Complex alloy for microalloying and deoxidation of steel based on iron

Abstract

FIELD: metallurgy; ferroalloy production.SUBSTANCE: invention which can be used in steelmaking for microalloying and deoxidation of metallic iron-carbon melt with boron. The alloy contains, wt.%: boron 1.0-1.9; aluminum 25-32; silicon 0.7-1.5; carbon 0.01-0.1; iron and impurities - the rest.EFFECT: high and stable absorption of boron due to the increased concentration of the chemically active element - aluminum, which expands the scope of its application for low-silicon steel grades.1 cl, 1 tbl

Description

[0001] The invention relates to ferrous metallurgy, namely to ferroalloy production, and can be used in steel smelting for its microalloying and deoxidation.

[0002] Using boron as a microalloying additive to steel improves its quality characteristics and allows it to replace scarce and expensive manganese, chromium, and nickel ferroalloys. However, this effect is observed within a narrow range of boron additions to steel, necessitating strict control over the amount of boron-containing material added.

[0003] In the domestic and foreign metallurgical industry, ferroboron with a content of 6-20% B is widely used for microalloying and deoxidation of steel. Its chemical composition, wt. %: B≥6, Si 2-10; Al 3-10; Fe - the rest (GOST 14848-69). In addition to low and uneven assimilation of boron (~75%), when introduced in lump form (Golubtsov V.A. Theory and practice of introducing additives into steel outside the furnace. - Chelyabinsk. - 2006. - 421 p.) this alloy has a high cost, since expensive and scarce charge materials are used for its production. For alloying steel, it is more rational to use alloys with a reduced boron content (up to 2%), which have chemically active components (Al, Ti, Si, etc.) in their composition. The advantages of such complex ferroalloys compared to traditional ones are the possibility of using cheaper charge materials and high technical and economic indicators in their production.

[0004] An alloy is known for deoxidizing and alloying steel, containing by weight %: silicon 30.0 - 45.0; aluminum 2.0 - 13.0; boron 0.5 - 3.0; calcium 0.6 - 3.0; titanium 3.0 - 8.0; iron is the rest (RU No. 2006513, IPC C22C 35 / 00, published 30.01.1994). The disadvantage of this alloy is the high silicon content, which significantly limits the use of the alloy for a wide range of steel grades and increases its cost.

[0005] A complex iron-based alloy for microalloying and deoxidation of steel is known, consisting of boron, silicon, aluminum, manganese and barium, wherein the specified components are taken in the following ratio, wt. %: boron 0.5-3.0; silicon 41.0-68.0; aluminum 1.0-2.5, manganese 0.2-0.4; barium 0.1-5.0; iron - the rest (EA No. 022416, IPC C22C 35 / 00, C21C 7 / 00, published 30.12.2015). The disadvantages of this alloy are a wide range of silicon content (41-68 wt. %) and a low degree of boron assimilation by steel - 71-72%.

[0006] A complex ferroalloy with boron is known, similar in composition to the proposed alloy, wt. %: boron 0.5-2.5; aluminum 10-15; silicon 50-60; iron and impurities - the rest (RU No. 2715510, IPC C22C 35 / 00, C21C 7 / 00. C22C 38 / 32, published 02 / 28 / 2020), which is taken as a prototype.

[0007] The maximum boron absorption rate by steel is 80-84%. The increased aluminum concentration in this alloy prevents its oxidation by dissolved oxygen, thereby ensuring a more complete boron transfer into the steel. However, the high silicon content of the alloy limits its use in the production of low-silicon steel grades, such as 08U, which contains 0.003% boron and 0.03% silicon.

[0008] The technical result of the proposed invention is that the claimed complex alloy with boron for deoxidation and microalloying of steel, containing a minimum number of elements, ensures high and stable absorption of boron due to the increased concentration of the chemically active element - aluminum, which expands the scope of its application for low-silicon steel grades, and a simple method for producing this alloy ensures low cost.

[0009] The specified technical result is achieved in that the complex alloy for microalloying and deoxidizing iron-based steel, containing boron, aluminum, silicon and carbon, according to the invention, contains the specified components in the following ratio, wt. %: boron - 1.0-1.9; aluminum - 25-32; silicon - 0.7-1.5; carbon 0.01-0.1; iron and impurities - the rest.

[0010] Based on experimental studies, it has been established that to achieve a boron concentration in steel of 0.001-0.003 wt.%, which is the most favorable for most steel grades, the ferroalloy must contain 0.5-1.9 wt.% boron. This concentration of boron in the alloying addition ensures its consistently high absorption by the steel without complicating its smelting process (simple lump addition). Lower boron content in the ferroalloy requires increasing its amount, while higher boron content reduces the physical mass of the ferroalloy, which, in turn, reduces the stability and degree of boron absorption by the steel due to the uneven distribution of ferroalloy pieces in the ladle.

[0011] Aluminum, which has a greater affinity for oxygen than silicon and boron, helps prevent the formation of nitrides and oxides of the latter, which increases the absorption of boron by steel. The presence of aluminum in the resulting alloy within the stated range (25-32 wt.%) improves the efficiency of the complex boron ferroalloy. The lower limit of aluminum content (25 wt.%) is sufficient to ensure a high degree of boron absorption into steel. The upper limit of aluminum (32 wt.%) is determined by the fact that this amount ensures the maximum absorption of boron by steel, and any further increase leads to increased production costs of the ferroalloy.

