超快冷对X80管线钢屈强比的影响

对超快冷条件下X80管线钢屈强比的影响因素进行了系统研究;结合光学电镜、扫描电镜和透射电镜对冲击断口和组织的观察,得出了超快冷条件下低屈强比X80管线钢强韧性匹配的最优工艺.结果表明:随着超快冷终止温度的降低,实验钢强度和屈强比均呈升高趋势;超快冷终止温度为655℃时,实验钢组织由针状铁素体、贝氏体和M/A岛组成,强韧性匹配良好;在"超快冷+空冷+层流冷却"的冷却模式下,随着空冷时间的延长,实验钢的屈强比逐渐降低;超快冷的应用在提高实验钢强度的同时有利于实现X80管线钢的低屈强比,为高级别的抗大变形管线钢的开发奠定了基础.

Effects of Ultra-fast Cooling on Yield Ratio of X80 Pipeline Steel

How ultra fast cooling affected the yield ratio of X80 pipeline steel was investigated by Metalloscope,SEM and TEM.The optimal technique for the pipeline steel with low yield ratio,high strength and high toughness was proposed.The experimental results revealed that both the strength and yield ratio of X80 pipeline steel increase gradually with decreasing the ending temperature of ultra fast cooling.When the ending temperature is about 655 ℃,the microstructure of the steel consists of acicular ferrite,bainite and M/A islands,which make the steel have a good balance between strength and toughness.Under the cooling mode of "ultra fast cooling+air cooling+laminar cooling",the yield ratio decreases with increasing air cooling time.Ultra fast cooling can not only enhance the strength,but decrease the yield ratio of X80 pipeline steel,which is important for developing high strength and high-deformability pipeline steel.