调质工艺优化对ZG34CrNiMo钢组织和低温冲击性能的影响

Effect of quenching and tempering process optimization on microstructure and low temperature impact propery of ZG34CrNiMo steel

采用光学显微镜、扫描电镜和力学性能测试等方法研究调质工艺对ZG34CrNiMo钢U形试块心部显微组织、力学性能和冲击断口形貌的影响。结果表明,相比于常规调质工艺,ZG34CrNiMo钢经优化调质工艺(增加高温正火、提高淬火液冷速和高温回火快冷)处理后,淬火冷却过程U形试块心部组织充分完成马氏体转变,晶粒度等级由7.6级提升至8.3级,冲击试样断口形貌上观察到大量椭圆形韧窝,心部试样的-35℃低温冲击能量平均值由7.23 J提升至43.00 J。采用微量V或稀土元素改善钢材成分,心部试样综合力学性能进一步显著提升,尤其是-35℃低温冲击能量平均值达到77.00 J。

Effect of quenching and tempering process on microstructure,mechanical properties and impact fracture morphology of the core zone in U-shaped test block of ZG34CrNiMo steel was studied by means of optical microscope,scanning electron microscope and mechanical property test.The results indicate that compared to conventional quenching and tempering processes,when the ZG34CrNiMo steel is treated by optimized quenching and tempering process(high-temperature normalizing,higher cooling rate of quenching liquid and high-temperature tempering with fast cooling),the martensitic transformation can be fully completed in the core of the U-shaped specimen during quenching,the grain size is refined from grade 7.6 to 8.3,a large number of elliptical dimples appear in the impact fracture,and the average low-temperature impact absorbed energy at -35℃ is increased from 7.23 J to 43.00 J.By using trace amounts of vanadium or rare earth elements to improve the composition of the steel,the comprehensive mechanical properties of the core zone specimen are further improved significantly,especially with average low-temperature impact absorbed energy of 77.00 J at -35℃.