Ladle furnace of the process analysis

LF refining is one of the main methods of refining outside the furnace

The purpose of LF slag is to desulphurize, deoxidize, improve the yield of alloy and remove inclusions, but in the process of aluminum steel slag, desulphurize and return silicon, add nitrogen, remove inclusions have certain contradictions, need to be considered as a whole. In LF fast and stable to produce good fluidity and a certain emulsification of reducing white slag, IS LF desulfurization, adsorption inclusions and ensure the quality of molten steel is necessary.

Taking European standard S235JR controlled aluminum steel (low silicon steel) as an example, the production process is as follows: multi-blown converter → argon station →LF→CC. When the converter steel is produced, the stirring kinetic energy is used to add an appropriate amount of lime for slag washing and pre-making reduction slag to ensure the basicity and prevent phosphorus and silicon from returning. The whole process of steel soft mixing uniform composition and temperature; Using steel core aluminum (or aluminum manganese magnesium) to deoxidize liquid steel; According to the amount of slagging (generally about 5kg/t), add appropriate amount of modifier in time after steel production; High carbon manganese was used for alloying.

Based on the analysis of slag making process, slag composition transformation process and comprehensive basicity change of slag  

The following technological measures for rapid white slag making are obtained

(1) Converter slags are modified in advance

 Which can provide favorable conditions for LF slags making quickly; At the same time, when the converter steel should also be strictly controlled: blowing, slag, bottom blowing, packing, a deoxidation several links.

(2) Early rapid slagging is the premise of slagging. Control points

 Rapid temperature rise, submerged arc, mixing, and reasonable addition of slag making agent in batches.

(3) Strong stirring desulfurization (4.0 ~ 6.0L/(min·t))

The speed should be fast, the time should be short, while ensuring desulfurization, as far as possible to control the secondary oxidation and liquid steel nitrogen absorption time. Generally, it is completed within 10 ~ 20min after the beginning of LF processing. This stage is the main stage of LF refining.

(4) After the completion of desulfurization

The main tasks of LF are temperature control, alloying and inclusion removal. In this stage, the slag viscosity should be ensured and the stirring intensity should be controlled from 0.5 L/ (min·t) to 1.0L/ (min·t) (based on the principle of liquid level fluctuation but not exposed steel level), and the retention time should be greater than 8min.