KR20110107959A - High Density Boron Carbide Sintered Body and Manufacturing Method Thereof - Google Patents

Abstract

The present invention comprises the steps of molding the boron carbide powder into a mold provided in the furnace and applying pressure to form a molded body of a desired shape, operating a pump to exhaust the impurity gas present in the furnace, and reducing gas (H ₂ ). Supplying a gas, increasing the temperature of the furnace to a temperature higher than a temperature at which the boron oxide (B ₂ O ₃ ) present on the surface of the boron carbide powder volatilizes, and increasing the temperature of the furnace to boron oxide Secondly raising to a sintering temperature higher than the volatilized temperature and lower than the melting temperature of boron carbide, and carbonizing in a hydrogen gas (H ₂ ) gas atmosphere which is a reducing gas atmosphere while applying pressure to the molded body of boron carbide powder at the sintering temperature. Method for producing a high density boron carbide sintered body comprising the step of sintering boron and cooling the furnace to obtain a boron carbide sintered body It relates to a high-density carbon boron sintered body produced by the year.

Description

High density boron carbide sintered body and manufacturing method of the same

The present invention relates to a boron carbide (B ₄ C) sintered body and a method for manufacturing the same, and more particularly, high-density carbonization used as an abrasive material or a cutting tool material exhibiting properties such as high hardness, abrasion resistance, grinding resistance, and neutron absorption A method for producing a boron sintered body and a high density boron carbide sintered body produced thereby.

Boron carbide (B ₄ C) is the third-hardest material after diamond and boron nitride cubes, and is applied to various fields in the form of powder or sintered body due to its properties such as high hardness, abrasion resistance, grinding resistance, and neutron absorption. have. Boron carbide powder is used for polishing glass, light metals or artificial minerals, and since the sintered body has a very high wear resistance, sand blasting nozzle, computer disk, grinding motor, sliding friction It is mainly used for sliding friction parts, bearing liners, protective clothing, fire-resistant antioxidants and anti-wear agents. Boron carbide (B ₄ C) is also used as a nuclear shield due to its high neutron absorption per unit area.

Boron carbide (B ₄ C) is there is a high melting point and hardly used as the abrasive material or the cutting tool material is used as a covalent bond substance, such a boron carbide (B ₄ C) is generally a carbon (C), Y ₂ O sintering of the powder _{3, SiC, Al 2 O 3} , TiB 2, AlF 3, W 2 has a sintering aid such as B ₅ are used. However, such a sintering aid is known to form a secondary phase, and the secondary phase formed by sintering with the addition of the sintering aid adversely affects the physical properties of boron carbide (B ₄ C). It is well known that the hardness and mechanical properties of boron carbide decrease rapidly as the content of the secondary phase formed by the sintering aid increases. For example, inde boron carbide (B ₄ C) is a well-known carbon (C) as a sintering aid for, the use of carbon as a sintering aid to obtain a carbon-boron (B ₄ C) having a high relative density, but the boron / carbon solid solution Excessive or less than the bonding ratio (about 20 mol% of carbon content in boron carbide) of may lower the mechanical properties of boron carbide. Therefore, there is research on the method without the addition of a sintering aid to obtain a boron carbide (B ₄ C) sintered body made recently.

It is also known that boron oxide (B ₂ O ₃ ) is formed on the surface of boron carbide (B ₄ C). Boron oxide (B ₂ O ₃ ) present on the surface of boron carbide (B ₄ C) causes pores or voids to form between crystal grains during sintering. Pores or voids formed between the grains by boron oxide (B ₂ O ₃ ) may interfere with crystal growth and degrade the mechanical properties of the boron carbide (B ₄ C) sintered body. Works. Therefore, there is a need for a method of effectively removing boron oxide (B ₂ O ₃ ) from boron carbide (B ₄ C) which adversely affects the physical properties of the boron carbide (B ₄ C) sintered body.

