卷取温度对X80M热轧带钢微观组织及力学性能的影响

Effect of coiling temperature on microstructures and mechanical properties of X80M hot rolled strip

高级别管线钢不仅可以满足长距离高压大输量输送油气的要求,还能大幅度节约钢材,积极地响应国家的“双碳”战略目标。然而国内能够实现X80M管线钢稳定供货的厂家不多,其中卷取工艺作为影响管线钢稳定生产的重要一环而备受关注。测定了不同卷取工艺下X80M热轧带钢的拉伸性能,并对其微观组织进行了表征,分析了卷取温度对X80M热轧带钢微观组织和拉伸性能的影响。研究结果显示,随着卷取温度的升高,板条贝氏体逐渐减少直至消失,粒状贝氏体逐渐增多,并出现了少量的针状铁素体;平均晶粒尺寸增大,马氏体/奥氏体(M/A)组元的形态由条状向块状转变,面积分数增加;屈服强度和抗拉强度降低,而断后伸长率和冲击功则逐渐升高。晶粒尺寸与屈服强度的Hall-Petch关系拟合程度较好,各卷取工艺下晶界强化对屈服强度的贡献率为57.1%~62.7%,晶界强化为该工艺下X80M管线钢的主要强化方式。卷取温度的升高使得过冷度减小、位错密度降低,随着晶粒尺寸增大,位错滑移过程中的阻力减小,滑移更容易进行,这将导致断后伸长率升高;大角度晶界所占比例随卷取温度的升高而增大,显著阻碍裂纹的扩展,使得冲击功升高。试验结果为X80M管线钢的热轧生产提供了参考。

The high-grade pipeline steel can not only meet the requirements of long-distance high-pressure large oil and gas transmission,but also greatly save steels,which can well response to the national strategic goal of"carbon peaking"and"carbon neutrality".However,few domestic manufacturers can realize the stable supply of X80M pipeline steel,among which the coiling process as an important link to affect its stable production has attracted much attention.The tensile properties of X80Mhot rolled strip were measured under different coiling processes,and the microstructure was characterized.The effects of coiling temperature on the microstructure and tensile properties of X80Mhot rolled strip were analyzed.The results show that with the increase of coiling temperature,lath bainite gradually decreases until to disappear,granular bainite increases,and a small amount of acicular ferrite appears.The average grain size increases with the increase of coiling temperature and morphology of M/A constituents change from strip to block,and its area percentage increases.The yield strength and tensile strength decrease with the increase of coiling temperature,while the elongation and impact energy increase gradually.The Hall-Petch relationship between grain size and yield strength is well fitted,and the contribution rate of grain boundary strengthening to yield strength under each coiling process is 57.1%-62.7%,so it can be considered that grain boundary strengthening is the main strengthening method of X80Mpipeline steel.With the increase of coiling temperature,the degree of supercooling decreases,dislocation density decreases and grain size increases.The dislocation sliding is easier to carry out and the resistance during the sliding decreases,leading to the increase of elongation.Meanwhile,the proportion of high angle grain boundary increases,which significantly hinders the crack propagation and increases the impact energy.The experimental results provide a reference for the hot-rolling production of X80Mpipeline steel.