KR20010081258A - Manufacturing method of near-net-shaped reaction-bonded silicon carbide - Google Patents

Abstract

PURPOSE: A reaction bonding silicon carbide with a complete pattern is provided to improve handling strength of molding and to manufacture a complex pattern with easiness at a low cost. CONSTITUTION: A method for manufacturing a reaction bonding silicon carbide with a complete pattern is comprised of the steps of: preparing a slurry by uniformly mixing silicon carbide powder, a thermohardening resin, and a thermoplastic resin; forming a molding by injecting the slurry to an intended mold and heating to harden the slurry; removing the thermoplastic resin by heating the molding; carbonizing the thermohardening resin by heating the molding; and spreading a melting metal silicon into the carbonized molding.

Description

MANUFACTURING METHOD OF NEAR-NET-SHAPED REACTION-BONDED SILICON CARBIDE}

The present invention relates to a process for producing a solid reaction-bonded silicon carbide.

Reaction-bonded silicon carbide penetrates molten silicon into a molded body made of silicon carbide and carbon, and new silicon carbide formed by the reaction of molten silicon and carbon joins the silicon carbide particles that originally constituted the molded body, and the pores therebetween. It is filling material. Reaction-sintered silicon carbide is widely used in high temperature and corrosive atmospheres such as mechanical seals and nozzles because of its excellent wear resistance, erosion resistance, heat resistance, and high thermal conductivity.

For commercial applications of reactive bonded silicon carbide, real-world molding processes such as injection molding and hydrostatic pressure molding are required.However, these molding methods mainly use thermoplastic resins as binders. There is a disadvantage of difficult handling. In addition, in order to perform hydrostatic molding or injection molding, expensive equipment is required for mixing, granulating, molding and the like.

Accordingly, the present invention is to provide a method for producing a high strength, real-shaped reaction-bonded silicon carbide product without expensive molding apparatus.

1 is a photograph showing an example of a silicon carbide component produced by the present invention.

2 is a photograph showing another example of a silicon carbide component manufactured by the present invention.

The present invention provides a slurry by uniformly mixing silicon carbide powder, a thermosetting resin, a thermoplastic resin, a curing agent and a surface active agent, injecting the slurry into a mold of a desired shape and heat-cured to form a molded body, and heating the molded body to thermoplastic The present invention provides a method for producing a solid-state reaction-bonded silicon carbide comprising degreasing a resin, heating the molded body to carbonize a thermosetting resin, and infiltrating molten metal silicon into the molded body at a high temperature.

Since the present invention uses a method of injecting and curing the slurry into the mold and injecting the same as the injection molding, there is no need for a molding apparatus other than a mixing apparatus. It is also possible to manufacture large-scale parts in the shape of a thread.

The present invention has the following features. The molded object can be manufactured in a real form by the curing reaction with a thermosetting resin. In addition, by adjusting the mixing ratio of the thermosetting resin and the thermoplastic resin, it is possible to secure the three-dimensional connecting pore channel in the molded body by removing the thermoplastic resin in the first stage hot degreasing, thereby effectively removing the generated gas generated in the subsequent pyrolysis degreasing of the second stage thermosetting resin. It can be removed to prevent degreasing defects. In addition, the highly reactive carbon formed by the carbonization process may reduce and decompose the surface oxide of the silicon carbide powder in an elevated temperature process to improve the wettability of the molten metal silicon on the surface of the silicon carbide powder to obtain a dense reaction-bonded silicon carbide.

Referring to the method of manufacturing the reaction-bonded silicon carbide according to the present invention in more detail.

First, the silicon carbide powder, the thermosetting resin, the thermoplastic resin, the curing agent, and the surface active agent are mixed uniformly. The silicon carbide raw material powder of appropriate size is basis weighted at an appropriate fraction and mixed with the resin composition at low temperature. The particle size of the silicon carbide powder may vary depending on the use temperature or the end use, but in general, an average particle diameter of 3 μm or more is sufficient, and in a part requiring most heat resistance, a range of 3 to 500 μm is preferable. In the present invention, the average particle diameter of silicon carbide is in the range of 3 to 2000 µm. In addition, the silicon carbide powder preferably has a weight ratio of 60 to 90% of the mixture.

