SU856649A1 - Exothermic mixture for warming head portion of ingot at casting steels and alloys - Google Patents

Description

The invention relates to metallurgy, in particular, to compositions of exothermic mixtures used to insulate the top of the head of an ingot when casting steels and alloys. For warming the head part of the ingots in metallurgical plants of the country, lunkerite powders are widely used. They include combustible oxidants and refractory fillers. Their application allows to obtain a more dense structure of the upper part of the ingots and reduce the loss of metal with head trimming. Exothermic mixtures are known, including aluminum, fireclay, charcoal or coke, bauxite and 45% ferrosilicon 1, The disadvantage of these mixtures is the presence of explosive aluminum powder and the absence of flame intensifiers. Closest to the offer is an exothermic mixture for warming the head part of the ingot during casting of steels and alloys, containing, in wt.%: Aluminum-containing material (aluminum powder) 10-35; ferrosilicon 3-15; actuation agent for burning fluorite 0.5-5.0; heat-insulating material (coking) 20-40 and refractory filler (chamotte, magnesite, bauxite, etc.) 30-45. The presence of a combustion activator — fluorite (CaFj) makes it possible to intensify the burning of aluminum powder and to develop higher temperatures. High temperatures of combustion of the mixture improve the heating of the top of the nail and contribute to the formation of agglomeration. the crusts are the calcine, which is a good thermal insulator 2. However, this mixture contains aluminum powder, which, if it is poured during the manufacture of the mixture, does not exclude the possibility of explosions with serious consequences for the staff. In addition, the mixture consists of five components, the preparation of which, in particular, ferrosilicon and bauxite, is a laborious operation associated with the calcination and crushing of these materials. The purpose of the invention is the provision of explosion safety in the manufacture of the mixture and the simplification of its technology pr: t1odstv. This goal is achieved by the fact that the exothermAccheting mixture for insulating the head part of the ingot during casting of steels and alloys, including aluminum-containing material, heat-insulating material and fire-resistant accumulator, contains as aluminum-containing material waste in the production of aluminum alloys in the form of aluminum-containing slag, has an aluminum-containing slag that has an aluminum-containing material as an aluminum-containing material. weight,%: Waste in the production of aluminum alloys in the form of aluminum containing slag25-60 Thermal insulation. material 27-45 O1 non-refractory filler 10-34 In addition, the exothermic mixture contains waste in the production of aluminum alloys in the form of aluminum-containing slag fractional 0.3-3.0 mm of the following chemical composition, weight,%: Aluminum62-73 Magnesium.1.9-2 , 7 Copper: 1.4-1.5 Zinc: 0.4-0.6 Chlorine (in magnesium, potassium, sodium chlorides) 0.85-1.20 Silicon dioxide. 2.0-3.6 Alumina Rest As a heat-insulating material, the mixture contains coke or fly ash of thermal power plants operating on coke. An example of a refractory half-stem can serve ground chamotte. For the manufacture of the mixture, aluminum-containing slag is used, which is obtained by producing aluminum: deformable croiaBOV, for example, according to GOST 4784-74, which allows. It is recommended to exclude ferrosilicon, bauxite and fluorine-containing substance (fl orit) from the mixture. The possibility of removing these ingredients from the mixture is due to the fact that the functions of ferrosilicon (by sintering calcine) and fluorite f to enhance the combustion of aluminum) in the mixture are rendered non-combustible part of the aluminum-containing slag, which consists mainly of aluminum oxide, silicon dioxide and chlorides. The sintering and formation of a porous cinder is also facilitated by the refractory filler introduced into the mixture, in particular the ground metal. Large fraction aluminum-containing slags (with a particle size greater than 3 mm) are utilized for the purpose of extracting and reusing aluminum from them. However, slags of fractions of 3.0 mm and less due to 8 4 ores of extraction of metallic aluminum from them (due to the relatively high amount of inert substances in slags and high carbon waste in them of spomina) are removed from the dump slag grinding at metallurgical plants producing aluminum alloys are carried out in ball mills. In tab. 1 shows the limits of fractions in aluminum-containing sludges obtained by grinding them at various domestic factories. Table 1 The LOWER fraction limit of the slag used is 0.315. This is due to the fact that in slags with a predominance of fractions less than 0.3 mm, the aluminum content decreases 1.5-2 times with a simultaneous increase in chlorine content by more than 2 times. Therefore, after grinding shlaka, its classification by sieving on sieves is preferable, which makes it possible to exclude small (less than 0.3 mm) unfavorable chemical composition fractions. In the proposed mixture, the upper and lower limits of the slag content of aluminum production (60% and 25%) are determined by the achievement of the required burning temperature of the mixture (1730-1400 ° C). As a heat insulating material, coke or ash of coke-fired boilers running on coke are used. The limits of this material content (27-45%) are determined by the heat insulating capacity of the mixture, which is estimated by its bulk density and apparent density of the cinder obtained. Thus, with a coke content of less than 27%, the bulk density of the mixture (1.32 g / cm) and apparent density of cinder (1.21 g / cm) increase significantly. The upper limit of the coke content (45%) is due to the fact that with a higher content of this material in the casting of low-carbon steels and alloys (with carbon less than 0.30%), metal saturation is possible.

