RU2354495C1 - Slag-forming mixture for metal protection in intermediate ladle during continuous steel casting - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention may be used for protecting metal surface in the intermediate ladle of continuous casting machine. The slag-forming mixture includes (wt %): slag-forming mixture production wastes (20 - 40), material on the basis of silicon oxides (to 20%) and cement (60 - 80).

EFFECT: use of slag-forming production wastes in claimed mixture as coal-bearing and fluorine-containing materials will reduce intermediate ladle lining deterioration and improve its heat insulation.

1 tbl

Description

The invention relates to ferrous metallurgy and can be used mainly to protect the metal surface in the tundish of a continuous casting machine for slab billets.

A known mixture used for processing metal in an intermediate ladle during continuous casting of steel (AS USSR, Cl. C21C 5/54, N 1310435, 1987). The mixture contains 5-20% amorphous graphite, 10-20% fluorspar, 20-40% cement, 5-20% silicate block and 20-40% perlite - a material based on silicon oxides. The disadvantages of this mixture is the insufficient assimilative ability of its slag melt due to the low basicity. In addition, the content in the mixture of fluorine-containing material leads to wear of the lining of the intermediate bucket in the region of the slag belt and stoppers.

A known mixture for protecting the surface of a metal containing 5-20% graphite, 5-20% fluorspar and 5-20% cement (AS USSR No. 544292, B22D 7/00). The disadvantages of this mixture is the high content of graphite, which can lead to an increase in the carbon content in the finished steel, which is not always desirable. In addition, the high content of fluorine-containing material (fluorspar) leads to wear of the lining of the intermediate bucket in the region of the slag belt and to wear of the stoppers. This mixture is expensive due to the high content of amorphous graphite in it.

The closest analogue of the inventive mixture is a mixture for protecting metal in a tundish during continuous casting, containing 2-10% carbon-containing material, 10-20% fluorine-containing material, 10-25% silicon-based material and the rest (RU, No. 2174893, B22D 11/111). The disadvantages of this mixture is the high content of fluorine-containing material in the mixture, which leads to wear of the lining of the intermediate bucket.

The problem solved by the invention is the selection of the optimal composition of the slag-forming mixture, which reduces the wear of the lining of the intermediate bucket and improves thermal insulation.

The problem is solved in that the slag-forming mixture for protecting metal in the intermediate ladle during continuous casting of steel, including carbon-containing and fluorine-containing materials, a material based on silicon oxides and cement, according to the invention, waste from the production of a slag-forming mixture is used as carbon-containing and fluorine-containing materials, while the ingredients mixtures are taken in the following ratio,%:

Waste production 20-40 Silicon Oxide Material up to 20 Cement 60-80

Dust and cake obtained from the production of granular slag-forming mixture, namely, by drying the suspension in a tower spray dryer, are used as production waste.

Cement is used in the form of slag Portland cement grade 300 according to GOST 10178-85.

As a material based on silicon oxides, quartz concentrate or foundry sand is used.

When the SCO production waste content is in the range of 20-40%, minimum wear of the lining of the intermediate bucket is provided.

When the SCO production waste content is less than 20%, the slag melt forms a hard crust - “roof”. This leads to the formation of viscous slag and further to thickening of the slag and a deterioration of assimilation ability, which leads to a deterioration in the quality of the metal.

When the SCO production waste content is more than 40%, the slag melt of such a mixture begins to intensively corrode the lining of the intermediate bucket, which leads to a decrease in the duration of the campaign of the intermediate caster ladle.

The cement content in the range of 60-80% leads to the formation of slag melt, which provides the necessary thermal insulation and minimal wear of the lining of the intermediate bucket.

When the cement content is less than 60%, the basicity of the slag melt decreases and intensive wear of the lining of the intermediate bucket is noted.

When the cement content is more than 80%, the basicity of the mixture increases, which leads to a thickening of the slag and a decrease in the assimilation of slag from non-metallic inclusions.

As a material based on silicon oxides, quartz concentrate or foundry sand is mainly used to ensure the basicity of the slag melt in the range 1.2 ... 1.6. When using this material, the basicity of the slag decreases by more than 20%, which leads to intensive erosion of the lining of the intermediate ladle.

When the contents of the ingredients in the mixture go beyond the specified limits, the maintenance technology for the intermediate bucket is violated (hindered), the thermal insulation of the metal deteriorates and the lining resistance of the intermediate bucket decreases.

The proposed mixture was made in the department of slag-forming mixtures LLC "Shlakservis" OJSC "Magnitogorsk Iron and Steel Works". Slag-forming mixture was prepared as follows. Prepared charge materials from storage hoppers were loaded into a “dry” mixing mill, where materials were ground with simultaneous mixing.

After 30-40 minutes of co-grinding, a sample is taken to determine the fractional composition. Then the finished mixture was poured into the filling machine and packaged in paper bags weighing 10-12 kg.

The composition of the inventive mixture is presented in the table.

Table Mix No. The content of components,% Technical result Waste production Cement Silicon Oxide Material one 25 60 fifteen Adequate insulation, low lining wear 2 60 twenty twenty Adequate insulation, high lining wear 3 10 80 10 Insufficient insulation, increased lining wear

The resulting mixture was used in an intermediate ladle of a slab continuous casting machine. The work of the mixture in the tundish and its consumption were evaluated visually.

When using the new mixture No. 1, 9 melts of St12 steel were cast on one intermediate ladle. There are no comments on the operation of the mixture and slag in the tundish. The average consumption of the mixture was 0.44 kg / t of cast steel. After casting was completed, an inspection bucket was inspected. The wear of the lining of the intermediate bucket in the region of the slag belt, as well as the wear of the stoppers, were in accordance with the norm.

When using the new mixture No. 2, 6 heats were cast on one intermediate ladle. There are no comments on the operation of the mixture and slag in the tundish. The consumption of the mixture was 0.39 kg / t of cast steel. During use of the mixture, wear of the lining along the slag belt is noted. After the casting was completed, the intermediate ladle was inspected: wear of the intermediate ladle lining in the region of the slag belt was noted, namely, complete wear of the working layer of the lining (100 mm) and wear of the reinforcing layer (15 mm), which led to the withdrawal of the bucket from circulation and setting it to capital repairs.

When using the new mixture No. 3, 4 heats were cast on one intermediate ladle. Further use of the mixture was discontinued due to the formation of viscous slag, which turned into a solid slag crust, which made it difficult for maintenance personnel to service the tundish. Lining wear was noted in the area of the slag belt. The average consumption of the mixture was 0.40 kg / t of cast steel.

Thus, the observation of the mixtures showed the advantage of the inventive mixture No. 1 in comparison with mixtures No. 2 and No. 3 in the wear of the lining of the intermediate bucket and in the work of the mixture in the intermediate bucket.

Claims (1)

Slag-forming mixture for protecting metal in the intermediate ladle during continuous casting of steel, including carbon-containing and fluorine-containing materials, a material based on silicon oxides and cement, characterized in that as the carbon-containing and fluorine-containing materials, waste from the production of slag-forming mixture is used in the following ratio of ingredients, wt.% :
waste production slag-forming mixture 20-40 silica based material up to 20 cement 60-80