A product and method for direct alloying of molten steel

Abstract

This invention discloses a product and method for direct alloying of molten steel, belonging to the field of metallurgical technology. The invention involves mixing fine powders of natural or carefully selected enriched alloying element compounds with fine powders of dispersants that isolate direct alloying materials and promote the rapid disintegration and dispersion of monomeric materials after addition to molten steel. This mixture is then packaged into a single product and added to the ladle before or at the beginning of tapping. Utilizing the combined and promoting effects of the deoxidizers used in the normal deoxidation and alloying process of the large amount of molten steel added simultaneously, as well as the finished alloying materials from other element alloying processes, the metallization process of the direct alloying elements in the alloying compounds is completed under the favorable thermodynamic and kinetic conditions of the iron bath during the early stages of tapping. This achieves direct alloying of molten steel using alloying compounds. After the product of this invention is added to the ladle in one go according to the method described in this invention, the direct alloying process of the molten steel requires no additional related auxiliary facilities or operations.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical technology, and more specifically, relates to a product and method for direct alloying of molten steel. Background Technology

[0002] The process of directly alloying molten steel by adding alloying element compounds (mainly alloying element oxides) to the ladle eliminates the high-energy-consuming and highly polluting finished ferroalloy production process. The negative impact indicators in terms of related resource consumption, energy consumption, environmental pollution, and occupational hazards are far superior to the traditional process of alloying molten steel and other liquid metals with finished ferroalloys. It is an important direction for improving liquid metal alloying processes that metallurgists have been dedicated to researching, developing, and experimenting with for nearly seventy years.

[0003] In recent years, there have been reports of experiments and even pilot productions of direct alloying with oxides of tungsten, molybdenum, chromium, manganese, or vanadium-containing special steels during tapping or refining. Some scholars have also compiled detailed summaries, such as Mr. Jorge Madias, Metallurgical Engineer, Director, Metallon, San Nicolas, Buenos Aires, Argentina, in his paper "Technical Contribution to the 49°Seminário de Aciaria, part of the ABM Week, October 2nd-4th, 2018." Paulo SP, Brazil, in his article titled "Direct Alloying of Steel: A Review of Plant Experiences and Lab Studies," systematically summarized the advantages of directly alloying molten steel with alloying element compounds. Despite numerous methods and achievements developed during long-term research, its application in large-scale industrial production remains limited. The direct alloying of molten steel with alloying element compounds is still constrained by the following issues:

[0004] 1. Most existing methods involve adding the oxides of alloying elements and the corresponding amount of reducing agents to the molten steel after forming them into blocks. The metallization reaction is carried out in the open within the molten steel and its slag system. Because the molten steel contains a high amount of oxygen, the added reducing agent is greatly consumed. The reaction environment and conditions for direct alloying are very unstable, resulting in poor element metallization, low alloy reduction rate and large fluctuations.

[0005] 2. In existing methods, after the oxides of alloying elements enter the molten steel, the reduction reaction process is mainly a solid-solid reaction between the direct alloying element compound and the reducing agent inside the block, or a molten reduction reaction between the direct alloying compound and the reducing agent after entering the slag in the furnace (ladle). The thermodynamic and kinetic conditions of the reaction are poor, resulting in low efficiency.

[0006] 3. In existing direct alloying attempts, the alloying element oxide material blocks used for direct alloying have high strength. After being added to molten steel, they will float on the surface of the molten steel due to the density difference between them. Because the slag cannot be quantitatively controlled, the direct alloying material is easy to enter the slag and become slag-forming, and it is difficult to be reduced and thus suffers losses.

[0007] 4. Existing methods mostly involve adding the direct reducing element compound into the furnace for melting and reduction, or undergoing a certain melting and reduction process. The reduction process is time-consuming and requires the use of corresponding metallurgical equipment, making the operation complex and cumbersome, which cannot meet the increasingly efficient requirements of steelmaking production.

