碳含量和组织类型对低合金钢耐蚀性的影响

研究了不同碳含量和显微组织的低合金钢的耐腐蚀性能和腐蚀行为,并与商业耐候钢09CuPCrNi进行了相应的比较.通过金相显微镜、扫描电镜观察,轧后水冷钢的主体组织为板条状贝氏体,轧后空冷钢为针状铁素体、粒状贝氏体、M/A小岛和少量渗碳体(珠光体)的混合物.用干湿循环加速腐蚀实验对耐蚀性测定结果表明:低碳钢(0.03%C)和轧后水冷的较高碳含量钢(0.1%C)的耐蚀性均明显优于09CuPCrNi;低碳含量钢的组织类型对其耐蚀性影响不大;较高碳含量情况下,单相贝氏体钢的耐蚀性优于由铁素体、渗碳体(珠光体)等构成的复相组织钢;轧后水冷时,不同碳含量的钢耐蚀性差别不大;轧后空冷时,低碳含量钢的耐蚀性优于较高碳含量钢.用扫描电镜对锈层进行观察,可以看出耐蚀性较好的样品在腐蚀后期形成了致密的内锈层.

Effect of carbon content and microstructure on the corrosion resistance of low alloy steels

The corrosion resistance and corrosion behavior of low alloy steels with different carbon contents and different microstructures were investigated and compared with a commercial weathering steel 09CuPCrNi.Optical microscopy and SEM were employed to examine the microstructures of these steels.It was revealed that the dominant microstructure in the steel cooled in water after rolling is lath-like bainite while the microstructure in the steel cooled in air after rolling is the mixture of acicular ferrite,granular bainite,M/A islands and little cementite(pearlite).Cyclic wet-dry test was carried out to evaluate the corrosion resistance of these steels.The results indicate that the corrosion resistance of the low carbon steel with 0.03% C or 0.1% C,which was cooled in water after rolling,excels that of 09CuPCrNi steel.Provided with low carbon content,the influence of microstructure on the corrosion resistance of the tested steel is not obvious.With a higher carbon content,the bainitic steel with single phase exhibits a higher corrosion resistance than multi-phase steel constituted by ferrite and cementite(pearlite).No marked distinction can be detected in the corrosion resistance of the steels with different carbon contents when they were cooled in water after rolling.When cooled in air after rolling,the steel with low carbon content exhibits a higher corrosion resistance than the steel with a higher carbon content.Through observations on rust layers with SEM,it can be found that a compact inner rust layer forms in the specimen with excellent corrosion resistance after long corrosion.