Cold Wire Feed Submerged Arc Welding NSRP Subcontract Agreement Number: 2006-354 NSRP Sub Number: 012306

Final Report

Submitted to:

Advanced Technology Institute (ATI) 5300 International Boulevard North Charleston, SC 29418 Attention: Dolly Pelto

Submitted by:

100 CTC Drive Johnstown, PA 15904

Dec 12, 2006

Technical Point of Contact: Administrative: Mark F. Mruczek Darnella Parker Project Manager Contracts Manager Telephone: 814-269-2735 Telephone: 814-269-2602 Facsimile: 814-269-2799 Facsimile: 814-269-6530 E-mail: [email protected] E-mail: [email protected]

Category B Data - Government Purpose Rights Approved for public release; distribution is unlimited.

ACKNOWLEDGMENTS

Concurrent Technologies Corporation (CTC) conducted this research project under the National Shipbuilding Research Program (NSRP) Subcontract Agreement Number 2006-354. The author acknowledges the advice and guidance of Northrop Grumman Ship Systems (Lee Kvidahl) and Northrop Grumman Newport News Shipbuilding (Paul A. Hebert). The author also wishes to acknowledge the Lincoln Electric Company (Harry Sadler) for providing the submerged-arc welding flux 800H and LA-71 electrodes for use in this project.

Approved for public release; distribution is unlimited.

(This page intentionally left blank.)

EXECUTIVE SUMMARY

This document is the final report for the “Cold Wire Feed Submerged Arc Welding (CWF- SAW)” project conducted by Concurrent Technologies Corporation (CTC) as part of the National Shipbuilding Research Program (NSRP), SP–7 Panel project. CWF involves the addition of a separate base solid or tubular filler metal into the molten weld pool to provide additional metal deposition without the use welding current. This report provides practical insight into the CWF- SAW process and its effects on the weldability of HSLA-65 and HSLA-100 high strength low alloy (HSLA) steels and ABS grade EH-36 steel. The intent of this report is to summarize information derived from welding trials conducted at CTC on several representative ship steels. These welding trials were intended to produce weldments that exhibit mechanical properties necessary to meet the specified requirements for the single-wire SAW process while increasing deposition rates and decreasing the overall heat input into the weldment. This information will help the shipyards enhance their welding capabilities and improve weld productivity due to an increase in deposition rates. In this project, ten (10) weldments were fabricated at CTC using 2-inch thick HSLA-100, 1.5-inch thick HSLA-65 and 0.5-inch thick ABS EH-36 carbon steels. Welding of HSLA-65 steel was performed using Lincoln Electric LA-71(AWS EM14K) for both the electrode and cold wire using a Lincoln Electric MIL800-H flux. Welding of the HSLA-100 steel was performed using Lincoln Electric LA-100 wire for the electrode and ESAB Spoolarc 95, ER100S for the cold wire. The flux used to weld all HSLA-100 weldments was ESAB OK10.62. Welding of the EH-36 steel was performed using Lincoln Electric LA-50 (AWS EM13K) wire for the electrode and Hobart Brothers Quantum Arc 3 ER70S-3 for the cold wire. The flux used to weld all EH-36 weldments was ESAB OK10.62. Mechanical properties, including yield strength, ultimate tensile strength, elongation, and Charpy V-notch toughness, were evaluated to determine whether the requirements specified for conventional SAW could be achieved at higher deposition rates and higher calculated electrode heat inputs beyond the established limit of 85 kJ/in. In addition, cold-wire placement (leading VS. trailing) was investigated to determine weld bead penetration effects. Deposition rates were increased from 36% to 68% for the HSLA-65 weldments when compared to the benchmark weldment made with the single wire SAW process at approximately 85 kJ/in heat input. In addition, electrode heat input was increased from 88 kJ/in to 125 kJ/in with no deterioration in mechanical properties. In fact, both yield and tensile strengths increased slightly

along with a dramatic improvement in weld metal toughness. For the HSLA-100 steel, two (2) weldments were produced, one (1) benchmark weldment using the single wire process at approximately 85 kJ/in heat input and a second weldment made using the CWF-SAW process at 124 kJ/in heat input. Deposition rates were increased 39% for the root pass and 97.5% for the fill and cap passes. Yield strength and toughness properties of the CWF-SAW weldment meet the requirements for MIL-100S electrode in NAVSEA Technical Publication T9074-BC-GIB-010/0200; however, elongation requirements did not meet the requirements. Finally, three (3) weldments were fabricated using EH-36 steel. One (1) benchmark weldment was manufactured using the single wire process at approximately 85 kJ/in heat input, a second weldment made using the CWF-SAW process also at approximately 85 kJ/in heat input, and finally, a weldment made at 100 kJ/in heat input made using the CWF-SAW process. Deposition rates increased from 39% for the root pass and 81% for the fill and cap passes while both yield and tensile strengths decreased slightly but were above the American Bureau of Shipping requirements. However, toughness requirements were not met for the benchmark nor the CWF-SAW processes.

TABLE OF CONTENTS

Page #

1.0 INTRODUCTION & BACKGROUND...... 9 2.0 GOALS AND OBJECTIVES...... 10 3.0 TECHNICAL APPROACH ...... 10 3.1 Materials...... 10 3.1.1 Base Metals ...... 10 3.1.2 Welding Consumables...... 13 3.2 Weldment and Joint Details ...... 14 3.3 Welding Equipment...... 17 3.4 Deposition Rate Calculations ...... 19 3.5 Effective Heat Input Calculation...... 20 3.6 Task 1 HSLA-65 Cold Wire Feed...... 21 3.6.1 Process Development ...... 21 3.6.2 Weldment CTC-024 Single Wire Process ...... 23 3.6.3 Machining and Testing...... 24 3.6.4 Weldment CTC-026 89.8 kJ/inch Cold Wire Leading...... 26 3.6.5 Weldment CTC-027 89.8 kJ/inch Cold Wire Lagging...... 32 3.6.6 Weldment CTC-028 111.6 kJ/in Heat Input...... 37 3.6.7 Weldment CTC-029 111.6 kJ/in Heat Input...... 42 3.6.8 Weldment CTC-030 125.4 kJ/in Heat input...... 43 3.7 Task 2 HSLA-100 Cold Wire Feed...... 48 3.7.1 Weldment CTC-037 Single Wire Process ...... 48 3.7.2 Machining and Testing...... 50 3.7.3 Weldment CTC-038 124.2 kJ/in Heat input...... 53 3.8 Task 3 EH-36 Cold Wire Feed ...... 58 3.8.1 Weldment CTC-031 Single Wire Process ...... 58 3.8.2 Machining and Testing...... 59 3.8.3 Weldment CTC-033 100.5 kJ/in Heat input...... 61 4.0 BENEFITS AND SAVINGS...... 65

iii

4.1 Cold Wire Feed SAW of HSLA-65 Steel ...... 65 4.2 Cold Wire Feed SAW of HSLA-100 Steel ...... 66 4.3 Cold Wire Feed SAW of EH-36 Steel...... 68 5.0 SUMMARY AND CONCLUSIONS...... 69 5.1 Cold Wire Feed SAW of HSLA-65 Steel ...... 69 5.2 Cold Wire Feed SAW of HSLA-100 Steel ...... 69 5.3 Cold Wire Feed SAW of EH-36 Steel...... 69 6.0 RECOMMENDATIONS...... 70 6.1 Cold Wire Feed SAW of HSLA-65 Steel ...... 70 6.2 Cold Wire Feed SAW of HSLA-100 Steel ...... 70 6.3 Cold Wire Feed SAW of EH-36 Steel...... 72 7.0 REFERENCES ...... 73 8.0 APPENDICES...... 74 8.1 Appendix A: CTC Experience...... 74 8.2 CTC Capabilities – Welding Applications...... 74 8.2.1 Design for Manufacturing and Assembly ...... 74 8.2.2 Prototyping of Components and Assemblies ...... 74 8.2.3 Machine Shop...... 75 8.2.4 Weld Shop ...... 75 8.2.5 Coordinate Measuring Machine (CMM)...... 75

LIST OF TABLES Page #

Table 3-1. Specified Chemical Composition of HSLA-100 Comp 3 Steel...... 11 Table 3-2. Specified Chemical Composition of HSLA-65 Steel...... 12 Table 3-3. Specified Chemical Composition of ABS EH-36 Steel...... 12 Table 3-4. Welding Consumables for Each Base Metal...... 13 Table 3-5. Number of Weldments and Thickness for Each Base Metal ...... 14 Table 3-6. Weld Parameters for Single Wire Benchmark Weldment CTC-024 ...... 23 Table 3-7. Heat Input and Deposition Rates Benchmark Weldment CTC-024...... 23 Table 3-8. 70 Series Weld Metal Requirements...... 25 Table 3-9. Tensile and Yield Strength for Benchmark Weldment CTC-024 HSLA-65 Steel ...... 25 Table 3-10. CVN Properties for Benchmark Weldment CTC-024 HSLA-65 Steel ...... 25 Table 3-11. Weld Parameters for Weldment CTC-026 HSLA-65 Steel Cold Wire Feed SAW.... 26 Table 3-12. Heat Input and Deposition Rates for Weldment CTC-026 Cold Wire Feed SAW..... 26 Table 3-13. Deposition Rate Comparison and Percent Increase for CTC-024 VS. CTC-026 ...... 27 Table 3-14. Tensile and Yield Strength Comparison for Weldments CTC-024 and CTC-026 ..... 27 Table 3-15. CVN Properties Comparison for Weldments CTC-024 and CTC-026...... 28 Table 3-16. Tensile and Yield Strength Comparison Weldments CTC-026 and CTC-027 ...... 33 Table 3-17. CVN Comparison for Weldments CTC-026 and CTC-027...... 34 Table 3-18. Weld Parameters for Weldment CTC-028 Cold Wire Feed SAW ...... 38 Table 3-19. Heat Input and Deposition Rates for Weldment CTC-028 Cold Wire Feed SAW..... 38 Table 3-20. Deposition Rate Comparison and Percent Increase for CTC-024 VS. CTC-028 ...... 39 Table 3-21. Tensile and Yield Strength Comparison for Weldments CTC-024 and CTC-028 ..... 39 Table 3-22. CVN Comparison for Weldments CTC-024 and CTC-028...... 40 Table 3-23. Tensile and Yield Strength Comparison for Weldments CTC-028 and CTC-029 ..... 42 Table 3-24. CVN Comparison for Weldments CTC-028 and CTC-029...... 43 Table 3-25. Weld Parameters for Weldment CTC-030 Cold Wire Feed SAW ...... 44 Table 3-26. Heat Input and Deposition Rates for Weldment CTC-030 Cold Wire Feed SAW..... 44 Table 3-27. Deposition Rate Comparison and Percent Increase for CTC-024 VS. CTC-030 ...... 44 Table 3-28. Tensile and Yield Strength Comparison for Weldments CTC-024 and CTC-030 ..... 45

Table 3-29. CVN Comparison for Weldments CTC-024 and CTC-030...... 46 Table 3-31. Weld Parameters for Single Wire Benchmark Weldment CTC-037 ...... 49 Table 3-32. Heat Input and Deposition Rates for Weldment CTC-037 Cold Wire Feed SAW..... 49 Table 3-33. MIL-100S Weld Metal Requirements for Joining HSLA-100 ...... 50 Table 3-34. Tensile Properties for Benchmark Weldment CTC-037 HSLA-100 Steel...... 51 Table 3-35. CVN Properties for Benchmark Weldment CTC-037 HSLA-100 Steel ...... 52 Table 3-36. Weld Parameters for Weldment CTC-038 Cold Wire Feed SAW ...... 53 Table 3-37. Heat Input and Deposition Rates for Weldment CTC-038 Cold Wire Feed SAW..... 54 Table 3-38. Deposition Rate Comparison and Percent Increase for CTC-037 VS. CTC-038 ...... 54 Table 3-39. Tensile Property Comparison for Weldments CTC-037 and CTC-038...... 55 Table 3-40. CVN Properties Comparison for Weldments CTC-037 and CTC-038...... 56 Table 3-41. Weld Parameters for Single Wire Benchmark Weldment CTC-031 ...... 58 Table 3-42. Heat Input and Deposition Rates for Single Wire Benchmark Weldment CTC-031 . 58 Table 3-43. 3M or 3YM Weld Metal Requirements for Joining EH-36...... 59 Table 3-44. Tensile Properties of Benchmark Weldment CTC-031 ...... 60 Table 3-45. CVN Properties of Benchmark Weldment CTC-031 ...... 60 Table 3-46. Weld Parameters for Weldment CTC-033 Cold Wire Feed SAW ...... 61 Table 3-47. Heat Input and Deposition Rates for Weldment CTC-033 Cold Wire Feed SAW..... 62 Table 3-48. Deposition Rate Comparison and Percent Increase for CTC-031 VS. CTC-033 ...... 62 Table 3-49. Tensile and Yield Strength Comparison for Weldments CTC-031 and CTC-033 ..... 63 Table 3-50. CVN Comparison Weldments CTC-031 and CTC-033...... 63 Table 3-51. Weld Parameters for New HSLA-100 Cold Wire Feed SAW Weldment...... 71 Table 3-52. Heat Input and Deposition Rates for New HSLA-100 Cold Wire Feed Weldment... 71 Table 3-53. Deposition Rate Comparison and Percent Increase New HSLA-100 Weldment...... 71

