Scarring causes on SWRCH22A wire rod surface and improvement measures

It is of great significance to investigate the scarring causes on SWRCH22A wire rod surface for improving the quality stability of steel for fastening piece and reducing the scrap rate in downstream processing. This paper aimed to clarify the scarring causes on SWRCH22A wire rod surface and formulate overall process improvement measures to effectively control the scarring defects. By collecting SWRCH22A wire rod samples with surface scarring, the distribution characteristics and macroscopic morphology of scarring were observed. The inclusions distribution and the matrix structure in the scarring areas were observed by metallographic analysis. The types and elemental composition of inclusions in the scarring areas were determined by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), and the inclusions in the steel were rated. It indicated that aluminum oxide type (Class B) inclusions were the main scarring cause on SWRCH22A wire rods surface, resulting from insufficient flotation of deoxidation products in the molten steel and the formation of large particle accumulations. Through measures such as converter steel pouring slag control, optimization of deoxidation system, development of dedicated refining slag system (with w(CaO)/w(Al₂O₃) ranging from 1.3 to 1.8 and w(Al₂O₃) ranging from 25% to 35%), control of w(Ca)/w(Al) more than 0.1 in the steel, strengthening continuous casting protection pouring and optimizing protective slag, the inclusions in the steel were significantly reduced, the wire rod scarring rate decreased from 0.63% to 0, and there was no flocculation during the continuous casting process, effectively improving the product quality stability.