SU548371A1 - Exothermic mixture to insulate the ingot head - Google Patents

Description

Lenpyu mixture and the resulting calcine and improves their insulating properties. The appearance of pores contributes to the penetration of atmospheric oxygen into the mixture and its participation and the oxidation reaction of not only peat, but also aluminum. This may be limited in the composition of the mixture m1I1 to the maximum content of the solid oxidant sodium-potassium or barium nitrates (not more than 15 wt.%) Required for the mixture h / c and increase the specific amount of heat released. A significant advantage of the proposed mixture is also that the combustion resulting from combustion is a solid, porous, lightweight material with low thermal conductivity. Such high thermal insulation properties of the mixture and the resulting calcine result in the maximum heat loss through the metal mirror in the head part of the ingot, which is especially important for large weights (15-22 tons) that are installed within a few hours.

The content of peat in the mixture in the amount of 51-75 ve. % is determined by the weight of the ingot and the appearance of peat. Thus, a mixture containing 52–57% of peat can be used to loosen ingots weighing 7–9 tons, and a mixture with 65–75% peat can be used to insulate larger ingots. When using low-ash peat (up to 6% ash), its content in the mixture can be reduced to the lower limit, and if the ash content of peat is higher (more than 6%), its content in the mixture can be increased to the upper limit.

The content of the other main combustible component of the mixture, aluminum, is also determined by the weight of the ingot and the content of peat in the mixture. With an increase in the weight of the ingot and peat content, the amount of aluminum in the mixture rises and, conversely, with a relatively small weight of ingots and peat content at the lower limit, the aluminum content in the mixture can be 20-25 wt. %

The content of the remaining komioneitami mixture is determined by the content of the main combustible components - peat and aluminum - and is within the specified limits. At the same time, the amount of solid oxidizer (Na, K or Ba nitrate) and catalyst (binder) is proportional to the consumption of aluminum, and the amount of refractory filler (technical alumina, or magnesite, or chamotte powder, etc.) is inversely proportional to the consumption of peat, i.e. For example, as the amount of peat in the mixture increases, the amount of refractory material decreases, since the peat ash is also a refractory material.

The compositions of the proposed exothermic mixture are given in the examples.

Example 1. When casting sheet ingots weighing 16-28 tons with profitable extensions, an exothermic mixture of the following composition is used, weight. %: peat - 75, aluminum

in the form of powder - 10, sodium nitrate - 1, refractory powder - 23, cryolite - 1.

Example 2. In the casting of sheet ingots weighing 12-14 tons, an exothermic mixture of the following composition is used, in weight-quiz-like molds with thermal insulating liners. %: peat - 52, aluminum in the form of powder - 18, sodium nitrate - 15, refractory powder - 13, cryolite - 2. Mixture consumption 1.2-1.5 kg / t of steel.

When casting steel from above, the exothermic mixture is meaded onto the metal mirror at the head of the ingot immediately after it is filled with the head (profitable) part of the steel. The proposed exothermic mixture is prepared by mechanical mixing of its initial components, the grinding degree of which should be generally less than 1 mm. The crushed peat for the preparation of the mixture should be used in an air-dry state, therefore, if necessary, it must be pre-dried.

The optimal composition of the proposed exothermic mixture contains, weight. %: peat - 55, aluminum powder - 20, technical alumina - 3.

The physicomechanical properties of the optimal composition are as follows: Calorific value

mixtures, kcal / kg820-840

Increase temperature

mixtures, ° С390-420

Heat conductivity coefficient of calcine, kcal / m-h ° С

at temperature, ° С

200,078

5000,192

8000,236

10,000,365

As laboratory tests show, when two experimental heats of grade 30 steel were cast with two ingots weighing 45–50 kg each (the head part of one of which was insulated with the specified optimal composition of the exothermic mixture according to the prototype), the cinders of the mixtures were light, loose, uncompressed , ash gray; the length of the concentrated shrinkage shell and the shrinkage porosity and friability in the first smelting was 33.2%, in the second - 32.4%, and when the mixture was warmed using the prototype mixture, respectively, 37.7% and 36.4%.

From the test data of comparable exothermic mixtures, it follows that the ratio of ingredients in the proposed mixture provides greater efficiency from the point of view of thermal work, reduces the length of shrinkage defects in the ingot and thus increases the yield of it.

Claims (1)

Invention Formula An exothermic mixture for insulating the head of an ingot, mainly sheet ingots weighing 15-22 tons, including aluminum, peat, sodium or potassium nitrates, barium, refractory filler, fluoride, so as to reduce shrinkage defects in the head of the ingot, the indicated ingredients have the following ratio, weight% Peat 51.0-75.0 6 Aluminum 10.0-25.0 Sodium or potassium nitrates, or barium 1.0-15.0 Fluorspar 1.0- 5.0 Refractory filler 13.0-25.0 Sources of information taken into consideration by an expert se: 1. Patent England N «885 595, Cl. F 23P, 1961.