The present invention has been made to solve the above problems, an object of the present invention is not only the secondary phase is formed by sintering without adding a sintering aid but also sintered in a reducing gas atmosphere to boron carbide (B ₄ C) Since boron oxide (B ₂ O ₃ ) present on the surface is reduced and decomposed, no pores or voids are formed between the crystal grains, so the crystal state is excellent, and the mechanical properties of the sintered body are excellent. The present invention provides a method for producing a high density boron carbide sintered body having a very high spacing and a high density boron carbide sintered body produced thereby.

The present invention comprises the steps of (a) placing the boron carbide powder into a mold provided in the furnace and applying pressure to form a molded body of a desired shape, (b) operating a pump to exhaust the impurity gas present in the furnace, and reducing agent gas. Supplying phosphorus hydrogen (H ₂ ) gas; and (c) raising the temperature of the furnace to a temperature higher than the temperature at which the boron oxide (B ₂ O ₃ ) present on the surface of the boron carbide powder is volatilized And (d) secondly raising the temperature of the furnace to a sintering temperature higher than the temperature at which the boron oxide is volatilized and lower than the melting temperature of boron carbide, and (e) applying pressure to the formed body of boron carbide powder at the sintering temperature. of the furnace, and in step (f) includes a step to cool the furnace to obtain a sintered boron carbide, the (d) sintering the boron carbide in a reducing gas atmosphere of hydrogen (H ₂₎ gas atmosphere, and The rising rate is set lower than the temperature rising rate of the furnace in the step (c) and gradually raised to the target sintering temperature to minimize thermal stress on the boron carbide powder compact, and sintering in a reducing gas atmosphere It provides a method for producing a high density boron carbide sintered body, characterized in that the boron oxide (B ₂ O ₃ ) present on the surface of the powder is reduced and decomposed.

The temperature at which the boron oxide is volatilized is 1200 to 1400 ° C., and the temperature higher than the temperature at which the boron oxide (B ₂ O ₃ ) is volatilized is 1400 to 1600 ° C., and the rate of temperature rise of the furnace in step (c) is 5. The temperature rise rate of the furnace in the step (d) is preferably set in the range of 1 to 30 ° C / min.

The sintering temperature is 1800 ~ 2100 ℃, the sintering is preferably carried out for 10 minutes to 3 hours in consideration of the microstructure and particle size of the sintered body.

In the step (e), the pressure applied to the molded body of the boron carbide powder is in the range of 20 to 60 MPa, and it is preferable to perform the up and down bidirectional compression in the upper and lower portions of the mold.

The mold is preferably a mold made of a graphite material of the same material as the carbon component of boron carbide.

In addition, the present invention provides a high-density boron carbide sintered body of which the apparent density is greater than 90% of the theoretical density as the boron carbide sintered body manufactured using the method for producing the high-density boron carbide sintered body.

The boron carbide (B ₄ C) produced according to the present invention sintered body is the apparent density is more than 90% of the theoretical density, the distance between the particles is very dense and pore are not substantially form a high density boron carbide (B ₄ C) sintered body .

In addition, since it made of sintering without the addition of a sintering aid in the boron carbide (B ₄ C) sintered body has a second phase (secondary phase) is not formed, and thus a very good hardness and mechanical properties of boron carbide (B ₄ C) sintered body Do.

By sintering in a reducing gas atmosphere, boron oxide (B ₂ O ₃ ) present on the surface of boron carbide (B ₄ C) is reduced and decomposed, so that no pores or voids are formed between grains. The state is excellent, and the mechanical properties of the boron carbide (B ₄ C) sintered body are also excellent.

1 is a view illustrating a sintering process for forming a carbon boron (B ₄ C) sintered body according to a preferred embodiment of the present invention.
2 is a graph showing an X-ray diffraction (XRD) pattern of the boron carbide (B ₄ C) sintered body prepared in Example 4. FIG.
3 is a graph showing the relative density of the boron carbide (B ₄ C) sintered body prepared according to Examples 1 to 4 and Comparative Examples 1 to 4 according to the sintering temperature.
Figure 4 is a graph showing the average grain size (average grain size) according to the sintering temperature of the boron carbide (B ₄ C) sintered body prepared according to Examples 1 to 4 and Comparative Examples 1 to ₄ .
5 is a graph showing Vickers hardness according to the sintering temperature of the boron carbide (B ₄ C) sintered body prepared according to Examples 1 to 4 and Comparative Examples 1 to ₄ ;
Figure 6 is a graph showing the flexural strength (flexural strength) according to the sintering temperature of the boron carbide (B ₄ C) sintered body prepared according to Examples 1 to 4 and Comparative Examples 1 to ₄ .

