CN105063398A - Technique for preparing high-nitrogen vanadium-nitrogen alloy - Google Patents

Abstract

The invention relates to a technique for preparing a high-nitrogen vanadium-nitrogen alloy, belonging to the technical field of metallurgy. The technique uses a self-propagating high-temperature synthesis process and comprises the following steps: by using coarse ammonium metavanadate as a raw material, mixing with a retardant, directly introducing hydrogen, and accelerating nitridation by using NH4<+> in NH4VO3 to implement nitriding at high temperature; and after the reaction is complete, cooling the high-nitrogen vanadium-nitrogen alloy in the graphite crucible by introducing nitrogen, taking out, and crushing into blocks. An exhaust valve is utilized to control synthesis pressure in the closed synthesis container so as to control the surface air cleft on the final product vanadium-nitrogen alloy; and thus, the product prepared by the combustion synthesis technique has high strength, is almost not crushed in the material transportation and use process, thereby lowering the attrition rate of the material. The synthetic product has the advantages of high compactness, high specific gravity (up to 6.5 g/cm<3>) and uniform nitrogen content distribution.

Description

A kind of technology of preparing high nitrogen vanadium nitrogen alloy

technical field

The invention relates to a process for preparing a high-nitrogen vanadium-nitrogen alloy, which belongs to the technical field of metallurgy.

Background technique

my country is the world's largest steel producer and also the world's largest steel consumer. However, low-carbon structural steel is the most used steel, accounting for about 70% of the steel usage. Therefore, improving the strength of ordinary carbon steel is an important direction to promote the technological progress of my country's steel industry and adjust the steel structure. The solution is to increase alloyed steel - add high nitrogen vanadium nitrogen alloy. Using vanadium-nitrogen alloying, no need to add other precious alloy elements, high-strength steel with a yield strength of 550-600Mpa can be obtained under general hot rolling conditions, so long products such as high-strength steel bars and steel plates (strips) , thick plate, thick-walled section steel, seamless steel pipe, CSP and other products have been widely used in the development.

In 1998, the US Strategic Minerals Corporation carried out the development of vanadium-nitrogen alloying technology and the promotion and application of its patented product vanadium-nitrogen alloy in my country's iron and steel industry. Some domestic steel mills carried out application tests in the production of HRB400 grade steel bars. Domestic research units and Some large steel mills have conducted a lot of research on the effect of adding vanadium-nitrogen alloys on the mechanical properties of steel and the strengthening mechanism. Better performance, more stable HRB400MpaIII grade threaded steel bar and V-N steel can be produced, and at the same time, 30-40% of vanadium can be saved, which greatly reduces the cost of steel. The United States claims that the United States is the only country that can commercially produce vanadium-nitrogen alloys, but this technology is not disclosed. Domestic enterprises have been able to mass-produce vanadium-nitrogen alloys after research and testing, but the current output of vanadium-nitrogen alloy products in my country cannot meet the needs of domestic production of high-strength steel bars and other steel products. Since 2003, we have used self-propagating high-temperature synthesis technology to develop and produce ferro-vanadium nitride, and have successfully applied it to the production of V-N steel in some large domestic steel plants.

Self-propagating high-temperature synthesis technology was discovered by the Institute of Chemical Physics of the former Soviet Academy of Sciences in 1967 when researching rocket solid fuels. The synthesis principle is to use a very small amount of energy provided by the outside to induce high heat release between heterogeneous substances in powder or powder compacts. Chemical reaction to form the combustion wave at the front of the reaction, and the subsequent synthesis reaction induces the continuous chemical reaction of adjacent materials with the support of self-exothermic self-sustained combustion until all the materials are reacted to synthesize the compound material with the required composition and structure. The advantages of self-propagating high-temperature synthesis technology are energy saving (the synthesis process does not require additional energy), high efficiency (the synthesis speed is extremely fast), environmental protection (no pollutants are discharged during the synthesis process), and high quality (stable composition and high purity). Self-propagating high-temperature synthesis technology is a high-tech in the current synthesis field. In the late 1980s, many units in our country carried out research in this area.

