Method for preparing vanadium carbide powder through gas-based reduction and vanadium carbide

Abstract

The invention relates to the technical field of powder metallurgy, and discloses a method for preparing vanadium carbide powder through gas-based reduction, which comprises the following steps: uniformly paving a vanadium source at the bottom of a quartz boat and placing the quartz boat in a heating furnace; carbon reaction gas is introduced into the heating furnace, and after air in the furnace is discharged, the gas flow is adjusted to the gas flow required by reaction; the furnace temperature is increased to the reaction temperature in a segmented mode, and heat preservation is conducted continuously; heating is stopped after heat preservation is finished, reaction gas or inert gas is continuously introduced to serve as shielding gas to maintain oxygen partial pressure in the furnace, and the sample is cooled to 200 DEG C or below along with the furnace to obtain vanadium carbide powder. The high-purity vanadium carbide powder is prepared by selecting medium-temperature carbonaceous gas cracking and carburizing, the purity of the product prepared by the process route is high, the residual carbon content can be accurately controlled, the process flows of external carbon addition, ball pressing and the like in the traditional preparation method are avoided, the calcination temperature is effectively reduced, and the carburizing efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of powder metallurgy, and in particular to a method for preparing vanadium carbide powder by gas-based reduction and vanadium carbide prepared by the method. Background Art

[0002] Vanadium carbide is currently widely used in the field of alloy materials. Adding vanadium carbide to steel can refine the grains of steel and improve the strength, toughness and wear resistance of steel. It can also be used as a carbide cemented carbide additive to significantly improve the hardness, wear resistance and heat resistance of cemented carbide. At present, the main preparation method of vanadium carbide is to mix vanadium pentoxide or vanadium trioxide with carbon powder and directly carry out carburization reduction reaction at high temperature. The vanadium carbide product prepared by this method contains 2~5% residual carbon and 1~3% residual oxygen, which cannot achieve the production of high-purity vanadium carbide and cannot meet the addition standards of certain special alloys. At the same time, the traditional carbon thermal reduction process requires a higher calcination temperature and a higher carbon content, and the production cost is high. It also runs counter to the green and low-carbon production concept.

[0003] Currently, vanadium carbide is mixed with a solid carbon source and prepared through traditional processes such as pelletizing and calcining. This method has a high calcination temperature, and the use of a solid carbon source to prepare vanadium carbide has a high carbon-oxygen equilibrium limit, and it is impossible to accurately control the carbon and oxygen content in the product, resulting in a low product purity.

[0004] Therefore, there is a need in the prior art for improving the preparation method of vanadium carbide powder grinding. Summary of the invention

[0005] In view of this, the purpose of the embodiment of the present invention is to propose a method for preparing vanadium carbide powder by gas-based reduction, selecting medium-temperature carbonaceous gas cracking and carburizing to prepare high-purity vanadium carbide powder. This process route produces products with high purity and can accurately control the residual carbon content, avoiding the external carbon mixing, ball pressing and other process processes of the traditional preparation method, while effectively reducing the calcination temperature and improving the carburizing efficiency.

[0006] Based on the above purpose, an embodiment of the present invention provides a method for preparing vanadium carbide powder by gas-based reduction, comprising the following steps: S1 spreads the vanadium source evenly on the bottom of the quartz boat and places it in a heating furnace; S2 introduces carbonaceous reducing gas into the heating furnace, exhausts the air in the furnace and adjusts the gas flow rate to the gas flow required for the reaction; S3: raising the furnace temperature in stages to the reaction temperature and keeping it warm; After S4 insulation is completed, heating is stopped, and reaction gas or inert gas is continuously introduced as protective gas to maintain the oxygen partial pressure in the furnace. The sample is cooled to below 200° C. with the furnace to obtain vanadium carbide powder.

[0007] In some embodiments, in S1, the vanadium source includes at least one of ammonium metavanadate, ammonium polyvanadate, vanadium pentoxide, and vanadium trioxide.

[0008] In some embodiments, the amount of vanadium source added is 4-20 g.

