RU2850598C1 - Method for obtaining iron-containing slag from thermitic mixture - Google Patents

Abstract

FIELD: foundry production.

SUBSTANCE: method for obtaining an iron-containing alloy from a thermite mixture includes making a casting mould, filling its cavity with a thermite mixture and igniting the thermite mixture to form an iron-containing melt in the casting mould. The casting mould contains a body (1) with a bottom (2) and an open top. A layer of ground slag (3) from the exothermic remelting of thermite mixtures is poured onto the bottom of the body, and a hollow pipe (4) is installed on the specified layer of slag in the central part of the bottom. Ground slag from the exothermic remelting of thermite mixtures is poured between the pipe (4) and the inner surface of the body (1), and an iron-aluminium thermite mixture with an active aluminium content of 17-65% by mass and the remainder being iron oxide is poured into the pipe. Then the pipe is removed and the upper layer of the iron-aluminium thermite mixture is ignited.

EFFECT: obtaining an iron-containing slab from a thermite mixture, intended for further processing by rolling, without defects in the form of scorching and obtained in a simple-to-manufacture casting mould.

1 cl, 4 dwg

Description

The invention relates to foundry production, in particular to methods for producing an iron-containing slab from a thermite charge, and can be used in the mechanical engineering industry.

A known method for producing steel castings, according to Russian Patent No. 2367540, involves fabricating a casting mold with elements of a gating system. The mold cavity is filled with a thermite mixture, and the upper portion is ignited with a gas-flame torch to initiate an exothermic reaction, forming molten steel in the mold and allowing it to solidify. This method allows steel castings to be produced from metallurgical waste. However, implementing this method entails costs associated with mold fabrication and places high demands on the refractoriness of the materials from which it is made, due to the high temperatures associated with the exothermic reaction. When the exothermic reaction occurs in thermite mixtures intended for producing molten steel, the high temperature, exceeding the melting point of iron (1539°C), results in the formation of a defect in the form of a difficult-to-remove burnt-on deposit.

The objective of the invention is to obtain from thermite charge a defect-free iron-containing slab in the form of burnt-on material, intended for further processing by rolling, obtained in a simple-to-manufacture casting mold formed from slag fractions of exothermic remelting of thermite charge materials with a refractoriness of up to 1900 °C.

The technical result achieved in this way consists in obtaining from the thermite charge an iron-containing slab without defects in the form of burn-on in the casting mold, formed from slag fractions of the exothermic remelting of thermite charges with a refractoriness of up to 1900 °C.

The said problem is solved due to the fact that the method for producing an iron-containing slab from a thermite charge, which includes making a casting mold, filling its cavity with a thermite charge, igniting the thermite charge with the formation of an iron-containing melt in the casting mold, has the following differences: the casting mold is made in a housing with a bottom and an open top, a layer of ground slag from the exothermic remelting of thermite charges is poured onto the bottom of the housing, a hollow pipe is installed on the slag layer in the central part of the bottom, ground slag from the exothermic remelting of thermite charges is poured into the space between the pipe and the inner surface of the housing, an iron-aluminum thermite charge is placed inside the pipe above the level of the ground slag, the content of active aluminum in which is 17-65 wt.%, the rest is iron oxide, the pipe is removed and the upper layer of the iron-aluminum thermite charge is ignited.

The entire set of features of the method ensures the production of an iron-containing slab from the thermite charge without defects in the form of burn-on in the casting mold, formed from slag fractions of the exothermic remelting of thermite charges with a refractoriness of up to 1900 °C.

The production of a casting mould in a housing with a bottom and an open top makes it possible to place ground slag from the exothermic remelting of thermite batches in bulk form.

Filling the bottom of the vessel with a layer of ground slag from the exothermic remelting of thermite charges ensures protection of the bottom of the vessel from the temperature effects of the iron-containing melt formed as a result of the exothermic remelting of thermite charges, as well as uniform cooling of the iron-containing slab.

The installation of a hollow pipe in the central part of the bottom on a layer of slag from the exothermic remelting of thermite batches ensures the possibility of placing the thermite batch in its cavity and uniform cooling of the melt from which the iron-containing slab is formed.

Filling the space between the pipe and the inner surface of the casing with ground slag from the exothermic remelting of thermite batches creates a cavity for the casting mold and ensures uniform cooling throughout the entire height of the melt, from which the iron-containing slab is formed.

