Process Analysis of Boron Carbide Bulletproof Ceramic Inserts

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SIMUWU company serves the production of pressureless sintering process and reaction sintering process of silicon carbide, boron carbide and other ceramic products, and provides vacuum furnaces and supporting equipment for related production enterprises to meet their process needs. This paper introduces a production process of boron carbide ceramics.

The core component of the ceramic matrix composite bulletproof material is bulletproof ceramics. Among the various bulletproof ceramics currently available, boron carbide and (b4c) ceramics have the lightest specific gravity, the highest hardness and elastic modulus. The hardest material other than boron nitride, it is the preferred ballistic ceramic material for modern lightweight ballistic materials. The melting point of b4c is as high as 2350 °C, the plasticity is poor, and the grain boundary movement resistance is very large, so the preparation of b4c ceramics is relatively difficult. At present, the preparation of b4c ceramics mainly includes three processes: hot pressing sintering, pressureless sintering, and reaction sintering. Hot pressing sintering requires Fine powder with particle size ≤ 3.5 microns, and the process cost is extremely high, pressureless sintering requires ultra-fine powder with particle size ≤ 1 micron, high sintering temperature, large product shrinkage, unsuitable dimensional accuracy control, low reaction sintering temperature, net size sintering, etc. Advantages and good application prospects. At present, the reaction sintering b4c process adopts the vacuum silicon infiltration method. During the production process of this process, the solid phase of boron carbide is greatly lost due to the reaction of liquid silicon, which weakens the advantages of boron carbide materials.

Crafting process:

This article lists a bulletproof insert plate based on boron carbide bulletproof ceramics. The bulletproof insert plate includes an impact surface, a back plate surface, and an interface. The impact surface is a boron carbide bulletproof ceramic. The preparation method of the boron carbide bulletproof ceramic includes the following steps:

Ball milling b4c powder and modified phenolic resin in a ball mill for 12-24 hours to form slurry;

b4c includes three particle size powder gradations, one b4c powder has an average particle size of 8-10 microns, and its mass accounts for 50% of the total mass of b4c; another b4c powder has an average particle size of 20-25 microns, and its mass accounts for 30% of the total mass of b4c. ; The average particle size of the third b4c powder is 2-4 microns, and the mass accounts for 20% of the total mass of b4c.

The weight ratio of b4c powder and modified phenolic resin is 10:1-15:1; the raw materials for ball milling also include pva, glycerol, peg, and anhydrous ethanol; the ball milling medium is silicon carbide balls.

2) Granulate the obtained slurry with a granulator, drive the peristaltic pump motor, and transport the slurry in the ball-milled slurry bucket to the spray disc at the top of the granulator through the pump, and the spray disc motor drives the system to drive The spray disk rotates, and the spray disk rotates at 300 rpm. The rotating spray disc disperses the slurry by centrifugal action, the blower blows the dispersed slurry into the water with ultrasonic device at the bottom through the tuyere, the ultrasonic frequency is 40-60khz, the particles are insoluble in water and settle to the bottom; The discharge port separates the particles and water; the obtained particles are dried to obtain granulated powder; the drying temperature is 110°C.

3) selecting a mold, and molding the granulated powder obtained above to obtain a green compact;

4) Then the compact is heated in a mesh belt furnace, the modified phenolic resin is decomposed and a coating carbon source is generated to obtain a green body; min.

5) Sintering in a vacuum sintering furnace with a vacuum degree of ≤10pa, pressing an appropriate amount of silicon particles into a silicon cake, placing the silicon cake on the upper layer of the green body, the silicon cake is melted during the heating process, penetrated into the pores of the green body, and The carbon is reacted to generate silicon carbide; the silicon cake and the green body are put into a vacuum sintering furnace, and the sintering temperature is set to 1580-1600° C.;

6) After the sintering is completed, use a grinding wheel to clean the residual silicon on the surface of the product.

Related examples:

Example 1

1) Ball milling b4c powder and modified phenolic resin in a ball mill for 12 hours to form a slurry; the raw material formula for ball milling is 900 g of b4c mass, 80 g of modified phenolic resin, 5 g of pva, 4 g of glycerol, 2 g of peg, 1000 g of anhydrous ethanol, and b4c is composed of The powders of three particle sizes are graded, and the ball milling medium is silicon carbide balls. The weight ratio of the silicon carbide balls to the above-mentioned raw material formula is 1:2, and the average particle size of the b4c powder is 8-10 microns, and the mass accounts for the total mass of the b4c. 50%; another kind of b4c powder has an average particle size of 20-25 microns, and its mass accounts for 30% of the total mass of b4c; the third type of b4c powder has an average particle size of 2-4 microns, and its mass accounts for 20% of the total mass of b4c.

