RU2755187C1 - Method for aluminothermic production of ferrotitanium - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy, in particular, to aluminothermic production of ferrotitanium. The first part of the main charge includes a mixture of at least two of the following technogenic waste in the form of waste from abrasive processing of titanium semi-fabricated products, titanium scale from hot processing of titanium preforms, or cyclone dust from abrasive processing of titanium semi-fabricated products, used as titanium-containing materials, then secondary aluminium powder is added to said mixture of technogenic waste in an amount of 0.26 to 0.36 of the weight of the titanium-containing mixture of waste. Iron scale in an amount considering the iron required to obtain a titanium content in the alloy in the range of 30 to 50%, secondary aluminium powder and lime are introduced in the second part of the precipitation charge. Both parts of the charge are then melted in an electroslag furnace with a non-consumable carbon electrode until the crystalliser is completely filled with the melting product in the mode of portioned supply of the main and the precipitation parts of the charge through different chutes, wherein portions of the precipitation part of the charge are introduced 1 to 3 minutes after introducing a portion of the main part of the charge.

EFFECT: invention makes it possible to recycle technogenic titanium production waste, producing an alloy containing 30 to 50% wt. titanium.

1 cl, 1 ex, 2 tbl

Description

The invention relates to metallurgy, in particular to the production of ferrotitanium grades FTi35 according to GOST 4761-91 and grades FeTi40 according to ISO 5454-80, which are in demand in ferrous metallurgy, where they are used as an alloying component for the production of low-alloy structural and cast steels, as well as stainless and heat-resistant steels.

In the aluminothermal production of ferrotitanium of these grades, ilmenite concentrate or its mixture with rutile concentrate is mainly used as titanium-containing raw material, while out-of-furnace or furnace methods are used [1].

When using in the charge only ilmenite concentrate, which contains many iron oxides, it is difficult to obtain ferrotitanium with a titanium content close to 40% (wt.). To increase the titanium content in the alloy, rutile concentrate, rich in titanium oxide, is introduced into the charge, but it is expensive and increases the cost of titanium in the alloy. Moreover, if we are talking about out-of-furnace production, as stipulated in RF patent No. 2325456 [2], in which to maintain the heat of the process, even more expensive components such as Berthollet's salt and calcium peroxide are introduced into the charge composition.

Known methods of aluminothermal production of ferrotitanium with an increased titanium content due to preliminary enrichment of ilmenite concentrates for titanium dioxide by removing iron oxides from them [3]. The disadvantage of such methods is a double redistribution, i.e. complication of technology.

A known method of introducing into the composition of the aluminothermic charge waste - crushed slag of ferrotitanium production, containing 17-21 wt. % TiO ₂ [4]. The disadvantage of this method is the need from the point of view of the balance of titanium in the charge the introduction of ilmenite concentrate with a TiO ₂ content of 59-65% (wt.) And crushed electric furnace titanium-containing slag (54-59 wt.% TiO ₂ ) in an amount seven times higher the volume of crushed slag introduced into the charge of ferrotitanium production containing 17-21 wt. %.

There is a known method of producing high-titanium ferroalloy from ilmenite [5], according to which, at the first stage of smelting, ilmenite is enriched with titanium oxides by removing most of the iron oxides from it with carbon, and then a mixture of crushed titanium-rich slag and aluminum is formed in a metal shell and such a consumable electrode is melted under a layer of flux in an electroslag furnace. The disadvantage of this technology is the two-stage nature and complexity of forming a consumable electrode with a uniform density of the filler - a very important characteristic from the point of view of the stability of the electrical parameters of electroslag smelting.

The closest in technical essence, used titanium-containing raw materials, smelting technology and the achieved result is the method according to RF patent No. 2196843 "Method for furnace smelting of ferrotitanium from titanium oxides" [6]. The method has been tested in the processing of titanium fired cut slag (titanium production waste) to obtain ferrotitanium due to the reduction of titanium oxides from this waste with ferroaluminum in an electroslag furnace.

The disadvantage of this method is the use in the charge of one of the many man-made waste of titanium production - slag of the fiery cut of titanium and the use of ferroaluminum as a reductant, the latter requires a separate redistribution for its smelting. In addition, the resulting ferrotitanium has a high nitrogen content of 0.82-1.46 wt. % due to the presence of metallized titanium particles (up to 50%) containing 2.5-3.5 wt. % nitrogen, which limits the scope of use of finished ferrotitanium in steelmaking.

The objective of the present invention is the recycling of other types of generated industrial waste titanium production to obtain ferrotitanium containing 30-50 wt. % titanium, reducing the cost of ferrotitanium and improving its quality by reducing the nitrogen content in the resulting alloy to less than 0.5 wt. %.

