Comparison of Tramp Elements Compositions in Steel Bars between Japan and China

Synopsis : In this study, a random sample of 107 steel bars from Japan and 26 steel bars from China were studied. Each specimen's elemental composition of tramp elements, such as Cu, Cr, Ni, and Sn, was analyzed. By using the compositions of specific tramp elements, 99 of the 107 samples and 16 of the 26 samples were recognized as electric arc furnace steel. The distributions of the tramp element composition were obtained for the Japanese steel bars and represent a larger number of samples than previous studies. Those for the Chinese samples are the first published data. The compositions of Cu, Cr, Ni, and Sn in the Japanese bars are statistically significantly higher than those in the Chinese bars. Owing to the large gap between the Cu contents of the Japanese and Chinese samples, and the statistically significantly differences between the ratios of Cu to both Ni and Cr in the Japanese and Chinese samples, it is highly likely that copper-based materials are separated from steel scrap at a higher rate in China. The relationship between the Cu and Cr compositions suggested that the mixing of copper-based materials and special steels, which contribute to Cr contamination, differs between Japan and China. The distributions of the Cr composition for each country had larger standard deviations than the distributions of other elements. The ratio of the Cr and Ni compositions in the Chinese samples is less than 2.25, resulting in 18% Cr and 8% Ni in stainless steel. It was found that Ni from materials other than stainless steel was likely to have been included.