Sn对Q125级ERW套管力学性能及腐蚀行为的影响

Influence of Sn on Mechanical Properties and Corrosion Behaviors of Q125-Grade Tube Used for ERW

采用扫描电镜、透射电镜、电子背散射衍射和电化学等分析了Sn对Q125级ERW石油套管用钢力学性能和抗CO2腐蚀性能的影响.结果表明:Sn的加入对钢的显微结构、析出物形态和尺寸均没有影响,因此强度变化不明显;少量Sn的加入改变了钢的活性,引起自腐蚀电位负移,腐蚀电流密度减小,同时实验钢电极反应的极化电阻增大,腐蚀反应变慢,耐腐蚀性能得到提高;Sn的加入使钢中小角度晶界的比例有所增大,提高了实验钢的耐腐蚀性,大角度晶界的比例则减小,使实验钢的延伸率和冲击功显著下降.

In this paper,the influences of Sn on the mechanical properties and CO2 corrosion resistance of the Q125-grade oil tube used for ERW were investigated by means of SEM,TEM,EBSD and electrochemical measurement.The results show that Sn has no influence on the microstructure of the steel as well as the forms and sizes of precipitates,so that there is no obvious change of the steel strength.However,the activity of the tested steel changes after the addition of a little Sn,which results in the negative shift of corrosion potential,the decrease in corrosion current density,the increase in the polarization resistance of electrode reaction and the deceleration of the co-rrosion,thus improving the corrosion resistance of the tube.Moreover,it is found that,with the addition of Sn,both the proportion of small-angle grain boundary and the corrosion resistance of the steel improve,while the proportion of large-angle grain boundary decreases,which results in a decrease in the elongation and impact energy of the steel.