17CrNiMo6高强度渗碳齿轮钢大型锻件的研制

Development of 17CrNiMo6 heavy forgings of high strength carburized gear steel

针对17CrNiMo6钢大型锻件端淬试验硬度值无法满足技术要求的情况,通过优化材料化学成分设计,制定合理的冶炼、模铸、锻造、热处理工艺,成功开发出20 t级起重机用高强度渗碳钢17CrNiMo6卷筒大齿轮锻件。通过化学成分分析、低倍和夹杂物检验、机械性能及末端淬透性试验,分析了17CrNiMo6钢锻件的特性。结果表明:研制的锻件在正火+高温回火后显微组织为均匀的回火索氏体和少量铁素体,无明显的带状组织和混晶出现;奥氏体晶粒度评级为8.0级,带状组织评级为0级,金相组织评级为2.0级。机械性能指标满足技术要求且富有一定的余量,端淬试验表明,从距离淬火端15 mm以内,硬度值变化很小,15～40 mm内硬度值逐渐减小,但下降幅度不大,两端硬度的最大差值为5 HRC,材料具有非常优良的淬透性。

Aiming at the situation that the hardness value of Jominy test of 17 CrNiMo6 large forgings cannot meet the technical requirements,the 17 CrNiMo6 large gear forgings of high strength carburized steel for 20 t crane have been successfully developed by optimizing the design of chemical composition of materials and formulating reasonable smelting,casting,forging and heat treatment processes.The characteristics of 17 CrNiMo6 steel forgings were analyzed by chemical composition analysis,low-power and inclusion test,mechanical properties and Jominy test.The results showed that the microstructure of the forgings was uniform temper sorbite and a small amount of ferrite after normalizing and tempering at high temperature.The austenite grain size rating was 8.0,the banded structure rating was 0,and the metallographic structure rating was 2.0.The mechanical performance index met the technical requirements and had a certain margin.The Jominy test showed that the hardness value changed very little within 15 mm from the quenching end,and gradually decreased within 15-40 mm range,but the decrease range was not large.The maximum difference between the hardness of both ends was 5 HRC,and the material had a very good hardenability.