新型含氮奥氏体热作模具钢的研究

Research on a new nitrogen-bearing austenitic hot work die steel

对一种新型含氮奥氏体模具钢在不同工艺下进行热处理,并对试验钢的强韧性与热稳定性进行测试。利用DIL805A热膨胀相变仪测定膨胀系数,通过光学显微镜、高分辨扫描电子显微镜、X射线衍射仪及高分辨透射电子显微镜观察分析显微组织。结果表明:试验钢的最佳热处理工艺为1200℃固溶+720℃时效保温2 h,硬度达46 HRC,横向无缺口冲击试样冲击功达150 J;热稳定性良好,700℃保温20 h,硬度基本不变,780℃保温20 h后,硬度在44 HRC以上;钢中析出相主要为V(C、N),时效状态下析出相占钢中总量约4%,弥散析出强化相尺寸为10～20 nm。

A new nitrogen-bearing austenitic hot work die steel was processed by different heat treatments.Strength,toughness and heat stability of the steel were tested.The coefficient of expansion was analyzed by a DIL805A thermal dilatometer.The microstructure was observed and researched by means of OM,SEM,XRD and TEM.The results show that the optimum heat treatment for the test steel is aging at 720 ℃ for 2 h after solution treatment at 1200 ℃,and after the heat treatment,hardness of the steel is 46 HRC and the impact toughness of un-notched specimen reaches 150 J.The aged test steel performs good heat stability,and the hardness of the steel is unchanged at 700 ℃ for 20 h and reduced to 44 HRC at 780 ℃ for 20 h.The major precipitate is V（C,N） phase with the mass fraction of 4% in the steel after aging,and the size of the precipitates working as dispersion strengthening phase is 10-20 nanometers.