A vanadium-containing polycrystalline alloy material, its preparation method, and its application in steel.

Abstract

This invention discloses a vanadium-containing polycrystalline alloy material, its preparation method, and its application in steel. The vanadium-containing polycrystalline alloy material is prepared from one or more untreated or pretreated V-containing slag materials as raw materials. In the vanadium-containing polycrystalline alloy, vanadium exists in the form of elemental vanadium, solid-solution vanadium, and vanadium compounds. The vanadium compounds include one or more of V₂O₅, V₂O₃, VN, V₂N, VC, V₂C, V₃Si, V₅Si₃, VSi₂, vanadium-titanium compounds, and vanadium-iron compounds. The solid-solution vanadium is a solid solution of vanadium in titanium / iron.

Description

Technical Field

[0001] This invention belongs to the field of nitride alloy technology, specifically relating to the field of novel high-temperature alloy technology of nitride alloys, and more specifically, relating to a vanadium-containing polycrystalline alloy material, its preparation method and its application in steel. Background Technology

[0002] Nitriding alloys are widely used in steelmaking. To improve the strength of steel, precious metal alloys such as ferrovanadium or ferroniobium are added during the steelmaking process through microalloying. To fully utilize the microalloying strengthening effect of vanadium and niobium, an appropriate amount of nitriding alloy is generally added during steelmaking. This forms strong carbonitrides with the microalloying elements niobium and vanadium, enhancing the precipitation strengthening and precipitation strengthening effects of the microalloying elements. Therefore, precious metal alloys are widely used in steelmaking.

[0003] Following the report in patent document US3579328A of the process for producing ferrovanadium from vanadium-containing slag through direct reduction, several related technologies have been disclosed in the prior art: 1) For example, patent document CN113416882A discloses a method for producing polycrystalline vanadium alloys using waste-rich materials. Vanadium slag and coke powder are mixed evenly, and a portion of it is used as a base and laid in an electric arc furnace equipped with an electric reactor for arc ignition and melting. Preliminary smelting: After the arc ignition is completed, the remaining vanadium slag and coke powder mixture is added for preliminary smelting.

[0004] 2) Patent document CN102912158A discloses a method for smelting ferrovanadium using vanadium concentrate slag. Scrap steel, vanadium pentoxide, vanadium concentrate slag, aluminum powder, and silicon powder are uniformly mixed and fed into an electric arc furnace. Smelting is carried out using an external furnace method. After ignition and reaction, ferrovanadium and slag are generated. During the reduction phase, an electric arc furnace method is used. Vanadium pentoxide and lime are uniformly mixed and fed into the electric arc furnace to melt the materials into a molten state. Ferrosilicon and ferrosilicon-aluminum slag are added to reduce the vanadium content. When the vanadium content in the slag reaches below 0.35%, the slag is removed. Vanadium pentoxide and lime are then fed into the electric arc furnace for refining. Samples are taken for analysis. After passing the refining process, the ferrovanadium is cast using a steel ladle to obtain ferrovanadium.

[0005] 3) Patent document CN104726715A discloses a method for the resource utilization of vanadium-chromium waste slag. The process steps are as follows: the vanadium-chromium waste slag is dried and dehydrated at 300-450℃ and pressed into pellets under a pressure of 20-22 MPa, i.e., green pellets; the green pellets, reducing agent and calcium oxide are added to the alloy furnace in three stages. Before adding the first stage material, the green pellets are first laid at the bottom of the electric arc furnace; after the power is turned on, the first stage mixed raw materials are added. After complete melting, the reducing agent is added for reduction. After smelting the lean slag, the second and third stage materials are added in sequence and reduced to obtain vanadium-chromium-iron alloy.

[0006] 4) Patent document JP2001098339A describes loading one or two of the following raw materials into a continuous cyclone smelting furnace: vanadium-containing waste and vanadium ore, heating, melting, and reducing them, and then separating them from the metal and vanadium-containing slag; thereafter, the vanadium-containing slag is loaded into a reactor along with a reducing agent to reduce the vanadium-containing slag. Summary of the Invention

[0007] The problem to be solved To address the problems in the prior art, one of the objectives of this invention is to provide a vanadium-containing polycrystalline alloy material that has better performance in steel applications.

