Graphite-free boron carbide smelting production method

Abstract

The invention discloses a graphite-free boron carbide smelting production method, which is characterized in that boron carbide is prepared based on a carbon thermal reduction method, raw materials are prepared according to a certain raw material ratio and a grain size distribution mode and then are fed into a furnace to be heated, and the performance of the boron carbide is improved under the condition that graphite is not used as a reducing agent by heating and changing a charging and power transmission mode; the method has the advantages that the problem that the performance of the boron carbide is reduced due to more residual graphite is solved, the utilization rate of the raw materials is improved, the optimal preparation condition is determined by optimizing the process parameters such as the reaction temperature, the heat preservation time and the raw material ratio, and the prepared boron carbide has high purity, good crystallinity and excellent performance and is suitable for industrial production. And a powerful technical support is provided for popularization in practical application.

Description

Technical Field

[0001] The invention belongs to the technical field of ceramic material preparation, and in particular relates to a smelting production method of graphite-free boron carbide. Background Art

[0002] The raw materials for traditional boron carbide production are boric acid, graphite, petroleum coke, carbon black and other materials. Graphite is irreplaceable in traditional processes. Its function is to reduce the resistivity of the charge and increase the conductivity of the material. However, from the perspective of reaction kinetics, graphite is very inert as a reducing agent; from the perspective of reaction products, more graphite remains after the reduction product, resulting in a decrease in the performance of boron carbide, especially in the field of special grinding. However, the traditional process without adding graphite will lead to the deterioration of the entire smelting furnace condition, abnormalities in the furnace such as electrode jitter, and subsequent normal production will be difficult. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides a graphite-free smelting method, including solving the problems of too high resistivity of furnace charge, decreased carbon thermal reduction ability and decreased product performance caused by excessive graphite residue.

[0004] The specific technical scheme is as follows: A graphite-free boron carbide smelting production method, based on the carbon thermal reduction method to prepare boron carbide, including raw material preparation, raw material mixing, furnace loading, heating, reduction reaction, heat preservation, cooling and other steps, wherein the change method in raw material preparation is:

[0005] S1. Raw material ratio and particle size distribution in the raw material preparation step. Raw material ratio is one of the main factors to improve the carbon thermal reduction reaction. In order to ensure that enough carbon participates in the reduction reaction, raw material ratio in raw material preparation should be carried out. The purpose of particle size distribution is to improve the conductivity in the furnace, optimize the particle size distribution of the charge, control the particle size and distribution of the charge, and reduce the contact resistance between particles:

[0006] S1.1 Boric acid, petroleum coke and carbon black are mixed in the following weight ratios: boric acid 90-100, petroleum coke 24-26, carbon black 1.8-2.2;

[0007] S1.2 The petroleum coke is graded; the particle size of the petroleum coke is to increase the specific surface area of ​​carbon to fully contact with the boron material, thereby increasing the contact area of ​​the reaction, improving the reaction efficiency and accelerating the reaction rate;

[0008] The charging method in the S2 furnace charging step is:

[0009] S2.1 Push the hot material into the furnace core, add the cold material around the furnace core, and compact the material;

[0010] The smelting charging and power supply method in the S3 heating step is:

[0011] S3.1 increases the operating voltage from 100V to 150V;

[0012] S2.2 The interval between each charging is shortened from 4 hours to 2.5 hours. After each charging, the charge is compacted to reduce the porosity and improve the current conduction path. The original intermittent power supply is adjusted to continuous power supply.

[0013] S3.3 Reduce the adjustment rate of electrode lifting and lowering, and adjust the lifting and lowering speed of the inverter to 1mm / s~5mm / s;

[0014] The increase in operating voltage mainly solves the problem that after the graphite is removed, the operating resistance in the furnace increases, which leads to a decrease in the power input into the furnace. After the voltage is increased, the input power in the furnace increases, which speeds up the reaction speed and increases the furnace temperature, thereby promoting physical and chemical reactions. When the voltage is increased, more Joule heat is generated at the same time, which helps to melt the raw materials, improve the flow of materials, promote the removal of impurities, reduce the residue of graphite, and avoid electrode jitter.

