唐钢中厚板厂连铸保护渣结晶器渣膜矿相分析

为改善唐钢中厚板厂船板钢的浇铸条件以及铸坯质量,将现场所用保护渣A进行调整形成保护渣B。基于相图平衡计算,采用光学显微镜对保护渣A和B在结晶器内的渣膜进行观察,研究渣膜结构对保护渣润滑和传热的影响机制。结果表明,保护渣A析晶温度和析晶率较高,析晶矿相主要为导热系数大的黄长石,渣膜中存在不均匀分布的气孔,使得铸坯向结晶器传热较快且不均匀,并恶化铸坯润滑,导致发生黏结漏钢,且铸坯出现裂纹,轧材合格率为98.73%。而保护渣B析晶温度和析晶率相应有所降低,渣膜结构分层明显,存在玻璃层,析晶矿相有适量导热系数小的枪晶石,有少量气孔,能有效控制铸坯向结晶器壁的均匀传热,并保证润滑铸坯,避免了黏结漏钢,且显著减少了铸坯裂纹率,轧材合格率为99.65%。

Crystallization mineral of mold fluxes used in Tangsteel Medium Plate Plant

To improve the casting conditions and slab quality of ship plate steel in Tangshan Medium Plate Plant, the field applied mold flux A was modified into mold flux B. Based on the equilibrium phase calculation, the structures of the slag films formed in the mold for mold flux A and B were observed by optical microscope to study the influence mechanism of slag film structure on the lubrication and heat transfer. It can be found that the crystallization temperature and crystallization rate of mold flux A were higher, the main crystallization mineral was melilite with high thermal conductivity, and there were porosities unevenly distributed in the slag film. All these characteristics led to the fast and uneven heat transfer from strand shell to mold and deteriorate the slab lubrication, which resulted in sticking breakout and slab cracks, thus the qualification rate of rolled products was only 98.73%. However, for mold flux B, the crystallization temperature and crystallization rate were relatively decreased, the structure of slag film was obvious layered with appropriate glass layer, and there was moderate cuspidine with low thermal conductivity and a small amount of porosities. These characteristics were in favor of the uniform heat transfer and lubrication between strand shell and mold, which was beneficial to avoiding sticking breakout and reducing slab cracks, thus the qualification rate of rolled products was improved to 99.65%.