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the following embodiments are provided to those skilled in the art to fully understand the present invention, and may be modified in various forms, and the scope of the present invention is limited to the embodiments described below. It doesn't happen.

The present invention uses a hot pressing sintering method to produce a high density boron carbide (B ₄ C) sintered body without adding a sintering aid.

The hot pressing sintering method is a method of sintering while applying a high pressure, and sintering is possible at a lower temperature than atmospheric pressure sintering, and the sintering time is shortened. It is difficult to sinter boron carbide (B ₄ C) at atmospheric pressure without a sintering aid, and in order to use atmospheric sintering, there is a disadvantage in that the temperature is raised to near the melting point of boron carbide (B ₄ C) at high temperature. In addition, the boron carbide (B ₄ C) sintered body sintered by atmospheric sintering has a low relative density and a problem in that mechanical properties are inferior as compared with the case of the hot-pressing sintering method. In addition, in the case of using atmospheric sintering, the temperature must be raised to near the melting point of boron carbide (B ₄ C), which causes high energy consumption and excessive thermal stress on the sintered specimen.

Therefore, in the present invention, by using the hot pressing sintering method, a high density boron carbide (B ₄ C) sintered body in which the spacing between particles is very dense and little pores can be produced can be produced.

Hereinafter, a method of manufacturing a high density boron carbide (B ₄ C) sintered body according to a preferred embodiment of the present invention will be described.

First, boron carbide (B ₄ C) powder is prepared. Since the particle size of the boron carbide (B ₄ C) powder affects the density, mechanical properties, etc. of the boron carbide (B ₄ C) sintered body, the particle diameter of the boron carbide (B ₄ C) powder is selected in consideration of this. Preferably, it is preferable to use spherical boron carbide (B ₄ C) powder having a particle diameter of 1 µm or less in consideration of the use of a high density boron carbide (B ₄ C) sintered body in an abrasive or cutting tool.

The boron carbide (B ₄ C) powder is sintered by hot pressing sintering. 1 is a view illustrating a sintering process for forming a carbon boron (B ₄ C) sintered body according to a preferred embodiment of the present invention. Hereinafter, the sintering process using the hot pressing sintering method will be described in detail.

Referring to Figure 1, boron carbide (B ₄ C) powder is put into a mold provided in the furnace (Furnace) by applying pressure to form a molded body of the desired shape. The mold may be provided in a cylinder or prismatic shape, and after charging boron carbide (B ₄ C) powder in the mold, the mold may be formed into a desired shape by performing bidirectional compression up or down on the upper and lower molds or by performing one-side compression. have. In this case, the pressure applied to the boron carbide (B ₄ C) powder (pressure compressed by the mold) is preferably about 20 to 60 MPa. If the pressurization pressure is too small, the boron carbide (B ₄ C) powder particles Since there are many voids, it is difficult to obtain a desired high-density carbon boron sintered body, and if the pressurization pressure is too large, further effects cannot be expected, and the manufacturing cost of equipment may be increased by adding a mold, a hydraulic device, etc. according to a high pressure. The mold is preferably made of graphite (graphite) material of the same material as the carbon (C) constituting the component of boron carbide (B ₄ C), in the case of using a mold made of a different material as impurities in the subsequent sintering process It may work.

A rotary pump (not shown) is operated to remove the impurity gas present in the furnace and to evacuate until it reaches a vacuum state (for example, about 1 × 10 ^{−1 to} 1 × 10 ⁻³ Torr).