LIST OF FIGURES Page #

Figure 3-1. Plate dimensions...... 15 Figure 3-2. Joint design B2V.3 for HSLA-65 welding process development...... 16 Figure 3-3. Joint design B2V.3 for HSLA-100 welding process development...... 16 Figure 3-4. Joint design B2V.1 for EH-36 welding process development...... 16 Figure 3-5. Lincoln Electric NA-5 wire feed controller...... 17 Figure 3-6. CK Worldwide WF-3 cold wire feed unit...... 18 Figure 3-7. CK Worldwide WF-3 cold wire feed unit side view...... 19 Figure 3-8. Cold-wire bracket...... 22 Figure 3-9. Cold-wire leading configuration...... 22 Figure 3-10. Mechanical test specimen locations for all HSLA-65 weldments...... 24 Figure 3-11. Transverse hardness detail of weldments CTC-024 and CTC-026...... 29 Figure 3-12. Transverse hardness profile of weldments CTC-024 VS. CTC-026...... 29 Figure 3-13. Temperature indicating liquid application example...... 30 Figure 3-14. Surface temperature comparison...... 31 Figure 3-15. Transverse section of CTC-026...... 32 Figure 3-16. Cold-wire lagging configuration...... 33 Figure 3-17. Transverse hardness profile of weldments CTC-024, CTC-026 and CTC-027...... 35 Figure 3-18. Penetration profile for weldments CTC-026 and CTC-027...... 36 Figure 3-19. Surface temperature comparison CTC-024, CTC-026 and CTC-027...... 37 Figure 3-20. Transverse section of CTC-027...... 37 Figure 3-21. Transverse hardness profile of weldments CTC-024 VS. CTC-028...... 41 Figure 3-22. Transverse section of CTC-028...... 41 Figure 3-23. Transverse hardness profile of weldments CTC-024 VS. CTC-030...... 47 Figure 3-24. Transverse section of CTC-030...... 47 Figure 3-25. Weld bead placement and number, weldment CTC-024...... 48 Figure 3-26. Weld bead placement and number, weldment CTC-030...... 48 Figure 3-27. Mechanical test specimen locations for all HSLA-100 weldments...... 51 Figure 3-28. Transverse section of CTC-037...... 53 Figure 3-29. Transverse hardness profile of weldments CTC-037 VS. CTC-038...... 57

vii

Figure 3-30. Transverse section of CTC-038...... 57 Figure 3-31. Mechanical test specimen locations for all EH-36 weldments...... 59 Figure 3-32. Transverse section of CTC-031...... 61 Figure 3-33. Transverse hardness profile of weldments CTC-031 VS. CTC-033...... 64 Figure 3-34. Transverse section of CTC-033...... 65 Figure 3-35. Cost saving comparison for single wire SAW vs. CWF-SAW of HSLA-65...... 66 Figure 3-36. Cost saving comparison for single wire SAW vs. CWF-SAW of HSLA-100...... 67 Figure 3-36. Cost Saving Comparison for New HSLA-100 CWF-SAW weldment...... 68

viii

1.0 INTRODUCTION & BACKGROUND

The current design concept for surface combatant ships include several large structures for each ship that are fabricated from thick-section, high-strength steels. Welding large, thick structures or plate requires large volumes of weld metal to be deposited using many beads and layers of weld metal. This requires thousands of production man-hours per ship and results in long production cycles. Therefore, there is great interest in the naval shipbuilding community to increase the productivity of fabrication joining process by increasing deposition rates without mechanical property deterioration and without the use of expensive additional equipment. The current means of increasing deposition rates is to increase the electrode feed rate, which consequently increases welding current and total heat input into the weldment. NAVSEA had approved single wire Submerged Arc Welding (SAW) of HSLA-100 up to 110 kJ/inch, and some shipyards had qualified procedures at that energy input. However, experience has shown that at such a high-energy input, mechanical properties, particularly toughness, are known to be inferior due to grain coarsening in the heat-affected zone (HAZ) and segregation in the weld metal along with the formation large columnar grains. In addition to the mechanical property deterioration, poor bead appearances are typically encountered as well; thus, shipyards typically limit SAW energy input to less than 85 kJ/inch. Therefore, increasing deposition rates by increasing heat input is at the expense of mechanical properties and not a viable solution. Attempts have been made to lower the heat input by such means as increasing welding speed; however, it has been shown that an increase in welding speed beyond a certain limit leads to defects such as undercut and a lack of sidewall fusion. Due to the inherent problems with the current means of increasing deposition rates, an alternative welding method was investigated that would increase deposition rates while maintaining or decreasing total heat input into the weldment. This method was the CWF-SAW process. Cold- wire additions have been shown to be feasible using both solid and flux-cored wires; however, the technique has not been applied to high-strength steels in the domestic shipbuilding industry. This project focused on cold-wire feed additions using a solid wire with a separate wire feed controller to allow cold-wire feed rates independent of the hot wire (electrode). There have been other applications where the cold wire is fed at the same speed as the electrode (Synergic Cold-Wire), [1] but the author felt that an independent cold-wire feed rate would allow for greater flexibility of the process for the operator and for weld procedure development as well.

2.0 GOALS AND OBJECTIVES

The objective of this project was to improve deposition rates and lower heat inputs by developing and optimize welding procedures using the CWF-SAW process to produce welds in steel types HSLA-65, HSLA-100 and EH-36 for large thick-section, high-strength steel structures. This process is not only expected to reduce welding labor by increasing deposition rates, but also help control distortion, help assure first-time quality, generate cost savings and reduce production schedules. In this project, weld joints were made at CTC using the CWF-SAW process in the above- mentioned structural steels. Mechanical properties, including weld-metal yield strength, ultimate tensile strength, elongation and Charpy V-notch toughness, were evaluated to determine whether the requirements specified for conventional SAW could be achieved at higher deposition rates and higher heat inputs. In addition, cold-wire placement (leading VS. trailing) was also investigated to determine the effect on weld bead penetration. Hardness readings were performed to help determine the change in overall heat input into the weldment to help prove the theory of an “effective heat input” when welding with the CWF-SAW process.

3.0 TECHNICAL APPROACH

3.1 Materials

3.1.1 Base Metals

All base metal used for the procedure development for the CWF-SAW processes was 2-inch thick HSLA-100 Comp 3, 1.25-inch thick HSLA-65, and 0.5-inch thick EH-36 steels. HSLA-100 is a low-carbon, copper strengthened steel that was introduced as a replacement for HY-100 in order to reduce fabrication costs by reduced preheating while using the same welding consumables and process used in welding HY-100. One of the benefits of the low-carbon, copper strengthened HSLA-100 steel is its ability to produce a weld heat-affected zone (HAZ) with excellent strength and toughness without the need for preheat. Some regions may actually soften due to over-aging and the dissolution of copper and grain coarsening caused by the heat of welding [2]. The specified composition for two-inch HSLA-100 per T9074-BD-GIB-010/030 Appendix A (24645) is shown in Table 3-1.

Table 3-1. Specified Chemical Composition of HSLA-100 Comp 3 Steel

Element Weight % Carbon (C) 0.06 Manganese (Mn) 0.75–1.15 Phosphorus (P) 0.020 Sulfur (S) 0.004 Silicon (Si) 0.40 Nickel (Ni) 3.35–3.65 Chromium (Cr) 0.45–0.75 Molybdenum (Mo) 0.55–0.65 Copper (Cu) 1.15–1.75 Niobium (Nb) 0.02–0.06 Aluminum (Al) 0.015 Vanadium (V) 0.03 Note: Single values are maxima

ASTM A 945, Grade 65 was established as the standard specification for HSLA-65 steel plate with low carbon and restricted sulfur for improved weldability, formability, and toughness [3]. This steel is essentially an enhanced carbon-manganese steel, with small alloying additions. HSLA- 65 was developed as a replacement for high-strength steel (HSS) steel plate. The replacement resulted a structural weight reduction and when compared to HSS steel due to its higher yield strength (65 ksi. VS. 51 ksi). The specified composition for HSLA-65 per ASTM A945 Grade 65 is shown in Table 3-2. ABS EH-36 is a HSS steel used in shipbuilding with good weldability and toughness properties. The specified composition for EH-36 per ABS specification is shown in Table 3-3.

Table 3-2. Specified Chemical Composition of HSLA-65 Steel

Element Weight % Carbon (C) 0.10 Manganese (Mn) 1.10–1.65 Phosphorus (P) 0.025 Sulfur (S) 0.010 Silicon (Si) 0.10–0.50 Nickel (Ni) 0.4 Chromium (Cr) 0.20 Molybdenum (Mo) 0.08 Copper (Cu) 0.35 Niobium (Nb) 0.05 Aluminum (Al) 0.08 Vanadium (V) 0.10 Note: Single values are maxima

Table 3-3. Specified Chemical Composition of ABS EH-36 Steel

Element Weight % Carbon (C) 0.18 Manganese (Mn) .90–1.60 Phosphorus (P) 0.035 Sulfur (S) 0.035 Silicon (Si) 0.10–0.50 Nickel (Ni) 0.4 Chromium (Cr) 0.20 Molybdenum (Mo) 0.08 Copper (Cu) 0.35 Niobium (Ti) 0.02–0.05 Vanadiun (V) 0.05–0.10 Aluminum (Al) 0.015 Note: Single values are maxima

3.1.2 Welding Consumables

SAW is a well-established method for welding most grades of carbon and low alloy steels found in today’s shipbuilding industry. Offering high productivity, along with good weld quality, excellent weld appearance and environmental advantages (e.g., no fume emissions), SAW is an attractive method, especially when welding thicker materials such as those found in shipbuilding. Welding of HSLA-65 steel was performed using Lincoln Electric LA-71(AWS EM14K) for both the electrode and cold wire using a Lincoln Electric MIL800-H flux. Welding of the HSLA- 100 steel was performed using Lincoln Electric LA-100 wire for the electrode and ESAB Spoolarc 95, ER100S for the cold wire, both are produced to the requirements of MIL-100S-1 per MIL-E- 23765/2D. The flux used to weld all HSLA-100 weldments was ESAB OK10.62. Welding of the EH-36 steel was performed using Lincoln Electric LA-50 (AWS EM13K) wire for the electrode and Hobart Brothers Quantum Arc 3 ER70S-3 for the cold wire. The flux used to weld all EH-36 weldments was ESAB OK10.62. Base metal and electrode combinations are shown in Tables 3-4.

Table 3-4. Welding Consumables for Each Base Metal

Electrode Electrode Cold wire Cold Wire Steel Class and Diameter, Class and Diameter, Flux Brand inch Brand inch AWS AWS EM14K Lincoln HSLA-65 EM14K 0.125 0.0625 LA-71 MIL800-H LA-71 MIL-100S-1 SpoolArc 95/ ESAB HSLA-100 0.125 0.0625 LA-100 MIL-100S-1 OK 10.62 AWS ESAB EH-36 EM13K 0.125 ER70S-3 0.0625 OK 10.62 L-50

ESAB OK10.62 flux is a bonded, fully basic flux used primarily for multipass butt-welding carbon and low alloy steel plate and is manufactured by ESAB Welding and Cutting. OK10.62 flux is suited for AC and DC, single- and multi-wire systems at currents up to 1000 A. Lincoln Electric MIL800-H flux is an agglomerated, neutral flux used for multipass butt-welding carbon and low alloy steel plate with single- and multi-wire systems. Agglomerated fluxes are manufactured by taking a mixture of prescribed ingredients and adding a ceramic or a mineral material as a cementing or binding agent. To accomplish

cementation, the total mixture is then heated to about 600 °C (1100 °F). After cementation has been completed, the mixture is cooled and cakes of flux are formed. These cakes are then crushed and screened to produce the specified range of flux mesh sizes. Bonded fluxes, like agglomerated fluxes, also use a binding agent to hold all the ingredients together until a solid cake of flux is formed. The bonding materials used are aqueous silicates of sodium and potassium, which differ from the ceramic or mineral materials used in the manufacture of agglomerated fluxes. The dry ingredients are mixed with the liquid silicate and then dried by baking to approximately 300 °C (600 °F). The dried, bonded cake is then crushed and screened just like the agglomerated flux. It should be noted that bonded fluxes sometimes have a greater tendency to pick up moisture than agglomerated fluxes; therefore, bonded flux may require better protection than agglomerated and fused fluxes during storage and handling [4].