[0015] The operation method in the S4 heat preservation and cooling step is:

[0016] S4.1 The crystal blocks after being taken out of the furnace are pushed into the cooling chamber, and the time for the temperature in the furnace to drop to room temperature is adjusted to 96-120 hours.

[0017] The particle size distribution in step S1.2) is as follows: 0.6 mm to 1 mm is 60% to 63%, 0.1 mm to 0.6 mm is 27% to 32%, and 0 mm to 0.1 mm is 8% to 11%.

[0018] The particle size range of carbon black is 0.01mm to 0.05mm.

[0019] The invention has the advantages that the method solves the influence of graphite residue on product performance, solves the problems of high resistivity and decreased carbon thermal reduction ability in the furnace without adding graphite, delays the cooling rate by heat preservation in the cooling chamber, and makes the boron carbide unit cell recrystallize to achieve the crystal density, and the produced boron carbide has high purity, high hardness, high density, and high output rate of high-quality boron carbide. DETAILED DESCRIPTION

[0020] The present invention is further described below with reference to specific embodiments.

[0021] Example 1

[0022] 1. Prepare the raw materials according to the following weight percentages: boric acid 100, petroleum coke 25, carbon black 1.8;

[0023] 2. The petroleum coke is graded to 60% to 63% for 0.6mm to 1mm, 27% to 32% for 0.1mm to 0.6mm, 8% to 11% for 0mm to 0.1mm, and the carbon black particle size is 0.01mm to 0.05mm;

[0024] 3. Boron carbide was prepared by carbothermal reduction method with an operating voltage of 150V;

[0025] 4. The interval between each charging is 2.5 hours, and the charge is compacted after each charging;

[0026] 5. Each time the material is added, it is distributed according to step 1) and step 2), the hot material is pushed into the furnace core, the cold material is added to the periphery of the furnace core, and the material is compacted;

[0027] 6. Reduce the adjustment rate of electrode lifting and lowering, and adjust the lifting speed of the inverter to 1mm / s;

[0028] 7. The crystal blocks after being taken out of the furnace are pushed into the cooling chamber, and the time for the temperature in the furnace to drop to room temperature is adjusted to 96 hours;

[0029] Through the above processing steps, the chemical index contents are shown in Table 1 below, and each numerical unit is a percentage:

[0030]

[0031] Table 1

[0032] Example 2

[0033] 1. Prepare the raw materials according to the following weight percentage: boric acid 95, petroleum coke 24, carbon black 2.2;

[0034] 2. The petroleum coke is graded to 60% to 63% for 0.6mm to 1mm, 27% to 32% for 0.1mm to 0.6mm, 8% to 11% for 0mm to 0.1mm, and the carbon black particle size is 0.01mm to 0.05mm;

[0035] 3. Boron carbide was prepared by carbothermal reduction method with an operating voltage of 150V;

[0036] 4. The interval between each charging is 2.5 hours, and the charge is compacted after each charging;

[0037] 5. Each time the material is added, it is distributed according to step 1) and step 2), the hot material is pushed into the furnace core, the cold material is added to the periphery of the furnace core, and the material is compacted;

[0038] 6. Reduce the adjustment rate of electrode lifting and lowering, and adjust the lifting speed of the inverter to 1mm / s;

[0039] 7. The crystal blocks after being taken out of the furnace are pushed into the cooling chamber, and the time for the temperature in the furnace to drop to room temperature is adjusted to 96 hours;

[0040] Through the above processing steps, the chemical index contents are shown in Table 2 below, and each numerical unit is a percentage:

[0041]

[0042] Table 2

[0043] Example 3

[0044] 1. Prepare the raw materials according to the following weight percentages: 90% boric acid, 26% petroleum coke, and 2.0% carbon black;

