CN113604696A - Method for preparing silicon nitride ferrovanadium by vacuum resistance method - Google Patents
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C1/00—Making non-ferrous alloys
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Abstract
The invention provides a method for preparing silicon nitride ferrovanadium by a vacuum resistance method, which comprises the steps of firstly mixing ingredients, uniformly mixing silicon nitride particles and silicon ferrovanadium particles, reacting the uniformly mixed silicon nitride particles and silicon ferrovanadium particles with nitrogen in high-temperature environments of different intervals for a certain time in a vacuum environment, and cooling to obtain the silicon nitride ferrovanadium. The invention utilizes the flame retardant effect of the silicon nitride iron to prevent the local over-high temperature in the nitriding reaction from causing the metal combustion smelting spread to obstruct the raw material nitriding reaction, the invention sets 4 temperature control intervals to ensure that the temperature at different positions of the raw material layer tends to be uniform, nitrogen also uniformly permeates to different positions of the raw material layer, and the nitrogen is dispersed in different temperature intervals to carry out the nitriding reaction, thereby dispersing the process of the exothermic reaction, not causing the heat to be aggregated in a short time, avoiding the melting phenomenon at multiple positions, and ensuring that the finally formed silicon nitride vanadium iron has better uniformity and consistency.
Description
Technical Field
The invention belongs to the technical field of silicon nitride ferrovanadium preparation, and relates to a method for preparing silicon nitride ferrovanadium, in particular to a method for preparing silicon nitride ferrovanadium by a vacuum resistance method.
Background
The existing methods for preparing silicon nitride ferrovanadium mainly comprise a self-propagating combustion method, a ball-pressing combustion method, a carbothermic reduction nitridation method, silicon ferrovanadium nitridation and the like, but all have the defects of different degrees, and the methods for producing silicon nitride vanadium alloy in the prior art generally have the problems of long process flow, high resource consumption and the like.
The method comprises the steps of firstly crushing the silicon-vanadium-iron alloy, then loading the crushed silicon-vanadium-iron alloy into a high-pressure reactor, vacuumizing the high-pressure reactor, then filling nitrogen, igniting the high-pressure reactor, keeping the pressure at 6-12 MPa for reaction, and cooling the silicon-vanadium-iron alloy under the condition of nitrogen after the reaction is finished to obtain the silicon-vanadium-iron nitride alloy. The method has the problem of low yield, so that the proportion of vanadium must be increased to a certain extent to produce the product with qualified content by using the method, and the production cost is increased to a certain extent.
Chinese patent publication No. CN109440003A discloses a method for smelting silicon vanadium nitride alloy, which comprises preparing silicon vanadium iron nitride by ball-pressing firing, feeding the ball-pressed vanadium silicon alloy into a vacuum sintering furnace, vacuumizing, heating and sintering, introducing high-purity nitrogen gas to carry out nitridation reaction when the temperature reaches 800-950 ℃, reducing vanadium pentoxide to obtain vanadium silicon iron alloy, and nitriding to obtain silicon vanadium iron nitride, wherein the content of vanadium silicon nitrogen can be ensured, the product quality is stable, but the method increases process steps for refining vanadium silicon alloy by reducing vanadium pentoxide, the cost is increased substantially, and vanadium pentoxide is used as the raw material to cause waste of vanadium resources.
Chinese patent document with publication number CN111621686A discloses a method for producing silicon vanadium nitride by smelting vanadium-rich slag, which discloses a method for producing silicon vanadium nitride by smelting vanadium-rich slag, and specifically comprises the steps of firstly mixing vanadium-rich slag, silica, coke and quick lime according to a preset weight ratio, then smelting to obtain silicon vanadium alloy, crushing the silicon vanadium alloy to be less than 20mm, and then ball-milling the crushed silicon vanadium alloy into 100-mesh powder; then adding an adhesive into the powder, uniformly mixing, and then performing compression molding and drying to obtain a material; and finally, carrying out vacuum decarburization and nitridation treatment on the material, and then cooling to obtain silicon vanadium nitride. The preparation method disclosed by the patent technology is a carbothermic reduction nitridation method, and has the main defects that: long flow and complex process.
Chinese patent document No. CN111621686A discloses a high-nitrogen low-oxygen silicon nitride ferrovanadium alloy and a preparation method thereof, the method is produced in a micro-positive pressure environment of 0.18-0.2MPa, vanadium and silicon are nitrided respectively at different temperatures in two steps, the method has the main disadvantages that: the nitridation of vanadium is completed intensively, a large amount of heat is easy to gather in a short time, and the local temperature rise at multiple positions is fast, so that more molten metal appears.
Based on the problems of the prior art in preparing silicon nitride ferrovanadium, a new preparation method of silicon nitride ferrovanadium is needed.
Disclosure of Invention
The Gibbs reaction formula of vanadium nitride in the preparation of silicon nitride ferrovanadium is as follows:
2V(s)+N2(g)＝2VN(s) ΔGθ＝-348694+166.2T(J·mol-1)
the Gibbs reaction formula of the silicon nitride iron nitride in the preparation of the silicon nitride ferrovanadium is as follows:
3Si(g)+2N2(g)＝Si3N4(s) ΔGθ＝-723+0.315T(kJ·mol-1)
from the two reactions, the vanadium nitriding reaction and the silicon nitriding reaction are exothermic reactions, particularly the heat released by the vanadium nitriding reaction is very large, when the silicon vanadium iron nitride is produced and prepared, if the process is improperly controlled, the local temperature rise of the raw materials is obvious, even metal melting occurs at multiple positions, and then the nitriding reaction is influenced, so that the finally prepared silicon vanadium iron nitride product has poor component uniformity and consistency and low nitrogen content. The invention provides a method for preparing silicon nitride ferrovanadium by a vacuum resistance method, which aims to solve the problems in the prior art and the technical problems.
A method for preparing silicon nitride ferrovanadium by a vacuum resistance method comprises the following steps of firstly mixing ingredients, uniformly mixing silicon nitride particles and silicon ferrovanadium particles, reacting the uniformly mixed silicon nitride particles and silicon ferrovanadium particles with nitrogen in high-temperature environments of different intervals for a certain time in a vacuum environment, and cooling to obtain the silicon nitride ferrovanadium, wherein the method comprises the following specific steps:
the method comprises the following steps: proportioning, namely uniformly mixing 90-97% of silicon ferrovanadium with the mass fraction of 60-120 meshes and 3-10% of silicon nitride with the mass fraction of 60-120 meshes, and uniformly spreading the mixture in a high-temperature-resistant feeding device, wherein the feeding device is of an open non-closed structure;
step two: placing the feeding device in the step one in a vacuum resistance furnace, and vacuumizing the vacuum resistance furnace;
step three: introducing nitrogen into the vacuum resistance furnace, controlling the pressure of the nitrogen in the resistance furnace to be 0.3-0.5MPa, simultaneously electrifying, heating and raising the temperature to be 600-1400 ℃, and reacting for 10-15 hours;
step four: and discharging the silicon nitride ferrovanadium product from the feeding device when the furnace temperature is reduced to below 300 ℃ in the nitrogen atmosphere.
