RU2738742C2 - Method of processing lumpy material for producing high-quality steel - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention can be used to produce high-quality steel in all steelmaking units. Small-lump iron containing raw material (SLICRM) is represented by small-lump iron-containing scrap (SLICS) and/or fine iron (FI), and/or dross, at that, prior to the beginning of melting, the calculated amount of small lump iron-containing scrap and/or fine iron and/or dross is placed into big-bag type containers with their subsequent arrangement in steel making unit between large-sized scrap metal in lower part of steelmaking unit closer to bottom or bath of liquid metal.

EFFECT: invention increases efficiency of production of high-quality steel due to local fixation of containers with said raw material, reduce labor intensity of melting process and expand functional capabilities by performing melting both on dry and liquid bath, as well as increase steel quality due to possibility of accurate batching of charge initial materials.

3 cl, 1 dwg, 3 ex

Description

The invention relates to a method for processing small-sized raw materials to obtain high-quality steel in all types of steel-making units (hereinafter referred to as CA). The productivity of the CA is determined by the efficiency of the following production stages: the speed of filling the metal charge into the CA, the intensity of the melting process and the discharge of liquid steel from the CA bowl.

The use in steelmaking of small pieces of scrap (hereinafter referred to as MCL), fine iron (hereinafter referred to as MJ) or steel scale (hereinafter referred to as CRM) belonging to the group of bulk materials creates a number of insoluble problems associated with the occurrence of undesirable manifestations at the stage of filling MCL or MJ or CO in CA in the form of raw material spillage, which leads to the loss of the specified raw material at the melting stage due to its sintering and floating on the liquid steel surface, an increase in the oxidation of liquid steel, which leads to a decrease in the quality and loss of liquid steel yield. MKL, MJ and CO as a metal charge have very important advantages, such as high bulk density (about 3 t / m ³ ) and good magnetic adhesion for handling and loading by electromagnetic method.

Known patent, which discloses a method of loading a charge into an electric arc furnace, and according to which the introduction of coke to the hearth of the furnace and the subsequent filling of small, medium and heavy scrap (types of scrap, in accordance with GOST 2787-75, industry standards, regulations and specifications ), cast iron. Thus, an intensification of the melting of the charge and a reduction in electrode breakdowns is achieved (USSR patent No. 1280024, 12/30/1986). The disadvantages of this method is the very limited use of scrap filling in steelmaking, since this method involves only dry bath smelting, while the most common method of scrap smelting in industrial metallurgy involves liquid bath smelting. This is due to the fact that when melting into a liquid bath, small (small-sized) scrap, waking up between pieces of medium and heavy scrap, and falling on the slag layer above the liquid metal layer, is sintered. Thus, the yield of steel, as well as its quality, is significantly reduced due to the deviation of proportionality in terms of the mass of the charge of each type.

Also at the stage of filling small lump raw materials into the CA: MCL, MJ and CO using a magnetic washer, significant losses of raw materials are possible, in the form of spillage, which leads to the difficulty of maintaining the accuracy of the proportions of filling between MCL or MJ or CO and large and medium lump scrap, as a result which is problematic to obtain high quality steel. Further, at the stage of melting, in case of deviation of proportionality in terms of the mass of charge of each type, complications are possible, leading to a deviation of the melting process from the normal mode, which also leads to a decrease in the quality of steel.

Another disadvantage of this invention is the lack of the possibility of effective use of metallurgical additives due to insufficient close contact with the charge, spillage of additives between the scrap into a liquid bath.

The technical problem to be solved by the claimed invention lies in the development of a technologically advanced, efficient and non-laborious method for processing small-sized raw materials to obtain high-quality steel, which makes it possible to use MCL and / or MJ and / or CO on a level with a conventional metal charge when melting both dry and and a liquid bath and allows to achieve an increase in the efficiency of the process of filling the specified raw materials in the CA.

The technical result of the invention is

increasing the efficiency of the high-quality steel production process when using MKL and / or MJ and / or CO on a level with the use of medium and heavy scrap by increasing the efficiency of melting MKL and / or MJ and / or CO, which leads to a significant increase in the yield of liquid steel, and achieved by strong local fixation of MCL or MJ or CO between layers of medium and heavy scrap in SA, by increasing the degree of activation of the melting process by providing optimal conditions for the operation of metallurgical additives with the exclusion of undesirable sintering processes and floating to the surface, which helps to reduce the oxidation of liquid steel, as well as reducing the labor intensity of the method, expanding the functionality, which is due to the possibility of using the method in melting both in dry and liquid baths, and improving the quality of steel due to the possibility of accurate dosing of MCL or MJ or CO in the SA to obtain steel with specified characteristics.

