RU2345864C2 - Investment for filling of steel-pouring channel of ladle - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: investment contains, wt %: 9.99-72.80 of quartz-bearing component with containing of SiO₂ not less than 96 wt % and grain size 0.1-1.0 mm; 14.98-77.67 chromite concentrate and/or chromite ore with content of Cr₂O₃ not less than 35 wt % and grain size 0.1-1.0 mm; 0.05-9.70 of graphite with grain size less than 0.1 mm; 0.01-2.91 olein and/or stearic acid.

EFFECT: fluidity increasing of investment, density increasing of its stowage into free poured condition, hardening againstk iron-containing melts, probability reduction of mixture sintering ability.

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Description

The invention relates to refractory unshaped materials used in the metallurgical industry, in particular, as a refractory material for filling a ladle’s steel-pouring channel to prevent premature exit of the metal from the ladle and cooling of the metal in the channel (channel “overgrowing”) during the accumulation, processing and transportation of metal in the bucket.

Known refractory mixture for filling the steel outlet of the ladle according to the patent of Russia No. 2242441, С04В 35/00, 2004, containing, wt.%: Milk-white quartz with a grain size of 1-3 mm with a SiO content _of 95.5-98.5% 97- 99 and graphite crystalline foundry brand GL-1 1-3.

Also known is the filler of the outlet channel of the steel pouring ladle according to the application of Russia No.2000116970, B22D 41/16, 2002, containing, wt.%: Quartz sand 96-99 and pyrolytic carbon - the rest.

As the closest analogue, you can choose a refractory mixture for filling the outlet channel of a steel pouring ladle according to Russian patent No. 2228819, B22D 41/46, 2004. It contains a quartz-containing component with a content of SiO _{2 of} at least 96 wt.% In the form of vein quartz and flake graphite in an amount of 1-4 wt.%. At the same time, vein quartz has a grain size of more than 1.0 mm 95-96 wt.%, And scaly graphite has a grain size of up to 0.5 mm.

The main disadvantage of the prototype is the increased tendency of the refractory mixture to sintering in the steel pouring channel and the likelihood of its interaction with the melt, the consequence of which is the overgrowing of the steel pouring channel and arching in the mixture layer above this channel. These shortcomings are associated with:

- insufficient fluidity and insufficient packing density of the refractory mixture in a loose state due to its large grain composition;

- the tendency of the mixture to refract during transportation, storage and filling the mixture into the steel pouring channel due to the large grain composition, which results in the possibility of direct contact of the grains of the quartz-containing component with each other and with the iron-containing melt with the formation of fusible but highly viscous melts that impede the free flow of the mixture from the steel-pouring channel

- the possibility of burning particles of graphite in the process of heating the ladle before casting, which, in turn, leads to sintering of the mass in the steel pouring channel;

- the possibility of the manifestation of the effect of "arch formation" at casting temperatures of the metal due to the residual expansion of the quartz-containing component during its polymorphic transformations;

- the formation in a free-sprinkled refractory mixture of a large number of pores that are not filled at metal pouring temperatures with a liquid ceramic phase or graphite, into which molten metal or slag can penetrate with the formation of highly viscous compounds that impede the free pouring of the mixture from the steel pouring channel when it is opened.

The problem to which the invention is directed, is to increase the reliability of the opening of the steel-pouring channel of the ladle, increase its productivity and reduce metal loss during casting.

The technical result achieved by the invention consists in increasing the fluidity of the refractory mixture, increasing the density of its laying in a freely sprinkled state, increasing the resistance of the mixture to the effects of iron-containing melts, reducing the likelihood of arch formation and sintering of the mixture and ensuring its unhindered precipitation from the steel pouring channel when it is opened without application mechanical impact and burning with oxygen.

The specified technical result is achieved in that the refractory mixture further comprises a chromite concentrate and / or chromite ore with a Cr ₂ O ₃ content _of at least 35 wt.%, And a grain size of 1.0-0.1 mm and oleic and / or stearic acid, the quartz-containing component has a size grains 1.0-0.1 mm, and graphite has a grain size of less than 0.1 mm, with the following ratio of components, wt.%:

quartz-containing component with a content of SiO _{2 of} at least 96 wt.% 9.99-72.80 chromite concentrate and / or chromite ore with a Cr ₂ O ₃ content _of at least 35 wt.% 14.98-77.67 graphite with a grain size of less than 0.1 mm 0.05-9.70 oleic and / or stearic acid 0.01-2.91

The essence of the invention lies in the fact that the introduction of the specified chromium-containing component into the composition of the refractory mixture increases the refractoriness and resistance of the mixture to the effects of iron-containing melts, reduces the tendency to form and sinter under the influence of high temperature due to the exceptional chemical inertness and high melting point of chromium oxide Cr _{2 itself} O ₃ , and its compounds with iron oxide (various chrome spinels - the main minerals of chromite raw materials) and silicon oxide.