In the invention, because the self-heat release in the raw material synthesis process is a discontinuous, non-uniform and non-compact complex combustion process, the combustion rate is limited by material transmission, a plurality of combustion heat release points can be formed, and different combustion conditions can cause combustion instability, therefore, the ferrosilicon nitride is added as a flame retardant.
In addition, the ferrosilicon nitride is added because the melting point is lower, molten metal can appear when the temperature is too high in the synthesis process, so that nitrogen gas is prevented from permeating, the ferrosilicon vanadium is unfavorable for the nitridation synthesis of ferrosilicon vanadium, and in severe cases, because the permeation rate is lower than the chemical reaction rate, gas cannot reach the combustion layer surface in time, and the surface combustion phenomenon occurs. Therefore, adding a certain amount of ferrosilicon nitride (melting point 1700 ℃) to reduce the reaction temperature can limit the burning rate, play a transition role and optimize the burning synthesis conditions.
In the nitridation process of silicon ferrovanadium and silicon carbide, the purity of the added nitrogen is high enough to ensure that the nitridation reaction of vanadium and the nitridation reaction of silicon are fully performed, and in the invention, the concentration of the introduced nitrogen in the step three is preferably greater than or equal to 99.9%.
In order to ensure the sufficient nitriding of the silicon ferrovanadium in the reaction, the thickness of the raw material layer paved in the feeding device is 8-20 cm. The lower part is difficult to nitride due to too thick raw material layer, the yield is too low due to too thin material layer, the production efficiency is not high, and the energy consumption per ton of product is high.
And further, after the feeding device in the second step is placed in the vacuum resistance furnace, the height of the raw material laid on the upper part of the feeding device from a resistance carbon rod in the vacuum resistance furnace is 10-20 cm.
In the invention, the silicon ferrovanadium added in the step one is silicon ferrovanadium extracted from vanadium slag, and the silicon ferrovanadium element components and the mass fractions of the elements are respectively as follows: v is more than or equal to 34 percent, Si is more than or equal to 16 percent, C is less than or equal to 2.0 percent, P is less than or equal to 0.2 percent, S is less than or equal to 0.1 percent, and the balance is Fe, wherein the mass fractions of the element components and the elements in the silicon nitride are respectively N: 29-32%, Si: 47-52% and the balance Fe.
By utilizing the method for preparing the silicon nitride ferrovanadium by the vacuum resistance method, the finally prepared silicon nitride ferrovanadium has the element components and the mass fractions of V more than or equal to 28 percent, TN more than or equal to 10 percent, Si more than or equal to 12 percent, C less than or equal to 2.0 percent, P less than or equal to 0.2 percent, S less than or equal to 0.1 percent and the balance of Fe.
In the third step of the invention, in order to avoid the nitridation reaction from being concentrated in the temperature range with active nitridation, 4 temperature ranges are set in the temperature range of 600-1400 ℃ to control the nitridation reaction, and the nitridation reaction is prevented from being concentrated in the temperature range with active nitridation, specifically, the temperature is raised to 600-650 ℃ and kept for 1-2 hours, the temperature is raised to 650-840 ℃ and kept for 3-5 hours, the temperature is raised to 840-1100 ℃ and kept for 3-5 hours, and the temperature is raised to 1100-1400 ℃ and kept for 3-5 hours. The nitridation reaction of vanadium and the nitridation reaction of silicon are exothermic reactions, if the nitridation active temperature interval is concentrated, local high temperature can be generated at multiple positions in a raw material layer, more metal melting phenomena occur, the uniformity and consistency of silicon nitride ferrovanadium in finished products are not facilitated, the nitridation reactions occur at different temperature intervals in a dispersing manner, the process of the exothermic reactions is dispersed, heat can not be concentrated in a short time, and the melting phenomena at multiple positions are avoided.
The invention has the outstanding technical effects that:
1. silicon ferrovanadium is adopted to prepare silicon ferrovanadium nitride, a discontinuous, non-uniform and non-compact complex combustion reaction process exists in both silicon element and vanadium element in the nitridation process, a plurality of combustion heat release points exist, moreover, when the nitridation reaction of silicon element and vanadium element belongs to an exothermic reaction, especially the nitridation reaction of vanadium, this results in localized temperatures at various locations on the surface and within the feedstock layer that are much higher than the controlled temperature within the furnace, when the local temperature rises to above 1300 ℃, the molten metal is produced, and the molten metal can spread and cover different positions of the whole raw material layer due to certain fluidity, therefore, the permeation of nitrogen is blocked, the nitridation synthesis of silicon ferrovanadium is not facilitated, the surface layer of the silicon ferrovanadium burns due to the fact that the permeation rate of the nitrogen is lower than the nitridation reaction rate in severe cases, and the nitrogen cannot permeate the lattice atom position of the silicon ferrovanadium. According to the scheme of the invention, 3-10 mass percent of silicon nitride iron is uniformly doped in the raw material, namely, countless flame retardant points are uniformly dispersed in the raw material, so that on one hand, flame of silicon ferrovanadium burnt on the surface layer is prevented from spreading to the adjacent unburned silicon ferrovanadium, on the other hand, molten metal is prevented from flowing to the adjacent position, nitrogen can be ensured to fully permeate into the raw material layer and the silicon ferrovanadium crystal lattice, and finally, the formed silicon ferrovanadium product has uniform components, sufficient nitridation and high quality.
2. In the invention, silicon ferrovanadium refined from vanadium slag can be directly used as a raw material, and a small amount (3-10%) of silicon nitride ferrosilicon is compounded to prepare a silicon ferrovanadium product with slightly lower V content than the silicon ferrovanadium. Secondly, the silicon nitride prepared by the invention has high vanadium-iron-nitrogen content.
3. In the third step, the temperature is raised to 600-650 ℃ and kept for 1-2 hours, mainly in order to ensure that the temperature at different positions of the raw material layer tends to be uniform, and nitrogen uniformly permeates to different positions of the raw material layer, so that the raw material finishes the most initial small amount of nitridation reaction; keeping the temperature of 650-840 ℃ for 3-5 hours to complete the nitridation reaction of more vanadium elements and a small part of silicon elements; keeping the temperature of 840-1100 ℃ for 3-5 hours to basically complete the nitridation reaction of all vanadium elements and part of silicon elements, and keeping the temperature of 1100-1400 ℃ for 3-5 hours to basically complete the nitridation reaction of all silicon elements. The invention controls the nitridation reaction in 4 temperature intervals, avoids the nitridation reaction from being totally concentrated in the temperature interval with active nitridation, because the vanadium nitridation reaction and the silicon nitridation reaction are both exothermic reactions, if the nitridation reaction is concentrated in the temperature interval with active nitridation, local high temperature can be caused at a plurality of positions in the raw material layer, more metal melting phenomena can be caused, the uniformity and consistency of the silicon vanadium iron nitride in the finished product can be avoided, the nitridation reaction can be caused by dispersing in different temperature intervals, the process of the exothermic reaction can be dispersed, the heat can not be concentrated in a short time, and the melting phenomena at a plurality of positions can be avoided, so that the silicon vanadium iron nitride in the finally formed product has better uniformity and consistency.
