MCCR产线低碳钢高拉速技术研究与应用

通过统计和分析现场数据,得出限制MCCR薄板坯连铸连轧低碳钢拉速提高的主要因素为结晶器热像图中的冷齿和结晶器液面波动,对冷齿和液面波动的成因进行研究,并提出有效控制措施。研究结果表明,结晶器热像图中的冷齿与结晶器弯月面凝固收缩特性相关,受冷却铜板厚度、碳当量、拉速及保护渣影响,反映到铸坯实物上为凹陷或者裂纹缺陷,需合理匹配形成最优参数组合,以降低因冷齿造成的漏钢风险。当结晶器铜板厚度减薄量在6.7%以内时,一冷水维持原设计流量;当结晶器铜板厚度减薄量在6.8%~11.1%时,拉速4.0 m/min以上时需降低10%的一冷水流量;当结晶器铜板厚度减薄量在11.2%~15.6%时,所有拉速下需降低18%的一冷水流量,同时使用高碱度B型保护渣。针对高拉速下结晶器液面波动问题,通过数值模拟研究浸入式水口插入深度、拉速、结晶器断面宽度及电磁制动等参数对结晶器内流场和温度场的影响规律,得到不同拉速和不同断面条件下电磁制动电流的合理配置,使得拉速达到5.5 m/min时钢液面最大流速仍小于0.3 m/s。上述研究结果应用后,结晶器冷齿问题得到有效缓解,110 mm厚的薄板坯最高拉速达到5.8 m/min,结晶器液面波动控制在±1 mm以内,保护渣液渣层厚度保持在8~10 mm,结晶器热流稳定,实现了高拉速的顺稳生产。

Research and application on high casting speed technology of low-carbon steel MCCR line

Through statistics and analysis of field data, it is concluded that the main factors limiting the increase of continuous casting speed of low-carbon steel for thin slab in MCCR line are cold teeth in thermal image and liquid level fluctuation in the mold. The causes of cold teeth and level fluctuation were studied, and effective control measures were proposed. The research results show that cold teeth thermal image in the mold are related to the solidification shrinkage characteristics of the mold meniscus, and affected by the thickness of mold copper plate, carbon equivalent, casting speed and mold powder. It is reflected that there are depression or crack defects on the slab. The optimal parameter combination should be formed by reasonable matching to reduce the risk of steel leakage caused by cold teeth. When the thickness reduction of the mold copper plate is within 6.7%, the primary cold water maintains the original design value; when the thickness reduction of the mold copper plate is 6.8%-11.1%, the water flow of primary cooling shall be reduced by 10% at the speed more than 4.0 m/min; when the thickness reduction of the mold copper plate is 11.2%-15.6%, the water flow of primary cooling shall be reduced by 18% at all speeds, and high alkalinity B-type mold powder shall be used at the same time. Aiming at the problem of mold level fluctuation under high speed, the effects of submerged nozzle immersion depth, casting speed, mold section width and electromagnetic braking on the flow field and temperature field in the mold were studied through numerical simulation. The reasonable configuration of electromagnetic braking current under different speeds and sections at high speed was obtained. When the speed reaches 5.5 m/min, the maximum speed of mold level was still less than 0.3 m/s. Through the application of the above research, the cold teeth problem of the mold has been effectively alleviated, the maximum speed of 110 mm thin slab has reached 5.8 m/min, the mold level fluctuation is controlled within ±1 mm, the thickness of mold liquid powder layer is maintained at 8-10 mm, the heat flow of the mold is stable, and the smooth and stable production at high speed has been realized.