Hydrogen (H ₂ ) gas, which is a reducing agent gas, is supplied into the furnace, and the temperature of the furnace is higher than the temperature (1200 to 1400 ° C.) at which the boron oxide (B ₂ O ₃ ) is volatilized and the target sintering temperature (1800 to 2100 ° C.) The temperature is raised to a lower temperature (eg, 1400-1600 ° C.) (T1 section in FIG. 1). The hydrogen gas is preferably supplied at a flow rate of about 0.1 to 10 ml / min. It is preferable that the temperature rise of the furnace is about 5 to 50 ° C / min. If the ramp-up speed of the furnace is too slow, it takes a long time and the productivity decreases, and the ramp-up speed of the furnace is too fast. It is preferable to increase the temperature of the furnace at a ramp-up rate in the above range because no dense sintering is achieved by rapid temperature rise. Boron oxide (B ₂ O ₃ ) present on the surface of the boron carbide (B ₄ C) is generally pyrolyzed and volatilized at a temperature of 1200 to 1400 ℃ or more, and thus boron oxide (B ₂ O) when the furnace temperature is 1400 ℃ or more ₃ ) pyrolysis starts to occur.

The furnace temperature is raised to a target sintering temperature of 1800-2100 ° C., which is lower than the melting temperature (2450 ° C.) of boron carbide (B ₄ C) (T2 section in FIG. 1). At this time, it is preferable that the rising temperature of the furnace is about 1 to 30 ° C / min. If the ramp-up speed of the furnace is too slow, it takes a long time and the productivity decreases, and the ramp-up speed of the furnace is too high. It is preferable to raise the temperature of the furnace at a ramp-up speed in the above range because it may adversely affect the characteristics of the sintered body by rapid temperature rise. It is preferable that the ramp-up rate in the T2 section of FIG. 1 is slower than the ramp-up rate in the T1 section of FIG. 1, which is gradually increased to the sintering temperature in the T2 section of FIG. 1 by boron carbide (B ₄ C) powder. This is to minimize the thermal stress on the molded body.

When the temperature of the furnace rises to the target sintering temperature, boron carbide (B ₄ C) is sintered for a predetermined time (for example, 10 minutes to 3 hours) (T3 section in FIG. 1). Since hydrogen (H ₂ ) gas, which is a reducing agent gas, is injected into the furnace, boron oxide (B ₂ O ₃ ) partially remaining on the surface of boron carbide (B ₄ C) is reduced as in Scheme 1 below. The reducing agent gas flows in an amount such that boron oxide (B ₂ O ₃ ) can be sufficiently reduced, for example, it is supplied at a flow rate of about 0.1 ~ 10ml / min. The boron oxide (B ₂ O ₃ ) is reduced by hydrogen (H ₂ ) gas, which is a reducing agent gas, as shown in Scheme 1 below.

Scheme 1

B ₂ O ₃ + 3H ₂ → 2B + 3H ₂ O

As shown in Scheme 1, while boron carbide (B ₄ C) is sintered, boron oxide (B ₂ O ₃ ) is reduced to boron (B). At this time, water vapor (H ₂ O) which is a reaction by-product generated by reduction of boron oxide (B ₂ O ₃ ) is evaporated. By sintering boron carbide (B ₄ C) in a reducing gas atmosphere, boron oxide (B ₂ O ₃ ) partially remaining on the surface of boron carbide (B ₄ C) may be reduced to be completely decomposed. Since boron oxide (B ₂ O ₃ ) present on the surface of boron carbide (B ₄ C) is completely removed during the sintering process, pores or voids are not formed between the grains, so the crystalline state is excellent and It is possible to produce a high density boron carbide sintered body having excellent mechanical properties and very close spacing between particles.

Sintering temperature is preferably about 1800 ~ 2100 ℃ in consideration of the diffusion of boron carbide (B ₄ C) particles, necking between the particles, etc. If the sintering temperature is too high, mechanical properties due to excessive grain growth If the sintering temperature is too low and the sintering temperature is too low, the sintered body may not be good due to incomplete sintering, and therefore, sintering at the sintering temperature in the above range is preferable. According to the sintering temperature, there are differences in the microstructure, particle size, etc. of the sintered body, because the surface diffusion is dominant when the sintering temperature is low, but the lattice diffusion and grain boundary diffusion are progressed when the sintering temperature is high. It is preferable that the sintering time is about 10 minutes to 3 hours when using a furnace for general heat treatment, but when the sintering time is too long, it is not only economical because it consumes a lot of energy and it is difficult to expect further sintering effects. When the size of the sintered body becomes large and the sintering time is small, the characteristics of the sintered body may be poor due to incomplete sintering. The pressure applied to the boron carbide (B ₄ C) powder compact during sintering is preferably about 20 to 60 MPa. If the pressurization pressure is too small, it is difficult to obtain a desired high-density carbon boron sintered body and the sintering process if the pressurization pressure is too large. Cracks and the like may occur in the sintered body after this completion.