[0008] 5. Among the existing attempts, none of them have been able to systematically and systematically make full use of the existing deoxidizers and other alloying elements in molten steel to reduce the compounds of direct alloying elements. Summary of the Invention

[0009] 1. The problem to be solved

[0010] The purpose of this invention is to overcome the problems of existing methods for directly alloying molten steel with compounds, such as complex and cumbersome solid-solid reduction or molten reduction processes, low reduction efficiency, and poor stability. This invention provides a product and method that utilizes a direct microscopic solid-liquid reaction design, leveraging existing deoxidizers and other alloying materials in the molten steel to promote and achieve immediate and efficient alloying of molten steel with direct alloying compounds before tapping. The technical solution of this invention can rapidly complete the alloying of molten steel during normal tapping without any subsequent auxiliary processes, thus replacing finished ferroalloys in one step and achieving immediate and direct alloying of molten steel with compounds.

[0011] 2. Technical Solution

[0012] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0013] The present invention discloses a product for direct alloying of molten steel, which is a block structure or packaging monomer formed by mixing natural or selected enriched and pre-purified compound powder as a direct alloying element source with dispersant powder.

[0014] Furthermore, the compound powder may be selected from at least one of oxides or salts containing tungsten, molybdenum, cobalt, niobium, chromium, boron, tantalum and vanadium, or may be directly alloyed with more than one element at the same time.

[0015] Furthermore, when the product is manufactured using a compression molding method to produce monomers, an appropriate binder needs to be added to the product.

[0016] Furthermore, the dispersant serves to isolate the direct alloying materials and promote the rapid disintegration and dispersion of the material monomers after they are added to the molten steel, and its weight ratio to the direct alloying compound powder is 0 to 0.2.

[0017] Furthermore, the dispersant is a gas-generating material that undergoes a chemical reaction and / or a gas-generating material that undergoes a decomposition reaction.

[0018] Furthermore, the chemical reaction-type gas-generating materials include carbon, etc., and the decomposition reaction-type gas-generating materials include carbonates, metal nitrides, alkaline earth metal hydroxides, etc.

[0019] Furthermore, the dispersant can also function as a reducing agent in the metallization reaction of direct alloying element compounds. For example, metallic silicon in carbon or silicon nitride during a metallization reaction that is a reduction reaction.

[0020] Furthermore, when the inherent deoxidizer of molten steel or other elemental alloying materials already contain the reducing agent required for direct alloying of molten steel, no reducing agent needs to be added to the product; when the inherent deoxidizer of molten steel and other alloying materials do not contain or contain only insufficient amount of reducing agent required for direct alloying of molten steel, sufficient reducing agent is added to the product in combination with the reducing ability of the dispersant.

[0021] This invention discloses a method for direct alloying of molten steel. 1) For thermally decomposable direct alloying element compounds whose decomposition products are undesirable to enter the molten steel, the aforementioned products are pre-added to the ladle before tapping. Then, at the start of tapping, all or part of the deoxidizer, other alloys, and supplementary reducing agent for inherent alloying of the molten steel are added to the ladle. Since alloying of molten steel inherently requires the addition of deoxidizers, other alloys, and reducing agents, the product of this invention can fully utilize materials that already need to be added to the molten steel to alloy the target direct alloying element, eliminating the need for additional addition to the product. From a production cost perspective, this is undoubtedly the most economical method.

[0022] Or 2) For thermally decomposable direct alloying element compounds and other types of direct alloying element compounds whose decomposition products are desired to enter the molten steel, all or part of the deoxidizer, other alloys and supplementary reducing agents for the inherent alloying of the molten steel are added to the ladle before or at the beginning of tapping, and the above products are also added to the ladle at the same time as the start of tapping.

[0023] Furthermore, the supplementary reducing agent is a supplementary component made by using one or more deoxidizing and alloying materials of other elements that were originally present in the molten steel to supplement the reducing material that has been added to the dispersant but is not yet sufficient to fully reduce the portion of the direct alloying element. This supplementary component is added to the ladle along with other existing deoxidizing and alloying materials in the early stage of the tapping process.

[0024] Furthermore, the supplementary reducing agent is used to replenish the inherent deoxidizing and alloying materials in the molten steel that are borrowed and consumed by the direct alloying materials. The total oxygen content bound by the deoxidizing elements in the supplementary reducing agent and the reducing agent and dispersant in the product is balanced with the total oxygen content bound by the target element and all elements in the direct alloying element compound whose oxygen binding force is weaker than that of the target element.

[0025] Furthermore, in this invention, the reduction of the direct alloying element in the direct alloying compound of molten steel is mainly achieved by utilizing and aiding the following simultaneously added to the ladle: 1) the existing deoxidizer in the molten steel, 2) alloying materials of other elements in the molten steel that have a stronger oxygen binding force than the direct alloying element, and 3) supplementary reducing agent, under iron bath conditions at the beginning stage of the tapping process.