The task is achieved by the fact that in the method of aluminothermal production of ferrotitanium from a charge containing titanium-containing material, aluminum powder, iron scale, lime, including preparing the charge and melting it in an electric furnace, the charge is prepared separately in two parts, while the composition of the first part charge (main) as titanium-containing materials, a mixture of at least two of the following man-made titanium-containing wastes is introduced:

- waste from abrasive processing of titanium semi-finished products (BZ);

- titanium scale from hot working of titanium blanks (TO);

- cyclonic dust captured during abrasive processing of titanium semi-finished products (CP),

then aluminum powder is added to this waste mixture at a ratio of these two components, respectively, 1: (0.26-0.36) by weight, and iron scale is introduced into the second part of the charge (precipitation) in an amount taking into account the necessary iron to obtain in the alloy titanium content in the range of 30-50%, secondary aluminum powder for reducing iron oxides from a selected amount of iron scale and lime for binding forming alumina, after which both parts of the charge are melted in an electroslag furnace with a non-consumable carbon electrode until the crystallizer is completely filled with the melting product in the mode batch feeding of the main and settling parts of the charge through different chutes in proportion to the charged volumes, while portions of the settling part of the charge are introduced into the furnace 1-3 minutes after the introduction of a portion of the main charge.

The method provides for the recycling of the following man-made titanium production wastes generated in volumes of thousands of tons per year, suitable for smelting ferrotitanium.

1. Waste from abrasive processing of titanium semi-finished products. These wastes are formed in the form of large pieces and fines and contain in their composition the metallized part (analogous to the nitrogen content of the metallized part of the titanium fired cut slag) in an amount of about 20%, and the rest is an oxidized part containing 65-75 wt. % titanium oxides with impurities of difficult to separate metallized particles. Before melting in an electric furnace for introduction into the composition of the charge, this waste is subject to crushing and screening, which provides for the separation of large pieces of the metallized part containing nitrogen.

2. Titanium scale from hot working of titanium blanks in the form of small plates and powder. Contains 80-90 wt. % titanium oxides.

3. Cyclonic dust captured during abrasive processing of titanium semi-finished products. It has a fraction of less than 2 mm, contains on average about 15% of fine scrapine of titanium and its alloys. The oxide part contains 60-70 wt. % titanium oxides and abrasive particles from the actuation of aluminum-zirconium wheels.

The specified wastes of titanium production differ in their physical state and chemical composition, therefore, for the purpose of averaging, it is envisaged to introduce into the first part of the charge (main) at least two of these wastes. For example, it is advisable to introduce cyclonic dust with a finely dispersed state into the main part of the charge together with one (or two) other types of waste in order to reduce its flight during melting. It is also advisable to combine waste from abrasive processing of titanium semifinished products and titanium scale from hot working of titanium blanks in the composition of the main part of the charge, since this makes it possible to reduce the proportion of metallized particles in the mixture that are present in the BZ and contain nitrogen.

In addition, mixing at least two (or all three) wastes for the first part of the charge (main) is carried out from the condition of obtaining the titanium content in the mixture in terms of titanium dioxide, preferably at least 70% (wt.) In order to average the charge over the titanium oxide content and calculating a more accurate sample of aluminum powder as a reducing agent for titanium oxides.

The ratio of the components in the first part of the charge (main), namely a mixture of at least two of the following man-made waste:

- waste from abrasive processing of titanium semi-finished products (BZ);

- titanium scale from hot working of titanium blanks (OK);

- cyclonic dust captured during abrasive processing of titanium semi-finished products (CP);

Secondary aluminum powder, selected as 1: (0.26-0.36) by weight, respectively.

When the fraction of aluminum powder is less than 0.26, the degree of extraction of titanium from raw materials decreases. An increase in this proportion over 0.36 leads to an increase in the aluminum content in ferrotitanium (more than 10 wt.%), Which is undesirable for consumers.

Iron scale, secondary aluminum powder and lime are added to the composition of the second part of the charge (precipitation). In this case, the amount of iron scale in this part is calculated taking into account the reducing titanium from the first part of the charge and proceeding from the required iron to obtain the titanium content in the alloy in the range of 30-50%.

The consumption of secondary aluminum powder in the second part of the charge is calculated according to the stoichiometry of the reduction reaction of iron oxides from a selected amount of iron scale.

The amount of lime for binding the forming alumina is set in the range of 0.7-0.8 of the selected consumption of secondary aluminum powder.

Selection of separate feeding into the electroslag furnace of the first main and second settling parts of the charge with a time interval of 1-3 minutes. is due to the fact that in the case of preparing one composition of the charge from all the materials used (respectively, the general mixing of the components) leads to the fact that the metallized parts of titanium present in the waste participate in the reduction of iron oxides from the scale with the formation of cakes.

