含硫45钢铸坯缺陷分析与工艺优化

Analysis on Defects of Casting Billet of 0.45C Steel Bearing Sulfur and Process Optimization

含硫45钢(/%:0.42～0.50C,0.17～0.37Si,0.50～0.80Mn,≤0.035P,0.035～0.045S)的Φ44 mm轧材探伤合格率低,轧材表面存在裂纹缺陷,通过分析是由150 mm×150 mm铸坯缺陷导致的。对铸坯表面酸洗发现裂纹缺陷,采用金相显微镜对裂纹进行分析。分析认为是由结晶器铜管R角太小、角部冷却太强、保护渣熔化不好、传热和润滑效果差以及二次冷却不均匀导致的。通过对结晶器铜管、保护渣及二次冷却水量进行工艺优化,改善结晶器冷却传热和二冷段喷淋冷却效果,提高铸坯冷却均匀性,使得铸坯缺陷明显改善,轧材合格率大幅提高。

Abstract Facing the quality problems of low pass rate and crack defects on the surface of the （I）44 mm metal rolling 45 with sulfur（/% ：0. 42 -O. 50C,0. 17 - 0. 37Si,0. 50 - 0. 80Mn, ≤0. 035P,0. 035 - 0. 045S）, the analysis is that the defects are caused by defects in the 150 mm x 150 mm casting billet. The crack defects are found on the surface of the slab and analyzed by metallographic microscope. The result indicates that the defect is caused by the strong cooling of the small R of crystallizer copper tube and the poor heat transfer and lubrication effect of the shielding flux and the asymmetrical sec- ondary cooling. The process optimization of the crystallizer copper tube and the shielding flux and the second cooling is car- ried out. It improves the cooling heat transfer of the mold and the cooling effect of the secondary cooling section and the cooling uniformity of casting billet. The result shows the defects of casting billet have been effective controlled and the qual- ified rate of rolled material has been greatly improved.