RU1786108C - Process for ladle treatment of metal - Google Patents

Abstract

The invention can be used in the after-furnace treatment of structural and other steel grades. Essence: after the end of the release of the intermediate product from the furnace, the slag chemical composition is calculated according to the calculation, the argon flow rate is set at 0.20-0.40 m / t-h and the intermediate is heated with arcs at a speed of 2-5 ° C / min until the temperature is reached , 50-90 ° C higher than the casting temperature of this steel grade, then under the bottom of the steel to its highest position, aluminum weighing 0.7-2.7 kg / t is introduced into the melt and the gas flow rate is increased by 0.6 -1.2 m3 / t-h for every 1 kg / t of aluminum alloyed, after reaching a temperature of 5-15 ° C higher th casting temperature, argon flow rate is reduced to 0.10-0.20 m3 / t h and metal is deoxidized with calcium weighing (0.2-0.6) -A kg / t, where AI is the mass of aluminum introduced into the ladle and the duration of the final part of the purge and the metal by argon (in min) is proportional to the mass (in kg / t) of the introduced calcium. with

Description

The invention relates to the field of ferrous metallurgy and can be used in the smelting of structural, tool and other steel grades. .

Known technologies for the smelting of these grades of steel in electric arc furnaces, in electric arc furnaces with out-of-furnace treatment (slag, argon, vacuum, their combination;).

The disadvantage of the first methods is the low quality of steel, the irrational use of the smelting unit, in the first place, a significant overheating of the metal in the arc furnace and the associated increased consumption of electricity and materials.

The closest in technical essence and the achieved positive effect to the proposed invention is a method of steel production, in which the intermediate product is smelted in an electric arc furnace with a given content of carbon and phosphorus, and all other operations for finishing steel by chemical composition, deoxidation is carried out in a ladle, and arc heating of the melt, intensified purge of metal with an inert gas. The disadvantages of the prototype:

   ,

1. The relatively high content of sulfur, oxygen and nitrogen in the refined metal, associated with the use of far from all the capabilities of the ladle-furnace assembly.

2. Non-guaranteed formation of non-metallic inclusions of a favorable shape in the finished steel, which leads to a decrease in the operational properties of the metal.

3. The increased consumption of electrodes.

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ABOUT

About 00

The purpose of the invention is to improve the quality of the metal by effectively removing sulfur, nitrogen, oxygen from the metal and the formation of non-metallic inclusions of a favorable shape in the refined metal. 5

This goal is achieved by the fact that after the end of the production of the intermediate product, the chemical composition of the slag is adjusted, the argon flow rate is set at 0.20- 0.40, and 10 intermediate is heated by arcs at a speed of 2-5 ° C / min until the temperature reaches 50-90 ° With a temperature higher than that of the casting, then the electrodes are raised to their highest position, 15 aluminum weighing 0.7-2.1 kg / t is introduced into the melt and the gas flow rate is increased by 0.6-1.2 m3 / t by each 1 kg / t of aluminum alloyed, after reaching a temperature of 5-15 ° C higher than the casting temperature, argon consumption 20 is reduced to 0.10-0.20 m3 / t h and metal is deoxidized with calcium weighing (0.2-0.6) AI kg / t, where AI is the mass of aluminum introduced into the bucket and the final the parts of the metal purge with argon (in mime) 25 are set proportional to the mass (in; |., .. kg / t) of the introduced calcium ;;.,: ,,.:;

Distinctive features of the invention are::; ..:: -, ..: ..,;: v .-- ..;,; .. h. ,;

1. After the end of the half-production, 30% product, the chemical composition is adjusted; .- va slag But to the calculation, establish the flow. . . argon 0.20-0.40 m3 / t and begin to heat the intermediate by arcs at a speed of 2-5 ° C / min until a temperature is reached that is 35-50-900C higher than the pouring temperature of this grade of steel. x V

2. Raise the electrodes to their extreme position; they introduce aluminum weighing 0.7-2.1 kg / t into the melt and increase 40 the gas flow rate by 0.6 g1.2 m3 / t for each. 1 kg / t of aluminum alloyed, after reaching a temperature that is 5-15 ° C higher than the casting temperature, argon consumption. . they are reduced to 0.10-0.20 m3 / t, and 45 metal is deoxidized with calcium weighing (0.2-0.6) AI kg / t, where AI is the mass of aluminum introduced into the ladle. .. / ;: -.