3.2 Weldment and Joint Details

For each base material type described above, CTC produced the number of weldments shown in Table 3-5 below. These quantities included one benchmark welding for each base metal welded at approximately 85 kJ/in total heat input.

Table 3-5. Number of Weldments and Thickness for Each Base Metal

Thickness, Steel No. of Joints inch HSLA-65 1.25 6 HSLA-100 2 2 EH-36 0.5 2 10 total

Each weldment was 16 inches wide (minimum) and 28 inches long (minimum) as shown in Figure 3-1 to accommodate the number of test specimens required. All HSLA-65 and HSLA-100 weldments had bevel angles of 50-degrees included and utilize the double-V joint design shown in Figures 3-2 and 3-3. This joint design is in accordance with MIL-STD-22D, page 8 and carries a joint designation of B2V.3. Joint design for the EH-36 weldments was the single-V joint design

shown in Figure 3-4. This joint design is in accordance with MIL-STD-22D, page 7 and carries a joint designation of B2V.1.

28 in 16 in

Figure 3-1. Plate dimensions.

Figure 3-2. Joint design B2V.3 for HSLA-65 welding process development.

Figure 3-3. Joint design B2V.3 for HSLA-100 welding process development.

Figure 3-4. Joint design B2V.1 for EH-36 welding process development.

3.3 Welding Equipment

All SAW was performed using a Lincoln Electric Idealarc DC-1500 power source with a Lincoln Electric NA-5 wire feed controller shown in Figure 3-5. The cold wire was fed using a CK Worldwide WF-3 Cold Wire Feed unit shown in Figure 3-6. The cold wire unit was mounted to the welding table for this project because the plates were relatively small. However, it could be mounted in any configuration to suit the fabrication needs.

Figure 3-5. Lincoln Electric NA-5 wire feed controller.

Figure 3-6. CK Worldwide WF-3 cold wire feed unit.

It should be noted that this cold wire feed unit was design for use with the gas tungsten arc welding process (GTAW) and not the SAW process. Therefore, the unit is only capable of a maximum wire diameter of 0.0635-inches. In addition, this unit cannot accommodate spools larger than 40 pounds. Figure 3-7 shows a side view of the cold wire feed unit with a 40-pound spool loaded into it.

Figure 3-7. CK Worldwide WF-3 cold wire feed unit side view.

3.4 Deposition Rate Calculations

Deposition rates for arc welding processes are dependent on the electrode diameters, electrode feed speed, and process efficiency (E). This is illustrated in Equation 3-1, which shows the deposition rate (Drate) calculation for a single-electrode welding process. This calculation was used for all single wire SAW benchmark weldments in this project. Where wiredia is the diameter of the electrode, wirespeed is the electrode feed rate, is the density of the weld metal, and E is the process efficiency.

2 ≈ wiredia’ D rate π ⋅∆ ÷ ⋅wirespeed⋅ρ ⋅E (3-1) « 2 ◊

Because the CWF-SAW, process adds a second cold wire to the process a second term must be added to the equation. In Equation 3-2, the second wire has been added to Equation 3-1 and this calculation was then used to calculate the deposition rates for all CWF-SAW weldments in this

project. Where E_wiredia is the diameter of the electrode, E_wirespeed is the electrode feed rate,

CW_wiredia is the diameter of the cold wire, CW_wirespeed is the cold wire feed rate, is the density of the weld metal, and E is the process efficiency.

» 2 ÿ » 2 ÿ … ≈ E_wiredia’ Ÿ … ≈ CW_wiredia’ Ÿ DepRateDep π ⋅∆ ÷ ⋅E_wirespeed⋅ρ ⋅E + π ⋅∆ ÷ ⋅CW_wirespeed⋅ρ ⋅E « 2 ◊ ⁄ « 2 ◊ ⁄ ( 3-2)

Process efficiency (E) shown in both equations describes how many pounds of weld metal can be expected from a given weight of the electrode or welding wire purchased. As an example, 100 pounds of a flux-cored electrode with an efficiency of 85% will produce approximately 85 pounds of weld metal, whereas 100 pounds of shielded-metal-arc electrode with an efficiency of 65% will produce approximately 65 pounds of weld metal [3]. A loss due to slag, spatter, and fume generation and, in the case of semiautomatic processes, the ends of the electrode cut before each weld, reduces process efficiencies [5]. SAW has a process efficiency of approximately 99%, because the only loss during SAW welding is the short piece the operator must clip off the end of the wire to remove the fused flux that forms at the termination of each weld. This is done to assure a good start on the succeeding weld.

3.5 Effective Heat Input Calculation

Earlier studies have indicated that the addition of a cold-wire produces a heat input that is less than the nominal heat input of a conventional arc welding process because the wire absorbs heat from the weld pool during insertion [1]. The term “effective heat input” was used to describe this reduced heat input and was based on the relative diameters of the electrode and cold wire to produce a heat input reduction factor. This was possible because both the electrode and cold wire were fed at the same rate and were the same diameter. This factor was then multiplied by the heat input of the electrode and the relative heat input was determined. Because the cold-wire process in this project used a cold-wire diameter that was smaller than the electrode and wire feed rates for each were different, the relative diameter approach was not applicable. The author used a reduction factor that

was based on previous research done at CTC and was based on electrode volume per unit time [7]. This would accommodate the feed rate difference between the electrode and the cold wire. Equations 3-3 and 3-4 show how the electrode and cold-wire volume per unit time were calculated (evol and cwvol) and Equation 3-5 shows the reduction factor calculation (Cf_mod) that was used to calculate the effective heat input for all cold wire feed weldments [7].

2 e vol d e ⋅e speed (3-3)

2 cw vol d cw ⋅cw speed (3-4)

e vol C f_mod (e vol+ cw vol) (3-5)

In the above calculations, de and dcw are the electrode and cold-wire diameters respectively, and espeed and cwspeed are the electrode and cold-wire feed rates. This reduction in heat input was not verified during actual welding trials by the use of thermocouples, however, this report will show that the hypothesis of an effective heat input is plausible through the use of hardness readings, weldment surface temperature readings, and CVN data generated for various benchmark and cold- wire feed weldments.

3.6 Task 1 HSLA-65 Cold Wire Feed

3.6.1 Process Development

A simple bracket, shown in Figure 3-8, was designed to hold the cold wire feeder in place and allow for angular adjustments. The bracket was fabricated from an aluminum alloy and mounted onto the existing nozzle assembly of the SAW machine. An insulator was inserted between the bracket and nozzle to ensure that no current was being conducted through the bracket to the cold wire.

Bracket and Pivot Arm

Figure 3-8. Cold-wire bracket.

After a few bead-on-plate trials, an angle and distance between the electrode and cold wire was selected for the actual welding trials. Figure 3-9 shows the configuration of the cold wire leading the electrode.

Figure 3-9. Cold-wire leading configuration.

3.6.2 Weldment CTC-024 Single Wire Process

In this task, six (6) weldments were fabricated using 1.25-inch HSLA-65 steel. The first weldment, CTC-024, was fabricated using the single wire SAW process with a 0.125-inch diameter electrode. All welding parameters are shown in Table 3-6. This weldment was used as the benchmark for the last five weldments fabricated using the cold wire process.

Table 3-6. Weld Parameters for Single Wire Benchmark Weldment CTC-024

Wire Size (in) Avg. Wire Speed (ipm) Avg. Avg. Travel Pass Current Cold Amps Volts Speed Cold Electrode Wire (ipm) Electrode Wire Root 0.125 0.0625 DCEP 412 30.2 12 53 N/A Fill and Cap 0.125 0.0625 DCEP 470 31.4 10 62 N/A

Table 3-7 shows the calculated average heat input for each pass and the deposition rates using equation 3-1 for weldment CTC-024 with the parameters shown in Table 3-7. It should be noted that the heat input calculation does not include the arc efficiency factor for the SAW process. In arc welding, heat losses by convection and radiation should be taken into account by the efficiency factor when calculating heat input. This factor is used to determine the actual heat transferred to the weldment. Most fabrication codes do not use this factor so it was decided by the author not to incorporate it into this project for heat input calculations.

Table 3-7. Heat Input and Deposition Rates Benchmark Weldment CTC-024

Calculated Weld Avg. Heat Input Reduction Effective Heat Deposition Pass Identification Electrode Factor Input (kJ/in) Rate (kJ/in) (lb/hr) Root 62.2 N/A N/A 10.9 Passes CTC-024 Fill and Cap 88.5 N/A N/A 12.8 Passes

3.6.3 Machining and Testing

Two (2) all weld metal 0.5-inch diameter tension, five (5) Charpy V-notch, two (3) transverse side bends and two (2) metallographic specimen were removed from each of the HSLA- 65 weldments. In Figure 3-10 the detailed locations for all specimens removed from each HSLA-65 weldment are shown from side 1 of the weldment. All Charpy V-notch specimens were removed at a depth of 0.062-inchs below the weldment surface per the requirements of the electrode. The CVN specimens had the notch located at the weld centerline. All tensile specimens were removed with their centers 0.375-inch below the weldment surface per the requirements of the 0200 technical publication.

Figure 3-10. Mechanical test specimen locations for all HSLA-65 weldments.

During welding, liquid Penetrant Testing (PT) was performed after backgouging the root pass and on the final cap passes. After welding was completed, mechanical tests were performed on weldment CTC-024 and used as the benchmark for the following five weldments. Table 3-8 shows the requirements for 70 series electrodes, which have been approved for welding HSLA-65 steel. The results of the mechanical testing are shown in Table 3-9 and 3-10.

Table 3-8. 70 Series Weld Metal Requirements

Test Type Property Requirement Tensile Properties Yield Strength 70,000 to 95,000 (min. & max. in psi) Elongation in 2- 22.0 inches min. (%) Charpy V-notch Impact Energy 30 ft-lb at –20 °F (minimum average)

Table 3-9. Tensile and Yield Strength for Benchmark Weldment CTC-024 HSLA-65 Steel

Specimen Tensile Elongation Reduction Specimen Yield Diameter Strength Increase of Area Identification Strength (inches) (ksi) (%) (%) TS1-024 0.4986 90.9 80.7 24 71 TS2-024 0.5001 90.2 80.2 24 70 Requirement 0.5000 ± 0.0100 - 70–95 22 -

Table 3-10. CVN Properties for Benchmark Weldment CTC-024 HSLA-65 Steel

Test Absorbed Lateral Fracture Specimen Temperature Energy Expansion Appearance Identification (°F) (ft-lbs) (mils) (% shear) CTC-024-1 -20 43.0 39 46 CTC-024-2 -20 57.0 42 50 CTC-024-3 -20 43.0 35 61 CTC-024-4 -20 104.0 67 77 CTC-024-5 -20 46.0 34 42 Average 58.6 43.4 55.2 St. Dev. 8.1 3.5 7.8 Requirement -20 30 - -

In addition to the testing shown in Tables 3-9 and 3-10, three full section side bends and transverse hardness tests were also performed. The bend specimens were bent to a 2T radius (T = specimen thickness). All bend specimens were acceptable with no cracking noted. As can be seen in Table 3-10 all specimens met or exceeded the toughness requirement shown in Table 3-8.

3.6.4 Weldment CTC-026 89.8 kJ/inch Cold Wire Leading

The first CWF-SAW weldment to be fabricated was CTC-026. For this weldment, all welding parameters remained the same as CTC-024 with the only difference being the addition of a 0.0625-inch diameter cold wire, which was leading the electrode as shown in Figure 2-15. Welding parameters for CTC-026 are shown in Table 3-11 and the calculated average heat input, effective heat input, and deposition rates using equation 3-2 are shown in Table 3-12.

