异种钢焊接接头失效机制的研究进展

由于异种钢理化特性的差异，在焊接过程中导致焊接接头的界面分布和裂纹失效机理与同种钢有所不同。文中从异种钢焊接接头的失效机制入手，介绍碳迁移导致熔合区出现软化和脆化现象，分析在焊接过程中导致其力学性能降低的本质原因，详细解释Type-II晶界和“白亮层”的形成机理，分析在高应力水平下异种钢焊接裂纹的形成机理和抑制措施。通过对异种钢焊接接头失效的本质原因进行系统性论述，为异种钢焊接失效机制的深入研究和工程应用提供理论指导，并提出针对异种钢焊接接头常见失效问题的解决方案。创新点： (1)从焊缝过渡区域的特性着手，分析异种钢焊接接头失效机制的研究进展，提出抑制过渡区域中Type-II晶界的形成、缩小“白亮层”的宽度是提高焊接接头性能的关键措施。通过整理前人对异种钢焊接过程中的碳迁移过程的定量研究，明确了由于碳迁移造成的异种钢焊接接头软化和脆化机理。(2)提出基于精确施加冷源从而定量控制焊接热应力和残余应力的分布情况，是可能改善异种钢焊接裂纹失效问题的有效措施。

Research and progress on failure mechanism of dissimilar steel welded joints

Due to differences in physical and chemical properties of dissimilar steels, interface distribution and crack failure mechanism of welded joints are different from those of the same steel during welding. Starting from failure mechanism of dissimilar steel welded joints, softening and embrittlement phenomenon of fusion zone caused by carbon migration were introduced in this paper, the essential reason for the decrease of mechanical properties in welding process was analyzed, formation mechanism of Type-II grain boundary and white bright layer was explained in detail, and formation mechanism and suppression measures of dissimilar steel welded cracks under high stress level were analyzed. The essential reasons for failure of dissimilar steel welded joints were systematically discussed, which provided theoretical guidance for in-depth study and engineering application of failure mechanism of dissimilar steel welded joints, and put forward solutions to common failure problems of dissimilar steel welded joints.Highlights: (1) Based on characteristics of weld transition zone, research progress of failure mechanism of dissimilar steel welded joints was analyzed. It was proposed that key measures to improve performance of welded joints were to inhibit formation of Type-II grain boundary in transition zone and reduce width of white bright layer. Mechanism of softening and embrittlement of dissimilar steel welded joints caused by carbon migration was clarified by discussing carbon migration in dissimilar steel welding.(2) It was proposed that quantitative control of distribution of welding thermal stress and residual stress based on precise application of cold source was an effective measure to improve welding crack failure of dissimilar steels.