SU1592097A1 - Method of heating head part of steel ingot - Google Patents

Description

The invention relates to the steel industry. The purpose of the invention is to reduce shrinkage defects and increase the yield due to the regulated supply of heat to the head part of the ingot. The method includes filling the mold with liquid

The invention relates to ferrous metallurgy, in particular to methods for casting calm steel into ingots.

The aim of the invention is to reduce shrinkage defects and increase the yield due to the regulated supply of heat to the head of the ingot.

After the casting is completed, scale metal of 3-100 µm in the amount of 0.050.1% is poured onto the metal mirror, the profitable extension is covered with a steel sheet 1-10 mm thick, concave inward, aluminum is placed on its surface

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metal, warming the head of the ingot and covering the insulation plate. After filling the mold with liquid metal, the ingot head is initially insulated with a scale of 3-100 μm in an amount of 0.050.5% of the mass of liquid metal, covered with a melted down at a temperature of 20-100 ° C above the crystallization temperature of the liquid metal, corresponding to the heat exchange the Fourier criterion (between the scale and the plate), equal to 10-500, whose thermal parameters correspond to the Biot heat exchange criterion, equal to 0.005-0.15, after which a layer of aluminum in the amount of 20-40 is applied to the plate % of the mass of scale, and then the head of the ingot is again warmed with a mixture containing 5-15% of the oxidizer. 1'z ^ p. f-ly.

20-40% of the mass of scale, and then on the surface of aluminum put an additional layer of a mixture of scale and perlite in the amount of 5-10% by weight of aluminum.

The separate input of the oxidizing and reducing components of the exothermic mixture allows not only to regulate the heat fluxes during crystallization of the liquid metal in the mold, but also to use the oxidizing component (scale) as a warming mixture.

The fractional composition of 3-100 microns of scale is determined by the optimum values of „„ 1592097

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technological characteristics of the insulating material.

The use of scale fraction of less than 3 microns as a heat insulation material is not economically feasible, since the grinding costs outweigh the benefits of heat insulation of steel with crushed material, and the use of scale fraction of more than 100 microns as a heat insulation insulation leads to deterioration of the insulation properties of the mixture during the initial crystallization period metal and to increase the depth of the shrinkage shell.

The amount of liquid metal introduced onto the surface is determined by the conditions of heat transfer through the metal mirror to the atmosphere and

divides the heat flux directed to the metal mirror from the mixture due to the burning of aluminum in the scale.

Reducing the content of scale in the head of less than 0.05% by weight 25

liquid metal is impractical because the proportion of heat lost by the ingot due to deterioration of the primary thermal insulation of the liquid metal increases, an increase in the scale of oxides in the head part of more than 0.1% by weight of the liquid metal is impractical because the heat flux from the mixture to the metal mirror begins to exceed necessary for secondary melt35

the head of the ingot.

The need to use for covering the steel sheet is determined by the conditions for the ignition of the termite along the solidification of the melt.

The downward concavity of the slab ensures the preservation and non-spreading of liquid aluminum on the slab surface until it burns out (or melts).

With an insignificant shrinkage shell and early additional heat supply to the head part of the ingot due to the exothermic reaction of aluminum burning in scale,

only a small part of the heat flow of the exothermic reaction is used effectively to locate the head part of the ingot and fill the cavity of the shrinkage cavity, the rest of the heat flow through the liquid melt — the crystallizable metal of the mold wall along the entire height of the ingot is transferred to the environment.

With a significant amount of shrinkage shell and late additional heat supply to the head part of the ingot, it is possible due to significant differences in heat fluxes at the metal-liquid interface that the melt flows into the gaps between the walls of the mold and the ingot.

The time for supplying additional heat for the head part of the ingot is determined by the thickness of the steel sheet.

An increase in sheet thickness of more than 10 mm leads to its later melting, and vice versa, a decrease in the thickness of the steel sheet of less than 1 mm leads to an early melting of the steel sheet, as well as to a decrease in head trimming.

Example. In a broadened upward 8-ton mold after its filling, 4 kg of scale, whose fractional composition is 3 μm, are placed on the surface of the liquid metal. Thermal technical parameters of scale are as follows: density 1400 kg / m ³ , heat capacity 1200 J / kg'K, thermal conductivity coefficient 0.15 W / mK. After a period of time corresponding to the Fourier heat exchange criterion of 50, namely, for the given conditions, after 40 minutes, the scale is covered with a metal steel plate 1 mm thick, the thermal conductivity of which is 30 W / mK, the heat transfer coefficient is 30 W / mK which is applied to the surface of the plate 0.8 £ g of aluminum and a mixture of perlite is applied to it. and scale 0.04 kg, containing 5% scale.

Claims (2)

Claim : 1. The method of heating the head of a steel ingot, including the use of a thermite mixture of scale and aluminum for insulation of the poured metal, characterized in that, in order to reduce shrinkage defects and increase the yield of the fit due to the regulated heat supply to the head part of the ingot, dross fraction 3 -100 microns are poured onto the metal mirror after casting in the amount of 0.050.1% by weight of the ingot, the profitable extension is covered with a steel sheet, aluminum is placed on its surface in the amount of 20-40% by weight of scale, and m on the aluminum surface applied additional layer CME '1592097 C scale and perlite in the amount of 510% by weight of aluminum, and the amount of scale in the additional layer is 5-15 wt ^%. 2. The method according to: p. 1, characterized in that the lucrative over-the-end is covered with a steel sheet with a thickness of 1-10 mm, concave inward.