Table 3-11. Weld Parameters for Weldment CTC-026 HSLA-65 Steel Cold Wire Feed SAW

Wire Size (in) Avg. Wire Speed (ipm) Avg. Avg. Travel Weld Current Identification Cold Amps Volts Speed Cold CTC-026 Electrode Wire (ipm) Electrode Wire Root Passes 0.125 0.0625 DCEP 410 30 12 53 90 Fill and Cap 0.125 0.0625 DCEP 475 31.5 10 62 90 Passes

Table 3-12. Heat Input and Deposition Rates for Weldment CTC-026 Cold Wire Feed SAW

Calculated Weld Avg. Heat Input Reduction Effective Heat Deposition Pass Identification Electrode Factor Input (kJ/in) Rate (kJ/in) (lb/hr) Root 61.5 0.702 43.2 15.6 Passes CTC-026 Fill and Cap 89.8 0.734 65.9 17.4 Passes

Although the welding parameters remained the same as with the single wire weldment CTC- 024, note the decrease in heat input from the calculated 89.7 kJ/in to the effective heat input of 65 kJ/in for the fill and cap passes. As mentioned previously in Section 3.5, the reduction factor was used to determine the effective heat input for this process by multiplying the average heat input by the reduction factor to achieve the effective heat input. Deposition rates were then compared to the single wire weldment CTC-024 and the percent increase in deposition rate was calculated for the cold wire feed process with the results shown in Table 3-13. As can be seen in Table 3-13, the

addition of a cold wire to the single wire SAW process produced an increase in the deposition rate of the root pass by 43.1 % and a 36% increase in the deposition rate for the fill and cap passes. This increase in deposition rate was achieved by using the same welding parameters as the single wire weldment CTC-024 and simply adding a cold wire to the process.

Table 3-13. Deposition Rate Comparison and Percent Increase for CTC-024 VS. CTC-026

Deposition Deposition Percent Rate Cold- Weld Rate Single Increase in Pass Wire Identification Electrode Deposition Process (lb/hr) Rate (lb/hr) Root Pass 10.9 15.6 43.1% CTC-026 Fill Passes 12.8 17.4 35.9%

After welding was completed, mechanical and hardness tests were performed on weldment CTC-026 and compared to the benchmark weldment CTC-024. The results of the mechanical testing are shown in Table 3-14 and 3-15.

Table 3-14. Tensile and Yield Strength Comparison for Weldments CTC-024 and CTC-026

Specimen Tensile Yield Elongation Reduction Specimen Diameter Strength Strength Increase of Area Identification (in.) (ksi) (ksi) (%) (%) TS1-024 0.4986 90.9 80.7 24 71 TS2-024 0.5001 90.2 80.2 24 70

TS1-026 0.4995 92.8 83.3 24 73 TS2-026 0.4994 93.4 84.5 24 70 Requirement 0.5000 ± 0.0100 - 70–95 22 -

As can be seen in Table 3-14, specimens met the yield strength requirement of 70 to 95 ksi shown in Table 3-8. There was a slight increase in both tensile and yield strengths for the cold wire feed weldment when compared to the single wire weldment and both elongation and reduction of area remained the same. Intuitively this makes sense since the effective heat input of weldment CTC-026 was lower than the single wire weldment of CTC-024, which increased the cooling rate and thus the yield and tensile strength of the weld metal. Table 3-15 shows the comparison of the

CVN impact test results for the cold wire feed SAW weldment CTC-026 to the single wire weldment CTC-024.

Table 3-15. CVN Properties Comparison for Weldments CTC-024 and CTC-026

CTC-026-1 -20 115.6 76 88 CTC-026-2 -20 80.0 55 84 CTC-026-3 -20 44.0 32 45 CTC-026-4 -20 53.0 41 62 CTC-026-5 -20 65.0 45 67 Average 71.5 49.8 69.2 St. Dev. 28.1 16.8 17.4 Requirement -20 30 - -

NAVSEA has established a requirement for weld metal toughness in HSLA-65 of 30 ft-lbs at –20 °F. Table 3-14 clearly shows that all specimens tested meet the minimum requirement of 30 ft- lb at –20 °F. Specifically, note the increase in the average reading for the cold wire weldment CTC- 026. This was achieved using the same welding parameters as the single wire welding CTC-024, with the only difference being the addition of the cold wire. This increase is to be expected and reasonable if we apply the hypothesis presented earlier that the cold wire reduces the actual heat input into the weldment (effective heat input of 65.9 kJ/inch), which generally increases the weld cooling rate and thus weld metal toughness. These data are a good indicator that the effective heat input hypothesis is reasonable. Hardness readings were performed on transverse sections of weldments CTC-024 and CTC- 026 in the base metal, HAZ and weld metal using a Vickers micro-hardness tester with a 1-kg load and 1-mm spacing between readings, as shown in Figure 3-11. In addition, all weldments fabricated

in this project had the hardness measurements performed in the same manner. A graph of the hardness profiles comparing the two weldments is shown in Figure 3-12.

1.25in.

Figure 3-11. Transverse hardness detail of weldments CTC-024 and CTC-026.

CTC-024 Side 2 CTC-026 Side 2

250 240 s

s 230 e n

d 220 r

a 210 H

r 200 e

k 190 c i

V 180 170 160 150 Base Metal HAZ Weld Metal HAZ Base Metal

Figure 3-12. Transverse hardness profile of weldments CTC-024 VS. CTC-026.

Figure 3-12 shows a distinct and significant difference in hardness readings for these two weldments. The cold wire feed welding has a higher harness reading for both the HAZ and the weld metal. This is a good indicator of the effective heat input hypothesis that was presented in section 3.5. As shown in Table 3-7, the heat input for CTC-024 is 88.5 kJ/in and the effective heat input for weldment CTC-026 is 65.9 kJ/in. The lower heat input for CTC-026 would produce a cooling rate that was higher than that of CTC-024. Typically, the higher the cooling rate the higher the hardness readings, which is what is observed in Figure 3-12. During the welding of the final cap pass for both weldments (CTC-024 and CTC-026), heat paints were used to illustrate and compare the actual heat flowing into the base metal. Each paint melts at a specific temperature shown (1700 F to 206 F). These indicating heat paints were purchased from Tempil (Tempillag G temperature indicating liquid) and were applied to the surface using a small paintbrush applicator extending 2-inches from the edge of the joint preparation. After welding was completed, and the surface was cool enough to touch, the length of melting was measured and recorded for each color of paint. Figure 3-13 shows the temperature indicating liquid after application to the weldment surface.

Figure 3-13. Temperature indicating liquid application example.

Comparisons were made between the two weldments to support the concept of an “effective heat input”, or that the addition of a cold-wire produces a heat input that is less than the nominal heat input of a conventional arc welding process because the wire absorbs heat from the weld pool during insertion. Figure 3-14 shows the comparison between the single wire weldment CTC-024 and the cold wire weldment CTC-026.

024 Pass 4 026 Pass 3 1700 1550

F 1400

g 1250 e D 1100 e r

u 950 t a

r 800 e

p 650 m

e 500 T 350 200 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 Distance Melted (in)

Figure 3-14. Surface temperature comparison.

As can be seen from Figure 3-14, there is a significant temperature drop for the cold wire weldment CTC-026 when compared to the single wire weldment CTC-024. This would indicate that the addition of a cold wire reduces the heat input into the weldment and supports the idea of an “effective heat input”. This evidence along with the increase in hardness values that were shown for weldment CTC-026, gives compelling evidence to the theory of the effective heat input for the CWF-SAW process. Figure 3-15 shows a transverse macro sample taken from cold wire feed weldment CTC-026. As can be seen from the figure, there are no indications in the weld metal, (e.g, porosity, cracking) and completed penetration was accomplished.

1.25 in.

Figure 3-15. Transverse section of CTC-026.

3.6.5 Weldment CTC-027 89.8 kJ/inch Cold Wire Lagging

The third weldment fabricated in this series was CTC-027. This weldment was welded with the same parameters as CTC-026, which are shown in Table 3-10 and produced heat inputs and deposition rates as shown in Table 3-11. However, the cold wire for this weldment was switched from leading the electrode as shown in Figure 3-10 to lagging the electrode with reference to travel direction as shown in Figure 3-16. This was done to see if there were any effects on mechanical properties and more specifically on weld bead penetration.

Figure 3-16. Cold-wire lagging configuration.

As can be seen in Tables 3-16 and 3-17, there was essentially no change in mechanical properties when compared to the cold wire feed weldment CTC-026. Both yield and tensile strengths were similar and were slightly better than the single wire weldment CTC-024, while toughness properties seemed to fare better for CTC-027 with the cold wire lagging; but it was not a significant improvement over CTC-26. Yield strength met the 70 to 95 ksi requirement and toughness requirements of 30 ft-lbs at –20 °F were also met.

Table 3-16. Tensile and Yield Strength Comparison Weldments CTC-026 and CTC-027

Specimen Tensile Yield Elongation Reduction Specimen Diameter Strength Strength Increase of Area Identification (in.) (ksi) (ksi) (%) (%) TS1-026 0.4995 92.8 83.3 24 73 TS2-026 0.4994 93.4 84.5 24 70

TS1-027 0.4989 93.0 83.8 24 70 TS2-027 0.4997 92.8 83.5 25 72 Requirement 0.5000 ± 0.0100 - 70–95 22 -

Table 3-17. CVN Comparison for Weldments CTC-026 and CTC-027

Test Absorbed Lateral Fracture Specimen Temperature Energy Expansion Appearance Identification (°F) (ft-lbs) (mils) (% shear) CTC-026-1 -20 115.6 76 88 CTC-026-2 -20 80.0 55 84 CTC-026-3 -20 44.0 32 45 CTC-026-4 -20 53.0 41 62 CTC-026-5 -20 65.0 45 67 Average 71.5 49.8 69.2 St. Dev. 28.1 16.8 17.4

CTC-027-1 -20 82.5 56 76 CTC-027-2 -20 76.2 54 74 CTC-027-3 -20 73.0 52 73 CTC-027-4 -20 76.3 54 74 CTC-027-5 -20 73.6 52 73 Average 76.3 53.6 74.0 St. Dev. 3.8 1.7 1.2 Requirement -20 30 - -

Transverse hardness readings were performed on weldment CTC-027 and were then compared to the single wire weldment CTC-024 and the cold wire weldment CTC-026 (cold wire leading). As can be seen in Figure 3-17, the hardness readings increased when compared to the single wire weldment CTC-024, and were roughly the same for the weld metal when compared to weldment CTC-026. However, there is a slight decrease in the hardness values for the HAZ of weldment CTC-027 when compared to CTC-026. This difference would indicate a slower cooling rate than was seen in CTC-026 resulting in a softer HAZ. This also suggests that there was a higher amount of heat being generated into the HAZ than was seen in the CTC-026 weldment.

CTC-024 Side 2 CTC-026 Side 2 CTC-027 Side 2 250 240 s

s 230 e n

d 220 r a 210 H

r 200 e

k 190 c i

V 180 170 160 150 Base Metal HAZ Weld Metal HAZ Base Metal

Figure 3-17. Transverse hardness profile of weldments CTC-024, CTC-026 and CTC-027.

One significant change that did occur when the cold wire orientation changed from leading to lagging was the amount of penetration of the root pass into the base metal. As can be seen in Figure 3-18, CTC-026 shows almost complete root penetration, whereas CTC-027 shows a significant decrease in penetration (circled in red) and was approximately 0.078 inches (2mm) in depth. This is significant for manufacturing of thinner plate where melt-through would be a concern or for any process that would deal with hardfacing or cladding. The hardfacing or cladding operation requires minimum penetration into the base metal to minimize the dilution rate of the weld metal. In addition to the change in penetration, there was also a slight increase in weld bead area and HAZ size. The change in HAZ size validates the lower hardness readings for the HAZ in Figure 3-17.

Change in Penetration CTC-026, Cold CTC-027, Cold Wire Leading Wire Lagging

Figure 3-18. Penetration profile for weldments CTC-026 and CTC-027.

