RU2353667C1 - Manufacturing method of low-silicon steel - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to ferrous metallurgy field, particularly, it relates to manufacturing of low-silicon steel. Method includes steel melting in steelmaking unit, slag cut-off from the metal in the end of its discharge from steel-making unit into ladle, additive of slag-forming and alloying materials, deoxidisation and blowing off the metal in the ladle by inert gas. Metal is melt with carbon content more than 0.03%, it is implemented vacuum metal working in the ladle, it is added slag-forming materials, it is defined oxygen content in the metal. Then metal and slag are deoxidised by calcium-bearing and aluminium-bearing materials, while in the capacity of calcium-bearing material it is used calcium carbide, which is fed to the ladle with consumption depending on content of the oxygen in metal after the vacuum treatment, required content of the oxygen in the metal till empirically determined coefficient, and aluminium-bearing material feeding is implemented in the amount on the assumption of material re-calculation to content of pure aluminium and in the limit of the ratio CaC₂/Al_pure=1-7 and then it is implemented correction of steel chemistry.

EFFECT: increasing of metal grade from nonmetallics.

3 cl, 1 tbl

Description

The invention relates to ferrous metallurgy, in particular to the production of low-silicon steel, with the possibility of casting the resulting steel in continuous casting plants and ingots.

The closest in technical essence to the proposed method is a method of producing low-silicon steel, providing steel with a silicon content of up to 0.05% and sulfur up to 0.010%. A method for the production of low-silicon steel involves the release of the melt from the steelmaking unit into the ladle, slag cut-off when the melt is discharged into the ladle, complex metal processing when it is discharged into the ladle with the main lining by the addition of aluminum and calcium-aluminum alloys, slag-forming mixture, deoxidizing agents, alloying materials, and metal purging in the ladle after its release by neutral gas. At a content of 0.02-0.05% aluminum in the metal, a flux-cored wire is introduced with a filler from a mixture of granular calcium and aluminum powder (RU 2166550, C2, publ. 2001.05.10).

The disadvantages of this method are:

- increased consumption of aluminum, which is associated with the use of aluminum as the main deoxidizer;

- increased waste of aluminum-containing materials, because their input is carried out at a high oxygen content in the metal, which leads to increased contamination of the metal with aluminous non-metallic inclusions;

- low degree of desulfurization of steel - 41.6-63.6%.

The technical result of the invention is:

- increasing the degree of purity of the metal for non-metallic inclusions and reducing the consumption of aluminum, which is associated with a preliminary vacuum-carbon deoxidation with the removal of deoxidation products in the gas phase;

- the elimination of the formation of cell bubbles during crystallization of steel with an aluminum content in the finished metal of less than 0.01% (pseudo-boiling metal), which is associated with a greater degree of deoxidation of steel with a minimum consumption of aluminum-containing materials, obtaining a metal with an oxygen content of less than 15 ppm and (FeO) in less than 1.5% slag and casting without “tightening” the pouring glasses, which will allow casting this metal on a continuous casting machine;

- casting on machines of continuous casting of low-silicon metal blanks without “tightening” casting glasses with aluminum content in the finished metal of 0.01-0.05% (semi-quiet metal).

The specified technical result is achieved by the fact that in the method of producing low-silicon steel, including metal smelting, slag cut-off at the end of the release from the steelmaking unit into the ladle, the additive of slag-forming and alloying materials, deoxidation and purging of the metal in the ladle with an inert gas, according to the invention, the carbon-containing metal is melted more than 0.03%, vacuum processing of the unoxidized metal in the ladle is carried out, slag-forming materials are planted, the oxygen content in the metal is determined, then the metal and ak calcium-aluminum-deoxidized materials as the calcium-containing material is calcium carbide, which is fed to the ladle at a rate depending on:

m = 0.21 · (and _{o_nach} -a _{o_kon} ) ⁿ , kg / t,

where a _{o_nach} is the oxygen content in the metal after vacuum treatment, ppm,

and _{o_con} - the required oxygen content in the metal up to 15 ppm,

n is an empirical coefficient in the range of 0.3-0.5,

0.21 - empirical coefficient, kg / t * rrt,

and the supply of aluminum-containing material is carried out in an amount based on the ratio of CaC ₂ / Al _net = 1-7 (from the conversion of the material to the content of pure aluminum), then the chemical composition of the steel is adjusted.

