厚壁管多道焊缝金属的局部微区蠕变性能试验研究

摘要

以高温耐热钢多道焊缝金属为对象，采用微试样方法进行了不同焊缝微区的蠕变试验，分析了蠕变破断试样断口、微观组织的关系。研究发现，焊缝金属局部微区的蠕变性能存在较大差异，表现为平行于焊道、垂直于焊道和焊道搭接区的蠕变强度依次降低，蠕变裂纹分别在粗晶区、柱状晶区和重结晶区萌生。局部微区组织差异主要影响蠕变一、二阶段的变形幅值，对变形规律没有显著影响。取样位置和方向分别导致试样包含的局部微区不同、相同外载下试样局部微区的应力不同，使多道焊缝金属表现出宏观各向异性蠕变行为。%Creep test with micro-specimens were conducted to study the properties of local zones in a heat resistant steel weld metal produced by multi-pass welding.The relationship between fracture morphology and microstructure of creep ruptured specimens was investigated.Results shown that different creep prop-erties can be clearly observed in local zones in multi-pass weld metal.The creep strength of specimen lo-cated in the weld pass parallel to welding direction has a maximum value,followed by that through multi-ple weld passes,and that located in the weld pass overlap perpendicular to welding direction.Meanwhile, the corresponding creep crack initiation sites are coarse grain zone,columnar grain zone and recrystallized grain zone,respectively.The above difference among local zones can induce the variation of the deforma-tion amplitude during primary and secondary creep stages,while it nearly has no effect on deformation law.The composition of specimen may be different as sampling location changes,while the applied stress on local zones may be different even for the same load when sampling direction changes.Both of them lead to macroscopic anisotropic creep behavior of multi-pass weld metal.