Sn含量对耐酸钢高温塑性和耐蚀性的影响

Effect of Sn content on high temperature plasticity and corrosion resistance of acid resistant steel

针对含Sn耐酸钢的开发,采用高温拉伸、电化学和全浸腐蚀试验研究了Sn含量对耐酸钢高温塑性和耐蚀性的影响。试验钢中Sn质量分数由0.10%增加至0.14%时,由于晶界间析出脆性相增多,导致其铸坯的第Ⅲ脆性温度区间范围明显扩大,铸坯产生裂纹的风险显著增加。电化学试验结果表明:随着试验钢中Sn质量分数由0.05%增加至0.14%,由于其表面产生SnO_(2)腐蚀产物层,阻碍了腐蚀介质中的离子向基体继续扩散,离子传导阻抗迅速增加,从而导致自腐蚀电位、点蚀电位和电荷转移电阻增加,耐蚀性显著提高。采用正交设计的全浸试验结果表明:相同条件下,试验钢中Sn质量分数超过0.05%并继续增加时,其腐蚀速率呈下降趋势,耐蚀性逐渐提高。此外,温度对试验钢腐蚀速率的影响最大,Cl^(-)浓度对试验钢腐蚀速率的影响最小。综上,由于试验钢中Sn质量分数超过0.10%时,铸坯产生裂纹的风险显著增加,而Sn质量分数不足0.05%时,对耐蚀性基本没有贡献,兼顾两者的影响,耐酸钢中Sn质量分数应控制在0.05%~0.10%。

For the development of acid resistant steel containing Sn,the effects of Sn content on the high temperature plasticity and corrosion resistance of acid resistant steel were studied using high temperature tensile,electrochemical,and full immersion corrosion tests.When the addition of Sn mass fraction increased from 0.05% to 0.14%,due to the increase of brittle phases precipitated between grain boundaries,the third brittle temperature range of the billet was significantly expanded,and the risk of cracks in the billet significantly increased.The electrochemical test results show that,as the Sn mass fraction increases from 0.05% to 0.14%,due to the SnO_(2) corrosion product layer on its surface,which prevents the ions in the corrosion medium from diffusing to the matrix,the ion conduction impedance increases rapidly,resulting in the increase of self corrosion potential,pitting potential and charge transfer resistance,and the corrosion resistance is significantly improved.The results of immersion test by orthogonal design show that under the same conditions,when the Sn mass fraction in the tested steel exceeds 0.05% and continues to increase,its corrosion rate shows a downward trend and its corrosion resistance gradually improves.In addition,temperature has the greatest impact on the corrosion rate of the tested steel,while Cl^(-) concentration has the smallest impact on the corrosion rate of the tested steel.In summary,when the Sn mass fraction in the tested steel exceeds 0.10%,the risk of cracking in the casting billet significantly increases.However,when the Sn mass fraction is less than 0.05%,it has little contribution to corrosion resistance.Considering both effects,the Sn mass fraction in acid resistant steel should be controlled between 0.05% and 0.10%.