Analysis of Surface Defects of High Strength Welding Wire Steel N2M2T Continuous Casting Billet and Process Improvement

Abstract

In response to the surface defects such as concavities， deep vibration marks， cracks， and slag pits on the surface of continuous casting billets during the smelting of N2M2T high-strength welding wire steel in a certain steel plant，combined with theoretical analysis and actual production conditions on site， an analysis was proposed to analyze the surface defects of N2M2T high-strength welding wire steel continuous casting billets from four aspects： the physical and chemical properties of protective slag， mold vibration parameter mode， primary cooling water distribution， and N content in the steel. The analysis results indicate that the surface defects generated by continuous casting billets are mainly related to the physicochemical indicators of the protective slag， mold vibration parameters， and N content in the steel， but not to the primary cooling water distribution. Production practice shows that by increasing the alkalinity of the protective slag from 0. 6 to 1. 19， the C content is reduced from 13. 51% to 8. 21%， and the viscosity is reduced from 0.666 Pa. s to 0.156 Pa. s； The deviation rate of mold vibration parameters has been increased from 0.15 to 0.20， and the vibration frequency formula has been adjusted from 60+50 V to 90+60 V； Control the N content in steel to ＜50 × 10-6， continuous casting process △ N ＜ 7 × 10-6； The surface defects of N2M2T high-strength welding wire steel continuous casting billet have been significantly improved， and the qualification rate of the billet has increased from 85% to over 95%， providing assurance for stable rolling of subsequent steel rolling

Keywords

• high strength welding wire steel； casting vibration marks； protective slag； corner cracks； continuous casting billet