Placing an iron-aluminum thermite charge inside the tube provides the base material from which the iron-containing slab is formed. The active aluminum content of 17-65 wt.% in the thermite charge enables their exothermic remelting and the production of various iron-containing melts. For example, according to Russian patent 2637735, if the thermite charge contains 17-21 wt.% active aluminum, the exothermic reaction results in the formation of low-carbon boiling steel. According to the source [Zhilin S.G., Predein V.V., Khudyakova V.A., Bogdanova N.A. Effect of heating the thermite charge on the structure and properties of an ingot of an intermetallic Fe-Al alloy obtained by exothermic remelting // Metallurgist. [2024. No. 11. pp. 94-101.] An increase in the active aluminum content in thermite batches from 25 to 65 wt.% during exothermic remelting leads to the formation of iron-aluminum melts. If the active aluminum content in the thermite batch is less than 17 wt.%, the reaction cannot be initiated. An active aluminum content in the thermite batch greater than 65 wt.% does not guarantee separation of the metallic and slag phases in the reaction products.

Removing the pipe from the casting mold ensures contact between the thermite charge and the melt formed from it directly with the slag from the exothermic remelting of the thermite charge, ensuring uniform cooling of the melt and the absence of burning on the surface of the iron-containing slab.

Due to the fact that the iron-aluminum thermite charge is poured into the pipe above the level of the ground slag, the possibility of ignition of the surface of the thermite charge is ensured.

The operating principle of the method for producing iron-containing slabs from thermite charge is explained in the drawing. Fig. 1 shows a section of the body 1 with an open top, placed on the bottom 2 of the body 1 with a layer of ground slag 3 from exothermic remelting of thermite charges, with a hollow pipe 4 installed in the central part of the bottom 2 on the slag layer 3. Fig. 2 shows a section of the body 1 of the casting mold, showing the technological stage of filling the space between the pipe 4 and the inner surface of the body 1 with ground slag 3 from exothermic remelting of thermite charges, as well as an iron-aluminum thermite charge 5 placed inside the pipe 4 above the level of the ground slag 3. Fig. 3 shows a section of the body 1 of the casting mold after removing the pipe 4 from it. Fig. 4 shows a section of the body 1 of the casting mold with an iron-containing slab 6 formed in it as a result of exothermic remelting of the thermite charge with a dense conglomerate of slag 7 from exothermic remelting thermite charges.

The method for producing an iron-containing slab from a thermite charge is carried out as follows. A layer (for example, 3 cm thick) of ground slag 3 from the exothermic remelting of thermite charges is poured onto the bottom 2 of the body 1, made, for example, of sheet steel grade St3, having, for example, a fraction of no more than 4 mm and a chemical composition, in wt.%: aluminum oxide 72-85; iron oxide 6-15; silicon oxide 3-4; magnesium oxide 3-4; manganese oxide 1.6-2; impurities - the rest. In the central part of the bottom 2, on the slag layer 3, a hollow pipe 4 with a diameter of, for example, 30 mm and a wall thickness of, for example, 1 mm, made, for example, of sheet steel grade St3, is installed. Ground slag 3 from the exothermic remelting of thermite batches is poured into the space between pipe 4 and the inner surface of body 1. Iron-aluminum thermite batch 5, containing, for example, 21.55 wt.% active aluminum, is placed inside pipe 4 above the level of ground slag 3 (e.g., 5 mm). To obtain a thermite batch containing 21.55 wt.% active aluminum, 25 wt.% of aluminum alloy B95 grit can be used. Since alloy B95 contains 86.2 mass percent aluminum, the amount of active aluminum can be determined by the formula 25⋅0.862=21.55. The rest is iron scale, impurities, and modifiers.

Then the pipe 4 is removed, and an igniter composition (for example, a mixture consisting of 23 wt.% of PAP2 grade aluminum powder and 77 wt.% of iron scale of fractions up to 0.2 mm) is poured onto the surface of the thermite charge 5 in an amount of, for example, 5 grams, which is ignited, for example, using a spark device.

The exothermic reaction moves consistently throughout the entire volume of the thermite charge 5 in the top-down direction and goes through the main reactions:

3FeO+2Al=Al ₂ O ₃ +3Fe,

Fe ₂ O ₃ + 2Al = Al ₂ O ₃ + 2Fe.

A molten iron-containing alloy forms in the body of mold 1 and solidifies within approximately 5 minutes. After solidification, an iron-containing slab 6 made from the thermite charge is removed from the mold, along with a dense slag conglomerate 7 resulting from the exothermic remelting of the thermite charge.

Claims (1)

A method for producing an iron-containing alloy from a thermite charge, which includes making a casting mold, filling its cavity with the thermite charge, igniting the thermite charge with the formation of an iron-containing melt in the casting mold, characterized in that the casting mold is made in a housing containing a bottom and an open top, wherein a layer of ground slag from the exothermic remelting of the thermite charges is poured onto the bottom of said housing, a hollow pipe is installed on the layer of ground slag in the central part of the bottom, ground slag from the exothermic remelting of the thermite charges is poured into the space between the pipe and the inner surface of the housing, an iron-aluminum thermite charge is placed inside the pipe above the level of the ground slag, the content of active aluminum in which is 17-65 wt.%, and iron oxide is the rest, the pipe is removed and the upper layer of the iron-aluminum thermite charge is ignited.