SU551117A1 - Exothermic Slag-Forming Mixture for Metal Casting - Google Patents

Description

The invention relates to the field of metallurgy, mainly to exothermic mixtures used in the casting of metal into molds. A known exothermic slag-forming mixture is introduced into the molds in order to produce ingots with a good surface and macrostructure, the composition of which includes a substance with high thermal insulating properties — exfoliated vermiculite ij. However, the absence of slag formation (fluxes) — silicate lump and fluorspar in cv / ecH — slows down the slagging process, which prevents the bottom of the ingot from having a defect-free surface. The exothermic slag-forming mixture, which contains combustible substances — magnesium and aluminum, heat-insulating substances — vermiculite and asbestos, oxidizer — manganese ore, fluxes — fluorspar and bauxite-2, is the closest to the invention by the technical essence and the achieved result. for the presence of magnesium and relatively high content of aluminum, the indicated ...-. iecb burns quite intensively with the formation of 1 -.a; I eat liquid slag from the very beginning of casting; -, Therefore, over the entire height of the ingot dsstygyts good surface s, and in the presence of c; vecH asbestita vermiculite and allows to have a sufficiently reliable heat tsgpo OTI JM-surface of the molten steel in izlozhl11ie, which ultimately leads to improved thermal performance gains and obtain ooies dense macrostructure of the head portion of the ingot. However, this exothermic slag oxide:; the blend mixture has the following dryness with - -; flawed, which limits the os: use when casting steel. azrvaemdsl-b: since the mixture contains magnkei;,; powder, which is o (ovally: ..: / snym substance; high cost of mixing. due to the relatively high content of magnesium and alumina powders in it, which are expensive; v:; substances (the selling price of one ton magnesium powder is 1850 rubles and aluminum powder is 515 rubles. Therefore, even with the minimum content of magnesium (2%) and aluminum powders in the mixture and the average content of other components, the cost of substances for the manufacture of one ton of the mixture was em 169rub. 10kop and the cost of magnesium and aluminum is equal to 114 rubles 25 kopecks, which is 67.5% of the cost of all components of the mixture.The aim of the invention is to create such an exothermic slag-forming mixture to improve the surface and macrostructure of the ingot, which would increase the safety of its use and have a low This is achieved by the fact that the exothermic slag-forming mixture, along with aluminum, manganese ore, fluorspar, vermiculite, also contains sawdust, silicate lump and chloraIngredients

Sawdust

Magnesium

Aluminum

Margaicena ore

Fluorspar

Silicate clump

Vermiculite

Ammonium chloride

Asbestos

Bauxite

by steel.

The compositions of the mixtures are given in table. one.

Table number 1

Content, wt.%:

mixture number 2

mixture number 3

mixture number 1

a mixture of N 4 (prototype)

35

2O

3.5

4 9 8 17.5

7.5 11 12.5 17.5 15

13

9.5

20

DA 35.5

1.5

one

20 9 Ammonium in the following ratio of ingredients, wt.%: Aluminum 4,0-11,0 Sawdust5,0-35,0 Manganese ore9-13 Fluorspar8-22 Silicate lump6-13 Ammonium chloride1-2 Vermiculite Else. When burning the mixture, ammonium chloride increases the reactivity of aluminum due to the destruction of the oxide film (AEjOJ present on the aluminum surface. The mixture is also accelerated by sawdust. The presence of silicate lump and fluorspar in the mixture, which lowers the slag melting temperature and gives it the necessary viscosity, contribute to the formation of liquid slag during combustion of the mixture from the very beginning of the filling of the mold

Mixture number 1, 2, 3 according to the invention, a mixture of NO 4 - according to the known composition.

The ingredient is used in powder form.55

A mixture of these compounds was tested when casting steel on 5 heats. The mixtures were introduced to the bottom of four molds installed on one pallet, and communicating with each other with a siphon through one center; 60

a mixture of the same composition was introduced into each mold. Then casting steel

After the ingots were cooled in their lower part, the boundary of the appearance of a specific wavy surface was observed, which corresponds to the onset of slag formation during combustion of the mixture and the appearance between the mold and the slag ingot. The measured distances from the bottom of the ingots to this boundary are given in Table. 2. 56

The distance from the bottom of the ingots to the border of the appearance of a wavy surface in them, fixing the beginning of slag formation during the combustion of the mixture

As can be seen from the table. 2, during the combustion of mixtures N9№ 1, 2 and 3, slag formation starts from the very beginning of steel casting and is no worse than that of the known mixture (mixture No. 4).

The melting temperature and viscosity of slags obtained from combustion are exothermicSlag temperature, ° С

155O 15OO 1450 1460 1400 130O 1200 1150 1100 1085 1050

551117

Table

The optimal composition of the exothermic slag-forming mixture is composition no. 2.

Physico-mechanical and technological properties of the mixtures are given in table. 3,

Table number 3

85

ki mixes number 1 and number 4 are given in table. four.

Table number 4

Viscosity, poise

mixture number 4

mixture number 1

2.9

3.3 15.1 4.7 6.2 15O The slag hardened 6.4 7.7 14.7 14.7 39.3 64.0 122 150 varnish hardened From tab. 4, it can be seen that the initial melting point of the slag for the mixture No. 1 is 1O85 ° C, for the mixture No. 4 is 1450 ° C. Compared the mixture No. 1 and No. 4 on the table. 3, it follows that mixture No. 1 is less explosive, since it has a slower speed and heat of the combustion process. To study the effect of the composition of the exotherm: ... a slag-forming mixture on the quality of the surface and the macrostructure of steel, 1I industrial tests of two mixtures according to the invention were carried out with the following ratio of ingredients, weight,%: Mixture No. 1 Mixture No. 2 Sawdust10 ALUMINUM 9 Manganese ore11 Spar spar2O Silicate block in the main open-hearth furnaces with steel production from the furnace into two steel-casting coves, and mixture No. 2 - during casting 92 heats of ShKh15 steel smelted in open-hearth furnaces with an acidic hearth, where the steel from the furnace was discharged into one steel-teeming ladle. two technologies: the first option - on each smelting the steel of one ladle was poured using mixture No. 1, and the steel of another ladle - using expanded vermiculite (mixture No. 3); second option a Canada smelting steel of one ladle was poured using mixture No. 1, and steel of another ladle using mixture No. 4, according to the current technology of the following composition, wt.%: Sawdust18 Aluminum7 Sodium nitrate7 Manganese ore15 Fluorspar 25 Sil “catna lump 15 Blast-furnace slag 13 The consumption of mixtures and vermiculite was, kg / t of steel: Mixture No. 13 Mixture of NO 43.8 Vermiculite {mixture No., 9 When casting steel ShKh15, mixture M 2 was used for 62 whole melts with ingot rolling on high-grade steel and 30 swimming trunks with steel appointment and cold drawing. In the last ZO melts, half of the steel at each melting was poured using mixture No. 2, and the other half using mixture No. 4. For a comparative assessment of the quality of steel, the first 62 heats processed the data on 2.73 heats, whose steel was cast using mixture No. 4 In all heats of the mixture and vermiculite in paper bags were injected to the bottom of the molds before the steel was cast. Comparative results of industrial tests of the exothermic slag-forming mixture according to the invention and the mixtures used according to the current technology are given in Table. 5. Table5

9

551117

ten

Continued table. five