[0026] 3. Beneficial effects

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] (1) The present invention provides a product for direct alloying of molten steel, which uses natural or selected enriched and pre-purified compound powders as the source of direct alloying elements. The dispersant powder is mixed and then pressed or packaged into a single unit, which is added to the ladle at once to achieve direct alloying of the molten steel. Simultaneously, the product of the present invention utilizes the high relative concentrations of deoxidizing and deoxidizing alloying elements such as carbon, silicon, and aluminum in the molten steel during the early stages of tapping to reduce the direct alloying element compounds. The thermodynamic and kinetic conditions of the reduction reaction are favorable, overcoming the problems of slow slag dissolution of high-melting-point compounds, poor thermodynamic conditions of molten reduction, and overall poor reduction kinetic conditions encountered in previous attempts. This results in a higher degree of metallization, a shorter direct alloying process time, and a higher and more stable metal yield. Furthermore, it should be noted that a reducing agent can also be added to the product; however, from the perspective of optimal alloying cost, using reducing materials added during the alloying treatment of non-target elements in the molten steel to complete the alloying process of the target direct alloying element is the most economical.

[0029] (2) The present invention provides a product for direct alloying of molten steel. By adding a dispersant, such as carbon or other high-melting-point reduction reaction gas-generating or decomposition gas-generating fine powders, the dispersant effectively isolates and prevents the agglomeration of the direct alloying element compound fine powders after being added to the molten steel, and promotes the disintegration and dispersion of the lumps after being added to the molten steel, thereby facilitating the instantaneous attainment of a high-temperature state conducive to the metallization reaction. Simultaneously, by selecting the dispersant, it can also function as a reducing agent for the direct alloying element compound.

[0030] (3) The present invention provides a method for directly alloying molten steel. When the amount of molten steel in the ladle is small at the beginning of the tapping process, the product of the present invention is added. Taking advantage of the fact that there is basically no slag in the early stage of the tapping process and the strong kinetic energy of the tapping steel flow generates good stirring, the floating matter on the surface of the molten steel is mixed with the molten steel by the circulation of the molten steel. In the molten steel with basically no slag, the metallization of the target alloying element is carried out directly with the help of the existing deoxidizer, other alloys and direct alloying elements in the reducing agent, which are all at a high concentration. This effectively improves the metal yield of the target alloying element and the yield fluctuation is small.

[0031] (4) The present invention provides a method for directly alloying molten steel. After the product of the present invention is added once, no additional auxiliary facilities or operations are required. The direct alloying process of molten steel is simple and convenient, making the application and promotion of direct alloying of compound molten steel possible. Furthermore, compared to the current industry practice of using finished ferroalloys, direct alloying of compounds significantly shortens the reduction path, protects resources, reduces pollution, and lowers energy consumption, resulting in substantial economic and social benefits. Detailed Implementation

[0032] To address the shortcomings of the direct alloying processes for molten steel described in the background art, this invention provides a direct alloying product and method for molten steel. By designing the alloying reaction process as a solid-liquid reaction, and utilizing the existing deoxidizing and other elemental alloying materials in the molten steel, along with the strong stirring of the molten steel during tapping and the real-time dissolution of the direct alloying elements, the metallization of the direct alloying element compounds is promoted fully and immediately.

[0033] Specifically, the product of this invention uses natural or carefully selected enriched and pre-purified compound powders as the direct alloying element source. The dispersant powder is mixed and then pressed or packaged into individual packaging units, wherein the particle size of the filling material is no greater than 400 μm. The compound used as the direct alloying element source mainly employs at least one of the following elements: tungsten, molybdenum, cobalt, niobium, chromium, boron, tantalum, and vanadium, whose binding capacity with oxygen at molten steel temperatures is less than that of metallic silicon and carbon. The dispersant uses a combination reaction-type gas-generating material and / or a decomposition reaction-type gas-generating material. The combination reaction-type gas-generating material is selected from carbon; the decomposition reaction-type gas-generating material includes carbonates, metal nitrides, and alkaline earth metal hydroxides. The addition of the dispersant provides a certain degree of isolation, effectively preventing the fine powder of the direct alloying element compound from clumping after being added to molten steel and promoting the disintegration and dispersion of the lumps after being added to molten steel. Even better, if the added dispersant can also function as a reducing agent or bulk binder for direct alloying element compounds, it can replace the addition of other reducing agents or binders when manufacturing products.