[0008] The second objective of this invention is to provide a method for preparing vanadium-containing polycrystalline alloy materials, which employs a gas-solid reaction, resulting in a high vanadium yield, full utilization of beneficial elements, and environmental friendliness during the production process; and can simultaneously complete the reduction and nitriding of vanadium-containing polycrystalline alloys.

[0009] The third objective of this invention is to provide an application of vanadium-containing polycrystalline alloy materials or vanadium-containing polycrystalline alloy materials obtained by a preparation method in steel, wherein the steel includes, but is not limited to, HRB500(E) high-strength earthquake-resistant steel, HRB400(E) steel, Q620D steel, high-chromium cast iron, high-strength strip steel, non-quenched and tempered steel, high-strength H-beam steel, high-speed tool steel, high-strength pipeline steel and HRB600(E) rebar.

[0010] Technical solution To solve the above problems, the technical solution adopted by the present invention is as follows: The first aspect of this invention provides a vanadium-containing polycrystalline alloy material, prepared from one or more untreated or pretreated V-containing slag materials as raw materials. In the vanadium-containing polycrystalline alloy, vanadium exists in the form of elemental vanadium, vanadium in solid solution, and vanadium compounds. The vanadium compounds include one or more of V2O5, VO, V2O3, VN, V2N, VC, V2C, V3Si, V5Si3, VSi2, vanadium-titanium compounds, and vanadium-iron compounds. The solid-solution vanadium is vanadium atoms dissolved in the matrix metal lattice to form a substitutional / interstitial solid solution, such as a solid solution of vanadium in titanium / iron.

[0011] When the reducing agent added during the manufacturing process is Al, the vanadium compound also includes VAl3, VAl6, VAl8, and VAl. 11 One or more of them.

[0012] The above-mentioned vanadium compounds shall be tested using the following standards and methods:

[0013] The aforementioned solid-solution vanadium refers to vanadium atoms that do not exist as independent elemental phases, nor do they form vanadium compounds (such as V₂O₅, V₂O₃, VN, V₂N, VC, V₂C, V₃Si, V₅Si₃, VSi₂, VAl₃, VAl₆, VAl₈, VAl₈). 11 Vanadium is not dissolved in the alloy matrix lattice in atomic form (e.g., substitutional solid solution) or interstitial positions (interstitial solid solution) to form a single-phase solid solution.

[0014] .

[0016] It should be noted that untreated or pretreated vanadium-containing slag typically refers to vanadium slag produced from vanadium-titanium magnetite smelting (blast furnace / converter) or tailings discarded after vanadium ore beneficiation. It is used directly as raw material or material to be treated without undergoing pretreatment steps such as grinding, roasting, pre-leaching, or impurity removal. Vanadium mainly exists as a vanadium-chromium spinel solid solution, tightly encapsulated by silicates and iron oxides; it contains impurities such as metallic iron, free SiO2, calcium, magnesium, and aluminum. Therefore, the purpose of pretreatment is: 1) to break the vanadium-chromium spinel solid solution encapsulation and release vanadium-containing minerals; 2) to oxidize the insoluble trivalent vanadium to soluble pentavalent vanadium.

[0017] However, this invention uses V-containing slag material that has not undergone pretreatment (only grinding, without roasting, pre-leaching, or impurity removal) or has undergone pretreatment (roasting, pre-leaching, or impurity removal) but has only undergone grinding, and then heats it to 1300°C or higher. This causes partial phase decomposition, vanadium valence reduction, and lattice activation in the raw material, directly destroying its low electrical conductivity structure at low temperatures. On the one hand, the high temperature above 1300°C will destroy the stable structure of vanadates, triggering a thermal decomposition reaction; on the other hand, common reducing components in the slag material, such as Fe²⁺, will be removed. + Elements such as C and Si, which come from smelting residues or raw material impurities, can undergo reduction reactions with high-valence vanadium, causing the valence state of vanadium to drop from +5 or +4 to +3 or +2, or even to some elemental metallic vanadium.

[0018] The crystalline states of vanadium compounds in the aforementioned vanadium-containing polycrystalline alloys are as follows: .

[0020] Compared to this invention, monocrystalline vanadium exhibits good plasticity at room temperature but low strength, and is prone to low-temperature brittleness due to hindered dislocation movement. In contrast, this invention introduces a second or more crystalline states into its polycrystalline form, achieving performance optimization through the hindering effect of multiphase interfaces and coordinated deformation, resulting in superior performance in steel applications. 1) Interfaces between different crystal states act as obstacles to dislocation movement. Dislocations require more energy to pass through the interface, following the extension effect of the Hall-Page relation, thus significantly improving the yield strength and hardness of the alloy. The bcc-V (Ti) solid solution crystal phase formed by introducing Ti into vanadium-titanium alloys creates a slight grain boundary difference with the matrix bcc-V, and its room temperature tensile strength can be increased by 30%-50% compared to pure vanadium.

