KR102079363B1 - A manufacturing method for carbon heater - Google Patents

Abstract

The present invention relates to a manufacturing method for producing a carbon heater used in the field of heating apparatus such as an electric oven.
According to the present invention, a process for mixing a carbon composite composition; Extrusion process; Stabilization heat treatment process; Carbonization heat treatment process; By providing a method of manufacturing a carbon heater comprising a, it is possible to prevent the occurrence of dielectric breakdown and sparks and plasma in the carbon heater and to provide a carbon heater having a variety of mechanical and electrical properties.

Description

Manufacturing method of carbon heater {A MANUFACTURING METHOD FOR CARBON HEATER}

The present invention relates to a method for producing a carbon heater used as a heater for applying heat from the cooking device areas, such as an oven, to a method using a new carbon composite material composition for preparing a carbon heater.

Recently, an oven using a heater is widely used as a home or commercial cooking appliance.

1 is a perspective view showing the general structure of the oven 1, the oven 1 is provided to selectively open to which the food is placed for cooking cavity (2), the cavity (2) door (3 ) And a plurality of heaters 6 that heat the cavity 2.

In particular, the heater 6 is mounted at least one heater, wherein the heater (6) is covered by the cover 8 from the outside of the cavity. In addition, a magnetron (4) is mounted on the top surface outside of the cavity (2) in order to ensure that the electromagnetic wave heating method is applied. Electromagnetic waves generated by the magnetron 4 radiate electromagnetic waves into the interior space of the cavity 2 through a predetermined waveguide and a stirrer. Further, the sheath heater is mounted (Sheath heater, 5) if necessary, the upper side in the internal space of the cavity.

The heaters differ in operation depending on the material and the heating method of the heater. Among these heaters, a carbon heater generally used as the sheath heater 5 and the heater 6 heats food in the cavity 2 by a radiant heating method as a grill heater.

In the case of the carbon heater, in the prior art, a carbon fiber (Carbon fibers, CFs) were primarily used. In general, carbon fiber refers to a fiber-shaped carbon material of the carbon content is less than 90%.

Since carbon fiber is made of a material called 'carbon', it retains the microwave absorption characteristic of carbon itself. In addition, the carbon fiber also shall have a unique characteristic of not only the rain can be very large fiber length to the fiber diameter of the type essentially in the nature of 'fiber'.

This inherent property of carbon fiber creates some problems when using carbon fiber as a heating source of an oven.

First, as shown in Figure 2, the carbon fiber is made of each carbon filament. However, the filaments as well as the diameter of the filament - is approximately the distance between the filaments can ㎛. Thus, under high electromagnetic fields, high voltages are applied at very narrow distances (intervals) between the filaments. For example, when a voltage of 10 V is applied at intervals of 1 탆, a high voltage of about 107 V / m is applied between the filament and the filament. In this case, the filaments are highly prone to breakdown, and even sometimes the spark (Spark) occurs.

On the other hand, the carbon heater is an assembly consisting of a carbon fiber and a connector for applying electricity to the carbon fiber, a quartz tube including the carbon fiber and the connector therein, and an encapsulated gas such as Ar enclosed in the tube (or Unit). In addition, the encapsulation gas maintains a vacuum atmosphere of about 10 ⁻¹ to 10 ⁻² torr. However, as described above, when a high voltage is applied between the filament and the filament, although the breakdown or spark of the filaments does not occur, the plasma is generated due to the inert gas atmosphere under the high voltage.

It is conventional to install the shield (Shield) member between the carbon heater and the cabin to prevent the light caused by the reaction with the plasma such that the plasma goes to the cabin. However, because the shield member not only shields the plasma light blocking part even copying light emitted from the carbon heater, there is a problem that significantly decreases the radiation efficiency of the oven.

Therefore, a new type of carbon heater does not have a conventional fibrous required, method for manufacturing the new form of the carbon heater must also be developed.

Meanwhile, in the prior art with respect to the present invention, Korea Laid-Open Patent Publication No. 10-2011-0109697 (2011. 10. 06.) There is.

The present invention relates to a carbon heater, and an object thereof is to provide a new carbon heater under a high voltage that does not cause dielectric breakdown or spark, and plasma.

Another object of the present invention is to provide a new method for the production of new carbon heater.

In order to solve the above technical problems, according to an aspect of the invention, the step of mixing the carbon composite composition; Extrusion process; Stabilization heat treatment process; Carbonization heat treatment process; A method of manufacturing a carbon heater may be provided.

