控轧控冷和回火工艺对超低碳贝氏体钢组织和性能的影响

Effects of controlled rolling,controlled cooling and tempering process on microstructure and properties of ULCB steel

研究超低碳贝氏体钢的控轧控冷和回火工艺对其组织及力学性能的影响。结果表明,在试验工艺下试样组织均为粒状贝氏体,且在820℃终轧、440℃回火时获得了高强度低屈强比的超低碳贝氏体钢;控轧控冷工艺可以细化贝氏体铁素体和M-A岛、降低铁素体含碳量、控制组织中软硬相的比例,从而提高材料强度、降低其屈强比。回火温度升高使贝氏体铁素体粗化、含碳量和位错密度降低、M-A岛分解成细小的板条贝氏体,并析出富铜原子团,这是材料获得高强度、低屈强比的主导因素。

The effects of controlled rolling,controlled cooling and tempering process on the microstructure and properties of ultralow carbon bainitic steel（ULCB） was studied.The results show that,under the experimental conditions,the sample microstructure is granular bainite,and the sample strength and yield ratio are reasonable at the finish rolling temperature of 820 ℃ and the tempering temperature of 440 ℃.Controlled rolling and controlled cooling can refine bainitic ferrite and M-A island,reduce the carbon content of ferrite,control the ratio of soft against hard phases,thus increasing the strength and reducing the yield ratio.The increase of tempering temperature can make bainitic ferrite coarse,reduce carbon content and dislocation density,turn M-A island into small strips,and result in the precipitation of Cu-rich clusters,leading to the high strength and low yield ratio of the steel.