[0021] 2) If the second crystal phase is a fine, dispersed soft phase, it can coordinate the stress concentration of the matrix through its own deformation when under stress, and avoid brittle fracture caused by stress concentration. In polycrystalline vanadium-chromium alloy, the dispersed crystal phase formed by Cr can effectively suppress the cleavage brittleness of pure vanadium at low temperature, so that the alloy can still maintain a good elongation at -50℃. The elongation of pure vanadium at this temperature is less than 5%, while the polycrystalline alloy can maintain more than 15%.

[0022] 3) In monocrystalline polycrystalline vanadium, the grain boundaries are prone to impurity segregation, such as O and N, forming brittle phases, such as V2O5, which leads to intergranular cracking. In contrast, in a multiphase structure, the second crystalline phase can adsorb some impurities or form a low-energy interface through grain boundary structure reconstruction, reducing impurity segregation and improving the alloy's resistance to intergranular corrosion cracking.

[0023] According to any embodiment of the first aspect of the present invention, the apparent composition of the vanadium-containing polycrystalline alloy, calculated by mass fraction, is: 0.5%≤V≤50%, 0<N≤36%, 0.5%≤Si≤58%, 0<Ti≤19%, 0<RE≤17%, 0<Al≤17%, with the remainder being Fe and C.

[0024] The above-mentioned components: silicon (0.5%≤Si≤58%) can effectively optimize the alloy lattice structure, refine the grains, and homogenize the internal structure, which can narrow the alloy melting temperature range and stabilize the overall melting point; titanium (0<Ti≤19%), rare earth (0<RE≤17%), and aluminum (0<Al≤17%), as modifying elements, can purify the internal impurities of the alloy, eliminate lattice defects, improve the overall thermal stability of the alloy, and suppress crystal structure distortion at high temperatures; vanadium, nitrogen, carbon and iron matrix form a stable multi-element alloy system, and the proportion of each element is in a relatively optimal balance range, which mutually counterbalance and offset the thermal performance fluctuations caused by a single element.

[0025] According to any embodiment of the first aspect of the present invention, the untreated or pretreated V-containing slag material refers to V-containing compounds and V-containing mixture slag materials, the V-containing mixture slag material including vanadium slag.

[0026] The second aspect of this invention provides a method for preparing a vanadium-containing polycrystalline alloy material, comprising the following steps: Step S1: Crushing, fine grinding, and screening of vanadium-containing slag material that has not been pretreated or has been pretreated; under the raw material composition of the present invention, a binder and a reducing agent in a certain proportion of the total mass fraction of fine vanadium-containing slag powder can be added. The reducing agent can be a carbonaceous material (such as graphite powder), aluminum powder, or metallic silicon powder.

[0027] For example, untreated or pretreated V-containing slag materials, such as vanadium-titanium magnetite smelting slag and vanadium extraction slag from coal shale, are mixed evenly with carbonaceous materials (such as graphite powder), aluminum powder, or metallic silicon powder in a certain proportion to ensure that vanadium oxides are in full contact with carbonaceous materials (such as graphite powder), aluminum powder, or metallic silicon powder; if the untreated or pretreated V-containing slag materials have a large particle size, they need to be pre-crushed to below 200 mesh to improve reaction efficiency; Step S2: After processing the V-containing slag material, whether untreated or pretreated, dry it to remove volatile matter; the drying temperature is 120-400℃, and the holding time is 2-4 hours. The volatile matter removal rate is required to be ≥98% to avoid residual moisture affecting the reduction nitriding reaction.

[0028] Step S3: High-temperature reduction and nitriding under inert gas protection; the equipment used for high-temperature reduction is a high-temperature electric heating furnace, and inert gas is introduced into the furnace cavity; 1) Specific type of inert gas, preferably Ar, purity ≥99.9%, flow control range 0.5-2m³ / h; 2) High-temperature reduction and nitriding: First, heat to 900-1000℃ and hold for 3-4 hours, then heat to 1150-1200℃ and hold for 9-10 hours, then continue to heat to 1300-1350℃ and hold for 6-8 hours, until the temperature reaches 1450-1700℃ and is held for 10-12 hours.