Preferably, the composition is a method of producing a carbon heater comprising a base material to determine the specific resistance of the resistance heating in a resin, a lubricant, and a high temperature as a binder.

Preferably, the composition is a method of producing a carbon heater comprising a base material and a resistivity modifier to determine the specific resistance of the resistance heating in a resin, a lubricant, and a high temperature as a binder.

In particular, the resin is a novolak (Novolac) a method for manufacturing a resin carbon heater.

In particular, the lubricant is a method of producing a carbon heater which is graphite.

In particular, the base material is a method of manufacturing a carbon heater which is silicon carbide (SiC).

In addition, the specific resistance controlling agent is a production method of a carbon heater silicon oxide (SiO2).

Preferably, the extrusion process is a method of producing a carbon heater is performed at a speed of 10 ~ 120 rpm at 100 ~ 180.

Preferably, the stabilization heat treatment process is a method of manufacturing a carbon heater that is performed for 10 minutes to 2 hours at 270 ~ 320 ℃.

Preferably, a method for manufacturing a carbon heater comprising a first carbonization heat treatment process that ahutga Singh (Out-gassing) in the carbonization heat treatment process is 600 ~ 1,000 ℃ for 10 minutes to 2 hours.

In particular, the carbonization heat treatment process is a method of manufacturing a carbon heater comprising a second and third carbonization heat treatment process.

Furthermore, the second carbonization heat treatment step is a manufacturing method of the carbon heater is carried out at 1,200 ~ 1,400 ℃ for 10 minutes ~ 4 hours and, performing the third carbonization heat treatment process at 1,500 ~ 1,700 ℃ for 10 minutes to 4 hours.

The carbon heater manufacturing method of the present invention, unlike the carbon heater using a conventional carbon fiber, it is possible to manufacture a carbon heater of the bulk (bulk) shape, not the fiber shape, between the filaments inherent disadvantages of carbon fiber There is no local voltage concentration in the circuit, which can prevent dielectric breakdown, sparks and plasma.

In addition, the carbon heater manufacturing method of the present invention, it is possible to produce a carbon heater in a variety of shapes, it is possible to easily produce a carbon heater having a desired shape required for the oven of different sizes and shapes.

In addition, the carbon heater manufacturing method of the present invention can provide a carbon heater having various mechanical and electrical properties by changing the composition and composition range of the raw material.

On the other hand, the carbon heater manufacturing method of the present invention, by controlling the carbonization heat treatment process even in the composition and composition range of the same raw material, it is possible to adjust the electrical characteristics of the carbon heater, greatly improving the degree of freedom of electrical design of the carbon heater.

1 is a perspective view showing a general structure of an electric oven.
2 is an enlarged view of carbon fiber.
Figure 3 is a flow chart schematically showing a manufacturing method for making a carbon heater using the carbon composite composition of the present invention.
Figure 4 is a DSC thermal analysis of the raw material of the noblock resin and silicon carbide.
5 is a microstructure photograph of the surface (a, c) and cross-section (b, d) of the carbon composite composition after extrusion (a, b) and after stabilization heat treatment (c, d), respectively, of the present invention.
Figure 6 is a cross-sectional microstructure of the carbon composite heating element performed only (a) the second carbonization heat treatment step observed with a scanning electron microscope (SEM) and (b) carbon performed to the third carbonization heat treatment process after the second carbonization heat treatment process A cross-sectional microstructure picture of the composite heating element.
Figure 7 is a surface (a) and cross-sectional (b) photograph of the carbon composites stabilized using the three-component carbon composite composition of Example 1 of the present invention.
8 is a photograph of the surface (a) and cross-section (b) of the carbon composite stabilized heat treatment using the four-component carbon composite composition of Example 2 of the present invention.
9 is a view illustrating a carbon heater product made of a heating element using the composition of the present invention.
10 is a photograph showing a heating operation state of the carbon heater produced using the four-component carbon composite composition of Example 2 of the present invention.
FIG. 11 illustrates an electrical resistance value of a carbon heater according to a third carbonization heat treatment process temperature produced using the four-component carbon composite composition of Example 3 of the present invention.
12 illustrates thermal conductivity characteristics of the carbon heater according to the third carbonization heat treatment process temperature.

Hereinafter, it will be described in detail with respect to the carbon heater produced by a method of producing a carbon heater and the method in accordance with a preferred embodiment of the present invention with reference to the accompanying drawings herein.