Moreover, in chrome spinel with a Cr ₂ O ₃ content _of more than 35 wt.%, The melt begins to appear at temperatures above 1700 ° C. In the presence of SiO _2, chrome spinels do not form chemical compounds and solid solutions with it, and at temperatures above 1840 ° C in the mixture of the chromium-containing component and quartz there are only two immiscible melts that practically do not interact with each other, which ensures the absence of sintering of the mixture at metal pouring temperatures (1600-1800 ° C).

When the components of the refractory mixture interact with oxides and metallic iron at high temperatures (both the chromium-containing component and the quartz-containing component), the molar volume increases due to changes in the valencies of iron and chromium oxides and due to the spinel formation process, which also prevents the mixture from sintering and penetrating into its volume of iron-containing melts.

The presence of graphite and secondary carbon in the composition of the refractory mixture at its service temperatures leads to its interaction with the components of the refractory mixture with the formation of chromium, iron, aluminum and silicon carbides and oxycarbides, which also have high melting points, high resistance to iron-containing melts and form with increasing volume, which is an additional obstacle to sintering of the refractory mixture.

Introduction to the composition of the refractory mixture of oleic and / or stearic acid as a surfactant from a number of organic fatty acids ensures uniform distribution of graphite over the surface of the mineral part of the mixture due to the low surface tension of the above acids and the manifestation of capillary forces on the surface of porous bodies, which increases the fluidity and the packing density of the mixture grains due to the appearance of a double electric layer on the surface of mineral particles and provides the appearance of additional finely dispersed carbon on the surface of the mineral particles of the mixture during its heating due to the coking process of organic acids.

The above properties are especially manifested with the indicated grain composition, since if the mixture contains thin and ultrafine fractions (less than 0.1 mm) of inorganic materials, agglomeration and coagulation effects of the mixture may occur, worsening its fluidity and uniformity of laying, as well as subsequent sintering of the mixture during the process her service.

If the mixture contains grains larger than 1.0 mm in the mixture, the processes of refraction begin during the transportation and laying (filling) of the mass, which significantly degrades the performance of the mixture and significantly increases the pore size in the layer of the freely filled mass (as is known, the maximum pore size in the dispersed the system will depend on the average grain size of the powder according to the empirical ratio d _pore ~ 0.15D ₃ ), which facilitates the penetration of the molten metal into the layer of bulk material.

Graphite is used as a highly refractory component, which is highly resistant to iron-containing melts and does not sinter at the metal pouring temperature in a finely dispersed state, which allows the use of fine graphite particles (less than 0.1 mm) to fill the pore space of a free-sprinkled refractory mixture and form a mixture-non-wettable iron-containing melts.

The use of a quartz-containing component with a SiO ₂ content _of less than 96 wt.% Leads to the appearance of a large amount of impurity components in the mixture — alkaline oxides, calcium, magnesium oxides, etc., which sharply reduces the sintering temperature of the quartz-containing component and the entire refractory mixture.

The presence of a specified quartz-containing component in the mixture of less than 9.99 wt.% Significantly increases the thermal conductivity of the mixture and almost completely reduces the effect of self-sealing of the mixture during its heating due to thermal expansion of the quartz-containing component. An increase in the content of the quartz-containing component in the mixture of more than 72.80 wt.% Leads to the manifestation of the effect of the formation of the mixture (hang) at the time of opening of the casting channel.

The presence of a chromite concentrate and / or chromite ore in a mixture of less than 14.98 wt.% Does not provide a uniform and complete distribution of this component over the volume of the mixture, which leads to an increase in its open porosity at high temperatures and wettability of the mixture by iron-containing melts and chemical interaction between the mixture and the melt ( sintering of the refractory mixture in the channel).

The presence of a specified chromite-containing component in the mixture of more than 77.67 wt.% Leads to a significant increase in the thermal conductivity of the mixture, which also leads to increased sintering of the mixture and an increase in its cost.

