第二相粒子对V-Ti微合金油井管钢力学性能的影响

Effect of secondary phase particles on V-Ti microalloy steel of oil country tubular goods(OCTG) mechanical properties

利用萃取复型分析技术研究了V-Ti微合金油井管钢中第二相粒子的尺寸、形貌、数量和成分等特征及其对显微组织和力学性能的影响。结果表明,V-Ti微合金钢中存在大量弥散分布的第二相粒子。尺寸较大的粒子近似方形,含Ti量较高而含V量较低;尺寸较小的粒子近似圆形,含V量较高而含Ti量较低或不含Ti。这些粒子增加了裂纹源的分布密度,降低了钢的韧性。通过提高淬火温度至890℃,减少未溶第二相粒子的数量,增强回火析出强化效果,而且没有使奥氏体晶粒过分长大,从而改善了试验钢的力学性能。

The size,morphology,quantity and composition of the secondary phase particles in V-Ti microalloyed steel of OCTG were investigated using carbon extraction replica technique.Their effect on microstructure and mechanical property were researched.The results show that there are a lot of fine dispersed secondary phase particles in the steel.The larger particles having square shape contain higher Ti and lower V.The smaller particles having circular shape contain higher V and lower Ti,even none Ti.These particles increase the source of crack and decrease the toughness of steel.Improving the quenching temperature to 890 ℃ that can reduce the number of undissolving secondary phase particles,enhance the effect of tempering precipitation strength and don＇t make the austenite grains grow up obviously,thus improving the mechanical property.