X70钢在模拟深海环境中的腐蚀对力学及疲劳性能影响分析

Analysis of the Influence of Corrosion of X70 Steel on Its Mechanical and Fatigue Properties in Simulated Deep-sea Environment

基于模拟深海环境腐蚀试验,分析获得深海常用管线钢X70的腐蚀规律,采用三维扫描仪获得不同腐蚀时间对应的腐蚀坑分布和深度。基于腐蚀规律和扫描结果采用MATLAB编程获得标准试件表面腐蚀坑分布,采用ABAQUS建立不同腐蚀程度的标准试件模型,并模拟试件拉伸和单轴疲劳试验,以获得腐蚀影响的X70钢力学和疲劳性能。结果表明,随着腐蚀时间增加,X70钢的腐蚀速率随着腐蚀时间增加呈现先增大后减少最终趋于稳定的趋势。随着腐蚀速率增加,X70钢屈服强度和极限抗拉强度变化不大,但是伸长率明显降低;X70钢的疲劳性能明显降低,在疲劳寿命为10~7时的疲劳强度从未腐蚀的195 MPa最大降低至121 MPa,下降率高达37.95%。

The corrosion law of X70,a common pipeline steel in deep sea,was obtained based on simulated corrosion tests in deep sea environment.A three-dimensional scanner was used to obtain the distribution and depth of corrosion pits at different corrosion times,and MATLAB programming was used to obtain the corrosion pit distribution on the surface of standard specimens according to the corrosion law and scanning results.ABAQUS was used to model the standard specimens with different corrosion levels and simulate the specimen tensile and uniaxial fatigue tests to obtain the mechanical and fatigue properties of X70 steel under the influence of corrosion.The results show that,as the corrosion time increases,more and more corrosion products adhere to the surface of the steel pendant,preventing the corrosion medium from contacting with the steel pendant,which will lead to the corrosion rate of X70 steel with the increase of corrosion time showing a trend of first increasing,then decreasing and finally stabilizing.With the increase of corrosion rate,the yield strength and ultimate tensile strength of X70 steel during the test period do not change much,but the elongation decreases significantly.As the corrosion rate increases,the fatigue performance of X70 steel decreases significantly,and the conditional fatigue limit decreases from 195 MPa to 121 MPa,with a decrease rate of 37.95%.