复合形变热处理对38MnVS钢组织及性能的影响

Effect of composite thermomechanical treatment on microstructure and properties of 38MnVS steel

利用热变形与温变形相结合的复合形变热处理工艺对38MnVS非调质钢进行了处理,借助光学显微镜、扫描电镜、能谱仪、拉伸试验机、摆锤冲击试验机及显微硬度仪等对其组织结构及力学性能进行了表征。结果表明,当复合形变热处理工艺为1150~1200℃热变形（25%变形量）＋650℃温变形（15%变形量）时,能够显著改善其组织结构,并有效增加珠光体团位错密度及形变强化效应,其显微组织主要为珠光体和沿晶界或晶内分布的均匀细小铁素体,抗拉强度、屈服强度和冲击吸收功（25℃）分别为935.8 MPa、625.5 MPa和11.8 J,相对于传统的控锻控冷工艺分别提升9.4%,12.5%和61.6%,且试样冲击断口具有解理断裂和微孔聚集型断裂混合特征。

38MnVS steel was treated by composite thermomechanical treatment combined with hot deformation and warm deformation processes. Microstructure and mechanical properties of the steel were investigated by optical microscope（ OM）,scanning electron microscopy（ SEM）,energy disperse spectroscopy（ EDS） analysis,electron tensile testing machine,pendulum impact testing machine and microhardness tester. The results show that the microstructure is composed of pearlite and uniform fine ferrite grown along the grain boundaries or within the crystal,and the dislocation density and strain strengthening of the steel obviously increase by the composite process of 25% hot deformation at 1150-1200 ℃ and 15% warm deformation at 650 ℃. Comparing with the traditional controlled forging and cooling process,the tensile strength,yield strength and the impact absorption energy（ 25 ℃） of the steel treated by the composite process are improved by 9. 4%,12. 5% and 61. 6%, which are 935. 8 MPa,625. 5 MPa and 11. 8 J, respectively, and the characteristics of impact fracture are cleavage fracture and micro pore aggregation fracture.