Self-propagating high-temperature synthesis does not require an external heat source during the synthesis process, so the focus of thermodynamic calculations is to discuss the possibility of its reaction, which is the basis for discussing the self-propagating high-temperature synthesis process, and the adiabatic combustion temperature of the synthesis reaction directly calculated according to the thermodynamic formula (Tad) is an important parameter to characterize combustion synthesis, which is of great significance to the theoretical research and application of self-propagating high-temperature synthesis. The most reliable method to predict the possibility of self-propagating high-temperature synthesis process is to calculate the adiabatic combustion temperature of a given mixed system, which is a qualitative basis for judging whether the combustion synthesis reaction can be self-sustaining. Merzhanov, the founder of the self-propagating high-temperature synthesis process, proposed some general empirical criteria ["Combustion Synthesis" 1999: P.56]: only when Tad>1800K, the self-propagating high-temperature synthesis reaction can be self-sustained. For the nitriding of vanadium metal or vanadium alloy raw materials, the adiabatic combustion temperature is mainly calculated through the reaction of vanadium and nitrogen. The adiabatic combustion temperature of the synthesis reaction of vanadium nitrogen compounds is 3500K. Put forward the requirement of Tad>1800K experience value. For example, on September 08, 2010, the Chinese Invention Patent Application Publication No. CN101824556A disclosed a method for producing ferrovanadium nitride using a self-propagating high-temperature synthesis process. The raw materials are ferrovanadium and nitrogen. Crushing, dry the crushed ferrovanadium raw materials and put them in bulk in a crucible, place the crucible in a high-pressure synthesizer and fill it with 6-12MPa nitrogen, start the ignition device to ignite the raw materials to carry out the synthesis reaction, and the combustion synthesis reaction is self-sustaining Carried out, the ferrovanadium nitride synthesized by combustion was taken out after being cooled in nitrogen, and broken into pieces. However, the nitrogen content in the synthetic product is only 9.0-17.0%, and there are problems such as low nitrogen content (≤17%) and high content of impurities such as carbon, sulfur and silicon, which seriously affect the nitrogen addition and performance of steel. Compared with ordinary low-nitrogen vanadium-nitrogen alloys, vanadium-nitrogen alloys with nitrogen content (≥17%) can more effectively promote the improvement of steel strength, toughness, ductility, fatigue resistance and other properties, and further reduce the use of vanadium to save costs. Reducing impurities such as carbon, sulfur and silicon in the vanadium-nitrogen alloy can reduce the excessive external impurities brought in when the vanadium-nitrogen alloy is added in steelmaking, which will affect the performance of the steel.

Contents of the invention

The technical problem to be solved by the present invention is to propose a process for preparing high-nitrogen vanadium-nitrogen alloys, using coarse-grade ammonium metavanadate directly as raw materials for vanadium-nitrogen alloys instead of using high-priced vanadium products such as ferrovanadium as raw materials, and utilizing self-propagating low-temperature The combustion reaction itself releases heat for nitriding, the reaction time is short, energy consumption and cost are low, and the nitrogen vanadium alloy produced has high nitrogen and high purity, and the nitrogen content is ≥ 17%. Nitrogen content is better than American VN alloy.

