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用Y型坡口拘束抗裂试验方法评定了Mn-Mo-Nb型压力容器用低合金高强度钢SR裂纹敏感性。并用扫描电镜、X光结构分析、α粒子径迹照相等测试技术研究了微量硼对Mn-Mo-Nb钢SR裂纹敏感性的影响。微量硼明显增加Mn-Mo-Nb型钢的SR裂纹敏感性,其程度主要取决于碳硼化物在焊接热影响区粗晶晶界的析出形态和聚集行为,以及由此引起的热影响区的粗晶区高温蠕变延性的降低。这被含硼钢SR裂纹的独特形貌所证实。本文在探讨微量硼对Mn-Mo-Nb钢SR裂纹形成机制的基础上,提出控制“硼相”、防止SR裂纹产生的途径和措施。
The cracking susceptibility of low alloy high strength steel SR-Mn-Mo-Nb for pressure vessel was evaluated by Y-groove restrained crack resistance test method. The effects of boron on SR crack susceptibility of Mn-Mo-Nb steel were studied by scanning electron microscopy, X-ray structural analysis and α-particle track photography. The amount of boron significantly increases the SR crack sensitivity of Mn-Mo-Nb steel, which depends mainly on the precipitation morphology and aggregation behavior of the carbides in the coarse grain boundaries in the heat affected zone and the coarse heat affected zone Crystalline zone high temperature creep ductility reduction. This is confirmed by the unique morphology of cracked SR steel. Based on the discussion of the formation mechanism of SR crack in Mn-Mo-Nb steel by trace boron, the ways and measures of controlling “boron phase” and preventing SR crack are proposed in this paper.