[0034] It should be noted that when the product is manufactured into monomers using compression molding, appropriate binders and dispersants need to be added to the product. However, when the product is directly packaged into a single packaging monomer, no binder needs to be added. Furthermore, if the direct alloying element (target alloying element) source used in the product itself functions as a dispersant, no or only a small amount of dispersant may be added to the product.

[0035] Furthermore, there are two specific scenarios regarding whether or not a reducing agent is added to the product:

[0036] (1) From the perspective of cost optimization, when the deoxidizer or other element alloying material of molten steel already contains the reducing agent required for direct alloying of molten steel, there is no need to add reducing agent to the product. In actual production, when molten steel is subjected to inherent alloying treatment, the added deoxidizer and / or reducing agent used for the reduction of other element alloying materials can be increased.

[0037] (2) When the inherent deoxidizer of molten steel and other alloying materials do not contain or contain only insufficient amount of reducing agent to be used for direct alloying of molten steel, sufficient reducing agent is added to the product in combination with the reducing ability of the dispersant to ensure the alloying effect of the direct alloying elements.

[0038] Based on the specific required dosage of reducing agent and the reducing function of the dispersant itself, the total oxygen content bound by the deoxidizing elements in the reducing agent and dispersant is denoted as n1, and the total oxygen content bound by the target element and all elements with weaker oxygen binding force than the target element in the direct alloying element compound is denoted as n2. The molar ratio of n1 to n2 should satisfy the range of 0 to 1.0.

[0039] Furthermore, a suitable amount of reducing agent can be added to the product of this invention according to actual needs or personal ideas. However, from the perspective of optimal economic cost, the materials required for alloying other elements inherent in molten steel should be utilized as much as possible (these materials can be used for alloying treatment of the target alloying element). This is because such processing is the most economical in terms of production cost, packaging cost, and transportation cost.

[0040] The present invention provides a method for directly alloying molten steel, which, based on the influence of the metallization reaction products of the direct alloying element compounds on the molten steel, can be selected as two methods of adding direct alloying materials to the ladle.

[0041] One method is as follows: For thermally decomposable direct alloying element compounds, especially when it is undesirable for their decomposition products to enter the molten steel, the product of the present invention is added to the ladle in advance while waiting for the steel to be tapped, and then all or part of the deoxidizer, other alloys and supplementary reducing agents for the inherent alloying of the molten steel are added to the ladle at the beginning of the tapping.

[0042] The second method is as follows: when it is desired that the reduction products of the alloying element compounds be directly introduced into the molten steel, all or part of the deoxidizer, other alloys and supplementary reducing agents for the inherent alloying of the molten steel are added to the ladle before or at the beginning of tapping, and the product of the present invention is added at the beginning of tapping.

[0043] In a more optimized form, for the supplementary reducing agent of the added direct alloying element compound, one or more deoxidizing alloying materials required by other elements existing in the molten steel can be used as supplementary reducing agents of the direct alloying element compound, so that the total oxygen content bound by the elements in the supplementary reducing agent and dispersant is balanced with the total oxygen content bound by the target element and all elements in the direct alloying element compound whose oxygen binding force is weaker than that of the target element.

[0044] The selection of supplementary reducing agent needs to be designed and selected according to the specific requirements of carbon increase, temperature control, additional slag amount and slag characteristic control in the direct alloying process of different steel grades. The ratio of carbon to metal in the supplementary reducing agent should meet the requirement of 100%-0%:0%-100%. That is, the supplementary reducing agent can be one or a combination of two of carbon or metal.

[0045] Furthermore, the alloying reaction process of the direct alloying element compound of the present invention simultaneously utilizes 1) steel deoxidation, and at the initial stage of tapping, all (or most) of the other element alloying materials and the added direct alloying element supplementary reducing agent have been added to the small amount of steel in the ladle and melted (or dissolved) to form a high concentration; 2) at the beginning stage of tapping, the falling steel flow strongly stirs the small amount of steel in the ladle rich in deoxidized alloying materials and mixed with direct alloying compound materials, and the alloying elements and alloying process are completed in real time under the condition of low slag iron bath at the initial stage of tapping.