The resin composition adds a curing agent and a surfactant to the precursor solution of the thermosetting resin and the thermoplastic resin. The thermosetting resin determines the strength of the shaped body and provides the raw material of carbon used for reaction sintering.The thermoplastic resin moves to the surface through the capillary of the shaped body and evaporates at a temperature lower than the thermal decomposition temperature of the thermosetting resin, resulting in the subsequent pyrolysis process. It serves to secure the gas discharge passage. Since the pore structure at the time of reaching the pyrolysis process may vary according to the fraction of the thermosetting resin and the thermoplastic resin, the thermoplastic resin is preferably not more than 40% and not more than 70% of the total resin amount. Since the curing agent determines the curing rate, it needs to be appropriately adjusted according to the heat transfer or curing temperature of the mold. In order to prevent polymerization of the thermosetting resin precursor, the mixing process is preferably performed while maintaining a low temperature of 5 ° C. or lower, and if necessary, the mixture is defoamed under vacuum.

Then, the mixture is poured into a mold and heat-cured at 40 to 150 ° C. to prepare a molded body. The mixture is filled into a mold of a desired shape made of metal, plastic, glass, or the like, and the mold is heated to induce curing of the thermosetting resin precursor. Although it changes with the thickness of a molded object, it is preferable to perform heat hardening over 1 to 12 hours.

Next, a primary degreasing step is performed to remove the thermoplastic resin by heating the molded body to 150 ~ 250 ℃. The thermoplastic resin in the resin component of the molded body is removed by capillary movement and surface evaporation. In this process, the molded article is changed into a connected pore structure. In the subsequent pyrolysis degreasing process, it is preferable to add a thermoplastic resin to about 40 to 70% of the total resin in order to suppress defects such as cracking, warping, and bending of the molded article.

Next, a secondary degreasing step is performed in which the molded body is heated to 300 to 1200 ° C. in a vacuum or inert atmosphere to carbonize the thermosetting resin while pyrolyzing. After the first degreasing, if the temperature is continuously raised, thermal decomposition of the thermosetting resin of the molded body is completed at about 400 to 500 ° C., and at higher temperatures, sintering of pyrolytic carbon proceeds to increase the strength of the specimen. The actual sintering of carbon is almost complete at 1200 ° C or below.

In the next step, the carbonized shaped body is infiltrated with molten metal silicon at 1410 占 폚 or higher in a vacuum or reducing atmosphere. In this process, the reaction between the carbon in the molded body and the infiltrated molten silicon occurs to produce silicon carbide, and the remaining pores in the molded body are filled with molten silicon. When this is cooled, the final molded product is a reaction bonded silicon carbide composed of silicon carbide and silicon. At this time, the amount of residual silicon has a great influence on the properties of the reaction-bonded silicon carbide, so it is necessary to optimize the fraction of the silicon carbide powder in the initial mixture. As the fraction of silicon carbide is higher, the fraction of residual silicon decreases. Therefore, in order to maximize the fraction of silicon carbide while maintaining proper fluidity, it is preferable to use a mixture of powders having different particle diameters.

1 and 2 show examples of silicon carbide parts produced by the present invention. 1 shows a 12 inch spiral molded body after removing the resin components, and FIG. 2 shows a 4 inch molded body polished after sintering.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the present invention is not limited in scope by these examples.

The particle size of the silicon carbide powder used in the present Example for preparing the reaction-bonded silicon carbide parts was 5 ~ 210㎛, was used a single size of powder or a mixture of two or more silicon carbide powder. The thermosetting resin was used furfuryl alcohol (furfuryl alcohol), furfuryl alcohol resin (furfuryl alcohol resin), the weight ratio of the two components was 50/50. Glycol was used as the thermoplastic resin, and the weight ratio of the thermosetting resin and the thermoplastic resin is in the range of 70:30 to 40:60 based on 50/50. When the fraction of the thermosetting resin is more than 70%, the curing proceeds rapidly and it is difficult to remove the curing rate, and when the fraction of the thermoplastic resin is 60% or more, the curing rate becomes too slow. Xylene sulfonic acid and p-toluene sulfonic acid were used as a curing agent. Trition X-100 (Union Carbide, USA) is added as a surface active agent for uniform mixing of the liquid resin, and butyl alcohol is added as a mixing aid to improve the wettability of powder and liquid resin and to facilitate defoaming during mixing. It was. Tables 1 and 2 show the compositions of silicon carbide and liquid resin.