Detailed Description
Embodiments of the present invention will be described below.
Example one
The method for preparing the silicon nitride ferrovanadium by the vacuum resistance method comprises the following steps:
the method comprises the following steps: proportioning, namely, uniformly mixing 5800kg of silicon ferrovanadium with the mass of 60 meshes-120 meshes and 200kg of silicon nitride with the mass of 60 meshes-120 meshes (namely, uniformly mixing the silicon ferrovanadium and the silicon nitride according to the mass ratio of 97% to 3%), uniformly spreading the mixture in a high-temperature resistant feeding device, wherein the spreading thickness is 8cm, and the feeding device is of an open non-closed structure. The silicon-vanadium-iron alloy in the step comprises, by mass, 34% of V, 16% of Si, 2% of C, 0.2% of P, 0.1% of S and the balance of iron, wherein the silicon nitride comprises, by mass, 29% of TN, 52% of Si and the balance of iron.
Step two: placing the feeding device in the step one in a vacuum resistance furnace, vacuumizing the vacuum resistance furnace, and then electrifying to heat;
step three: introducing nitrogen with the purity of 99.9 percent into the vacuum resistance furnace, controlling the nitrogen pressure in the resistance furnace to be 0.3-0.5MPa, controlling the height of the raw material at the upper part of the feeding device to be 20cm away from a resistance carbon rod in the vacuum resistance furnace, controlling the temperature to be 600-1400 ℃, specifically controlling the temperature rise process to be 600-650 ℃, keeping for 1 hour, keeping for 5 hours at 650-840 ℃, keeping for 3 hours at 840-1100 ℃, keeping for 1 hour at 1100-1400 ℃, and controlling the total reaction time to be 10 hours;
step four: and discharging the silicon nitride ferrovanadium product from the feeding device when the furnace temperature is reduced to below 300 ℃ in the nitrogen atmosphere. Finally, the silicon nitride ferrovanadium on the lower part, the middle part and the upper part of the feeding device is respectively taken for assay, and the following results are obtained:
the silicon nitride ferrovanadium at the lower part comprises the following components by mass percentage of TN 10.96%, V27.72%, Si 14.93%, C1.73%, P0.15%, S0.06% and the balance of Fe;
the silicon nitride ferrovanadium in the middle part comprises 13.33 percent of TN, 28.28 percent of V, 15.43 percent of Si, 1.62 percent of C, 0.13 percent of P, 0.05 percent of S and the balance of Fe by mass percent;
the silicon nitride ferrovanadium on the upper part comprises 11.67 percent of TN, 27.81 percent of V, 15.28 percent of Si, 1.69 percent of C, 0.13 percent of P, 0.06 percent of S and the balance of Fe by mass percent.
The yield of silicon nitride ferrovanadium in this example is about 76%.
In the embodiment, because the raw materials scattered on the high-temperature-resistant feeding device are thin in thickness, the flame retardant effect of the silicon nitride iron is limited, the obtained silicon nitride ferrovanadium has good consistency, the mass fractions of the silicon nitride ferrovanadium components and the elements at the lower part, the middle part and the upper part of the feeding device have small differences, and the nitrogen content differences at the lower part, the middle part and the upper part are about 2%.
In this embodiment, the content of ferrosilicon nitride in the raw materials for preparing silicon vanadium iron is 3%, the flame retardant effect of ferrosilicon nitride in the raw materials is limited, and the TN content in the obtained silicon vanadium iron is normal, but the total is low because the ferrosilicon nitride effect is limited, resulting in too high local temperature, forming molten metal to spread and cover, and blocking the penetration of nitrogen.
Example two
The method for preparing the silicon nitride ferrovanadium by the vacuum resistance method comprises the following steps:
the method comprises the following steps: the method comprises the steps of proportioning, uniformly mixing 6400kg of silicon ferrovanadium with a mass of 60 meshes-120 meshes and 340kg of silicon nitride with a mass of 60 meshes-120 meshes (namely uniformly mixing the silicon ferrovanadium and the silicon nitride according to a mass ratio of 95% to 5%), uniformly spreading the mixture in a high-temperature-resistant feeding device, wherein the spreading thickness is 10cm, and the feeding device is of an open non-closed structure. The silicon-vanadium-iron alloy in the step comprises 35% of V, 18% of Si, 1.5% of C, 0.15% of P, 0.05% of S and the balance of iron, wherein the silicon nitride comprises 30% of TN, 50% of Si and the balance of iron;
step two: placing the feeding device in the step one in a vacuum resistance furnace, vacuumizing the vacuum resistance furnace, and then electrifying to heat;
step three: introducing nitrogen with the purity of 99.9 percent into the vacuum resistance furnace, controlling the nitrogen pressure in the resistance furnace to be 0.3-0.5MPa, controlling the height of the raw material at the upper part of the feeding device to be 15cm away from a resistance carbon rod in the vacuum resistance furnace, controlling the temperature to be 600-1400 ℃, specifically controlling the temperature rise process to be 600-650 ℃, keeping for 2 hours, keeping for 5 hours at 650-840 ℃, keeping for 4 hours at 840-1100 ℃, keeping for 3 hours at 1100-1400 ℃, and controlling the total reaction time to be 14 hours;
step four: and discharging the silicon nitride ferrovanadium product from the feeding device when the furnace temperature is reduced to below 300 ℃ in the nitrogen atmosphere. Finally, the silicon nitride ferrovanadium on the lower part, the middle part and the upper part of the feeding device is respectively taken for assay, and the following results are obtained:
the silicon nitride ferrovanadium at the lower part comprises 11.73 percent of TN, 27.64 percent of V, 16.76 percent of Si, 1.26 percent of C, 0.12 percent of P, 0.04 percent of S and the balance of Fe by mass percent;
the silicon nitride ferrovanadium in the middle part comprises 13.85 percent of TN, 28.61 percent of V, 17.36 percent of Si, 1.19 percent of C, 0.11 percent of P, 0.02 percent of S and the balance of Fe by mass percent;
the silicon nitride ferrovanadium on the upper part comprises 12.22 percent of TN, 28.20 percent of V, 17.14 percent of Si, 1.23 percent of C, 0.12 percent of P, 0.03 percent of S and the balance of iron by mass percent.
The yield of silicon nitride ferrovanadium in this example is about 83%.
In the embodiment, the thickness of the raw materials scattered on the high-temperature-resistant feeding device is moderate, so that the obtained silicon nitride ferrovanadium has good consistency, the mass fractions of the silicon nitride ferrovanadium components and elements at the lower part, the middle part and the upper part of the feeding device have small differences, and the nitrogen content differences of the silicon nitride ferrovanadium at the lower part, the middle part and the upper part are about 2%.