If the mixture contains less than 0.05 wt.% Graphite, it does not completely cover the grains of the mineral part and does not fill the thin pores in the structure of the freely sprinkled mixture, which leads to the penetration of the iron-containing melt into the steel pouring channel and freezing of the melt in it (“stenosis” of the steel pouring channel).

In the presence of graphite in the mixture of more than 9.70 wt.%, The thermal conductivity of the mixture increases significantly, its mixing is not ensured (its refraction begins), which also leads to the loss of fluidity of the mixture and its sintering during service.

The presence in the mixture of the specified surfactant from a number of organic fatty acids of less than 0.01 wt.% Does not allow to obtain the required rheological properties of the mixture due to incomplete wetting of the surface of the granular part, and the content of the above component is more than 2.91 wt.% Leads to its release in the mass in free form, which negatively affects the fluidity of the mass and contributes to the coagulation of the granular part of the mass during its transportation and filling into the casting channels of the thermal unit.

As a quartz-containing component, you can use milk-white quartz, quartzite, quartz sand, vein quartz, rock crystal and other quartz-containing materials with a content of SiO _{2 of} at least 96 wt.%.

The chromite concentrate is an enriched chromite ore and contains Cr ₂ O ₃ not less than 35 wt.%, Fe ₂ O ₃ not more than 18 wt.% With a ratio of Cr ₂ O ₃ / Fe ₂ O ₃ / Al ₂ O ₃ = 1.3 ÷ 2.0 /1.0/1.0. It is possible to use directly chromite ore as a natural material, subject to the above ratios.

The technical result will be achieved with the combined use of chromite concentrate and chromite ore.

As graphite, you can use crystalline, flake, cryptocrystalline, artificial and other types of graphite.

The invention does not change from the joint use of oleic and stearic acids.

To obtain the inventive refractory mixture using the following starting materials:

- Chromite concentrate ХК1, ХК2 according to TU 0741-002-51824642-2003

(Cr ₂ O ₃ 45-50 wt.%, Fe ₂ O ₃ 15-20 wt.%, Al ₂ O ₃ 16-25 wt.%), Which is crushed to a grain size of 1.0-0.1 mm;

- Chromite ore DH-2 according to TU 14-9-249-83 (Cr ₂ O ₃ 48-52 wt.%, Fe ₂ O ₃ 13-22 wt.%, Al ₂ O ₃ 16-25 wt.%), which is crushed to a grain size of 1.0-0.1 mm;

- Quartz sand of the MKO brand according to TU 571726-002-45588031-01 (SiO ₂ -98.4 wt.%, R ₂ O-0.05 wt.%, Fe ₂ O ₃ -0.16 wt.%, CaO-0.04 wt.%), which is crushed to a grain size of 1.0-0.1 mm;

- Ground quartzite, grade ZKV-97-T, according to TU 14-202-31-90 (SiO ₂ -97.8 wt.%, R ₂ O-0.15 wt.%, Fe ₂ O ₃ -0.26 wt.%, CaO-0.14 wt. .%), which is crushed to a grain size of 1.0-0.1 mm

- Crystalline graphite GL brand according to GOST 5279-74 (ash content not more than 18 wt.%, Humidity not more than 1 wt.%), Crushed to a grain size of less than 0.1 mm;

- Flake graphite grade GT-1 according to GOST 4596 (ash content not more than 10 wt.%, Humidity not more than 1 wt.%), Crushed to a grain size of less than 0.1 mm;

- Oleic acid brand "B" TU 10-04-02-82-91;

- Technical stearic acid GOST 6484-96.

The process of preparing the refractory mixture consists in sequential mixing in the mixer with forced movement of the activators of the starting components according to the following scheme:

- chromite concentrate and / or chromite ore and a quartz-containing component are loaded into the mixer and mixed for 3-6 minutes;

- oleic and / or stearic acid is added and the mixture is mixed for 5-8 minutes;

- graphite is added and the mixture is mixed for 7-10 minutes.

The refractory mixture is packaged in polyethylene or jute bags of 5-10 kg.

The finished refractory mixture is a gray-brown granular material. The bulk density of the mixture is 2.6-3.6 g / cm ³ , the refractoriness of the mass is more than 1740 ° C, the fluidity is 33-41 s, the sinterability is more than 1670 ° C.

