焊接热输入对厚壁X80管线钢粗晶热影响区组织及性能的影响

摘要

In order to study the influence of welding heat input on microstructure and properties of X80 thick wall pipeline steel coarse grain heat affected zone, it adopted the thermal simulation technology to investigate and analyze the mechanical properties and microstructure of X80 pipeline steel. The results indicated that the microstructure of X80 pipeline steel coarse grain heat affected zone compose of lath bainitic, granular bainite and M-A. When the heat input is less than 25 kJ/mm, the coarse grain heat affected zone mainly compose of lath bainitic, the impact toughness is optimum, but the hardenability is moderate;when the heat input is greater than 25 kJ/mm,the coarse grain heat affected zone mainly compose of lath bainitic and granular bainite,the impact toughness is higher,and the hardness moderate;with the increase of heat input,the granular bainite of coarse grain heat affected zone becomes very bulky, at the same time, the form and distribution of M-A structure rapidly change,the serious softening appear in coarse grain heat affected zone,the impact toughness values dropped to the lowest.%为了研究焊接热输入对X80管线钢粗晶热影响区的组织及性能影响,采用热模拟技术,对不同焊接热输入下X80管线钢的力学性能与显微组织进行了研究和分析.研究结果表明,在不同热输入量下厚壁X80管线钢粗晶热影响区组织为板条贝氏体、粒状贝氏体及M-A岛组织.当热输入量小于25 kJ/mm时,粗晶热影响区组织以贝氏体板条为主,冲击韧性最佳,但硬度较高;当热输入量在25 kJ/mm时,试验钢粗晶热影响区组织为板条贝氏体与粒状贝氏体,冲击韧性较高,且硬度适中;随着热输入的增大,粗晶热影响区中的粒状贝氏体变得极为粗大,同时,M-A形态与分布发生急剧变化,粗晶热影响区出现严重软化,冲击韧性值明显下降.