Method for determining steel belt feeding process parameter of crystallizer in thick slab continuous casting process

Abstract

The invention relates to a method for determining the steel belt feeding process parameter of a crystallizer in the thick slab continuous casting process. The method comprises the steps the work condition parameter of the crystallizer in the thick slab continuous casting process is collected, and the feeding quantity of a cold steel belt is determined through the work condition parameter of the crystallizer in the thick slab continuous casting process based on the liquidus congruent melting and phase change heat transfer theory; a continuous casting slab-cold steel belt system phase change heat transfer theoretical model is built through a generalized enthalpy method, namely, a relation model among the melting time and feeding thickness of the cold steel belt, the superheat degree of casting molten steel and the initial temperature of the cold steel belt; the section size and feeding speed of the cold steel belt are determined through the continuous casting slab-cold steel belt system phase change heat transfer theoretical model according to the feeding quantity and melting time of the cold steel belt and the depth of a solidified liquid core; and the cold steel belt with the determined section size and feeding speed is preheated and fed into molten steel in the crystallizer through the position between a water opening and a narrow face of the thick slab crystallizer parallel to the wide face of the crystallizer in a low-amplitude high-vibration manner.

Description

technical field [0001] The invention belongs to the field of thick slab continuous casting production, and in particular relates to a method for determining process parameters of a crystallizer feeding strip in the thick slab continuous casting process. Background technique [0002] Compared with the traditional mold casting process, the continuous casting process is a major technological progress, but many inherent product defects restrict the quality of continuous casting products. The general problems to be solved for medium-thick slabs, extra-thick slabs and thicker rectangular slabs are internal quality defects such as center segregation, center porosity, center cracks, and low equiaxed crystal ratio. Defects such as center segregation and center porosity of continuous casting slabs are bottlenecks that restrict the further improvement of thick slab quality, so eliminating or controlling problems such as center segregation, center porosity and cracks is the key to solvi...

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Problems solved by technology

These measures are a good way to clean and homogenize molten steel and reduce internal defects of slabs; however, the degree of improvement is limited, and excessive requirements will increase the difficulty of smelting and increase the cost of smelting

Slight reduction at the end of the liquid core compensates the solidification shrinkage of the slab by applying pressure near the end of the liquid core to compensate for the solidification shrinkage of the slab. On the one hand, it can eliminate or reduce the internal voids formed by the shrinkage of the slab and prevent intergranular enrichment The molten steel with solute elements flows laterally toward the center of the slab; on the other hand, the extrusion effect generated by light pressure can also promote the reverse flow of molten steel enriched with solute elements in the center of the liquid core along the direction of casting, so that the solute elements are Redistribution in the molten steel, so that the solidified structure of the slab is more uniform and dense, which plays a role in improving center segregation and reducing center porosity. This technology has a significant effect on improving the internal quality of thin slabs, but the effect on thick slabs is not significant

Electromagnetic stirring technology can increase the equiaxed crystal ratio on the cross-section of the slab, thereby effectively improving the central segregation, but the existing problems are that the electromagnetic stirring position is difficult to control accurately, the adaptability is poor, and the maintenance cost is high; especially when the slab thickness and specifications are large When the solid phase ratio is high, due to the influence of the skin effect of the induced current, the stirring effect on the center of the slab is lost

However, there is an important problem in the process of industrialization: the amount of fed steel strip is not controlled accurately, and the steel strip that is not completely melted often remains in the continuous casting slab

However, the melting model or the theoretical feeding speed model proposed in the current research literature have been oversimplified to varying degrees, making it impossible to accurately determine the crystallizer feeding process parameters

For example, the speed formula for feeding the cold steel strip proposed in the article "A Production Method for Homogenized Casting Slabs of Medium-low Carbon and High-strength Steel" (CN201410740946.1) only considers the process of molten steel from the tundish to the crystallizer. Heat, without considering the heat taken away by the cooling water of the crystallizer and the influence of the latent heat of the melting process of the cold steel strip, such calculation results are far from the actual production experiments

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