对新型R5系泊链钢进行了950 ℃淬火及不同温度的回火处理,通过显微组织观察、拉伸和低温冲击试验、冲击断口形貌分析等方法研究了回火温度对R5系泊链钢显微组织与力学性能的影响.结果表明:R5系泊链钢经淬火及570～690 ℃区间回火后,显微组织均为回火索氏体,但组织中碳化物的大小、形貌和分布有所不同;经570～600 ℃回火后,组织中碳化物主要呈片状及长条状不均匀分布在原奥氏体晶界、马氏体板条界以及板条内部,组织保留马氏体位向,经630～690 ℃回火后,片状及长条状碳化物逐渐球化并长大,在组织中呈弥散均匀分布;随回火温度的升高,R5系泊链钢的强度逐渐减小,断后伸长率和冲击吸收能量逐渐增加;回火温度为630 ℃时,R5系泊链钢的抗拉强度为1 082 MPa,规定塑形延伸强度为973 MPa,断后伸长率为17.0%,冲击吸收能量为66 J,具有最佳综合力学性能.

A new type of R5 mooring chain steel was tempered at different temperature after being quenched at 950 ℃.Effects of tempering temperature on microstructure and mechanical properties of R5 mooring chain steel were investigated through microstructure observation,tensile and impact test and impact fracture analysis.The results show that the microstructure of R5 mooring chain steel after quenching and tempering at temperatures of 570-690 ℃ was tempering sorbite,but the size,morphology and distribution of carbides in the microstructure were different.When tempering temperature was in the range of 570-600 ℃,the flake and long strip carbides in the microstructure unevenly distributed on the grain boundaries of original austenite,martensite laths and in the inside of martensite laths,and the microstructure kept the direction of martensite.The flake and long strip carbides gradually became spherical and grew up when tempering temperature was in the range of 630-690 ℃.With the increase of tempering temperature the strength of R5 mooring chain steel decreased,but the elongation after fracture and impact absorption energy increased.When the tempering temperature was 630 ℃,the R5 mooring chain steel had optimum comprehensive mechanical properties,whose tensile strength reached 1 082 MPa,proof strength at plastic extension reached 973 MPa,elongation after fracture reached 17.0%,and impact absorption energy reached 66 J.