[0046] The basic principle and design concept of this invention are as follows: First, it has the following advantages in terms of reaction thermodynamics: 1) Utilizing and taking advantage of the relatively large quantity of molten steel containing deoxidizing and other alloying materials, when only a small amount of molten steel is available at the beginning of tapping, the concentrations of various deoxidizing and alloying elements are at a high level. Then, the elemental metallization of the alloying element compounds can be carried out directly, and the reaction conditions are relatively sufficient and stable, which is conducive to improving and stabilizing the yield of direct alloying elements; 2) Utilizing the role of the dispersant, the direct alloying material blocks disintegrate and disperse and are encapsulated by the molten steel at the beginning of contact with the molten steel, instantly reaching a high temperature state conducive to the metallization reaction of the direct alloying element compounds; 3) Utilizing the characteristic that molten steel can form a high-temperature solid solution with various possible direct alloying elements, good conditions are formed for real-time absorption of reaction products and promotion of reaction depth.

[0047] Secondly, in terms of kinetics, it has the following advantages: 1) In the initial stage of tapping, the amount of molten steel in the ladle is small, and the concentration of various reactants contained in the added direct alloying materials, existing deoxidizers, other alloys, and direct alloying elements supplementing the reducing agent in the molten steel is the highest; 2) In the initial stage of tapping, the low molten steel level in the ladle results in a large drop in the tapping steel flow, and at the same time, the deep molten steel level in the furnace, under the superimposed potential energy conversion, the kinetic energy of the tapping steel flow on the molten steel in the ladle is very high; 3) In the initial stage of tapping, the small amount of molten steel in the ladle, the strong stirring of the tapping steel flow, makes the added direct alloying materials and existing deoxidizers, other alloys, and direct alloying elements supplementing the reducing agent at the highest concentrations of various reactants. The molten steel containing deoxidizers, other alloying materials, and direct alloying elements has a high degree of turbulence in its flow. The substances contained therein are fully mixed and have a high circulation rate. The metallization reactants and reaction products of the direct alloying elements in the molten steel diffuse and exchange rapidly at the reaction interface with the flow of the molten steel, resulting in excellent mass transfer conditions. 4) Under the action of the dispersant, the blocks of direct alloying materials disintegrate and disperse as soon as they come into contact with the molten steel. The various reactants wrapped in the molten steel have a large contact surface area, which is conducive to the rapid progress of the metallization reaction.

[0048] Finally, in terms of reaction engineering, it has the following advantages:

[0049] 1) Under iron bath conditions, let the total amount of direct alloying element compounds in the direct alloying element metallization reaction be X, and their concentration (denoted as Xc). Let the concentration of a certain deoxidizer or alloying element Yi (denoted as yci) be denoted as yci) , and the amount of molten steel in the ladle be Q. Then, we have xc = X / Q or yci = Yi / Q. The product xc*yic or (xc)n*(yic)m (where m and n are the balancing coefficients of the reactants in the corresponding reaction formulas) is the chemical potential that promotes the direct alloying element metallization reaction. As the amount of molten steel in the ladle increases during the tapping process, the chemical potential for the reaction continuously decreases. Obviously, it is necessary to add more reactants to the ladle as early as possible before tapping and at the beginning of tapping to obtain the chemical potential for the direct alloying element compound metallization reaction as early as possible. In practice, it is best to add all relevant deoxidizing and alloying materials before the tapping amount reaches 10%.

[0050] 2) Typically, before the end of tapping, the slag in the ladle mainly consists of deoxidation products from the high-oxygen molten steel flowing into the ladle from the steelmaking furnace, and this amount increases as more molten steel enters the ladle. In the early stages of tapping, due to the smaller total volume of molten steel in the ladle, the corresponding amount of deoxidation products is also smaller. This reduces the loss of the added direct alloying element compounds through melting and slagging in the slag. Furthermore, under the strong stirring of the tapping steel flow, a small amount of direct alloying element compounds may be slagged into the slag and repeatedly broken up and entrained by the molten steel, continuously reacting with the deoxidizing alloying elements in the molten steel to form metals and dissolve into the molten steel, ensuring a relatively small loss rate of direct alloying elements.

