热循环对13MnNiMoR钢焊接热影响区显微组织和韧性的影响

Effects of Thermal Cycle on Microstructure and Toughness of HAZ of 13MnNiMoR Steel

通过系列焊接热模拟试验,研究了焊接热输入和焊接峰值温度对13MnNiMoR钢焊接热影响区显微组织和冲击韧性的影响。结果表明:随着焊接热输入的增加,试验钢粗晶热影响区(CGHAZ)组织中粒状贝氏体的含量增加,贝氏体铁素体板条尺寸增大,冲击韧性降低;随着焊接峰值温度的降低,热影响区的组织和韧性呈现明显变化,其中当峰值温度处于γ+α两相区(800℃)时,临界热影响区(ICHAZ)组织中形成多边形铁素体+大量的马氏体/奥氏体(M/A)组元,严重恶化了冲击韧性,成为整个热影响区中最薄弱的区域。

A group of welding thermal simulation tests for 13MnNiMoR steel were conducted to study the effects of welding heat input and peak temperature on the microstructure and impact toughness of the simulated heat affected zone （HAZ）. The results show that with the increase of heat input, the impact toughness and hardness of the coarse-grained heat affected zone （CGHAZ） decreased due to the increases both in the volume fraction of granular bainite and in the size of bainite laths; with the decrease of welding peak temperature, a significant change in the microstructure and toughness was observed. Particularly, when the peak temperature was in the α ＋ β intercritical region （800 ℃）, polygonal ferrite with a large amount of martensite/austenite （M/A） constituent formed in the intercritical heat affected zone （ICHAZ）. This microstructure led to poor impact toughness and made the ICHAZ become the weakest area in the HAZ.