Abstract: The microstructure and micro-hardness of typical non-quenched and tempered steel 38MnSiVS5 ( /% : 0. 37C,0. 78Si,0. 012P,0. 045S,0. 03Mo,0. 120V,0. 004Nb,0. 003Ti) are analyzed by using thermal dilatometer, optical microscope and Vickers hardness tester. The continuous cooling transformation ( CCT ) curves of supercooled austenite are tested. The results show that the CCT curve of steel 38MnSiVS5 could be divided into high temperature transition region, middle temperature transition region and low temperature transition region. With cooling rate ≤0.89 ℃/s, the high temperature transition region is formed with microstructure ferrite and pearlite; With the cooling rate 1.78 ～4.45 ℃/s, the high temperature transition region and middle temperature compound transition region is formed with microstructure ferrite, pearlite and bainite; as the cooling rate up to 8. 9 ℃/s, the high temperature transition region, middle temperature transition region and low temperature transition region are formed with microstructure ferrite, pearlite, bainite and martensite; as the cooling rate up to 17. 8 ℃/s, the F + P structure disappears,the middle temperature transition region and low temperature transition region are formed, the microstructure is bainite and martensite; as the cooling rate ≥44.5 ℃/s, the microstructure is martensite. With the increase of cooling rate from 0. 06 to 44. 5 ℃/s, the HV5 micro-hardness number of 38MnSiVS5 steel increased from 213 to 568.

摘要： 采用淬火膨胀仪、光学显微镜、维氏硬度计等研究了典型非调质钢38MnSiVS5(/%:0.37C,0.78Si,0.012P,0.045S,0.03Mo,0.120V,0.004Nb,0.003Ti)的显微组织和硬度。测定了其过冷奥氏体连续冷却转变(CCT)曲线。结果表明,38MnSiVS5钢的CCT曲线可分为高温转变区域、中温转变区域和低温转变区域。当冷却速度≤0.89℃/s时为全高温转变区,组织为铁素体和珠光体;当冷却速度为1.78～4.45℃/s时为高温、中温两相复合转变区,组织为铁素体、珠光体和贝氏体;当冷却速度为8.9℃/s时,为高温、中温、低温三相复合转变区,组织为铁素体、珠光体、贝氏体和马氏体;当冷却速度为17.8℃/s时,铁素体和珠光体消失,为中温、低温两相复合转变区,组织为贝氏体+马氏体;当冷却速度≥44.5℃/s时为马氏体转变区。随着冷却速度从0.06℃/s增大到44.5℃/s,38MnSiVS5钢的HV5显微硬度值由213增加至568。

关键词: 非调质钢, 38MnSiVS5,  ,  连续冷却相变,  ,  显微组织,  ,  显微硬度,  ,  CCT 曲线