22CrNi3Mo超高强钢的直接热处理工艺试验

Direct heat treatment process experiment of 22CrNi3Mo ultra high strength steel

凿岩机械用钢需具有高强度、高耐磨性及抗疲劳特性,通常通过热加工和热处理工艺改善其性能,但是工艺流程长、能耗较高。通过热轧试验研究了840-900℃之间不同终轧温度以及轧后空冷、空冷-炉冷两种冷却方式对22CrNi3Mo钢组织和性能的影响,探索了一种新型的直接热处理工艺。结果表明,轧后空冷至室温时,组织为板条贝氏体＋马氏体,降低终轧温度可使组织细化,强度提高;轧后空冷-炉冷时,组织为板条贝氏体、粒状贝氏体及沿奥氏体晶界分布的残留奥氏体,且块状残留奥氏体体积分数随终轧温度的降低呈现先增加后减小的趋势,而尖角状M/A岛的出现使得应力集中,引起韧性的下降,降低空冷终止温度可显著减小块状残留奥氏体体积分数,使得材料强度、韧性明显提高,力学性能接近传统工艺。

Steel for drilling machineries need to have high strength,higher wear resistance and fatigue resistance. Hot working and heat treatment is usually used to improve the steel properties but with a long process and high energy consumption. A new direct heat treatment process was explored. The influence of different finishing rolling temperature（ 840-900 ℃） and cooling processes（ air cooling after rolling,air cooling and furnace cooling after rolling） on the microstructure and properties of 22CrNi3Mo steel by hot rolling mill were studied. The results show that by the process of air cooling to room temperature,the microstructure of the steel is mainly composed of lath bainite and martensite,and the decrease of finishing rolling temperature results in the microstructure refined and strength increased; by the process of air cooling and furnace cooling after rolling,the microstructure is constituted by lath bainite,granular bainite and retained austenite distributed along the austenite grain boundaries. Furthermore,the volume of blocky retained austenite can tend firstly to increase and then decrease with the reducing of finishing rolling temperature,but the presence of sharp M / A islands brings about stress concentration,which leads to the decrease of toughness. For the volume fraction of blocky retained austenite can drop significantly when reducing the finish cooling temperature of the air cooling process,the strength and toughness can increase remarkably,as the mechanical properties is close to that by traditional process.