异种钢窄间隙焊焊接接头两侧材料成分存在差异,在9%Cr侧熔合区内发生碳迁移现象。实际异种钢高温构件贫碳层内出现完全铁素体化组织,硬度极低,给焊接接头各项力学性能带来不良影响。设计不同焊道分布形式的异种钢堆焊试板,探究碳迁移程度及贫碳区内铁素体组织产生的影响因素。通过对不同热处理过程试样的金相观察发现,碳迁移主要在回火过程中产生。利用金相观察、显微硬度测试及电子探针成分测试等研究手段,比较焊道不同熔合比状态下的碳迁移现象。三层焊道堆焊试样的焊道交汇处碳迁移现象严重,在贫碳区内出现了完全铁素体化组织,硬度显著降低。电子探针测试结果表明,该位置母材熔合比较低,熔合线两侧铬元素质量分数差异明显导致碳元素活度梯度增加,因此碳迁移现象严重,对异种钢焊接接头的各项力学性能带来不良影响。
In the narrow gap welding joints of dissimilar steels, carbon migration happens due to the different components of dissimilar steels. Ferrite with low hardness is found in the carbon depleted zone of a real dissimilar welding high temperature component, which influences the mechanical properties of the welding joint. Bead-on-plate specimens with different weld bead configurations are designed to study the influence factors of carbon migration and the formation of ferrite in carbon-depleted zone. Carbon migration is found to happen during the temper process by metallographic observation. With the method of micro-hardness test and electron probe microanalysis, it is found that fusion ratio has a great influence on carbon migration. The specimen with three layers of welding beads suffers a severe carbon migration phenomenon, ferrite appears in the carbon-depleted zone, with a great decrease of micro-hardness. Electron probe microanalysis indicates that the multilayer intersection has a low fusion rate, the content of Cr across the fusion line is significantly different, which leads to a steep gradient of the activity of C. Carbon migration is severe at this area, which will have a deleterious effect on the mechanical properties of dissimilar welding joints.
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