[0029] By combining XRD and SEM to detect the presence of at least two target crystalline states, and by chemical analysis to detect the content of elements such as V and N, non-conforming products can be reprocessed by adjusting parameters such as temperature and holding time to ensure product quality stability.

[0030] Step S4: The final product is in the form of blocks or granules of different particle sizes.

[0031] The third aspect of the present invention provides an application of the vanadium-containing polycrystalline alloy material described in the first aspect, the application including the application of the vanadium-containing polycrystalline alloy material to the following steel grades: HRB400(E), HRB500(E), HRB600(E) threaded steel bars and wires, high-strength profile steel, high-strength pipeline steel, high-strength corrosion-resistant steel, high-strength cast steel and cast iron, etc.

[0032] In the aforementioned materials, vanadium nitride compounds such as VN and V2N do not exist independently, but are deeply integrated with vanadium-silicon, vanadium-titanium, and vanadium-iron composite compounds and solid solutions. Nitrogen atoms are confined within the alloy lattice and solid solution structure, increasing the decomposition activation energy of the nitride alloy, effectively reducing the high-temperature decomposition rate, and preventing the instantaneous generation of large amounts of nitrogen gas. Simultaneously, titanium, aluminum, and rare earth elements in the system possess excellent nitrogen-fixing and deoxidation capabilities, preferentially capturing free nitrogen and oxygen atoms generated during alloy decomposition to form stable inert compounds such as titanium nitrides and rare earth nitrides, further suppressing the precipitation of free nitrogen gas. The stabilizing coating effect of the iron-carbon matrix also buffers the high-temperature impact of molten steel, reducing the degree of thermal decomposition of the nitride alloy.

[0033] Beneficial effects Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The vanadium-containing polycrystalline alloy material of the present invention introduces a second or more crystal states into the polycrystalline state, which can achieve performance optimization through the hindering effect of the multiphase interface and coordinated deformation, making its application effect in steel better; (2) The vanadium-containing polycrystalline alloy material of the present invention is prepared from untreated or pretreated V-containing slag as raw material. Its composition is complex, containing elemental V, compound V and various vanadium nitrides, carbides, silicides, aluminides, titanides and ferrites, etc. The apparent composition calculated by mass fraction makes the vanadium alloy have a variety of performance characteristics. The nitrogen, carbon and other elements can affect the hardness, strength and wear resistance of the alloy by forming corresponding compounds; the silicon, titanium and other elements can improve the high temperature performance and oxidation resistance of the alloy by solid solution strengthening or forming specific intermetallic compounds. (3) The application of the vanadium-containing polycrystalline alloy material of the present invention in high-strength steel: In the process of steel smelting, the vanadium alloy of the present invention is precisely added to the molten steel, which improves the absorption rate of the vanadium alloy, thereby achieving precise control of the composition and properties of the steel. Therefore, the present invention can refine the grains by adjusting the vanadium content in the steel, improve the strength and toughness of the steel, or use vanadium carbides and nitrides to improve the wear resistance and corrosion resistance of the steel. Attached Figure Description

[0034] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. However, it should be understood that these drawings are designed for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, unless specifically indicated, these drawings are intended only to conceptually illustrate the structural construction described herein and are not necessarily drawn to scale.

[0035] Figure 1 This is a product diagram of the vanadium-containing polycrystalline alloy material of the present invention. Detailed Implementation

[0036] This disclosure will be more readily understood through reference to the following description, taken in conjunction with the accompanying drawings and examples, all of which form part of this disclosure. It should be understood that this disclosure is not limited to the specific products, methods, conditions, or parameters described and / or illustrated herein. Furthermore, the terminology used herein is for the purpose of describing particular embodiments by way of example only and is not intended to be limiting, unless otherwise stated.

[0037] It should also be understood that, for clarity, certain features of this disclosure can be described herein in the context of individual embodiments, but can also be provided in combination with each other in individual embodiments. That is, unless obviously incompatible or specifically excluded, each individual embodiment is considered to be able to be combined with any other embodiment, and such combination is considered to represent another different embodiment. Conversely, for the sake of brevity, various features of this disclosure described in the context of individual embodiments can also be provided individually or in any sub-combination. Finally, while a particular embodiment can be described as part of a series of steps or part of a more general structure, each step or substructure can also be considered an independent embodiment in itself.

