AWS C5.7:2000 (R2006) An American National Standard

Recommended Practices for Electrogas AWS C5.7:2000 (R2006) An American National Standard

Approved by the American National Standards Institute May 5, 2000

Recommended Practices for

Supersedes ANSI/AWS C5.7-89

Prepared by the American Welding Society (AWS) C5 Committee on and Cutting

Under the Direction of the AWS Technical Activities Committee

Approved by the AWS Board of Directors

Abstract

Electrogas Welding (EGW) is a specialized welding process having similarities to the (GMAW) or the flux cored arc welding (FCAW) processes for vertical position welding. The deposits in the cavity formed by backing plates or shoes that bridge the groove between the plates being welded. The elec- trode may be solid, metal cored, or flux cored, and additional shielding may or may not be obtained from an externally supplied gas or gas mixture. The weld is usually completed in a single pass. Fundamentals of the process, including the various methods of welding, are presented. A discussion of equipment, consumables, applications, and metallurgical advantages and limitations is provided. The selection of process variables and operating conditions and typical EGW procedures is then presented. Inspection of welds, and training and qualifica- tion of welding procedures and operators are described. Finally, a troubleshooting guide, safety considerations, and a supplementary reading list are presented.

550 N.W. LeJeune Road, Miami, FL 33126 AWS C5.7:2000 (R2006)

Table of Contents

Page No. Personnel (Reaffirmation)...... v Personnel (Original) ...... vii Foreword ...... ix List of Tables ...... xiii List of Figures...... xiv 1. General ...... 1 1.1 Scope ...... 1 1.2 Introduction ...... 1 2. Referenced Standards...... 1 3. Definitions ...... 3 4. Fundamentals ...... 5 4.1 Process Description ...... 5 4.2 Principles of Operation...... 5 4.3 Electrode Variations ...... 5 4.4 Consumable Guide Variations...... 6 5. Equipment...... 9 5.1 Welding Power Source...... 9 5.2 Wire (Electrode) Feeder ...... 9 5.3 Electrode Guide Oscillators...... 9 5.4 Electrode Guide...... 9 5.5 Backing Shoes (Dams) ...... 9 5.6 Controls ...... 10 6. and ...... 10 6.1 Electrodes ...... 10 6.2 Shielding...... 10 6.3 AWS Specification for Electrogas Filler Metal...... 10 7. Applications ...... 10 7.1 Base Metals ...... 10 7.2 Joint Design...... 11 7.3 Assembly and Alignment ...... 11 7.4 Typical Applications ...... 14 8. Metallurgical Advantages and Limitations...... 14 8.1 Electrogas Welding Thermal Cycle...... 14 8.2 Weld Macrostructure...... 22 8.3 Preheat ...... 23 8.4 Postweld Heat Treatment ...... 24 8.5 Residual Stresses and Distortion ...... 24 8.6 Mechanical Properties ...... 24 9. Selection of Process Variables and Other Welding Conditions ...... 27 9.1 Welding Voltage...... 27 9.2 Welding Current—Wire Feed Speed...... 27

xi AWS C5.7:2000 (R2006)