As with weldments CTC-024 and CTC-026, during the welding of the final cap pass for CTC-027, heat paints were used to see the actual heat flowing into the base metal. Figure 3-19 shows the comparison between the single wire weldment CTC-024 and the cold wire weldments CTC-026, and CTC-027. As can be seen, the temperature difference for both cold wire weldments was significantly less when compared to the single wire weldment CTC-024 and again reinforces the theory of the effective heat input. In addition, weldment CTC-027, with the cold wire lagging, produced a slightly higher heat input into the weldment than CTC-026 with the cold wire leading. Thus the weld penetration would be greater with the cold wire lagging, as shown in Figure 3-18; however, it was not observed in a transverse section of weldment CTC-027 in Figure 3-20.

024 Pass 4 026 Pass 3 027 Pass 7

1800

) 1600 F

g 1400 e D

( 1200

r 1000 u t 800 a r

e 600 p

m 400 e

T 200 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 Distance Melted (in)

Figure 3-19. Surface temperature comparison CTC-024, CTC-026 and CTC-027.

1.25 in.

Figure 3-20. Transverse section of CTC-027.

3.6.6 Weldment CTC-028 111.6 kJ/in Heat Input

The fourth weldment in this task was CTC-028. This weldment was welded with the cold wire leading the electrode, and the calculated heat input for the electrode increased from 88 kJ/in to 111.6 kJ/in for the fill and cap passes. This heat input is over the limit that shipyards typically use

due to the deterioration in mechanical properties and weld bead appearance. Welding parameters for CTC-028 are shown in Table 3-18 and the calculated average heat input, effective heat input, and deposition rates using equation 3-2 are shown in Table 3-19.

Table 3-18. Weld Parameters for Weldment CTC-028 Cold Wire Feed SAW

Wire Size (in) Avg. Wire Speed (ipm) Avg. Avg. Travel Weld Current Identification Cold Amps Volts Speed Cold CTC-028 Electrode Wire (ipm) Electrode Wire Root Passes 0.125 0.0625 DCEP 410 30.4 10 53 90 Fill and Cap 0.125 0.0625 DCEP 515 32.5 9 71 110 Passes

Table 3-19. Heat Input and Deposition Rates for Weldment CTC-028 Cold Wire Feed SAW

Calculated Weld Avg. Heat Input Reduction Effective Heat Deposition Pass Identification Electrode Factor Input (kJ/in) Rate (kJ/in) (lb/hr) Root 74.8 0.702 52.5 15.6 Passes CTC-028 Fill and Cap 111.6 0.721 79.6 20.3 Passes

Deposition rates were compared to the single wire weldment CTC-024 and the percent increase in deposition rate was calculated for the cold wire feed process with the results shown in Table 3-20. As can be seen in Table 3-20, the addition of a cold wire to the single wire SAW process and the increase in heat input produced an increase in the deposition rate of the root pass by 42.2 % and a 58.6% increase in the deposition rate for the fill and cap passes. Incidentally, these parameters also produced a 35.9% increase in the deposition rate for the fill and cap passes when compared to weldment CTC-026.

Table 3-20. Deposition Rate Comparison and Percent Increase for CTC-024 VS. CTC-028

Deposition Deposition Percent Rate Cold- Weld Rate Single Increase in Pass Wire Identification Electrode Deposition Process (lb/hr) Rate (lb/hr) Root Pass 10.9 15.5 42.2% CTC-028 Fill Passes 12.8 20.3 58.6%

In Table 3-19, note the decrease in heat input from the calculated 111.6 kJ/in to the effective heat input of 79.6 kJ/in for the fill and cap passes. This is below the 88 kJ/in that was originally used for the single wire weldment CTC-024. As expected, this weldment also produced better mechanical properties than the single wire weldment CTC-024 as shown in Table 3-21 for tensile properties and Table 3-22 for toughness properties.

Table 3-21. Tensile and Yield Strength Comparison for Weldments CTC-024 and CTC-028

Specimen Tensile Yield Elongation Reduction Specimen Diameter Strength Strength Increase of Area Identification (in.) (ksi) (ksi) (%) (%)

TS1-024 0.4986 90.9 80.7 24 71 TS2-024 0.5001 90.2 80.2 24 70

TS1-028 0.4999 92.1 82.9 23 66 TS2-028 0.5000 91.5 82.6 22 68 Requirement 0.5000 ± 0.0100 - 70–95 22 -

Table 3-22. CVN Comparison for Weldments CTC-024 and CTC-028

CTC-028-1 -20 55.0 39 59 CTC-028-2 -20 94.1 61 81 CTC-028-3 -20 30.1 21 43 CTC-028-4 -20 110.2 72 87 CTC-028-5 -20 55.2 40 59 Average 68.9 46.6 65.8 St. Dev. 32.5 20.1 18.0 Requirement -20 30 - -

As shown in Table 3-21 even though tensile and yield strengths increased when compared to the single wire weldment, elongation and the reduction of area decreased slightly but were well within acceptable values of. Average toughness values again were better than the single wire weldment and all specimens were above the requirement. It should be noted that one specimen (CTC-028-3) was marginally over the minimum but is not a concern since the other four specimens exceeded the requirements. Hardness readings were performed on a transverse section of weldment CTC-028 and compared to the single wire weldment CTC-024. As can be seen in Figure 3-21 the hardness readings increased when compared to the single wire weldment CTC-024. This was as expected due to the lower effective heat input of 79.6 kJ/inch versus 88.5 kJ/inch for CTC-024.

CTC-024 Side 2 CTC-028 Side 2 240 230 s s

e 220 n d

r 210 a H

200 s r

e 190 k c i 180 V 170 160 150 Base Metal HAZ Weld Metal HAZ Base Metal

Figure 3-21. Transverse hardness profile of weldments CTC-024 VS. CTC-028.

Unlike weldments CTC-024, CTC-026, and CTC-027, heat paints were not used to see the actual heat flowing into the base metal for this weldment. Figure 3-22 shows a transverse section from weldment CTC-028. As can be seen, the there are no indications in the weld metal, (e.g., porosity, cracking) and completed penetration was accomplished.

1.25 in.

Figure 3-22. Transverse section of CTC-028.

3.6.7 Weldment CTC-029 111.6 kJ/in Heat Input

The fifth weldment in this task was CTC-029. This weldment was welded with the cold wire lagging the electrode, as shown in Figure 3-16, and the calculated heat input was the same as CTC- 028, (111.6 kJ/in) for the fill and cap passes (See Tables 3-18 and 3-19). This was done to determine whether changing the cold wire orientation at this higher heat input would have any influence on the mechanical properties when compared to weldment CTC-028, which was welded with the cold wire leading the electrode. The tensile and CVN properties are shown in Tables 3-23 and 3-24.

Table 3-23. Tensile and Yield Strength Comparison for Weldments CTC-028 and CTC-029

Specimen Tensile Yield Elongation Reduction Specimen Diameter Strength Strength Increase of Area Identification (in.) (ksi) (ksi) (%) (%) TS1-028 0.4999 92.1 82.9 23 66 TS2-028 0.5000 91.5 82.6 22 68

TS1-029 0.5003 91.2 80.6 26 72 TS2-029 0.4995 90.7 80.8 26 71 Requirement 0.5000 ± 0.0100 - 70–95 22 -

Table 3-24. CVN Comparison for Weldments CTC-028 and CTC-029

Test Absorbed Lateral Fracture Specimen Temperature Energy Expansion Appearance Identification (°F) (ft-lbs) (mils) (% shear) CTC-028-1 -20 55.0 39 59 CTC-028-2 -20 94.1 61 81 CTC-028-3 -20 30.1 21 43 CTC-028-4 -20 110.2 72 87 CTC-028-5 -20 55.2 40 59 Average 68.9 46.6 65.8 St. Dev. 32.5 20.1 18.0

CTC-029-1 -20 77.0 54 67 CTC-029-2 -20 80.0 57 69 CTC-029-3 -20 95.0 67 77 CTC-029-4 -20 86.0 62 74 CTC-029-5 -20 84.0 60 73 Average 84.4 60.0 72.0 St. Dev. 6.9 4.9 4.0 Requirement -20 30 - -

As can be seen from Table 3-23, tensile and yield strengths did not vary significantly between the two methods and all specimens were within the requirement of 70 to 95 ksi. However, there was an increase in both the elongation and reduction in area for weldment CTC-029. Unlike the comparison between CTC-026 (cold wire leading) and CTC-027 (cold wire lagging) at 42.7 kJ/inch heat input, in which the average toughness remained essentially the same, the average toughness for CTC-029 (cold wire lagging) increased by 15.5 ft-lbs (See Table 3-23). The reason for this increase is not known. Given that the leading/lagging cold wire comparison at lower heat input revealed no significant difference in toughness, further investigation should be considered into the effects of cold wire position at various heat inputs. No hardness readings were performed nor were any indicating paints used for this weldment.

3.6.8 Weldment CTC-030 125.4 kJ/in Heat input

The sixth and last weldment in this task was CTC-030. In this weldment, the cold wire led the electrode, and the calculated heat input for the electrode was increased to 125.4 kJ/in for the fill and cap passes. This heat input is significantly over the shipyard limit due to the deterioration in mechanical properties and weld bead appearance. Welding parameters for CTC-030 are shown in

Table 3-25 and the calculated average heat input, effective heat input, and deposition rates using equation 3-2 are shown in Table 3-26.

Table 3-25. Weld Parameters for Weldment CTC-030 Cold Wire Feed SAW

Wire Size (in) Avg. Wire Speed (ipm) Avg. Avg. Travel Weld Current Identification Cold Amps Volts Speed Cold CTC-030 Electrode Wire (ipm) Electrode Wire Root Passes 0.125 0.0625 DCEP 410 30.4 10 53 90 Fill and Cap 0.125 0.0625 DCEP 570 33 9 76 110 Passes

Table 3-26. Heat Input and Deposition Rates for Weldment CTC-030 Cold Wire Feed SAW

Deposition rates were compared to the single wire weldment CTC-024 and the percent increase in deposition rate was calculated for the cold wire feed process with the results shown in Table 3-27.

Table 3-27. Deposition Rate Comparison and Percent Increase for CTC-024 VS. CTC-030

Deposition Deposition Percent Rate Cold- Weld Rate Single Increase in Pass Wire Identification Electrode Deposition Process (lb/hr) Rate (lb/hr) Root Pass 10.9 15.4 41.3% CTC-030 Fill Passes 12.8 21.5 68.0%

As can be seen in Table 3-27, the addition of a cold wire to the single wire SAW process and the increase in heat input from 88.5 to 125.4 kJ/in produced an increase in the deposition rate of the root pass by 41.3 % and a 68.0% increase in the deposition rate for the fill and cap passes. In Table 3-25, note the decrease in heat input from the calculated 125.4 kJ/in to the effective heat input of 91.2 kJ/in for the fill and cap passes. This is only slightly above the 88 kJ/in that was originally used for the single wire baseline weldment CTC-024. As expected, this weldment produced tensile properties similar to the single wire weldment CTC-024 as shown in Table 3-28. Yield strengths are only slightly lower than the single wire weldment due to slightly higher heat input. This is another indication to support the effective heat input theory.

Table 3-28. Tensile and Yield Strength Comparison for Weldments CTC-024 and CTC-030

Specimen Tensile Yield Elongation Reduction Specimen Diameter Strength Strength Increase of Area Identification (in.) (ksi) (ksi) (%) (%) TS1-024 0.4986 90.9 80.7 24 71 TS2-024 0.5001 90.2 80.2 24 70

TS1-030 0.4994 91.0 78.1 25 70 TS2-030 0.4994 89.7 76.7 26 70 Requirement 0.5000 ± 0.0100 - 70–95 22 -

Table 3-29. CVN Comparison for Weldments CTC-024 and CTC-030

CTC-030-1 -20 71.0 49 73 CTC-030-2 -20 71.0 49 73 CTC-030-3 -20 57.0 43 62 CTC-030-4 -20 90.0 59 86 CTC-030-5 -20 86.0 58 82 Average 75.0 51.6 75.2 St. Dev. 13.2 6.8 9.3 Requirement -20 30 - -

In Table 3-29, toughness properties are shown for both weldments. The average toughness for the cold wire feed weldment CTC-030 is actually higher than that of the single wire weldment CTC-024 with an average toughness value better than the single wire weldment and above the requirement of 30 ft-lbs at –20 °F. Hardness readings for weldment CTC-030 are compared to the single wire weldment CTC- 024 in Figure 3-23. The hardness readings of the weld metal increased somewhat when compared to the single wire weldment CTC-024. Considering that the effective heat input of CTC-030 was slightly higher than the single wire weldment CTC-024, this was not expected. Figure 3-24 shows a transverse section of weldment CTC-030, which shows no indications in the weld metal.

