RU2609884C1 - Extrusion briquette for steel production - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention refers to ferrous metallurgy, namely to obtainment of extrusion briquette containing metallurgy waste, such as metallurgy scales, and intended for use as a charge component in steel making processes. Extrusion briquette obtained by stiff vacuum extrusion consists of metallurgy scales, carbon-containing material, bentonite and cement, and contains, wt %: FeO > 10; Fe₂O₃ > 10; MgO 0.1-7.0; MnO 0.1-4.5; Cr₂O₃ 0.01-1.5; C 0.8-40.0; SiO₂ 0.1-10.0; ZnO 0.01-0.5; TiO₂ 0.01-1.5; CaO 0.1-10.0; Al₂O₃ 0.1-15.0, impurities < 3, where content of Fe_total comprises 20.0-80.0. Compression strength is at least 5.0 MPa, specific density is at least 3.0 kg/dm³, open porosity comprises at least 10 %, and softening start temperature is at least 1200 °C.

EFFECT: homogeneous quality of briquettes serving as accelerators of formation of highly active foaming free-running slag with increased content of lower iron oxide, reduced melting time and emergy cost, increased metal yield.

2 cl, 1 dwg, 3 tbl, 2 ex

Description

The invention relates to the field of ferrous metallurgy, and in particular to the production of an extrusion briquette containing metallurgical waste, in particular metallurgical scale, intended for use as a component of the charge in steelmaking processes.

The prior art extrusion briquette used for steelmaking (patent RU 2147617, class C22B 1/245, publ. 04/20/2000), consisting of an iron-containing material, a carbon-containing material and an organic binder. The disadvantage of this known technical solution is that the known briquette has low strength properties, insufficiently high chemical properties, and its production is costly and time-consuming.

Also known are extrusion briquettes made by hard vacuum extrusion, disclosed in patents RU 2504588 C1, publ. 01/20/2014, RU 2502812 C1, publ. 02.27.2013 and RU 2506325 C1, publ. 02/10/2014.

The closest analogue of the invention is an extrusion briquette for steelmaking, disclosed in patent RU 2506325 C1, cl. C22B 1/243, publ. 02/10/2014. The well-known briquette is made by hard vacuum extrusion from a mixture of iron-containing materials (including mill scale), carbon-containing material, mineral binder and fluxing additives. The density of the obtained briquettes was 2.0-2.2 g / cm ³ , the crushing strength after aging for 48 hours was 4.5-5.0 MPa. The disadvantages of the known briquette are insufficiently optimal physical properties and chemical composition and, accordingly, the qualitative characteristics of the resulting steel.

The objective of the invention is the manufacture of an extrusion briquette with a given chemical characteristics, allowing you to use them as a component of the charge in steelmaking processes containing a carbon-containing component and a high percentage of iron oxide.

The technical result of the invention is to obtain briquettes with high chemical properties, of uniform quality, providing the function of an accelerator for the formation of highly active foamed fluid-moving slag with a high content of iron oxide, oxidation of harmful impurities and their assimilation, which in turn helps to reduce melting time, energy costs, quantity used slag-forming components and ferroalloys, as well as an increase in metal yield, including due to reduction renewal of all oxide forms of iron found in the heat.

To achieve the specified technical result, the claimed briquette obtained by hard vacuum extrusion from mill scale, carbon-containing material (1-75%), bentonite (1-2%) and cement (5%), contains, wt. %:

FeO > 10 Fe ₂ O ₃ > 10 MgO 0.1-7.0 MnO 0.1-4.5 Cr ₂ O ₃ 0.01-1.5 C 0.8-40.0 SiO ₂ 0.1-10.0 Zno 0.01-0.5 TiO ₂ 0.01-1.5 Cao 0.1-10.0 Al ₂ O ₃ 0.1-15.0 impurities <3

wherein Fe _total is 20.0-80.0, compressive strength is not less than 5.0 MPa, specific gravity is not less than 3.0 kg / dm ³ , open porosity is not less than 10%, and the softening start temperature is not less than 1200 ° C.

