V、N含量和热处理对抗腐蚀油套管组织和性能的影响∗

摘要

The effect of V and N addition on microstructure and mechanical properties of microalloyed medium carbon steel at different normalized temperature had been studied.The results showed that even though the pre-cipitation strengthening effect was promoted with the increase of V and N,the strength of material decreases and toughness was greatly improved.The amount of ferrite in V3 steel with higher V and N content is almost 6 times more than that of V1 steel with lower V and N content at normalized temperature of 950 ℃.However, the size of pearlite grains in V1 steel is about 3 times larger than that of V3 steel at 850 ℃.Meanwile,the con-tent of ferrite and pearlite of material reduces and that of bainite increases at higher normalized temperature.It is obvious that increasing V and N content and decreasing normalized temperature is beneficial to the amount of ferrite and pearlite.According to analyses,the undissolved V(C,N)prevents coarsening of austenite grain,ser-ving as nucleation of proeutectoid ferrite,promoting transformation of ferrite,inhibiting transformation of bainite.Subsequently,the ferrite and pearlite microstructure with good corrosion resistant property is formed, and the strength reaches up to 80ksi (552 MPa).%研究了不同正火温度和不同 V、N 含量对1％Cr 中碳钢的组织和力学性能的影响,结果表明,V、N 含量提高,虽然增加了析出强化作用,但材料强度却随之降低,韧性大幅度提高。在950℃正火温度下较高 V、N 含量 V3钢中的铁素体含量是较低V、N含量的V1钢中铁素体的6倍,而在850℃正火温度下V1钢中的珠光体晶粒尺寸是V3钢的3倍。随着正火温度提高,铁素体和珠光体含量均降低,贝氏体含量增加。因此可以看出增加V、N含量以及降低正火温度都有利于铁素体和珠光体组织转变。通过分析可知,未溶解的 V(C,N)会阻碍奥氏体晶粒的粗化,并作为先共析铁素体的形核质点促进了铁素体转变,阻碍了贝氏体的形成,从而获得了具有良好抗腐蚀性能的铁素体＋珠光体组织结构,并且使材料强度达到80ksi(552 MPa)。