In this embodiment, the content of ferrosilicon nitride is 5%, and ferrosilicon nitride is better at the flame retardant efficiency of raw materials, has prevented that local high temperature from leading to the metal to smelt and has propagated, and silicon and vanadium can be fully nitrided, and the qualification rate of ferrosilicon vanadium reaches about 83%, and is higher than implementing one.
In the embodiment, the change range of the nitrogen pressure gauge is observed to be 0MPa to 1.5MPa within the temperature range of 600 ℃ to 650 ℃, and the nitridation reaction is supposed to be slow within the temperature range; the change amplitude of the nitrogen pressure gauge is further increased to 1-2 MPa within the temperature range of 650-840 ℃, and the nitridation reaction is accelerated within the temperature range; in the reaction range of 840-1100 ℃, the change range of the nitrogen pressure gauge is observed to be 1.5-2 MPa, and the silicon ferrovanadium can be supposed to mainly complete the nitridation reaction in the temperature range; in the range of 1100-1400 ℃, the change range of the nitrogen pressure gauge in the early stage of the reaction is observed to be 1.5-2 MPa, and the change range of the nitrogen pressure gauge in the later stage of the reaction is 0.5-1 MPa, so that the main nitridation reaction is presumed to be completed in the early stage of the reaction in the temperature range.
In the embodiment, in all temperature intervals and reaction time, the whole nitriding reaction is relatively stable, even in a high-temperature area, the change of an observed nitrogen pressure gauge is less than 2MPa, and in the later stage of the nitriding reaction, the nitrogen pressure change amplitude of 0.5MPa is also provided, presumably, the reaction temperature is set to 4 intervals, the nitriding reaction starts to slowly carry out the nitriding reaction for a long time in the early stage with lower temperature, and because partial nitriding reaction is completed in the early stage, the nitriding reaction is still active in the high-temperature interval, but the heat release amount of the nitriding reaction is controllable due to the limited nitriding amount, so that the iron melting phenomenon in the reaction is relatively less, the qualification rate of the finally obtained product is high and reaches 83%.
EXAMPLE III
The method for preparing the silicon nitride ferrovanadium by the vacuum resistance method comprises the following steps:
the method comprises the following steps: proportioning, namely uniformly mixing 7250kg of silicon ferrovanadium with the mass of 60 meshes-120 meshes and 550kg of silicon nitride with the mass of 60 meshes-120 meshes (namely uniformly mixing the silicon ferrovanadium and the silicon nitride according to the mass ratio of 93 percent to 7 percent), uniformly spreading the mixture in a high-temperature resistant feeding device, wherein the spreading thickness is 20cm, and the feeding device is of an open non-closed structure. The silicon-vanadium-iron alloy in the step comprises, by mass, 37% of V, 23% of Si, 2% of C, 0.18% of P, 0.05% of S and the balance of iron, wherein the silicon nitride comprises, by mass, 32% of TN, 47% of Si and the balance of iron.
Step two: placing the feeding device in the step one in a vacuum resistance furnace, vacuumizing the vacuum resistance furnace, and then electrifying to heat;
step three: introducing nitrogen with the purity of 99.9 percent into the vacuum resistance furnace, controlling the nitrogen pressure in the resistance furnace to be 0.3-0.5MPa, controlling the height of the raw material at the upper part of the feeding device to be 10cm away from a resistance carbon rod in the vacuum resistance furnace, controlling the temperature to be 600-1400 ℃, specifically controlling the temperature rise process to be 600-650 ℃, keeping for 2 hours, keeping for 3 hours at 650-840 ℃, keeping for 5 hours at 840-1100 ℃, keeping for 4 hours at 1100-1400 ℃, and controlling the total reaction time to be 15 hours;
step four: and discharging the silicon nitride ferrovanadium product from the feeding device when the furnace temperature is reduced to below 300 ℃ in the nitrogen atmosphere. Finally, the silicon nitride ferrovanadium on the lower part, the middle part and the upper part of the feeding device is respectively taken for assay, and the following results are obtained:
the silicon nitride ferrovanadium at the lower part comprises 11.52 percent of TN, 28.03 percent of V, 21.33 percent of Si, 1.63 percent of C, 0.16 percent of P, 0.03 percent of S and the balance of Fe by mass percent;
the silicon nitride ferrovanadium in the middle part comprises 14.56 percent of TN, 29.14 percent of V, 21.98 percent of Si, 1.57 percent of C, 0.13 percent of P, 0.02 percent of S and the balance of Fe by mass percent;
the silicon nitride ferrovanadium on the upper part comprises 12.89% of TN, 28.67% of V, 21.62% of Si, 1.51% of C, 0.15% of P, 0.03% of S and the balance of Fe by mass.
The yield of silicon nitride ferrovanadium in this example is about 81%.
In this embodiment, the thickness of the raw material scattered on the high-temperature-resistant feeding device is slightly thick, the differences in the silicon nitride ferrovanadium components and the element mass fractions of the lower part, the middle part and the upper part of the obtained silicon nitride ferrovanadium feeding device are small, and the differences in the nitrogen element contents of the silicon nitride ferrovanadium of the lower part, the middle part and the upper part are about 3%.
In the embodiment, the content of the ferrosilicon nitride is 7%, the flame retardant effect of the ferrosilicon nitride in raw materials is good, the metal smelting spreading caused by over-high local temperature is prevented, the silicon and the vanadium can be fully nitrided, and the obtained ferrosilicon nitride has moderate TN content. In this embodiment, the thickness of the raw material laid in the feeding device is 20cm, and the thickness of the laid raw material is uneven, so that the difference between the nitrogen element contents of the silicon nitride ferrovanadium at the middle part and the nitrogen element contents at the lower part is about 3%.
In the embodiment, the change range of the nitrogen pressure gauge is observed to be 0-1.5 MPa within the temperature range of 600-650 ℃, and the nitridation reaction can be presumed to start slowly within the temperature range; the change amplitude of the nitrogen pressure gauge is further increased to 1-1.5 Mpa observed in the temperature range of 650-840 ℃, and the nitridation reaction is accelerated in the temperature range; in the reaction range of 840-1100 ℃, the change range of the nitrogen pressure gauge is observed to be 1.5-2.5 MPa, and the silicon ferrovanadium can be supposed to mainly complete the nitridation reaction in the temperature range; in the range of 1100-1400 ℃, the change range of the nitrogen pressure gauge in the early stage of the reaction is observed to be 1.5-2 MPa, and the change range of the nitrogen pressure gauge in the later stage of the reaction is 0.5-1 MPa, so that the main nitridation reaction is presumed to be completed in the early stage of the reaction in the temperature range.
