不同低碳钢的点蚀诱发敏感性及诱发机理研究

RESEARCH OF PITTING SUSCEPTIBILITY IN LOW CARBON STEELS AND MECHANISM OF PITTING INITIATION

选择 4种冶金因素有代表性的低碳钢 ,通过极化试验比较了它们之间的点蚀诱发敏感性 .电子探针分析了不同夹杂物在诱发点蚀过程中的腐蚀特征 ,显微腐蚀试验确定了点蚀诱发初期溶解产物的性质 .结果表明 ,沸腾钢的点蚀敏感性显著低于镇静钢 ,稀土处理镇静钢则介于前两者之间 .夹杂物是钢中主要点蚀诱发源 ,紧靠夹杂物的钢基体处的钝化膜保护作用最弱 ,点蚀均从该处基体诱发 .同类夹杂物在不同类型钢中的点蚀诱发敏感性差异较大 .同一钢中不同类型夹杂物的点蚀诱发敏感性差异很小 ,硫化物夹杂较其它夹杂物的点蚀诱发敏感性强 .

Four low carbon steels with different metallurgy factors have been selected.Their susceptibility to pitting has been compared by means of polarization test.Characteristic of pitting initiated by different inclusions has been studied with the EPMA and the dissolving production has been confirmed with the MCT during pitting initiation.The results showed that the susceptibility of boiling steel to pitting initiation was markedly lower than those of killed steel ,the pitting susceptibility of killed steel treated by rare earth was between boiling steel and common killed steel.The inclusions were the sites most susceptible to pitting initiation.Passivation film of boundary between steel matrix and inclusions was the weakest and the early pitting corrosion was caused from here.The difference of susceptibility to pitting initiated by homogeneous inclusions was large when these inclusions existed in different kind of steels.The difference of susceptibility to pitting initiated by different inclusions in the one steel was small and the sulfide inclusions had bigger ability of initiating pitting than other types of inclusions did.