摘要
随着连铸技术的不断发展,对连铸钢水的洁净度和铸坯质量的要求也越来越高。结晶器是连铸机的心脏,是改善铸坯质量,去除钢中夹杂物的最后环节,对铸坯质量有着重要的影响。结晶器内钢液的流动行为包括液面的波动、注流对窄面的冲击、渣层覆盖状况、表面流速等,极大地影响着铸坯质量和浇铸过程的顺行。优化浸入式水口结构参数和结晶器操作参数是改善结晶器内钢液流动方式、优化结晶器流场的有效手段,对提高连铸坯质量具有重要作用。
本文以重钢环保搬迁在建1#板坯连铸结晶器为研究对象,根据相似原理,建立1:0.55的物理模型。采用水力学模拟方法,对160mm、190mm和230mm厚度结晶器进行物理模拟。通过测量和分析液面波动、渣层分布、卷渣次数、冲击深度、流场显示等实验指标,研究拉速、插入深度、塞棒吹气量、结晶器断面宽度以及中间包液位深度对结晶器内钢液流动行为的影响;在此基础上,对重钢新厂的浸入式水口结构参数和结晶器操作参数进行设计。此外实验还制作了相似比为1:0.8的结晶器模型,研究不同结晶器相似比对结晶器流场的影响。由于重钢新厂尚未投产,水口进行现场应用还需要进一步的研究。
研究结果表明:160mm厚度结晶器选用B2#(凸底、倾角向下15o、侧孔面积3289mm2)水口。在实验条件下,采用优选的水口时,结晶器液面稳定,保护渣覆盖良好;结晶器表面流速适当,即有利于保护渣的熔化,又不至于产生卷渣。190mm厚度结晶器选用3#水口(凸底、倾角向下15o、侧孔面积3846mm2)和2#水口(凸底、倾角向下20o、侧孔面积4334mm2);其中3#水口适用于转炉单联工艺对应的拉速,2#水口适用于转炉双联工艺对应的拉速。230mm厚度结晶器选用2#和7#(凹底、倾角向下15o、侧孔面积3846mm2)水口,其中2#水口适用于转炉单联工艺对应的拉速,7#水口适用于转炉双联工艺对应的拉速。
不同相似比物理模型的研究表明:模型与实物的相似比为0.55,较相似比为0.8结晶器液面波动小,液渣分布均匀。物理模拟实验中,在研究钢渣界面行为时,有必要同时满足Fr准数和We准数相等。
With the development of continuous casting technology, it becomes more and more important to improve the cleanliness and quality of casting steel. The mold which serves as a heart during continuous casting is the last process that improves the liquid steel quality and removes inclusions, it has important influence on slab quality. The fluid flow of molten steel include the level fluctuation, the impact depth, the state of slag blanket and the surface velocity, which exactly effect the quality of slab and the security of casting process. Optimize the Submerged Entry Nozzle (SEN) and the production parameter of mold are the available measure to improve fluid flow and promote the reasonable distribution of molten steel, which have significant function to enhance the quality of slab.
According to the No.1 continuous caster of the steelmaking factory of Chongqing Iron and Steel Company, a 1:0.55 mold model based on conform theory was established in this paper. Using water model, this paper has studied systematically 160mm, 190mm and 230mm thickness mold. Using the physical simulation which consisted of the level fluctuation, the state of slag blanket, the slag entrapment and the impact depth etc , this paper researched how the casting speed, immerged depth, blowing volume, different mold section and tundish depth influence the mold flow field. Based on this, this paper designed the submerged entry nozzle structural parameters mold operation parameters. Besides, a 1:0.8 mold model has established to research the effect of fluid flow on different similitude ratio. Because the new plant hasn’t put into production, the plant application needs more research.
The results indicate that: 160mm thickness of mold preferred B2# nozzle (concave bottom, downwards 15°, 3289 mm2 side area). As a result, the fluid flow of molten steel was stable, mold slag covered well; mold surface velocity was properly, which is beneficial for the slag melting and liquid level stabilizing. 190mm thickness of mold preferred 3# (convex bottom, downwards 15°, 3846 mm2 side area) and 2# nozzle, (convex bottom, downwards20°, 4334 mm2 side area); the 3# nozzle can be the choice for conventional steelmaking technology of converter, the 2# nozzle can be the choice for duplex steelmaking technology of converter. 230mm thickness of mold preferred 2# and 7# nozzle (concave bottom, downwards 15°, 3846 mm2 side area), the 2# can be the choice for conventional steelmaking technology of converter, the 7# nozzle can be the choice for duplex steelmaking technology of converter.
Different similitude ratio physical simulation research showed: model and practicality similitude ratio was 0.55, the surface fluctuation was smaller than the 0.8 similitude ratio, liquid slag distributed uniformity. At physical simulation experiments, it is necessary to meet the Fr and We number to study the behavior of steel-slag interface.
引文
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