GCr15钢球阀的深冷处理

Cryogenic treatment of GCr15 steel ball valve

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。

Microstructure and mechanical properties of GCr15 steel ball valve which cryogenically treated by different liquid nitrogen holding time and different temperature rising rate were studied. The results show that cryogenic treatment can induce retained austenite to transform into martensite, refine the microstructure, precipitate fine carbides and improve the comprehensive mechanical properties of GCrl5 steel ball valve. After cryogenic treatment, the retained austenite content of the steel reduced from 16.74% to 0. 40%-9. 75% , surface residual stress changed from -98 MPa compressive stress to 252MPa tensile stress, wear resistance increased by 105%-146% and hardness increased by 1.70%-4.43%. When liquid nitrogen soaking time is less than 4 h, the wear rate was decreased with the soaking time extended, meanwhile, the impact absorption energy and hardness were increased. When soaking time is more than 4 h, the impact absorption energy was decreased with the extension of soaking time, while the wear rate and the hardness changed little. In addition, the hardness and wear rate were increased and impact absorption energy was decreased with the increase of temperature rising rate after liquid nitrogen soaking. The GCrl5 ball valve with about 10% retained austenite after the cryogenic treatment of about 4 h liquid nitrogen soaking and about 0.5 ℃/min temperature rising rate has excellent comprehensive mechanical properties.