Micro-Shear Properties of Welded Joints of ASTM4130 Steel

The effect of soaking time and temperature of post weld heat treatment on the micro-properties of the welded joints of ASTM4130 steel was investigated by using micro-shear test. The results show that micro-shear test can be adopted to evaluate the mechanical properties of uneven materials such as the welded joint. The micro-strength of the weld, fusion line and base metal is not obviously affected by the soaking time. The width and strength loss of the softened zone slightly decrease with increasing soaking time. The micro-shear strength of the weld firstly decreases and then significantly increases with increasing PWHT temperature. But the BM shows the opposite trend. The width and strength loss of the softened zone are not obviously affected by PWHT temperature. At PWHT temperature of 590 °C, the width of softened zone and the strength loss rate are the largest. In terms of hardness, width and degree of the softened and toughness, 640°C/165min PWHT is preferred.

Effect of Postweld Heat Treatment on Toughness of the Heat Affected Zone in ASTM4130 Steel with Single-Pass Welding

The effect of postweld heat treatment (PWHT) on microstructure and properties of the heat affected zone (HAZ) in ASTM4130 steel fabricated by single-pass welding was investigated by weld thermal simulation test, optical microscope, transmission electron microscopy and scanning electron microscope. The results show that the subcritical HAZ (SCHAZ) toughness slightly decreases due to the aggregation and growth of carbides. Other HAZ toughness is significantly improved showing that the 650°C/1.5h PWHT is effective. The toughness improvement of the fine-grained HAZ (FGHAZ) and the intercritical HAZ (ICHAZ) is chiefly resulted from the complete decomposition of martensite and M-A constituent. Meanwhile, the supersaturation reduction of non-equilibrium microstructure and the relief of residual stress effectively improve CGHAZ toughness.