With separate feeding of the selected two parts of the charge, the following mechanism is implemented. When a portion of the first part of the charge is fed into the furnace, it passes through the melting flux, heats up, and the reduction reactions of titanium oxides begin upon contact with aluminum. During the subsequent, after a certain period of time, the supply of a portion of the second part of the charge, which also passes through the furnace flux layer, the reduction reactions of iron oxides with aluminum (at least the initial period) proceed under conditions of some isolation from the first part of the charge. At the same time, the high thermal effect of the reduction of iron oxides with aluminum promotes mixing of the dimple of liquid metal in the electroslag furnace, intensification of the reduction reactions of titanium oxides, and deposition of the finished alloy.

The most important condition for the proposed option of separate feeding into the furnace of two different parts of the charge is the synchronization of the supply of portions of the charge according to their selected volumes. Under the envisaged condition of the presence of two leaks for loading materials into the furnace, this is quite feasible and, in principle, can be automated.

Examples of specific implementation Smelting of ferrotitanium from a mixture of technogenic titanium-containing waste was carried out in an electroslag furnace with a non-consumable carbon electrode. Furnace grade USh 148, transformer power - 760 kW, electrode diameter 150-200 mm, water-cooled crucible. Metal capacity up to 200 kg.

In the composition of charge materials for melting, a mixture of technogenic titanium production wastes was used:

- crushed waste from abrasive processing of titanium semi-finished products, cleaned from metallized pieces (BZ);

- titanium scale (TO);

- cyclonic dust caught during abrasive processing of titanium semi-finished products (CP).

Along with this mixture of wastes in the charge was used: secondary aluminum powder, iron scale and lime. The ratio of the components of the charge was selected from the conditions:

- a mixture of technogenic titanium-containing wastes (at least two of those listed) with a titanium content in terms of titanium dioxide not less than 70% (wt.);

- the amount of iron scale, taking into account the necessary iron to obtain the content of titanium in the alloy in the range of 30-50%;

- powder of secondary aluminum in an amount for the reduction of titanium oxides from waste titanium and iron oxides from a selected amount of iron scale;

Each smelting in the furnace was started with firing up and guiding the flux required for electroslag processes. _{Fluorspar (CaF 2} ) was used as a flux in an amount providing the thickness of the liquid flux at the beginning of work 7-12 cm (38-42 kg). Then the charge was fed. The liquid flux simultaneously provided the binding of alumina formed during the reduction of titanium oxides with aluminum.

In the first melting, a mixture of all three of the above wastes was used with their ratio by weight BZ: TO: CP, respectively, 40:40:20. With this ratio of wastes in the mixture, the titanium content in it in terms of titanium dioxide was about 70% (wt.). The consumption of secondary aluminum powder was taken in the amount of 0.3 fractions of the weight of the titanium waste mixture. Steel shavings were introduced into the charge at the rate of obtaining in the final alloy about 40 wt. % titanium.

When melting on this composition of the charge, the effect of "chilling" of the process and the need to work at higher electrical parameters were revealed. This is explained by the relatively low thermal effect of the reactions of reduction of titanium oxides with aluminum, especially the lower titanium oxides, which are actually present in the waste in amounts up to 15 wt. % of the total mass of oxides. Smelting was finished after about 60% of the prepared charge was consumed. An ingot of an inhomogeneous alloy was found in the crucible, which cannot be qualified as a commercial one.

In the second heat, with the same parameters of the titanium waste mixture and the consumption of secondary aluminum powder, the steel shavings were replaced with a mixture of iron scale, secondary aluminum powder and lime. The consumption of iron scale is selected from the condition of obtaining 40% titanium in the alloy, and the consumption of secondary aluminum powder - according to the stoichiometry of the reduction reaction of iron oxides with aluminum, lime - 0.6 shares of the consumption of aluminum.

All types of charge materials were mixed together (total weight 350 kg) and fed into the furnace in portions as they were melted. It was not possible to provide a stable electric mode of the furnace, which is why the melting was stopped after loading about a third of the charged volume. A formed ingot was not found in the crucible; the material was cakes of materials.

The practical impracticability of aluminothermal smelting of ferrotitanium from the indicated titanium-containing wastes according to the tested options required the development of other approaches to smelting.

Subsequently, smelting was carried out on two parts of the charge: the first (main) part of the charge is a mixture of at least two titanium-containing waste, secondary aluminum powder, the second part (precipitation) is iron scale, secondary aluminum powder and lime with separate feeding into the furnace through different chutes two parts of the charge, prepared and divided proportionally by weight according to the scheme: a portion of the charge 1, after 1-3 minutes - a portion of the charge 2 and repeating these cycles until both parts of the charge are consumed.