The specified technical result is achieved due to the method of production of high-quality steel, including loading into the furnace lumpy scrap and small lump iron-containing raw materials (MZhS), carrying out smelting until they are completely melted, dissolved and reduced in a liquid metal bath. Small-sized iron-containing scrap (MCL) and / or fine-dispersed iron (MJ) and / or scale are used as SMR, while before the start of melting, the calculated amount of small-size iron-containing scrap and / or fine-dispersed iron and / or scale is placed in containers of the big- type. bag with their subsequent placement in the steelmaking unit between the lumpy scrap in the lower part of the steelmaking unit closer to the bottom or bath of liquid metal. As a scrap, between which big bags are placed, medium and heavy scrap can be used.

Traditionally, in steelmaking, the size of a piece, the type of metal steel or cast iron scrap (metal charge) in the Russian Federation is regulated by GOST 2787-75, industry standards, regulations and technical specifications. Small pieces of scrap are determined by the following technical parameters: piece weight less than 0.5 kg and piece size less than 50 mm. Fine iron is understood as the iron-containing raw material of the lump fraction and / or particles with sizes from 0 mm to 50 mm with a metallic iron content of more than 90%. Steel scale is a flat multilayer structure with a thickness of several microns to hundreds of microns and consists mainly of iron oxides. Traditionally, the above raw materials without an additional process of agglomeration, briquetting or granulating as iron-containing raw materials in metallurgical production are practically not used in large quantities.

As a soft container for placing small pieces of scrap and / or fine iron and / or steel scale, mainly soft combustible containers, flexible containers are used, that is, containers made of material that does not interfere with the clamping of MCL or MJ or CO, placed in the container, by traditional lumpy scrap (for example, medium and / or heavy) after filling into the CA bowl and burning during the melting process. Polymer flexible containers, such as big bags, can be used as a soft container.

It is possible to use fluxes (limestone, silica, fluorspar, etc.), modifiers containing aluminum, boron, nitrogen, and reducing agents as metallurgical additives for mixing with MCL and / or MJ and / or CO and placing in big bags (limestone, silica, fluorspar, etc.) carbon-silicon-containing raw materials).

The location of big bags with a mixture of MCL and / or MJ and / or CO and metallurgical additives during filling into the lower part of the steelmaking unit, closer to the bottom and / or the liquid metal bath, allows to achieve a significant acceleration of the process of melting, melting, dissolution and recovery of the contents of the big -bags when filling a steelmaking ladle with liquid steel.

With the indicated arrangement of big bags, by the time of full collection of liquid steel in the CA bowl or by the beginning of the first slag coming out, all the raw materials placed in the big bag go through the stages of melting, stirring, dissolving and recovery. This allows not only to speed up the process of smelting raw materials and, thus, reduces the labor intensity of the method, but also provides an increase in the efficiency of melting of small pieces of finely dispersed iron and steel scale, which leads to a significant increase in the yield of liquid steel and an increase in the efficiency of the high-quality steel production process as a whole.

The use of big bags in the method makes it possible to simplify, accelerate and provide controlled by weight filling of small pieces of scrap and / or fine iron and / or steel scale, as well as locally fix this raw material in a soft flexible container in the volume of traditional piece of scrap (for example, medium or heavy ) in the lower part of the steelmaking unit closer to the bottom and / or bath of molten metal. Thus, it is possible to avoid spillage of MCL and / or MJ and / or CO between pieces of larger scrap before the start of melting. In addition, the placement of MCL and / or MJ and / or CO in soft containers, when filling in the SA, allows the specified raw material to be squeezed from all sides between pieces of larger scrap, which leads to its holding in a fixed position in the lower part of the steelmaking unit closer to the bottom and / or a bath of liquid metal and after the combustion of the container and also prevents small particles from spilling between pieces of larger scrap.

It was also found that the efficiency of melting localized and tightly compressed raw materials in big bags is similar to the efficiency of melting lumpy scrap, which is not achieved when filling MCL, MJ and CO without using soft containers, i.e. in bulk.

Thus, local fixation of MCL and / or MJ and / or CO in a soft container excludes negative manifestations during the melting process, such as spilling of raw materials onto the hearth and sintering of fine raw materials, floating on the surface of liquid steel, and provides a decrease in oxidation of liquid steel, in As a result, it is possible to achieve an increase in the yield of liquid steel and a significant increase in the efficiency of melting small-piece raw materials and the steel production process as a whole. Also, the possibility of fixing the MCL and / or MJ and / or CO allows melting in the optimal position in the SA, namely, in the lower part of the steelmaking unit closer to the hearth and / or bath of liquid metal and, thus, accelerate the melting process and reduce the labor intensity ...

