模拟焊后热处理对 SA -738 Gr．B 钢板组织及韧性的影响

摘要

对比分析了调质处理（QT）及模拟焊后热处理（SPWHT）对SA-738Gr．B钢板力学性能及微观组织的影响。结果表明，SPWHT后钢板强度并未发生大的变化，但冲击韧性明显下降。主要原因在于，SPWHT后，钢中析出相由QT状态的小于20 nm的第二相粒子长大为100～400 nm的大尺寸含Cr的合金碳化物，从而引起晶界弱化，形成准解理断口，提高了韧脆性转变温度。%The effects of quenched -tempered ( QT ) and simulated post -welded heat treatment ( SP-WHT) on microstructure and impact properties of SA -738Gr.B steel plate were comparatively analyzed . The results show that the impact properties of steel plate are decreased significantly after SPWHT ,but the strength of steel plate is not changed obviously .The main reason is that the Cr -containing alloy carbide precipitates in the steel after SPWHT was increased to 100~400 nm,in contrast to the size of the second phase particles is smaller than 20 nm in the QT state,thereby which causes grain boundary weakening , generates a quasi cleavage fracture and increasing ductile -brittle transition temperature .