3. With an increase in the weight of the imparted aluminum, the calcium mass increases, and 50 the duration of the final part of the metal purge with argon (in min) is proportional to the mass (in kg / t) of the introduced calcium.

These distinguishing features are as follows, including and new properties. 55

Purpose of feature No. 1: in a minimally short time, form a highly axial, iron-free refining oslak in the goat, adjust the chemical composition of the metal and heat it with

the purpose of subsequent desulfurization. At the same time, provide a relatively low consumption of electrodes and lining of the unit (examples 1-5, table).

This is ensured by the priority operation in the ladle furnace - adjusting the chemical composition of the slag as calculated, the argon flow rate of 0.20-0.40 m / t.h and heated by arcs at a speed of 2-5 ° C / min until the temperature reaches 50-90 ° C exceeding the casting temperature of this steel grade.

If the formation of refining slag is moved to a later date, the consumption of materials increases due to an increase in the duration of steel processing in the furnace:.: ..; :.; ..

Consumption, argon less than 0.20 m3 / t. h does not provide sufficient mixing of the metal for its predetermined heating and the formation of the necessary refining slag during this period, more than 0.40 m3 / t - to unstable arc burning in the slag due to excessive movement of the melt, which leads to uncontrolled carburization of the metal. : - -; v--. . -.

Metal heating at a speed of more than 5 ° C / min to a temperature higher than the casting temperature of a given steel grade by more than 90 ° C and metal heating at a speed of 2 ° C / min to a temperature higher than the casting temperature of a given steel grade by less than 50 ° C, impractical. In the first case, due to a decrease in the durability of the lining of the unit, in the second, due to insufficient heating of the melt for subsequent desulfurization of the metal of a given degree.

The purpose of feature No. 2 is to increase the efficiency of removal of sulfur, oxygen from the metal with a relatively low consumption of argon and a decrease in the consumption of electrodes (see the group of examples No. 6-11, table). .,.,.;, ...,:, - - -

The divergence of aluminum and the subsequent purge rate are determined by the initial content of sulfur and oxygen in the metal at a given temperature range. And calcium input according to a given program (temperature, argon flow rate, aluminum content) basically provides a favorable type of non-metallic inclusions in the finished steel.

The introduction of aluminum weighing less than 0.7 kg / t into the melt and increasing the gas flow rate by less than 0.6 m / t.h for every 1 kg / t loaded, aluminum does not provide the necessary quality of steel even with a low pollution of sulfur and oxygen of the source metal and upon reaching a temperature less than 5 ° C higher than the casting temperature. In this case, a favorable form of inclusions is not achieved.

An additive in the mass of aluminum of more than 2.1 kg / t and an increase in gas flow by more than 1.2 m3 / t for every 1 kg / t of aluminum added leads to an increase in the consumption of ladle refractories and an increase in exogenous inclusions in the metal even when the temperature is reached, more than 15 ° C higher than the temperature of the casting. In this case, there is no possibility of the formation of a favorable form of inclusions even with a large mass of calcium being introduced.

Differentiated consumption of argon (depending on the weight of the loaded aluminum) allows to reduce its consumption when the specified quality is achieved.

An additive in calcium metal weighing more than 0.6 A kg / t at a temperature less than 5 ° C higher than the casting temperature and an argon flow rate of less than 0.10 m / t-h in the metal produces an unreasonable excess of calcium (expensive), leading to the formation of calcium sulfides, which degrade the spillability of steel.