Example four
The method for preparing the silicon nitride ferrovanadium by the vacuum resistance method comprises the following steps:
the method comprises the following steps: the method comprises the steps of proportioning, uniformly mixing 6500kg of silicon ferrovanadium with a mass of 60 meshes-120 meshes and 720kg of silicon nitride with a mass of 60 meshes-120 meshes (namely, uniformly mixing the silicon ferrovanadium and the silicon nitride according to a mass ratio of 90% to 10%), uniformly spreading the mixture in a high-temperature-resistant feeding device, wherein the spreading thickness is 15cm, and the feeding device is of an open non-closed structure. The silicon-vanadium-iron alloy in the step comprises, by mass, 36% of V, 20% of Si, 1.4% of C, 0.15% of P, 0.05% of S and the balance of iron, wherein the silicon nitride comprises, by mass, 31% of TN, 49% of Si and the balance of iron;
step two: placing the feeding device in the step one in a vacuum resistance furnace, vacuumizing the vacuum resistance furnace, and then electrifying to heat;
step three: introducing nitrogen with the purity of 99.9 percent into the vacuum resistance furnace, controlling the nitrogen pressure in the resistance furnace to be 0.3-0.5MPa, controlling the height of the raw material at the upper part of the feeding device to be 18cm away from a resistance carbon rod in the vacuum resistance furnace, controlling the temperature to be 600-1400 ℃, specifically controlling the temperature rise process to be 600-650 ℃, keeping for 1 hour, keeping for 4 hours at 650-840 ℃, keeping for 5 hours at 840-1100 ℃, keeping for 5 hours at 1100-1400 ℃, and controlling the total reaction time to be 15 hours;
step four: and discharging the silicon nitride ferrovanadium product from the feeding device when the furnace temperature is reduced to below 300 ℃ in the nitrogen atmosphere. Finally, the silicon nitride ferrovanadium on the lower part, the middle part and the upper part of the feeding device is respectively taken for assay, and the following results are obtained:
the silicon nitride ferrovanadium at the lower part comprises 10.71 percent of TN, 27.02 percent of V, 19.32 percent of Si, 1.12 percent of C, 0.12 percent of P, 0.03 percent of S and the balance of Fe by mass percent.
The silicon nitride ferrovanadium in the middle part comprises 13.06% of TN, 28.37% of V, 19.77% of Si, 1.10% of C, 0.12% of P, 0.02% of S and the balance of Fe by mass.
The silicon nitride ferrovanadium on the upper part comprises 12.01 percent of TN, 27.69 percent of V, 19.04 percent of Si, 1.12 percent of C, 0.12 percent of P, 0.03 percent of S and the balance of iron by mass percent.
The yield of silicon nitride ferrovanadium in this example is about 78%.
In this embodiment, the raw materials scattered on the high temperature resistant feeding device have appropriate thickness, and the silicon nitride ferrovanadium components and element mass fractions of the lower part, the middle part and the upper part of the obtained silicon nitride ferrovanadium feeding device are consistent.
In the embodiment, the content of the ferrosilicon nitride is 10%, the ferrosilicon nitride has a good flame retardant effect in the raw materials, the TN content of the obtained ferrosilicon vanadium is moderate, and the V content of the obtained ferrosilicon vanadium is lower than that of the examples one to four because the V content of the raw materials is lower than that of the examples one to four, but within a reasonable range.
EXAMPLE five
The method comprises the following steps: proportioning, namely uniformly mixing 60-120 meshes of 6370kg of silicon ferrovanadium and 60-120 meshes of 70kg of silicon nitride (namely uniformly mixing the silicon ferrovanadium and the silicon nitride according to the mass ratio of 99 to 1 percent), uniformly spreading the mixture in a high-temperature-resistant feeding device, wherein the laying thickness is 10cm, and the feeding device is of an open non-closed structure. The silicon-vanadium-iron alloy in the step comprises, by mass, 35% of V, 18% of Si, 1.5% of C, 0.15% of P, 0.05% of S and the balance of iron, wherein the silicon nitride comprises, by mass, 30% of N, 50% of Si and the balance of iron.
Step two: placing the feeding device in the step one in a vacuum resistance furnace, vacuumizing the vacuum resistance furnace, and then electrifying to heat;
step three: introducing nitrogen with the purity of 99.9 percent into the vacuum resistance furnace, controlling the nitrogen pressure in the resistance furnace to be 0.3-0.5MPa, controlling the height of the raw material at the upper part of the feeding device to be 15cm away from a resistance carbon rod in the vacuum resistance furnace, controlling the temperature to be 600-1400 ℃, specifically controlling the temperature rise process to be 600-650 ℃, keeping for 2 hours, keeping for 5 hours at 650-840 ℃, keeping for 4 hours at 840-1100 ℃, keeping for 3 hours at 1100-1400 ℃, and controlling the total reaction time to be 14 hours;
step four: and discharging the silicon nitride ferrovanadium product from the feeding device when the furnace temperature is reduced to below 300 ℃ in the nitrogen atmosphere. Finally, the silicon nitride ferrovanadium on the lower part, the middle part and the upper part of the feeding device is respectively taken for assay, and the following results are obtained:
the silicon nitride ferrovanadium at the lower part comprises 11.06 percent of TN, 28.07 percent of V, 17.33 percent of Si, 1.26 percent of C, 0.12 percent of P, 0.03 percent of S and the balance of Fe by mass percent.
The silicon nitride ferrovanadium in the middle part comprises 13.32 percent of TN, 29.61 percent of V, 17.62 percent of Si, 1.21 percent of C, 0.12 percent of P, 0.02 percent of S and the balance of Fe by mass percent.
The silicon nitride ferrovanadium on the upper part comprises 12.53 percent of TN, 28.65 percent of V, 17.17 percent of Si, 1.25 percent of C, 0.12 percent of P, 0.03 percent of S and the balance of iron by mass percent.
The yield of silicon nitride ferrovanadium in this example is about 65%.
In this example. The quality of the ferrosilicon nitride accounts for 1 percent of the total mass of the raw materials, the ferrosilicon nitride has poor flame retardant effect on the raw materials, so that the local temperature is too high, the metal smelting is spread, the nitriding reaction is blocked, the local smelting trace of the raw materials can be observed after the product is discharged from the furnace, and the reasonable rate of the product is 65 percent.
Comparative example 1
The difference between the comparative example and the second example is that in the first step, no silicon nitride is added, and the other preparation processes are the same as those in the second example, specifically:
the method comprises the following steps: uniformly scattering 60-120 meshes of 6800kg of silicon ferrovanadium in a high-temperature resistant feeding device, wherein the laying thickness is 10cm, and the feeding device is of an open non-closed structure. The silicon-vanadium-iron alloy in the step comprises, by mass, 35% of V, 18% of Si, 1.5% of C, 0.15% of P, 0.05% of S and the balance of iron, wherein the silicon nitride comprises, by mass, 30% of N, 50% of Si and the balance of iron.