[0051] 3) Compared with the direct alloying process in which the main reaction is designed as molten reduction or solid-liquid reaction in the interior of the reactant mixing block, the metallization of the direct reducing element in the early stage of steel tapping can take advantage of the iron bath conditions of the tapping steel to achieve a high-concentration, high-temperature, high-mass-transfer and high-yield solid-liquid reaction system in the ladle composed of all the reactants and the existing steel.

[0052] The present invention will be further described below with reference to specific embodiments. It should be noted that, since vanadium is the element with the strongest oxygen affinity among the many elements applicable to the immediate direct alloying of molten steel, theoretically, the method applicable to the direct alloying of vanadium compounds can achieve the same or better yield results for other applicable direct alloying elements, especially for those elements whose oxygen affinity is weaker than that of iron.

[0053] Example 1

[0054] This embodiment describes the direct vanadium-nitrogen alloying of molten steel. Considering that the steel plant's existing alloying materials lack nitrogen-containing products, a nitrogen-enhancing agent needs to be added to the direct alloying material. Ferrosilicon nitride is selected as the nitrogen-enhancing agent. Since ammonium metavanadate itself has a certain dispersing effect due to ammonia decomposition, and ferrosilicon nitride also has an isolating effect to prevent material agglomeration and acts as a reducing agent, 98% pure ammonium metavanadate is used as the vanadium source, and 79% ferrosilicon nitride is used as a supplementary nitrogen source and dispersant. The ammonium metavanadate and ferrosilicon nitride are mixed in a 10:2 ratio, packaged, and bagged. The molar ratio of silicon in the ferrosilicon nitride to the vanadium-bound oxygen in the ammonium metavanadate is 0.29, and the total material weight is 0.73 kg. Before tapping from the medium-frequency furnace, the molten steel composition is 0.15% C, 0.06% Si, and the balance 0.003% V, with a basic nitrogen content of 30 ppm. The temperature is 1600℃, and the total tapping weight is 820 kg. Before tapping, 0.8 kg of aluminum, 2.5 kg of ferrosilicon, and 5.2 kg of ferromanganese, along with 0.24 kg of supplementary ferrosilicon to ensure complete equilibrium reduction of vanadium-bound oxygen in the vanadium compounds, were added to a 1-ton casting ladle. (This means the molar ratio of silicon in the ferrosilicon to vanadium-bound oxygen in ammonium metavanadate was 0.71, resulting in a total ferrosilicon addition of 2.74 kg before tapping.) All direct vanadium-nitrogen alloying materials were added to the ladle at the start of tapping, with all other operations remaining unchanged. The final ladle molten steel composition was accurate, with an alloy content of 0.031%, equivalent to a 94.2% recovery rate of alloying elements from the added direct alloying materials. The nitrogen content was 116 ppm, equivalent to a 63% recovery rate of nitrogen from the added direct alloying materials.

[0055] Example 2

[0056] This embodiment describes the direct alloying of vanadium in molten steel. 98% pure powdered vanadium pentoxide was used as the vanadium source, and anthracite powder with 88% fixed carbon was used as the dispersant (all materials have a particle size less than 400 μm). They were mixed in a 1:0.15 ratio, with a molar ratio of carbon to vanadium-bound oxygen in ammonium metavanadate of 0.56. After thorough mixing, the mixture was pressurized and sealed into a miniature, single-unit carbon steel sealed container with approximately 70*60*80 mm dimensions and a shell wall thickness of 0.35 mm. The total alloying material was 25.1 kg (38.6 kg gross weight including the sealed reactor shell). At the time of tapping from the converter, all the required deoxidizer, carbon powder, and direct alloying materials, as well as 2.95 kg of supplementary carbon powder to ensure complete equilibrium reduction of vanadium-bound oxygen in the vanadium compounds, were pre-added to the 45-ton ladle via a hopper. Other alloying materials were added simultaneously at the moment of tapping. The molten steel tapped from the converter had a residual vanadium content of 0.004%, a temperature of 1,595°C, and a total tapping volume of 45 tons. The final analysis showed that the vanadium content in the steel was 0.035%, which translates to a 96.0% recovery rate of alloying elements from the added direct alloying materials.

