GOALI: Turbulent Flow Modeling of Gas Injection to Minimize Surface Defects in Continuous-Cast Steel

Colorado School Of Mines, Golden CO

Investigators

Abstract

Many important commercial processes involve turbulent flow of molten metal mixed with gas. In steel continuous casting, used to manufacture 96% of steel in the US, problems with multiphase flow in the mold are responsible for most of the serious defects in final rolled steel products. Detrimental flow patterns allow particles to become entrapped in the solidifying steel shell, where they form permanent defects, leading to surface pinholes, slivers, blisters, and expensive rejects. With the difficulty of experimental measurements in the molten metal environment, computational models are an important tool to enable fundamental understanding of how these defects form, and to find windows of safe operating conditions to avoid them. This Grant Opportunity for Academic Liaison with Industry (GOALI) Program award supports creation of a new computational tool to study multiphase flow in molten metal systems with inert gas injection, and to apply this tool to better understand and improve steel continuous casting, in order to minimize the entrapment of gas bubbles, inclusions, and slag particles. This will benefit many engineering processes which involve these phenomena. In particular, the application of these tools to steel continuous casting will improve the quality of steel slabs and competitiveness of the US steel industry. This GOALI award supports a collaboration between University researchers experienced in computational modeling with an industry team at ArcelorMittal, experienced in conducting water modeling studies, measurements and trials in the operating steel plant, and metallurgical analysis of defects. A comprehensive model system is being developed to accurately simulate gas flow through the nozzle refractories, passive gas aspiration into low pressure regions, bubble formation during injection, unsteady multiphase flow in the nozzle and mold that ranges from bubbly to slug flow with and without electromagnetic effects, and particle transport and entrapment into the final product. Systematic measurements are being conducted at ArcelorMittal to quantify the size and location of entrapped bubble-related defects in many cast steel slabs, in order to validate the model system. The validated models will provide new insights into defect formation, and ways to improve caster operations will be proposed and tested. This fundamental project complements ongoing practical modeling efforts at the University Continuous Casting Consortium, which is currently supported by eleven member companies. Results will be conveyed to the steel industry via the Consortium and short courses to industry.