Decarburization method of vanadium-nitrogen alloy

Abstract

The invention provides a decarburization method of a vanadium-nitrogen alloy, which comprises the following steps of: a) reacting the vanadium-nitrogen alloy, an oxygen-containing vanadium source and ammonia gas to remove carbon in the vanadium-nitrogen alloy; according to the method, the oxygen-containing vanadium source is adopted to conduct decarburization treatment on the vanadium-nitrogen alloy in the ammonia gas environment, carbon in an intermediate product vanadium carbide which is not completely reacted in the vanadium-nitrogen alloy and elemental carbon which does not participate in the reaction are oxidized, the oxygen-containing vanadium source is adopted as an oxidizing agent, the oxygen adding amount is controllable, and the risk that the VN content is reduced due to excessive oxidation is avoided; and meanwhile, under the combined action of ammonia gas, the oxygen-containing vanadium source oxidizes carbon into CO to be discharged, and the carbon content of the vanadium-nitrogen alloy is reduced. Experimental results show that the method provided by the invention can reduce the carbon content in the vanadium-nitrogen alloy to 5% or below.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of alloy materials, and particularly relates to a decarburization method of vanadium-nitrogen alloy. BACKGROUND

[0002] The carbothermal reduction nitridation method is one of the most commonly used methods for preparing vanadium-nitrogen alloy (VN), and in the preparation process, vanadium oxide (for example, V2O3 or V2O5) is fully mixed with carbon powder and other additives, and then reacts with nitrogen at high temperature. In the reaction process, the transformation path of the vanadium existing form is: V2O3→VC→VN or V2O5→V2O3→VC→VN. Since carbon powder needs to be added in the preparation process, and the VC intermediate state is involved in the reaction process, if the addition amount of carbon powder or the process parameters in the reaction process are not properly controlled, the carbon content in the vanadium-nitrogen alloy will be too high. The high carbon content in the vanadium-nitrogen alloy will lead to the decrease of the physical properties of the alloy, such as the decrease of hardness, toughness and ductility. In addition, if the vanadium-nitrogen alloy is used in the steelmaking process, the high carbon content in the vanadium-nitrogen alloy will lead to the decrease of the compatibility of the vanadium-nitrogen alloy with the steel, affect the strengthening effect of the vanadium-nitrogen alloy in the production of the steel, and lead to the decrease of the mechanical properties of the steel. SUMMARY

[0003] Therefore, the present application provides a decarburization method of vanadium-nitrogen alloy, which can effectively remove the carbon in the vanadium-nitrogen alloy without introducing other impurities.

[0004] The vanadium-nitrogen alloy includes two parts of carbon, one part is elemental carbon which does not participate in the reaction, and the other part is carbon in VC which is not converted into VN. Directly oxidizing the vanadium-nitrogen alloy with oxygen can remove the elemental carbon therein, but if the amount of oxygen is not properly controlled, the VN is easily oxidized into vanadium oxide. Continuing to introduce nitrogen to nitride the vanadium-nitrogen alloy can remove the carbon in VC, but the reaction route of VC and nitrogen is: 2VC+N2=2VN+2C, which generates elemental carbon and cannot completely remove the carbon in the vanadium-nitrogen alloy.

[0005] Based on this, the present application provides a decarburization method of vanadium-nitrogen alloy, which includes the following steps:

[0006] a) reacting the vanadium-nitrogen alloy, an oxygen-containing vanadium source and ammonia to remove the carbon in the vanadium-nitrogen alloy.

[0007] In some specific implementation manners, the reaction temperature is 1100℃-1300℃.

[0008] In some specific implementation manners, the molar ratio of vanadium in the oxygen-containing vanadium source to carbon in the vanadium-nitrogen alloy is 2-4:3.

[0009] In some specific implementation manners, the oxygen-containing vanadium source is selected from one or more of vanadium trioxide, vanadium pentoxide, ammonium metavanadate and ammonium polyvanadate.

[0010] In some specific implementations, the vanadium oxide source is vanadium trioxide.

[0011] In some specific implementations, the vanadium-nitrogen alloy is in powder form.

[0012] In some specific implementations, the carbon content in the vanadium-nitrogen alloy is 5wt% to 15wt%.

[0013] In some specific implementations, the step a) specifically comprises:

[0014] a1) mixing the vanadium-nitrogen alloy and the vanadium oxide source uniformly and placing them in a heating furnace;

[0015] a2) after the heating furnace is purged of the original gas by introducing ammonia gas, the temperature is raised to perform the reaction and remove the carbon in the vanadium-nitrogen alloy.

