焊后热处理对31CrMoV9钢电子束焊接接头组织及性能的影响

Effect of PWHT on microstructure and mechanical properties of electron beam welded joints of 31CrMoV9 steel

研究了31CrMoV9钢电子束焊接接头在焊后去应力退火、焊后调质两种不同焊后热处理状态下的焊缝组织与性能,并与同等强度等级下的母材组织与性能进行了对比研究。结果表明,接头焊后组织为板条马氏体及少量残留奥氏体;焊缝经调质处理后,组织为相对均匀的回火索氏体,接头力学性能与母材相当,相比于焊后去应力退火处理,焊缝冲击性能大幅提高。两种类型的焊后热处理均未消除焊缝柱状枝晶等凝固组织形态,但焊后调质工艺可减轻焊缝柱状枝晶组织偏析,并使之细化,使得焊缝与母材的组织与硬度更加均匀;焊后经多次重复淬火,焊缝经检测均未见裂纹,说明焊后采用调质工艺可行,这为提高焊缝冲击性能提供了可行工艺路线。

The microstructures and mechanical properties of 31 CrMoV9 steel electron beam welded joints with different post-weld heat treatment(PWHT),including stress relief annealing and quenching and tempering,were investigated and compared to the matrix with the same strength level.The results indicate that the microstructure of the electron beam welded joints is lath martensite and a small amount of retained austenite.After quenching and tempering treatment,the microstructure of the welded joint is relatively uniform tempered sorbite.And the mechanical properties of the joint are equivalent to that of the matrix.Compared with post-weld stress relief annealing treatment,the Charpy impact properties of the quenched and tempered welded joints are improved significantly.The two types of post-weld heat treatment cannot eliminate the solidification structure morphology such as columnar dendrites.The post-weld quenching and tempering process can reduce the segregation of the columnar dendrite structure of the weld and refine it,making the structure and hardness of the weld and the base metal are more uniform.No cracking is found in the electron beam welded joint,by several repeated quenching,which indicates that the post-weld quenching and tempering process is feasible.Therefore,PWHT provides a practical process route for improving the properties of the welded joint.