Application Example: Steel Deoxidation on Tapping

This example shows a few of the ways the Process Metallurgy Module in Thermo-Calc can be used to investigate steel deoxidation (killing) on tapping.

Relevant Topics

  • Steel deoxidation on tapping
  • Steel killing
  • Steelmaking
  • Process Metallurgy Module 

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Read the full analysis in PDF format, which includes explanations of all the calculations and interpretation of the results. 

Download the calculation files, which can be run in Thermo-Calc. 

About Deoxidation or “Killing” of Steel

Deoxidation of steel, also known as killing of steel, occurs toward the end of the steelmaking process, but before desulphurization. After primary steelmaking, for example in a basic oxygen furnace (BOF) or electric arc furnace (EAF), the liquid steel contains a large amount of dissolved oxygen [O] (400 to over 1000 ppm, see the example on kinetic simulation of BOF process). This oxygen must be removed from the liquid steel for several reasons, including:

  • Desulphurization is not effective with high oxygen content in the steel (see example on desulphurization)
  • Continuous casting of un-killed steel is not possible and will result in “boiling” of the steel in the mould and massive porosity, as shown in the figure. 

Blowholes Formed During Casting Of Steel Billet
Blowholes formed during casting of a steel billet with insufficient deoxidation.

The two most widely applied methods of deoxidizing or killing the steel are by adding Al (Al-killed steel) or adding Si (Si-killed steel). These elements readily react with oxygen to form oxides that precipitate within the liquid steel. This does not reduce the total amount of oxygen in the liquid steel; it simply transforms the dissolved oxygen into an oxide precipitate. This oxide precipitate then needs to be removed from the steel by flotation during secondary metallurgy in the ladle furnace (LF).

About this Example

In this example we look at how the Process Metallurgy Module can be used to investigate these two widely applied methods of deoxidizing or killing the steel: adding Al (Al-killed steel) or adding Si (Si-killed steel). This, however, can result in the formation of damaging inclusions that cause problems during further processing, so we go on to look at two simple and very common processes that are used to transform the solid SiO2 and Al2O3 inclusions into liquid oxides so that they are less damaging. 

Read the full analysis in PDF format » 

Additional Examples Using the Process Metallurgy Module  

The Process Metallurgy Module can be used to investigate the entire steelmaking process, from scrap to fully refined steel. The examples below investigate other steps in the steelmaking process:   

Basic Oxygen Furnace Process 

Steel Refining in a Ladle Furnace

Desulphurization in a Ladle Furnace