SU550236A1 - Exothermic mixture to insulate the ingot head - Google Patents

Description

one

This invention relates to ferrous metal metal, in particular, exothermic mixture compositions, for heating the head of steel ingots.

Exothermic powder backfills are widely used to insulate the head part of quiet steel ingots and reduce the shrinkage defects, i.e., to increase the yield of good from ingots. Such exothermic mixtures include hot components, solid oxidizing agents, inert (refractory) additives, sometimes insulating components and catalysts, controlling the burning rate of exothermic mixtures.

Closest to the described invention for technical sushi, ness and the achieved result is an exothermic mixture containing, and the combustible ingredient in the form of heat-treated waste aluminum foil, aluminum powder, coke and sawdust, solid oxidizer in the form of sodium nitrate and mill scale, filler perlite, vermiculite and other materials, binder-catalyst in the form of sulphate liquor and fluorspar

 This mixture has a number of disadvantages,

reducing its effectiveness in terms of shrinkage defects in the ingot

and quality metal. The incomplete combustion of combustible components, mainly aluminum, leads to a decrease in the amount of heat produced during this process.

to keep the metal in the profitable part of the ingot in a liquid state. This is because the mixture contains only the minimum amount of solid oxidizing agents (1% NaNOa and 1% mill scale) and no

effective catalyst for the oxidation of aluminum by oxygen. The presence of a large amount of carbon-containing materials in the form of coke, coal, paper, foil, sawdust causes carbonization of the metal volumes in the head part of the ingot. Such a process is associated with incomplete combustion of carbon-containing materials, also due to the presence of slowly burning (glowing) sawdust in the mixture.

The inappropriate invention is to reduce the shrinkage defects in the head of an ingot. This is achieved by the fact that the mixture contains wood flour as wood and product and, additionally, river sand or quartz, technical alumina or corundum in the following ratio of ingredients, weight. %:

Aluminum15.0-35.0

Wood flour5.0-15.0

Sodium or potassium nitrate,

or bari 1,0--10,0

Expanded perlite 15,0-35,0

River sand or quartz1.0-5.0

Fluorspar1,0-5,0

Technical alumina or

corundum

Introduction to the mixture of wood flour - finely ground wood processing product, containing mainly particles less than 180 microns and an effective combustible material that burns at high speed in air during the initial burning period of the mixture, initiates the start of burning of the main combustible ingredient - aluminum.

When burning wood flour, gaseous products of combustion are formed, which contribute to the loosening of the mixture and the resulting calcine, which ensures their higher thermal insulation properties. The appearance of pores facilitates the penetration of atmospheric oxygen into the mixture and its participation in the oxidation of combustible comionants. This makes it possible to limit the composition of the mixture to a minimum content of solid oxidizing agent — nitrate Na or K, or Ba (no more than 10%) to increase the specific amount of heat released. A significant increase in the specific amount of heat, separation of the pulp during complete combustion of the mixture, and the good thermal insulation properties of the resulting porous solid calcine provide a much greater thermal efficiency of the exothermic mixture and a decrease in the depth of penetration into the ingot of shrinkable defects.

The high thermal insulation properties of the mixture and the resulting coal are also provided by the presence of expanded perlite in its composition. However, expanded perlite is only a good insulator until it is melted (the upper limit of the temperature range for melting perlite 1150-ISOO C). To preserve the perlite at high temperatures of the mixture in a solid form, it is necessary to protect it with another inert refractory material. As such a material, the mixture contains an alumina-based material — technical alumina or corundum, which is satisfactorily displaced with the expanded perlite.

At the same time, high thermal insulation properties of the mixture and calcine are provided only with the use of expanded perlite of a certain volume weight and fractional composition. The best results are obtained by using expanded puffing with a volume weight of 150-180 kg / m and a particle size of 0.2-1.2 mm. The use of lighter perlite, especially with a bulk weight of 50–70 kg / m and a large number of fine fractions (; 0.2 mm), is less effective, since such perlite quickly melts, and this forms a dense, pasty cinder with a high thermal conductivity. In this case, the heat loss in the profitable part of the ingot significantly increases.

The presence in the mixture of small amounts (no more than 5%) of river sand or quartz and a fluorite mattress makes it possible to bind individual grains of perlite to the whole frame of a porous cinder. Fluorspar or fluorides of other metals (NaF, NasAlFe, etc.) are also with Na nitrate, K or Ba catalysts, necessary for the stable burning of aluminum. Since the carbon-containing material in the proposed exothermic mixture (wood flour) burns almost completely, no carbonization of the metal occurs at the head of the ingot.

The content of the components in the mixture is determined by its purpose and associated with this amount of aluminum in the mixture. So, when casting small-sized ingots (up to 2-3 tons), crystallizing within a short period of time and having relatively large losses of teila in the profitable part than from the ingots of the crucious weight, in order to ensure the effective operation of the exothermic mixture, it is necessary to add up to 28 35% of the main fuel component is aluminum, 12-15% wood flour, about 10% nitrate of Na or K, or Ba, 3-5% of river sand and fluorspar, the rest is expanded perlite and alumina.