Step two: placing the feeding device in the step one in a vacuum resistance furnace, vacuumizing the vacuum resistance furnace, and then electrifying to heat;
step three: introducing nitrogen with the purity of 99.9 percent into the vacuum resistance furnace, controlling the nitrogen pressure in the resistance furnace to be 0.3-0.5MPa, controlling the height of the raw material at the upper part of the feeding device to be 15cm away from a resistance carbon rod in the vacuum resistance furnace, controlling the temperature to be 600-1400 ℃, specifically controlling the temperature rise process to be 600-650 ℃, keeping for 2 hours, keeping for 5 hours at 650-840 ℃, keeping for 4 hours at 840-1100 ℃, keeping for 3 hours at 1100-1400 ℃, and controlling the total reaction time to be 14 hours;
step four: and discharging the silicon nitride ferrovanadium product from the feeding device when the furnace temperature is reduced to below 300 ℃ in the nitrogen atmosphere. Finally, the silicon nitride ferrovanadium on the lower part, the middle part and the upper part of the feeding device is respectively taken for assay, and the following results are obtained:
the silicon nitride ferrovanadium at the lower part comprises 9.89 percent of TN, 26.98 percent of V, 17.16 percent of Si, 1.31 percent of C, 0.12 percent of P, 0.03 percent of S and the balance of Fe by mass percent.
The silicon nitride ferrovanadium in the middle part comprises 12.65 percent of TN, 28.32 percent of V, 17.25 percent of Si, 1.23 percent of C, 0.11 percent of P, 0.02 percent of S and the balance of Fe by mass percent.
The silicon nitride ferrovanadium on the upper part comprises 10.72 percent of TN, 27.27 percent of V, 17.36 percent of Si, 1.36 percent of C, 0.12 percent of P, 0.03 percent of S and the balance of Fe by mass percent.
The yield of silicon nitride ferrovanadium in this example is about 50%.
In this contrast, silicon iron nitride is not added, so that the metal smelting is spread, the nitriding reaction is blocked, and after the product is discharged from the furnace, the raw material smelting trace can be obviously observed, and the qualified rate of silicon nitride ferrovanadium is very low, so that the production requirement can not be met.
Comparative example No. two
The difference between the comparative example and the second example is that in the first step, 60-120 meshes of 5780kg silicon ferrovanadium with mass and 60-120 meshes of 1020kg silicon nitride with mass are uniformly mixed (namely, the silicon ferrovanadium and the silicon nitride are uniformly mixed according to the mass ratio of 85% to 15%), and then are uniformly scattered in a high-temperature resistant feeding device, and other preparation processes are the same as those in the second example, specifically:
the method comprises the following steps: proportioning, namely uniformly mixing 5780kg of silicon ferrovanadium with the mass of 60 meshes-120 meshes and 1020kg of silicon nitride with the mass of 60 meshes-120 meshes (namely uniformly mixing the silicon ferrovanadium and the silicon nitride according to the mass ratio of 85% to 15%), uniformly spreading the mixture in a high-temperature resistant feeding device, wherein the spreading thickness is 10cm, and the feeding device is of an open non-closed structure. The silicon-vanadium-iron alloy in the step comprises, by mass, 35% of V, 18% of Si, 1.5% of C, 0.15% of P, 0.05% of S and the balance of iron, wherein the silicon nitride comprises, by mass, 30% of TN, 50% of Si and the balance of iron.
Step two: placing the feeding device in the step one in a vacuum resistance furnace, vacuumizing the vacuum resistance furnace, and then electrifying to heat;
step three: introducing nitrogen with the purity of 99.9 percent into the vacuum resistance furnace, controlling the nitrogen pressure in the resistance furnace to be 0.3-0.5MPa, controlling the height of the raw material at the upper part of the feeding device to be 15cm away from a resistance carbon rod in the vacuum resistance furnace, controlling the temperature to be 600-1400 ℃, specifically controlling the temperature rise process to be 600-650 ℃, keeping for 2 hours, keeping for 5 hours at 650-840 ℃, keeping for 4 hours at 840-1100 ℃, keeping for 3 hours at 1100-1400 ℃, and controlling the total reaction time to be 14 hours;
step four: and discharging the silicon nitride ferrovanadium product from the feeding device when the furnace temperature is reduced to below 300 ℃ in the nitrogen atmosphere. Finally, the silicon nitride ferrovanadium on the lower part, the middle part and the upper part of the feeding device is respectively taken for assay, and the following results are obtained:
the silicon nitride ferrovanadium at the lower part comprises 9.18 percent of TN, 25.42 percent of V, 18.69 percent of Si, 1.12 percent of C, 0.09 percent of P, 0.02 percent of S and the balance of Fe by mass percent.
The silicon nitride ferrovanadium in the middle part comprises 12.06% of TN, 26.24% of V, 18.92% of Si, 1.03% of C, 0.08% of P, 0.01% of S and the balance of Fe by mass.
The silicon nitride ferrovanadium on the upper part comprises 10.72 percent of TN, 25.86 percent of V, 18.37 percent of Si, 1.09 percent of C, 0.09 percent of P, 0.02 percent of S and the balance of Fe by mass percent.
The yield of silicon nitride ferrovanadium in this example is about 40%.
In this contrast, the ferrosilicon nitride's content is 15%, adds ferrosilicon nitride too high, can make the vanadium content of totality reduce in the mixed raw materials, just must add the ferrovanadium of high vanadium content in order to guarantee that final product vanadium content is up to standard, and this can lead to manufacturing cost to rise.
Comparative example No. three
The difference between the comparative example and the second example is that in the first step, 7800kg of silicon ferrovanadium with a mass of 60 meshes-120 meshes and 400kg of silicon nitride with a mass of 60 meshes-120 meshes are uniformly mixed (namely, the silicon ferrovanadium and the silicon nitride are uniformly mixed according to a mass ratio of 95% to 5%), and then the mixture is uniformly scattered in a high-temperature resistant feeding device, the paving thickness is 25cm, and other preparation processes are the same as those in the second example, specifically:
the method comprises the following steps: the method comprises the steps of proportioning, namely, 7800kg of silicon ferrovanadium with the mass of 60 meshes-120 meshes and 400kg of silicon nitride with the mass of 60 meshes-120 meshes are uniformly mixed (namely, the silicon ferrovanadium and the silicon nitride are uniformly mixed according to the mass ratio of 95% to 5%), and then the mixture is uniformly scattered in a high-temperature resistant feeding device with the laying thickness of 25cm, wherein the feeding device is of an open non-closed structure. The silicon-vanadium-iron alloy in the step comprises, by mass, 35% of V, 18% of Si, 1.5% of C, 0.15% of P, 0.05% of S and the balance of iron, wherein the silicon nitride comprises, by mass, 30% of N, 50% of Si and the balance of iron.
