马氏体焊缝组织对T91/P91钢焊接冷裂纹敏感性的影响

Effect of Martensite Weld Microstructure on Welding Cold Crack Sensitivity of T91/P91 Steel

综述了马氏体焊缝对T91/P91钢焊接冷裂纹敏感性的影响,包括焊缝组织、扩散氢行为和接头拘束力。结果表明,T91/P91钢焊后状态的焊缝组织为板条马氏体+残余奥氏体+δ铁素体,焊缝组织的形成取决于"准成分匹配"焊缝金属的化学成分,在铁研试件中出现的启裂于根部应力集中处,以短段串接、二次裂纹、穿晶开裂方式为特征的裂纹属于氢致冷裂纹;马氏体焊缝组织对T91/P91钢冷裂纹敏感性影响,除了马氏体自身特性之外,主要取决于焊缝中扩散氢的行为和接头拘束应力的作用。因此,工程上常用焊缝中残留扩散氢最小化、不足以引发氢致冷裂纹的"焊缝金属低氢化"综合工艺来控制T91/P91钢焊接冷裂纹,并获得了满意的效果。

The effect of martensitic weld on the cold crack sensitivity of T91/P91 steel was reviewed,including weld microstructure,hydrogen diffusion behavior and joint restraint force.The results show that the weld microstructure of T91/P91 steel after welding is lath martensite+retained austenite+δferrite.The formation of weld microstructure depends on the chemical composition of"quasi composition matching"weld metal.The cracks generated in tekken specimens,which originate from the stress concentration at the root,have the characteristics of short-segment series connection,secondary cracks and transgranular cracks,the natures of the cracks are hydrogen-induced cold cracks.The influence of martensite weld microstructure on cold crack sensitivity of T91/P91 steel mainly depends on the behavior of diffusing hydrogen in the weld and the effect of restraint stress of welded joints in addition to the quality characteristics of martensite itself.The comprehensive process of low hydrogenation with minimizing residual diffusive hydrogen in the weld metal and insufficient to cause hydrogen-induced cool cracks are often used in engineering,and have achieved satisfactory results.