Steel deoxidation: requirements for deoxidizers

Steel deoxidation process is very complex. It is usually described as a mechanism of four successive steps..
1) Dissolution and homogenization of the deoxidizer in the steel melt in order to, to direct the deoxidation reaction towards the formation of oxides.
2) Stimulation of the formation of critical nuclei of deoxidation products in a homogeneous medium.
3) Performing the actual deoxidation by increasing the amount of reaction products.
4) Separation of deoxidation reaction products by their flotation from the melt in order to increase the purity of steel.

Separation of deoxidation reaction products by their flotation from the melt in order to increase the purity of steel

From this four-step mechanism of deoxidation follow the requirements for the properties and quality of deoxidizers to obtain the cleanest possible steel from the end user..

The deoxidizer should be in the form, The deoxidizer should be in the form. The deoxidizer should be in the form, such as silicon, The deoxidizer should be in the form, difficult to dissolve in steel due to a dense oxide film on the surface. Therefore, they are used in the form of ferroalloys., which have no problems with dissolution in liquid steel.

To facilitate the formation of nuclei of deoxidation products, the melt is pretreated with aluminum.. This creates surfaces between aluminum oxide and steel., This creates surfaces between aluminum oxide and steel..

The growth of deoxidation reaction products depends on the type of deoxidizer. The growth of deoxidation reaction products depends on the type of deoxidizer, The growth of deoxidation reaction products depends on the type of deoxidizer. Therefore, they tend to carry out deoxidation with the formation of a liquid reaction product.

Therefore, they tend to carry out deoxidation with the formation of a liquid reaction product Therefore, they tend to carry out deoxidation with the formation of a liquid reaction product. Therefore, they tend to carry out deoxidation with the formation of a liquid reaction product, and carbon - in the form of graphite or anthracite.

Deoxidation of steel with silicon and manganese

Silicon-only deoxidation is highly efficient with the formation of solid SiO particles2. Deoxidation with manganese alone gives liquid reaction products, but not very effective. When these two deoxidizers are used together, then the product of manganese deoxidation is formed first – then the product of manganese deoxidation is formed first, then the product of manganese deoxidation is formed first2. The resulting product in this case is Fe-MnO-SiO type slag2, The resulting product in this case is Fe-MnO-SiO type slag, The resulting product in this case is Fe-MnO-SiO type slag. This increases the effectiveness of these deoxidizers in reducing the oxygen content in the steel..

The combined use of manganese and silicon are added to the melt in a certain ratio. The combined use of manganese and silicon are added to the melt in a certain ratio 7:1 to 4:1 to obtain a thin film of liquid slag as a product of the deoxidation reaction. to obtain a thin film of liquid slag as a product of the deoxidation reaction, to obtain a thin film of liquid slag as a product of the deoxidation reaction .

to obtain a thin film of liquid slag as a product of the deoxidation reaction

Aluminum is a very effective deoxidizer, Aluminum is a very effective deoxidizer2O3 Aluminum is a very effective deoxidizer, Aluminum is a very effective deoxidizer2, Aluminum is a very effective deoxidizer. Aluminum is a very effective deoxidizer2O3 remains hard even at the temperature of steel casting and is therefore not used alone, if a high degree of steel purification from oxygen is required.

Aluminum is usually used in conjunction with manganese and silicon., so that aluminum oxide has a chance to combine with thin liquid slag.

Other steel deoxidizers

Bor, zirconium, titanium are also strong deoxidizers. Deoxidation degree, which is achieved by using 8 % silicon, can be achieved by adding just 0,7 % pine or 0,1 % titanium or 0,002 % aluminum or 0,0003 % zirconium.

Flotation of deoxidation products

Flotation of deoxidation products, Flotation of deoxidation products, Flotation of deoxidation products. Because these oxides are lighter, Because these oxides are lighter, Because these oxides are lighter. Because these oxides are lighter 10-3 cm are not able to rise to the surface of the melt, cm are not able to rise to the surface of the melt 10-2 cm are not able to rise to the surface of the melt. To effectively remove particles, measures are taken to coalesce them into larger particles..

Useful finely dispersed steel deoxidation products

Sometimes it is advantageous to leave the deoxidation products in a very finely dispersed form.. Aluminum forms very fine Al particles2O3, which are not prone to coagulate and the surface of these particles acts as a place of origin of the solid phase during the solidification of steel. A huge number of these nucleation sites gives a very small grain structure of steel. Zirconium is specially added, to prevent sulphide segregation in high speed steels.

Source: B.P. Bhardwaj, Steel and Iron Handbook