CTC-024 Side 2 CTC-030 Side 2

240 230 s

s 220 e n d

r 210 a H

200 s r

e 190 k c i

V 180 170 160 150 Base Metal HAZ Weld Metal Base Metal HAZ

Figure 3-23. Transverse hardness profile of weldments CTC-024 VS. CTC-030.

Figure 3-24. Transverse section of CTC-030.

Weldment CTC-030 exhibited excellent mechanical properties and greatly higher deposition rates. These welding parameters could be used in shipyard production without fear of degradation in mechanical properties or weld integrity. With these parameters and the increase in deposition rate, there will also be a decrease in number of weld beads when compared to the single wire weldment CTC-024. This would be true of all the cold wire feed weldments but CTC-030 represents the best

effort. Figure 3-25 shows the actual placement and number of weld pass required to complete weldment CTC-024 and Figure 3-26 shows the actual placement and number of weld pass required to complete weldment CTC-030. As can be seen from the figures, the number of weld beads decreased from 14 for the single wire process to 8 for weldment CTC-030.

Figure 3-25. Weld bead placement and number, weldment CTC-024.

Figure 3-26. Weld bead placement and number, weldment CTC-030.

3.7 Task 2 HSLA-100 Cold Wire Feed

3.7.1 Weldment CTC-037 Single Wire Process

In this task, two (2) weldments were fabricated using 2-inch HSLA-100 steel and MIL-100S electrodes. The first weldment, CTC-037, was fabricated using the single wire SAW process with a

0.125-inch diameter electrode. All welding parameters are shown in Table 3-31. This weldment was used as the benchmark for the last weldment fabricated using the cold wire process.

Table 3-31. Weld Parameters for Single Wire Benchmark Weldment CTC-037

Wire Size (in) Avg. Wire Speed (ipm) Avg. Avg. Travel Pass Current Cold Amps Volts Speed Cold Electrode Wire (ipm) Electrode Wire Root 0.125 0.0625 DCEP 420 31.1 10.5 57 N/A Fill and Cap 0.125 0.0625 DCEP 415 31.1 9 57 N/A

Table 3-32 shows the calculated average heat input for each pass and the deposition rates using equation 3-1 for weldment CTC-037 with the parameters shown in Table 3-31. It should be noted as with the HSLA-65 weldments, that the heat input calculation does not include the arc efficiency factor for the SAW process.

Table 3-32. Heat Input and Deposition Rates for Weldment CTC-037 Cold Wire Feed SAW

Calculated Weld Avg. Heat Input Reduction Effective Heat Deposition Pass Identification Electrode Factor Input (kJ/in) Rate (kJ/in) (lb/hr) Root 74.5 N/A N/A 11.8 Passes CTC-037 Fill and Cap 86 N/A N/A 11.8 Passes

As can be seen from Table 3-32, the total heat input for the fill and cap passes were at the maximum heat input used by shipyards for welding HSLA-100 steel (85 kJ/in +/- 5 kJ/in). The fabrication documents for welding HSLA-100 normally permit energy input up to 55 kJ/inch, with alternative heat inputs allowed upon NAVSEA approval. NAVSEA had approved SAW up to 110 kJ/inch and some shipyards had qualified procedures at that energy input. However, experience has shown that marginal soundness, bead appearance and mechanical properties are typically

encountered at such a high energy input; thus, shipyards typically limit energy input to less than 85 kJ/inch.

3.7.2 Machining and Testing

Four (4) all weld metal 0.5-inch diameter tension, Six (6) Charpy V-notch, and one (1) metallographic specimen were removed from each of the HSLA-100 weldments. In Figure 3-27 the detailed locations for all specimens removed from each of the two HSLA-100 weldments are shown. All Charpy V-notch specimens were removed at a depth of 0.0625-inchs below the weldment surface. The CVN specimens had the notch located at the weld centerline. All tensile specimens were removed with their centers 0.375 inch below the weldment surface per the requirements of the NAVSEA Technical Publication T9074-BC-GIB-010/0200. Procedure qualification weldments fabricated using MIL-100S electrodes are required to meet the mechanical requirements of NAVSEA Technical Publication T9074-BC-GIB-010/0200, Appendix B, which covers bare solid or cored electrodes for low alloy steels for critical applications. Table 3-33 summarizes the all-weld metal testing requirements of NAVSEA Technical Publication T9074-BC-GIB-010/0200. The higher yield strength requirement of 88–120 ksi has been imposed for undermatched weldments in HSLA-100.

Table 3-33. MIL-100S Weld Metal Requirements for Joining HSLA-100

Test Type Property Requirement Yield Strength 82,000 to 120,000 (min. & max. in psi) Tensile Properties Elongation in 2- 16.0 inches min. (%) Impact Energy 35 ft-lb at –60 °F Charpy V-notch (minimum average) 60 ft-lb at 0 °F

Figure 3-27. Mechanical test specimen locations for all HSLA-100 weldments.

During welding, liquid Penetrant Testing (PT) was performed after backgouging the root pass and after completing the final cap passes. After welding was completed, mechanical tests were performed on weldment CTC-037 and used as the benchmark for the following weldment. The results of the mechanical testing are shown in Table 3-34 and 3-35. Table 3-34 shows that three of the tensile specimens met the requirements of 82 to 120 ksi shown in Table 3-33. Specimen TS4-037 failed in the threads of the specimen shortly after the test began. Visual examination did not reveal the cause of this failure and various reasons could exist. At this time, no further investigation was performed to determine the reason for the failure due to the lack of time and money.

Table 3-34. Tensile Properties for Benchmark Weldment CTC-037 HSLA-100 Steel

Specimen Tensile Elongation Reduction Specimen Yield Diameter Strength Increase of Area Identification Strength (inches) (ksi) (%) (%) TS1-037 0.5007 113.0 101.0 22.5 68.3 TS2-037 0.4996 110.4 94.3 24.0 68.5 TS3-037 0.4996 110.8 92.4 22.5 68.0 TS4-037 0.5002 0.0 0.0 N/A N/A Requirement 0.5000 ± 0.0100 - 82–120 16 -

Table 3-35. CVN Properties for Benchmark Weldment CTC-037 HSLA-100 Steel

Test Absorbed Lateral Fracture Specimen Temperature Energy Expansion Appearance Identification (°F) (ft-lbs) (mils) (% shear) CTC-037-1 0 99.0 57 90 CTC-037-2 0 98.0 67 90 CTC-037-3 0 118.0 75 95 Average 105.0 66.3 91.7 St. Dev. 11.3 9.0 2.9 Requirement 0 60 - -

CTC-037-4 -60 33.0 26 46 CTC-037-5 -60 33.0 25 46 -60 79.0 48 62 Average 48.3 33.0 51.3 St. Dev. 26.6 13.0 9.2 Requirement -60 35 - -

NAVSEA Technical Publication T9074-BC-GIB-010/0200 CVN requirements for MIL- 100S specify that for each testing temperature the average of five (5) tests shall be determined and must not fall below 60 ft-lb at 0 °F and 35 ft-lb at –60 °F. In addition, only one test specimen may have a value below the minimum average and that value must not be more than 10 ft-lb below the minimum average. However due to budgetary constraints, only 3 specimens for each temperature were tested. Table 3-35 clearly shows that all specimens tested at 0°F meet the minimum requirement of 60 ft-lb at 0 °F; unfortunately two (2) of the specimens at -60 °F did not meet the requirement of 35 ft-lb. In this case, even if all five (5) specimens were tested, the outcome would have been the same because the first two failed to meet the requirements. This also shows how difficult it can be to meet the requirements when high heat inputs are used to increase production rates. Hardness readings for CTC-037 were obtained so they could be compared to the cold wire feed weldment. Figure 3-28 shows a transverse section of weldment CTC-037.

2 in.

Figure 3-28. Transverse section of CTC-037.

3.7.3 Weldment CTC-038 124.2 kJ/in Heat input

The last weldment in this task was CTC-038. For this weldment, the cold wire led the electrode and the calculated heat input for the electrode increased from the 86 kJ/in baseline (CTC- 037) to 124.2 kJ/in for the fill and cap passes. This heat input was chosen because it would be an extreme for this material and is significantly over the shipyard limit. Welding parameters for CTC- 038 are shown in Table 3-36 and the calculated average heat input, effective heat input and deposition rates using equation 3-2 are shown in Table 3-37.

Table 3-36. Weld Parameters for Weldment CTC-038 Cold Wire Feed SAW

Wire Size (in) Avg. Wire Speed (ipm) Avg. Avg. Travel Weld Current Identification Cold Amps Volts Speed Cold CTC-038 Electrode Wire (ipm) Electrode Wire

Root Passes 0.125 0.0625 DCEP 420 31.1 10.5 57 90 Fill and Cap 0.125 0.0625 DCEP 600 34.5 10 88 100 Passes

Table 3-37. Heat Input and Deposition Rates for Weldment CTC-038 Cold Wire Feed SAW

Calculated Weld Avg. Heat Input Reduction Effective Heat Deposition Pass Identification Electrode Factor Input (kJ/in) Rate (kJ/in) (lb/hr) Root 74.6 0.717 53.5 16.5 Passes CTC-038 Fill and Cap 124.2 0.779 96.7 23.3 Passes

Deposition rates were compared to the single wire weldment CTC-037 and the percent increase in deposition rate was calculated for the cold wire feed process with the results shown in Table 3-38.

Table 3-38. Deposition Rate Comparison and Percent Increase for CTC-037 VS. CTC-038

Deposition Deposition Percent Rate Cold- Weld Rate Single Increase in Pass Wire Identification Electrode Deposition Process (lb/hr) Rate (lb/hr) Root Pass 11.8 16.5 39.8% CTC-038 Fill Passes 11.8 23.5 99.2%

As can be seen in Table 3-38, the addition of a cold wire to the single wire SAW process and the increase in heat input to 124.2 kJ/in produced an increase in the deposition rate of the root pass by 39.8 % and a 99.2% increase in the deposition rate for the fill and cap passes. In Table 3-37, note the decrease in heat input from the calculated 124.2 kJ/in to the effective heat input of 96.7 kJ/in for the fill and cap passes. This heat input was above the 86 kJ/in that was used for the single wire weldment CTC-037, and was significantly above the 85 kJ/in used in shipyards. Again, these parameters were chosen because they are the extreme. Although the deposition rate was improved by 99.2%, if mechanical properties were not met, the cold wire feed rate could be reduced to achieve acceptable properties while still increasing the deposition rates beyond what is currently being used. During welding, liquid Penetrant Testing (PT) was performed after backgouging the root pass and after completing the final cap passes. After welding was completed, mechanical tests were

performed on weldment CTC-038 and used to compare to the benchmark weldment CTC-037. The results of the mechanical testing are shown in Table 3-39 and 3-40.

Table 3-39. Tensile Property Comparison for Weldments CTC-037 and CTC-038

TS1-038 0.5008 105.8 95.8 7.5 20.6 TS2-038 0.5007 106.2 86.7 14.5 27.9 TS3-038 0.5005 107.6 95.1 10.5 26.0 TS4-038 0.5001 99.0 88.6 8.0 32.1 Requirement 0.5000 ± 0.0100 - 82–120 16 -

Table 3-39 shows that all four of the tensile specimens for CTC-038 meet the yield strength requirement of 82 to 120 ksi shown in Table 3-33. However, none of the specimens met the requirement of 16% minimum elongation as shown in Table 3-33. Visual examination did not reveal to cause for this failure and various reasons could exist, but it was noted that each specimen did show a small area which appeared to show cleavage fracture. Under low magnification, there did not seem to be any indication of “fish eyes” which would indicate hydrogen embrittlement, and each specimen did fail in a ductile manner except for the small area already indicated. At this time, no further investigation was performed to determine the reason for the failure, but it appears that these parameters are beyond the upper limit for this material and electrode combination. Table 3-40 shows the CVN comparison between weldments CTC-037 and CTC-038. The toughness values for the cold wire feed weldment CTC-038 meet the requirements of NAVSEA Technical Publication T9074-BC-GIB-010/0200, Appendix B of 60 ft-lb at 0 °F and 35 ft-lb at –60 °F shown in Table 3-33.

