【摘要】 采用热模拟试验机,研究了一次及二次焊接热循环对X120管线钢的组织和性能的影响。结果表明:在一次焊接热循环时,X120管线钢具有良好的可焊性,当线能量为40kJ/cm时,焊接粗晶区仍保持高的冲击韧性和硬度。在双面焊时,峰值温度为1200℃的二次循环后,热影响区组织主要由板条马氏体和粒状贝氏体组成,因其奥氏体晶粒相对细小,从而具有良好的综合力学性能。当二次热循环峰值温度在奥氏体-铁素体两相区(800℃)和略高于两相区(1000℃)时,焊接热影响区表现为局部脆化。当峰值温度为800℃时,脆化原因是在晶界形成网状组织;而峰值温度为1000℃时,脆化原因是冷却时获得含有粗大M/A岛状组织的粒状贝氏体。更多还原

【Abstract】 The influence of once and twice welding thermal cycle on the microstructure and properties of the X120 pipeline steel was investigated by means of welding thermal simulation.The results show that a high weldability of the X120 pipeline steel can be exhibited after once welding thermal cycle.When the welding line energy is 40 kJ/cm,the high impact toughness and rigidity in the CGHAZ (coarse grain heat affected zone) can be obtained.During double-face welding,when the reheating peak temperature of twice welding thermal cycle is 1200 ℃,the microstructure of HAZ is composed of the lath martensite and granular bainite,and the austenite grain is refined,so the comprehensive mechanical properties at HAZ can be obtained.When the reheating peak temperature of twice welding thermal cycle is 800 ℃ which is at the α-γ two phase region,or 1000 ℃ which is higher than that at α-γ two phases region,local brittle zone can be found in the CGHAZ after twice welding thermal cycle.When the peak temperature is 800 ℃,the reason for the embrittlement of HAZ is the net microstructure formed in grain boundary.When the peak temperature is 1000 ℃,the embrittlement reason is the large M/A islands in granular bainite obtained during the cooling process.更多还原