KR970000377B1 - Method of manufacturing a nozzle for metal casting process and the articles produced thereby - Google Patents

Abstract

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Description

Nozzle forming method for metal mold process and molded nozzle

1 is a schematic cross-sectional view of a mandrel in the state before the sheet is laid.

2 is a schematic cross-sectional view of a mandrel with a rubber mold set in a nozzle-shaped body.

* Explanation of symbols for main parts of the drawings

1: green sheet 2: mandrel

3: mould 4: beeswax band

5: nozzle-type body

The present invention relates to an improved method for forming nozzles for use in metal casting processes, and more particularly to a method of molding such a nozzle body and also a nozzle formed with a new structure.

Some types of nozzles with passages through which molten metal spills can flow include ladles, tundishes (pouring basins for pouring molten metal from the mold during casting operations). Or funnel) or metal mold process for introduction into the mold.

The best known method for forming such a nozzle is described as follows. After selecting the refractory raw material powder and preparing the raw material mixture by a well-known process, mixing the powder and granulating it into a granule (grain), the raw material grain is fixed in a rubber mold, and then It is a method of applying a uniform pressure to form a nozzle body having a passage.

The second best known method is the slip molding method.

In this method, a material slurry is prepared and poured into a mold that can absorb moisture (e.g. plaster), and the nozzle body is formed after sufficient moisture is absorbed into the mode to maintain the nozzle body. do.

However, according to the first method, the shaped bodies sometimes have an inhomogeneous part of the composition (caused by unequal distribution of the mixture grains) and cracks occur in the body. As a result of studying the cause of the problem, the inventors have found that the structural defect is due to the uneven movement of the raw material grains of various sizes within a certain range, so-called grain segregation when the mixture grains are fixed and pressed. I found out.

Investigations by the inventors have shown that the use of mixture grains that are more uniform in size and weight, or the use of mixture grains of different sizes, i.e. larger or smaller grains, cannot completely solve the grain separation problem. okay.

According to the second process, the problem of inhomogeneity in the configuration between the nozzle monsters is more pronounced and important than the first process. In this process, since moisture in the slurry is absorbed on the surface of the mold, relatively large grains tend to occupy an area close to the surface between the nozzle bodies.

Inhomogeneity in the nozzle body configuration has caused problems that render the nozzle unusable or shorten its use period.

It is therefore an object of the present invention to provide a new method for molding a nozzle body which solves the inhomogeneity in the configuration between the nozzle bodies.

Still another object of the present invention is to provide a nozzle that does not include a heterogeneous portion in the configuration between the nozzle bodies.

According to the invention the raw material mixture is formed of sheets rather than grains.

Therefore, there is no inhomogeneous portion in the sheet. In addition, the nozzle-shaped body formed by placing a sheet in a core device, i.e., a mandrel, such as a mandrel of a uniform pressure molding machine, has no inhomogeneous parts between the bodies. After the pressure is applied, the nozzle body will not have any of the structural drawbacks described above.

According to the present invention, the nozzle provided by the method of the present invention has a laminated structure in the thickness direction due to the sheet stacking operation. The nozzles have a composite layer glued to each other.

This structure prevents the accumulation of heat-stressed stresses as molten metal flows (up to about 1600 ° C) pass through the nozzle passages. Therefore, the thermal shock resistance and crack resistance of the nozzle are greatly improved.

In addition, the method according to the present invention can reduce dust generated in mold casting as compared to conventional mold manipulation using grain or powder.

Furthermore, the method according to the invention is very suitable for the automation of nozzle manufacturing and brings cost savings.

In order to achieve this purpose and to achieve the above described usefulness, the present invention provides a method of preparing a slurry material by mixing a binder and raw materials, forming a green sheet from the slurry material, and having a passage. Placing a green sheet on the core device to form a nozzle-type body, and pressing a uniform pressure on the body using an elastic mold such as a rubber mold.

In more detail this, the refractory raw powder is selected according to the required nozzle characteristics. Alumina, silica, zirconia, mullite, alumina-mullite, zirconia-mullite, metallic silicon, clay, graphite, pitch powder or resin powder (such as carbon) are generally selected as the main raw materials.

A certain amount of raw powder is mixed with a binder such as a liquid resin or polyvinyl alcohol and a dispersant as a slurry material as necessary.

Preferably, the slurry is transferred to an operation step of making a sheet using a doctor blade method, an injection molding method or an extrusion molding method. The adjusting blade is a device for adjusting the amount of liquid material on the roller of the spreader and is suitable for making a relatively thin belt-like sheet. The latter two methods are generally well known and suitable for making sheet-like materials that are relatively thicker than control blades.

It is preferably treated under reduced pressure to reduce foam in the slurry, and the viscosity of the slurry is adjusted by moistening or drying prior to the operating step of making the sheet.

The green sheet 1 (shown in FIG. 1) can be dried more or less to place the sheet in a core device such as a mandrel of a uniform press. Green sheet refers to a sheet of material before it is burned. This green sheet is 0.5 to 5.0 mm thick depending on the application to the nozzle.

The green sheet 1 is placed on the mandrel 2 which provides a passage for molten metal when the mandrel is removed to form a nozzle-like body.

Since it is easier to put the belt-shaped green sheet (1) on the mandrel than to place the clipped green sheet on the mandrel, wrap several layers of the belt-shaped green sheet (1) around the mandrel to make the belt-type green sheet (1) Preference is given to using.

