RU2393050C1 - Heat-insulation mix for steel-teeming ladle - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: proposed mix can be used for heat insulation of metal mirror in steel-teeming and tundish ladles. Proposed mix comprises expanded perlite and dusty wastes of dust-free coke discharge of the following fractional composition: 0÷0.1 mm - 6-10%, 0.1÷0.25 mm - 47-50%, 0.25 ÷ 0.5 mm - 25.8-26.8%, 0.5 ÷ 3.0 - 10.7-16.7, >3.0 mm - less than 1.2%. Carbon content in dusty wastes makes at least 82%, ash content is less than 9.7%, moisture content does not exceed 0.8%. Mix components are taken in the following ratio, wt %: Perlite - 52.63-63.16, dusty wastes of dust-free coke discharge - 36.84-47.37.

EFFECT: higher heat-insulation capacity.

Description

The invention relates to ferrous metallurgy, and in particular to compositions of heat-insulating mixtures used for thermal insulation of the surface of a metal mirror in steel-pouring and intermediate ladles.

Known selected as a prototype heat-insulating mixture for casting steel containing expanded perlite and amorphous graphite, characterized in that, in order to improve the quality of steel, these components are taken in the following ratio, vol.%:

amorphous graphite 10-20;

expanded perlite - the rest [1].

Significant technical disadvantages of this mixture when used in a steel pouring ladle are the uncontrolled process of carburizing steel, the high cost and increased complexity associated with the need to manually level the mixture with a scraper on the melt surface due to the low spreadability on the surface of liquid metal and slag (due to the use of carbon-containing material amorphous graphite).

A heat-insulating mixture for continuous casting of steel is also known, containing a silica-containing material and an organic additive, characterized in that it contains a carbon-containing material in which calcium oxides are introduced, with a content of not more than 50% silicon oxide in it, in the following ratio, wt.%:

Carbon-containing material 4-25

Rice husk 4-90

Silica-containing material - Else

Silica-containing material, has the following composition, wt.%; CaO 30.0-60.0; SiO ₂ 20.0-50.0; Al ₂ O ₃ 3.0-7.0; MnO 0.5-5.0; MgO 3.0-7.0; (Na ₂ O + K ₂ O) 0.1-2.0; C 4.0-20.0; FeO 0.1-5.0; F 0.001-5.0; TiO ₂ 0.1-2.0 with basicity CaO / SiO ₂ = 0.6-3.0.

As a carbon-containing material, the heat insulating mixture contains coke.

Significant technical disadvantages of this mixture when used in a steel pouring ladle are the uncontrolled process of carburizing steel, the increased cost of the mixture due to the use of imported organic component (rice husk), high injury risk due to intense burning of the organic component.

The technical results of the invention are:

- increase the heat-insulating ability of the mixture;

- reduced labor intensity and increased safety during use;

- increase in yield due to an increase in the seriality of steel casting at CCM.

For this purpose, a heat-insulating mixture for warming steel in a steel pouring ladle is proposed, containing expanded perlite and a carbon-containing material, characterized in that the dust-containing waste of the dust-free coke delivery unit of the fraction 0 ÷ 0.1 mm 6-10%, 0.1 ÷ is used as the carbon-containing material 0.25 mm 47-50%, 0.25 ÷ 0.5 25.8-26.8%, 0.5 ÷ 3.0 10.7 - 16.7,> 3.0 mm - less than 1.2 %, with a carbon content of at least 82%, an ash content of less than 9.7%, a moisture content of less than 0.8%, and these components are taken in the following ratio, wt.%:

perlite 52.63-63.16;

dusty waste of the dust-free coke delivery plant 36.84-47.37

The claimed ratio of the components is selected empirically, and when the ratio of the components is changed, the spreadability on the melt surface and the heat-insulating properties of the slag mixture are reduced. The functional purpose of the ingredients included in the insulating mixture is as follows:

- expanded perlite, being a loose component with a mass fraction of elements: CaO - less than 2.0%; SiO ₂ 65.0-75.0%; Al ₂ O ₃ 10.0-16.0%; MgO - less than 1.0%; (Na ₂ O + K ₂ O) 9%; Fe ₂ O ₃ - less than 3.0%, having a low bulk density of 60-200 kg / m ³ and high heat-insulating properties (thermal conductivity 0.052-0.07 W / mK ⁰ ) is used as the skeleton of the mixture to create a porous (loose) structure ;

- dusty waste from the dust-free coke delivery unit serves to reduce the sintering of perlite grains and thereby allow a long time to preserve the porous (loose) structure of the mixture, and also due to its pseudo-fluidity - to increase the spreadability of the mixture on the melt surface, which excludes the manual leveling of the mixture with the aim excluding the presence of exposed sections of liquid melt.

The optimality of the claimed ratio is confirmed by the fact that the content of the dusty mixture in the dust-free coke production plant of 36.84-47.37 wt.% Corresponds to high heat-insulating properties and sufficient spreadability on the surface of the liquid melt, excluding the leveling operation. With an increase in the content of pulverized wastes of the dust-free coke delivery unit more than 47.37 wt.%, A slight increase in heat-insulating properties was observed with significant spreadability of the mixture, however, it led to a sharp carburization of the metal.

The content of pulverized wastes of the dust-free coke delivery unit of less than 36.84 wt.% Reduces the heat-insulating properties and the spreadability of the mixture on the surface of the melt.

The use of dusty waste from the dust-free coke delivery unit with a moisture content of more than 0.8% and a fraction of 0.1-0.25 mm less than 47% leads to a sharp decrease in the spreadability of the mixture.

In experiments, we used expanded perlite with a mass fraction of elements: CaO — less than 2.0%; SiO ₂ 66.0%; Al ₂ O ₃ 12.0%; MgO - less than 1.0%; (Na ₂ O + K ₂ O) 8.7%; Fe ₂ O ₃ - less than 3.0%, bulk density 60-70 kg / m ³ and dusty waste of the dust-free coke delivery unit of the fraction 0 ÷ 0.1 mm 6-10%, 0.1 ÷ 0.25 mm 47-50 %, 0.25 ÷ 0.5 25.8-26.8%, 0.5 ÷ 3.0 10.7-16.7,> 3.0 mm - less than 1.2%, with a carbon content of at least 82%, ash content - less than 9.7% and humidity less than 0.8%.

An experimental heat-insulating mixture was made by mixing the starting components in a mixing plant. To achieve a uniform composition of the mixture, the components were mixed for at least 30 minutes at a rotor speed of 22 rpm.

The use of a heat insulating mixture was carried out in steel pouring ladles in the production of steel grades st.3-5 sp., E76, E76F. At the end of the out-of-furnace treatment at the ladle furnace installation or steel degassing installation, immediately before the steel was delivered to the continuous casting machine, a heat-insulating mixture in the amount of 500 liters was set on the liquid melt mirror.

The use of a heat-insulating mixture in a steel pouring ladle during continuous casting of steel allowed to reduce the temperature gradient of the metal in the intermediate ladle to 7-9 ° C and, as a result, the rejection of metal due to violation of the temperature-speed regime by 0.7%, increase seriality by an average of 0, 5 smelting, reduce technological waste by 0.4 kg / t of steel.

Information sources

1. A.S. USSR 348288 B22D 27/04.

2. Patent RU 2175279, B22D 11/111.

Claims (1)

A heat-insulating mixture for warming steel in a steel pouring ladle containing expanded perlite and a carbon-containing material, characterized in that it contains dusty waste from the dust-free coke delivery unit of fractions 0 ÷ 0.1 mm - 6-10%, 0.1 ÷ 0 as a carbon-containing material , 25 mm - 47-50%, 0.25 ÷ 0.5 - 25.8-26.8%, 0.5 ÷ 3.0 - 10.7-16.7,> 3.0 mm - less than 1 , 2%, with a carbon content of at least 82%, with an ash content of less than 9.7% and a moisture content of less than 0.8%, and these components are taken in the following ratio, wt.%:
Expanded Perlite 52.63-63.16 Dusty waste dust-free coke dispensers 36.84-47.37