[0009] In some embodiments, in S2, the carbonaceous reducing gas includes at least one of CH4, C2H6, and C3H8.

[0010] In some embodiments, in S2, the gas flow rate required for the reaction is 0.2-1 L / min.

[0011] In some embodiments, in S3, the staged temperature increase includes: The first heating stage: the temperature range of the first heating stage is 20~500℃, and the heating rate is 10℃ / min; The second heating stage has a temperature range of above 500°C and a heating rate of 5°C / min.

[0012] In some embodiments, in S3, the insulation temperature is 900-1050° C., and the insulation time is less than 3 hours.

[0013] In some embodiments, the heating furnace is one of a tubular furnace, a carbon tube furnace, a rotary kiln, and a push plate kiln.

[0014] In some embodiments, the inert gas is one of nitrogen and argon.

[0015] Another aspect of the present invention provides vanadium carbide prepared using the above method.

[0016] The present invention has at least the following beneficial technical effects: The invention simplifies the existing vanadium carbide preparation process, reduces the optimal calcination temperature for vanadium carbide preparation, solves the technical problems of high carbon-oxygen balance limit and high residual carbon content in products of traditional solid carbonaceous reducing agents, and provides a method for preparing vanadium carbide by medium-temperature gas-based reduction. The method utilizes the cracking reaction of carbonaceous reducing gas at 800°C to 1100°C, utilizes highly active newly cracked carbon atoms for high-speed carburizing, and adjusts the equilibrium state of the cracking rate of the reaction gas and the carburizing reaction rate by adjusting experimental conditions such as the reaction gas flow rate, gas partial pressure, insulation temperature and insulation time, thereby adjusting the residual carbon and residual oxygen content in the reaction product, thereby realizing the one-step preparation of high-purity vanadium carbide powder. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other embodiments can be obtained based on these drawings without paying creative work.

[0018] Figure 1 The present invention provides a flow chart of an embodiment of a method for preparing vanadium carbide powder by gas-based reduction. DETAILED DESCRIPTION

[0019] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the embodiments of the present invention are further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0020] The terms "including" and "having" and any variations thereof in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions; the terms "first", "second", etc. in the specification and claims of the present invention or the above-mentioned drawings are used to distinguish different objects rather than to describe a specific order. "Multiple" means two or more, unless otherwise clearly and specifically defined.

[0021] In addition, reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0022] The invention simplifies the existing vanadium carbide preparation process, reduces the optimal calcination temperature for vanadium carbide preparation, solves the technical problems of high carbon-oxygen balance limit and high residual carbon content in products of traditional solid carbonaceous reducing agents, and provides a method for preparing vanadium carbide by medium-temperature gas-based reduction. The method utilizes the cracking reaction of carbonaceous reducing gas at 800°C to 1100°C, utilizes highly active newly cracked carbon atoms for high-speed carburizing, and adjusts the equilibrium state of the cracking rate of the reaction gas and the carburizing reaction rate by adjusting experimental conditions such as the reaction gas flow rate, gas partial pressure, insulation temperature and insulation time, thereby adjusting the residual carbon and residual oxygen content in the reaction product, thereby realizing the one-step preparation of high-purity vanadium carbide powder.

[0023] like Figure 1 As shown, the method for preparing vanadium carbide powder by gas-based reduction according to the present invention comprises the following steps: S1 spreads the vanadium source evenly on the bottom of the quartz boat and places it in a heating furnace; S2 introduces carbonaceous reaction gas into the heating furnace, exhausts the air in the furnace and adjusts the gas flow rate to the gas flow required for the reaction; S3: raising the furnace temperature in stages to the reaction temperature and keeping it warm; After S4 insulation is completed, heating is stopped, and reaction gas or inert gas is continuously introduced as protective gas to maintain the oxygen partial pressure in the furnace. The sample is cooled to below 200° C. with the furnace to obtain vanadium carbide powder.

