KR101041674B1 - Casting method for extreamly low temperature valve - Google Patents

Abstract

The present invention relates to a cryogenic valve casting method having a narrow diameter of an end region compared to a central region, the method comprising the steps of preparing a wax model, coating a ceramic shell on the wax model, and the ceramic shell on the wax model Injecting the filling gel into the hollow region of the wax model after the coating, and coating a ceramic shell on the outside of the wax model into which the filling gel is injected to complete the mold, and the wax model and the filling inside the mold. In the cryogenic valve casting method comprising the step of melting a gel, injecting molten metal into the mold, and removing the mold,

The filling gel is prepared by mixing an ethylene silica, silica sol and fused silica,

The said ethyl silicate, a silica sol, and fused silica are mixed in the ratio of 7 weight%: 38 weight%: 55 weight%.

Cryogenic Valve, Filling Gel

Description

Cryogenic valve casting method {CASTING METHOD FOR EXTREAMLY LOW TEMPERATURE VALVE}

The present invention relates to a valve casting method, and more particularly to a cryogenic valve casting method used at cryogenic temperatures.

Cryogenic valves are devices used for liquefied gas flow. Cryogenic valves are manufactured using precision casting because of their complex internal shape.

1 is a schematic diagram schematically showing a general precision casting method. As shown in the drawing, in order to manufacture the cryogenic valve, first, a wax model (b) having the same shape as the valve to be manufactured is manufactured. The production of the wax model (b) generally injects wax in a solid (semi-flow) state into the injection mold (a). (B) Each wax figure produced by injection is assembled to the wax tree (c) to increase production efficiency (WAX TREE). The type of assembly is determined by the size of the product is determined, and may vary depending on the shape of the wax model.

(C) The produced wax tree is a mixture of water, alcohol and colloidal silica with appropriately mixed ceramic powder to maintain the proper viscosity, soaked in a stirred slurry (dlurry, d) for a certain time, and the ceramic grains of a predetermined particle size Sprinkle on the surface, coat and dry thoroughly. This ceramic coating operation is repeated 8-10 times to obtain the desired thickness of the ceramic shell.

(D) After the coating operation is completed, the mold of the ceramic shell (e) is heated at high temperature and high pressure to melt and remove the wax model (b), and the same pupil shape as the shape of the desired product to be manufactured is formed inside the ceramic shell. This process is called dewaxing.

(E) The wax and impurities remaining in the mold are completely removed and fired for a long time at high temperature f to obtain high temperature strength.

(F) The molten metal (molten metal, g) of the desired material is injected into the mold (e) thus calcined and cooled to room temperature. (G) When the casting is cooled, the mold formed of ceramics is removed (descaling step). (H) Then, each product (g) is separated from each other, and (I) the surface of the product is polished to inspect the (J) dimensions and appearance to complete the product.

By the way, the cryogenic valve is thicker than the general valve because it is stressed at high durability and low temperature. In addition, since the internal shape is complex, the entire surface is curved, and the inlet is narrow, the probability of defects is high even when manufactured by the above-described precision casting method.

In particular, when a wax model is deposited on a slurry to coat a ceramic shell, a relatively narrow inlet is blocked and a shape of a product does not come out properly after injecting molten metal.

An object of the present invention is to provide a cryogenic valve casting method that can prevent the inlet is blocked by filling the filling gel inside the wax model when the ceramic shell is coated to solve the above problems.

The present invention for achieving the above technical problem,
Preparing a wax model, coating a ceramic shell on the wax model, coating the ceramic shell on the wax model, and then injecting a filling gel into the hollow region of the wax model, and filling the filling gel. Adding a ceramic shell to the outside of the wax model to complete the mold, melting the wax model and the filling gel inside the mold, injecting molten metal into the mold, and removing the mold. In the cryogenic valve casting method comprising the steps,
The filling gel is prepared by mixing an ethylene silica, silica sol and fused silica,
The said ethyl silicate, a silica sol, and fused silica are mixed in the ratio of 7 weight%: 38 weight%: 55 weight%.

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According to the cryogenic valve casting method of the present invention, if the inlet region is blocked during the formation of the ceramic shell, the gelled filling gel is filled into the wax model to prevent the inlet region from being clogged even when the ceramic shell is continuously coated. Occurrence can be minimized.

In addition, the removal of the ceramic shell may be easier during the spinning process.

In order to fully understand the present invention, preferred embodiments of the present invention will be described with reference to the accompanying drawings. Embodiment of the present invention may be modified in various forms, the scope of the invention should not be construed as limited to the embodiments described in detail below. This embodiment is provided to more completely explain the present invention to those skilled in the art. Therefore, the shape of the elements in the drawings and the like may be exaggerated to emphasize a more clear description. It should be noted that the same members in each drawing are sometimes shown with the same reference numerals. Detailed descriptions of well-known functions and constructions which may be unnecessarily obscured by the gist of the present invention are omitted.

