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通过金相组织分析研究了X70HD管线钢在两阶段变形后弛豫时间和终冷温度对微观组织的影响。结果表明,第二阶段变形后空冷弛豫到700℃,获得铁素体+下贝氏体的双相组织且无先共析铁素体生成,但随弛豫时间的延长有先共析铁素体生成并获得多边形铁素体+贝氏体的双相组织。终冷温度影响贝氏体的种类及含量,终冷温度保温时会产生更多下贝氏体;在相同弛豫条件下,终冷到320℃获得铁素体+少量粒状贝氏体,终冷到350℃获得铁素体+少量下贝氏体。
The influence of the relaxation time and the final cooling temperature on the microstructure of X70HD pipeline steel after two-stage deformation was studied by means of microstructure analysis. The results show that in the second stage of deformation, the air-cooling relaxes to 700 ℃ and the ferrite + lower bainite duplex structure is obtained without proeutectoid ferrite formation. However, with the extension of the relaxation time, the pro-eutectoid iron The body generates and obtains biphasic tissue of polygonal ferrite + bainite. The final cooling temperature affects the type and content of bainite, and the lower bainite will be produced when the final cooling temperature is maintained. In the same relaxation condition, the final cooling is carried out to 320 ℃ to obtain ferrite plus a small amount of granular bainite Cold to 350 ℃ to obtain ferrite + a small amount of lower bainite.