After performing the sintering process, the furnace temperature is lowered to unload the boron carbide (B ₄ C) sintered body. When the temperature of the furnace is lowered to a temperature of about 800 to 1200 ° C., it is preferable to cut off the supply of hydrogen gas which is a reducing agent gas. The furnace cooling may be allowed to cool down in a natural state by turning off the furnace power source, or to set a temperature drop rate (eg, 10 ° C./min) arbitrarily.

The boron carbide (B ₄ C) sintered body manufactured according to the preferred embodiment of the present invention has an apparent density of 90% or more of the theoretical density, a very high density of boron carbide (B ₄ ) with a very small gap between particles, and little pores. C) It is a sintered compact.

In addition, since it made of sintering without the addition of a sintering aid in the boron carbide (B ₄ C) sintered body has a second phase (secondary phase) is not formed, and thus a very good hardness and mechanical properties of boron carbide (B ₄ C) sintered body Do.

Boron oxide (B ₂ O ₃ ) present on the surface of boron carbide (B ₄ C) is reduced during the sintering process so that no pores or voids are formed between the crystal grains, and thus the crystal state is excellent. The mechanical properties of the boron (B ₄ C) sintered body are also very good.

The invention is described in more detail with reference to the following examples, which do not limit the invention.

≪ Example 1 >

A boron carbide (B ₄ C) powder (product name C Grade) manufactured by Herman C Stark having an average particle diameter of 0.8 μm was prepared.

Table 1 below shows the characteristics of the boron carbide (B ₄ C) powder of Herman C. Stark.

Specific surface area 18㎡ / g
Particle size
D 90% of particle ≤ 3.0 μm
50% particle ≤ 0.8 μm
D 10% of particle ≤ 0.2 μm

Impurity levels


Up to 1.7 wt% oxygen (O)
Up to 0.7 wt% nitrogen (N)
0.05 wt% iron (Fe)
Up to 0.15wt% Silicon (Si)
0.05 wt% aluminum (Al)
Other impurities up to 0.5wt% Boron content 75.65wt% Carbon content 21.2 wt% B / C molar ratio of boron (B) and carbon (C) 3.7

The boron carbide (B ₄ C) powder was placed in a cylindrical mold provided in a furnace (Furnace) was formed into a molded body by applying the upper and lower bidirectional pressure from the upper and lower mold. At this time, the pressure compressed by the mold was about 40 MPa. The mold used a mold made of graphite (graphite).

In order to remove the impurity gas present in the furnace and create a vacuum state, the rotary pump was operated to exhaust the impurity gas, the rotary pump was stopped, and hydrogen (H ₂ ) gas, which was a reducing agent gas, was supplied into the furnace. The hydrogen (H ₂ ) gas was supplied at a flow rate of about 5 ml / min.

Power was supplied to a heating means (not shown) surrounding the circumference of the furnace to heat the furnace to raise the temperature of the furnace to 1500 ° C. At this time, the rising temperature of the furnace was about 20 ° C / min.

After raising the temperature of the furnace to 1500 ° C., the temperature of the furnace was raised to 1900 ° C., which was lower than the melting temperature (2450 ° C.) of boron carbide (B ₄ C). At this time, the rising temperature of the furnace was about 5 ° C / min.

After raising the temperature of the furnace to 1900 ° C., boron carbide (B ₄ C) was sintered for 1 hour. The pressure applied to the boron carbide (B ₄ C) powder compact during sintering was kept constant at about 40 MPa. During sintering, hydrogen (H ₂ ) gas was supplied at a flow rate of about 5 mL / min.