[0024] Further, the vanadium source used in the raw material includes but is not limited to at least one of ammonium metavanadate, ammonium polyvanadate, vanadium pentoxide, vanadium trioxide, etc. In a preferred embodiment, ammonium polyvanadate is used as the vanadium source, and ammonium polyvanadate is a compound with a high vanadium content. This means that when preparing vanadium carbide, a unit mass of ammonium polyvanadate can provide more vanadium elements, so that a higher vanadium carbide yield can be obtained in theory. Ammonium polyvanadate has good thermal stability within a certain temperature range. In the initial stage of heating, it can maintain its chemical structure and will not decompose or react prematurely. This thermal stability helps to accurately control the starting temperature of the reaction, and provides a guarantee for the subsequent reduction reaction to generate vanadium carbide in a suitable temperature range. For example, during the heating process in a tubular furnace, it can remain stable before reaching a specific reaction temperature, and when the temperature is raised to the temperature required for the reduction reaction, it reacts with a reducing agent, etc.

[0025] Furthermore, the reaction gas used includes but is not limited to at least one of carbonaceous reducing gases such as CH4, C2H6, and C3H8. Preferably, methane is used as a reducing gas. Methane undergoes a cracking reaction at high temperature (800°C-1100°C). The carbon atoms produced by this cracking reaction are highly active, and these newly formed carbon atoms can react with the vanadium source. The carbon atoms produced by the cracking of methane are highly active because these carbon atoms have just been cracked from the molecules and are in a high energy state, and they are more likely to react with the vanadium source. This high activity enables the carburizing process to proceed quickly, which is conducive to the generation of vanadium carbide in a shorter time and improves the reaction efficiency. For example, compared to the use of a solid carbon source, the carbon atoms produced by the cracking of methane can be more evenly distributed in the reaction system and have more sufficient contact with the vanadium source, thereby achieving high-speed carburizing and increasing the generation rate of vanadium carbide.

[0026] Furthermore, the weight of the added vanadium source in the experiment was 4-20 g, and the reaction gas flow rate was 0.2-1 L / min. The variation of the reaction gas flow rate caused by different calcination scales was within the scope of patent protection.

[0027] Furthermore, the temperature rise system of the tubular furnace used in the experiment is 10°C / min from 20 to 500°C, and 5°C / min above 500°C.

[0028] Furthermore, the experiment adopted a holding temperature of 900~1050℃ and a holding time of less than 3h. The changes in holding temperature and holding time caused by different calcination scales are all within the scope of patent protection.

[0029] Further, the heating furnace is one of a tubular furnace, a carbon tube furnace, a rotary kiln, and a push plate kiln. In a preferred embodiment, a tubular furnace is used for heating, and the tubular furnace is equipped with an advanced temperature control system that can accurately set and maintain the desired reaction temperature, which is crucial for the preparation of vanadium carbide. During the reduction process, accurate temperature control helps to ensure that the reaction proceeds according to a predetermined thermodynamic and kinetic path, thereby improving the purity and crystallinity of the product and reducing the generation of impurity phases. The tubular furnace can be conveniently connected to various gas supply systems to achieve accurate control of the atmosphere in the furnace. When preparing vanadium carbide, reaction gases can be introduced according to the needs of the reaction, or inert gases can be introduced as a protective atmosphere to prevent the vanadium source and the product from being oxidized at high temperatures. By accurately controlling the type, flow rate, and pressure of the atmosphere, the reaction conditions can be optimized to improve the efficiency and selectivity of the reduction reaction.

[0030] Furthermore, the inert gas is one of nitrogen and argon. In a preferred embodiment, nitrogen is used as a protective gas. The nitrogen molecule is formed by two nitrogen atoms bonded by a triple bond (N≡N). This chemical bond is very stable, so that nitrogen has a high chemical stability. In the preparation process of vanadium carbide, nitrogen will not chemically react with the vanadium source, the vanadium carbide product, and other substances that may be involved in the reaction process (such as a carbon source, etc.), thereby effectively preventing the occurrence of oxidation reactions. For example, in a high temperature environment, many metals and their compounds are easily oxidized with oxygen, and the presence of nitrogen can well isolate oxygen, ensuring that the reaction is carried out in an oxygen-free or low-oxygen environment.