Page No. 9.3 Form Factor ...... 27 9.4 Electrode Extension...... 29 9.5 Electrode Oscillation ...... 29 9.6 Joint Opening...... 29 9.7 Work Lead...... 30 9.8 EGW Procedures ...... 30 10. Inspection of Welds and Rework ...... 30 10.1 Methods of Inspection ...... 30 10.2 Acceptance ...... 30 10.3 Quality Control...... 30 10.4 Rework ...... 30 11. Training...... 45 11.1 Process Variables...... 45 11.2 Equipment Familiarization ...... 47 12. Qualifications...... 47 12.1 Process and Equipment...... 47 12.2 Welding Procedure ...... 47 12.3 Welding Operator ...... 47 13. Troubleshooting Guide ...... 47 13.1 Weld Start Porosity...... 47 13.2 Weld Porosity ...... 47 13.3 Weld Termination Porosity ...... 48 13.4 Centerline Weld Cracking ...... 48 13.5 Incomplete Fusion at Weld Toes...... 48 13.6 Incomplete Fusion to One Groove Face...... 48 13.7 Overlap and Poor Fusion...... 48 13.8 Underfill ...... 48 13.9 Starting Tab Melt-Through...... 48 13.10 Pickup ...... 48 13.11 Metal Spillage...... 48 13.12 Electrode Wander ...... 49 13.13 Arcing to Groove Faces...... 49 13.14 Hourglass Nugget Shape ...... 49 14. Safety Recommendations...... 49 14.1 Radiant Energy ...... 49 14.2 Burn Protection...... 50 14.3 Electrical Hazards...... 50 14.4 Fumes and Gases ...... 50 14.5 Noise and Hearing Protection...... 51 14.6 Safety and Health Information Sources...... 51 Annex A (Informative)—Safety and Health References...... 53 Annex B (Informative)—Supplementary Reading List ...... 55 Annex C (Informative)—Guidelines for the Preparation of Technical Inquiries...... 57 List of AWS Documents on Arc Welding and Cutting...... 59

xii AWS C5.7:2000 (R2006)

List of Tables

Table Page No. 1 Chemical Composition Requirements for Solid Electrodes ...... 11 1A Chemical Composition Requirements for Weld Metal From Composite Flux Cored and Metal Cored Electrodes...... 12 2 A5.26 Tension Test Requirements (As-Welded)...... 13 2M A5.26M Tension Test Requirements (As-Welded) ...... 13 3 A5.26 Impact Test Requirements (As-Welded)...... 13 3M A5.26M Impact Test Requirements (As-Welded) ...... 13 4 Typical As-Welded Mechanical Properties of Structural Steels Welded with Self-Shielded Flux Cored Electrodes...... 25 5 Typical As-Welded Mechanical Properties of Steels Welded with Gas Shielded Flux Cored Electrodes...... 26 6 As-Welded Notch Toughness Properties of Electrogas Weld in 1 in. (25 mm) Thick A 283 Steel...... 27 7 Commonly Used Settings for Electrogas Welds with AWS Class EG72T-1 Electrode with Moving Shoe(s)...... 31 8 Commonly Used Settings for Electrogas Welds with AWS Class EG72T-1 Electrode with Consumable Guide Tube...... 33 9 Commonly Used Settings for Electrogas Welds with AWS Class EG72T-NM1 Electrode with Moving Shoe(s)...... 37 10 Commonly Used Settings for Electrogas Welds with AWS Class EG70S-1 Electrode with Moving Shoe(s)...... 40 11 Typical EGW Procedure Specification with Moving Shoe(s) ...... 41 12 Typical EGW Procedure Specification Using Consumable Guide Tubes and Fixed Copper Shoe(s)...... 42 13 Typical Electrogas Checklist with Moving Shoe(s) ...... 43 14 Typical Electrogas Checklist for Welding with Consumable Guide Tubes and Fixed Copper Shoe(s) .....45

xiii AWS C5.7:2000 (R2006)

