轴承钢连铸过程中非金属夹杂物群迁移行为的分析

为了研究轴承钢方坯连铸过程中存在的非金属夹杂物聚集问题,建立了凝固过程的流-固耦合模型,采用数值模拟和现场试验相结合的方法,研究了浇注过程中夹杂物族群的迁移行为。结果表明,在断面、结晶器搅拌强度和浸入式水口对比方面,较大断面、较强搅拌和带侧孔的水口对改善铸坯中10 μm以下的夹杂物比较有利,5～10 μm级别夹杂物最易被初生坯壳捕捉。结果显示,5 μm以下的中间包钢液中微观夹杂物数量过大,在浇注过程中会促进夹杂物族群间的碰撞迁移,导致铸坯中20～30 μm级别夹杂物数量增多,但对50 μm以上的大尺寸夹杂物影响甚微;铸坯中该大尺寸级别的夹杂物主要直接来源于中间包。这些研究结果对弄清夹杂物的来源,改善轴承钢疲劳寿命具有重要意义。

Behavior analysis of non-metallic inclusion groups in bearing steel during bloom casting

In order to study the aggregation of non-metallic inclusions in the continuous casting process of bearing steel, a flow-solidify-coupled model of solidification process was established. The migration behavior of inclusions in the casting process was studied by means of numerical simulation combined with factory tests. The results show that, as the comparison of casting varieties, such as mould sections, the M-EMS, and SEN types, the parameters of bigger sections, stronger M-EMS stirring and many-side-port SEN nozzles, are more favorable to improve the inclusions below 10 μm in the bloom, and the inclusions of 5-10 μm level are most easily captured by the raw casting shell. Results also show that, high number density of microscopic inclusion groups in tundish, which are below 5 μm, will promote the collision and migration during the pouring process, resulting in an accumulation of inclusion groups with 20-30 μm in the bloom, but has little effect on large size inclusion groups, which are above 50 μm. The inclusion groups with that macro size level in the bloom are mainly originated from tundish directly. These results are of great significance to clarify the origin of inclusions and improve the fatigue life of bearing steel.