[0038] Unless otherwise stated, it should be understood that each individual element in the list and each combination of individual elements in the list will be interpreted as a different embodiment. For example, a list of embodiments denoted as "A, B, or C" should be interpreted as including embodiments "A", "B", "C", "A or B", "A or C", "B or C", or "A, B, or C".

[0039] In this disclosure, the singular forms of the articles “a,” “one,” and “the” also include the corresponding plural references, and references to a particular value include at least that particular value, unless the context clearly indicates otherwise. Thus, for example, a reference to “substance” is a reference to at least one of such substance and its equivalents.

[0040] Ordinal terms such as "first" and "second" can be used to explain various components or fluids, but these components and fluids are not limited by these terms. Therefore, without departing from the teachings of this disclosure, these terms are used only to distinguish one component / fluid from another.

[0041] When an item is described using the combined terms “...and / or ...", the description should be understood to include any one of the listed items and all combinations thereof.

[0042] Generally, the use of the term "about" indicates an approximation that can vary depending on the desired characteristics obtained through the disclosed subject matter, and will be interpreted in a context-dependent manner based on function. Therefore, those skilled in the art can interpret a degree of difference on a case-by-case basis. In some cases, the number of significant figures used when expressing a particular value can be a representative technique for determining the difference allowed by the term "about." In other cases, a range of values ​​can be used to determine the range of differences allowed by the term "about." Furthermore, all ranges in this disclosure are inclusive and combinable, and references to values ​​described within a range include every value within that range.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terms used herein and / or include any and all combinations of one or more of the associated listed items.

[0044] The present invention will be further illustrated below with reference to specific embodiments, but these embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field. The essential features and significant effects of the present invention can be seen from the following embodiments. The described embodiments are some, but not all, embodiments of the present invention, and therefore do not limit the present invention in any way. Any non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are within the protection scope of the present invention.

[0045] Existing vanadium alloy production equipment (such as the devices mentioned in patents CN103105060A and CN101603132A) has stringent requirements for raw materials, mainly relying on high-purity raw materials (such as vanadium pentoxide). However, untreated or pretreated vanadium-containing slag (vanadium-containing steel slag, vanadium slag, ore dressing slag, etc.) has a complex composition, containing a large amount of non-conductive substances (such as silicates and calcium oxides), and vanadium exists in high valence states (+5, +4) dispersed in multiple phases. Existing equipment cannot directly adapt to such low-purity, high-impurity slag raw materials. At the same time, the small amount of conductive substances in untreated or pretreated vanadium-containing slag are trapped by non-conductive components, making it difficult for current to be transmitted and failing to meet the conditions for reduction nitriding reaction. Therefore, the resource utilization of untreated or pretreated vanadium-containing slag requires multi-step pretreatment, which is cumbersome and costly.

[0046] Vanadium-containing polycrystalline alloy materials The vanadium-containing polycrystalline alloy material of the present invention is prepared from one or more untreated or pretreated V-containing slag materials as raw materials. In the vanadium-containing polycrystalline alloy, vanadium exists in the form of elemental vanadium, solid-solution vanadium, and vanadium compounds, including V₂O₅, V₀, V₂O₃, VN, V₂N, VC, V₂C, V₃Si, V₅Si₃, VSi₂, VAl₃, VAl₆, VAl₈, and VAl. 11 One or more of vanadium-titanium compounds and vanadium-iron compounds; the solid-solution vanadium is vanadium atoms dissolved in the matrix metal lattice, forming a substitutional / interstitial solid solution, such as a solid solution of vanadium in titanium / iron. The above-mentioned vanadium compounds are tested using the following standards and methods:

[0047] XRD (macroscopic phase characterization) + SEM (microscopic morphology observation) is preferred. For abnormal areas found by XRD / SEM, TEM (micro-region phase structure) + EBSD (grain orientation) is used to clarify the crystallographic characteristics and orientation differences of local crystal states, thereby obtaining different crystal states of V in vanadium-containing polycrystalline alloys.

[0048] The crystalline states of vanadium compounds in the aforementioned vanadium-containing polycrystalline alloys are as follows:

[0049] It should be noted that all 16 types of crystalline V mentioned above can be formed using the methods described below, such as VC+VFe solid solution, VN+VSi2, etc.