[0016] In some specific implementations, after the reaction is completed, ammonia gas is continuously introduced until the heating furnace is cooled.

[0017] In some specific implementations, the reaction time is 1h to 4h.

[0018] The present application uses a vanadium oxide source to perform decarburization treatment on a vanadium-nitrogen alloy in an ammonia gas environment, oxidizes the carbon in the intermediate product vanadium carbide that has not completely reacted and the elemental carbon that has not participated in the reaction in the vanadium-nitrogen alloy, uses a vanadium oxide source as an oxidizing agent, the oxygen addition amount is controllable, and the risk of VN content reduction caused by excessive oxidation is avoided; at the same time, under the joint action of ammonia gas, the vanadium oxide source oxidizes carbon to CO and discharges it, reducing the carbon content of the vanadium-nitrogen alloy. Experimental results show that the method provided by the present application can reduce the carbon content in the vanadium-nitrogen alloy to below 5%. DETAILED DESCRIPTION

[0019] It should be understood that the expression "one or more of something" includes each of the objects of the recited expression separately as well as various combinations of two or more of the recited objects, unless otherwise understood from the context and usage. The expression "and / or" in combination with three or more recited objects should be understood to have the same meaning, unless otherwise understood from the context.

[0020] The term "comprising" or "containing", including the use of its grammatical synonyms, should be generally understood to be open-ended and non-limiting, for example, not excluding other non-recited elements or steps, unless otherwise specifically stated or understood from the context.

[0021] It should be understood that the order of steps or the order of performing certain actions is not important as long as the present application remains operable. In addition, two or more steps or actions can be performed simultaneously.

[0022] The use of any and all instances or exemplary language such as “e.g.” or “including” in this document is merely intended to better illustrate the invention and is not intended to limit the scope of the invention unless the claims are made. No language in this specification should be construed as indicating that any unclaimed element is essential to the practice of the invention.

[0023] Furthermore, the numerical ranges and parameters used to define the present invention are approximate values, and the relevant values ​​in the specific embodiments have been presented as precisely as possible. However, any value inevitably contains standard deviations due to individual test methods. Therefore, unless explicitly stated otherwise, it should be understood that all ranges, quantities, values, and percentages used in this disclosure are modified with the word "approximately." Here, "approximately" generally means an actual value within plus or minus 10%, 5%, 1%, or 0.5% of a particular value or range.

[0024] This invention provides a method for decarburizing vanadium-nitrogen alloys, comprising the following steps:

[0025] a) React vanadium-nitrogen alloy, oxygen-containing vanadium source and ammonia to remove carbon from vanadium-nitrogen alloy.

[0026] Specifically, the present invention performs decarbonization treatment according to the following method:

[0027] Step a1) After the vanadium-nitrogen alloy and the oxygen-containing vanadium source are mixed evenly, they are placed in a heating furnace;

[0028] Step a2) After ammonia gas is introduced into the heating furnace to purge the original gas in the heating furnace, the temperature is raised to carry out the reaction and remove carbon from the vanadium-nitrogen alloy.

[0029] This invention first involves uniformly mixing a vanadium-nitrogen alloy and an oxygen-containing vanadium source. In some specific implementations, the vanadium-nitrogen alloy is a carbon-containing vanadium-nitrogen alloy powder. In some specific implementations, the particle size of the vanadium-nitrogen alloy powder is ≤75μm, preferably ≤70μm, and more preferably ≤65μm. In some specific implementations, the carbon content in the vanadium-nitrogen alloy is 5wt% to 15wt%, preferably 6wt% to 13wt%. In some specific implementations, the oxygen-containing vanadium source contains oxygen or oxygen-containing nitrogen, including but not limited to vanadium trioxide, vanadium pentoxide, ammonium metavanadate, and ammonium polyvanadate, and may be one or more of these. In some specific implementations, the oxygen-containing vanadium source is preferably vanadium trioxide.

[0030] In some specific implementations, the molar ratio of vanadium in the oxygen-containing vanadium source to carbon in the vanadium-nitrogen alloy is 2–4:3, preferably 2.5–3.5:3. Ideally, the entire oxygen-containing vanadium source participates in decarburization, at which point the molar ratio of vanadium in the oxygen-containing vanadium source to carbon in the vanadium-nitrogen alloy (hereinafter referred to as the vanadium-carbon ratio) n(V):n(C) = 2:3. However, in the actual reaction process, some V₂O₃ reacts directly with NH₃ to form the vanadium-nitrogen alloy: V₂O₃ + 2NH₃ = 2VN + 3H₂O. Therefore, it is necessary to appropriately increase the amount of oxygen-containing vanadium source, for example, by increasing the vanadium-carbon ratio n(V):n(C) to 4:3. Since the reaction V₂O₃ + 3C + 2NH₃ = 2VN + 3CO + 3H₂ is better than the direct reaction between V₂O₃ and NH₃, and only some V₂O₃ reacts with NH₃ to form VN, the amount of oxygen-containing vanadium source added should not be too high to prevent the final product from having an excessively high oxygen content. Meanwhile, V2O3 reacting with NH3 will generate VN, increasing VN production without causing vanadium loss.

