KR19980036119A - Process for producing graphite mold - Google Patents

Abstract

The present invention relates to a mold used to manufacture a casting, and relates to a method for producing a carbonaceous mold for solving the problems of the conventional sand mold and its inner mold.

In the present invention, in the manufacture of a mold used to manufacture a casting, a grinding step of crushing the raw material of pitch coke or petroleum cost into particles of a certain size, and kneading by adding a fixing agent to the particles crushed in the grinding step A mixing step, a molding step of pressurizing the kneaded material in the mixing step to a constant appearance, a firing step of heat-treating the molded product completed in the molding step at a high temperature, and processing according to a shape to cast the jaws in which the firing step is completed Characterized in that the finishing process is performed sequentially.

Description

Process for producing graphite mold

In general, in order to cast various ferrous and nonferrous metals, a casting method of producing a product having a desired shape after heating a metal as a raw material to a temperature above the melting temperature and liquefying is widely used. It performs the main functions that influence the quality of workability and product quality.

Sand molds and metal molds are known as such molds.

The conventional sand mold described above is to press the sand in the mold to produce a predetermined shape, looking at the process for producing the same as follows.

The first process of manufacturing the die by placing the processed die according to the shape of the casting on a flat mold cutting board while pressing the surface sand (sand of high fire resistance and small particle size to clean the surface of the die) while making it into a basic die. And a second step of filling the foundry sand in the mold after placing the basic mold manufactured in the first process on the bottom of the mold, and inverting the mold manufactured in the second process, that is, the lower mold, so that the wooden mold is positioned upward. After the lamination of the upper mold on the upper mold to fill the molding sand in the upper mold, and the third step, and after turning the upper mold and the lower mold in the third process, the lower mold is separated from the upper mold and the first mold If the basic mold manufactured in the process is exposed to the outside, the fourth process of removing the wooden mold from the basic mold, and the upper mold and the lower mold separated in the fourth process It was to include a fifth step of laminating each device.

However, the above-described conventional sand mold has a lot of work time and manpower since it has to repeatedly carry out the work of stacking or separating the upper mold and the lower mold. Particularly, the work of filling and compacting the molding sand in the mold is generally durable. In order to maintain this, a small amount of foundry sand had to be filled and chopped, and the foundry sand had to be inserted and chopped again and again.

In addition, since the durability of the mold is limited, casting of a complicated shape or a thin product is difficult to cast, and when repeated use, the edge portion is worn on the molten metal, and thus a casting of an accurate shape cannot be manufactured.

Furthermore, the molding sand, which is the main component of the mold, has to have the necessary conditions such as good moldability, strength, fire resistance, breathability, and has an appropriate particle size, but the amount of the casting sand is limited in order to extract the casting sand from nature. The foundry sand is gradually exhausted and difficult to secure.

In addition, the product cast in the sand mold, because the small particles of the molding sand is attached to the surface, not only need to separate work to remove it, but also because the surface of the product is not smooth and the productability is degraded to perform separate finishing work There were many cases.

In order to compensate for the problem of the sand mold, a metal mold is widely used in recent years, and the metal mold is described as follows.

The metal mold is manufactured by molding a material such as Pearlite cast iron or alloy cast iron having high heat resistance, and then heat-treating the same.

However, although the above-described conventional metal mold can cast a thinner thickness than the sand mold and can repeatedly cast a product having a precise dimension and a smooth surface, there is a fear of cracking due to the hot melt. The molten metal that is injected is not easily cooled and is kept at a high temperature for a long time, causing bubbles.

In order to suppress cracking and bubble generation due to such hot boiling water, a separate device for cooling by supplying water to the outside of the mold was required.

The present invention has been researched and developed in order to solve the above problems, and its object is to provide a method for producing a graphite mold for producing a casting having a minimum occurrence rate of the cast product and having an accurate dimension and a smooth surface. .

Another object of the present invention is to provide a method for producing a mold having good castability as a simple method by forming the carbon particles at a high temperature to machine the molten metal injection portion.

A feature for achieving the above object of the present invention is to crush the pitch coke (Pitch Coke) or petroleum coke (Petroleum Coke), which is a raw material of the carbon particles in order to produce a mold for use in castings A grinding step, a mixing step of adding and mixing a fixing agent to the particles prepared in the grinding step, a molding step of manufacturing the dough kneaded in the mixing step into a predetermined dimension, and heat-treating the molded product completed in the molding step at a high temperature. And a finishing step of machining the material of which the firing step is completed into a predetermined dimension and formation.

In the pulverization step, pulverized pitch coke or waste troleum coke is pulverized into powder of 0.4 to 0.8 mm particles and 2 to 300 μm particles, respectively.

In the mixing step, 0.4 to 0.8 mm particles and 2 to 300 μm particles completed in the grinding step are mixed in a ratio of 3: 1 by weight, respectively, and 20 to 30% of Coal Pitch is added thereto as a weight ratio to about 150 Mix by kneading evenly at ~ 170 ℃.

The molding step is made of a mold having an external shape of a certain size, and is pressed as a high pressure using an extrusion molding machine or a compression molding machine.

The firing step is to graphitize carbon particles which are heated again at about 2600 to 3000 ° C by incorporating a pitch after first heating the material having the molding process at about 750 to 1500 ° C.

In the processing step, the molten metal injection portion of the mold, that is, the portion to be cast is processed as a cutting or polishing machine, and the upper and lower molds are individually processed and integrated.