The claimed extrusion briquette is obtained by the method of hard vacuum extrusion using mill scale of a separate metallurgical production with the corresponding chemical composition, which provides a briquette of a given composition. In the particular case, it is possible to prepare the mixture using scale of various industries with the appropriate chemical composition, ensuring the achievement of a given chemical composition.

Iron in oxide forms is the raw material for reduction, providing an increase in steel production. The iron oxide contained in the briquettes activates the formation of foamed slag, which increases the efficiency of the furnace due to its low thermal conductivity, which reduces the load on energy resources, the consumption of electrodes and refractory materials. In the converter industry, briquettes are introduced into cast iron to remove carbon and reduce iron waste.

Carbon in the carbon-containing component plays the role of a reducing element. In the process of carbon reduction of elements from oxide forms, the generation of CO and CO ₂ gases occurs, which ensures the formation of highly active foamed slag.

The presence in the briquettes of oxides of magnesium, calcium, iron, silicon and aluminum in these ranges, as well as the presence of carbon in an amount of 0.1-40.0%, ensures the passage of an exothermic reaction during smelting, during which the recovery of active elements from oxides: magnesium , manganese, titanium, calcium, chromium, forming a complex alloy that promotes alloying and modification of the melt. Slag containing alumina helps to reduce the content of sulfur, oxygen and non-metallic inclusions in steel.

Manganese, recovered from magnesium oxide contained in the briquette in an amount of 0.1-4.5%, acts as a deoxidizing agent for steel and an alloying additive. Manganese, forming a solid solution with iron, helps to increase the hardness and strength of steel, without loss of ductility. In addition, manganese binds sulfur, eliminating the possibility of the formation of a harmful sulfur compound with iron.

TiO ₂ in an amount of 0.01-1.5% increases the density and strength of steel, contributes to the grinding of grain, improves machinability and corrosion resistance, is also a deoxidizer of steel. Titanium also forms strong carbides, nitrides and carbonitrides, neutralizing nitrogen in steel.

Oxides of calcium (0.1-10.0%) and magnesium (0.1-7.0%), being slag-forming materials, have a positive effect on the durability of the lining of the melting unit, limiting the interaction of slag with the slag belt. The content of calcium oxide above 10% will lead to an increase in the melting temperature of the slag, which will reduce its refining ability and for this reason is impractical.

Silica, present in briquettes in an amount of 0.1-10.0%, is involved in the formation of slag and, by the end of the oxidation period of the smelting, is reduced as the metal is heated and is used as a deoxidizer.

The briquette also contains impurities, the total content of which does not exceed 3 wt. %

The percentage of active elements is regulated in the above ranges, depending on the lost steel grade and is provided by mixing the feedstock with different chemical composition.

To obtain an extrusion briquette, scale of -3 mm fraction of a separate metallurgical production is used, or a mixture is prepared using scale of various industries to achieve the required chemical composition. Dross is mixed with carbon-containing material 1-75% and with 1-2% bentonite, additional mixing in a mixing screw with the addition of water to obtain a homogenized mixture, the mixture is aged for 8 to 24 hours, mixing the mixture in a twin-roll mixer with the addition of 5% cement in the quality of the binder and water to achieve the moisture content of the mixture 12-15%, feeding into the vacuum chamber of the extruder with preliminary compaction of the mixture in the extruder meter and passing through the extruder made with a fixed front part of the main axis th extrusion screw.

The technological process for producing briquettes by the method of hard vacuum extrusion in the presence of a binder is given below with reference to the attached scheme 1.

Schema Positions:

1 - the site of the reception of raw materials;

2 - Separation site;

3 - Raw materials warehouse after separation;

4 - Bunker No. 1;

5 - Bunker No. 2 carbon-containing raw materials (coke, coal fines);

6 - Bunker No. 3 bentonite;

7 - Conveyor No. 1;

8 - Mixer;

9 - Conveyor No. 2;

10 - Warehouse for sludge prepared mixture;

11 - Receiving hopper for the prepared mixture;

12 - Silo No. 1 cumulative;

13 - Silo No. 2 cumulative (spare);

14 - Silo No. 3;

15 - Conveyor No. 3;

16 - Two-roll mixer;

17 - extruder dispenser;

18 - extruder;

19 - Conveyor No. 4;

20 - Land for finished briquettes (chest);

21 - Warehouse for finished products.