2) Use a granulator for granulation. The specific structure of the granulator includes a slurry barrel, a peristaltic pump motor, a peristaltic pump, a spray disc, a spray disc motor, a granulator barrel, an ultrasonic device, a discharge port, and the slurry barrel. It is communicated with the peristaltic pump, the peristaltic pump is communicated with the spray disc, the spray disc is communicated with the barrel of the granulator, the barrel of the granulator is communicated with the ultrasonic device, and the spray plate is provided with a tuyere, wherein the tuyere can be A through hole opened around the central axis of the spray disc. The tuyere is connected with the blower, and deionized water is passed into the ultrasonic device.

The concrete working steps of the granulator are: 1) the rotating speed of the spray disc 3 is set to 300 rpm, and the frequency of the ultrasonic device is set to 40-60khz; the peristaltic pump motor is driven, and the ball in the above step 1) is well ground. The slurry in the slurry tank is transported to the spray plate 3 at the top of the granulator through the peristaltic pump 2. The spray plate motor drive system drives the spray plate 3 to rotate, and the rotating spray plate 3 disperses the slurry through centrifugal action. The tuyere blows the dispersed slurry into the water with the ultrasonic device 6 at the bottom, and the particles are insoluble in water and settle to the bottom, so that the phenolic resin is well and evenly coated on the surface of the b4c; The discharge port 7 separates the particles and water, and the obtained particles are dried, and the drying temperature is 110 ° C, and the granulated powder is obtained after drying.

3) selecting a mold, molding the granulated powder obtained above to obtain a green compact,

4) Then the compact is heated in a mesh belt furnace, the resin is decomposed and a coating carbon source is generated to obtain a green body.

5) After sintering in a vacuum sintering furnace, the vacuum degree is less than or equal to 10pa, pressing an appropriate amount of silicon particles into a silicon cake, placing the silicon cake on the upper layer of the blank, and the ratio of the weight of the silicon cake to the weight of the blank is 1.2:1; the vacuum sintering temperature Set at 1580-1600°C; heat preservation and pressure for 30 minutes, the silicon cake melts during the heating process, penetrates into the pores of the green body, and reacts with carbon to form silicon carbide.

6) After the sintering is completed, use a grinding wheel to clean the residual silicon on the surface of the product

The properties of the final product are: density 2.64-2.67g/cm3, microhardness 2900-3100hv0.2, flexural strength 450mpa, fracture toughness 4.5mpa·m1/2. Wherein the bulletproof ceramic comprises the following components by mass percentage: b4c50-60%; sic25-30%; si15-25%.

Example 2

Example 2 By replacing the ratio of the ball milling formula in step 1) of Example 1, such as changing the mass of b4c to 1200g or 800g, modified phenolic resin 80g, and other qualities are equal to those of Example 1, the results show that the flexural strength of the obtained product is all uniform. ≥450mpa, fracture toughness ≥4.5mpa·m1/2.

Implementation 3

The traditional boron carbide process is used to obtain boron carbide bulletproof ceramics. The only difference between the traditional process flow and the process flow of Example 1 is that the granulation method is different; it is difficult for the traditional granulator to uniformly coat the phenolic resin on the boron carbide ceramics. surface, so as to obtain granulated powder with uniform distribution of carbon.

The results show that the sintered microhardness, flexural strength and fracture toughness of the bulletproof ceramic obtained in Example 1 are increased by 18%, 33% and 35%, respectively, compared with the bulletproof ceramic obtained in Example 2.

Example 4

According to the process flow of Example 1, select a suitable mold to obtain a boron carbide bulletproof ceramic with a thickness of 5mm, and compound the 5mm boron carbide bulletproof ceramic prepared above with a 10kg/m2 ultra-high molecular weight polyethylene backplane, and the compounding method adopts an interface adhesive. , to get a bulletproof insert. Subsequently, the sample bulletproof insert plate obtained in Example 4 is subjected to a ballistic performance test:

Test environment: room temperature, temperature 23℃, humidity 40%rh;

Instruments and equipment mainly used for testing and testing: general standard measuring tools; ballistic testing system; electronic scales; firearms (type 95 5.8mm automatic rifle); ammunition (type 87 5.8mm ordinary bullets);

Under normal temperature conditions, the firing distance is 10m and the firing angle is 0°. The 95-type 5.8mm automatic rifle and the 87-type 5.8mm ordinary projectile are used for 3 effective projectiles, and none of them penetrates. The maximum dent depth of the backing material is 22.4mm. The detailed data are shown in Table 1; in addition, as shown in Figure 2 and Figure 3, the bulletproof insert provided by the present invention will crack and grind the bullet when the bullet-proof insert plate is impacted by the bullet, and the back plate fiber will be stretched, broken and other forms to further absorb The kinetic energy of a bullet, thereby protecting a person or equipment.

Picture of the product:

Recommended related equipment:

The RVS-S series vacuum sintering furnace produced by SIMUWU can effectively meet the above process requirements. The product features are good vacuum atmosphere, accurate temperature control, good temperature uniformity, and various models. Products of different specifications, including vertical and horizontal, support customization.