[0031] The present invention will be further explained below in conjunction with specific embodiments.

[0032] Example 1 4 g of ammonium polyvanadate was loaded into the quartz boat as a reactant, the flow rate of reaction gas CH4 was 0.2 L / min, the heating system of the tubular furnace was 20-500 °C with a heating rate of 10 °C / min, 500 °C-900 °C at 5 °C / min, and the holding time at 900 °C was 3 h.

[0033] Implementation effect: According to the above test conditions, heating was stopped after the insulation was completed, and the reaction gas was continued to be introduced as a protective gas to maintain the oxygen partial pressure in the furnace, and the sample was cooled to below 200°C with the furnace. The obtained vanadium carbide content was 89.8%, O content was 9.2%, and free carbon content was 0.5%.

[0034] Example 2 8 g of ammonium polyvanadate was loaded into the quartz boat as a reactant, the flow rate of reaction gas CH4 was 0.4 L / min, the heating system of the tubular furnace was 20-500 °C with a heating rate of 10 °C / min, 500 °C-1000 °C at 5 °C / min, and the holding time at 1000 °C was 3 h.

[0035] Implementation effect: According to the above test conditions, after the insulation is completed, the heating is stopped, and the reaction gas is continued to be introduced as a protective gas to maintain the oxygen partial pressure in the furnace, and the sample is cooled to below 200°C with the furnace. The obtained vanadium carbide content is 92.3%, the O content is 0.2%, and the free carbon content is 7%.

[0036] Example 3 12 g of ammonium polyvanadate was loaded into the quartz boat as a reactant, the flow rate of reaction gas CH4 was 0.6 L / min, the heating system of the tubular furnace was 20-500 °C with a heating rate of 10 °C / min, 500 °C-1050 °C at 5 °C / min, and the holding time at 1050 °C was 2 h.

[0037] Implementation effect: According to the above test conditions, after the insulation is completed, the heating is stopped, and the reaction gas is continued to be introduced as a protective gas to maintain the oxygen partial pressure in the furnace, and the sample is cooled to below 200°C with the furnace. The obtained vanadium carbide content is 96.1%, the O content is 0.2%, and the free carbon content is 3.2%.

[0038] Example 4 20 g of ammonium polyvanadate was loaded into the quartz boat as a reactant, the flow rate of reaction gas CH4 was 1 L / min, the heating system of the tubular furnace was 20-500 °C at a heating rate of 10 °C / min, 500 °C-1050 °C at 5 °C / min, and the holding time at 1050 °C was 1 h.

[0039] Implementation effect: According to the above test conditions, heating was stopped after the insulation was completed, and the reaction gas was continued to be introduced as a protective gas to maintain the oxygen partial pressure in the furnace, and the sample was cooled to below 200°C with the furnace. The obtained vanadium carbide content was 98.2%, O content was 0.3%, and free carbon content was 1.1%.

[0040] Example 5 12 g of ammonium polyvanadate was loaded into the quartz boat as a reactant, the flow rate of reaction gas CH4 was 0.4 L / min, the heating system of the tubular furnace was 20-500 °C with a heating rate of 10 °C / min, 500 °C-1050 °C with a heating rate of 5 °C / min, and the holding time at 1050 °C was 0 h.

[0041] Implementation effect: According to the above test conditions, after the insulation is completed, the heating is stopped, and the reaction gas is continuously introduced as the protective gas to maintain the oxygen partial pressure in the furnace, and the sample is cooled to below 200°C with the furnace. The obtained vanadium carbide content is 97.5%, the O content is 2%, and the free carbon content is 0.2%.

