热处理工艺对30Cr16Mo1VN钢组织和性能的影响

为探索30Cr16Mo1VN钢最佳的热处理工艺,采用冲击、拉伸试验机、洛氏硬度计、OM、SEM、XRD、TEM研究了淬、回火温度对该钢组织和力学性能的影响。结果表明:该钢最佳的淬火温度为1050 ℃,淬火后存在少量M₂₃C₆碳化物和M₂N氮化物阻碍晶界迁移,其平均晶粒尺寸为14.1 μm,而大部分碳/氮化物固溶进基体中,导致Ms点降低,残留奥氏体含量增至59.2%。经-73 ℃冷处理后,大量残留奥氏体转变成马氏体,硬度提高至57 HRC。该钢300 ℃回火时具有良好的强韧性匹配,抗拉强度达2030 MPa,断面收缩率为10.0%。回火后基体发生回复,位错密度降低,随回火温度的升高,基体上析出细小弥散的球状碳化物阻碍位错运动产生二次硬化,450 ℃回火时出现硬度峰值。回火温度低于500 ℃时,该钢的硬度值皆大于55 HRC,具有良好的回火稳定性。

Effect of heat treatment on microstructure and properties of 30Cr16Mo1VN steel

In order to explore optimum heat treatment process of 30Cr16Mo1VN steel, the effect of quenching and tempering temperatures on the microstructure and mechanical properties was studied by impact and tensile tests, Rockwell hardness test, OM, SEM, XRD and TEM. The results show that the optimum austenitizing temperature for quenching of the steel is 1050 ℃, at which there are a small amount of M₂₃C₆ carbide and M₂N nitride to hinder the grain boundary migration in quenching, and the average grain size of prior austenite is 14.1 μm. However, most of the carbide and nitride are dissolved into the matrix, resulting in lowering of the Ms point and increasing the content of retained austenite up to 59.2%. After cryogenic treatment at -73 ℃, a large amount of retained austenite is quenched into martensite, and the hardness of the steel is increased to 57 HRC. After tempering at 300 ℃, the steel has a good match of strength and toughness, with the tensile strength and the area reduction up to 2030 MPa and 10.0% respectively. The tempering leads the matrix to recover and the dislocation density to decrease, while as the tempering temperature rises, the dispersed fine spherical carbide precipitates in the matrix to hinder the movement of dislocations and produce secondary hardening, and the hardness peak appears when tempering at 450 ℃. When the tempering temperature is lower than 500 ℃, the hardness is always greater than 55 HRC, the steel has good tempering resistance.