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对GCr15钢球阀经不同液氮保温时间和不同升温速度的深冷处理后的组织和力学性能进行了研究。结果表明:深冷处理可促使残留奥氏体转变为马氏体,细化组织并析出微细碳化物,提高GCr15钢球阀的综合力学性能。经深冷处理后残留奥氏体含量由16.74%降为0.40%~9.75%,表层残余应力由-98 MPa压应力变为252 MPa拉应力,耐磨性提高105%~146%,硬度提高1.70%~4.43%。液氮浸泡时间少于4 h时,随浸泡时间延长,磨损量减小、冲击吸收能量和硬度有所提高;超过4 h,随浸泡时间延长,磨损量和硬度变化不大,冲击吸收能量减小。此外,升温速度越快,硬度和磨损量均有提高,冲击吸收能量降低。当液氮保温时间约为4 h,深冷处理后的升温速度控制在0.5℃/min左右时,GCr15钢球阀残留奥氏体可控制在10%左右,获得良好的综合力学性能。
The microstructure and mechanical properties of GCr15 steel ball valve after cryogenic treatment with different liquid nitrogen holding time and different heating rate were studied. The results show that cryogenic treatment can promote the transformation of retained austenite into martensite, refine the microstructure and precipitate fine carbides, and improve the comprehensive mechanical properties of GCr15 steel ball valve. After cryogenic treatment, the retained austenite content decreased from 16.74% to 0.40% ~ 9.75%. The surface residual stress was changed from -98 MPa compressive stress to 252 MPa tensile stress, the wear resistance increased by 105% -146% and the hardness increased by 1.70% ~ 4.43%. When the immersion time of liquid nitrogen is less than 4 h, the wear loss decreases and the energy absorption and hardness increase with immersion time. When the immersion time is less than 4 h, the wear energy and hardness change little with the soaking time, and the impact energy absorbed small. In addition, the faster the heating rate, the higher the hardness and the wear amount, and the lower the impact absorption energy. When the holding time of liquid nitrogen is about 4 h and the heating rate after cryogenic treatment is controlled at about 0.5 ℃ / min, the residual austenite of GCr15 steel ball valve can be controlled at about 10%, obtaining good comprehensive mechanical properties.