【摘要】 管线钢在多道焊的２次热循环下形成的临界粗晶区是受焊区的韧性谷区。引起临界粗晶区局部脆化的主要原因，是在多道焊２次热循环的特定热过程中所形成的粗大、富碳的Ｍ—Ａ组元和表现出来的组织遗传现象。采用预备回火焊道处理可消除组织遗传现象；采用补充国火焊道处理可细化Ｍ—Ａ组元，从而消除临界粗晶区局部脆化。更多还原

【Abstract】 The relationship between microstructure and toughness of the welding heat-affected zone (HAZ) of a pipeline steel is investigated by means of thermal simulation test and transmission electron microscope (TEM). It is found that the intercritically reheated coars-grained heat-affected zone (IRCGHAZ) of experimental steel has the lowest toughness when the second peak temperature is at (α+γ) region during multi-pass welding. This local embrittlement is mainly attributed to the morphology, amount and size of M-A constituent. It is also found that the microstructure inhabitance at IRCGHAZ has a deleterious effect on the toughness. On the basis of above experimental results, it is suggested that the local embrittlement should be prevented by using pre-heating cycle, which could eliminate the microstructure inhabitance, and using temper-heat- ing cycle which could improve the morphology, amount and size of M-A constituent.更多还原