管线钢焊缝的应力腐蚀破裂研究

STRESS CORROSION CRACKING RESEARCH ON PIPELINE STELL WELD

观察国产ＷＸ５２及日本产Ｔ／Ｓ５２Ｋ管线钢在硝盐介质中应力腐蚀开裂（ＳＣＣ）现象，比较了母材与焊缝应力腐蚀敏感性差别，探讨了腐蚀介质温度的影响．试验表明：两种管线钢焊缝在未进行改善处理的情况下，焊缝比母材临界应力腐蚀开裂应力σｃｒ将近降了一半；温度越高，应力腐蚀敏感电位区间越宽．为了提高焊缝抗应力腐蚀能力，在ＷＸ５２管线钢埋弧焊焊缝中渗入微量Ｔｉ、Ｂ、稀土Ｙ等合金元素．结果表明：加入这些合金元素都能使得焊缝组织得到改善，减少晶界先共析铁素体，使应力腐蚀通道受到阻碍和限制，影响电化学效应。

With the observation of the Stress Corrosion Cracking (SCC) phenomena of the domestic WX52 pipeline steel and the Japanese T/S52K pipeline steel in the medium of nitrate, this paper compares the base metals with the stress corrosion susceptibility of the weld beads. The effect of the medium under different temperatures is discussed. It has been proved that, under the condition of not improving or treating the weld beads of these two kinds of materials, the weld beads stress of the critical stress corrosion crack( σ cr ) is reduced by nearly a half than that of the basemetals. The higher the temperature, the wider the potential range of the materialsstress corrosion susceptibility. In order to improve the resistance of SCC, we put a very little alloy elements into weld bead of WX52 pipeline steel. Tests show that all the elements mentionted above can improve the form of the structure and degrade the amount of the preeutectord territe of the grain boundary, restrict the path of stress corrosion, influence the electrochemical effect and improve the weld bead resistance of WX52 pipelin steel in nitrate.