热输入对贝氏体海工钢焊接热影响区显微组织与低温韧性的影响

Effect of Heat Input on Microstructure and Low Temperature Toughness of Welding HAZ of Bainitic Offshore Steel

采用Gleeble-3800热模拟试验机研究了690MPa低裂纹敏感性贝氏体海工钢不同热输入焊接热影响区粗晶区(coarse grain high affected zone,CGHAZ)组织及低温韧性。结果表明:随着热输入的增加,试验钢CGHAZ中组织类型由马氏体/贝氏体向贝氏体/粒状贝氏体转变,M/A数量增多尺寸变大,低温韧性先升高后降低,当热输入30KJ/cm时韧性最好;当焊接热输入50KJ/cm时,M/A组元变粗大,粒状贝氏体出现以及原奥氏体晶粒度变大,大角度晶界密度下降,从而导致低温韧性恶化。

The microstructure and low temperature toughness of coarse grain high affected zone(CGHAZ)with different heat input of 690MPa low-crack sensitive bainite marine steel were studied by Gleeble3800 thermal simulation tester.The results show that with the increase of heat input,the microstructure of CGHAZ changes from martensite/bainite to bainite/granular bainite,the number of M/A increases,the size becomes larger,the low temperature toughness rises before the 30KJ/cm heat input and then falls.When the heat input up to 50 KJ/cm,the M/A component and the grain size of the austenite coarsens,the granular bainite appears and the grain boundary density decreases at large angle,which leads to the deterioration of low temperature toughness.