The present invention is not limited to the embodiments disclosed below, but can be implemented in various different forms, only this embodiment to complete the scope of the invention to those skilled in the art and complete the scope of the invention to those skilled in the art It is provided to inform you.

First, a description will be given of a method invented for the preparation of a carbon heater according to the present invention.

3 is a production method of a carbon heater invention In the present invention, (hereinafter referred to as carbon composite composition, the composition or raw materials) of a carbon composite composition raw material mixing process, an extrusion process, the stabilization heat treatment process, and carbonization heat treatment step of the Include.

First, the manufacturing method in the present invention starts from the step (S 100) of uniformly mixing the raw materials. In the method of mixing the raw materials, first, a raw material having a desired component and composition range is prepared, and then the raw materials are mixed for a sufficient time using a mill. Although the present invention, mixed for 2 hours using an attrition mill (Attrition Mill), is not limited thereto. May also be used even in the crusher, a ball mill (Ball mill), attrition mill, pinmil (Pin mill), as well as jet mill, vibration mill, colloid mill or the like.

Ingredients used in the present invention uses a carbon composite composition comprising a base material to determine the specific resistance of the resistance heating in a resin, a lubricant, and a high temperature as a binder.

In addition, the present invention may use a composite carbon material composition comprising a base material and a resistivity modifier to determine the specific resistance of the resistance heating in a resin, a lubricant, and a high temperature as a raw material as a binder.

First, the binder is a component added for mechanical bonding between the powders at a relatively low temperature, before the inorganic powders serving as heating elements of the carbon heater are bonded by diffusion at a high temperature. In addition, the binder according to the present invention performs its functions as a source of carbon in the main components of the carbon heater final product.

In the present invention, Novolac resin, which is a kind of phenol resin having excellent heat resistance, was used as one example of the binder. Novolak resin is one of phenol in the resin produced by the reaction of a phenol and formaldehyde Alte hydroxy, a phenol resin produced when the catalyst is in the catalyst acid (Acid). However, it not necessarily limited to phenolic resins, particularly novolak resins as a binder. Specifically, in addition to the noblock resin, a resol resin may also be used in the phenol resin. In addition to the phenol resin, all of the organic resins that can be used as a binder generally responsible for the adhesion function, such as an acrylic resin, are possible.

More specifically, the noblock resin is obtained by reacting with an acidic catalyst such as sulfuric acid, hydrochloric acid, hydroxyl acid, etc. with a compound molar ratio of formaldehyde to phenol of 0.5 to 1.0. Since the condensation reaction takes place rapidly under an acidic catalyst, since many phenol nuclei are connected by methylene groups, they are thermoplastic resins and have a property of not being cured without a curing agent. It is cured by condensation curing or thermosetting, and is usually heat cured by mixing with hexamine. However, as will described in more detail in the extrusion process, the novolak resin of the present invention was confirmed by the present inventors to have a beneficial effect does not require a curing agent in the extrusion process and stabilizing heat treatment step.

In the present invention, silicon carbide (SiC) is also included as a base material for determining the specific resistance of the heating element in the carbon heater which is the final product.

Silicon carbide has a low electrical resistivity than the first inorganic powder in the other component is characterized in that an electric conductivity and thermal conductivity is relatively high. The electrical properties of the base material are the basic properties that must be provided to be used as the heating element of the carbon heater. In addition, thermal conductivity is also important, because when the thermal conductivity is low, the operating temperature when used as a carbon heater rises to about 1,200 ° C., which is very high, so that heat dissipation around the heater may cause disconnection of the heater heating element.

In addition, the raw material of the carbon composite composition of the present invention contains graphite as a lubricant. The lubricant is to reduce the friction with the raw material and the die (Die) in order to extrude the raw material.

In general, the carbon electrode may include carbon, so is used, the lubricant of graphite (Graphite), a carbon black (Carbon Black) and activated carbon (Activated carbon) including carbon as a main ingredient is used as a main material.

On the other hand, in the present invention, in addition to the lubricant and graphite as a carbon source, another function of graphite was confirmed. As described above, the novolak resin used as a binder in the present invention may be known that cure by themselves. A process such as simply raising the temperature does not cure the noblock resin. Therefore, in order to cure the noblock resin, a separate curing agent (for example, a curing agent such as hexamine) must be included.

When using the resol (resol) resins from another by ten thousand and one phenolic resin binder, the additional curing agent is not necessary. Because, resole resin is that the heat curable without the need for a separate curing agent.

