Effects of post-weld heat treatments on the residual stress and mechanical properties of electron beam welded sae 4130 s
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Effects of Post-Weld Heat Treatments on the Residual Stress and Mechanical Properties of Electron Beam Welded SAE 4130 Steel Plates C.C. Huang, Y.C. Pan, and T.H. Chuang The distribution of the residual stresses of electron beam welded SAE 4130 and the effect of stress relief after various post-weld heat treatments (PWHT) were measured using X-ray diffraction. The mechanical properties and microstructure were also examined. Experimental results show that the tensile residual stress increased with the heat input of the electron beam. Most of the residual stresses were relieved by the PWHT at 530 ~ for 2 h followed by furnace cooling to 50 *C. The strength of the welds decreased slightly, and the elongation of the welds increased after PWHT.
Keywords electron beam welding, heat treatment, post-weld treatment, residual stress
1, Introduction ELECTRON BEAM welding (EBW) is a high-energy beam welding process. This process utilizes a very high-intensity beam as the power source for welding and has very high penetrating power that a conventional heat source cannot achieve. Because of the extremely concentrated heat source, EBW can produce welds much deeper and narrower than arc welds. In addition to a high depth-to-width ratio, low heat input and minimum distortion of the weld are advantages of EBW. During welding, thermal stresses occur due to local heating. Residual stresses in a single-pass weld are produced by the resistance of the metal plate to the contraction of the weld. Residual stresses and distortion result after welding and cause mismatching and cracking. In many cases, residual stresses don't cause cracking directly but promote fracturing through fatigue, hydrogen cracking, and stress corrosion. A thorough understanding of the magnitude and distribution of residual stresses can be used to increase the reliability of the structure. Therefore, measurement of residual stresses resulting from various welding parameters is important. Many methods are used to measure residual stresses, such as stress relief, x-ray diffraction (XRD), ultrasound, and the electromagnetic method (including Barkhausen). XRD is the most widely used nondestructive method. The principle is that when a metal is under stress, the resultant elastic strains cause the spacings of atomic planes in the metallic crystal structure to be changed (Ref 1). XRD can measure the interplanar atomic spacing, and from this quantity the stress can be evaluated. Three principal XRD techniques are used for stress measurement: the single-exposure technique, double-exposure technique, and sin 2 ~ method (Ref 2). The single-exposure technique requires at least two independent x-ray detectors that C.C. Huang and T.H. Chuang, Institute of Materials Science and Engineering, National Taiwan University, Taipei, Taiwan, R.O.C.; and Y.C. Pan, Chung Shan Institute of Science and Technology, Lungtan, Taoyuan, Taiwan, R.O.C.
Journal of Materials Engineering and Performance
can be operated simultaneously. The last two require repositioning of the stres
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