The carbon content at the output of the intermediate from the steelmaking unit in the range of more than 0.03% allows vacuum-carbon deoxidation with carbon contained in the melt. At lower values, effective vacuum-carbon deoxidation will not be ensured.

The range of values of the flow of calcium carbide is determined by the dependence:

m = 0.21 · (and _{o_nach} -a _{o_kon} ) ⁿ , kg / t,

where a _{o_nach} is the oxygen content in the metal after vacuum-carbon deoxidation,

and _{o_con} - the required oxygen content in the metal up to 15 ppm,

n is an empirical coefficient in the range of 0.3-0.5, depending on the content of slag in the ladle,

0.21 - empirical coefficient, kg / t * ppm.

The feed into the ladle CaC ₂ according to this relationship allows you to get the required degree of deoxidation of steel. At lower values, the required degree of steel deoxidation will not be achieved. With large quantities, the necessary chemical composition will not be provided for the carbon content on low-carbon steel or on medium-carbon steels will lead to an excessive consumption of this material.

The range of flow rates of aluminum-containing materials during out-of-furnace treatment of the melt within the CaC ₂ / Al ratio _net = 1-7 is explained by the physicochemical laws of the metal and slag deoxidation process until the oxygen content decreases below 15 ppm. At high ratios, on a low carbon metal, the necessary oxygen content will not be provided while maintaining a low carbon content. At lower values, overconsumption of aluminum-containing materials will occur and on a metal with an aluminum content of up to 0.01% the specified chemical composition will not be provided.

The implementation of the technology of production of low-silicon metal according to the above method allows you to:

- to increase the degree of purity of the metal on non-metallic inclusions due to vacuum-carbon deoxidation and the use of calcium carbide as slag and metal deoxidant;

- reduce aluminum consumption, which is associated with a preliminary vacuum-carbon deoxidation with the removal of deoxidation products in the gas phase and the replacement of part of aluminum with calcium carbide;

- to exclude the formation of cellular bubbles during crystallization of steel with an aluminum content of less than 0.01% in the finished metal (pseudo-boiling metal), which will allow this metal to be cast on continuous casting machines. The exclusion of the formation of cellular bubbles is associated with a greater degree of deoxidation of steel and the production of a metal with an oxygen content of less than 15 ppm (0.0015%);

- to cast low-silica metal on continuous casting machines with aluminum content in the finished metal 0.01-0.05%, without “tightening” the pouring glasses, which is due to the low level of metal contamination by inclusions based on Al ₂ O ₃ and is confirmed by high absorption of aluminum made of aluminum alloy wire.

The following is an embodiment of the invention that does not exclude other variations within the scope of the claims.

Method for the production of low-silicon steel 08A with the required chemical composition, wt.%: C≤0.1; Si≤0.03; Mn = 0.35-0.6; S≤0.025; P≤0.025; A1≤0.01 is as follows.

The intermediate was smelted in a shaft furnace with a volume of 150 tons.

The resulting chemical composition of the molten metal at the outlet is, wt.%: C = 0.05; Si = 0.004; Mn = 0.10; S = 0.043; P = 0.007. During the release of metal from the furnace into the ladle, slag was cut off.

Then, the melt was evacuated at the UVS installation for 20 minutes.

The chemical composition of the melt after evacuation of the metal, wt.%: C = 0.006; Si = 0.003; Mn = 0.10; S = 0.036; P = 0.007.

Next, slag-forming materials were planted in the bucket: lime in the amount of 6.5 kg / t and 4 kg / t of fluorspar, to guide highly basic fluid-moving slag. The oxygen content of the metal was measured, which was 240 ppm (0.024%). After the slag was introduced into the ladle, deoxidizers — calcium carbide — were placed at a flow rate determined by dependence, which is:

m = 0.21 · (240-10) ^0.5 = 3.18 kg / t, based on the necessary oxygen content of 10 ppm, and an aluminum section in the amount of 0.64 kg / t.

