RU2356687C2 - Slag-forming mixture for tundish ladle - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention can be used for protection of metal surface in tundish ladle of continuous steel casting machine. Slag-forming mixture contains (wt %): microsilica 36 - 40, powdered wastes of aluminium manufacturing 19 - 23, powdered wastes of lime production 39 - 43. Chemical composition of mixture, wt %: C 4.0 - 16.0, CaO 24.0 - 35.0, SiO₂ 32.0 - 40.0, Al₂O₃ 6.0 - 13.0, F 2.5 - 8.5, Na₂O 2.0 - 8.0, K₂O 0.5 - 4.0, providing relation CaO/SiO₂=0.7 - 1.0, provides optimal physicochemical characteristics of slag.

EFFECT: there are increased heat-insulating and refine ability of mixture.

Description

The invention relates to ferrous metallurgy, and in particular to compositions of slag-forming mixtures used for thermal insulation and protection of a metal mirror in an intermediate ladle from secondary oxidation during continuous casting of steel.

Known selected as a prototype slag-forming mixture for continuous casting of steel, including amorphous graphite, lime, dusty waste from the production of ferrosilicon, dusty waste from the production of aluminum in the following components, wt. %:

amorphous graphite - 10-20

lime - 20-30

dusty production waste of ferrosilicon - 30-40

dusty waste from aluminum production - 20-30 [1].

Significant disadvantages of this mixture when used in an intermediate ladle are the uncontrolled process of carburizing steel and low heat-insulating and refining properties due to the content of amorphous graphite in the mixture.

The technical results of the invention are:

- increase the heat-insulating ability of the mixture;

- an increase in the refining ability of the mixture.

To achieve this, a slag-forming mixture for an intermediate ladle is proposed containing dusty waste from aluminum production, characterized in that it contains silica fume and dusty waste from lime production, in the following ratio, wt.%:

silica fume 36-40 aluminum dust production 19-23 pulverized waste of lime production 39-43,

with the following chemical composition, wt.%:

FROM 4.0-16.0 CaO 24.0-35.0 SiO ₂ 32.0-40.0 Al ₂ O ₃ 6.0-13.0 F 2.5-8.5 Na ₂ O 2.0-8.0 K ₂ O 0.5-4.0

and CaO / SiO ₂ ratio = 0.7-1.0.

The claimed ratio of the components is selected empirically, and with a change in the ratio of the components, the fluidity and heat-insulating properties of the slag mixture are reduced.

With a decrease in the content of pulverized waste from aluminum production in the mixture below 19%, the viscosity increases and the thermal conductivity of the slag mixture increases. If the content of dusty aluminum waste in the mixture exceeds 23%, the slag viscosity decreases and the likelihood of an increase in the amount of alumina-containing inclusions in the steel increases.

A decrease in the content of silica fume in the mixture below 36% leads to an increase in the melting temperature of the mixture and a decrease in the heat-insulating properties. When the content of silica fume in the mixture is more than 40%, an increase in the viscosity of the slag melt is observed, which leads to the formation of a skull around the stoppers of the bucket.

Dust of lime production together with other components of the slag mixture provides the optimal physicochemical characteristics of the slag melt, necessary for the assimilation of non-metallic inclusions and insulation of the metal. It has been experimentally established that this effect is achieved when the content of lime dust in the slag mixture is 39-43%.

An experimental slag mixture was made by dosing the starting materials by weight as follows. The dispenser was mounted on the weight frame of the trolley with an electronic weight indicator. Moving the cart with the dispenser under the bunker overpass, it was alternately stopped under one of the three bunkers with the starting materials (silica fume, aluminum dust, lime dust). After installing the dispenser under the hopper, the shutter was opened on it and the dispenser was filled. In electronic scales, weight information about each source material was laid. The ratio of starting materials per dispenser was,%:

silica fume 36-40 aluminum dust production 19-23 lime dust 39-43.

The filled dispenser was transferred to the mixing plant. To achieve a uniform composition of the mixture, the materials were mixed in a mixing unit for at least 30 minutes.

The experiments were carried out on a four-strand bloom caster with a cross-section of a mold of 300 × 330 mm when casting steel grades st.3-5 sp, E76, E76F.

During casting in the intermediate ladle, a slag-forming mixture in the amount of 130-155 kg was set in a series on the mirror of the first melting metal; when changing the next casting ladle, a slag-forming mixture in the amount of up to 60 kg was planted in the intermediate ladle.

The use of slag mixture during continuous casting of steel made it possible to reduce the temperature gradient of the metal in the intermediate ladle to 7-9 ° С and, as a result, reject the metal due to violation of the temperature-speed regime by 0.7%, reduce steel contamination by non-metallic inclusions (line length of silicate inclusions reduced by 0.2 mm, alumina-containing by 0.05 mm).

Information sources

1. A.S. USSR 1702696, C21C 5/54.

Claims (1)

Slag-forming mixture for the intermediate ladle containing dusty waste from aluminum production, characterized in that it additionally contains silica fume and dusty waste from lime production in the following ratio, wt.%:
silica fume 36-40 aluminum dust production 19-23 pulverized waste of lime production 39-43,
with the following chemical composition, wt.%:
FROM 4.0-16.0 CaO 24.0-35.0 SiO ₂ 32.0-40.0 Al ₂ About ₃ 6.0-13.0 F 2.5-8.5 Na ₂ O 2.0-8.0 K ₂ O 0.5-4.0
and CaO / SiO ₂ ratio = 0.7-1.0.