[0050] Compared with the present invention, monocrystalline vanadium has good plasticity at room temperature but low strength, and is prone to low-temperature brittleness due to obstructed dislocation movement at low temperatures; while the present invention introduces a second or more crystalline states into the polycrystalline form, which can achieve performance optimization through the hindering effect of multiphase interfaces and coordinated deformation, making it more effective in steel applications.

[0051] 1) The interface between different crystal states will become an obstacle to the movement of dislocations. Dislocations need to consume more energy to pass through the interface. According to the extension effect following the Hall-Page relation, the yield strength and hardness of the alloy are significantly improved. The bcc-V (Ti) solid solution crystal phase formed by introducing Ti element into vanadium-titanium alloy forms a small grain boundary difference with the matrix bcc-V, and its room temperature tensile strength can be increased by 30%-50% compared with pure vanadium.

[0052] 2) If the second crystal phase is a fine, dispersed soft phase, it can coordinate the stress concentration of the matrix through its own deformation when under stress, and avoid brittle fracture caused by stress concentration. In polycrystalline vanadium-chromium alloys, the dispersed crystal phase formed by Cr can effectively suppress the cleavage brittleness of pure vanadium at low temperature, so that the alloy can still maintain a good elongation at -50℃. The elongation of polycrystalline alloys can be maintained at more than 15%.

[0053] 3) In monocrystalline polycrystalline vanadium, the grain boundaries are prone to intergranular cracking due to impurity segregation, such as O forming brittle phases like V2O5. In contrast, in multiphase structures, the second crystalline phase can adsorb some impurities or form low-energy interfaces through grain boundary structure reconstruction to reduce impurity segregation and improve the alloy's resistance to intergranular corrosion cracking.

[0054] Preparation methods for vanadium-containing polycrystalline alloy materials V-containing slag materials, whether untreated or pretreated, mainly include vanadium-containing steel slag and vanadium slag, with complex and diverse compositions, as shown in the following two materials: 1) Vanadium-containing steel slag: mainly composed of 3CaO SiO2, 2CaO Fe2O3, 2CaO The composition includes SiO2, FeO phase, and free CaO. Vanadium exists in a dispersed state in all phases, mainly in tricalcium silicate and calcium ferrite, with pentavalent vanadium accounting for more than 80%. 2) Vanadium slag: Generally, this refers to the enriched slag formed by selectively oxidizing vanadium in vanadium-titanium magnetite molten iron obtained through blast furnace or electric arc furnace smelting, and then refining it by blowing. Its main phases are vanadium-bearing spinel, silicate phase, and magnetite. The main stable phase is spinel containing Fe, V, Ti, Cr, and Mn, while the vein phase is quartz. Chemically, it contains 10%–25% V₂O₅, 15%–22% SiO₂, 0.7%–3.0% CaO, 3%–10% MgO, 2.6%–20.0% MnO, 0.02%–0.12% P, and 26%–40% TFe.

[0055] The preparation method of the vanadium-containing polycrystalline alloy material of the present invention comprises the following steps: Step S1: Crush, grind, and screen the above-mentioned untreated or pretreated V-containing slag material; For example, untreated or pretreated vanadium-titanium magnetite smelting slag, vanadium extraction slag from coal shale, etc., containing vanadium oxides should be mixed evenly with carbonaceous materials (such as graphite powder) or aluminum powder in a certain proportion to ensure that vanadium oxides are in full contact with carbonaceous materials (such as graphite powder) or aluminum powder; if the untreated or pretreated vanadium oxide slag containing vanadium oxides has a large particle size, it needs to be crushed to below 200 mesh in advance to improve the reaction efficiency. Step S2: After processing, the V-containing slag material, whether untreated or pretreated, is dried and volatile matter is removed; Step S3: High-temperature reduction and nitriding under inert gas protection; the equipment used for high-temperature reduction is a high-temperature electric heating furnace, and inert gas is introduced into the furnace cavity; Step S4: The product is obtained in block or granular form with different particle sizes.

[0056] The applications include the use of the vanadium-containing polycrystalline alloy material in steel grades such as HRB400(E), HRB500(E), and HRB600(E) threaded steel bars and wires, high-strength profile steel, high-strength pipeline steel, high-strength corrosion-resistant steel, high-strength cast steel, and cast iron.