Additive to calcium metal weighing less than 0.2 AI kg / t at a temperature exceeding 15 ° C higher than the casting temperature and an argon flow rate of more than 0.20 m / t-h in the metal leads to a calcium deficiency, which leads to the predominant formation in the metal . hard-melting hard-to-remove inclusions of the type that make casting difficult

Purpose of the characteristic N; 3 - guaranteed formation of non-metallic inclusions of favorable shape in steel to a less negative degree, affecting the exposure properties of the metal. This is achieved by adding a mass of calcium to the melt, consistent with the mass of previously introduced aluminum, and the duration of argon purging with a given intensity. In this case, liquid inclusions (readily removable) of the Ca02A 20z type and with a melting point below 873 ° C are formed. At the same time, the mechanical properties of the steel are improved, especially its viscosity and spillability of the metal (Examples 12 and 13, table).

If, with an increase in the aluminum content, the weight of the added calcium is reduced or, conversely, there is no guaranteed formation of oxygen-containing non-metallic inclusions of a given shape.

An increase in the purge time (6 min) is more than the weight of the introduced calcium (in kg / t) and less at a given argon flow rate. In the first case, due to excessive oxidation of calcium, in the second, due to increased pollution, they became non-metallic inclusions.

In the aggregate, signs 1-3 show a new property - a decrease in the nitrogen content in the finished steel.

It is known that when the metal is heated by arc, the mass fraction of nitrogen in it increases. Moreover, the lower the content of surface-active elements (sulfur, oxygen) in the metal, the more efficient the saturation with nitrogen.

In the prior art, arc heating in a ladle takes place before sulfur and oxygen are removed from the metal. During and after desulfurization and deoxidation, nitrogen is washed out with argon without arc heating, which also helps to reduce the nitrogen content in the finished steel.

Thus, the claimed features of the proposed invention, taken separately and in combination, allow their implementation to significantly improve the quality of steel in terms of sulfur and oxygen and to guarantee the formation of non-metallic inclusions of a favorable shape in the refined metal (see table).

An example of a specific implementation. Structural steel of the type ZOKHGSA, 50KHGA was smelted in 60 and 10Oelectrode furnaces. The mixture was melted in the melting unit, the metal was oxidized to the specified carbon, phosphorus and temperature contents. The bulk of the alloying elements were introduced into the furnace and / or into the ladle at the outlet. Then the intermediate in the installation was heated by arcs with simultaneous purging with argon. Slag and metal were adjusted with additives from slag-forming, alloying bunkers. The metal was deoxidized by aluminum and calcium by introducing these elements in the form of a wire using tribaterate.

Argon was introduced into the melt both from below through a ceramic plug and from above through a lined tube.

In order to determine the effect of the optimal limits of variation of the claimed parameters on the achievement of the object of the invention, the parameters fluctuated over a wider range. The change in the output parameters was evaluated by both direct and indirect measurements by standard methods.

Processing of the intermediate in the “ladle furnace” began with additives on the slag of lime, powdered coke, aluminum, fluorspar based on the formation in the ladle

highly basic reducing slag (basicity 2.5-3 (FeO + MnO) 10%) weighing 10-15 kg / t. Then, the argon flow rate was set at 0.10-0.50 m3 / t-h and arc melt heating was started at a rate of 6 ° C / min (by changing the input power). During heating, the metal was adjusted for chemical composition.

After reaching the metal temperature, by 30-110 ° C, exceeding the casting temperature of this steel grade, the electrodes were raised to the highest position, aluminum was introduced weighing 0.4-2.4 kg / t, the argon consumption was increased by 0.4-1.4 m ° / t-h for every 1 kg / t of aluminum seated. After reaching a temperature that was 0-20 ° C higher than the casting temperature of this steel grade, the argon flow rate was reduced to 0.05-0.25 m / t-h and metal was deoxidized with calcium weighing (0.1-0.7) AI kg / t . Moreover, with an increase in the mass of aluminum, the mass of calcium decreased and increased.