Composition (wt%) of silicon carbide powder Turned silicon composition Powder Average Particle Size (㎛) 210 150 100 65 45 35 25 16 10 5 One 10 40 35 15 2 25 50 25 3 80 20 4 78 22 5 15.6 10.4 8.3 7.3 7.3 7.3 6.3 37.5 6 100 7 100

Composition of Resin (wt%) Furtherance Thermoplastic resin Thermosetting resin Surface active agent Mixing aids Hardener One 50.6 32.8 10.1 6.5 2 37.9 45.4 7.6 9.1 3 30.3 45.4 7.6 7.6 9.1 4 25.9 44.4 7.5 11.1 11.1 5 21.9 61.4 4.4 12.3

Example 1

150㎛ silicon carbide powder 19wt%, 35㎛ silicon carbide powder 38wt%, 5㎛ silicon carbide powder 19wt%, ethylene glycol 7.4wt%, Triton X-100 1.8wt%, butyl alcohol 1.8wt%, perfuryl alcohol 5.4wt% , A mixture of perfuryl alcohol resin 5.4 wt%, a curing agent 2.2 wt% was prepared. Defoaming in vacuum for 30 to 60 minutes to remove bubbles in the powder and resin mixture. The powder mixture obtained above was poured into a mold and molded and subjected to initial curing at 50 ° C. Stepwise, the temperature was raised to 70 ° C, maintained at 70 ° C, the liquid resin was cured, and naturally cooled to demold. The liquid phase produced by the phase separation during the curing process was maintained at 150 ℃ to remove (primary degreasing). In order to completely degrease the residual liquid phase and produce carbon, the molded body after primary degreasing was heat-treated at 300 to 1000 ° C. for 1 hour in an argon atmosphere. The carbonized molded body was heated to a temperature of 1410 ° C. or higher in a vacuum or reducing atmosphere, and then maintained for 5 to 120 minutes to infiltrate molten silicon to prepare a sintered body.

Example 2

35㎛ silicon carbide powder 59.3wt%, 5㎛ silicon carbide powder 16.7wt%, diethylene glycol 9.2wt%, X-100 1.8wt%, furfuryl alcohol 5.4wt%, furfuryl alcohol resin 5.4wt%, hardener 2.2wt A mixture consisting of% was prepared. A sintered body was manufactured in the same manner as in Example 1.

According to the present invention, it is possible to economically manufacture a reaction-bonded silicon carbide product having a complicated shape. In particular, it has a high handling strength of the molded product throughout the process, and does not require expensive injection molding machine or hydrostatic pressure molding device to manufacture complex shape, and manufactures complete solid reaction bonded silicon carbide products without the need for processing equipment for shape processing. can do.

Claims (15)

The slurry is made by uniformly mixing silicon carbide powder, thermosetting resin and thermoplastic resin, The slurry is poured into a mold of a desired shape and heat cured to form a molded body, Heating the molded body to degrease the thermoplastic resin, Heating the molded body to carbonize the thermosetting resin, A real-shaped reaction bonded silicon carbide production method comprising penetrating molten metal silicon into the carbonized molded body. The method of claim 1, wherein the average particle diameter of the silicon carbide powder is in the range of 3 to 2000㎛, the weight ratio of the slurry is 60 to 90% range of the solid-state reaction-bonded silicon carbide manufacturing method. The method of claim 1, wherein the thermosetting resin is furfuryl alcohol and furfuryl alcohol resin. The method of claim 1, wherein the thermoplastic resin uses glycol. The method of claim 1, wherein the slurry is further mixed with a curing agent. The method of claim 5, wherein the curing agent is xylene sulfonic acid (xylene sulfonic acid), p-toluene sulfonic acid (p-toluene sulfonic acid) using a real-shaped reaction-bonded silicon carbide production method. The method of claim 1, wherein the slurry is further mixed with Triton X-100 as a surface active agent. The method according to claim 1, wherein butanol is used as a mixing aid in the slurry. The method of claim 1, wherein the fraction of the thermoplastic resin in the slurry ranges from 40 to 70%. The method of claim 1, wherein the weight ratio of the thermosetting resin and the thermoplastic resin of the slurry ranges from 70:30 to 40:60. The method of claim 1, wherein each component of the slurry is mixed while maintaining a low temperature of 5 ℃ or less. The method of claim 1, wherein the forming step is performed at a temperature of 40 to 150 ° C. for 1 to 12 hours. The method of claim 1, wherein the degreasing step is performed at a temperature of 150 to 250 ° C. 3. The method of claim 1, wherein the carbonization is performed by heating to a temperature of 400 ° C. or higher in a vacuum or inert atmosphere. The method of claim 1, wherein the step of infiltrating the molten metal silicon into the carbonized molded body is performed in a range of 1410 to 1650 ° C. for 5 to 120 minutes in a vacuum or reducing atmosphere.