Table 3-40. CVN Properties Comparison for Weldments CTC-037 and CTC-038

CTC-037-4 -60 33.0 26 46 CTC-037-5 -60 33.0 25 46 CTC-037-6 -60 79.0 48 62 Average 48.3 33.0 51.3 St. Dev. 26.6 13.0 9.2 Requirement -60 35 - -

CTC-038-1 0 105.0 62 89 CTC-038-2 0 90.0 61 86 CTC-038-3 0 61.0 44 77 Average 85.3 55.7 84.0 St. Dev. 22.4 10.1 6.2 Requirement 0 60 - -

CTC-038-4 -60 73.0 47 61 CTC-038-5 -60 67.0 45 50 CTC-038-6 -60 61.0 46 50 Average 67.0 46.0 53.7 St. Dev. 6.0 1.0 6.4 Requirement -60 35 - - Note: highlighted cells indicate values that did not meet the requirement.

Hardness readings for weldment CTC-038 were compared to the single wire weldment CTC- 037. As can be seen in Figure 3-29 the hardness readings of the weld metal for the cold wire weldment CTC-038 decreased when compared to the single wire weldment CTC-037. Considering that the effective heat input of CTC-038 was higher than the single wire weldment CTC-037, this was to be expected. This data again reinforces the hypothesis of the effective heat input. Figure 3- 30 shows a transverse section of weldment CTC-030 with no indications and complete penetration.

CTC-037 Side 1 CTC-038 Side 1 410

390

370

s 350 s e n 330 d r a

H 310

290

270

250 Base HAZ Weld Metal HAZ Base

Figure 3-29. Transverse hardness profile of weldments CTC-037 VS. CTC-038.

2 in.

Figure 3-30. Transverse section of CTC-038.

3.8 Task 3 EH-36 Cold Wire Feed

3.8.1 Weldment CTC-031 Single Wire Process

In this task, a total of two (2) weldments were fabricated using 0.5-inch EH-36 steel and Lincoln Electric L-50 (ER70S-3) electrodes. The first weldment, CTC-031, was fabricated using the single wire SAW process with a 0.125-inch diameter electrode. All welding parameters are shown in Table 3-41. This weldment was used as the benchmark for the last weldment fabricated using the cold wire process.

Table 3-41. Weld Parameters for Single Wire Benchmark Weldment CTC-031

Wire Size (in) Avg. Wire Speed (ipm) Avg. Avg. Pass Current Travel Cold Amps Volts Speed Cold Electrode Wire (ipm) Electrode Wire Root 0.125 0.0625 DCEP 325 24.5 10 41 N/A

Fill and Cap 0.125 0.0625 DCEP 410 30.4 9 52 N/A

The parameters shown in Table 3-41 and Table 3-42 show the calculated average heat input for each pass and the deposition rates using equation 3-1 for weldment CTC-031 . The heat input calculation does not include the arc efficiency factor for the SAW process.

Table 3-42. Heat Input and Deposition Rates for Single Wire Benchmark Weldment CTC-031

Calculated Weld Avg. Heat Input Reduction Effective Heat Deposition Pass Identification Electrode Factor Input (kJ/in) Rate (kJ/in) (lb/hr) Root 47.8 N/A N/A 8.5 Passes CTC-031 Fill and Cap 83.1 N/A N/A 10.7 Passes

The author is unaware of any restrictions on the heat input for welding EH-36 steel. Thus, the benchmark weldment was made at 85 kJ/in (+/- 5 kJ/in) as was done for the other two steels.

3.8.2 Machining and Testing

Two (2) all weld metal 0.35-inch diameter tension, Six (6) CVN, and one (1) metallographic specimen were removed from each of the two EH-36 weldments. In Figure 3-31 the detailed locations for all specimens are shown. All CVN specimens were removed at a depth of 0.0625-inch below the weldment surface. The CVN specimens had the notch located at the weld centerline. All tensile specimens were removed with their centers 0.250-inch below the weldment surface.

Figure 3-31. Mechanical test specimen locations for all EH-36 weldments.

Mechanical test requirements for procedure qualification of a 3M or 3YM electrode for SAW in accordance with ABS document, Rules for Materials and Welding Part 2, 2006, section 2-A2-1 is shown in Table 3-43.

Table 3-43. 3M or 3YM Weld Metal Requirements for Joining EH-36

Test Type Property Requirement Tensile Properties Yield Strength min. 58,000 (psi) Tensile Strength 71,000 to 95,000 (min. & max. in psi) Charpy V-notch Impact Energy 35 ft-lb at –20 °F (minimum average)

During welding, PT was performed after backgouging the root pass and after completing the final cap passes. After welding was completed, mechanical tests were performed on weldment CTC- 031 and used as the benchmark for the following weldment. The results of the mechanical testing are shown in Table 3-44 and 3-45. Table 3-44 shows that the tensile specimens meet the requirements shown in table 3-39 for 3M or 3YM electrodes.

Table 3-44. Tensile Properties of Benchmark Weldment CTC-031

Specimen Tensile Elongation Reduction Specimen Yield Diameter Strength Increase of Area Identification Strength (inches) (ksi) (%) (%) TS1-031 0.3495 83.6 69.1 39 80 TS2-031 0.3492 83.4 69.7 41 81 Requirement 0.3500 ± 0.0070 71–95 58 - -

Table 3-45. CVN Properties of Benchmark Weldment CTC-031

Test Absorbed Lateral Fracture Specimen Temperature Energy Expansion Appearance Identification (°F) (ft-lbs) (mils) (% shear) CTC-031-1 -20 8.0 8 20 CTC-031-2 -20 10.0 9 20 CTC-031-3 -20 15.0 14 25 CTC-031-4 -20 10.0 9 20 CTC-031-5 -20 11.0 11 20 Average 10.8 10.2 21.0 St. Dev. 2.6 2.4 2.2 Requirement -20 35 - -

As can be seen in table 3-45, none of the specimens met the requirement of the ABS specification; in fact they failed to meet the requirement by a significant amount. Thus, when deposited in a relatively thin (0.5 inch) plate at high heat inputs, the actual weld metal CVN toughness can be much lower than the current ABS requirements. Figure 3-32 shows a transverse section of weldment CTC-031.

0.5 in.

Figure 3-32. Transverse section of CTC-031.

3.8.3 Weldment CTC-033 100.5 kJ/in Heat input

The next weldment was made with the cold wire feed process to see if there would be any significant improvement in toughness. Weldment CTC-033 was welded with the cold wire leading the electrode, and the calculated heat input for the electrode increased from the 83.1 kJ/in benchmark to 100.5 kJ/in for the fill and cap passes. Welding parameters for CTC-033 are shown in Table 3-46 and the calculated average heat input, effective heat input and deposition rates using equation 3-2 are shown in Table 3-47.

Table 3-46. Weld Parameters for Weldment CTC-033 Cold Wire Feed SAW

Wire Size (in) Avg. Wire Speed (ipm) Avg. Avg. Travel Weld Current Identification Cold Amps Volts Speed Cold Electrode Electrode CTC-033 Wire (ipm) Wire Root Passes 0.125 0.0625 DCEP 325 25.4 10 41 90 Fill and Cap 0.125 0.0625 DCEP 515 32.5 10 71 90 Passes

Table 3-47. Heat Input and Deposition Rates for Weldment CTC-033 Cold Wire Feed SAW

Calculated Weld Avg. Heat Input Reduction Effective Heat Deposition Pass Identification Electrode Factor Input (kJ/in) Rate (kJ/in) (lb/hr) Root 49.5 0.646 32 13.1 Passes CTC-033 Fill and Cap 100.5 0.722 76.3 19.3 Passes

Deposition rates were compared to the single wire weldment CTC-031 and the percent increase in deposition rate was calculated for the cold wire feed process with the results shown in Table 3-48.

Table 3-48. Deposition Rate Comparison and Percent Increase for CTC-031 VS. CTC-033

Deposition Deposition Percent Rate Cold- Specimen Rate Single Increase in Pass Wire Identification Electrode Deposition Process (lb/hr) Rate (lb/hr)

CTC-033 Root Pass 8.5 13.1 54.1% Fill Passes 10.7 19.3 80.4%

As can be seen in Table 3-48, the addition of a cold to the single wire SAW process and the increase in heat input to 100.2 kJ/in produced an increase in the deposition rate of the root pass by 54.1 % and an 80.4% increase in the deposition rate for the fill and cap passes. In Table 3-47, note the decrease in heat input from the calculated 100.2 kJ/in to the effective heat input of 76.3 kJ/in for the fill and cap passes. This is below the 83.1 kJ/in that was originally used for the single wire weldment CTC-031. Given this information, it would be expected that this weldment would produce mechanical properties better than the single wire weldment CTC-031, especially weld metal toughness. However, this is not what was observed as shown in Table 3-49 and Table 3-50. Yield strengths and toughness properties were slightly lower than the single wire weldment.

Table 3-49. Tensile and Yield Strength Comparison for Weldments CTC-031 and CTC-033

Specimen Tensile Yield Elongation Reduction Specimen Diameter Strength Strength Increase of Area Identification (in.) (ksi) (ksi) (%) (%) TS1-031 0.3495 83.6 69.1 39 80 TS2-031 0.3492 83.4 69.7 41 81

TS1-033 0.3498 81.5 65.8 39 78 TS2-033 0.3492 82.0 66.0 37 78 Requirement 0.3500 ± 0.0070 71–95 58 - -

Table 3-50. CVN Comparison Weldments CTC-031 and CTC-033

CTC-033-1 -20 11.0 13 20 CTC-033-2 -20 10.0 11 20 CTC-033-3 -20 12.0 10 20 CTC-033-4 -20 7.0 5 18 CTC-033-5 -20 9.0 9 18 Average 9.8 9.6 19.2 St. Dev. 1.9 3.0 1.1

Shipyards have experienced similar problems with joining thin section EH-36 steel at high heat inputs. The problem is often overcome by reducing the heat input and using a nickel-containing welding electrode to meet the toughness requirements. If the standard carbon steel electrodes were to be used, heat inputs needed to be at or below 50 kJ/in to meet the toughness properties. Additional development needs to be performed in order to produce welding parameters to meet the properties for this material.

The hardness readings for CTC-033 were compared to the single wire weldment CTC-031. As can be seen in Figure 3-33 the hardness readings of the weld metal for the cold wire weldment CTC-033 remained essentially the same when compared to the single wire weldment CTC-031. Considering that the effective heat input of CTC-033 was lower than the single wire weldment CTC- 031 by only 6.8 kJ/in, this was to be expected. Figure 3-34 shows a transverse section of weldment CTC-033.

CTC-031 Side 1 CTC-033 Side 1

220

210

200 s

s 190 e n d r

a 180 H 170

160

150 Base Metal HAZ Weld Metal HAZ Base Metal

Figure 3-33. Transverse hardness profile of weldments CTC-031 VS. CTC-033.

Figure 3-34. Transverse section of CTC-033.

4.0 BENEFITS AND SAVINGS

4.1 Cold Wire Feed SAW of HSLA-65 Steel

Weldment CTC-030 represents the best parameters for CWF-SAW of HSLA-65 steel. That weldment produced a 68% increase in deposition rate when compared to the single wire weldment CTC-024. Figure 3-35 summarizes a cost savings analysis that was for weldments CTC-024 and CTC-030. Based on data supplied from the shipyards, $60.00 per hour labor rate was used for all calculation, electrode and flux cost were based on actual data supplied from the manufacturers. For weldment CTC-024, the total cost per foot of weld would be approximately $24.0 with a shift productivity of 51.8 lb of weld metal deposited in an 8-hour shift. Total cost per foot of weld for the cold wire feed weldment CTC-030 would be $18.58 with a shift productivity of 85.9 lb of weld metal welded in an 8-hour shift. Therefore, the cold wire feed process would produce a cost saving of 22.6% relative to the single wire weldment. Figure 3-35 shows the results of the cost savings. The results suggest that higher deposition rates could be obtained with HSLA-65 steel, which would result in higher cost savings than shown. However, a 22.6% cost savings with a $2,100 investment in additional equipment is a significant achievement.

Figure 3-35. Cost saving comparison for single wire SAW vs. CWF-SAW of HSLA-65.