The use of big bags and free-flowing properties of MCL and / or MJ and / or CO allows the use of high-quality mixing and localization of metallurgical additives in the volume of small-sized scrap and / or fine-dispersed iron and / or steel scale, avoiding spillage of metallurgical additives. The possibility of localization and close contact of small pieces of scrap and / or finely dispersed iron and / or steel scale with metallurgical additives (for example, fluxes and / or modifiers and / or reducing agents) due to their joint placement in a big bag allows to achieve an increase in the efficiency and reaction rate of additives and, as a consequence, an increase in the yield of liquid steel when melting small-sized scrap and / or fine-dispersed iron and / or steel scale, which in general provides an increase in the efficiency of melting MCL and / or MJ and / or CO and, as a consequence, the yield of liquid steel. Thus, an increase in the efficiency of the steel production process from small pieces of scrap, fine iron and steel scale is achieved by increasing the yield of liquid steel when melting small pieces of scrap and / or fine iron and / or steel scale, controlled by activation of the melting process. This is due to the fact that in the volume of finely dispersed materials, additives quickly and actively enter the steelmaking process, thereby eliminating unpredictable technological delays in the melting process and / or vice versa activating the melting processes. When in contact with medium- or large-sized scrap, these positive effects are not observed.

Localization and fixation of small pieces of scrap and / or fine iron and / or steel scale, achieved in the method, makes it possible to obtain higher quality steel, which is due to the mixing of small pieces of scrap and / or fine iron and / or steel scale with metallurgical additives and their close contact , with the exception of spillage of small pieces of scrap and / or fine iron and / or steel scale and floating on the steel surface, which can lead to the preservation of inclusions of unmelted phases of raw material fractions in the liquid steel mass.

Thus, the possibility of localization and close contact of small lumpy scrap and / or fine iron and / or steel scale with metallurgical additives leads to an increase in the degree of activation of the melting process due to the provision of optimal conditions for the operation of metallurgical additives with the exclusion of undesirable sintering processes and floating to the surface, which helps to reduce the oxidation of liquid steel and leads to which leads to a significant increase in the yield of liquid steel in the process of processing small-sized raw materials and the efficiency of the production process of high-quality steel as a whole.

Localization and fixation of small pieces of scrap and / or fine iron and / or steel scale by the present method also makes it possible to obtain steel of a higher quality. In addition, the possibility of firm fixation of MCL and / or MJ and / or CO in big bags between the layers of scrap allows melting both in dry and liquid baths, which significantly expands the functionality of the method.

The possibility of providing controlled by weight filling of small pieces of scrap with the elimination of loss of raw materials and, thus, ensuring more accurate control of the amount of loaded raw materials in the CA and compliance with the proportions between MCL, MJ and CO and traditional scrap (medium and heavy) due to the use of big bags allows to simplify the process, as well as to ensure the production of high quality steel.

In addition, the use of big bags can significantly speed up the filling process and, thus, reduce the complexity of the process.

The essence of the invention is illustrated in figure 1, which shows the location of small pieces of scrap and / or fine iron and / or steel scale in a steel furnace.

In the figure, positions 1-8 indicate:

1 - a bowl of a steel-making furnace;

2 - carbon electrodes;

3 - scrap large and medium lump, of various types;

4 - big bag;

5 - small pieces of scrap and / or fine iron and / or steel scale with metallurgical additives;

6 - hearth CA;

7 - liquid bath;

8 - CA vault.

The method for processing SCL and / or MJ and / or CO can be illustrated by the following examples. Reducing agents are dosed into the big bag together with MCL, MJ and CO in a mixed form - to neutralize excess oxidation or fluxes - to induce slag of proper quality during the melting process, or modifiers - to influence the crystallization process. The amount of the additive is determined by calculation or empirical.

