轧制工艺对铬钼系螺纹钢组织和性能的影响

Effect of rolling process on microstructure and properties of chrome-molybdenum steel rebar

为解决铬钼系螺纹钢轧制工艺参数设定问题,借助高温共聚焦显微镜、Gleeble热模拟试验机、金相显微镜、拉伸试验机及维氏硬度计等设备,结合小尺寸样品拉伸试验,研究了加热温度、变形温度、上冷床温度和冷速等轧制工艺参数对铬钼系螺纹钢组织和力学性能的影响。分析了试验钢过冷奥氏体连续冷却相变行为,测定了试验钢连续冷却转变(CCT)曲线,并在工业生产线上完成了直径20 mm的铬钼系螺纹钢试制。结果表明,试验钢过冷奥氏体连续冷却过程中,主要发生铁素体和贝氏体相变,随着冷速的增大,铁素体含量减少,贝氏体含量增大,硬度值增大;轧制工艺参数影响螺纹钢组织类型、晶粒大小及所占比例,进而影响螺纹钢的强度和塑性;当加热温度为1150~1200℃、变形温度为(1020±10)℃、上冷床温度为850~900℃、冷速为1℃/s时,试制钢筋的组织为铁素体+贝氏体,其中铁素体所占比例为48.56%,平均粒径为18.34μm,屈服强度大于430 MPa,抗拉强度大于630 MPa,断后伸长率大于20%,强塑积大于12 GPa·%。试验结果为铬钼系耐蚀钢筋的产业化提供了数据支撑。

In order to solve the problem of rolling process parameters setting of chrome-molybdenum steel rebar,the effects of heating temperature,deformation temperature,temperature on cooling bed and cooling rate on the microstructure and mechanical properties of chrome-molybdenum steel rebar were studied by high temperature confocal microscope,Gleeble thermal simulator,metallographic microscope,tensile testing machine,Vickers hardness tester and other equipment,and combined with small-size sample tensile test.The continuous cooling phase change behavior of test steel was analyzed,and the CCT(Continuous Cooling Transformation)curve of test steel was measured.The trial production of 20 mm diameter chrome-molybdenum steel rebar was completed in the industrial production line.The results show that,during the continuous cooling of test steel undercooled austenite,the ferrite and bainite phase transitions mainly occur.With the increase of cooling rate,the ferrite content decreases,while the bainite content increases,and the hardness increases.Rolling process parameters affect the structure type,grain size and proportion of steel rebar,and then affect the strength and plasticity of steel rebar.With heating temperature of 1150-1200℃,hot rolling temperature of(1020±10)℃,cold bed temperature of 850-900℃,and cooling rate of 1℃/s,the produced steel rebars exhibit a microstructure of ferrite and bainite,of which the proportion of ferrite is 48.56%,the average particle size is 18.34μm,and the yield strength is greater than 430 MPa,the tensile strength is greater than 630 MPa,the elongation after fracture is more than 20%,and the product of strength and elongation is greater than 12 GPa·%.The results provide data support for the industrialization of chrome-molybdenum corrosion resistant steel bar.