SU1062278A1 - Slag-forming mix for metal treatment - Google Patents

Abstract

Slag-forming mixture for metal treatment, including fluorine-containing component and blast-furnace slag, characterized in that, in order to reduce the consumption of the mixture and improve the quality of the metal, it additionally contains the following components, in wt.%: Fluoride containing 15-30 Known for 40 40 Blast furnace slag Else

Description

The invention relates to ferrous metallurgy, specifically to the treatment of metal with slag-forming mixtures in a ladle and mold.

Known slag-forming mixture for casting steel of the following composition, weight. %: fluorite 18-25; soda ash 3-10 and blast furnace slag else ij.

The disadvantages of the mixture are contained in the sloughness of the composition and its preparation, including heat treatment, the difficulty of maintaining a constant composition of the liquid slag due to thermal dissociation of fluorite and soda.

Also known is synthetic slag for treating a metal of a simpler composition, comprising 75-90% of a blast-shpak and 10-25% of alkali metal oxides 2.

However, the resulting liquid slag is characterized by a significant fluctuation of the composition, since the degree of assimilation of volatile alkali metal oxides varies widely depending on the conditions of use of this mixture.

The closest in composition and achievable effect to the proposed is a slag-forming mixture for metal treatment, consisting of blast-furnace slag (80-90 wt.%) And fluorine-containing component (1020 wt.%).

However, testing the known mixture on individual steel ingots revealed an increase in the sulfur content to 0.001-0.003%, which lowers the quality of the metal being processed. This is due to the high sulfur content in the blast furnace slag.

The Kremlin also needs a high consumption of a known mixture for processing steel when casting from above — at least 3.0 kg / ton of steel. But even with such a flow, the steel stream falling from the ladle drives the slag away from the center to the edges of the mold and the ingot mirror is exposed. The liquid steel undergoes secondary oxidation with oxygen of the atmosphere and the quality of the steel decreases.

The purpose of the invention is to reduce the consumption of slag-forming mixture and improve the quality of the metal. I.

The goal is achieved by the fact that the slag-forming mixture for metal treatment, including the fluorine-containing component and the blast-furnace slag, additionally contains limestone with the following ratio of components, in%:

fluoride containing ca 15-30

Known to 40-60

Blast slag Else

Introduction to the composition of the slag-forming mixture of limestone, thermal

the dissociation of which in the resulting liquid slag from the offered one is accompanied by foaming, makes it possible to reliably cover the metal and protect it from oxidation with a lower consumption of the mixture than for the known composition.

Data on the composition and properties of the tested mixtures are presented in Table 1.

0

Compared to slag obtained from a known mixture, the bulk density in the liquid state decreases by a factor of 3 to 7.

The basicity of the mixture proposed

5 compostase ranges from 2.0 to 3.4, which excludes the possibility of sulfur transfer from slag to metal.

In tests of the proposed slag-forming mixture, in addition to calcium fluoride, sodium fluoride and cryolite were used as a fluorine containing component. At the same time, there was no significant difference in the properties (melting point, viscosity, ability to foaming) about 5 times the amount of slags.

Since sodium fluoride and cryolite are scarce and expensive, the proposed slag-forming mixture is economically viable. use natural calcium fluoride.

The experiments were carried out in a Tamman laboratory furnace, slag-forming mixtures were melted in molybdenum crucibles, and the melting rate was measured by a platinum – rhodium thermocouple. The ability to foaming is defined. by measuring the thickness of the slag foam and visual observation.

0

The melting point of mixture 1 is, and mixtures 3-8 are; respectively 1180-1120 ° C. A mixture2 with a calcium fluoride content of less than 15% and a limestone of more than 60% has a mp. 1280s and for use5

neither expounded | The test when casting steel from above is unsuitable (it is known that the acceptable melting point under these conditions is 1220 ° C).

0

With an increase in the calcium fluoride content of more than 30% and with a lime content of less than 40%, the capacity for stable foaming decreases, and the melting point of the mixture decreases slightly. To use such a mixture is not economically feasible, different.

Blast furnace slag in the amount of 20-40%

0

33 serves as a filler and increases the stability of slag foam within these limits.

The optimal composition of the slag-forming mixture contains 20% calcium fluoride, 30% blast furnace slag and 50%

5 limestone (mixture G) and determined from the conditions of high foaming ability, low melting point () and economic feasibility. The thickness of the slag foam increased in comparison with the known mixture by 6.6 times at the same flow rate of the mixture. Example. The experiments used ground lump fluorite (contains: CaF2 60 and SiO2 20) fractions 03 MM, granulated blast furnace slag (CaO 40, SiO 35 and S 0.9) fractions 0-4 mm, used as a filler, and ground dried unfired known to / containing 50% CaO fraction 0-3 mm. The experiments were carried out during the casting of steel 08U melted in a two-bath furnace. The metal was poured into molds of the type CNT-18 t from a 300-capacity ladle through a glass with a hole in the channel of 80 mm.

Table 1 The results of the experiments are given in table 2. The results of the experiments show that when casting using a known mixture, significant oxidation of aluminum occurs (by 22.5%), while using the mixture of the proposed composition, the oxidation of aluminum in the waste is insignificant (5.0%), respectively became aluminates. High protective efficiency was also achieved when the mixture of the proposed composition was consumed two times less than the known one. The economic efficiency of using 1 ton of the proposed slag-forming mixture for steel treatment in comparison with the known one was 13 rubles and was due to the specific consumption per ton of steel.

85 25

25 40

35 30

20 30

1.04

3.95 missing

Very weak

3.40

Weak 2.00

Is stronger

2.24

2.55 strong

Very strong

2.54 2.00

Less strong 0.07 0.01 0.28 0.040 1 3.0 {known) 1.5 0.07 0.01 0.28 0.040 0.07

Table 2 0.07 0.01 0.28 0.031 0.01 0.28 0.038

Claims (1)

SLAG-FORMING MIXTURE FOR METAL PROCESSING, including fluorine-containing component and blast furnace slag, characterized in that, in order to reduce the consumption of the mixture and improve the quality of the metal, it additionally contains limestone in the following ratio of components, wt.%: Fluorine-containing composition ♦ barking 15-30 Limestone 40 * 60 Blast furnace slag Else