The parameters of the conducted heats and their results are shown in table. 1.

The degree of extraction of titanium in smelts and the chemical composition of the resulting ferrotitanium are given in table. 2.

Individual samples of ferrotitanium were taken from the ingot of smelting No. 5 with a height of 40 cm and a diameter of 40 cm from the upper and lower parts of the ingot, as well as in the middle part in the center of the ingot and along the edges at this height - a total of five samples to assess the homogeneity of the resulting ferrotitanium. Chemical analysis for the content of titanium and aluminum showed that the deviation of the content of elements among themselves at different points was - for titanium not more than 4.9 wt. %, for aluminum - no more than 1.5 wt. %, which is quite acceptable for the conditions of mandatory averaging of a commercial product.

The results of the performed smelting show the suitability of using in the charge of aluminothermic smelting of ferrotitanium various types of titanium-containing wastes generated at different stages of titanium production, which were not previously used for this purpose.

With the consumption of secondary aluminum powder at the lower limit of the selected range of consumption, the extraction of titanium into the alloy is minimal (melting 3), and with its consumption above the selected range (0.4 versus 0.36) under the conditions of the obtained increased extraction of titanium, the alloy contains more than 10% aluminum (melting 6), which is higher than it is regulated, in particular, for the FeTi40Al10 grade according to GOST ISO 5454-80.

Due to the removal of most of the metallized pieces of BZ, containing an increased amount of nitrogen, from the composition of this waste before mixing mixtures of titanium-containing waste, it was possible to solve the task of reducing the nitrogen content in the finished ferrotitanium - less than 0.5% (wt.), Which is important for a number of consumers of ferrotitanium.

Acceptable homogeneity of the obtained ferrotitanium in terms of titanium and aluminum content under conditions of batch feeding of two different parts of the charge into the furnace with an interval of 1-3 minutes (preferably about two minutes) is shown by sampling at different levels and horizons of the ingot from smelting No. 5.

Thus, aluminothermal smelting of ferrotitanium according to the parameters of the proposed formula is quite feasible and allows you to involve in the production waste of titanium production, which were traditionally sent to the dump, and thus the problem of reducing the environmental load on the territory is solved. At the same time, the cost of the produced ferrotitanium is reduced due to the cheapness of titanium-containing waste in comparison with the traditional raw material - ilmenite or rutile concentrate.

Currently, the proposed method of aluminothermal production of ferrotitanium from an expanded range of technogenic titanium production wastes according to the selected technological parameters is implemented in the industrial production version in volumes at the request of consumers.

Sources of information

1. M.A. Ryss, Production of ferroalloys, Moscow, "Metallurgy", 1985, p. 269-281.

2. RF patent №2325456, charge for ferrotitanium production, publ. May 27, 2008.

3. RF patent No. 2398907, Method for producing high-percentage ferrotitanium, publ. 10.09.2010.

4. RF patent No. 2608936, Charge and method of aluminothermic production of ferrotitanium using it, publ. 26.01.2017.

5. RF patent №2329322, Method of producing high-titanium ferroalloy from ilmenite, publ. 20.07.2008.

6. RF patent No. 2196843, Method of furnace smelting of ferrotitanium from titanium oxides, publ. January 20, 2003.

Claims (4)

A method for aluminothermal production of ferrotitanium from a charge containing titanium-containing material, aluminum powder, iron scale, lime, including preparing the charge and melting it in an electric furnace, characterized in that the charge is prepared in two parts, while the composition of the first part of the charge, the main one, a mixture of at least two of the following man-made titanium-containing wastes is introduced as titanium-containing materials: - waste from abrasive processing of titanium semi-finished products, - titanium scale from hot working of titanium blanks, - cyclonic dust captured during the abrasive processing of titanium semi-finished products, then secondary aluminum powder is added to this waste mixture in an amount of 0.26-0.36 of the mass of the titanium-containing waste mixture, and iron scale is added to the second part of the precipitation mixture in an amount of taking into account the necessary iron to obtain a titanium content in the alloy in the range of 30-50%, secondary aluminum powder for reducing iron oxides from a selected amount of iron scale and lime to bind the resulting alumina, after which both parts of the charge are melted in an electroslag furnace with a non-consumable carbon electrode until complete filling the crystallizer with the smelting product in the mode of batch feeding of the main and settling parts of the charge through different chutes in proportion to the charged volumes, while portions of the settling part of the charge are introduced into the furnace 1-3 minutes after the introduction of a portion of the main part of the charge.