弛豫时间和终冷温度对X70HD抗大变形管线钢微观组织的影响

Influences of Relaxation Time and Finish Cooling Temperature on Microstructure of X70HD Pipeline Steel with High Deformability

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 influences of relaxation time and final cooling temperature on the microstructure of X70HD pipeline steel after the two stages of deformation were studied by means of the analysis of the microstructure. The results show that, a dual phase microstructure with ferrite and lower bainite is obtained and proeutectoid ferrite does not generate after the second stage of deformation and then air cooling relaxation to 700 ~C. But with the extension of relaxation time, the proeutectoid ferrite produces and dual phase structure with polygonal ferrite and bainite is obtained. The final cooling temperature influences the type and content of bainite, the more lower bainite will be produced during the insulation with finish cooling temperature. Under the same relaxation condition, the ferrite and a small amount of granular bainite are obtained when final cooling to 320℃; the ferrite and a small amount of lower bainite are obtained when fmal cooling to 350℃.