Separation plot. At this site, preliminary separation of the starting materials by particle size distribution is performed to obtain acceptable particle sizes. The quality of raw materials arriving at the site - mill scale with a moisture content of 0.3-10%, is checked in a chemical laboratory.

Scale is divided into 3 fractions at the McCloskej international 130 installation. The feedstock is fed to the McCloskej international 130 installation with a front-end loader. As a result of separation, the following fractions are distinguished: fraction +10 mm; fraction - 10 + 3 mm; fraction - 3 mm.

The + 10 mm and -10 + 3 mm fractions are not involved in the technological process, are moved by the front-end loader in GEL and are subject to sale to consumers. To implement the method, a scale of -3 mm fraction is used, which is subject to further processing on a separator to obtain satisfactory quality of the prepared materials, removal of small metal inclusions in the form of needle shavings, which are not permissible for conducting the technological process of processing scale.

The preparation of the charge. At this site, dry mixing of the feedstock and plasticization is performed to obtain a homogeneous mixture of scale, carbon-containing feedstock and bentonite and the sludge of the mixture to achieve a state of swelling of bentonite and increase the elasticity of the prepared mixture.

After separation, the raw material enters the charge preparation section.

Dross of -3 mm fraction by a front-end loader is fed into hopper No. 1, from which through a screw feeder to conveyor No. 1. Simultaneously with the scale, carbon-containing raw materials are fed from hopper No. 2 and bentonite from hopper No. 3 to conveyor No. 1 through a screw feeder. At that, 23-92% of scale, 1-75% of carbon-containing material and 1-2% of bentonite are fed. Based on the experimental data, subject to these proportions, the best elasticity and plasticity of the mixture are achieved, eliminating the presence of air porosities in it, which ensures uniform and homogeneous filling of the extruder chamber and, as a result, obtaining a high-strength briquette.

Next, the scale, carbon-containing material and bentonite conveyor No. 2 is sent to the mixer for homogenization and stabilization of the composition. In the process of mixing, water is supplied to the mixer to moisten and plasticize the mixture with a 10% moisture content in the mixture.

Prepared homogenized mixture from the mixer is fed via conveyor No. 2 to the warehouse for sedimentation of the mixture, where it lasts from 8 to 24 hours, which is optimal to ensure the elasticity of the mixture.

The preliminary saturation with moisture of the hygroscopic elements of the mixture, namely bentonite, and their elimination of excess moisture during the sludge sedimentation contributes to the further qualitative mixing of the mixture with a binder (cement), which further ensures high physical and mechanical properties of the briquettes.

In addition, this mixing sequence ensures uniformity of the chemical composition of the manufactured briquettes in each batch of the product.

Press section. At the pressing site, the resulting mixture is fed with the addition of water and a binder in the form of cement into an extrusion press to obtain briquettes.

The prepared mixture from the stockpile of sludge with a front-end loader is loaded into the receiving hopper of the pressing line. From the receiving hopper through the screw feeder, the mixture enters the conveyor No. 3, through which it is fed into a twin-roll mixer.

From silo No. 3 to conveyor No. 3, simultaneously with the prepared mixture, 5% of cement is supplied to the twin-roll mixer, which is sufficient to ensure the required strength of the resulting briquette. During mixing, water is supplied to the mixer to plasticize the finished mixture and achieve a moisture content of 12-15%.

After mixing in a twin-roll mixer with cement and water, the mixture is fed into the extruder dosing device, in which it is pre-compacted, and fed into the vacuum chamber of the extruder. A low vacuum is maintained in the vacuum chamber from 760 to 25 mm Hg, from 1 × 10 + 5 to 1 × 10 + 1 Pa.

To obtain a briquette using an extrusion press with a fixed front of the axis of the main extrusion screw. Unlike presses with a freely located front part of the axis, the press used allows for uniform flow rate and density of the initial mass when it is fed to the channels of the die plate along its entire plane, with guaranteed production of briquettes of uniform quality in terms of strength characteristics and specific gravity.