Example 1. Steel scale with a particle size of 100 to 200 microns is mixed with a reducing agent in a 4: 1 ratio in a mixer, after which the resulting mixture is filled in polypropylene big bags with a carrying capacity of up to 1.5 t, after which the big bags are poured onto a layer of lumpy scrap (piece more than 50 mm) into the bottom of the steelmaking furnace. After that, the big bags are poured from above with a mixture of lumpy (medium or heavy) scrap to the top, but not above the arch of the CA. In addition, big bags are poured into the oven so that the free space between them can be filled with traditional scrap so as to provide a conductive channel from the electrodes to the bottom of the CA. Then the steelmaking furnace is turned on and the loaded raw material is melted. Melting is carried out at a temperature of 1650-1670C. Smelting begins with the upper layer of the charge. The liquid metal flows down to the bottom and begins to interact with the raw materials in the big bags. Liquid metal begins to absorb raw materials in big bags and at this moment the functional purpose of big bags ends and the process of melting, mixing and dissolving raw materials piled in big bags in liquid metal begins. At the same time, after the big bag is melted, there is no spillage of steel scale particles through pieces of lumpy scrap into a bath with liquid metal.

The developed method allows processing steel scale with a particle size from 100 to 200 microns by 95%.

Example 2. Fine iron with a particle size of 1 to 50 mm is mixed with fluxes, in a ratio of 25: 1 in a mixer, after which the resulting mixture is filled with polypropylene big bags with a carrying capacity of up to 1.5 tons. Next, big bags are poured onto a layer of lumpy scrap ( medium or heavy) to the bottom of the steelmaking furnace. After that, the big bags are poured from above with a mixture of lumpy (medium or heavy) scrap to the top, but not above the arch of the CA. In addition, big bags are poured into the oven so that the free space between them can be filled with traditional scrap so as to provide a conductive channel from the electrodes to the bottom of the CA. Then the steelmaking furnace is turned on and the loaded raw material is melted. Melting is carried out at a temperature of 1650-1670C. Smelting begins with the upper layer of the charge. The liquid metal flows down to the bottom and begins to interact with the raw materials in the big bags. Liquid metal begins to absorb raw materials in big bags and at this moment the functional purpose of big bags ends and the process of melting, mixing and dissolving raw materials piled in big bags in liquid metal begins. At the same time, after the big bag melts, there is no spillage of fine iron through the pieces of lumpy scrap into the bath with liquid metal.

The developed method makes it possible to process finely dispersed iron with a particle size of 1 to 50 mm by 98%.

Example 3. Small-sized scrap with a particle size of 1 to 50 mm is mixed with a boron ferroalloy modifier (to increase the strength of steel) in a 50: 1 ratio in a mixer, after which the resulting mixture is filled in polypropylene big bags with a carrying capacity of up to 1.5 tons, after which big bags are poured onto a layer of lumpy (medium or heavy) scrap in the lower part of the steelmaking furnace. After that, the big bags are poured from above with a mixture of lumpy (medium or heavy) scrap to the top, but not above the arch of the CA. In addition, big bags are poured into the oven so that the free space between them can be filled with traditional scrap so as to provide a conductive channel from the electrodes to the bottom of the CA. Then the steelmaking furnace is turned on and the loaded raw material is melted. Melting is carried out at a temperature of 1650-1670C. Smelting begins with the upper layer of the charge. The liquid metal flows down to the bottom and begins to interact with the raw materials in the big bags. Liquid metal begins to absorb raw materials in big bags, and at this moment the functional purpose of big bags ends and the process of melting, mixing and dissolving raw materials piled in big bags in liquid metal begins. At the same time, after the big bag melts, there is no spillage of small pieces of scrap through pieces of large pieces of scrap into a bath with liquid metal.

The developed method allows processing small-sized scrap with a particle size from 1 to 50 mm by 99%.

Thus, the localization of the raw material, packed in big bags, between the layers of scrap, its placement in the lower part of the CA closer to the bottom and / or the bath of liquid metal between the scrap, in combination, allows the present method to be used with great efficiency to obtain high quality steel in the CA. both with liquid and dry bath.

In addition, the implementation of the method also makes it possible to increase the efficiency of using small steel scrap metal and iron-containing product, which creates conditions for the use of a new type of raw material, not previously used fine iron and steel scale.

Claims (3)

1. A method of obtaining steel in a steel-making furnace, including loading into the furnace lumpy scrap and small lump iron-containing raw materials (MZhS), smelting until they are completely melted, dissolved and reduced in a liquid metal bath, characterized in that small-lump iron-containing scrap is used as MZhS, and / or fine iron, and / or scale, while before the start of melting, the calculated amount of small lump iron scrap and / or fine iron and / or scale is placed in containers of the big-bag type with their subsequent placement in the steel-making unit between the large-sized scrap in the lower part of the steelmaking unit closer to the bottom or bath of liquid metal. 2. A method according to claim 1, characterized in that medium and heavy scrap is used as large-sized scrap. 3. The method according to claim 1, characterized in that the placement of small lump iron scrap and / or fine iron and / or scale in the big bag is carried out together with metallurgical additives.

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