H型钢Q235B连铸保护渣的优化

针对津西钢铁厂H型钢Q235B(0.14%～0.18%C)铸坯(宽面550 mm,窄面440 mm,腹板90 mm)经常出现纵裂等缺陷,基于原有保护渣(%:29～30SiO2、25～26CaO、10～11Al2O3、3.0～3.5Fe₂O₃、15～17C、≤0.5H₂O),通过正交实验和优化设计,开发出一种高性能保护渣(%:37.50SiO₂、37.50CaO、6Al₂O₃、7CaF₂、12Na₂O、7石墨、1.5炭黑)。与原保护渣相比,优化渣的半球点温度、粘度和熔化时间分别从1 167℃,0.77 Pa·s和57 s下降至1 092℃,0.27 Pa·s和32.5 s。优化渣应用表明,当拉速由0.98 m/min提高到1.2 m/min时,铸坯质量良好。

Optimization of Mold Powder for H-Shape Steel Q235B Casting

To counter the situation of longitudinal crack defect usually occurred on bloom (wide side 550 mm, narrow side 440 mm, waist 90 mm) in H-shape steel Q235B (0. 14% ~0. 18%C) casting at Jinxi Iron and Steel works, based on original mold powder (% : 29~30Si02, 25 ~26CaO, 10 ~ 11A12O3, 3. 0 ~ 3.5Fe₂O₃, 15 ~ 17C,≤0.5H₂O), a high performance mold powder (% : 37. 50Si0₂, 37. 50CaO, 6A1₂O₃, 7CaF₂, 12Na₂O, 7 graphite, 1. 5 carbon black) is developed by orthogonal experimental and optimum design. As compared with original mold powder, the semi-sphere point temperature, viscosity and melting time of improved mold powder decrease respectively to 1 092 ℃ , 0. 27 Pa ? s and 32. 5 s from original 1 167℃ , 0. 77 Pa ? s and 57 s. Application shows that as casting speed increase from 0. 98 m/min to 1. 2 m/min, the bloom has high quality by using the improved mold powder.