[0057] The preparation method described above in this invention has the following characteristics: (1) The material reacts directly in the gas-solid phase in the high-temperature furnace. It is in a non-molten state and will not produce waste such as slag or high-temperature harmful dust. This avoids the loss of beneficial elements by being carried away by the slag and also avoids pollution to the environment. (2) Through the adjustment and control of the high-temperature reduction process, the beneficial elements in the material, such as V, Si, Ti, Al, etc., are basically all reduced to form vanadium-containing polycrystalline alloys combined with V. (3) Elements such as V, Si, and Al can cooperate with the nitriding process during high-temperature reduction to form nitrides and carbonitrides. These substances can enable vanadium-containing polycrystalline alloys to fully exert their effects in steel applications.

[0058] The untreated or pretreated V-containing slag refers to V-containing compounds and V-containing mixtures of slag, including vanadium slag. Wherein: Vanadium (V): As a matrix element, its content is 0.5%≤V≤50%. Elemental V and solid solution V are the basic components of alloys and have an important influence on the basic properties of alloys such as strength and hardness.

[0059] Nitrogen (N): With a content of 0 < N ≤ 36%, it can form compounds such as VN and V₂N, which strengthen the alloy and improve its hardness and strength. However, excessive content can lead to a decrease in the alloy's toughness. When vanadium alloys are mainly composed of silicon-vanadium alloys or elemental vanadium, the N content is relatively low.

[0060] Silicon (Si): content 0.5% < Si ≤ 58%, can form silicides such as V3Si, V5Si3, VSi2, which can improve the high temperature strength and hardness of the alloy and improve the oxidation resistance of the alloy.

[0061] Titanium (Ti): content 0 < Ti ≤ 19%, forms VTi solid solution with vanadium. Ti can improve the resistance of vanadium alloys to liquid metal corrosion and neutron irradiation damage, and can also improve the strength of the alloy through solid solution strengthening.

[0062] Rare earth elements (RE): content 0 < RE ≤ 17%. Rare earth elements can capture dissolved oxygen in the vanadium alloy matrix to form rare earth oxides, thereby effectively reducing coarse titanium-rich strip-shaped second phases, refining grains, improving microstructure, and enhancing the alloy's radiation resistance.

[0063] Iron (Fe) and carbon (C): The remainder is Fe and C. Fe is an important component of the alloy and plays a role in regulating the alloy's density and strength. C can form carbides such as VC and V2C, which can improve the alloy's hardness, wear resistance and strength.

[0064] In the material of this invention, vanadium is not in a single elemental form, but exists in three forms: elemental vanadium, vanadium in solid solution, and vanadium compounds. These encompass multiple phases, including V₂O₅, V₂O₃, VN, V₂N, VC, V₂C, vanadium-silicon, vanadium-titanium, and vanadium-iron compounds. The solid-solution vanadium is a stable solid solution of vanadium with titanium and iron. This multi-phase structure is the core of the material's stable chemical properties. Compared to traditional single-phase vanadium nitride and vanadium carbide alloys, which exhibit extremely high activity in high-temperature molten steel environments and are prone to instantaneous decomposition and oxidation reactions, leading to rapid component loss and imbalance, this material exhibits superior properties.

[0065] The composite vanadium phases of the material of this invention form a stable system with complementary properties: elemental vanadium provides core alloying properties, while solid-solution vanadium, relying on the binding effect of titanium and iron lattices, effectively reduces the free activity of vanadium atoms; various vanadium oxides, nitrides, carbides, silicides, and composite metal compounds all have crystal structures with excellent high-temperature stability. The phases mutually restrict and balance each other, avoiding violent reactions of a single phase; at the same time, the synergy of multiple phases can effectively fix key elements such as nitrogen, carbon, silicon, and titanium in the material, preventing the overall composition ratio imbalance caused by the escape of a single element, and further enhancing the overall stability of the composition.

