Q125级ERW用石油套管钢力学性能及CO2腐蚀行为

设计研发一种低碳的Q125级ERW用石油套管用钢。运用SEM和TEM分析实验钢的强化机制,并采用高温高压反应釜对实验钢的CO2腐蚀行为进行研究。实验结果表明:实验钢的晶粒粒径10～15μm,晶区的长度约为2μm,马氏体板条束宽度约150 nm,这些均为实验钢具有较好的强韧性配合提供条件;直径约为50 nm的圆形(Nb,Ti)(C,N)析出物,通过钉扎晶界阻止γ晶粒的粗化过程,可有效阻止奥氏体晶粒的长大;直径约20 nm的椭圆形(Nb,Ti)C以及纳米级圆形NbC析出物,可起到钉扎位错的作用,阻止位错移动,可很大程度地提高强度;实验钢腐蚀速率随着温度的增加先增大后减小,在90℃时平均腐蚀速率和点蚀速率均达到最大值;在60℃时,点蚀速率与平均腐蚀速率相差程度最大。

Mechanical properties and CO2 corrosion behavior of Q125 grade oil tube steel used for ERW

A type of Q125 grade high-strength low carbide oil tube steel was designed and researched.The strengthening mechanism of steel was analyzed by SEM and TEM,and the CO2 corrosion behavior of steel was simulated by high-temperature and high-pressure autoclave.The results show that the size of prior austenite grain,packet and block are 10-15 μm,2 μm and 150 nm,respectively,so that the strength of the steel matched its toughness well.The precipitate of(Nb,Ti)(C,N) whose size is about 50 nm can restrain coarsening of the prior austenite grain through pitting austenite grain boundary.The precipitate of(Nb,Ti)C and nanometer size precipitate of NbC can be an effective barrier for dislocation motion,so that it has great contributions to improve the strength of the steel.The average and pitting corrosion rate increase first and then drop down with the increase of temperature.There is a maximum of average and pitting corrosion rate at 90 ℃.When the temperature is 60 ℃,there is a greatest difference between average corrosion rate and pitting corrosion rate.