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20Cr Mn Ti H齿轮钢件在锻造后因奥氏体晶粒粗大,冷却后极易形成针状铁素体、网状铁素体和贝氏体等非平衡组织,影响后续的渗碳处理和切削加工。本文在实际工业生产条件下,研究了多步连续冷却等温正火对20Cr Mn Ti H钢锻坯显微组织及硬度的影响,研讨了这类钢中先共析铁素体的形态与形成条件以及控制方法。结果表明,采用适当的连续冷却等温正火工艺可精准控制这类钢中先共析铁素体形态,使得锻坯获得所要求的铁素体加珠光体组织,其晶粒大小可控制在4~6级,硬度在160~190 HBW范围之内。
Due to coarse austenite grains after 20Cr Mn Ti H gear steel forging, it is easy to form non-equilibrium structure such as acicular ferrite, reticular ferrite and bainite after cooling, which affects subsequent carburization and Cutting. In this paper, under the conditions of actual industrial production, the effect of multi-step continuous cooling isothermal normalizing on microstructure and hardness of 20Cr Mn Ti H steel was studied. The morphology and formation conditions of pro-eutectoid ferrite As well as control methods. The results show that the proper continuous cooling isothermal normalizing process can precisely control the pro-eutectoid ferrite morphology in this kind of steel so that the required ferrite plus pearlite structure can be obtained and the grain size can be controlled at 4 ~ 6, hardness in the range of 160 ~ 190 HBW.