【摘要】 本文采用裂纹张开位移(COD)试验方法,对60公斤级高强钢(12Ni3CrMoV)的热模拟试样,单道焊和多道焊实焊试样,热影响区的断裂韧性和裂纹扩展阻力进行了详细的研究.研究表明,在12Ni3CrMoV钢的焊接热影响区中存在着粗晶区脆化和不完全相变区脆化.粗大的马氏体和焊接过程产生的粒状贝氏体是脆化的内在原因.热模拟试样能够反映热影响区中各种组织的相对韧性次序.在模拟粗晶区中,晶粒度的大小是影响裂纹扩展阻力的主要因素.热模拟粗晶区的断裂韧性最差,而多道焊粗晶区具有较好的韧性,这是因为多道焊的粗晶区中马氏体经过多次热循环回火所致.焊接热模拟试样能够反映热影响区中对应组织的韧性,但利用热模拟试样难以评定实际焊接接头中热影响区的裂纹扩展阻力.更多还原

【Abstract】 This paper, adopting the test method of crack opening displacement (COD), studies in detail the fracture toughness and the resistance of cracking growth of the thermal simulated specimens, and the single pass and multipass welding specimens of 12Ni3CrMoV steel. The results show that there is brittlement with the coarse-grained zone and the partly transformed zone in the welded HAZ of 12Ni3CrMoV steel. The large coarsened martensite and grainy bainite are the internal causes of brittlement. The thermal simulated specimens can reflect the relative toughness orders of varied microstructures in the welded HAZ. In the simulated coarse-grained zone, the grain size is the main factor affecting the resistance of crack growth. The fracture toughness .of the simulated coarsegrained zone is the lowest. The coarse-grained zone of the multipass welding has good toughness, it is because martensite in the coarse-grained zone of the multipass weld can withstand the tempering of many thermal eyclings. The welding thermal simulated specimens can reflect the toughness of corresponding microstructures in the welded HAZ. But it is difficult to evaluate the resistance of crack growth of the welded HAZ in the welded joints by using the thermal simulated specimens.更多还原