X70管线钢屈强比控制的实践与分析

结合管线钢的生产实践,针对X70管线钢屈强比偏高的问题,从工艺及显微组织控制方面进行了深入分析。结果显示:开冷温度低、终冷温度偏高、针状铁素体及贝氏体等硬相组织含量偏少是导致钢板屈强比偏高的主要原因。终冷温度降低到430℃以下,形成的板条贝氏体能大幅度提高钢板的抗拉强度,而屈服强度提高不大,屈强比可得到有效降低。

Practice and Analysis of Yield-Tensile Ratio Control for X70 Pipeline Steel

Based on the production practice of pipeline steel, the paper deeply analyzes the causes of higher yield - tensile ratio of X70 pipeline steel from the aspect of process control and microstructure. The result shows that low start cooling temperature, comparatively higher finish cooling temperature, less hard phase components of acicular ferrite and bainite are the major causes of the higher yield - tensile ratio of steel plate. The lath bainite formed at the finish cooling temperature ≤ 430 ℃ will significantly improve the tensile strength of steel plate, but not the yield strength. The yield- tensile ratio can be effectively reduced.