[0057] Example 3

[0058] This embodiment involves directly chromium alloying medium-carbon steel molten steel, replacing high-carbon ferrochrome. South African chromite with a Cr2O3 content of 45% and iron oxide (FeO) and Fe2O3 contents of 21% and 6%, respectively, is used. Anthracite powder with a fixed carbon content of 88% is added as a dispersant with reducing properties, at a ratio of 10% by weight of chromite, i.e., the ratio of source compound to dispersant is 0.1, and the molar ratio of carbon to chromium and iron-bound oxygen in the chromite is 0.56. 8.6 kg of chromite and 0.86 kg of anthracite are mixed, and then 0.43 kg of sodium silicate binder solution is added and mixed again. The mixture is then pressed into rectangular blocks approximately 40*30*50 mm in size, totaling 9.9 kg of alloying material. This material is added to a 1-ton casting ladle before tapping. The total steel output of the intermediate frequency furnace was 810 kg. Before tapping, 0.8 kg of pure aluminum, 2 kg of ferrosilicon with 75% silicon content, and 0.67 kg of ferrosilicon as a supplementary reducing agent were added to the ladle for deoxidation and alloying of the molten steel. The composition of the molten steel in the intermediate frequency furnace was 0.35% C, 0.18% Si, and 0.04% Cr. The final analysis of the ladle steel sample showed 0.38% C, 0.43% Si, and 0.34% Cr. The recovery rate of alloying elements in the added direct alloying materials was 90.9%, which is comparable to the recovery rate of the finished ferrochrome alloy.

[0059] Example 4

[0060] This embodiment describes a direct micro-chromium treatment of low-carbon structural steel molten steel, replacing micro-carbon ferrochrome alloys. South African iron ore with a Cr2O3 content of 45% (containing 21% FeO and 6% Fe2O3) was used as the chromium source, and calcium carbonate powder was used as the dispersant. No reducing agent was added (at this point, the molar ratio of the reducing agent to the chromium and iron-bonded oxygen in the directly alloyed chromite compound was zero). 9.6 kg of chromite (equivalent to 2.97 kg of pure chromium and 1.99 kg of total oxygen from iron and chromium) was mixed with 0.49 kg of calcium carbonate powder (dispersant ratio 0.05) and 0.49 kg of sodium silicate binder dilution solution, then pressed into rectangular blocks approximately 40*30*50 mm in size. The total alloying material was 10.5 kg, which was added to a 1-ton casting ladle before tapping. The total steel output of the intermediate frequency furnace was 900 kg. Before tapping, 0.8 kg of pure aluminum, 2 kg of ferrosilicon (75% silicon content), and 1.75 kg of ferrosilicon (75% silicon content) were added to the ladle as a supplementary reducing agent (at this point, the molar ratio of silicon to chromium and iron bound oxygen in chromite was 1.0). The steel composition of the ladle and the intermediate frequency furnace samples was C 0.05%, Si 0.05%, and Cr 0.03%. The final analysis of the ladle steel sample showed C 0.06%, Si 0.20%, and Cr 0.29%, which translates to an alloy element recovery rate of 88.7% from the added direct alloying materials, comparable to the recovery rate of the finished micro-carbon ferrochrome alloy.

[0061] Example 5

[0062] This embodiment describes the use of molybdenum alloying in molten steel as an alternative to ferromolybdenum alloy. Roasted molybdenum concentrate (MoO3) with a Mo content of 53% was used as the molybdenum source, and calcium oxide and anthracite powder with 88% fixed carbon were used as dispersants. The mixture was prepared in a ratio of 1:0.15:0.05 (dispersant ratio 0.2, molar ratio of carbon to oxygen in the molybdenum source 0.27). After thorough mixing, the mixture was sealed in an iron drum, with a total alloying material of 5.2 kg. Before tapping, this material was added to a 1-ton casting ladle and left to tap. The total steel output of the intermediate frequency furnace was 850 kg. At the beginning of tapping, 0.8 kg of pure aluminum, 2.5 kg of carbon raiser, 2 kg of low-carbon ferrosilicon with 75% silicon content, and 0.9 kg of carbon powder (containing 90% carbon) were added to the ladle for deoxidation and alloying of the molten steel. The composition of the molten steel in the ladle and the intermediate frequency furnace was C 0.05%, Si 0.06%, and Mo 0.03%, respectively. The final analysis of the ladle steel sample showed C 0.30%, Si 0.21%, and Mo 0.32%, which means that the recovery rate of alloying elements in the added direct alloying materials was 96.0%, which is comparable to the level of finished ferroalloys.