In addition, in the case of using another resin such as an acrylic resin as a binder, the binder may be cured using a curing agent or thermosetting or photocuring, if necessary. If using the photocuring and photoinitiator is also contain further, in addition can also contain various additives.

In the present invention, it is not known what mechanism yet, but when graphite is included in the carbon composite composition to which the curing agent of the present invention is not added, the carbon composite composition itself hardens without addition of a curing agent after the extrusion process. it was confirmed that progress. Therefore, carbon composite materials of the present invention may perform the graphite without a separate curing agent is required according to the type of the binder at the same time as function of a lubricant and a curing agent. Of course, when using the binder of other ingredients, depending on the composition of the binder is, there is also a case that the curing agent together with a binder must be contained in the carbon composite composition.

In addition, the carbon composite composition, which is a raw material of the present invention, may include a resistivity regulator for controlling the resistivity of the heating element in the carbon heater, which is the final product, if necessary.

The resistivity regulator serves to raise or lower the resistivity of the heating element of the carbon heater. However, in the present invention, silicon carbide having a relatively low resistivity is used as the base material, so a material capable of raising the resistivity is mainly used as the resistivity adjuster.

Typically, as a material having a high resistivity, oxides generated by phonon (referred to as Phonon or lattice vibration) instead of electrons are known. In the present invention, silicon oxide (SiO ₂ ) or aluminum oxide (Al ₂ O 3) was used as a resistivity regulator.

However, together the silicon oxide is a more preferable specific resistance adjusting agent than aluminum oxide prepared, which, because it easier to control the adjustment (increase) of specific resistance of the carbon heater at the time of carbonization heat treatment to the silicon oxide is low more, the melting point will be described later than the aluminum oxide to be.

Next, the manufacturing method in this invention goes through the process (S200) of extruding using a uniform raw material.

The extrusion process of the present invention is carried out at a temperature of 100 ~ 180 ℃ at a rate of 10 ~ 120rpm. If the extrusion temperature is lower than 100 ℃ high viscosity of the binder is difficult to bond with the ceramic powder, the mechanical stability of the extrudate after extrusion is lowered. On the other hand, since the extrusion temperature when higher than 180 ℃ the binder is reacted with the graphite beginning to the cured polymeric network that is formed is difficult to progress the extrusion over the extruded hard water.

Meanwhile, in the present invention, the injection process using the mold instead of the extrusion process can be applied.

The principle of the extrusion process is that the polymer is melted in the screw extruder, and the polymer component is melted and then moved forward along the screw channel and extruded through the die at the end of the extruder by the high pressure formed at the screw tip. Therefore, the extrusion process has the advantage that the productivity is very high, while the density and strength of the product, surface roughness or straightness, etc. has a worse characteristic than the injection process.

On the other hand, the injection process is flew polymer or melt polymer components of the raw material containing the polymer is transferred to a cylinder front side, at the end of the conveyance by pushing the polymer or polymer component melt feed forward to the screw or plunger through the nozzle of the cylinder end It utilizes a way that enters flow into the mold. Therefore, the injection process, compared to the extrusion process, the design of the shape is free according to the mold design, there is an advantage of excellent density, strength, surface roughness of the product.

Figure 4 is a DSC thermal analysis result showing the curing reaction that occurs when heating a raw material composed of one embodiment novolak resin and the silicon carbide of the present invention.

As seen in Figure 4, it can be seen that when the content of the resin increases in the raw material carbon composite composition, the curing reaction is initiated the temperature, peak temperature, and end temperature increase. Therefore, the upper limit of the extrusion temperature in this invention is determined by the near 180 ℃ curing start temperature of the resin used as a binder in the present invention.

According to the production method of the present invention, a stabilization heat treatment process (S 300) is performed after the extrusion process. Stabilization heat treatment step (S 300) is a heat treatment process for deriving a combined structure of the binder carbon and oxygen. The binder is hardened so that the result of the carbon composite material extruded from a composition of a stabilizing heat treatment step can ensure the mechanical stability to remain in the extruded shape.

Stabilization heat treatment process initially after the binder takes place the process temperature rises in accordance with the first viscosity is lowered ceramic densification (Densification) process to fill the void between powder, stabilization heat treatment process reviews, the curing reaction is completed, maintain the extruded shape stably Done.

5 is a microstructure photograph of the surface (a, c) and cross-section (b, d) of the carbon composite composition after extrusion (a, b) and after stabilization heat treatment (c, d), respectively.

