The final steel chemistry and casting temperature from a basic oxygen furnace (BOF) or electric arc furnace (EAF) is attained by secondary steel making or secondary metallurgy. As the liquid steel is tapped from the furnace, tap-time additions and heat loss create a highly dynamic thermo-physical process in the liquid bath. During the subsequent holding period, the liquid layers in the ladle undergo thermal stratification resulting from natural convection. Thermal stratification is detrimental to quality casting. Tap temperature, holding time, ladle preheat and ladle life significantly influence the rate of stratification. Argon gas purging through the liquid steel bath helps to generate enough bath turbulence to cause rapid thermal homogenization. Stirring with argon also enhances the mixing rate for chemical additions.

Temperature after 20 minutes holding of a 130 ton steel ladle

Using Fluent CFD, various processes in secondary steel making can be analyzed and optimum process parameters can be achieved. For example, effect of purging rate Vs. Heat size, effect of ladle preheat, effects of carry-over slag and synthetic slag volume, thermal effects and mixing rates of various chemical additions. Depending on a particular plant layout of equipment, CFD can help you to determine the best practice for additions and thereby optimize the process time.

Temperature after 3 minutes of homogenization by bottom purging of argon through the steel ladle

The first image here shows the growth of thermal stratification in a 130-ton steel ladle after 20 minutes of holding. This bath is then agitated by purging of argon gas from the bottom and as the second image shows, the bath temperature is homogenized in as little as 3 minutes.