一种中碳高强度合金钢的组织与性能研究

Study on Microstructure and Mechanical Properties of a Medium-carbon High-strength Alloy Steel

中碳高强度合金钢可用作分切高强度钢材的刀片。试制了一种含0.44%C、5.04%Cr、3.01%Mo、1.01%Ni、0.69%V和0.18%Nb(质量分数)的中碳合金钢,对其进行了球化退火、分别从975℃、1000℃、1025℃、1050℃和1075℃油淬及淬火后于200~600℃回火。检测了试验钢的热处理特性参数、不同工艺热处理后钢的显微组织和力学性能及拉伸与冲击试样的断口形貌。结果表明:适当增加Mo、Ni含量能进一步提高可用于制作高强度钢材分切刀片的中碳高强度合金钢的强韧性;试验钢淬火态组织为板条马氏体、少量未溶MC型碳化物和残留奥氏体,回火过程中会产生二次硬化效应,520℃回火的钢硬度最高;试验钢的最佳热处理工艺为900℃保温2 h随后730℃保温4 h球化退火,1025℃油淬随后520℃两次回火。

Medium-carbon high-strength ally steel may be used as a blade for cutting high-strength steel.A kind of medium-carbon alloy steel containing 0.44%C,5.04%Cr,3.01%Mo,1.01%Ni,0.69%V and 0.18%Nb by mass was trial-produced,and was spheroidized,quenched from 975,1000,1025,1050 and 1075℃in oil then tempered at temperatures ranging from 200 to 600℃,respectively.The investigated steel was tested for characteristic parameters for heat treating,the microstructure and mechanical properties after heat treating by different procedures,the fracture pattern of tensile and impact specimens.The results demonstrated that(a)increasing in molybdenum and nickel contents was capable of further raising strength and toughness of the medium-carbon high-strength alloy steel suitable for blade for cutting high-strength steel;(b)the investigated steel exhibited microstructure consisting of lath martensite,a small amount of undissolved carbides MC and retained austenite after quenching,secondary hardening effect during tempering,and maximum hardness after tempering at 200℃;and(c)the optimum heat treating processes for the investigated steel were spheroidizing consisting of holding at 900℃for 2 h followed by holding at 730℃for 4 h,and quenching from 1025℃in oil followed by double tempering at 520℃.