The duration of the final part of the purge (in min) with a flow rate corresponding to the mass of calcium introduced (in kg / t). For example: calcium was added weighing 0.6 kg / t, purge duration 0.60 min.

The effect of changes in the claimed parameters on the purpose of the invention is summarized, systematized and presented in the table.

The expected economic effect from the introduction of the inventive technology will be 4-6 rubles / ton of smelted steel.

Claims (1)

The claims A method for out-of-furnace metal refining, including smelting and releasing an intermediate in a ladle, arc heating of metal in a ladle, argon purging, desulfurization, deoxidation with aluminum and calcium, characterized in that, in order to improve the quality of the metal by effectively removing sulfur, nitrogen, oxygen and metal from the metal the formation of non-metallic inclusions of a favorable shape in the refined metal, after the end of the semi-product production, the chemical composition of the slag is adjusted, the argon flow rate is set to 0.20-0.40 m3 / t and preheated the intermediate product with arcs at a speed of 2-5 ° C / min until a temperature of 50-90 ° C is reached that exceeds the casting temperature, then the electrodes are raised to their highest position, aluminum weighing 0.7-2.1 kg / t is introduced into the melt and increase gas consumption by 0.6-1.2 m3 / t-h for each 1 kg / t of aluminum alloyed, after reaching temperatures 5-15 ° C higher than that of neoaTvov oazlivka argon waste is reduced to 0.10-0.20 m3 / gh and metal is deoxidized with calcium weighing (0.2-0.6) AI kg / t, where Al aluminum introduced into the ladle, and the duration of the final part of the metal purge with argon, in min, is set proportional to the mass, in kg / t, of calcium introduced. 1.40 / J10 0.150.4xA1 +  1.4 0.91.00.15 O. 1.40, -J100.15 u.feMV 1.4 0.9 100.15 C.ixAl 1.4 O. J10 0.15 0.4xA1 t, i 0.310 0.15 O.W.I + gerantir. 0.002 0.0015 0.007 485 increased, material consumption 0.0100.0026 0.007 + 0.0050.0020 0.007 bO 0; 0020.0015 0.007 + b5 35 110 0.002 0.0022 0.009 + maugle iron increase in long-term heating 0.00 0.0020 0.008 +90 0.002 0.0015 0.007 + 85 0.002 0.002J 0.009 + 85 decrease in lining resistance 0.014 0.003 0.00V + 85 0.007 0.0024 O. OU7 + 85 0.002 0.0015 0.007 + 85 0.002 0.0015 O.OOfcS 94 0.002 0.0026 0.010 105 sharp weslimsnis of consumptive electronic | about a Y) 0.30 3.5 70 1.4 0, y YU) 0.30 3.5 70 .4 0.3 h) 0.30 3.5 70 1.4 0, J 12) +0.30 3.5 70 13) 0.30 3.5 70 1.4 0, J 1.4 0.9 Continuation of the table unsatisfactory. raeliaka 0.15 O.xAl 0, OJ 0.10 0..15 O. ixAI 0, JO. . 0.25 0.002 0.002 0.003 0.0015 0.007 + 0.0015 0.007 + 0.0017 0.007 + 0.15 0.15 O.lxAl 0.2xAl O.llxAl 0.6xAl 0.7xL1 O. ixAI 0.15 O. lxAl deterioration steel deterioration of railroad bridge 0.002 0.001 0.007 + 0.002 0.0015 0.007 0.002 0.00) 8 0.007 0.002 0.0021 0.007 0.0055 0.0016 0.007 0.0035 0.0016 0.007 + 0.002 0.0015 0.007 0.002 0.0016 0.007 + 0.002 0. 0015 0.007 - 0.002 0.0047 0.007 - 0.002 0.0018 0.00 inclusions 85 85 85 85 85 85 90 65 85 85 85 85 85 85 5