[0042] The invention aims to solve the problems of high material cost, high calcination energy consumption and low product purity in the traditional carbon thermal reduction preparation of vanadium carbide. The invention changes the selection of traditional solid carbon source and the calcination process route of ball pressing, and selects medium-temperature CH4 cracking and carburizing to prepare high-purity vanadium carbide powder. The product prepared by this process route has high purity and can accurately control the residual carbon content. It avoids the external carbon mixing, ball pressing and other process processes of the traditional preparation method, and at the same time effectively reduces the calcination temperature and improves the carburizing efficiency. It has great advantages in reducing production costs and reducing carbon emissions.

[0043] The above are exemplary embodiments disclosed in the present invention, but it should be noted that various changes and modifications may be made without departing from the scope disclosed in the embodiments of the present invention as defined in the claims. The functions, steps and / or actions of the method claims according to the disclosed embodiments described herein do not need to be performed in any particular order. In addition, although the elements disclosed in the embodiments of the present invention may be described or required in individual form, they may also be understood as multiple unless explicitly limited to the singular.

[0044] It should be understood that, as used herein, the singular forms "a", "an" are intended to include the plural forms as well, unless the context clearly supports an exception. It should also be understood that, as used herein, "and / or" refers to any and all possible combinations including one or more of the associated listed items.

[0045] The serial numbers of the embodiments disclosed in the above embodiments of the present invention are only for description and do not represent the advantages or disadvantages of the embodiments.

[0046] A person skilled in the art should understand that the discussion of any of the above embodiments is only exemplary and is not intended to imply that the scope of the disclosure of the embodiments of the present invention (including the claims) is limited to these examples; under the concept of the embodiments of the present invention, the technical features in the above embodiments or different embodiments can also be combined, and there are many other changes in different aspects of the above embodiments of the present invention, which are not provided in detail for the sake of simplicity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present invention should be included in the protection scope of the embodiments of the present invention.

Claims

1. A method for preparing vanadium carbide powder by gas-based reduction, characterized in that: include: S1 spreads the vanadium source evenly on the bottom of the quartz boat and places it in a heating furnace; S2 introduces carbonaceous reducing gas into the heating furnace, exhausts the air in the furnace and adjusts the gas flow rate to the gas flow rate required for the reaction; S3: raising the furnace temperature in stages to the reaction temperature and keeping it warm; After S4 insulation is completed, heating is stopped, and reaction gas or inert gas is continuously introduced as protective gas to maintain the oxygen partial pressure in the furnace. The sample is cooled to below 200° C. with the furnace to obtain vanadium carbide powder.

2. The method for preparing vanadium carbide powder by gas-based reduction according to claim 1, characterized in that: In S1, the vanadium source includes at least one of ammonium metavanadate, ammonium polyvanadate, vanadium pentoxide, and vanadium trioxide.

3. The method for preparing vanadium carbide powder by gas-based reduction according to claim 2, characterized in that: The added amount of the vanadium source is 4-20g.

4. The method for preparing vanadium carbide powder by gas-based reduction according to claim 1, characterized in that: In S2, the carbonaceous reducing gas includes at least one of CH4, C2H6, and C3H8.

5. The method for preparing vanadium carbide powder by gas-based reduction according to claim 1, characterized in that: In S2, the gas flow rate required for the reaction is 0.2~1L / min.

6. The method for preparing vanadium carbide powder by gas-based reduction according to claim 1, characterized in that: In S3, the stepwise heating includes: The first heating stage, wherein the temperature range of the first heating stage is 20-500°C, and the heating rate is 10°C / min; The second heating stage: the temperature range of the second heating stage is above 500° C., and the heating rate is 5° C. / min.

7. The method for preparing vanadium carbide powder by gas-based reduction according to claim 1, characterized in that: In S3, the insulation temperature is 900-1050° C., and the insulation time is less than 3 hours.

8. The method for preparing vanadium carbide powder by gas-based reduction according to claim 1, characterized in that: The heating furnace is one of a tubular furnace, a carbon tube furnace, a rotary furnace and a push plate kiln.

9. The method for preparing vanadium carbide powder by gas-based reduction according to claim 1, characterized in that: The inert gas is one of nitrogen and argon.

10. A vanadium carbide, characterized in that: Prepared by the method according to any one of claims 1 to 9.

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