SU1125092A1 - Heat-insulating mixture for steel teeming - Google Patents

Abstract

HEAT-INSULATING MIXTURE I FOR STAINLASTING, including vermiculite, graphite, characterized in that, in order to improve the surface quality of the ingots, as well as yield, by improving the thermophysical properties of the mixture, it additionally contains coal ash and carbonates of alkali or alkaline earth metals in the following ratio of ingredients , wt.%: Vermiculite 5-30 Graphite 3-25 Carbonates of alkali metals or alkaline earth metals 2-15 Coal ash 50-80

Description

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The invention relates to ferrous metallurgy, in particular to compositions of heat insulating mixtures, using ix when casting steel in the following. A known mixture is a mixture containing amorphous graphite and expanded perlite Cl 3.

The thermally insulating mixture for steel casting, including vermiculite and graphite 2, is the closest to the invention in technical essence and the achieved result. 3 The disadvantages of the mixtures are: high (1480-1520 ° C) melting point, insufficient slag liquid mobility and, as a result, poor quality ingot surfaces and low elongation.

The aim of the invention is to improve the surface quality of the ingots, as well as the yield of a suitable one by improving the thermophysical properties of the mixture.

The goal is achieved by the fact that the heat-insulating mixture for steel casting, including vermiculite, graphite, additionally contains coal ash and carbonates of alkali or alkaline earth metals in the following ratio of ingredients, wt.%:

Vermiculite 5-30 Graphite3-25

Alkali or alkaline earth metal carbonates (2–15 Coal ash 50–80 forming molten slag melt already at the very beginning of steel casting.

When the content of a mixture of carbonates of alkali and alkaline-earth metals in the amount is less than 2% by mass, the melting temperature of the mixture is high to. Increasing the carbonate content in excess of 15 wt.% Has a significant effect on the melting point of the mixture and only leads to an increase in the cost of the latter.

250922

Ash - waste from the combustion of coal fuel is a filler, as well as a supplier of oxides (SiOj, CaO, FeO, etc.), which can be used for intensive formation at temperatures of cast metal in a mold.

The content of coal ash in the composition of the proposed composition O is determined by the optimal values of the physicochemical characteristics of the mixture and the slag melt obtained from it.

The introduction of vermicu5 into a mixture contributes to the enhancement of the heat insulating properties of the composition. When the content of vermiculite is less than 5 wt.%, The heat insulating properties of the mixture are reduced. When the content of vericulus in an amount exceeding 30 wt.%, The heat-insulating properties of the mixture remain practically unchanged, but the cost of the mixture increases.

Graphite in the proposed composition 5 is a material that prevents sintering of the mixture at the moment of contact with the liquid metal, which contributes to the creation of conditions for obtaining a high-quality surface of the ingots. When Q content of graphite in an amount less than 3 wt.%, The heat insulator "mixture is prone to sintering. Increasing the content of graphite in excess of 25% by weight creates the danger of carburizing the metal of the ingot.

The compositions tested heat insulating. The mixtures for steel casting are presented in table 1.

Data characterizing the properties of the mixtures indicated in Table 1, as well as slags produced from them, are presented in Table 2.

The values of thermal conductivity coefficients of the proposed and known mixtures are presented in Table 3.

As follows from the data presented in Tables 2 and 3, the melting point of the mixture, the temperature of formation of a drop of slag, and the heat conductivity of the proposed mixture are significantly lower than those of the known mixture, which contributes to the achievement of the stated purpose of the invention — to improve the quality of the ingot surface and yield them . The proposed composition of the mixture is carried out when casting bearing steel at Dneprospetsstal plant into ingots weighing 3.6 tons. The temperature of the metal during casting is ISZO-ISSO C. An analysis of the design of the metal by surface defects shows an increase in the yield of 3% when casting with the proposed mixture. 3.5%. The quality of the metal by macrostructure and contamination of the mixture, and

These non-metallic inclusions remain unchanged. The results of the quality of the metal according to 63 experimental heats are presented in Table 4.

When using the proposed mixture, in the conditions of the Dneprospetsstal plant, the expected economic effect will be 15 000 rubles per year.

Table 1

10 (soda NajCOj) 2 Same 7 - 15 - 15 - 10 - 2 (noTam-KjCX),)

7 (K, CO,)

7 (known to CaCO)

7 (magnesite-MgCOj)

15 (witerte-BaCOj)

Table 2

Continuation of table 2

6 7 8 9 10 11

0.86

13 13 13 13 13 13 14 0.82 0.80 0.85 0.84 0.86 3.37 zvesta

eight

1125092 Continuation of table 4

2.66

2.3

2.45

2.65

2.7

2.9

5.0-6.0

Claims (1)

'HEAT-INSULATING MIXTURE I FOR CASTING STEEL, including vermiculite, graphite, characterized in that, in order to improve the surface quality of the ingots, as well as yield by improving the thermophysical properties of the mixture, it additionally contains coal ash and alkali or alkaline earth metal carbonates in the following ratio ingredients, May ·% · Vermiculite Graphite Carbonates of alkali or alkaline earth metals Coal ash