According to the requirements proposed in the present invention, the technical scheme adopted in the present invention is:

1. A process for preparing high-nitrogen vanadium-nitrogen alloys, using self-propagating high-temperature synthesis technology, using coarse-grade ammonium metavanadate as raw material, mixing moderator, directly passing hydrogen, and promoting nitrogen by NH ₄ ⁺ in NH ₄ VO ₃ Combined, nitriding at high temperature; the specific steps are: before the reaction, fully mix the coarse-grade ammonium metavanadate and the moderator; put them into graphite crucibles one by one, and these graphite crucibles are stacked into airtight synthesis containers In the process, hydrogen gas is introduced from the bottom of the graphite crucible in the lowest layer; the ignition device is started to ignite the raw materials to carry out the synthesis reaction, and the high-nitrogen vanadium-nitrogen alloy is combusted; the mixed gas of water vapor and carbon monoxide is discharged from the top of the airtight synthesis container through the exhaust valve; When the vanadium nitriding reaction temperature reaches 1500°C-1520°C; adjust and control the exhaust valve so that the gas pressure in the airtight synthesis container is 2-3Mpa, and the combustion synthesis reaction is self-sustaining; After cooling with nitrogen gas, take it out and break it into pieces.

The moderator of the present invention is added in order to prevent the nitriding reaction from being too violent as the temperature increases.

The moderator is graphite powder, and its addition is 3%-5% of the total weight of the coarse-grade ammonium metavanadate.

Innovation point and beneficial effect of the present invention are:

The present invention provides a new option for the production of high-nitrogen vanadium-nitrogen alloys. The present invention directly utilizes coarse-grade ammonium metavanadate as a raw material, passes through hydrogen directly, and promotes nitrogenation by NH ₄ ⁺ in NH ₄ VO ₃ . Nitriding at high temperature; the present invention utilizes an exhaust valve to control the synthesis pressure in the airtight synthesis container to be 2-3Mpa, and the discharge of _H2O and CO in the vanadium-nitrogen alloy is limited during the synthesis process, which becomes slow and not continuous Air gaps are formed by gushing out from the same position on the surface of the vanadium-nitrogen alloy body, so the surface cracks of the final product of the vanadium-nitrogen alloy of the present invention are less, and its surface quality is improved, thereby improving its product quality.

Compared with the CN101824556A technique, the inventive method has the following advantages:

1. In the present invention, coarse-grade NH ₄ VO ₃ is directly used as raw material for vanadium-nitrogen alloy instead of high-priced vanadium products such as V ₂ O ₅ as raw material, and the source of raw material is easier to obtain; both NH ₄ ⁺ in NH ₄ VO ₃ can be used to promote Nitrogenation, and save a lot of cost;

2. In the synthesis process of the present invention, except for the moderator (graphite powder), no other reducing or heating materials are added, which can greatly reduce the impurities in the product, and there is no discharge of three wastes, and the product quality is high;

3. The present invention utilizes the self-propagating low-temperature combustion reaction to release heat itself to realize sufficient reaction of vanadium and nitrogen, thereby realizing high nitrogen content of the alloy and ensuring uniform and stable product quality. Moreover, the whole reaction synthesis process does not need electric heating and heat preservation, which saves energy and procedures, is easy to control, and is convenient for equipment processing and installation. Using the new technology of self-propagating low-temperature combustion can also make the synthesis cycle less than 50 minutes, which is much shorter than the reaction time of the existing technology, greatly improving production efficiency;

4. The present invention adopts an exhaust valve to control the synthesis pressure in the airtight synthesis container to control the surface air gap of the final product vanadium-nitrogen alloy; to make the product prepared by the combustion synthesis process stronger, and there is almost no breakage during material transportation and use, thereby Reduced material loss rate;

5. Combustion synthesis technology is adopted, no briquetting is required for either the initial synthesis charge or the final product. The synthetic product is compact, with a large specificity, up to 6.5g/cm ³ , and the nitrogen content is evenly distributed. The high-nitrogen vanadium-nitrogen alloy composition of this product is: vanadium-nitrogen alloy containing V ≥ 78%, vanadium-nitrogen alloy containing N ≥ 17%, Vanadium nitrogen alloy C content ≤ 5%, vanadium nitrogen alloy S content ≤ 0.1%, vanadium nitrogen alloy silicon content ≤ 0.1%.