Microstructure of the carbon composite material after extrusion has shown that the composition and the ceramic powder are coated with a binder resin, a relatively large gap between the binder resin powder well without filling. However, the cross-sectional microstructure is to show a slightly angled (Faceted) shape in a portion, which because they do not have the temperature in the mixing process or extrusion process, not the binder is sufficiently coated with some ceramic powders does not sufficiently high extent to the binder to flow to be.

On the contrary, it can be seen that the microstructure after the stabilization heat treatment is larger in unevenness on the surface than the microstructure after extrusion. In addition, cross-sectional microstructure shows that becomes more round (Round) in most areas, after stabilization heat treatment. This is because, as well as the curing reaction of the binder during the stabilization heat treatment process, as the viscosity of the binder decreases as the temperature increases, the binder is coated with a binder having increased fluidity. Due to this densification process, caused by the stabilizing heat treatment step, the fine shrink (Shrinkage) in the surface up generating fine unevenness on the surface, and the shape of particles in the cross-sectional microstructure is a curved surface than over the particles after the extrusion process have.

On the other hand, the stabilization heat treatment process in the present invention is carried out for 10 minutes to 2 hours at a temperature of 270 ~ 320 ℃ in the air. In particular, the lower limit of the process temperature is determined by the thermal properties of the binder, as shown in Figure 4 it can be seen that the crystallization completion temperature of the noblock resin of the binder in one embodiment of the present invention is about 270 ℃. Therefore, if the stabilizing annealing process is lower than 270 ℃ it is the curing of the binder can not be guaranteed. On the other hand, the upper limit of the stabilization heat treatment temperature is not technically limited, but in terms of energy, it is preferable not to raise the temperature too high.

Temperature rise rate of the heat treatment in the stabilization step is the 1 ~ 10 ℃ / min is preferred. In terms of microstructure, the slower the temperature rise rate is, the better, but the slower than 1 ° C / min, the microstructure after the stabilization heat treatment has a long process time without significant change, and as a result, the process time per unit process increases, resulting in a significant drop in productivity. On the other hand, if the temperature increase rate is faster than 10 ℃ / min, the reaction time is not enough, resulting in a phenomenon that the durability (defect) occurs in the final microstructure and the durability is poor.

Next, the cured carbon composite composition is subjected to a carbonization heat treatment process (S 400). The carbonization heat treatment process primarily out-gassing the volatile components among the components constituting the carbon composite composition, and then carbonizes most of the remaining components to form an active component of a carbon heater resistor as a final product. and that for the purpose. To this carbonization heat treatment process of the present invention comprises a first carbonization heat treatment step and the second carbonization heat treatment step.

Firstly, the first carbonization heat treatment step is a subsequent second carbonization heat treatment compared proceeds at a relatively low temperature is a temperature of 600 ~ 1,000 ℃ for 10 minutes to 2 hours, usually the binder components of the other components excluding the carbon in an inert gas atmosphere such as nitrogen And volatilize other components other than carbon which may be present in the components of the composition and the components contained in the components other than the binder.

After the first heat treatment step, the carbide of the second carbide heat treatment step is in progress. A second heat treatment step, carbonization sikimyeo carbide components of the washing step after ahutga remaining carbon composite composition, is carried out at a temperature of 1,200 ~ 1,400 ℃ under an inert gas atmosphere such as nitrogen for 10 minutes to 4 hours. When the temperature of the second carbonization heat treatment process is lower than 1,200 ° C., there is a problem that the carbonization of the components is incomplete and the electrical conductivity of the heating element of the carbon electrode is lowered. On the other hand, when the temperature of the second carbonization heat treatment process is higher than 1,400 ° C., excessive vaporization of the “-CC-” structure resulting from the binder material or the like occurs, causing a problem that the yield of the heating element of the carbon electrode is greatly reduced. do.

In addition, the carbonization heat treatment process is not divided into the first carbonization heat treatment process and the second carbonization heat treatment process to improve productivity, and may be operated as one carbonization heat treatment process. In this case, the adjustment of the other process conditions such as varying the rate of temperature rise to facilitate ahutga washing may also be parallel.

On the other hand, the inventors of the present invention, even using the same carbon composite composition, through the carbon heater manufacturing method of the present invention, it was confirmed that the electrical properties of the carbon heater as the final product can be changed.

In particular, under the conditions used in the carbon heater, to increase the electrical resistance heating element of the heater in the specification at a certain level is needed to reduce the amount of power used in the heater.