4.2 Cold Wire Feed SAW of HSLA-100 Steel

Figure 3-36 summarizes a cost savings analysis that was for weldments CTC-037 and CTC- 038. If the cold wire feed weldment would have meet the tensile elongation requirements, a total cost saving would have been 28.5%. Weldment CTC-038 produced a 97.5% increase in deposition rate when compared to the single wire weldment CTC-037. For the single electrode weldment CTC- 037, the total cost per foot of weld would have been approximately $64.02 with a shift productivity of 47.1 lb of weld metal welded in an 8-hour shift. Total cost per foot of weld for the cold wire feed weldment CTC-038 would have been $45.77 with a shift productivity of 93.4 lb of weld metal welded in an 8-hour shift.

Figure 3-36. Cost saving comparison for single wire SAW vs. CWF-SAW of HSLA-100.

If welding would have been performed with the parameters show in Table 3-48, the potential cost savings would have been 26.3%. The new weldment would have produced an 83.1% increase in deposition rate when compared to the single wire weldment CTC-037. For the single electrode weldment CTC-037, the total cost per foot of weld would have been approximately $64.02 with a shift productivity of 47.1 lb of weld metal welded in an 8-hour shift. Total cost per foot of the new weld for the cold wire feed process would have been $47.23 with a shift productivity of 86.47 lb of weld metal welded in an 8-hour shift. The detailed information for this cost savings is shown in Figure 3-37.

Figure 3-36. Cost Saving Comparison for New HSLA-100 CWF-SAW weldment.

4.3 Cold Wire Feed SAW of EH-36 Steel

No cost calculations were performed for these weldments because mechanical properties failed to meet the requirements. At this time, the author could not develop welding parameters with any confidence due to lack of available information on welding this material.

5.0 SUMMARY AND CONCLUSIONS

5.1 Cold Wire Feed SAW of HSLA-65 Steel

Deposition rates of the CWF-SAW weldments were increased from 36% to 68% for the HSLA-65 weldments when compared to the benchmark weldment made with the single wire SAW process at approximately 85 kJ/in heat input. Heat inputs were increased from 85 kJ/in to a maximum of 125 kJ/in with no deterioration in mechanical properties, which is a significant improvement. As deposition rates increased, both yield and tensile strengths increased slightly with the most dramatic improvement in weld metal toughness; this was true for all HSLA-65 weldments. Hardness readings for all weldments increased as the amount of heat entering the weldment decreased. The increase in hardness indicates an increase in the cooling rate of the weld and supports the hypothesis of the cold wire addition lowering the effective heat input. All cold wire feed welding ran smoothly with no complications noted with the process. Root pass welding for all weldments was also conducted using the CWF-SAW process. Typically with twin-arc SAW or tandem arc SAW a separate process such as GMAW or FCAW is used to deposit the root pass, which is an added cost. The CWF-SAW process eliminated the need for a separate welding process for the root pass, which will reduce set-up and handling time.

5.2 Cold Wire Feed SAW of HSLA-100 Steel

For the HSLA-100 task, two (2) weldments were produced, one (1) benchmark weldment using the single wire process at approximately 85 kJ/in heat input and a second weldment made using the CWF-SAW process at 124 kJ/in heat input. Deposition rates were increased 39% for the root pass and 97.5% for the fill and cap passes using the cold wire feed process. All yield strength and toughness properties of the cold wire weldment meet the requirements for MIL-100S, however elongation requirements were not meet. This would indicate that an upper limit for the welding parameters was exceeded for this material and filler metal combination. It should be noted that the single wire benchmark weldment did not meet the -60 °F toughness requirement.

5.3 Cold Wire Feed SAW of EH-36 Steel

The single wire weldment using a Lincoln Electric LA-50, AWS EM13K electrode met the requirements of 71 ksi–95 ksi tensile strength per the ABS document, Rules for Materials and

Welding Part 2, 2006, section 2-A2-1, Table 1 for a 3M or 3YM electrode. In addition, the weldment also meet the requirement of 58 ksi for the yield strength. However, none of the specimens met the procedure qualification CVN requirement of 35 ft-lb at -20 °F in accordance with the ABS specification; in fact they failed to meet the requirement by a significant amount. This was also true for the cold wire weldment for this steel. Again, the toughness requirements could not be met even though the effective heat input was below the heat input for the single wire weldment.

6.0 Recommendations

6.1 Cold Wire Feed SAW of HSLA-65 Steel

Results for the HSLA-65 material were very promising. Additional research should be performed with this material and the CWF-SAW process to optimize performance. Additional testing should be performed such as CVN testing of the HAZ and a more in-depth study into the effective heat input theory using thermocouples. This project did not produce a maximum heat input for this material, therefore, additional weldments should be made increasing the heat input beyond the 124 kJ/in that was used in this project until a maximum is found. Distortion should also be investigated with this and all other materials when using the CWF- SAW process. Although this project did not focus specifically on distortion control, it was noted that the plates that were welded using the CWF-SAW process visually exhibit less distortion than the plate using the single wire SAW process.

6.2 Cold Wire Feed SAW of HSLA-100 Steel

With the valuable information produced in this report for HSLA-100 material, the author is confident that welding parameters can be developed to meet the requirements of the specification and still produce at least an 80% increase in deposition rates. As an example, parameters could have been adjusted to develop a deposition rate of 21.6 lb/hr and an effective heat input of 81.6 kJ/in. This would produce an 83.1% increase in the deposition rate at a decreased cost, which is still a significant increase in production. See Tables 3-51–3-53 for parameters and deposition rates.

Table 3-51. Weld Parameters for New HSLA-100 Cold Wire Feed SAW Weldment

Specimen Wire Size (in) Avg. Wire Speed (ipm) Avg. Avg. Identification Current Travel New HSLA- Cold Amps Volts Speed Cold 100 Electrode Wire (ipm) Electrode Wire Root Passes 0.125 0.0625 DCEP 420 31.1 10.5 57 90 Fill and Cap 0.125 0.0625 DCEP 570 32.5 10 76 110 Passes

Table 3-52. Heat Input and Deposition Rates for New HSLA-100 Cold Wire Feed Weldment

Avg. Heat Calculated Effective Specimen Input Reduction Deposition Pass Heat Input Identification Electrode Factor Rate (kJ/in) (kJ/in) (lb/hr) Root 78.4 0.717 56.2 16.4 Passes New HSLA- 100 Fill and Cap 111.2 0.734 81.6 21.6 Passes

Table 3-53. Deposition Rate Comparison and Percent Increase New HSLA-100 Weldment

Deposition Deposition Percent Rate Cold- Specimen Rate Single Increase in Pass Wire Identification Electrode Deposition Process (lb/hr) Rate (lb/hr) New HSLA- Root Pass 11.8 16.4 39.0% 100 Weldment Fill Passes 11.8 21.6 83.1%

It is the authors’ opinion that the new parameters would have produced satisfactory mechanical properties. This is based on the current work with the HSLA-65 steel and previous worked conducted through the NMC for cold wire feed SAW of HSLA-100 steel [6].

6.3 Cold Wire Feed SAW of EH-36 Steel

Additional work needs to be performed in order to produce welding parameters to meet the mechanical property requirements for this material. The problem with the low CVN results may be overcome by reducing the heat input and using a welding electrode containing a high nickel content to meet the toughness requirements. Welding should be conducted starting with the single wire SAW process at a heat input of 50 kJ/in using a standard carbon steel electrode to see if toughness requirements can be meet. If toughness requirements are not met at 50 kJ/in the heat input should be decreased to 40 kJ/in and mechanical testing performed. This should continue until a heat input is reached that would produce satisfactory toughness results. Once toughness requirements are met, heat inputs can be increased until an upper limit for heat input is met for the single wire SAW process. After adequate procedures have been developed, and maximum heat inputs are established, CWF-SAW process can be used to determine deposition rate increases and mechanical property improvements.

7.0 REFERENCES

1. Synergic Cold Wire Submerged Arc Welding of High Alloyed Stainless Steels, L. Karlsson, H. Arcini, P. Dyberg, S. Rigdal and M. Thuvander, ESAB AB, 2002, pp. 285–286.

2. Submerged Arc Welding of Low-Carbon Copper-Strengthened Alloy Steel, R.J. Jesseman, and G.J. Murphy, Welding Journal, Vol. 62, No. 11 November 1983, pp. 321s–330s.

3. Evaluation of HSLA-65 (ASTM A 945, Grade 65) Steel for Surface Combatant Structures, E.J. Czyryca, J.J. DeLoach, and E.M. Focht, Naval Surface Warfare Center Carderock Division, NSWCCD-61-TR-2001/20 December 2001, pg. Xiii.

4. Welding Metallurgy Vol. 1, G.E. Linnert, GML Publications, Hilton Head Island, South Carolina, p. 749, 1994, ISBN: 0-87171-457-4.

5. Welding Filler Metal Data Book, ESAB Welding and Cutting, 2005, p. 7-2.

6. “Manufacturing Large Marine Structures – NCEMT Tasks: Task 3 – Weld Procedure Robustness Optimization, Final Report,” Mark F. Mruczek and Paul J. Konkol, NCEMT TR No. 05-044, Concurrent Technologies Corporation, Johnstown, PA, 30 April 2005, p. 27

8.0 Appendices

8.1 Appendix A: CTC Experience

8.2 CTC Capabilities – Welding Applications

CTC is an independent, nonprofit, applied research and development professional services organization that provides technology-based solutions to a wide variety of clients representing state and federal government as well as the private sector. CTC addresses welding application projects with experienced teams of mechanical, material and welding engineering staff. CTC uses state-of- the-art computer-aided engineering tools and technologies to enhance our clients’ product quality, producability and cost effectiveness. CTC staff experts have built virtual product models and have performed numerically-based simulations to support welding applications and product evolution from concept to shop floor fabrication. CTC applies advanced manufacturing techniques, computer aided engineering, design for manufacturing and assembly, prototyping and numerical analysis capabilities from the development of the design concept through final fabrication. Concurrent engineering principles are applied for total systems integration. The following paragraphs describe CTC’s design and manufacturing capabilities toward welding applications.

8.2.1 Design for Manufacturing and Assembly

CTC incorporates a design philosophy for weld fabrication design from start to finish that will aid in the transition of computer/paper designs into fabricated part/assemblies. CTC can bridge the gap between fabrication and design before a part is created on the manufacturing floor. This virtual development relies upon concurrent engineering teams, which understand welding theory, metallography, welding practices, welding code/specifications and ship building.

8.2.2 Prototyping of Components and Assemblies

CTC has built capabilities and expertise in full service machine and welding shops that quickly develop prototypes for test and evaluation purposes and to provide correlation to numerical modeling for simple to complex systems. These capabilities are critical to ensure designs are sufficient to meet customer requirements.

8.2.3 Machine Shop

The machining areas at CTC heavily support responsiveness and flexibility in meeting project requirements from machining test specimens and fixtures to fabricating subassemblies. The machining area contains a lean amount of equipment necessary to support the projects. The core machining equipment is used in a flexible manner to provide capabilities for CNC turning, CNC milling, surface grinding, wire Electrical Discharge Machining (EDM) and cutting saws. Manual mills and lathes are also available for use. Some examples of this equipment include a CNC Cincinnati Milacron Sabre-750 three-axis milling center, a Fanuc Robocut Alpha-1B Submersible four-axis EDM, a Mori Seki CNC turning machine equipped with rotary tooling for milling, drilling and tapping operations and a Gallmeyer & Livingston precision surface grinder that can be used for flat, radius and angle finishes capable of attaining 10" within 0.0001".

8.2.4 Weld Shop

The welding area consists of a variety of equipment to support various welding processes. An overhead crane allows materials to be moved efficiently and safely. An environmentally controlled clean room is capable of temperature and humidity control to extreme conditions. GMAW, gas tungsten arc welding (GTAW), plasma arc welding (PAW), submerged arc welding (SAW), electroslag surfacing (ESS) and cutting operations are available to support project requirements. Some examples of the GMAW welding equipment include a Lincoln Idealarc 500, Miller Synchrowave 500, Miller Deltaweld 451 and Lincoln Power Wave 455M. For GTAW welding, a Miller Synchrowave 350 with AC/DC constant power source and manual or automatic torch is available. A Thermal Dynamic PS 3000 is used for PAW welding, has a 300-amp power supply complete with thermal arc sequencer and is able to run in manual or automatic modes. A Miller Pulstar 450, Miller Spectrum 1500 and Airco welding and cutting torches for oxygen acetylene cutting are available to support cutting operations. Preheating units, fixturing devices, turning rolls and portable air filtration units are available to support welding operations.

8.2.5 Coordinate Measuring Machine (CMM)

CTC has a calibrated CMM machine/surface plate in a controlled temperature and positive pressure environment.