1000MPa级超高强钢的SH-CCT曲线及其热影响区的组织和性能  

SH-CCT Diagram,Microstructures and Properties of Heat-Affected Zone in a 1 000MPa Grade Extra High-Strength Steel

作　　者：蒋庆梅[1] 张小强[1] 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：《钢铁研究学报》2014年第1期47-51,共5页Journal of Iron and Steel Research

基　　金：国家科技支撑计划资助项目(2007BAE51B07)

摘　　要：采用热膨胀法结合显微金相与硬度检测,在热模拟试验机上测定了1 000MPa级低碳微合金高强钢焊接过程中的临界点Ac1和Ac3,绘制出该钢在不同冷却速率下的焊接连续冷却转变曲线(SH-CCT曲线),研究了冷却速率对焊接热影响区粗晶区(CGHAZ)组织和硬度的影响规律,揭示了不同冷却速率下焊接热影响区的相变过程及组织特征,同时获得了奥氏体晶粒平均尺寸随t8/5的变化关系。研究结果表明,在焊接条件下,该钢的奥氏体化温度要比平衡状态下的奥氏体化温度显著升高;该钢在相当宽的冷却速率范围内发生中温转变,获得贝氏体组织;在较快的冷却速率(≥40℃/s)下,焊接热影响区组织以马氏体为主;随着冷却时间t8/5的增加,硬度逐渐下降,最高硬度HV10为425。在试验条件下,奥氏体晶粒粗化程度并不显著。By using thermal expansion measurement combined with microscopic analysis and hardness test, the crit- ical points At1 and At3 of 1000MPa grade low carbon micro-alloyed extra high-strength steel in the welding process were determined and SH-CCT diagram at different cooling rates was obtained. The influence of cooling rate on microstructure and hardness of CGHAZ was investigated to reveal the phase transition of HAZ at different cooling rates and the relationship between average austenite grain size and ts/5 during simulated thermal circle. The results indicate that the austenitizing temperature of this steel in the welded condition is significantly higher than that in the equilibrium state. Intermediate temperature phase transformation to bainite can occur in a wide range of cooling rates. The microstructure of HAZ is mainly consisted of martensite at rapid cooling rate （≥40 ℃/s）. The hardness decreases gradually with the increase of t8/5 and the maximum hardness is 425 （HV10）. The coarsening degree of austenite grain size is insignificant on the testing condition.

关 键 词：1000MPa级超高强钢 焊接热影响区 SH—CCT曲线 硬度 晶粒尺寸 

分 类 号：TG401[金属学及工艺—焊接]