After passing through an extruder with a side pressure of 5.2 MPa, the finished product is fed by conveyor No. 4 to the finished briquette section (in the chest).

On the site of finished briquettes, a set of product strength of at least 5MPa occurs. After curing (78 hours), finished briquettes are transported by a front-end loader to a finished goods warehouse to form a transport lot and ship to the consumer.

The invention is illustrated by the following examples.

Example 1. To obtain a briquette used mill scale (92%), carbon-containing raw materials (1%), bentonite (2%) and as a cement binder (5%) with the addition of water. The chemical composition of the components and the resulting briquettes are shown in table 1.

After separation, a scale of -3 mm fraction and carbon-containing raw materials were mixed with bentonite in a mixer in a ratio of 10 kg of bentonite per 1 ton of charge. During the mixing process, water was fed to obtain a 10% charge moisture content.

The prepared homogenized charge was kept in stock for a charge of 12 hours. The prepared mixture from the warehouse for sludge and cement are simultaneously sent to a two-roll mixer. With stirring, water is supplied to plasticize the mixture and achieve a moisture content of 12%.

After mixing in a twin-roll mixer, the mixture is fed to the extruder dosing device for its preliminary compaction and fed into the vacuum chamber of the extruder. The pressure in the vacuum chamber is 50 mm Hg.

Then, the charge was passed through an extruder with a side pressure of 5.2 MPa, after which the resulting briquette was sent to the finished briquette section for building strength of at least 5 MPa for 78 hours.

Example 2. To obtain a briquette used mill scale of two industries (21% + 49%) fraction -3 mm, carbon-containing raw materials (23%), bentonite (2%) and as a cement binder (5%) with the addition of water. The chemical composition of the components and the resulting briquettes are shown in table 2.

After separation, a scale of -3 mm fraction and carbon-containing raw materials were mixed with bentonite in a mixer in a ratio of 10 kg of bentonite per 1 ton of charge. During the mixing process, water was fed to obtain a 10% charge moisture content.

The prepared homogenized charge was kept in stock for a charge of 12 hours. The prepared mixture from the warehouse for sludge and cement are simultaneously sent to a two-roll mixer. With stirring, water is supplied to plasticize the mixture and achieve a moisture content of 12%.

After mixing in a twin-roll mixer, the mixture is fed to the extruder dosing device for its preliminary compaction and fed into the vacuum chamber of the extruder. The pressure in the vacuum chamber is 50 mm Hg.

Then, the charge was passed through an extruder with a side pressure of 5.2 MPa, after which the resulting briquette was sent to the finished briquette section for building strength of at least 5 MPa for 78 hours.

Ready briquettes correspond to the following physical properties (table. 3):

Thus, briquettes obtained within a given chemical composition are high-quality products used as a component of the charge in steelmaking. Given the presence of these chemical components, briquettes are not only raw materials for recovery, but also play the role of flux, providing optimization of the processes of slag formation and favorably affecting the quality of steel and reducing the time of melting and processing of steel.

In the process of melting, a highly active foamed liquid-moving slag is formed, which ensures the transfer of harmful impurities (sulfur, phosphorus) and oxides of reducing elements from the steel structure to slag and their presence in the slag before the end of the melting process.

Claims (4)

1. Briquette for steelmaking, obtained by hard vacuum extrusion, consisting of mill scale, 1-75% carbon-containing material, 1-2% bentonite and 5% cement and containing, by weight. %: FeO > 10 Fe ₂ O ₃ > 10 MgO 0.1-7.0 MnO 0.1-4.5 Cr ₂ O ₃ 0.01-1.5 C 0.8-40.0 SiO ₂ 0.1-10.0 Zno 0.01-0.5 TiO ₂ 0.01-1.5 Cao 0.1-10.0 Al ₂ O ₃ 0.1-15.0 impurities <3 wherein Fe _total is 20.0-80.0, compressive strength is not less than 5.0 MPa, specific gravity is not less than 3.0 kg / dm ³ , open porosity is not less than 10%, and the softening start temperature is not less than 1200 ° C. 2. The briquette according to claim 1, characterized in that the scale is used as a scale of a separate or different metallurgical industries.

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