[0031] In some specific implementations, a vanadium-nitrogen alloy and an oxygen-containing vanadium source are mixed evenly and placed in a heating furnace. Ammonia gas is then introduced into the furnace to purge the existing gases, and the temperature is raised to initiate a reaction, removing carbon from the vanadium-nitrogen alloy. During the reaction, VC reacts with ammonia: 2VC + NH3 = 2VN + 2C + 3H2, generating hydrogen gas that escapes. The generated elemental carbon has the same properties as the original elemental carbon. Since the mixture contains an oxygen-containing vanadium source, the elemental carbon participates in the reaction: V2O3 + 3C + 2NH3 = 2VN + 3CO + 3H2. Using ammonia for decarbonization is easier than the traditional carbothermic reaction involving nitrogen. During the reaction, elemental carbon is converted into carbon monoxide gas, which escapes, achieving the decarbonization purpose. In some specific implementations, the reaction temperature is 1100℃~1300℃, preferably 1150℃~1250℃; the reaction time is 1h~4h, preferably 1.5h~3.5h.

[0032] In some specific implementations, after the reaction is complete, ammonia gas is continued to be introduced into the heating furnace for cooling, resulting in a vanadium-nitrogen alloy with a low carbon content.

[0033] This invention employs an oxygen-containing vanadium source in an ammonia atmosphere to decarburize vanadium-nitrogen alloys. It oxidizes the unreacted carbon in the intermediate product vanadium carbide and the unreacted elemental carbon. Using an oxygen-containing vanadium source as the oxidant allows for controllable oxygen addition, avoiding the risk of VN content reduction due to over-oxidation. Simultaneously, under the combined action of ammonia, the oxygen-containing vanadium source oxidizes carbon to CO and discharges it, reducing the carbon content of the vanadium-nitrogen alloy. Experimental results show that the method provided by this invention can reduce the carbon content in vanadium-nitrogen alloys to below 5%.

[0034] The present invention is further illustrated below with reference to the embodiments. The scope of protection of the present invention is not limited to the following embodiments.

[0035] Example 1

[0036] Vanadium-nitrogen alloy powder with a particle size ≤75μm, prepared in the laboratory, was selected, with a carbon content of 8.2% and an oxygen content of 1.2%.

[0037] Take 10g of vanadium-nitrogen alloy powder. Weigh 3.4g of vanadium trioxide according to the molar ratio of vanadium in vanadium trioxide to carbon in the vanadium-nitrogen alloy powder n(V):n(C)=2:3. Mix the vanadium-nitrogen alloy powder and vanadium trioxide evenly and place them in a tube furnace. Continuously introduce ammonia gas into the tube furnace at a flow rate of 0.2L / min. After the original gas in the furnace is exhausted, start heating until the furnace reaches 1100℃. Hold at 1100℃ for 1 hour and then stop heating. Continue to introduce ammonia gas until the tube furnace cools down to obtain the vanadium-nitrogen alloy product with a carbon content of 2.2% and an oxygen content of 0.6%.

[0038] Example 2

[0039] Vanadium-nitrogen alloy powder with a particle size ≤75μm was selected, containing 12.5% ​​carbon and 1.4% oxygen.

[0040] Take 10g of vanadium-nitrogen alloy powder. Weigh 9.5g of vanadium pentoxide according to the molar ratio of vanadium in vanadium pentoxide to carbon in the vanadium-nitrogen alloy powder n(V):n(C)=1:1. Mix the vanadium-nitrogen alloy powder and vanadium pentoxide evenly and place them in a tube furnace. Continuously introduce ammonia gas into the tube furnace at a flow rate of 0.2L / min. After the original gas in the furnace is exhausted, start heating until the furnace reaches 1250℃. Hold at 1250℃ for 2 hours and then stop heating. Continue to introduce ammonia gas until the tube furnace cools down to obtain the vanadium-nitrogen alloy product with a carbon content of 3.5% and an oxygen content of 1.0%.

[0041] Example 3

[0042] Vanadium-nitrogen alloy powder with a particle size ≤75μm, a carbon content of 12.5%, and an oxygen content of 1.4% was selected.