Detailed ways

A kind of technique for preparing high-nitrogen vanadium-nitrogen alloy of the present invention:

A process for preparing high-nitrogen vanadium-nitrogen alloy, using self-propagating high-temperature synthesis technology, using coarse-grade ammonium metavanadate as raw material, mixing moderator, directly passing hydrogen, and promoting nitrogen combination by NH ₄ ⁺ in NH ₄ VO ₃ , Nitriding at high temperature;

2NH ₄ VO ₃ +H ₂ +C=2VN+5H ₂ O+CO;

The present invention is a solid-gas reaction, which belongs to the type of "permeation combustion synthesis". Osmotic combustion synthesis is a process in which hydrogen infiltrates into NH ₄ VO ₃ to undergo exothermic chemical transformation and structural transformation with nitrogen atoms. According to the current combustion synthesis process of NH ₄ VO ₃ , the nitrogen atoms contained in NH ₄ VO ₃ are sufficient to maintain the needs of the vanadium nitriding reaction. In order to prevent the nitriding reaction from being too violent with the increase of temperature; the present invention adds graphite powder moderator in NH VO _{3 ;}

The graphite powder added in the present invention acts as a deceleration, and its addition is 3%-5% of the gross weight of the coarse-grade ammonium metavanadate; it is fully mixed before the reaction; it is packed into graphite crucibles one by one, and these graphite crucibles are placed in a stacked state. In the airtight synthesis container, hydrogen gas is introduced from the bottom of the graphite crucible on the lowermost layer; the ignition device is started to ignite the raw materials to carry out the synthesis reaction, and the high-nitrogen vanadium nitrogen alloy is combusted; H ₂ O and CO pass through the exhaust valve from the top of the airtight synthesis container Discharge; when the vanadium nitriding reaction temperature reaches 1500°C-1520°C; adjust and control the exhaust valve so that the gas pressure in the airtight synthesis container is 2-3Mpa, and the combustion synthesis reaction will continue; after the reaction is complete, the high-nitrogen vanadium-nitrogen alloy is in Cool the graphite crucible with nitrogen gas, take it out, and break it into pieces.

As mentioned above, the present invention provides a process for preparing high-nitrogen vanadium-nitrogen alloys, and an application for a patent for invention is now filed according to law; however, the above description is one of the preferred embodiments of the present invention, and is not intended to limit the present invention. Therefore, all those that are similar to or identical to the features of the present invention should fall within the scope of the patent application of the present invention.

Claims (2)

1. A process for preparing high-nitrogen vanadium-nitrogen alloys, utilizing self-propagating high-temperature synthesis technology, is characterized in that it is raw material with coarse-grade ammonium metavanadate, mixed moderator, directly leading hydrogen, by NH ₄ VO ₃ in NH ₄ ⁺ Promote nitrogen combination, nitriding at high temperature; the specific steps are: before the reaction, first mix the coarse-grade ammonium metavanadate and the moderator fully; put them into graphite crucibles one by one, and put these graphite crucibles in a stacked state In the airtight synthesis container, hydrogen gas is introduced from the bottom of the graphite crucible on the lowermost layer; the ignition device is started to ignite the raw materials to carry out the synthesis reaction, and the high nitrogen vanadium nitrogen alloy is combusted; the mixed gas of water vapor and carbon monoxide is exhausted from the top of the airtight synthesis container Valve discharge; when the vanadium nitriding reaction temperature reaches 1500°C-1520°C; adjust and control the exhaust valve so that the gas pressure in the airtight synthesis container is 2-3Mpa, and the combustion synthesis reaction is self-sustaining; after the reaction is complete, the high-nitrogen vanadium-nitrogen alloy After cooling with nitrogen gas in a graphite crucible, take it out and break it into pieces. 2. a kind of technique for preparing high nitrogen vanadium nitrogen alloy according to claim 1 is characterized in that: described moderator is graphite powder, and its add-on is the 3%-5% of coarse grade ammonium metavanadate gross weight %.