Study of Argon Shrouding in Ingot Casting, with Focus on Improving the Operation at Scana Björneborg Steel Plant

Sammanfattning: This thesis has been carried out as a development project at Scana Steel Björneborg with the purpose to study the influential parameters in argon shrouded ingot casting during the manufacturing of low-alloy steels. In the first stage, a literature study was conducted in order to investigate the theoretical background of the procedure and the importance of protecting the melt during ingot casting. Next, a computer model of the shield was designed using COMSOL Multiphysics® with regard to the process conditions at Scana Steel Björneborg. The effect of various parameters on the process was examined through simulations of the argon gas flow pattern, heat transfer between the gas and the melt stream, and the chemical species transport in the gas around the melt stream. Based on the simulation results, two different shapes of shield were proposed for the argon shrouding operation. A set of implementation tests was executed in order to check the installation and usage conditions of the two new shields. After deciding the proper shape of the shield, a full-scale ingot-casting test was performed with the selected shield to investigate the protection behavior. Moreover, the impact of the new casting-protection shield on the nitrogen and oxygen contents of steel was examined through sampling and analyzing the steel before and after casting. It was found that the use of the new shield during the uphill ingot casting is an effective way to reduce the final nitrogen and oxygen contents of the casted ingot. Therefore, the new design of the shield can be used as a developed substitute for the protection of the melt stream in the ingot casting operation.