SU1133299A1 - Slag forming mix for steel casting into molds - Google Patents

Abstract

SLAG FORMING MIXTURE. STEEL SPRAYS IN ITS PICTURES, including: schica silicocalcium, fluorspar, silicate lump, characterized in that, in order to improve the surface quality of the ingot and reduce the nonmetallic inclusions in the steel, the mixture additionally contains cryolite and coke with the following ratio of ingredients, wt.%: Silicocalcium 8-12 Fluorspar 28-32 Cryolite. 13-17 Cox3-7 Silicate Block Rest

Description

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1C

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The invention relates to ferrous metallurgy and can be used in casting steel into molds.

The known mixture for steel casting containing fluorspar, nepheline, silicate lump and wood sawdust lj. The disadvantage of this mixture is that wood sawdust, when using the composition, produces a significant amount of harmful gases, as a result of which the working conditions on the casting platform deteriorate.

Closest to the invention in its technical essence and the effect achieved is an exothermic slag-forming mixture, used in steel casting and containing silicocalcium, margan), ore, fluorspar and silicate lump G21,

A disadvantage of the known mixture is that it is not suitable for use in casting stainless steels. The presence in this mixture of manganese ore leads to the oxidation of titanium and chromium contained in the liquid steel, the oxides of which increase the viscosity of the slag cover, which leads to the formation of defects on the surface of the ingot, as well as an increase in the content of the ingot of nonmetallic inclusions.

The aim of the invention is to improve the surface quality of the ingot and to reduce non-metallic inclusions in steel.

In order to achieve this goal, the spack-forming mixture for casting steel into molds, including silicocalcium, fluorspar, silicate lump, additionally contains cryolite and coke in the following ratio of ingredients, wt.%:

Silikokaltsiy8-12

Fluke spar28-32

Cryolit13-17

Cox3-7

Silicate cubeOstal

a little

By chemical analysis of stainless steel samples, it has been found that non-metallic inclusions are mainly refractory oxides of aluminum, chromium and titanium. Their content in non-metallic inclusions is, in wt.%: A120 ,, 15-50; 5-30; Tic2 10-30. In the process of casting, these oxides form refractory clusters, which, located in the surface layer of the ingot metal, reduce its quality and, as a consequence, contribute to the appearance of defects in the cold-rolled sheet. By creating conditions for converting refractory compounds (clusters) to low-melting with a temperature of their melting below the temperature of solidification of steel at 350-450s. Oxides of aluminum, chromium and titanium in the presence of a sufficient amount of free oxides of silicon. At the required temperature, it easily forms complex silicate inclusions with a low melting point. Consequently, the predominant component in the refining mixture should be silica, introduced into the mixture in the form of a silicate block.

However, lowering the silicon oxide content in the slag leads to an increase in the viscosity of the latter. The elements contributing to the reduction of the viscosity of the slag bed are fluorine, sodium and potassium. These elements are introduced into the slag-forming mixture in the form of fluorspar and cryolite.

When the content in the mixture of fluorspar is less than 28 wt.%, The resulting slag has a high viscosity. Introduction to the mixture of fluorspar in an amount greater than 32 wt.% 5 creates the danger of harmful fluorine compounds entering the atmosphere of the shop.

Cryolite with a melting point of 1 SHO-s is an effective solvent of fused alumina and titanium and at the same time performs the function of liquefying the solids of the melt pack. When the content of cryolite in the mixture in an amount less than 13 wt.%, The effect of reducing the viscosity of the slag and the assimilation of non-metallic inclusions is not achieved. The content of cryolite in the mixture in the quantity greater than 17 wt.% Does not have a significant effect on the viscosity of the slag and contributes to an increase in the cost of the slag-forming mixture.

The introduction of coke into the composition of the slag-forming mixture contributes to a decrease in the interfacial tension between the metal and the slag.

Taking into account that carbon-containing materials have high thermal conductivity, and carbon has low solubility in liquid packs, coke eliminates sintering of the components of the mixture at the moment of its addition to the metal mirror in the mold. All this allows to quickly equalize the temperature gradient over the entire layer of liquid slag, making it homogeneous from the very beginning of the casting process, as a result of which the slag covers the walls of the mold with an even layer, creating a condition for uniform crystallization of the forming ingot crust, which contributes to obtaining a quality surface of the cast metal. When the coke content in the mixture is less than 3 wt.%, Its sintering is observed in the process of filling to the metal mirror. A coke content in a mixture of more than 7% by weight is undesirable, since, in this case, there is a danger of carburizing the metal of the ingot. Instead of coke, graphite, anthracite and other carbon-containing materials can be used, the years of which do not exceed 8%. For the purpose of rapid heating and dispersion of the mixture, silicocalcium was introduced into its composition. The amounts of silicocalcium as well as silicate lump and fluorspar are determined by the basicity (CaO / / SiOrt) of the obtained slag melt. It is established that the absorption of slag refractory non-metallic inclusions of pyumini, titanium and chromium is the best basicity of slag within 0.35 R, 55. When the content in the mixture of silicocalcium in an amount of less than 8 wt.%, The formation of slag and melt slows down, which can lead to the formation of surface defects in this part of the ingot. Increasing the content of silicocalcium over 12 wt.% Increases the cost of the mixture, without significantly affecting the properties of the slag melt and the quality of the ingots. In tab. 1 shows the compositions of the known 1 and proposed 3-5 mixtures. 1 994 All raw materials for preparing the mixture are crushed to a particle size of less than 200 mesh. They are thoroughly mixed and packaged in paper or plastic bags for transportation and backfill to the bottom of the molds before steel is cast. It is possible to fill the mixture with the help of tools or luckerite scoops. In tab. 2 presents the results of tests of the mixtures given in table. 1, when casting stainless steel grade 12x18H10T into molds for ingots weighing 13100 kg. Given in Table. 2, the data suggests that the use of the proposed mixture for casting stainless steels makes it possible to obtain cleaner steel by nonmetallic inclusions and reduce the number of rolled defects. When using mixture 2, as compared to the known 1, the ingot surface deteriorates both by the number of clean slab faces and by the general marriage of the cold-rolled sheet, due to the viscosity of the slag melt and its considerable adhesion to the mold. The use of the mixture 6 does not allow to reduce the amount of nonmetallic inclusions in steel compared to the known, since the increased basicity of slag (1.11) does not contribute to the absorption of refractory inclusions of aluminum, titanium and chromium. Therefore, the optimum formulations of the proposed pshakoobrazuyu mixture are compounds 3-5. Thus, the proposed mixture forms an improvement in the surface quality of the ingot and reduces non-metallic inclusions in steel. The application of the invention allows to obtain an economic effect in the amount of 6.51 rub / t steel.

Table 1

14

18

6

eight

ten

12

14

Koltschestvo viscosity of the speck when, Pa metal inclusions,% to metal

0,0152

1.8

0.0082 3.2

0.00627 1.3

0.00429 0.8

0.00742 0.6

0,0135 0.5

64

56

eleven

48

13

40

15

32

17

24

nineteen

table 2

Quality slab and cold rolled sheet

Marriage sheet,%

Clean slab faces,%

1,3

1.6

0.7

ABOUT

0.6

0.8

Claims (1)

SLAG-FORMING MIXTURE FOR PREPARING STEEL INTO TARGETS, including silicocalcium, fluorspar, silicate block, characterized in that, in order to improve the quality of the surface of the ingot and to reduce non-metallic inclusions in steel, the mixture additionally contains cryolite and coke in the following ratio of ingredients. %: Silicocalcium Fluorspar Cryolite Coke Silicate block 8-12 28-32 13-17 3-7 Rest 299