CSP连铸薄板坯中非金属夹杂物行为研究

Inclusions in Low Carbon Al-Killed Steel Produced by CSP

通过在炼钢和连铸过程的各个阶段加入不同的示踪元素,采用金相观察、大样电解、电子探针及扫描电镜等多种方法对邯钢CSP流程低碳铝镇静钢中非金属夹杂物行为进行了调查研究,找出了夹杂物的来源、数量及分布的变化规律。研究表明CSP薄板坯的洁净度水平低于传统板坯,在相同的钢种和热轧板厚条件下,邯钢CSP热轧板卷生产的冷轧板缺陷率比传统工艺热轧板卷生产的冷轧板缺陷率高62%。对结晶器EMBr实际使用效果研究表明,无电磁制动时,结晶器液面波动为±7 mm,使用电磁制动时,结晶器液面波动为±4 mm,钢中w(TO)降低了40%,大型夹杂物减少了61%。应用CFX软件数学模拟了电磁制动及无电磁制动情况下的CSP结晶器流场。模拟结果表明,在邯钢现行工艺条件下,结晶器使用电磁制动后,结晶器弯月面钢水中心线速率降低了约3倍,湍动能降低了2倍左右。结晶器钢水流动减缓,结晶器钢水卷渣明显减轻,薄板坯洁净度明显改善。

The investigation on non-metallic inclusions was made by adding different tracer elements into ladle slag, tundish flux and tundish lining. By means of metallographic, EPMA and SEM observation and electrolysis, the source, size and distribution of inclusions were studied. It was shown that the conventional slab is cleaner than CSP thin slab. For the same steel grades and the same thickness of hot strip the number of defects of cold sheets produced from CSP hot strip was 62% higher than that produced by conventional hot strip. Trail experiments indicated that the meniscus fluctuation without EMBr is ±7 mm and ±4 mm with EMBr and the total oxygen and macro-inclusions with EMBr were more reduced than that without EMBr by 40% and 61% respectively. Fluid flow in the mold with or without EMBr was simulated by CFX software, the results showed that the flow rate at surface and the turbulent kinetic energy at the center of meniscus with EMBr are 3 times and 2 times lower than that without EMBr respectively. Thus the slag entrapping is alleviated and the cleanness of thin slab can be improved obviously.