To obtain the desired chemical composition, manganese metal was used, which was planted in an amount of 3.92 kg / t, aluminum wire was introduced in an amount of 0.038 kg / t based on aluminum production of not more than 0.01%, followed by a ferrocalcium wire in an amount of 0.9 kg / t, calculated on pure calcium.

During the period of evacuation and out-of-furnace metal processing at the ladle furnace (CCP), the metal was purged with inert gas with argon.

As a result of the treatment, steel with a final chemical composition was obtained, wt.%: C = 0.05; Si = 0.014; Mn = 0.50; S = 0.007; P = 0.009; Al = 0.006.

The metal was poured on a high-quality continuous casting machine into a round billet, the casting took place without tightening the pouring glass, and no “cellular bubbles” formed during crystallization.

The table shows examples of the method of production of steel with its processing in a ladle with various technological parameters.

In the 1st, 2nd and 6th examples, the desired technical result described in the invention is not achieved due to deviations from the specified technology.

Examples 3, 4 and 5 due to the observance of the technological parameters of the invention are optimal for achieving the required metal oxidation, which eliminates the formation of cell bubbles during crystallization of pseudo-boiling metal (with aluminum content up to 0.01%), and a metal with a regulated aluminum content (0 , 01-0,05%) - cast on a continuous steel casting unit without "tightening" the pouring glass. The resulting metal is characterized by a high degree of purity for non-metallic inclusions, and in the production of it significantly reduced aluminum consumption.

Options Examples one 2 3 four 5 6 The carbon content before evacuation of the metal,% 0.05 0.05 0,035 0,07 0.15 0.02 The oxygen content after vacuum-carbon deoxidation, ppm 120 93 150 220 fifty 455 Calcium carbide consumption, kg / t 0.54 1.23 1,52 1.78 0.92 2.41 Aluminum consumption (in terms of pure aluminum), kg / t 0.23 2.46 0.51 0.59 0.31 0.83 The oxygen content after deoxidation, ppm 39 3 9 12 7 fifteen Duration of processing at the ladle furnace installation, min thirty 35 35 40 35 65 Absorption of aluminum,% 57 85 83 80 85 80 Result Low consumption of calcium carbide leads to the formation of honeycomb bubbles during the casting of metal with a regulated aluminum content and the "tightening" of the pouring glasses due to the low absorption of aluminum The increased consumption of aluminum leads to the production of steel with an Al content of> 0.01% and increased metal contamination with Al ₂ O ₃ inclusions, and the impossibility of casting it on the UNRS Semi-technical result according to the invention The technical result of the invention is obtained. The technical result of the invention is obtained. Violation of the technology (low carbon content before release from the steelmaking unit) leads to an increase in deoxidant costs and the duration of processing on the CPC

Claims (3)

1. Method for the production of low-silicon steel, including smelting metal in a steel-smelting unit, cutting off slag from metal at the end of its release from a steel-smelting unit into a ladle, additive of slag-forming and alloying materials, deoxidation and purging of metal in a ladle with inert gas, characterized in that the metal is smelted with carbon content of more than 0.03%, vacuum processing of the metal in the ladle, slag-forming materials are planted, the oxygen content in the metal is determined, then the metal and slag are deoxidized with calcium conductive and aluminum-containing materials, wherein as a calcium-containing material is calcium carbide (CaC _2), which is fed to the ladle at a rate depending on
m = 0.21 (and _{o_nach} -a _{o_kon} ) ⁿ kg / t,
where a _{o_nach} - the oxygen content in the metal after vacuum treatment, mln ^-1 ;
and _{o_con} - the required oxygen content in the metal up to 15 million ^-1 ;
n is an empirical coefficient in the range of 0.3-0.5;
0.21-empirical coefficient, kg / t · mln ^-1 ,
and the supply of aluminum-containing material is carried out in an amount based on the conversion of the material to the content of pure aluminum within the ratio CaC ₂ / Al _net = 1-7, and then the chemical composition of the steel is adjusted. 2. The method according to claim 1, characterized in that they use calcium carbide with a mass fraction of calcium of 40-65%. 3. The method according to claim 1 or 2, characterized in that the mass fraction of aluminum in the aluminum-containing material is 18-100%.