List of Figures

Figure Page No. 1 Schematic Diagram of EGW Process Using a Moving Shoe and a Stationary Shoe ...... 4 2 Schematic Diagram of EGW Process Using Two Moving Shoes ...... 4 3 Electrogas Welding with Solid Electrode Using Moving Shoes ...... 5 4 Electrogas Welding with Flux Cored Electrode ...... 6 5 Consumable Guide EGW Equipment ...... 7 6 Schematic Diagram of Consumable Guide EGW Process...... 8 7 Typical EGW Joint Designs...... 14 8 Alternate EGW Joint Designs...... 15 9 Typical Brackets Used for EGW Joint Assembly...... 16 10 Typical Arrangement of Starting, Run-off Tabs, and Brackets for EGW Joint Assemblies ...... 16 11 Electrogas Welding of a Ship Hull Using Two Machines Controlled by One Operator ...... 17 12 Field Electrogas Welding of a Storage Tank ...... 18 13 A Portable EGW Unit Housed in a Special Elevator Cage...... 19 14 A Self-Contained EGW Unit Used in Ship Building...... 20 15 Electrogas Welding of Vertical Joints for Surge Tanks...... 21 16 Knoop Microhardness Survey Across Electrogas Weld in an A 283 Grade C Base Metal...... 22 17 Knoop Microhardness Survey Across Shielded Metal Arc Weld (Vertical Up) in an A 283 Grade C Base Metal ...... 23 18 Effect of Welding Voltage on the Shape of the Weld Pool ...... 28 19 Effect of Welding Current on the Shape of the Weld Pool...... 28 20 Sketches of Weld Macrostructure of a Vertical Section of an Electrogas Weld ...... 28 21 Effect of Electrode Extension (with CP Power Supply) on the Shape of the Weld Pool ...... 29 22 Typical EGW Restart Procedure...... 46 23 Weld Defects in EG Welds Caused by Improper Technique or Defective Equipment, or Both ...... 46

xiv AWS C5.7:2000 (R2006)

Recommended Practices for Electrogas Welding

1. General efficiency, weld metal soundness, simple joint prepara- tion, and other advantages. 1.1 Scope. This document provides recommended prac- Some of the advantages associated with EGW result in tices for electrogas welding low carbon pressure vessel, considerable cost savings, particularly in joining thicker and structural steels. Aluminum and are materials. Savings have been achieved when joint mem- excluded because of a lack of general commercial use of bers can be joined in the vertical position and where thick electrogas welding for these materials. This standard base metal can be joined with a continuous vertical weld. makes use of the U.S. Customary Units. Approximate EGW is often less expensive than the more conventional mathematical equivalents in the International System of joining methods such as (SAW) Units (SI) are provided for comparison in parentheses ( ) and flux cored arc welding (FCAW) in thicker base met- or in appropriate columns in tables and figures. als or flat position welding by submerged arc welding Safety and health issues and concerns are beyond the (SAW) with the prohibitive associated material handling. scope of this standard and, therefore, are not fully ad- Even in some applications involving thinner base metals, dressed herein. Some safety and health information can EGW has resulted in cost savings because of its effi- be found in Section 14. Safety and health information is ciency, simple joint preparation, etc. available from other sources, including, but not limited There are two primary variations of the EGW process to, ANSI Z49.1, Safety in Welding, Cutting, and Allied commonly used in the United States. In the first method, Processes, and applicable federal and state regulations. a solid electrode is fed into the joint. When using a solid electrode, external shielding gas is required. In the sec- 1.2 Introduction. (ESW) was the ond method, a flux cored or metal cored electrode is first single-pass vertical welding process made commer- used. When using flux cored electrodes, both the exter- cially available. Immediately after its successful imple- nally gas shielded types, and self-shielded types are mentation, there was a demand for equipment that would available. These methods of EGW for plain carbon, enable similar techniques to be applied to workpieces structural, and pressure vessel quality steels will be dis- with thinner sections than is generally possible with cussed in more detail later in these recommended prac- 1 ESW. Until ESW became available in 1961, almost all tices. Although EGW has been used to join aluminum vertical joints were welded with the manual shielded and some grades of stainless steels, those applications metal arc or semiautomatic gas metal arc welding pro- are not discussed in this document. cess. Laboratory evaluation using a flux cored electrode with auxiliary gas shielding and an adaptation of an elec- troslag machine determined that a plate as thin as 1/2 in. (13 mm) could be welded in the vertical position at high 2. Referenced Standards speeds by the single-pass electrogas technique. Electro- gas welding (EGW) has enjoyed steady growth in the The following standards have been cited in this United States in recent years. This growth has occurred, document: not only because the process has inherent out-of-position ABS Rules for Building and Classing Steel Vessels capability, but also due to its high deposition rate, high Available through: American Bureau of Shipping 16855 Northcase Drive 1 See Supplementary Reading List, Annex B, item number 8. Houston, TX 77060

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