Origin of large spherical or bar-shaped inclusions in calcium treated steel
QIN Zheng-feng1,2, XUE Zheng-liang1,2, LI Jin-bo3, LI Bo-si1,2
1. The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081, Hubei, China; 2. Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education, Wuhan 430081, Hubei, China; 3. Hansteel Co., HBIS Group, Handan 056015, Hebei, China
Abstract:Large inclusions have a very harmful effect on the processing properties, mechanical properties and corrosion resistance of steel. The properties of large spherical or bar-shaped inclusions, which were obtained by electrolytic extraction method in calcium treated steel, were investigated. The results of both the scanning electron microscopy (SEM) and elemental composition analysis indicated that the large spherical or bar-shaped inclusions were originated from the clustered aluminum de-oxidation product, such as Al2O3. A large number of small Al2O3particles had the tendency to form large-sized inclusion clusters, which further form a spherical or bar-shaped by the complex flow field in the ladle. During the calcium treatment process, the modified inclusions can form a low melting calcium aluminate, which can form dense spherical shaped inclusions during the solidification process of molten steel; the shape of the inclusions with insufficient modified was still kept the same morphology as Al2O3 inclusion. The w([Ca])/ w([Al]) ratio required for calcium treatment to modify Al2O3 inclusions is primarily affected by the content of S. The calcium aluminate has a strong absorption and dissolution ability to S in molten steel. During the casting process, as the temperature of molten steel decreasing, the S element absorbed by the calcium aluminate was precipitated from the matrix in the form of CaS inclusions.
秦正丰, 薛正良, 李金波, 李博思. 钙处理钢中大型球状及棒状夹杂的成因[J]. 钢铁, 2020, 55(5): 31-38.
QIN Zheng-feng, XUE Zheng-liang, LI Jin-bo, LI Bo-si. Origin of large spherical or bar-shaped inclusions in calcium treated steel. Iron and Steel, 2020, 55(5): 31-38.
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