[0012] Silicon is an impurity, and its content in the alloy is 0.5-1.5 wt.%. These concentration limits are determined by the starting charge materials. Exceeding the upper limit (1.5 wt.%) is impractical, as it does not enhance boron uptake and limits the range of steel grades that can be processed.

[0013] Carbon is present as an impurity in the complex boron-containing alloy in an amount no greater than 0.01-0.1% by weight, which is determined by its concentration in the starting materials: the reducing agent, the ore, and the metal component. Exceeding the upper limit (0.1%) is inadvisable, as it promotes carbide formation and increases the carbon concentration in the steel after alloying.

[0014] The presence of iron in the alloy ensures a more uniform distribution and more complete absorption of the alloy components by the steel. The amount of iron in the alloy is determined by the technological conditions of the reduction smelting of boron-containing ferroalloy.

[0015] Example. Prototypes of a boron-containing ferroalloy were produced in a high-temperature laboratory electric furnace at 1500-1550°C by fusing the following charge materials: analytical grade carbonyl iron, primary aluminum, and FB17 ferroboron. Corundum crucibles were used as high-temperature vessels. To prevent oxidation of the charge components, the process was carried out in an inert argon atmosphere.

[0016] The charge materials were heated until completely melted, mixed, and held at the set temperature for 10 minutes. The melt was then poured into cast iron molds for subsequent air cooling. The compositions of the proposed alloy are presented in the table.

[0017] The process of steel microalloying with boron was carried out in a high-temperature electric furnace, using magnesia crucibles. The chemical composition of the steel corresponded to grade 32G1A, wt. %: 0.31 C; 1.05 Mn; 0.21 Si; 0.01 P; 0.006 S; 0.110 Cr; 0.11 Ni; the rest is iron and impurities.

[0018] Argon was used to create an inert atmosphere. The crucible containing the steel pieces was placed in the furnace and heated until the metal was completely melted.

[0019] After preliminary deoxidation of the metal, boron-containing ferroalloys were introduced into the molten steel through a 5 mm diameter quartz tube to achieve 0.005 wt.% boron in the finished steel. After holding for 20 minutes, the liquid steel was poured into steel molds, where it was cooled to room temperature.

[0020] A DFS-500 optical emission spectrometer was used to determine the chemical composition of the obtained steel ingots.

[0021] The ratio of the final concentration of boron in steel to its amount introduced by the ferroalloy was chosen as the criterion for the efficiency of determining the composition of a complex ferroalloy (the degree of boron assimilation):

[0022] K=[B c ] / [IN ф ]⋅100,

[0023] where B c - the amount of boron in steel treated with ferroalloy; Bф - the amount of boron in the introduced ferroalloy.

[0024] Table - Compositions of complex alloys and the degree of boron absorption by steel

[0025] № Chemical composition of ferroalloys, wt.% Boron absorption rate of steel (K) Ferroalloy additive mass Note B Al Si C Fe* 1 0,55 30,9 0,60 0,04 67,9 82 0,91 Beyond the formula 2 1,12 29,7 0,75 0,04 68,4 88 0,45 Within the formula 3 1,55 28,8 1,40 0,04 70,3 92 0,33 Within the formula 4 1,89 29,4 1,17 0,05 67,46 91 0,26 Within the formula 5 2,46 28,5 1,22 0,07 67,8 85 0,20 Beyond the formula 6 1,45 20,1 1,05 0,07 77,3 81 0,34 Beyond the formula 7 1,42 25,4 0,79 0,07 71,8 88 0,34 Within the formula 8 1,59 30,8 0,89 0,05 66,7 91 0,31 Within the formula 9 1,62 36,5 1,15 0,04 60,6 90 0,17 Beyond the formula 10 1,2 14 51 0,3 33,5 84 0,41 Prototype * The rest is Fe and impurities.

[0026] The degree of absorption of the leading elements of a complex alloy by steel is the main characteristic affecting its consumption and the stability of the steel composition.

[0027] The table shows that the best indicators of the degree of boron transfer into steel are observed when using samples 3, 4, 8 and 9. Sample 10 (prototype), despite the high total concentration of silicon and aluminum, provides a degree of boron transfer into steel of 84%.

[0028] The boron concentration in the range of 1.0-1.9 wt.% is due to the fact that at a boron content of less than 1.0 wt.% (sample 1), the mass of the introduced ferroalloy increases, leading to cooling of the steel being processed. When the boron concentration in the alloy exceeds 1.9 wt.% (sample 5), the mass of the ferroalloy additive decreases, which in turn leads to an uneven distribution of lumps in the liquid melt and negatively affects the degree of boron absorption by the steel, reducing it to 85%.

[0029] The aluminum content within 25-32 wt.% is necessary to prevent the oxidation of boron, since when the aluminum content is less than 25 wt.% (samples 6), the degree of boron absorption by steel decreases to 81%, and when exceeding 31 wt.% (sample 9), the increase in the degree of boron absorption is insignificant relative to the alloy with a content of 31 wt.% (sample 8), but it is more expensive.

[0030] Thus, the proposed alloy differs from the prototype by significantly increasing (by 7-8%) the boron uptake rate of steel. The complex alloy does not contain a large amount of silicon, allowing for a wider range of steel grades to be processed. Furthermore, it does not contain expensive alloying elements, is simpler to manufacture, and is less expensive.

Claims

A complex alloy for microalloying and deoxidizing iron-based steel, containing boron, aluminum, silicon and carbon, characterized in that it contains the said components in the following ratio, wt.%: boron 1.0-1.9; aluminum 25-32; silicon 0.7-1.5; carbon 0.01-0.1; iron and impurities - the rest.