回火温度对30Cr3Si2NiMoWNb钢组织性能的影响

Effect of tempering temperature on microstructure and properties of 30Cr3Si2NiMoWNb steel

采用扫描电镜、能谱分析和力学试验等研究了回火温度对30Cr3Si2NiMoWNb超高强度钢组织和性能的影响。结果表明,回火温度变化可实现对力学性能的大幅度调控。200~350℃回火,微观组织为回火马氏体与细小弥散的ε-碳化物,此阶段强韧性变化幅度较小,抗拉强度等级1700 MPa、屈服强度等级1300 MPa;350~500℃回火由于渗碳体的不均匀析出,强度和韧性同时下降,其中500℃左右回火脆性最为严重,冲击吸收能量下降至最低点;500~700℃回火生成较稳定的球状渗碳体,强度大幅下降,韧性大幅上升。回火温度对强韧性的影响机理为ε-碳化物、渗碳体等析出相演变过程的影响;一定含量的Si元素可以提高渗碳体形成温度和回火脆性温度。

Effect of tempering temperature on microstructure and properties of 30Cr3Si2NiMoWNb ultra-high strength steel was studied by means of scanning electron microscopy(SEM),energy dispersive spectrometer(EDS)and mechanical test.The resules show that the tempering temperature can greatly affect and regulate the mechanical properties of the steel.When tempered at 200-350℃,the microstructure is composed of tempered martensite and fine dispersed ε-carbides.The fluctuation of strength and toughness is small,the tensile strength grade is 1700 MPa,the yield strength grade is 1300 MPa.Due to the inhomogeneous precipitation of cementite when tempered at 350-500℃,the strength and toughness decrease at the same time,and the brittleness is the most serious at about 500℃,with impact absorbed energy decreasing to the lowest point.When tempered at 500-700℃,stable spherical cementite is formed,and strength decreases and toughness increases greatly.The influence mechanism of tempering temperature on strength and toughness is the evolution process of precipitates such as ε-carbide and cementite.Certain amount of Si can raise the forming temperature of cementite and temper brittleness temperature of the steel.