[0066] Example 1 The preparation method of the vanadium-containing polycrystalline alloy material in this embodiment includes the following steps: Step S1: Select vanadium-containing slag material that is either untreated or pretreated, wherein the V content is 30%, the Si content is 12%, the N content is 38%, the Ti content is 2%, the RE content is 8%, and the remainder is Fe and C; Step S2: Crush the material selected in step S1, then grind it to a particle size of 120-600 mesh; dry at 400℃ for 2 hours to ensure a volatile matter removal rate of 98% and avoid residual moisture affecting the reduction nitriding reaction; Step S3: Add 2% by mass of polyborosiloxane and 12% by mass of graphite carbon reducing agent to the total vanadium-containing slag fine powder, mix well and press into blocks using a high-pressure briquetting machine at a pressure of 120 MPa; Step S4: Place the compressed block obtained in step S3 into a pretreatment furnace and heat it to 680°C. Then, fill the furnace with a protective gas (argon-nitrogen mixture, where Ar is 99% pure and N2 is 98% pure) and pretreatment for 5 hours. Step S5: Place the pretreated briquette into a nitriding furnace for reduction nitriding treatment; during the nitriding treatment, nitrogen gas is introduced at a pressure of 0.2 MPa, the temperature is first raised to 1000℃ and held for 3 hours, then raised to 1200℃ and held for 9 hours, then raised to 1350℃ and held for 8 hours, until it is heated to 1700℃ and held for 12 hours. Step S6: After the reduction nitriding treatment is completed, the furnace is allowed to cool naturally to below 300℃, and then removed from the furnace and cooled to room temperature to obtain a vanadium-containing polycrystalline alloy with a particle size of 3-70mm. Figure 1 As shown.

[0067] The results included the detection of crystalline vanadium in vanadium-containing polycrystalline alloys:

[0068] This vanadium-containing polycrystalline alloy was used in a converter with a nominal capacity of 120 tons, producing HRB400(E) steel. During the steel refining process, an argon-nitrogen mixture was blown into the molten steel for 5 minutes at a flow rate of 7.1 m³ / s. 3 During the nitriding process, an oxygen / nitrogen meter (HORIBAEMGA-820) was used to measure the nitrogen content, which was found to be 0.021% by mass. This indicates that the melting rate of the vanadium-containing polycrystalline alloy reached over 95%, the decomposition rate was reduced, and the alloy yield was effectively improved.

[0069] Example 2 It is basically the same as Example 1, except that 8% aluminum powder is added as a reducing agent.

[0070] The results included the detection of crystalline vanadium in vanadium-containing polycrystalline alloys: In this test, the crystalline vanadium in the vanadium-containing polycrystalline alloys included:

Claims

1. A vanadium-containing polycrystalline alloy material, characterized in that, The vanadium-containing polycrystalline alloy is prepared from one or more untreated or pretreated vanadium-containing slag materials. In the vanadium-containing polycrystalline alloy, vanadium exists in the form of elemental vanadium, solid-solution vanadium, and vanadium compounds. The vanadium compounds include one or more of V2O5, VO, V2O3, VN, V2N, VC, V2C, V3Si, V5Si3, VSi2, vanadium-titanium compounds, and vanadium-iron compounds. The solid-solution vanadium is a solid solution of vanadium in titanium / iron.

2. The vanadium-containing polycrystalline alloy material according to claim 1, characterized in that, The apparent composition of the vanadium-containing polycrystalline alloy, calculated by mass fraction, is: 0.5%≤V≤50%, 0<N≤36%, 0.5%≤Si≤58%, 0<Ti≤19%, 0<RE≤17%, 0<Al≤17%, with the remainder being Fe and C.

3. The vanadium-containing polycrystalline alloy material according to claim 1, characterized in that, When the reducing agent is Al, the vanadium compound also includes VAl3, VAl6, VAl8, and VAl 11 One or more of them.

4. The vanadium-containing polycrystalline alloy material according to claim 1 or 2, characterized in that, The untreated or pretreated V-containing slag material refers to V-containing compounds and V-containing mixture slag materials, including vanadium slag.

5. A method for preparing a vanadium-containing polycrystalline alloy material as described in claim 1 or 2, characterized in that, The steps are as follows: Step S1: Crushing, fine grinding, and screening of V-containing slag materials, whether pretreated or untreated; Step S2: After processing the V-containing slag material (whether pretreated or untreated), dry it to remove volatile matter; Step S3: High-temperature reduction and nitriding under inert gas protection; the equipment used for high-temperature reduction is a high-temperature electric heating furnace, and inert gas is introduced into the furnace cavity; Step S4: The product is obtained in block or powder form.

6. An application of the vanadium-containing polycrystalline alloy material as described in any one of claims 1-4, characterized in that, The applications include the vanadium-containing polycrystalline alloy material mainly used in the following steel grades: HRB400(E), HRB500(E), HRB600(E) threaded steel bars and wires, high-strength profile steel, high-strength pipeline steel, high-strength corrosion-resistant steel, high-strength cast steel and cast iron.

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