PL188412B1 - Thermally insulating powder - Google Patents

Abstract

Powder thermo-insulating used down warms lusrra silent steel and in kddzi foundry consisting out with roasted dolomite, perlite expanded, material carbon bearing, measure loosening and measure anti-dust, significant this that includes in percentages masses: 30-55% dolomite roasted, 15-30% perlite expanded, 5-15% material carbon bearing, 5-20% measure loosening and maximum 2% measure anti-dust.

Description

The subject of the invention is a heat-insulating backfill for thermal insulation of a liquid steel mirror in a casting ladle, applicable in the metallurgical industry.

There are known thermal insulation backfills, such as according to Polish patent specification No. 169128, containing 60-90% by volume of amorphous silica dust, 10-40% by volume of organic raising and insulation agents and up to 4% by weight of anti-dusting agents; and according to the Soviet patent no. 1503982 containing in its composition 30-40% by weight of graphite and 55-70% by weight of diatomite.

The known powders are acidic in nature, because their main component are materials with a high SiCty content. Acidic powders, in addition to the advantage of their good thermal insulation, have the disadvantage that when used for thermal insulation of liquid steel in a basic lined casting ladle, they reduce its service life.

The aim of the development of the heat-insulating backfill according to the invention was to reduce its aggressive chemical effect on the refractory basic lining of the casting ladle and to achieve good thermal insulation of the liquid steel mirror.

The alkaline backfill according to the invention with calcined dolomite is characterized by thermal insulation properties comparable to those of acid backfills.

The inventive heat-insulating backfill is used to insulate the liquid steel mirror in the casting ladle, consisting of calcined dolomite (containing in weight percent: MgO min. 30%, CaO min. 55%, Fe2O3 max. 6%), grain size 0- 4 mm; expanded perlite (containing in percent ma.sy: SiO; min. 66%, AL2O3 max. 18%, FiwOj max. 3%, CaO + MgO max. 6%, Na? C) + K2O max. 8%) with a bulk density below 160 kg / dm ³ ; carbon-bearing material (graphite or ground waste of graphite and graphite-carbon products with the trade names Separex and Karburyt, containing at least 80% by weight of the element C), a raising agent which is wood sawdust, roasted cereal waste or a mixture thereof; anti-dusting agent, which is a mineral oil, is characterized by the fact that it contains, in percent, by weight: 30-55% calcined dolomite, 15-30% expanded perlite, 5-15% carbon-bearing material, 5-20% raising agent and max. 2% anti-dust agent.

Roasted dolomite and expanded perlite are the basic thermal insulation components in the backfill. The carbon-bearing material increases the melting point of the powder and creates a reducing atmosphere above the surface of the liquid metal, the raising agent reduces its bulk weight and promotes the formation of a porous slag stump remaining at the bottom of the casting ladle after tapping steel therefrom. Mineral oil used as an anti-dusting agent reduces dust in the production of backfill and its application and prevents the hydration of calcium oxide contained in calcined dolomite.

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The combination of roasted dolomite with expanded perlite in the composition of the backfill has the advantage that the silica contained in the perlite reacts at high temperatures with the calcium oxide contained in the dolomite to form dicalcium silicate 2 CaO • SiO2. This silicate, while cooling down, undergoes a polymorphic transformation, which is accompanied by a significant increase in volume, causing dispersion decomposition of the sinter. As a result, the slag remaining at the bottom of the ladle after tapping the steel from it is brittle and its removal does not present technological difficulties.

This backfill solves the problem of thermal insulation of the steel mirror in the alkaline-lined casting ladle, because it has good insulating properties. Detailed tests of the backfill in the Carbitec furnace at 1420 ° C for 45 minutes showed that it had a final insulation value (KIW) of a maximum of 15 kW / m ² .

The backfill is prepared in the form of granules with a grain size of up to 6 mm. The backfill placed on the steel mirror in the amount of 1.2-1.5 kg / Mg ensures effective thermal insulation of the metal in the time necessary for its casting.

The thermal and insulation backfill contains in percentage by mass:

Example I:

- roasted dolomite 55%,

- expanded perlite 22%,

- graphite 10%,

- wood sawdust 5%,

- grain waste 9%,

- 1% anti-dust agent.

Example II:

- roasted dolomite 55%,

- expanded perlite 22%,

-Separex H%,

- wood sawdust 9%,

- grain waste 5%,

- 1% anti-dust agent.

Example III:

- roasted dolomite 50%,

- expanded perlite 22%,

- Carburite H%,

- wood sawdust 11%,

- grain waste 55 /,

- anti-dusting agent 10 ^/ o.

The composition in examples 1 and 3 is optimal for insulating steel in a 150 Mg capacity ladle.

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The Publishing Department of the Polish Patent Office. Circulation 50 copies. Price PLN 2.00

Claims (1)

Patent claim Thermal insulation backfill used for warming the liquid steel mirror in the casting ladle, consisting of roasted dolomite, expanded perlite, carbon-bearing material, raising agent and anti-dusting agent, characterized by the fact that it contains in percent by weight: 30-55% calcined dolomite, 15-30% expanded perlite, 5-15% carbonaceous material, 5-20% raising agent and a maximum of 2% anti-dusting agent.