[0043] Take 1 kg of vanadium-nitrogen alloy powder. Weigh 1.62 kg of ammonium metavanadate according to the molar ratio of vanadium in ammonium metavanadate to carbon in the vanadium-nitrogen alloy powder n(V):n(C) = 4:3. Mix the vanadium-nitrogen alloy powder and ammonium metavanadate evenly and place them in a rotary kiln. Continuously introduce ammonia gas into the rotary kiln at a flow rate of 10 L / min. After the original gas in the kiln is exhausted, start heating until the furnace reaches 1300℃. Hold at 1300℃ for 4 hours and then stop heating. Continue to introduce ammonia gas until the rotary kiln cools down to obtain the vanadium-nitrogen alloy product with a carbon content of 4.2% and an oxygen content of 1.2%.

[0044] Example 4

[0045] Vanadium-nitrogen alloy powder with a particle size ≤75μm, a carbon content of 6.6%, and an oxygen content of 1.0% was selected.

[0046] Take 100g of vanadium-nitrogen alloy powder. Weigh 55g of vanadium trioxide according to the molar ratio of vanadium in vanadium trioxide to carbon in the vanadium-nitrogen alloy powder n(V):n(C)=1:1. Mix the vanadium-nitrogen alloy powder and vanadium trioxide evenly and place them in a rotary kiln. Continuously introduce ammonia gas into the rotary kiln at a flow rate of 1L / min. After the original gas in the kiln is exhausted, start heating until the furnace reaches 1180℃. Hold at 1180℃ for 2 hours and then stop heating. Continue to introduce ammonia gas until the rotary kiln cools down to obtain the vanadium-nitrogen alloy product with a carbon content of 1.6% and an oxygen content of 0.4%.

[0047] Comparative Example 1

[0048] Vanadium-nitrogen alloy powder with a particle size ≤75μm, prepared in the laboratory, was selected, with a carbon content of 8.2% and an oxygen content of 1.2%.

[0049] Take 10g of vanadium-nitrogen alloy powder. Weigh 3.4g of vanadium trioxide according to the molar ratio of vanadium in vanadium trioxide to carbon in the vanadium-nitrogen alloy powder n(V):n(C)=2:3. Mix the vanadium-nitrogen alloy powder and vanadium trioxide evenly and place them in a tube furnace. Continuously introduce ammonia gas into the tube furnace. After the original gas in the furnace is exhausted, start heating until the furnace reaches 600℃. Hold at 600℃ for 1 hour and then stop heating. Continue to introduce ammonia gas until the tube furnace cools down to obtain the vanadium-nitrogen alloy product with a carbon content of 6.3% and an oxygen content of 4.5%.

[0050] Therefore, the method provided by this invention can effectively remove carbon from vanadium-nitrogen alloys and significantly reduce the carbon content.

[0051] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for decarburizing a vanadium-nitrogen alloy, comprising the following steps: a) React vanadium-nitrogen alloy, oxygen-containing vanadium source and ammonia to remove carbon from vanadium-nitrogen alloy.

2. The decarbonization method according to claim 1, characterized in that, The reaction temperature is 1100℃~1300℃.

3. The decarbonization method according to claim 1 or 2, characterized in that, The molar ratio of vanadium in the oxygen-containing vanadium source to carbon in the vanadium-nitrogen alloy is 2 to 4:

3.

4. The decarbonization method according to claim 3, characterized in that, The oxygen-containing vanadium source is selected from one or more of vanadium trioxide, vanadium pentoxide, ammonium metavanadate, and ammonium polyvanadate.

5. The decarbonization method according to claim 4, characterized in that, The oxygen-containing vanadium source is vanadium trioxide.

6. The decarbonization method according to claim 1 or 2, characterized in that, The vanadium-nitrogen alloy is in powder form.

7. The decarbonization method according to claim 6, characterized in that, The carbon content in the vanadium-nitrogen alloy is 5wt% to 15wt%.

8. The decarbonization method according to claim 1, characterized in that, Step a) specifically includes: Step a1) After the vanadium-nitrogen alloy and the oxygen-containing vanadium source are mixed evenly, they are placed in a heating furnace; Step a2) After ammonia gas is introduced into the heating furnace to purge the original gas in the heating furnace, the temperature is raised to carry out the reaction and remove carbon from the vanadium-nitrogen alloy.

9. The decarbonization method according to claim 8, characterized in that, After the reaction is complete, ammonia gas is continuously introduced into the heating furnace for cooling.

10. The decarbonization method according to claim 8, characterized in that, The reaction time is 1 hour to 4 hours.