SU923723A1 - Slag forming mixture - Google Patents

Description

The invention relates to ferrous metallurgy, in particular to the continuous casting of steel with the protection of meniscus tal in the mold slag-forming materials.

There are various compositions of slag-forming mixtures, the main purpose of which is to isolate the metal meniscus from cooling and oxidation, as well as to assimilate non-metallic inclusions emerging from steel.

Slag-forming mixture containing, mica 15 “30, fluorspar 8-; 20, carbon-containing substance 2-15 "borax 0.2-15 and Portland cement (base) [13.

The main disadvantages of this mixture are, on the one hand, insufficient heat insulating and refining properties and the presence of harmful fluoride compounds. On the other hand, when casting steel with

With aluminum content, the dosing glasses in the tundish are tightened, which negatively affects the surface quality of the blanks.

In order to eliminate the tightening of glasses-dosers, in practice a part of aluminum (0.015 ~ 0.0-0 kg / t) is introduced into the crystallizer.

Use of highly basic Portland cement blends for assimilation! A1 ¢ 0 inclusions in these cases will be less effective than using silicate-based mixtures.

Closest to the offer is a silicate-based mixture consisting of wt.%: Fly ash 3060 (preferably 40-50) ’, thinner (CaG) 10 ~ 30 (preferably 10-25); Ma ^ CO ^ 15; CaCO ^ <15, cryolite <10; sodium borate 4 10; carbon additive (graphite) 2-8;

MpO - 4-12 (preferably 5 “Yu);

3

glass crushed into powder / 15 »Ge _g 0f / 5 C23.

The disadvantages of this mixture should include a high rate of melting, which leads to an increased consumption of the mixture and an increase in heat loss for melting. This is due to the fact that due to the low content in the mixture, graphite practically only serves as a lubricant. The increase in the consumption of graphite is associated with the danger of carburizing steel. The low content of volatile graphites in the main grades (up to 2%) is the reason for their low rate of growth, which does not allow improving the thermal operation of the charge.

The purpose of the invention is the optimization of the heat-shielding properties of the mixture on a silicate basis.

This goal is achieved by hem, that liquid glass was additionally introduced into the slag-forming mixture on a silicate basis, and high-ash graphite was taken as a carbon-containing additive in the following ratio of components, weight.% ·.

Silicate base 45 “6О

Thinners 15 "30

High ash

graphite (ash content

60-75%) u-zo

Liquid glass (module 2.31 "

2.6) 3 "8

The choice of high-ash graphite as an carbon-containing additive (ash content 60-75%, volatile content 20%, grade TKS) is due to a higher (10-15 times) burning rate as compared to low-ash, which ensures better thermal performance of the charge due to complete combustion of carbon, increasing the temperature and reducing the viscosity of the slag at the boundary with the metal. This will improve the assimilating properties of the slag and the surface quality of the blanks. In addition, slags

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high-ash graphite (5ί045 “53% content) replaces part of the silicate base. Regulation of the rate of reflow is determined by the presence of ₅ highly refractory graphite carbon shells around the mixture grains. To regulate the supply of air to the graphite shells and, consequently, their burning rate, liquid glass was introduced into the mixture. On the other hand, liquid glass additionally dilutes the mixture and prevents dusting of the mixture due to partial gluing of powder particles.

When choosing a brand of liquid glass take into account the data of laboratory experiments, from which it follows that the optimal module is 2.31-2.6 ₂₀ (grade 8 according to GOST 8264-56). An increase in the modulus leads to a significant decrease in the viscosity of the glass and worsens the conditions for its distribution in the mixture, reduces the adhesive properties of the glass and leads to dusting of the mixtures.

To determine the optimal composition of the mixture, it is taken into account that a rational rate of slag formation should ensure the uniform formation of ₃₀ on the slag garnishage with a thickness of 0.8-1.5 mm. Calculations show 'the thickness of the slag layer zhidkopodvizhnogo viscosity of 2-5 P, subrules for 1 min (pulling speed preforms 0.7 m / min) must coc ³⁵ nent 10-15 mm.

For the experiments selected 9 options slag-forming mixtures with different content of components. Experiments are carried out in 200 kg induction furnace ⁴⁰ . Experimental mixtures are placed on the surface of molten St 3 SP (layer thickness 55 "6O mm) and the furnace is turned off. Extracting the mixtures for 1 min. The thickness of the heat insulating and slag ⁴⁵ composition and the temperature at the interface between the layers are fixed.

The results of the experiments are given in the table.

five

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6

Composition Components, wt.% Layer thickness, mm Temperature at the border of Åev, ° С Silicate base Thinners * Liquid glass (module 2.4) Amorphous graphite liquid slag powdered ash content 65-70% ash content 17% Proposed one 40 15 five 40 - four 44 1520 2 40 34 five 21 - 20 ten 1485 3 45 15 eight 32 - 6 40 1520 four 55 12 3 ^thirty - 14 35 1520 five 55 20 five 20 - thirty 15Y 6 55 25 s 12 - 12 thirty 1510 7 55 27 eight ten - 14 25 15Y eight 55 thirty 9 6 ' - 20 ten 1490 * Famous 9 65 thirty -  - five 20 ten 1490

Potash, borax, cryolite.

The experiments show that at lower flow silicate filler ³⁵ ((bases) of at least 45%, which is compensated by increased consumption of high-graphite (40? Ec.%, The composition of 1), is not provided dostatochnyi layers of molten slag, and when povy * ^and shenii flow thinners (composition 2) deteriorate the heat-shielding properties of the mixture (ί _g p = 1485 ° C).

The presence in the mixture of high-ash graphite more than 30% by weight (composition 3) ⁴⁵

It leads to a dramatic slowing of slag formation and decrease the content of graphite to 8 vos.% (Formulation 8), despite the maximum content of waterglass, ⁵⁰ leads to elevated hydrochloric submelting rate and mixture flow rate, a decrease in their thermal insulation properties. These drawbacks are characteristic of the known mixture (part 9) · 55

The best indicators are mixtures of compositions 3 ^- 7 · In these cases, a rational rate of slag formation of mixtures, the maximum thickness of the heat insulating layer. The elevated temperature of the liquid slag provides the most favorable conditions for the adsorption of non-metallic inclusions.

Slag-forming mixture of the proposed sport has passed industrial tests with continuous casting of carbon steels. As a silicate base, waste frit foundry coatings with thinners are used. Satisfactory results were obtained for the quality of the ingot surface. Decrease in scrap metal is 5.6%. The consumption of mixtures is 0.3 "g / t, which is about 0.1 kg / t lower than when using a known mixture. Positive results obtained are explained by rational slagging and improved heat-shielding

| properties of the mixture of the proposed composition.

Claims (1)

Claim Slag-forming mixture comprising silicate base, thinners and ug ~ 923723 eight 7 Lerod-containing substance, characterized in that, in order to improve the heat-shielding properties, it additionally contains liquid glass, and as a carbon-containing 5 substance - high-ash graphite in the following ratio of components, wt.%: Silicate base 45-60 Thinners 15-30 High ash graphite (ash content 60-75%) 10-30 Liquid glass (module 2,312,61) 3-8