After performing the sintering process, the furnace temperature was lowered to unload the boron carbide (B ₄ C) sintered body. When the temperature of the furnace was decreased, the supply of hydrogen gas, which is a reducing agent gas, was cut off when the temperature reached about 1000 ° C. The furnace cooling shuts down the furnace power, allowing the furnace to cool in its natural state.

<Example 2>

A high-density boron carbide (B ₄ C) sintered body was produced in the same manner as in Example 1 except that the sintering temperature was set to 1950 ° C and sintered.

<Example 3>

A high-density boron carbide (B ₄ C) sintered body was produced in the same manner as in Example 1 except that the sintering temperature was set to 2000 ° C. and sintered.

<Example 4>

A high-density boron carbide (B ₄ C) sintered body was produced in the same manner as in Example 1 except that the sintering temperature was set to 2050 ° C and sintered.

Comparative Example 1

The same boron carbide (B ₄ C) powder used in Example 1 was prepared, and a molded body was made in the same manner using the same mold as in Example 1.

In order to remove the impurity gas present in the furnace and create a vacuum state, the rotary pump was operated to exhaust the impurity gas, the rotary pump was stopped, and argon (Ar) gas was supplied into the furnace. The argon (Ar) gas was supplied at a flow rate of about 5 ml / min.

Subsequent processes were carried out in the same manner as in Example 1, and during sintering, unlike Example 1, argon (Ar) gas was supplied at a flow rate of about 5 ml / min to prepare a boron carbide (B ₄ C) sintered body. When the furnace temperature was lowered, the supply of argon (Ar) gas was cut off when the temperature reached about 1000 ° C.

Comparative Example 2

A boron carbide (B ₄ C) sintered body was produced in the same manner as in Comparative Example 1 except that the sintering temperature was set to 1950 ° C and sintered.

Comparative Example 3

A boron carbide (B ₄ C) sintered body was produced in the same manner as in Comparative Example 1 except that the sintering temperature was set to 2000 ° C. and sintered.

<Comparative Example 4>

A boron carbide (B ₄ C) sintered body was produced in the same manner as in Comparative Example 1 except that the sintering temperature was set to 2050 ° C and sintered.

FIG. 2 is a graph showing an X-ray diffraction (hereinafter referred to as 'XRD') pattern of the boron carbide (B ₄ C) sintered body manufactured according to Example 4. FIG. In Figure 2 (a) is a XRD pattern of boron carbide (B ₄ C) powder used in Example 4, (b) is equal to the boron carbide (B ₄ C) powder used in Example 4 and Example 1 XRD pattern when the hydrogen (H ₂ ) gas is supplied and heat-treated for 1 hour at a temperature of 1200 ℃ in a reducing atmosphere, (c) is XRD of the boron carbide (B ₄ C) sintered body prepared according to Example 4 A graph showing a pattern.

2, the boron carbide (B ₄ C) powder, the boron oxide (B ₂ O ₃₎ boron carbide (B ₄ C), the boron oxide the surface of the powder by a peak appears in as shown in (a) (B ₂ O ₃₎ to check that it is present, (b) and (c), can be concluded that the boron oxide (b ₂ O ₃₎ a peak is not as boron oxide (b ₂ O ₃₎ is removed, not a.

3 is a graph showing the relative density of the boron carbide (B ₄ C) sintered body prepared according to Examples 1 to 4 and Comparative Examples 1 to 4 according to the sintering temperature. Relative density is measured using the Archimedes method. As shown in FIG. 3, when Examples 1 to 4 which sintered in a hydrogen gas atmosphere which is a reducing gas atmosphere to remove boron oxide (B ₂ O ₃ ) are sintered at the same sintering temperature, sintering was performed in an argon (Ar) gas atmosphere. It can be seen that the relative density is higher than that of Comparative Examples 1 to 4.