The present inventors have found that a fusion "-CC-" which oxidize or vaporize a part of the structure or specific resistance adjusting agent of silicon oxide (SiO2) resulting from the heat treatment after the oxidation process, and the binder material around the silicon carbide base material ( The melted silicon oxide was coated with silicon carbide, which is a base material, to reduce the cross-sectional area through which electrons can pass. This by reducing the time to collision of electrons with a shorter stroke moving average (Mean free path) of the electronic, electrical conductivity, heating of the heater was decreased and characters increases electrical resistance and.

For this purpose, the present inventors pay attention to the fact that the melting point (1,600 ° C) of silicon oxide is not higher than the melting point of other high-resistance metal oxides such as aluminum oxide (Al2O3, 2,072 ° C) or zirconium oxide (ZrO2, 2,715 ° C). and it was added to the third carbonization heat treatment process after the second carbonization heat treatment step.

The third carbonization heat treatment process are reduced and an increase in electrical resistivity of the electrical conductivity mentioned earlier, as well as thereby also significantly improving the mechanical strength of the heater heating conditions to be provided in the present invention. This is because some of the molten silicon oxide fills in voids or defects, particularly between ceramic powders present on the surface, to remove surface defects that are the major cause of brittle fracture in the ceramic material.

In addition, the third carbonization heat treatment process of the present invention causes a change in thermal conductivity of the carbon heater. This is due to the change of the component and microstructure in the composition for heater heating element due to the molten silicon oxide.

The third carbonization heat treatment process in the present invention is carried out for 10 minutes to 4 hours at a temperature of 1,500 ~ 1,700 ℃ under an inert gas atmosphere such as nitrogen.

If the temperature of the third carbonization heat treatment step is lower than 1,500 ° C, too much vaporization of the "-C-C-" structure resulting from the binder material or the like occurs, which causes a problem that the yield of the heat generating element of the carbon electrode is lowered. In addition, there is the main problem that more than three, if the temperature of carbonization heat treatment process is lower than 1,500 ℃ mothayeo not pass the high heat of the carbon electrode during the thermal conductivity of the carbon electrode is too low to heating around a result can lead to disconnection.

On the other hand, the third case where the temperature of carbonization heat treatment process is higher than 1,700 ℃, and the molten silicon oxide with the reaction of the "-C-C-" structures resulting from the binder material or the like is changed into silicon carbide. The result is reduced the proportion of the molten silicon oxide with silicon carbide and the coating resistivity is decreased.

FIG. 6 illustrates a microstructure of cross-sections of the carbon composite heating elements which are each subjected to only the second carbonization heat treatment process (a) or the second carbonization heat treatment process to the third carbonization heat treatment process (b), respectively, using a scanning electron microscope (SEM). to be.

The carbon composite heating element (a), which has been advanced only to the second carbonization heat treatment process, has a microstructure in which a "-C-C-" structure derived from a binder resin is surrounded around silicon carbide or silicon oxide having a size of 20 to 40 µm. And this "-CC-" For this reason, the bonding strength between the silicon carbide or silicon oxide is weaker than the bonding strength of the silicon carbide or silicon oxide itself, the surface of the silicon carbide or silicon oxide in the microstructure showing a fracture surface of the carbon composite material of the structure It was observed relatively smoothly.

On the other hand, the third carbon composite advanced to carbonization heat treatment process the heating element (b) is a part or a plurality of the silicon oxide is present in the coating around the silicon carbide surrounding or silicon carbide or silicon oxide is melted (Melting) "-CC - "it has the oxidized or vaporized microstructure. When the molten silicon oxide coats the silicon carbide around it, the bonding strength between the molten silicon oxide and the silicon carbide is much stronger than that between the conventional "-CC-" structure and silicon carbide or silicon oxide, as a result, the fusion-coated silicon oxide on the silicon carbide surface in the microstructure of the fracture surface of a carbon composite material is left in a fine shape, such as a residue (residue).

Therefore, it can be seen that these microstructure observation results agree very well with the expectation that the melting of the silicon oxide in the third carbonization heat treatment process will occur in the present invention.

Through the following various embodiments, the present invention will be described in more detail by way of example. The following examples are merely to illustrate the present invention more clearly, and the present invention is not limited to the examples.

Example  One

First, the silicon carbide (SiC), to prepare a novolak resin, and a three-component (Ternary) carbon composite material composition was added (hereinafter referred to as%) 74 wt.% Graphite, respectively, 23% and 3% as a lubricant as a binder.