Step two: placing the feeding device in the step one in a vacuum resistance furnace, vacuumizing the vacuum resistance furnace, and then electrifying to heat;
step three: introducing nitrogen with the purity of 99.9 percent into the vacuum resistance furnace, controlling the nitrogen pressure in the resistance furnace to be 0.3-0.5MPa, controlling the height of the raw material at the upper part of the feeding device to be 15cm away from a resistance carbon rod in the vacuum resistance furnace, controlling the temperature to be 600-1400 ℃, specifically controlling the temperature rise process to be 600-650 ℃, keeping for 2 hours, keeping for 5 hours at 650-840 ℃, keeping for 4 hours at 840-1100 ℃, keeping for 3 hours at 1100-1400 ℃, and controlling the total reaction time to be 14 hours;
step four: and discharging the silicon nitride ferrovanadium product from the feeding device when the furnace temperature is reduced to below 300 ℃ in the nitrogen atmosphere. Finally, the silicon nitride ferrovanadium on the lower part, the middle part and the upper part of the feeding device is respectively taken for assay, and the following results are obtained:
the silicon nitride ferrovanadium at the lower part comprises 10.26 percent of TN, 27.82 percent of V, 17.25 percent of Si, 1.28 percent of C, 0.13 percent of P, 0.04 percent of S and the balance of Fe by mass percent.
The silicon nitride ferrovanadium in the middle part comprises 13.52 percent of TN, 28.69 percent of V, 17.45 percent of Si, 1.26 percent of C, 0.13 percent of P, 0.02 percent of S and the balance of Fe by mass percent.
The silicon nitride ferrovanadium on the upper part comprises 12.07 percent of TN, 28.11 percent of V, 17.39 percent of Si, 1.28 percent of C, 0.13 percent of P, 0.03 percent of S and the balance of iron by mass percent.
The yield of silicon nitride ferrovanadium in this example is about 55%.
In this contrast, the material of adding is thicker, and the raw materials layer is too thick can cause the bottom to be difficult to the nitride to penetrate, gets the goods at feeding device bottom, middle part and top and tests, and nitrogen content is obviously less than middle part and top in the goods of bottom, and middle part and bottom silicon nitride ferrovanadium nitrogen content differ about 3.3%, will cause output too low when bed thickness is too thin, and production efficiency is not high, and ton product energy consumption is high. The product percent of pass of the comparative example is too low, and does not meet the production requirement.
Comparative example No. four
The difference between the comparative example and the second example is that in the third step, the temperature is controlled to 600-1400 ℃, the temperature is specifically controlled to be kept for 5 hours when the temperature rise process is controlled to be 600-800 ℃, the temperature is kept for 4 hours when the temperature is 800-1100 ℃, the temperature is kept for 5 hours when the temperature is 1100-1400 ℃, and the total reaction time is 14 hours; the other preparation processes are the same as the examples, and specifically are as follows:
the method comprises the following steps: the method comprises the steps of proportioning, uniformly mixing 6460kg of silicon ferrovanadium with a mass of 60 meshes-120 meshes and 340kg of silicon nitride with a mass of 60 meshes-120 meshes (namely, uniformly mixing the silicon ferrovanadium and the silicon nitride according to a mass ratio of 95% to 5%), uniformly spreading the mixture in a high-temperature-resistant feeding device, wherein the spreading thickness is 10cm, and the feeding device is of an open non-closed structure. The silicon-vanadium-iron alloy in the step comprises, by mass, 35% of V, 18% of Si, 1.5% of C, 0.15% of P, 0.05% of S and the balance of iron, wherein the silicon nitride comprises, by mass, 30% of TN, 50% of Si and the balance of iron.
Step two: placing the feeding device in the step one in a vacuum resistance furnace, vacuumizing the vacuum resistance furnace, and then electrifying to heat;
step three: introducing nitrogen with the purity of 99.9 percent into the vacuum resistance furnace, controlling the nitrogen pressure in the resistance furnace to be 0.3-0.5MPa, controlling the height of the raw material at the upper part of the feeding device to be 15cm away from a resistance carbon rod in the vacuum resistance furnace, controlling the temperature to be 600-1400 ℃, specifically controlling the temperature rise process to be 600-800 ℃, keeping for 4 hours, keeping for 5 hours at 800-1100 ℃, keeping for 5 hours at 1100-1400 ℃, and controlling the total reaction time to be 14 hours;
step four: and discharging the silicon nitride ferrovanadium product from the feeding device when the furnace temperature is reduced to below 300 ℃ in the nitrogen atmosphere. Finally, the silicon nitride ferrovanadium on the lower part, the middle part and the upper part of the feeding device is respectively taken for assay, and the following results are obtained:
the silicon nitride ferrovanadium at the lower part comprises 11.02 percent of TN, 27.11 percent of V, 17.89 percent of Si, 1.23 percent of C, 0.12 percent of P, 0.02 percent of S and the balance of Fe by mass percent.
The silicon nitride ferrovanadium in the middle part comprises 13.32% of TN, 28.32% of V, 17.43% of Si, 1.17% of C, 0.12% of P, 0.02% of S and the balance of Fe by mass.
The silicon nitride ferrovanadium on the upper part comprises 11.34 percent of TN, 27.85 percent of V, 16.62 percent of Si, 1.20 percent of C, 0.12 percent of P, 0.02 percent of S and the balance of Fe by mass percent.
The yield of silicon nitride ferrovanadium in this example is about 52%.
In the comparative example, in the reaction range of 600 ℃ to 800 ℃, the change of the nitrogen pressure gauge is observed within the first 1h and is less than 0.5MPa, the nitridation reaction is supposed to start in the stage, the nitrogen pressure change gauge is observed within the stage of 1-2 h, the nitrogen pressure change gauge is observed within the range of 0.5MPa to 1MPa, the reaction is supposed to start to slowly proceed in the stage, the change amplitude of the nitrogen pressure gauge is observed to increase to 1.5-2 MPa in the later stage of the reaction, and the nitridation reaction is supposed to start to accelerate in the later stage; in the range of 800-1100 ℃, the variation amplitude of a nitriding reaction pressure gauge reaches 3.5Mpa at most, but in the later stage of the reaction, the variation of the pressure gauge is observed to drop to 0.5 Mpa-1 Mpa in detail, and the nitriding reaction is mainly suddenly reduced in the early stage and the later stage of the reaction; in the temperature range of 1100-1400 ℃, the change of the nitrogen nitride pressure gauge was observed to be less than 0.2MPa, and it is estimated that the nitriding reaction was almost stopped in this temperature range.
After the nitriding reaction of the comparative example is finished, a plurality of metal melting phenomena occur, the obtained product is poor in component uniformity and low in nitrogen content, the presumed reason is that the nitriding reaction is an exothermic reaction, a fixed temperature range is set, the nitriding reaction is completely concentrated in a certain temperature range (800-1100 ℃), the local temperature is too high, the raw material is burnt, melted and spread, the nitriding reaction is hindered, the nitriding reaction is almost stopped in the temperature range of 1100-1400 ℃, the product yield of the comparative example is 52%, the yield is too low, and the production requirement is not met.