Figure 4 is a graph showing the average grain size (average grain size) according to the sintering temperature of the boron carbide (B ₄ C) sintered body prepared according to Examples 1 to 4 and Comparative Examples 1 to ₄ . As shown in FIG. 4, when Examples 1 to 4, which were sintered in a hydrogen gas atmosphere to remove boron oxide (B ₂ O ₃ ), were sintered in an argon (Ar) gas atmosphere, the Comparative Examples 1 to 4 that were sintered in an argon (Ar) gas atmosphere were used. It can be seen that the average particle size was smaller than that of 4.

5 is a graph showing Vickers hardness according to the sintering temperature of the boron carbide (B ₄ C) sintered body prepared according to Examples 1 to 4 and Comparative Examples 1 to ₄ ; As shown in FIG. 5, Examples 1 to 4, which were sintered in a hydrogen gas atmosphere to remove boron oxide (B ₂ O ₃ ), were sintered in an argon (Ar) gas atmosphere when the sintering temperatures were the same. It can be seen that Vickers hardness was higher than that of 4.

Figure 6 is a graph showing the flexural strength (flexural strength) according to the sintering temperature of the boron carbide (B ₄ C) sintered body prepared according to Examples 1 to 4 and Comparative Examples 1 to ₄ . As shown in FIG. 6, Examples 1 to 4, which were sintered in a hydrogen gas atmosphere to remove boron oxide (B ₂ O ₃ ), were sintered in an argon (Ar) gas atmosphere when the sintering temperatures were the same. It can be seen that the bending strength was higher than that of 4.

As mentioned above, although preferred embodiment of this invention was described in detail, this invention is not limited to the said embodiment, A various deformation | transformation by a person of ordinary skill in the art within the scope of the technical idea of this invention is carried out. This is possible.

Claims (6)

(a) placing the boron carbide powder into a mold provided in the furnace and applying pressure to form a molded body of a desired shape;
(b) operating the pump to exhaust the impurity gas present in the furnace and to supply hydrogen (H ₂ ) gas which is a reducing agent gas;
(c) first raising the temperature of the furnace to a temperature higher than the temperature at which the boron oxide (B ₂ O ₃ ) present on the surface of the boron carbide powder is volatilized;
(d) secondly raising the temperature of the furnace to a sintering temperature higher than the temperature at which the boron oxide is volatilized and lower than the melting temperature of boron carbide;
(e) sintering boron carbide in a hydrogen (H ₂ ) gas atmosphere, which is a reducing gas atmosphere while applying pressure to the molded body of boron carbide powder at the sintering temperature; And
(f) cooling the furnace to obtain a boron carbide sintered body,
In step (d), the temperature rising rate of the furnace is set to be lower than the temperature rising rate of the furnace in step (c), and gradually raised to a target sintering temperature, thereby minimizing thermal stress on the boron carbide powder compact. A method for producing a high density boron carbide sintered body characterized in that the boron oxide (B ₂ O ₃ ) present on the surface of the carbon boron powder is reduced and decomposed by sintering in a reducing gas atmosphere.
The method of claim 1, wherein the boron oxide (B ₂ O ₃ ) is volatilized at a temperature of 1200 to 1400 ° C, the temperature higher than the temperature at which the boron oxide (B ₂ O ₃ ) is volatilized is 1400 to 1600 ° C, In step (c), the temperature rising rate of the furnace is set in a range of 5 to 50 ° C./min, and in step (d), the temperature rising rate of the furnace is set in a range of 1 to 30 ° C./min. Method for producing a boron sintered body.
The method of claim 1, wherein the sintering temperature is 1800 ~ 2100 ℃, the sintering method of producing a high density boron carbide sintered body, characterized in that performed for 10 minutes to 3 hours in consideration of the microstructure and particle size of the sintered body.
The high-density boron carbide sintered body according to claim 1, wherein the pressure applied to the formed body of the boron carbide powder in the step (e) is in the range of 20 to 60 MPa, and the bi-directional compression is performed in the upper and lower portions of the mold. Manufacturing method.
The method of manufacturing a high density boron carbide sintered body according to claim 1, wherein the mold is made of a graphite material of the same material as the carbon component of boron carbide.
A high-density boron carbide sintered body produced by using the manufacturing method according to any one of claims 1 to 5, the apparent density of which is greater than 90% of the theoretical density.

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