The prepared three-component composition was uniformly mixed through a raw material mixing process using an abrasive grinding machine for 1 to 4 hours, then extruded at 120 ~ 160 ℃, a stabilization heat treatment process was performed at 280 ~ 300 ℃. Since were carried out ahutga Singh and carbonizing 800 ℃ and each for 1 hour, during the first carbonization heat treatment step and the second carbonization heat treatment process at a temperature of 1,400 ℃ to, a heating element to carbonization the heat-treated carbon composite material is machined to a final carbon heater electric to evaluate the property.

Figure 7 shows the surface and cross section of the three-component carbon composite after the stabilization heat treatment process. As shown in FIG. 7, it can be seen that the carbon composite of the three-component composition is very excellent in macroscopic mechanical stability and hardly any defects are observed on the surface. In addition, without the occurrence of cross-sectional microstructure segregation (Segregation) and aggregation (aggromeration), or macropores (Voids) in the carbon composite material, the silicon carbide can be seen that the very uniformly distributed by a binder.

After the carbon heater was fabricated using the three-component composition of Example 1, the electrical properties were evaluated. Electric resistance of the carbon heater at an applied voltage of 115V was measured to be about 4 ~ 5Ω.

Example  2

Among the inorganic powder component, 62% graphite, each as a novolak resin, and a lubricant as a specific resistance adjusting agent and a silicon carbide (SiC) as the default, as a binder, the inorganic powder, including further a silicon oxide (SiO2), 12%, 23%, and A quaternary carbon composite composition containing 3% was prepared.

Prepared also under the same conditions as in Example 1, 4-component composition, the first after a then uniformly mixed through the raw material mixing process, the extrusion was formed, since the stabilization heat treatment step and the first carbonization heat treatment process and the second carbonization heat treatment process, final Processed with a carbon heater to evaluate the electrical properties.

Figure 8 shows the surface and cross section of the four-component carbon composite after the stabilization heat treatment process. As shown in Figure 8, the carbon composite material into 4-component composition in Example 1, as in the carbon composite by the three-component composition at, few defects are not observed on the surface as well as the macroscopic mechanical stability to very good it can be seen to do. In addition, without the occurrence of cross-sectional microstructure segregation (Segregation) and coagulation (agglomeration), or macropores (Voids) in the carbon composite material, the silicon carbide can be seen that the very uniformly distributed by a binder. In particular, it was confirmed that silicon carbide and silicon oxides were homogeneously distributed without macroscopic / microscopic segregation.

9 is a view illustrating a carbon heater products made with the heating element (11) with a composition of the present invention. The actual carbon heater comprises a connector 14 for supplying power from the outside and supporting the heating element 11 and the heating element (11). In addition, tube 12 and metal wire 15 for supplying electricity from the outside to the heating element, the metal piece 16, the external electrode 17, the insulator (18 to he surround the heating element comprises an inert gas therein ) and the terminal block 19 is also included.

10 shows a heating state of a carbon heater manufactured from a heating element using the four-component composition of Example 2. FIG. Since the carbon heater according to the present invention does not use carbon fiber, the carbon heater does not generate sparks and plasma due to dielectric breakdown and maintains a stable heating state. On the other hand, the heating element made of the four-component composition of Example 2 had a saturation resistance of about 13 kV at an applied voltage of 115 V, and the output was measured at about 950 W.

Example  3

First, among inorganic powder components, inorganic carbide powder containing silicon oxide (SiO2) as a resistivity control agent based on silicon carbide (SiC) was added, 56 to 59% of graphite, and 56 to 59% of graphite as a lubricant, respectively. %, to prepare the 23% and 3% which includes four components (Quaternary) carbon composite composition.

The prepared four-component compositions were uniformly mixed through the raw material mixing process and then extruded under the same conditions as in Example 1 until the second carbonization heat treatment process, and then stabilized heat treatment process, first carbonization heat treatment process, and second carbonization heat treatment. The process was carried out. Next, the carbon composite compositions were further subjected to a third carbonization heat treatment process in a temperature range of 1,500 ~ 1,900 ℃. Then the third carbonization heat treatment process, the carbon composite heat generating element made of a four-component system composite carbon material composition of the above composition range are performed to evaluate the carbon heater is processed to the final electrical properties.

Figure 11 is a third heat treatment step of the carbonization temperature shows the resistance of the carbon heater (in Fig. 10 PN, GP, SC and SO denotes the respective novolak resin, graphite, silicon carbide and silicon oxide).