When casting large-sized ingots (over 15 tonnes) that crystallize for a long period of time, it is necessary to have an exothermic mixture that would dissolve the entire period of time, replacing the resulting shrinkage shell with liquid metal. In this case, the mixture can have a significantly lower amount (15–18%) of the most expensive component — aluminum and, accordingly, a smaller amount of wood flour (5–7%) of Na or K nitrate, or Ba (1–5%) and the proportion of inert materials is expanded perlite (up to 30-35%) and technical alumina or corundum (up to 35-40%). Between these extreme slits, depending on the weight of the ingot, intermediate mixtures are selected.

The proposed exothermic mixture is an effective steel ingot elutiner and has a volume weight of between 500 and 600, depending on the composition and weight of the ingot, 1.0–1.5 kg / ton of steel.

Example 1. In the casting of varietal ingots with a weight of 8–10 tons, an exothermic mixture of the following composition is used in weight-reducing ingot molds with tenloisol zoine liners. %: aluminum in the form of powder, shredded chips, waste aluminum alloys 22; wood flour 10; barium nitrate 5; expanded perlite 24; technical alumina or corundum 33; river sand or quartz 3; fluorspar 3.

Mix consumption 1.3-1.5 kg / t steel.

Example 2. In the casting of sheet ingots of carbon and low alloyed steel weighing 16-20 tons, an exothermic mixture of the following composition is used, weight. %: aluminum 16; wood flour 6; barium nitrate 3; swollen inner 28; technical alumina 38; river nesok 4; hydrofluor board 3.

Mix consumption 1.0-1.3 kg / t steel.

11 p and m 3. In the casting of ingots of small weight (2-3 tons) a mixture of the following composition is used, weight. %: aluminum 35; wood flour 15; barium nitrate 10; expanded perlite 16; technical alumina 20; river sand 1; fluorspar 4.

Mixture consumption 1.4-1.5 kg / t steel.

Example 4. When casting ingots of 22-25 tons, a mixture of the following composition is used, weight. %: aluminum 15; wood flour 5; barium nitrate 1; expanded perlite 35; technical alumina 40; river sand 3; fluorspar 1.

Mix consumption 1.0-1.2 kg / t steel.

Example 5. When casting ingots weighing 4-5 tons, a mixture of the following composition is used, weight. %; aluminum 30; wood flour 12; barium nitrate 8; expanded perlite 18; technical gliozem 22; river sand 5; fluorspar 5.

Mixture consumption 1.3-1.4 kg / t steel.

When casting steel on top, the exothermic mixture sits on the metal mirror at the head of the ingot immediately after it is filled, and when casting steel with a siphon, the mixture sits on the metal mirror before the end of filling the tin (profitable) part of the ingot.

Described; An exothermic sms can be prepared; but by mechanical mixing of its initial components, the degree of comminution of which should be generally less than 1 mm. First, the expanded perlite and technical alumina NLP corundum are mixed first, after which the remaining components are added to the mixture.

Composition, weight.

We offer a mixture

Known som.

When testing the proposed and known exothermic mixtures, it was found that this mixture is more efficient from the point of view of heat work: the mixture burns within 2-3 minutes after filling, which is formed during the combustion of the mixture of calcine, darkens rapidly, the content of AI (metal) in the calcine is only 4%.

For testing, exothermic mixtures of the following composition were taken, weight. %:

We offer a mixture of aluminum mink 11,0

Aluminum chips12.0

Wood flour10,0

Barium nitrate 5.0

Expanded perlite (volumetric weight 170 kg / mm) 24.0 Technical alumina32.0 River sand3.0 Fluorspar 3.0

Known mixture Heat treated shredded waste A1 (foil) 35.0 Aluminum powder 16.0 Sawdust -8.0 Ground coal 10.0 Patrieva saltpeter1.0 Rolled mill scale1., 0 Calcined magnesium carbonate 13.0 Sculptured perlite 13.0 Spit feldspar1 , 0 Sulphate liquor 2.0 Exothermic mixtures of these compositions were tested when casting steel of grade 30 with a casting on each of them two ingots weighing 45-50 kg. Metal temperature before pouring into molds 1640-1650С. The consumption of the mixture on the insulation of the head of one ingot at each heat 200 g

The chemical composition of the stubs described by my and known exothermic mixtures is given in Table. 1, and the properties of the mixtures and the resulting cinders are in the table. 2

Table 1

As cutting of ingots shows, the length of the concentrated shrinkage shell and the nodusaged porosity and looseness when insulating ingots with the exothermic mixture described is 32.8 and 31.1% of the ingot length, and when insulating with the known exothermic mixture 40.7 and 37.0% of the length ingot.

Thus, the proposed exothermic mixture is more efficient from the point of view of thermal work, it allows reducing the length of shrinkage defects in the ingot and increasing the yield of the good from the ingot.

Claims (1)

1. An exothermic mixture for insulating the head part of an ingot, including aluminum, wood product, sodium or potassium nitrate, or bari, expanded perlite, fluorspar, characterized in that reducing the shrinkage defects in the head of the ingot; as a wood product, the mixture contains wood flour and, additionally, river sand or quartz, technical alumina or corundum in the following ratio of ingredients, weight. %: Aluminum 15,0-35,0 Wood flour5.0-15.0 Sodium or potassium nitrate or barium 1.0-10.0 Expanded perlite 15,0-35,0 River sand or quartz 1.0-5.0 Fluorspar1.0-5.0 Technical alumina or corundum The source of information taken into account in the examination: 1. Patent of Great Britain No. 1280768, Cl, C 5G (B 22D 27/06), 1972.