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抗大变形管线钢加热并保温一段时间后,钢管力学性能将发生变化,通常会有屈服强度、屈强比升高,均匀延伸率降低,应力—应变曲线形状改变等,这些性能变化将降低钢管抵抗变形的能力。利用扫描镜等设备研究了冷却工艺对21mmX70HD抗大变形管线钢组织、性能和应变时效硬化的影响。结果表明,随着开始冷却温度的降低,先共析铁素体含量逐渐增加,贝氏体组织含量逐渐降低,贝氏体的组织相态由粒状贝氏体逐渐向板条贝氏体转变。当开始冷却温度在700℃时,试验钢板具有最佳的综合力学性能。试验钢板制成1016mm钢管后,钢管在200℃时效保温5min下,纵向屈服强度Rt0.5为497MPa,抗拉强度Rm为695MPa,伸长率为41%,屈强比Rt0.5/Rm为0.72,Rt1.5/Rt0.5为1.24、Rt2.0/Rt1.0为1.09,均匀变形伸长率达到9.0%。
After a long period of heating and holding, the mechanical properties of steel pipe will change. Generally, there will be yield strength, higher yield-strength ratio, lower uniform elongation, and change of stress-strain curve shape. Ability to resist deformation. The effects of cooling process on the microstructure, properties and strain hardening of 21mmX70HD large deformation pipeline steel were studied by scanning mirror and other equipment. The results show that the content of pro-eutectoid ferrite gradually increases and the content of bainite decreases gradually as the cooling temperature begins to decrease. The microstructure of bainite changes from granular bainite to lath bainite gradually. When the starting cooling temperature is 700 ℃, the test steel has the best comprehensive mechanical properties. After the test steel plate was made of 1016mm steel pipe, the longitudinal yield strength Rt0.5 was 497MPa, the tensile strength Rm was 695MPa, the elongation was 41% and the yield strength ratio Rt0.5 / Rm was 0.72, Rt1.5 / Rt0.5 is 1.24, Rt2.0 / Rt1.0 is 1.09, and the uniform deformation elongation reaches 9.0%.