焊接对X65钢腐蚀疲劳裂纹扩展影响的试验研究

Experimental Study of Effect of Welding on Corrosion Fatigue Crack Propagation of X65 Steel

对于深海油气输送结构,焊接产生的初始预应力会对其腐蚀疲劳性能产生影响。针对深海油气输送常用材料X65钢开展腐蚀疲劳裂纹扩展试验。分别从焊接热影响区和母材上制备了标准紧凑拉伸(CT)试样,利用直流电压降(DCPD)方法测量了疲劳裂纹扩展长度,对焊接试件的腐蚀疲劳性能进行了研究,并拟合出了两种试件在不同试验环境下的Paris常数C和m。试验结果表明:在0.2 Hz的加载频率下,腐蚀溶液可明显加快裂纹扩展速率,并使裂纹扩展阈值分别提高16.25%和13.75%。焊接试件在空气环境下拟合的C值和m值均要略高于母材试件,在腐蚀环境下其C值和m值要略低于母材试件。

For deep-sea oil and gas transport structures, the initial pre-stress generated by welding will affect the corrosion fatigue performance. The corrosion fatigue crack propagation test was carried out on X65 steel which is commonly used for deep-sea oil and gas transportation. The standard compact tensile(CT) specimens were prepared from welding heat affect zone and base material, respectively. Direct current potential drop(DCPD) method was used to measure the fatigue crack length,the corrosion fatigue properties of welding specimens was studied, and the Paris constants C and m of two kinds of specimens were fitted in different test environments. The test results show that the corrosion solution can significantly accelerate the crack growth rate and increase the crack growth threshold by 16.25% and 13.75% respectively at the loading frequency of 0.2 Hz. The C and m values of the welding specimen fitted in the air environment are slightly higher than that of the base metal specimen. The value of the welding specimen in the corrosive environment is slightly lower than that of the base metal specimen.