Hereinafter, the present invention will be described in detail with reference to Examples.

* Grinding Process *

The raw material is petroleum coke obtained by distilling tar, in which organic substances such as coal and wood are heat-treated at a high temperature of about 1000 to 1100 ° C, or petroleum coke obtained by distilling petroleum, a kind of asphalt component, at high temperature. Prepare.

In the present invention, the pitch coke and the petroleum coke may be selectively used or quantum coke may be used in combination.

Since the raw material itself contains about 10% of volatile components, it is necessary to calcinate in advance before the crushing process to remove the volatile components to prevent inadvertent shrinkage during the manufacturing process.

Since the raw material is not composed of particles of a certain size, but is agglomerates, it should be pulverized into fine particles. The raw materials are put into a roll grinder and operated for a predetermined time, and the particle size is 0.4 to 0.8 mm using a mesh. Each is separated into particles having a thickness of 2 to 300 µm.

* Mixing Process *

0.4 to 0.8 mm and 2 to 300 [mu] m of materials, each of which were separated in the grinding process and separated, were mixed in a ratio of 3: 1 by weight, respectively, to form a blend to the maximum density, and then, as a weight ratio to the blend. Add 30% Coal Pitch and knead evenly in the mixer.

The nose pitch is intended to improve the formability of the material, when 30% or more is increased in fluidity, but the cohesive force is lowered, while the fluidity is lowered to 20% or less.

In addition, when heat of 160 to 170 ° C. is applied in the process of mixing the materials in the mixer, the fluidity of the cowl pitch may be increased to shorten the mixing time.

Molding process

The material kneaded in the mixer is cooled in a cooler, and then put into a compression molding machine or a compression molding machine and pressurized at a high pressure to form a predetermined shape.

This molding process is to mold only the outer shape of a mold to a certain size, and to achieve simultaneous compacting of the mold. An extrusion molding machine is used for molding a small mold of the outer shape and a compression molding machine for molding a large mold. It is preferable to use.

During the molding process, the molds are produced as separate moldings as upper and lower molds.

Firing process

The molded article completed in the forming step is put into a heat treatment furnace and first heated at 750 to 1500 ° C, then impregnated with pitch, and then heated to a high temperature of 2600 to 3000 ° C for graphitization.

During the firing process, after the primary firing of the mold, the pitch can be combined to increase the density of the material by high temperature firing.

Most of the volatiles are removed during the firing process to produce a high density, high strength graphite body.

* Manufacturing process *

It is necessary to process the molten metal injection part, that is, the part where the shape of the cast product is cast by using the graphite produced by the above-described processes, and a known cutting machine or grinding machine can be used as such processing means. Depending on the efficiency, the machine is optionally processed.

The finished mold is produced by processing the upper and lower molds in which the molten metal injection portion, hot water, and gas discharge holes are formed in the graphite body.

The mold of the present invention prepared by the above method, as shown in Table-1, has a high heat resistance passion degree, a low coefficient of thermal expansion, and has good mechanical properties.

TABLE 1

Properties of Graphite Molds Prepared by the Method of the Present Invention

As shown in Table 1, the mold of the present invention has a very high thermal conductivity, so when the molten metal is injected into the mold, the internal high temperature is easily released to the outside to suppress the generation of bubbles, and the melt injection time and the cooling time can be shortened. It can be effective.

In addition, since the thermal expansion coefficient of the mold is very small, it is possible to cast an accurate product without changing the dimensions of the casting.

In addition, since the mechanical properties such as tensile strength and compressive strength are good, there is no damage even after repeated use of the mold can be used economically for a long time.

In particular, the mold of the present invention has a high heat resistance that is maintained in a stable state without causing a thermal change at 2000 ° C. or lower, and thus it is possible to prevent a change in enthusiasm such as being changed or cracked by high temperature molten metal.

As described above, the present invention is an advantageous invention that can produce a high quality product while using a simple and semi-permanent manufacturing method compared with the sand mold or metal mold that has been conventionally used.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to molds used for casting various industrial products, and more particularly, to a method for producing graphite molds for improving the work efficiency and improving the quality of cast products by manufacturing the molds with graphite.

Claims (5)

In manufacturing molds used to manufacture castings, A pulverizing step of crushing the raw material of pitch coke or petroleum coke into particles of a constant size, a mixing step of kneading by adding a fixing agent to the crushed particles in the crushing step, and pressurizing the kneaded material in the mixing step to a certain appearance Forming process, A process for producing a graphite mold, characterized in that the firing step of heat-treating the molded article completed in the molding step at a high temperature, and the finishing step of processing according to the shape to be cast the material is completed. The method for producing a graphite mold according to claim 1, wherein the grinding step separates the particles of the raw material into 0.4 to 0.8 mm particles and 2 to 300 µm particles, respectively. 2. The mixing process according to claim 1, wherein the mixing step mixes 0.4 to 0.8 mm particles and 2 to 300 µm particles in a weight ratio of 3: 1, respectively, in a weight ratio of 20 to 30%. A method for producing a graphite mold, characterized in that the nose pitch is added and mixed. 4. The method for producing a graphite mold according to claim 1 or 3, wherein heat is applied at a temperature of 150 to 170 deg. C during the mixing step. The graphite process according to claim 1, wherein the firing step is characterized by graphitizing carbon particles by subjecting the formed material to a first heat treatment at about 750-1500 ° C., then combining the pitches and heat-treating again at 2600-3000 ° C. Process for the Preparation of Vaginal Molds.