585

The established limits on the mixture of aluminum-containing slag and thermally insulating material provide the heating and insulating properties of the mixture, thus ensuring the explosion safety of the mixture during manufacture and greatly simplifying the technology of its production.

To make the mixture, pre-dried and crushed to a fraction of not more than 2.0 mm coke or ready ash CHP, dry aluminum containing; 1 sludge fraction 19 g 0.3-3.0 mm and ground grain powder with a grain size not more than 2.0 mm are used.

The raw materials are metered by weight or by volume, mixed in closed-type mixers to obtain a homogeneous powder mass, and then poured into closed containers, in which the mixture is delivered to steel-smelting workshops.

In a production environment. mix is tested at siphon pouring open-hearth

steels (20.45U8A, 40H, 65G, 25HGNML, 19HGN, 45G2, 18HGT, 20KhNZA, etc.). The consumption of the mixture is 1.5-3.0 kg / t during the casting of the metal under the ash-graphiton mixture with ingots weighing 6 tons,

The ash-graphite mixture is placed at the bottom of the mold before casting or at the beginning of casting and is used to protect the metal mirror from oxidation and cooling in order to improve the surface quality of the ingots. The mixture is given to the metal mirror at the end or immediately after casting and is intended for the OLYA heating and warming the top of the ingot in order to reduce the metal consumption for the head (profitable) part, which is a waste during the rolling or forging of ingots.

The mixture can also be used independently, i.e. without the use of heat-spreading and skull backfills during casting.

In tab. 2 shows the composition of the proposed mixture and their basic thermophysical properties.

Table 2

For comparison, the relevant indicators are given for a known mixture with an aluminum powder content of 14 and 28 sec.%:

Burning temperature, ° С1395 1726

Bulk weight of the mixture, g / cm1,08 1,20

Seeming density

cinder, g / cm

1.17 1.15

The specific calorific value of the proposed mixture is 2795-10559 kJ / kg, known

2795-9783 kJ / kg.

To backfill the top of six-ton profits

ingots at the end of their casting use

a mixture of the following composition, wt.%: Aluminum slag32 46

Cox34 34

Fireclay3420

Experienced mixtures begin to burn in 15-27 minutes. after they are filled with ingot profit, and then hot for 30–40 min with the formation of porous and horse baked from the calcine. When the atmosphere is controlled at the workplaces of the service personnel during the process and after casting of steel, only chlorine and fluorine specialists are found with the proposed and known mixtures. The quality of the metal according to macrostat complies with accepted technical standards.

Lumshawd slag fraction less than 3.0 mm does not explode. Its air-ignition ignition temperature is more than 800 ° C, and the auto-ignition temperature in the layer is more than 1000 ° C.

Claims (2)

The use of an aluminum-containing scrap metal instead of 78 in the exothermic mixture eliminates the possibility of an explosion, simplifies and facilitates the technology of its production and allows you to build compartments for preparing mixtures in conventional form, and not in explosion-proof, i.e. with lower capital costs. In addition, aluminum-containing slag, which is a waste in the production of aluminum by a combustible metal component, is much cheaper than a secondary aluminum powder. Thus, the proposed mixture ensures the achievement of explosion safety conditions in the process of its preparation and simplification of its production technology. Claim 1. An exothermic mixture for insulating the head part of an ingot during casting of steels and alloys, including an aluminum-containing material, heat-insulating material and fire resistant filler, which, in order to ensure explosion safety in the manufacture of the mixture and simplify its production technology, it contains quality. aluminum-containing material waste in the production of aluminum alloys in the form of an aluminum-containing material in the following ratio, ingredients, wt.%: Waste in the production of aluminum alloys in the form of aluminum-containing slag25 60 Heat-insulating material27-45 Refractory filler 10-34 2. Mixture according to claim 1, mt It is due to the fact that it contains waste during the production of aluminum alloys in the form of luminescent sclac fractions of 0.3-, 0 mm. 3, Mixture on Ш1. I and 2, so that it contains waste in the production of aluminum alloys in all aluminum-containing slag of the following chemical composition, wt.%: Aluminum62-73 Magnesium1.9-2.7 Copper -1.4- 1.5 Zinc, 0.4-0.6 Chlorine (in magnesium, potassium, sodium chlorides) 0.85-1.20 Silicon dioxide, 2.0-3.6 Alumina Oxide Remaining 4. The mixture according to item I, that it contains as a heat insulating material coke ash ash ztus CHP. Sources of information taken into account during the examination 1. G. K. and Oyks G. N. Metallurgists of steel. M., Metallurgists, 1964, p. 501. 2. USSR author's certificate number 458389, cl. On 22 D 27/06. 1975.