40Cr钢的强烈淬火+回火处理

采用CaCl₂水溶液对40Cr钢进行强烈淬火并高温回火，利用光学显微镜、扫描电镜、硬度计、冲击及拉伸试验机等，表征了显微组织、力学性能及断口形貌，并与常规调质工艺(油淬)进行了对比。结果表明，40Cr钢采用CaCl₂淬火介质进行强烈淬火+高温回火与常规调质处理相比，可获得细小均匀的回火索氏体组织；经强烈淬火+回火处理后，与常规调质相比，硬度提高8%～18%,强度提高3%～5%,冲击性能提高16%～30%,可满足其较高的服役性能要求。40Cr钢最优的调质工艺为850℃保温20 min后采用CaCl₂淬火介质进行强烈淬火，再经580℃回火120 min后空冷。

Intensive quenching and tempering of 40Cr steel

CaCl₂ aqueous solution was used as quenching medium to carry out intensive quenching process for the 40Cr steel, followed by high temperature tempering. The microstructure, mechanical properties and fracture morphologies were characterized by means of optical microscope, scanning electron microscope, hardness tester, impact and tensile tester, and compared with that of the oil quenching and tempering process. The results show that the fine and uniform tempered martensite can be obtained by intensive quenching with CaCl₂ quenching medium and high temperature tempering compared with oil quenching and tempering process. After intensive quenching and tempering, compared with conventional quenching and tempering process, the hardness is increased by 8%-18%, the strength is increased by 3%-5%, and the impact property is increased by 16%-30%, which can meet the requirements of higher service performance. The optimal quenching and tempering process for the 40Cr steel is austenitizing at 850 ℃ for 20 min, followed by intensive quenching with CaCl₂ quenching medium, and then tempering at 580 ℃ for 120 min plus air cooling.