Comparative example five
The difference between the comparative example and the second example is that in the third step, the temperature is controlled to 600-1400 ℃, the temperature is specifically kept for 2 hours when the temperature rise process is controlled to 600-800 ℃, the temperature is kept for 12 hours when the temperature is 800-1400 ℃, and the total reaction time is 14 hours; the other preparation processes are the same as the examples, and specifically are as follows:
the method comprises the following steps: the method comprises the steps of proportioning, uniformly mixing 6460kg of silicon ferrovanadium with a mass of 60 meshes-120 meshes and 340kg of silicon nitride with a mass of 60 meshes-120 meshes (namely, uniformly mixing the silicon ferrovanadium and the silicon nitride according to a mass ratio of 95% to 5%), uniformly spreading the mixture in a high-temperature-resistant feeding device, wherein the spreading thickness is 10cm, and the feeding device is of an open non-closed structure. The silicon-vanadium-iron alloy in the step comprises, by mass, 35% of V, 18% of Si, 1.5% of C, 0.15% of P, 0.05% of S and the balance of iron, wherein the silicon nitride comprises, by mass, 30% of TN, 50% of Si and the balance of iron.
Step two: placing the feeding device in the step one in a vacuum resistance furnace, vacuumizing the vacuum resistance furnace, and then electrifying to heat;
step three: introducing nitrogen with the purity of 99.9 percent into the vacuum resistance furnace, controlling the nitrogen pressure in the resistance furnace to be 0.3-0.5MPa, controlling the height of the raw material at the upper part of the feeding device to be 15cm away from a resistance carbon rod in the vacuum resistance furnace, controlling the temperature to be 600-1400 ℃, specifically controlling the temperature rise process to be 600-800 ℃ and keeping for 2 hours, controlling the temperature to be 800-1400 ℃ and keeping for 12 hours, and controlling the total reaction time to be 14 hours;
step four: and discharging the silicon nitride ferrovanadium product from the feeding device when the furnace temperature is reduced to below 300 ℃ in the nitrogen atmosphere. Finally, the silicon nitride ferrovanadium on the lower part, the middle part and the upper part of the feeding device is respectively taken for assay, and the following results are obtained:
the silicon nitride ferrovanadium at the lower part comprises 9.92 percent of TN, 27.52 percent of V, 17.12 percent of Si, 1.25 percent of C, 0.12 percent of P, 0.02 percent of S and the balance of Fe by mass percent.
The silicon nitride ferrovanadium in the middle part comprises 12.17 percent of TN, 28.21 percent of V, 17.29 percent of Si, 1.13 percent of C, 0.12 percent of P, 0.02 percent of S and the balance of Fe by mass percent.
The silicon nitride ferrovanadium on the upper part comprises 10.65 percent of TN, 27.38 percent of V, 16.97 percent of Si, 1.22 percent of C, 0.12 percent of P, 0.02 percent of S and the balance of Fe by mass percent.
The yield of silicon nitride ferrovanadium in this example is about 44%.
In the comparative example, in the reaction interval of 600 ℃ to 800 ℃, the nitrogen pressure gauge is observed to change by less than 0.5MPa within the first 1h, the nitridation reaction is supposed to start in the stage, and the nitrogen pressure gauge is observed to change by 0.5MPa to 1MPa within the stage of 1h to 2h, and the reaction is supposed to start slowly in the stage; in the range of 1100-1400 ℃, the variation amplitude of the nitrogen nitride pressure gauge is observed to reach 3-3.5 Mpa in the middle reaction period, and the variation of the nitrogen pressure gauge is less than 0.2Mpa in the later reaction period, so that the nitridation reaction is supposed to be very active in the temperature range, and the nitridation reaction is almost stopped in the later reaction period.
In the comparative example, more metal melting phenomena occur, the uniformity of the obtained product components is poorer than that of the comparative example IV, and the nitrogen content is lower than that of the comparative example IV, which is presumed to be caused by the fact that the nitriding reaction is exothermic and is set in a fixed temperature range, the nitriding reaction is totally concentrated in the fixed temperature range (1100-1400 ℃), so that the local temperature in the nitriding reaction is too high, the raw materials are burnt and melted to spread and block the nitriding reaction, and the product yield of the comparative example is too low, only 44%, and the comparative example is not in line with production requirements.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (7)
1. A method for preparing silicon nitride ferrovanadium by a vacuum resistance method is characterized by comprising the following steps:
the method comprises the following steps: proportioning, namely uniformly mixing 90-97% of silicon ferrovanadium with the mass fraction of 60-120 meshes and 3-10% of silicon nitride with the mass fraction of 60-120 meshes, and uniformly spreading the mixture in a high-temperature-resistant feeding device, wherein the feeding device is of an open non-closed structure;
step two: placing the feeding device in the step one in a vacuum resistance furnace, and vacuumizing the vacuum resistance furnace;
step three: introducing nitrogen into the vacuum resistance furnace, controlling the pressure of the nitrogen in the resistance furnace to be 0.3-0.5MPa, simultaneously electrifying, heating and raising the temperature to be 600-1400 ℃, and reacting for 10-15 hours;
step four: and discharging the silicon nitride ferrovanadium product from the feeding device when the furnace temperature is reduced to below 300 ℃ in the nitrogen atmosphere.
2. The method for preparing silicon nitride ferrovanadium by vacuum resistance method according to claim 1, wherein the nitrogen concentration is 99.9%.
3. The method for preparing silicon nitride ferrovanadium by using the vacuum resistance method according to claim 1, wherein the thickness of the raw material layer laid in the feeding device is 8-20 cm.
4. The method for preparing silicon nitride ferrovanadium by a vacuum resistance method according to claim 1, wherein after the feeding device is placed in a vacuum resistance furnace, the height of the raw material laid on the upper part of the feeding device from a resistance carbon rod in the vacuum resistance furnace is 10-20 cm.
5. The method for preparing silicon-vanadium-iron nitride by the vacuum resistance method according to claim 1, wherein the silicon-vanadium-iron is silicon-vanadium-iron extracted from vanadium slag, the mass fractions of the elemental components and the elements of the silicon-vanadium-iron are respectively V not less than 34%, Si not less than 16%, C not more than 2.0%, P not more than 0.2%, S not more than 0.1%, and the balance of Fe, and the mass fractions of the elemental components and the elements of the silicon nitride are respectively N: 29-32 percent of Si, 47-52 percent of Si and the balance of Fe.
6. The method for preparing silicon nitride ferrovanadium by a vacuum resistance method according to claim 5, wherein the finally prepared silicon nitride ferrovanadium comprises the following elements by mass percent, V is greater than or equal to 28%, TN is greater than or equal to 10%, Si is greater than or equal to 12%, C is less than or equal to 2.0%, P is less than or equal to 0.2%, S is less than or equal to 0.1%, and the balance is Fe.
7. The method for preparing silicon nitride ferrovanadium by vacuum resistance as claimed in claim 5, wherein in the third step, the heating temperature is controlled to 600-1400 ℃, specifically, the temperature is raised to 600-650 ℃ and kept for 1-2 hours, the temperature is raised to 650-840 ℃ and kept for 3-5 hours, the temperature is raised to 840-1100 ℃ and kept for 3-5 hours, and the temperature is raised to 1100-1400 ℃ and kept for 3-5 hours.
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| CN113604696B (en) | 2022-05-10 |
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