Embodiments in which the third carbonization heat treatment process is performed at 1,500 to 1700 ° C. indicate that the third carbonization heat treatment process is not performed or that the third carbonization heat treatment process is significantly increased in electrical resistivity than the embodiments performed at 1,800 to 1,900 ° C. Able to know.

This result, in the composite carbon material composition of the same components and composition ranges just means that it is possible to easily control the resistance to the output of the carbon heater with the addition of 3 carbonization heat treatment process of the present invention. This can greatly increase the degree of freedom of electrical design of the carbon heater by the process variable alone, it has a very useful practical significance.

12 shows the thermal conductivity characteristic of the carbon heater according to a third temperature carbonization heat treatment step.

In the carbon heater of the present invention, the thermal conductivity increases as the third carbonization heat treatment process temperature exceeds 1,400 ° C., but after 1,700 ° C., the thermal conductivity tends to stabilize or decrease slightly.

Silicon oxide has low thermal conductivity is a third heat treatment temperature is increased as unstable along a result, combined with the surrounding carbon contained in the composition is phase change thermal conductivity in the high silicon carbide. As the ratio of silicon carbide having high thermal conductivity increases, the macroscopic thermal conductivity of the carbon heating element increases.

And even if a third increasing the heat treatment temperature is more because almost completed in the vicinity of the phase transition has already 1,600 ℃, more even heating to a temperature or the thermal conductivity of the carbon heater is little change was determined to be slightly decreased.

Although the present invention has been described with reference to the drawings exemplified as above, the present invention is not limited to the embodiments and drawings disclosed herein, and various modifications may be made by those skilled in the art within the scope of the technical idea of the present invention. It is obvious that modifications can be made. In addition, even if the above described embodiments of the present invention while not explicitly described and described the effect of the effect of the configuration of the present invention, it is obvious that the effect predictable by the configuration is also to be recognized.

1: oven 2: cavity
3: door 4: magnetron
5: sheath heater 6: heater
11: heating element 12: tube
14 connector 15 metal wire
16: metal piece 17: external electrode
18: insulator 19: terminal terminal
S 100: Mixing Process S 200: Extrusion Process
S 300: Stabilization heat treatment process S 400: Carbonization heat treatment process

Claims (12)

Mixing a carbon composite composition comprising a ceramic powder;
Extrusion process;
Stabilization heat treatment process;
Carbonization heat treatment process; and
The carbonization heat treatment process is a carbon heater manufacturing method comprising a first carbonization heat treatment process out-gassing (Out-gassing) for 10 minutes to 2 hours at 600 ~ 1,000 ℃.
Mixing a carbon composite composition comprising a ceramic powder;
Extrusion process;
Stabilization heat treatment process;
A carbonization heat treatment process;
The composition comprises a phenol resin as a binder, a lubricant, and a base material for determining a specific resistance of the resistance heating element at a high temperature.
Mixing a carbon composite composition comprising a ceramic powder;
Extrusion process;
Stabilization heat treatment process;
A carbonization heat treatment process;
The composition comprises a phenol resin as a binder, a lubricant, a base material for determining the specific resistance of the resistance heating element at a high temperature, and a method for producing a carbon heater.
The method according to claim 2 or 3,
The phenol resin is a Novolac resin manufacturing method of a carbon heater.
The method according to claim 2 or 3,
And the base material is silicon carbide (SiC).
The method according to claim 2 or 3,
And the lubricant is graphite.
The method of claim 3,
The resistivity control agent is a method of producing a carbon heater is silicon oxide (SiO ₂ ).
Mixing a carbon composite composition comprising a ceramic powder;
Extrusion process;
Stabilization heat treatment process;
A carbonization heat treatment process;
The extrusion process is a method of producing a carbon heater performed at a speed of 10 ~ 120 rpm at 100 ~ 180 ℃.
Mixing a carbon composite composition comprising a ceramic powder;
Extrusion process;
Stabilization heat treatment process;
A carbonization heat treatment process;
The stabilization heat treatment process is a method of manufacturing a carbon heater is performed for 10 minutes to 2 hours at 270 ~ 300 ℃.
delete Mixing a carbon composite composition comprising a ceramic powder;
Extrusion process;
Stabilization heat treatment process;
A carbonization heat treatment process;
The carbonization heat treatment process is a method of manufacturing a carbon heater comprising a second and third carbonization heat treatment process.
The method of claim 11,
The second carbonization heat treatment process is performed for 10 minutes to 4 hours at 1,200 to 1,400 ° C., and the third carbonization heat treatment process is performed at 1,500 to 1,700 ° C. for 10 minutes to 4 hours.

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