焊后热处理对SIMP钢瞬时液相扩散连接接头组织与力学性能的影响

Effect of Postweld Heat Treatment on Microstructure and Mechanical Properties of SIMP Steel Joint by Transient Liquid Phase Diffusion Bonding

在不同等温凝固工艺参数下对SIMP钢管进行瞬时液相扩散连接,并进行1060℃×4 min原位正火+(780±3)℃×120 min回火处理,对比研究了热处理前后接头的显微组织和力学性能。结果表明:接头热影响区组织由粗大马氏体和残余奥氏体组成,焊后热处理后马氏体转变为细小均匀的回火马氏体;焊后热处理后焊缝界面由直线状变成曲线状,界面结合面积增加;焊后热处理后,接头的抗拉强度和显微硬度均略有降低,但抗拉强度仍在700 MPa以上,冲击吸收能量由不高于9.4 J提高到40 J以上,拉伸断裂形式由脆性断裂向韧性断裂转变,综合力学性能较好。

SIMP steel tubes were subjected to transient liquid phase(TLP)diffusion bonding with different isothermal solidification parameters,and then subjected to 1060℃×4 min in-situ normalizing and(780±3)℃×120 min tempering treatment.The microstructure and mechanical properties of the joints before and after heat treatment were studied and compared.The results show that the microstructure of the heat-affected zone of the joint consisted of coarse martensite and retained austenite,and the martensite transformed into fine and uniform tempered martensite after postweld heat treatment.The weld interface changed from a straight line to a curved line after postweld heat treatment,and the interface bonding area increased.After the postweld heat treatment,the tensile strength and microhardness of the joint were slightly reduced,but the tensile strength was still above 700 MPa;the impact absorption energy increased from no more than 9.4 J to more than 40 J;the form of tensile fracture changed from brittle fracture to ductile fracture.The joint after heat treatment had relatively good comprehensive mechanical properties.