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Effect of Friction Welding Parameters on Mechanical and Microstructural Properties of Dissimilar AISI 1010-ASTM B22 Joints

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Effect of Friction Welding Parameters on Mechanical and Microstructural Properties of Dissimilar AISI 1010-ASTM B22 Joints Kurt et al Supplement May 2011:Layout 1 4/11/11 11:16 AM Page 102 Effect of Friction Welding Parameters on Mechanical and Microstructural Properties of Dissimilar AISI 1010-ASTM B22 Joints In this study, the characteristic of structures, tensile properties, hardness values, and microstructural changes of friction joints were investigated BY A. KURT, I. UYGUR, AND U. PAYLASAN ABSTRACT it is necessary to produce high-quality joints between them. Typical solid-state Rotary friction welding is one of the most economical and efficient production meth- joining applications of diffusion welding ods for joining similar and dissimilar materials. It is widely used with metals and thermo- for various content of the aluminum metal matrix composites (Refs. 5–7) and friction WELDING RESEARCH plastics in a wide variety of aviation, transport, and aerospace industrial component de- signs. Individually, mild steel to mild steel and copper to copper are normally easy to weld stir welding (Ref. 8) have been studied in by fusion welding methods, but the joint of mild steel to copper can be extremely difficult detail. Welding copper alloys is usually dif- due to the differences in the two materials’ melting temperature, density, strength, and ficult using a conventional fusion welding thermal conductivity. Thus, these kinds of problems can be eliminated by a solid-state fric- process because copper has high thermal tion welding technique. Hence, the current study attempts to understand the friction weld- diffusivity, which is about 10 to 100 times ing characteristics of mild steel-bronze dissimilar parts. This study looks into the influence higher than in many steels and nickel al- of process parameters, which includes friction pressure, upsetting pressure, and upset time loys. The effects of diffusion welding pa- on the axial shortening, hardness, microstructure, and tensile properties of the welds. The rameters on the mechanical response of optimum parameters for upset time, upset pressure, and friction pressure necessary for low carbon steel and commercially pure welding were obtained. Finally, the obtained mechanical properties results were com- copper were studied in detail by Kurt et al. mented on the light of optical microscopy. (Ref. 5). Welding time, applied load, weld- ing temperature, and chemical composi- Introduction good mechanical and physical properties. tion of the steel are some of the key pa- It is an easy process to weld these materi- rameters to controlling the solid-state diffusion welding process. Welding of machinery components is als by themselves. Unfortunately, most Rotary friction welding is one of the compulsory in most engineering applica- engineering materials have to join with solid-state techniques that is applied to tions. Just a few decades ago, materials dissimilar counterparts. Thus, it is difficult the joining of similar and dissimilar coun- were classified as weldable and nonweld- to obtain good-quality weld joints using terparts. In this technique, machinery able, but innovations in technology al- molten welding methods. Some defects components are brought into contact. lowed joining of most materials by fusion and intermetallic phases can occur during While one of them remains stationary, the and solid-state welding techniques. Typi- the process because of the great differ- other is rotated with the applied pressure. cal fusion welding techniques include gas ences between Fe and Cu in physical, me- When the temperature of the interfaces welding (oxyacetylene), arc welding chanical, and chemical properties. Table 1 has reached an optimum value for the ex- (shielded metal, gas tungsten, and sub- shows some physical and mechanical tensive plastic deformation, the rotation is merged), and high-energy beam welding properties of AISI 1010 mild steel and stopped, while the forging pressure re- (electron and laser). Heat sources for ASTM B22 copper bronze (Ref. 4). These mains unchanged or increased. The appli- these techniques are a gas flame, an elec- metals have good electrical and heat con- cation of an axial force maintains intimate tric arc, and a high beam, respectively. ductivity and have a good ability for cast- contact between the parts and causes plas- However, in the nature of these tech- ing and machining. In order to take ad- tic deformation of the material near the niques, excessive heating can cause dam- vantage of the dissimilar metals involved, weld interface. If sufficient frictional heat age to the workpiece, including weakening has been produced during softening, and distortion. Some of the fusion tech- larger wear particles begin to expel from niques are applied for various materials the interfaces and axial shortening of the (Refs. 1–3). Low carbon (mild) steel