PL168590B1 - Mixture for off-furnace treating open-hearth, electric furnace and converter steels as far as their refining and ladle slag formation are concerned - Google Patents

Abstract

1. Mixture for pazkaidcowzj pi ^ i ^ c ^ t ^ ki Marian jtals, electric and converter for the refining and formation of ladle slag, characterized in that it comprises a mixture of desulfurizers and fluidizers in the following proportions: 70-80% by weight hard-burned lime, 10-18% by weight of fluorspar and 7-12% by weight of dross aluminum.

Description

The subject of the invention is a mixture for the secondary treatment of open hearth, electric and converter steels in the field of refining and formation of ladle slag.

So far, in order to desulphurize liquid steel, apart from the steelmaking aggregate, mixtures containing the most common components such as lime (CoO), fluorite (CaF2) or calcium-silicon (CaSi) are used. Obtaining a high degree of steel desulphurization is associated with a significant cost of the used reagents, especially calcium-silicon or fluorspar.

A cheaper and effective slag-forming mixture was developed and tested in a series of tests. which not only provides for the formation of ladle slag with the required properties (basicity and liquidity), but also effectively desulfates the liquid steel after tapping from the furnace aggregate.

This mixture contains 70-80% by weight of hard burned lime, 10-18% by weight of fluorspar and 7-12% by weight of aluminum scrap (fraction III waste in aluminum production). Depending on the method of its introduction into the liquid steel, the grain size of the mixture may vary up to 40 mm, and the method of its preparation is as follows. The hard quicklime delivered to the plant is milled in a roller mill to the required initial granulation. Then it undergoes the process of screening and segregation into individual grain fractions in a vibrating screen. The weighed ingredients of the recipe are mixed in a roller mixer, and then bagged by a bagging machine into appropriate quantitative portions. The content of H2O in the mixture must not exceed 0.5%.

This mixture can be introduced in the production of converter, electric and open hearth steels, both:

- on the steel stream during tapping,

- to the bottom of the ladle before draining,

- to the ladle while it is being filled with liquid steel and with a lance immersed in the metal directly or in a stream of argon or nitrogen (then the grain size of the mixture is up to 4 mm).

The blend can be used to form active ladle slag and to desulphurize steel in both convection ladles and in all secondary metallurgy processes, especially the LF (Ladle Furnace) process.

The amount of the mixture addition should be from 4 to 8 kg / Mg of steel, while the addition of 4 kg / Mg of steel introduced to the steel stream during tapping and to the bottom of the ladle provides a 30-40% degree of desulphurization, while the addition of 8 kg / Mg of steel introduced with the lance provides a degree of desulphurization of 60-70%, depending on the initial sulfur content of the steel before introducing the mixture.

Publishing Department of the UP RP. Circulation of 90 copies

Price PLN 1.50

Claims (2)

Patent claims 1. Mixture for secondary furnace processing of open hearth, electric and converter steels in the field of refining and formation of ladle slag, characterized by the fact that it contains a mixture of desulfurizers and fluidizers in the following proportions: 70-80% by weight of hard-burned lime, 10-18% by weight of fluorspar and 7 -12% by weight of aluminum scrap. 2. A mixture according to claim The grain of claim 1, characterized in that its grain size when blowing with the lance is up to 4 mm, and with the addition to the steel stream during tapping, to the bottom of the ladle before tapping, and to the ladle while it is being filled with liquid steel, to 40 mm.