[0045] 2. The petroleum coke is graded to 60% to 63% for 0.6mm to 1mm, 27% to 32% for 0.1mm to 0.6mm, 8% to 11% for 0mm to 0.1mm, and the carbon black particle size is 0.01mm to 0.05mm;

[0046] 3. Boron carbide was prepared by carbothermal reduction method with an operating voltage of 150V;

[0047] 4. The interval between each charging is 2.5 hours, and the charge is compacted after each charging;

[0048] 5. Each time the material is added, it is distributed according to step 1) and step 2), the hot material is pushed into the furnace core, the cold material is added to the periphery of the furnace core, and the material is compacted;

[0049] 6. Reduce the adjustment rate of electrode lifting and lowering, and adjust the lifting speed of the inverter to 1mm / s;

[0050] 7. The crystal blocks after being taken out of the furnace are pushed into the cooling chamber, and the time for the temperature in the furnace to drop to room temperature is adjusted to 96 hours;

[0051] Through the above processing steps, the chemical index contents are shown in Table 3 below, and each numerical unit is a percentage:

[0052]

[0053] Table 3

[0054] Comparative Example 1

[0055] 1. Boron carbide is also prepared based on the carbon thermal reduction method, with 95% boric acid, 24% petroleum coke, 1.2% carbon black and 1% graphite;

[0056] 2. Mix petroleum coke, boric acid and other raw materials and put them into the furnace to react at high temperature.

[0057] 3. The operating voltage in the furnace is 100V, the power is supplied intermittently, and the interval between feeding in the furnace is 4 hours. The electrode rising rate is in the range of 1cm to 5cm / s;

[0058] 4. Out of the oven: the crystal blocks are placed outdoors after being taken out of the oven, and the outdoor temperature is used to cool the crystal blocks. Through the above processing steps, the chemical index contents are shown in Table 4 below, and each numerical unit is a percentage:

[0059]

[0060] Table 4

[0061] From the comparative example (existing technology) and the three embodiments, it can be seen that the carbon content of the method disclosed in the present application is reduced, the total boron content is increased, and the purity of boron carbide is improved.

Claims

1. A graphite-free boron carbide smelting production method, based on the carbon thermal reduction method to prepare boron carbide, including raw material preparation, raw material mixing, furnace loading, heating, reduction reaction, heat preservation, cooling, Features: S1. Raw material ratio and particle size distribution in raw material preparation step: S1.1 Boric acid, petroleum coke and carbon black are mixed in the following weight ratios: boric acid 90-100, petroleum coke 24-26, carbon black 1.8-2.2; S1.2 grade the petroleum coke; The charging method in the S2 furnace charging step is: S2.1 Push the hot material into the furnace core, add the cold material around the furnace core, and compact the material; The smelting charging and power supply method in the S3 heating step is: S3.1 increases the operating voltage from 100V to 150V; S2.2 The interval between each feeding is shortened from 4 hours to 2.5 hours, and the original intermittent power supply is adjusted to continuous power supply; S3.3 Reduce the adjustment rate of electrode lifting and lowering, and adjust the lifting and lowering speed of the inverter to 1mm / s~5mm / s; The operation mode of S4 insulation and cooling is as follows: S4.1 The crystal blocks after being taken out of the furnace are pushed into the cooling chamber, and the time for the temperature in the furnace to drop to room temperature is adjusted to 96-120 hours.

2. The method for smelting and producing graphite-free boron carbide according to claim 1, It is characterized in that The particle size distribution in step S1.2) is as follows: 0.6 mm to 1 mm is 60% to 63%, 0.1 mm to 0.6 mm is 27% to 32%, and 0 mm to 0.1 mm is 8% to 11%.

3. The method for smelting and producing graphite-free boron carbide according to claim 1, Features: The particle size range of carbon black is 0.01mm to 0.05mm.

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