A predictive model for hydrogen content in steel in non-degassed heats

Abstract

Hydrogen may cause several problems during steel processing. Issues caused or enhanced by hydrogen range from different types of bubbles such as pinholes to breakout during continuous casting. Further down the line, segregation and embrittlement may lead to cracking such as flaking or blistering. These problems impact plant productivity and have cost impacts on equipment maintenance and the need for additional steel treatment. Some of the problems lead to scraping. Although vacuum degassing effectively controls the hydrogen content of steel, it introduces additional costs that are not justifiable for many products. This work aims to identify the main sources of hydrogen in liquid steel in the Ternium Brazil steelmaking plant and to propose a model to decide the need for hydrogen measurement for the degassing process, focusing on steels for which vacuum degassing is not a specification requirement. It is essential for these steels to guarantee a controlled level of dissolved hydrogen to avoid problems, mostly at casting. Once the sources are identified, a model is developed to predict the hydrogen content at the beginning of the secondary metallurgy treatment. Based on the model, it is proposed that hydrogen should be measured or not at this step to decide if vacuum degassing is required to assure safety in casting.