低碳高强贝氏体钢二次焊接热循环过程组织转变与局部脆化  

Microstructural evolution and local brittlement of a low-carbon high-strength bainitic steel during double welding thermal cycle

作　　者：蒋庆梅[1] 张小强[1] 胡淑娥[2,3] 陈礼清[2] 孙卫华[3] 

机构地区：[1]中国石油天然气管道工程有限公司线路室,河北廊坊065000 [2]东北大学轧制技术及连轧自动化国家重点实验室,辽宁沈阳110819 [3]济南钢铁股份有限公司技术中心,山东济南250101

出　　处：《焊接技术》2015年第2期5-9,共5页Welding Technology

基　　金：国家科技支撑计划资助项目(2007BAE51B07)

摘　　要：采用焊接热模拟、低温冲击试验以及金相和扫描、透射电镜技术,研究了低碳高强贝氏体钢经历二次焊接热循环后的组织与韧性的变化规律。结果表明,经历不同峰值温度的二次热循环,组织类型没有发生变化,只是各种组织的形态、大小、数量以及原奥氏体晶粒大小有些差异。粗晶区的韧性呈现先升高后降低的趋势,当二次热循环峰值温度为1 000℃时韧性高于母材;试验钢不存在临界粗晶区局部脆化现象,但表现为亚临界粗晶区局部脆化,不均匀晶粒及粗大长链状的M-A组元存在是韧性下降的主要原因。通过二次焊接热循环可以有效改善一次热循环粗晶区的低温韧性。The microstructure evolution and low-temperature impact toughness of a 1 000 MPa grade low-carbon high-strength bainitic steel after double weld thermal cycle were investigated by using weld thermal simulation,low temperature impact test,metallographic observation,scanning and transmission electron microscopic analysis.The results showed that the microstructure type was no much change after double thermal cycle of different peak temperatures,but the shape and amount of each constituent in the microstructure and the original austenite grain size were different when the peak temperature of double thermal cycle was changed.The toughness of coarse-grained region first increased and then decreased,and the toughness was higher than the base metal when the peak temperature of double thermal cycle was 1 000 ℃.The experimental steel showed no local brittlement in the intercritically reheated coarse-grained HAZ,but a local brittlement appeared in subcritically reheated coarse-grained HAZ.This phenomenon was caused by the non-uniform grain size and chain-like coarse M-A constituents.The lowtemperature toughness of CGHAZ in first thermal circle could be effectively improved by the double thermal cycle.

关 键 词：低碳高强贝氏体钢 焊接热模拟 二次热循环 低温韧性 局部脆化 

分 类 号：TG406[金属学及工艺—焊接]