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一、研制的缘起及目标我厂产品轻型大功率高速柴油机上的喷油嘴针阀体,过去一直采用18Cr2Ni4WA钢固体渗碳工艺制造。由于其工作条件较恶劣,头部工作温度高达250℃以上,因此使用后座面硬度下降较大,经测量其显微硬度由HV734～794下降到HV520～537,致使磨损加快,密封性破坏,寿命缩短。又由于该钢在250℃以上时处于回火过程第二阶段的残余奥氏体快速分解区,经用X光衍射法对其残余奥氏体定量分析,发现它含有的残余奥氏体,大量转变为回火马氏体(新机为18.7％,使用100小时后残余奥氏体下降为7％),因而引起体积膨胀,破坏了座面密封性,直至造成针阀卡死,处
First, the development of the origin and goal I plant products light high-power high-speed diesel injector nozzle needle body, the past has been using 18Cr2Ni4WA steel solid carburizing process. Because of its harsh working conditions, the head of the working temperature up to 250 ℃ or more, so after use seat surface hardness decreased significantly, the measured hardness decreased from HV734 ~ 794 to HV520 ~ 537, resulting in accelerated wear and tear, sealing damage, Shortened life expectancy. And because the steel at 250 ℃ above the tempering process in the second phase of rapid decomposition of retained austenite, by X-ray diffraction method for quantitative analysis of retained austenite and found it contains retained austenite, a large number Transformed into tempered martensite (18.7% for new machine, retained austenite decreased to 7% after 100 hours of use), causing volume expansion and destroying seat sealing until the needle valve becomes stuck