The nozzle-like body may be reshaped or finished to smooth its surface and sized using a mechanism such as a spatula or lathe. The resilient soil, for example made of rubber or plastic, is set in close contact with the surface of the nozzle-shaped body, and the nozzle-shaped body covered with the mold is preferably pressed at a uniform pressure of 0.5 to 2.0 ton / cm.

The pressed nozzle body is taken out of the elastic mold and then heated to dry the nozzle body.

The finished and dried body is burned with heat in practical use, but if necessary the nozzle body is burned at a suitable temperature depending on the nature of the material before practical use.

(Example 1)

The raw materials shown in Table 1 were placed in a kneader and the binder and dispersant were mixed sufficiently to be a slurry material.

In this example, the surfactant was used as a dispersant.

The slurry was transferred to a vessel connected to a vacuum pump to reduce foam in the slurry.

The slurry was then set in a vessel of a doctor blade machine.

The adjusting blade produced a belt-shaped green sheet 1 having a thickness of 4 mm and a width of 20 cm. The green sheet 1 was left at room temperature for drying until it had a suitable strength. The green sheet 1 was then wound on the mandrel 2 of the uniform pressing machine to form a nozzle-shaped body 5 of almost desired size. And the surface of the body was finished with a spatula to eliminate roughness.

A rubber mold 3 was then set on the body 5 and the corners of the opening door of the mold were tightened with a seal band 4 to seal into the mold 3.

The nozzle-type body 5 was pressed at a pressure of 1.5 t / cm 2 in a uniform pressing machine.

The nozzle body was taken out of the mandrel 2 and the mold 3 and dried at a temperature of 150 ° C. to remove volatile substances contained in the binder. Finally, the nozzle body was adjusted to obtain the desired size and burned at 1400 ° C. in a heating crucible.

The physical properties of the nozzles provided are shown in Table 3.

Thermal shock resistance coefficient (R) is defined by equation (1) to indicate the resistance to thermal shock to explain the usefulness of the present invention.

R = S / (E × α)... … … … … … … … … … … … … … … … … … … … … … … … … … … (One)

Where S is the bending strength, E is the elastic modulus of elasticity, and α is the coefficient of thermal expansion.

(Example 2)

(compare)

The raw material and the binder shown in Table 1 were put into the kneader, mixed sufficiently to be a mixture grain material, and then dried naturally.

The mixture grain was fixed in the rubber mold with a mandrel to form a cavity with the shape of the proposed nozzle. The mold to which the mixture grain was fixed was sealed with the cap described above and set in a homogeneous pressing machine.

Accordingly, the nozzle was prepared in the same manner as in Example 1.

As a result, the physical properties of the nozzles are shown in Table 3.

(Example 3)

Example 1 was repeated except for the changed material as shown in Table 2. The physical properties of the resulting nozzles are shown in Table 3.

(Example 4)

(compare)

Example 2 is repeated except for the material changed as shown in Table 2. As a result, the physical properties of the nozzles are shown in Table 3.

* 1 is the value measured at 1000 ℃

* 2 is × 10 kgf / cm to be.

Referring to Table 3, the nozzle according to the present invention was improved in sub-abrasion and abrupt strength and each value of the thermal expansion coefficient was smaller than that of the comparative example.

Therefore, the nozzle of the present invention can withstand thermal shock better than conventional nozzles. When the nozzle of the present invention is heated, since the expansion is less than the conventional nozzle, it has a greater strength to withstand the stress caused by thermal expansion than the conventional nozzle.

In summary, the present invention relates to new methods for producing nozzles and to overcome the insolubility of conventional designs and new materials produced by the methods.

Since many changes and modifications can be made in the above description without departing from the scope of the invention, the appended claims should be construed to include all such modifications.

Claims (8)

Mixing the powdered raw material with a binder to prepare a slurry material; Making a green sheet from the slurry material; Drying the green sheet; Placing a green sheet over the core device to form a nozzle-shaped body; Finishing the body to a predetermined size; Nozzle molding method used in a metal casting process, characterized in that the step of applying a uniform pressure to the body using an elastic mold device. 2. The metal mold of claim 1 wherein the step of making the green sheet comprises using a doctor blade to control the amount of liquid material on the roller to form a thin belt-like sheet. Nozzle forming method used in process. 2. The nozzle forming method of claim 1, wherein the making of the green sheet comprises using an injection molding method. 2. The method of claim 1, wherein the step of making the green sheet comprises a step of using an extrusion molding method. The method of claim 1, wherein the step of making the green sheet comprises forming a green sheet in a belt shape, and the step of laying the green sheet comprises the step of winding the belt-shaped green sheet on a mandrel. Nozzle forming method used in metal casting process. The method of claim 1, wherein the green sheet has a thickness of 0.5 mm to 5.0 mm, depending on the application to the nozzle. The method of claim 1, further comprising the step of burning the body in a predetermined air condition according to the properties of the powder raw material used. A nozzle body having a passageway and having a structure laminated in the thickness direction thereof, the body secreting slurry material by mixing a powder raw material and a binder; Making a green sheet from the slurry material; Placing a green sheet in the core device to form a nozzle-shaped body; A nozzle for use in a metal molding process, characterized in that the body is molded in a process comprising the step of applying a uniform pressure to the body using an elastic mold apparatus.

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