Specific compositions of the refractory mixture are shown in table 1, and the properties of the refractory mixture are presented in table 2 (Appendix 1)

Bulk density was determined according to GOST 9758-86.

The refractoriness of the mixture was determined according to GOST 4069-69.

The fluidity of the mixture was determined according to GOST 20899-98.

Sintering ability of the mixture was determined according to GOST 23409.20-78.

As can be seen from table 2, the patented composition provides a greater bulk density and greater fluidity and, therefore, a high packing density of the mixture in a free-sprinkled state, has a high refractoriness and sintering temperature, which ensures the absence of sintering of the mixture in the steel pouring channel of the steel pouring ladle.

The developed refractory mixture was tested during steel casting at NTMK OJSC, Nizhny Tagil, OJSC Seversky Pipe Plant, Polevskoy, FSUE Uralvagonzavod, Nizhny Tagil. The use of the developed refractory mixture provided 80-95%, depending on the grade of the metal being cast, rashes of the mixture without mechanical impact and burning with oxygen. In the remaining cases, a simple mechanical effect was sufficient without burning with oxygen. The use under the same conditions of mixtures manufactured by MMK OJSC, similar to the prototype (quartzite - 97 wt.%, Graphite - 3 wt.%), Provides 50-65% of cases of rash of the mixture without any effect and 35-50% of cases with burning with oxygen up to 10-15 s.

Thus, a refractory mixture has been developed for filling the ladle’s steel-pouring channel, which has improved rheological properties and provides, during operation, a decrease in the likelihood of sintering, a decrease in the interaction with iron-containing melts, a reduction in arching, and an increase in the fraction of the guaranteed unhindered pouring of the mixture from the steel-pouring channel.

Annex 1

Table 1. The composition of the refractory mixture Components Compositions, wt.% one 2 3 four 5 6 7 8 9 10 eleven 12
(prototype) Chromite concentrate 77.67 - 60.0 - 14.98 - 25.0 - 64.5 54.0 45.0 - - Chromite ore - 63.0 - 46.0 - 57.0 28.5 58.0 - - 24.0 - - Quartz sand of the MKO brand 17.32 34.04 - - 72.41 - - 37.0 - 42.0 18.5 99.0 96.0 Ground quartzite of the ZKV-97-T brand - - 38.7 50.5 - 40.15 39.3 - 33.45 - 4.5 - - GL brand graphite 5.0 - 1.0 - 9.70 - - 3.3 - - 5.0 - - GT brand graphite - 1 - 0.05 - 3.5 - 2.5 6.5 - 1.8 2.75 1.5 1.0 4.0 Oleic acid brand "B" 0.01 - 0.3 - 2.91 0.15 0.4 1.7 0.1 - 0.7 - - Technical stearic acid - 2.91 - 0.15 - 0.2 0.3 - 0.15 1.25 0.8 - - Table 2. Properties of the compositions of the refractory mixture Indicators Compositions, wt.% one 2 3 four 5 6 7 8 9 10 p eleven 12
(prototype) Bulk density, g / cm ³ 3.6 3.5 3.4 3.1 2.6 3.3 3.5 3.4 3.5 3.3 3.5 2.4 2.4 Refractoriness, ° С 1770 1750 1750 1740 1740 1750 1770 1750 1750 1740 1750 1740 1730 Fluidity, s 41 37 33 35 40 33 38 31 36 35 36 56 58 Sintering ability, ° С 1730 1700 1700 1690 1670 1700 1700 1680 1700 1690 1700 1660 1680

Claims (1)

Refractory mixture for filling the ladle’s steel channel, comprising a quartz-containing material with a SiO ₂ content _of at least 96 wt.% And graphite, characterized in that it additionally contains chromite concentrate and / or chromite ore with a Cr ₂ O ₃ content _of at least 35 wt.% and oleic and / or stearic acid in the following ratio of components, wt.%:
silica-containing material containing SiO ₂ not less than 96 wt.% 9.99-72.80 chromite concentrate and / or chromite ore containing Cr ₂ O ₃ not less than 35 wt.% 14.98-77.67 graphite 0.05-9.70 oleic and / or stearic acid 0.01-2.91,
wherein the quartz-containing material has a grain size of 0.1-1.0 mm, the chromite concentrate and / or chromite ore has a grain size of 0.1-1.0 mm, and graphite has a grain size of less than 0.1 mm.