【摘要】 针对某火电厂超临界机组汽轮机1Cr5Mo钢制紧固螺母服役后硬度大幅下降现象,在566℃下对1Cr5Mo钢制螺母进行时效试验(等效于服役),研究了时效时间对显微组织和力学性能的影响,并与566℃下服役约105 h螺母的组织和性能进行了对比。结果表明:在不高于566℃的条件下,1Cr5Mo钢制螺母显微组织转变缓慢,时效2 880 h时的显微组织仍为马氏体和碳化物,但服役1 05 h时组织转变为回火索氏体;随着时效/服役时间的延长,碳化物由晶内向晶界处迁移富集,并发生明显粗化。组织的劣化导致螺母硬度、强度和冲击功降低。更多还原

【Abstract】 The hardness of the lCr5 Mo steel fastening nut of a supercritical unit steam turbine in a thermal power plant was reduced significantly after service.Aiming at this phenomenon,the aging tests(equivalent to service)of the 1 Cr5 Mo steel nut were carried out at 566℃.The effect of aging time on the microstructure and mechanical properties was studied,and the microstructure and performance were compared with those of the nut served at 566℃ for 10~5 h.The results show that at temperatures not higher than 566℃,the microstructure of the 1 Cr5 Mo steel nut changed slowly;the microstructure was still martensite and carbide after aging for 2 880 h.But the microstructure changed to tempered sorbite after service for 10~5 h.With the extension of the aging/service time,the carbides migrated and concentrated from the inside grain to the grain boundary,and became obviously coarsened.The deterioration of the structure led to the reduction of the hardness,strength,and impact energy of the nut.更多还原