[0063] Example 6

[0064] This embodiment describes the direct alloying of vanadium in molten steel. Given the excellent dispersing effect of ammonium metavanadate due to ammonia decomposition, only 44.8 kg of 98% pure ammonium metavanadate was used as the vanadium source, directly bagged without reducing agents or dispersants (i.e., the molar ratio of reducing agent to vanadium-bound oxygen in ammonium metavanadate was 0, and the dispersant ratio was 0). It was added to a 45-ton ladle during the tapping process from the converter. Simultaneously, all other required deoxidizers, carbon powder, and direct alloying materials, along with 15.7 kg of supplementary carbon powder to ensure complete equilibrium reduction of vanadium-bound oxygen in the vanadium compounds, were added at the moment of tapping. The molten steel tapped from the converter had a residual vanadium content of 0.003%, a temperature of 1,595°C, and a total tapping volume of 45 tons. The final analysis showed a vanadium content of 0.035%, equivalent to a 93.5% recovery rate of alloying elements from the added direct alloying materials.

[0065] The present invention has been described in detail above with reference to specific exemplary embodiments. However, it should be understood that various modifications and variations can be made without departing from the scope of the invention as defined by the appended claims. The detailed description should be considered illustrative only and not restrictive, and any such modifications and variations shall fall within the scope of the invention described herein. Furthermore, the background art is intended to illustrate the current state of development and significance of the technology and is not intended to limit the present invention or the scope of application of the present application.

Claims

1. A method of direct alloying of liquid steel, characterized by: The product is added into the ladle before tapping or during tapping, and all or part of the deoxidizer, other alloying elements and additional reducing agent for inherent alloying of the molten steel are added into the ladle at the beginning of tapping; or all or part of the deoxidizer, other alloying elements and additional reducing agent for inherent alloying of the molten steel are added into the ladle before or at the beginning of tapping, and the product is added at the beginning of tapping; The product is a block structure or a packaged unit formed by mixing a powder of a natural or selected enriched and initially purified compound as a source of direct alloying elements with a dispersant powder; the compound powder is selected from at least one of oxides or salts of tungsten, molybdenum, cobalt, niobium, chromium, boron, tantalum and vanadium elements; When the inherent deoxidizer of the molten steel or other element alloying materials already contains the required reducing agent for direct alloying of the molten steel, the product does not need to add the reducing agent; when the inherent deoxidizer of the molten steel and other alloying materials do not contain or only contain insufficient amount of the required reducing agent for direct alloying of the molten steel, the sufficient amount of reducing agent is added in the product in combination with the reducing capacity of the dispersant; The total oxygen combined with the deoxidizing elements in the reducing agent and the dispersant is denoted as n1, the total oxygen combined with the target elements in the direct alloying element compound and all elements having weaker oxygen combination capacity than the target elements is denoted as n2, and the molar ratio of n1 to n2 is 0-1.

0.

2. A method of direct alloying of liquid steel according to claim 1, characterized in that: The additional reducing agent is used to compensate for the inherent deoxidizing and alloying materials consumed by the direct alloying materials; the total oxygen combined with the deoxidizing elements in the additional reducing agent, the product and the dispersant is balanced with the total oxygen combined with the target elements in the direct alloying element compound and all elements having weaker oxygen combination capacity than the target elements.

3. A method of direct alloying of liquid steel according to claim 1 or 2, characterized in that: The reduction of the direct alloying elements in the compound is mainly completed under the iron bath condition in the initial stage of the tapping process by means of the 1) inherent deoxidizer of the molten steel, 2) alloying materials of other elements having stronger oxygen combination capacity than the direct alloying elements and 3) additional reducing agent added into the ladle at the same time.

4. A method of direct alloying of liquid steel according to claim 1 or 2, characterized in that: The weight ratio of the dispersant to the direct alloying element compound powder is 0-0.

2.

5. A method of direct alloying of liquid steel according to claim 1 or 2, characterized in that: The dispersant uses a chemical reaction type gas generating material and / or a decomposition reaction type gas generating material.

6. A method of direct alloying of liquid steel according to claim 5, characterized in that: The chemical reaction type gas generating material is selected from carbon; the decomposition reaction type gas generating material includes carbonate, metal nitride and / or alkaline earth metal hydroxide.