焊丝成分对T91/316L异种钢焊接接头微观组织和力学性能的影响

Effect of Welding Wires on Microstructures and Mechanical Properties of T91/316L Dissimilar Welding Joints

T91马氏体钢与316L奥氏体钢异种钢的焊接主要应用于超超临界机组(USC)和核电领域中的加速器驱动次临界洁净核能系统(ADS)。本研究采用ER309L、ER316L和ERNiCr-3三种不同的焊丝,使用钨极氩弧(TIG)焊对T91马氏体不锈钢和316L奥氏体不锈钢进行了焊接,并对焊接接头进行了微观组织和力学性能分析,同时研究了焊后热处理对焊接接头的影响规律。研究结果表明,使用三种焊丝获得的焊缝的微观组织都是粗大的奥氏体枝晶,且其枝晶的晶粒垂直于熔合线往焊缝中心生长。焊态下焊接接头拉伸试样在T91侧的粗晶热影响区(CGHAZ)发生脆性断裂,经过焊后热处理(750℃/1h)的焊接拉伸试样的韧性断裂均发生在316L母材处,且抗拉强度显著上升,这表明焊后热处理能够提高T91/316L异种钢焊接接头的拉伸性能。在未焊后热处理状态下,使用ERNiCr-3焊丝获得的焊接接头焊缝的冲击性能优于其他焊丝。焊态下焊接接头硬度在T91侧熔合线处显著升高,而焊后热处理后T91侧熔合线处的硬度凸起几乎消失。

Dissimilar welding between T91 martensitic steel and 316L austenitic stainless steel is typically used in ultra-supercritical(USC)boilers for power plants and in the accelerator driven systems(ADS)for nuclear industry.This paper investigated the microstructure and mechanical properties of T91/316L tungsten inert gas(TIG)welding joints fabricated by three different kinds of welding wires(ER309L,ER316L and ERNiCr-3).The microstructure of three welding joints were all coarse dendritic austenitic grains with the orientation perpendicular to the fusion line.Before post welding heat treatment(PWHT),the fracture of tensile specimens all took place in T91 side CGHAZ due to the formation of the coarse grains at T91 side CGHAZ in the process of welding thermal cycle.However,after PWHT(750℃/1 h),the fracture locations of tensile specimens shifted to the 316L base metal and the tensile strength increased obviously,indicating that PWHT was necessary for the enhancement of the tensile strength of T91/316L dissimilar welding joints.The impact toughness of ERNiCr-3 welding seam was better than ER309L and ER316L welding seams in as-welded condition.The hardness of all samples in the as-welded condition exhibited an obvious increase in the fusion zone at T91 side,while the bump disappeared after PWHT.