and KEYWORDS components begin as a result of the ex- copper alloys are widely applied prospects pelled upsetting. In general, heat is con- because of their economic value, plus Friction Welding Mild Steel-Bronze ducted away from the interfaces, and a Welding Parameters plastic zone develops. The plasticized A. KURT is with Gazi University, Faculty of Tech- Mechanical Properties layer is formed on the interfaces and the nology, Ankara-Turkey. I. UYGUR (ilya- local stress system with the assistance of [email protected]) is with Duzce University, the rotary movement extrudes material Faculty of Engineering, Duzce, Turkey. U. PAY- from the interface into the flash. It has LASAN is with Korfez Vocational and Technical been shown that weld integrity is strongly High School, Kocaeli, Turkey. affected by the rate of flash expelled under 102-s MAY 2011, VOL. 90 Kurt et al Supplement May 2011:Layout 1 4/11/11 11:16 AM Page 103 A B Fig. 1 — Microstructure of A — AISI 1010 steel (× 500); B — ASTM B22 copper bronze (× 50). appropriate conditions (Ref. 9). Friction yield strength of the welded welding has a lot of advantages over other specimens were determined. welding processes, such as no melting, Hardness values (VH0.5) were high reproducibility, short production determined by using a Zwick time, low energy input, limited heat-af- 3212 device. Measurements fected zone (HAZ), avoidance of porosity were taken in the welding cen- formation and grain growth, and the use of ter through base metals. For nonshielding gases during the welding tensile strength and hardness process. Also, the technique is not only ap- test values, at least three speci- plied to round specimens but used for rec- mens were carried out for each tangular components. It is called linear parameter. The axial shorten- friction welding and has recently been ap- ing was estimated by measuring plied to steel (Ref. 10). the length of the specimens be- Although a large amount of previous fore and after welding. The mi- studies (Refs. 7–11) in similar and dissimi- crostructure was investigated Fig. 2 — The effect of upset time and friction pressure on the axial lar materials have been studied, mechanical by optical microscopy. The steel shortening with 22 MPa upset pressure. properties of the mild steel to copper specimens were polished and bronze joint by friction welding method etched with a solution consist- have never been reported up-to-date. Thus, ing of 70% HCl and 30% upset time and pressure on axial shortening the aim of this study is to examine the me- HNO3. The grains have equaxied shapes are also shown in Fig. 3. It is clearly seen that chanical properties and optimal welding ranging from 30 to 150 μm in dimension. axial shortening significantly increased with conditions of friction welded joints of The bronze specimens were also polished increasing friction, upset pressures, and ASTM B22 Tin bronze and AISI 1010. and etched with a solution consisting of times. To ensure good metallurgical in- 40% NH4OH, 60% H2O. Typical mi- tegrity, it is necessary to break up and expel Materials and Methods crostructures of materials can be seen in the contaminated surface layers. In rotary Fig. 1A, B. friction welding, this is achieved with WELDING RESEARCH Chemical composition of the copper- greater pressure and upset times. Also, in based bronze and mild steel employed is Results and Discussions light of these figures, the axial shortening given in Table 2. Cylindrical test specimens exponentially increased by increasing these of 20 mm in diameter and 100 mm in length Effects of Welding Parameters on Axial welding parameters. The fit of the results were prepared for friction welding. Before Shortening yields the following simple formula: friction welding, the surfaces facing each 0.22 other were machined using a lathe. Before The effect of upset time and friction As = 0.4 – 0.8 t (1) welding, the surface of the workpieces were pressure on the axial shortening is pre- cleaned with a stainless steel brush and ace- sented in Fig. 2. Similarly, the effects of where As is the axial shortening (mm) and tone to remove the oxide layer and stains. Joining of these two dissimilar alloys was performed on a continuous drive friction Table 1 — Some Physical and Mechanical Properties of Mild Steel and Copper Bronze welding machine of 250 kN capacity at a constant rotation speed of 2500 rev/min, Properties Unit AISI 1010 ASTM B22 and constant friction time of 3 s. Friction Density g/cc 7.87 8.72 and upset pressures can be observed on the Themal Conductivity W/m-K 51.9 74 screen, and the welding sequence stages are CTE μm/m-°C 12.2 20 controlled by a solenoid valve. The welding Ultimate Tensile Strength MPa 425 310 parameters were as follows: friction pres- Yield Strength MPa 180 150 sures (P1): 10, 15, 20 MPa; upset pressures Elongation % 28 25 (P2): 22, 25, 30 MPa; and upset (forging) Elastic Modulus GPa 200 105 time (t1) of 1, 5, 7, 8 s. Tensile test specimens Melting Temperature °C 1535 1000 were prepared according to ASTM E8M- Hardness Hv 100 83 00b.
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