2-4 are schematic diagrams illustrating a process of applying a ceramic shell to a cryogenic valve according to the present invention. Prior to the description, only one embodiment of the cryogenic valve is shown in the drawings, and the present invention is applicable to other cryogenic valves having a relatively narrow inner diameter (d2) compared to the diameter (d1) of the central region and having a complicated internal shape. It can be applied.

First, in order to cast the cryogenic valve, the wax model is completed as described above. The wax model may be formed through injection, and in the case of the wax model 110 illustrated in FIG. 2, a core may be used for the internal shape. The pupil 120 is formed inside the wax model 110. When the wax model 110 is completed, the worker tilts the wax model 110 in the slurry and slowly deposits it. Then, the wax model is taken out to determine whether the slurry is evenly applied to the entire area of the wax model. The mold handle is supported by the pedestal and slowly turned to allow excess slurry to flow down. Twist the wax model to the left and right and up and down so that the slurry on the wax model is not pushed to one side, and the caster vibrates so that the casting sand (sand) is evenly applied to the entire surface. When the slurry and foundry sand is applied to the surface of the wax model, it is dried.

This process is repeated several times. In the repeating process, the operator determines whether the inlet area of the wax model 110 is blocked by the slurry 130. When the coating operation is performed about 5-6 times and the inlet area is blocked by the slurry 130, the operator mixes the filling gel 150 and moves the filling gel 150 to the inlet area as shown in FIG. 2. It is injected into the inner cavity 120 of the wax model 110.

The filling gel 150 is filled in the pupil 120 to prevent the pupil 120 inside the wax model from clogging even when the ceramic shell is coated. Filling gel 150 is prepared by mixing the ethylene silica, silica sol and fused silica. Here, it is preferable to mix the mixing ratio of an ethyl silicate, a silica sol, and a fumed silica in the ratio of 7 weight%: 38 weight%: 55 weight%. However, this is only a preferred embodiment and the mixing ratio may be appropriately added or subtracted depending on the shape and size of the wax model.

The operator determines that the inlet area is blocked, and mixes the filling gel in the cup 140. Since the filling gel is gelled by a chemical reaction immediately after mixing, the operator mixes the filling gel individually whenever it determines that the inlet area of the wax model 110 is blocked. And immediately after mixing the filling gel 150 is injected into the inlet area. As shown in FIG. 4, when the filling gel 150 is completely filled inside the cavity 120, the worker infiltrates the wax model 110 again into the slurry to perform the coating operation again. The filling gel 150 filled therein does not flow because it is gelled. This ceramic coating operation is repeated several times to obtain the desired thickness of the ceramic shell.

After the coating operation is completed, the mold of the ceramic shell is heated at high temperature and high pressure to melt and remove the wax model and the filling gel, and the pupil is formed in the ceramic shell in the shape of a pipe pipe opening and closing hole. The wax and impurities remaining in the mold are completely removed and simultaneously baked at a high temperature for a high temperature strength.

The molten metal (molten metal) of the desired material is injected into the calcined mold and cooled to room temperature. Once the casting has cooled, the molds formed of ceramics are removed and each product is separated from each other. The surface of the separated cryogenic valve product is polished to inspect the dimensions and appearance to complete the product.

According to the cryogenic valve casting method, if the inlet region is blocked during the formation of the ceramic shell, the gelled filling gel is filled into the wax model to prevent the inlet region from clogging even if the ceramic shell is coated continuously. can do. In addition, since the filling gel and the ceramic cell are discharged together in the desalting process, the ceramic shell can be more easily removed.

The embodiment of the cryogenic valve casting method of the present invention described above is merely exemplary, and those skilled in the art to which the present invention pertains can various modifications and other equivalent embodiments therefrom. You will know. Accordingly, it is to be understood that the present invention is not limited to the above-described embodiments. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims. It is also to be understood that the present invention includes all modifications, equivalents, and substitutes within the spirit and scope of the invention as defined by the appended claims.

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1 is a schematic diagram showing a general precision casting process,

2 to 4 is an exemplary view showing a process of filling the filling gel in the wax model during the cryogenic valve precision casting according to the present invention.

* Description of the symbols for the main parts of the drawings *

100: mold 110: wax model

120: pupil 130: ceramic shell

140: cup 150: filling gel

Claims (3)

delete Preparing a wax model, coating a ceramic shell on the wax model, coating the ceramic shell on the wax model, and then injecting a filling gel into the hollow region of the wax model, and filling the filling gel. Adding a ceramic shell to the outside of the wax model to complete the mold, melting the wax model and the filling gel inside the mold, injecting molten metal into the mold, and removing the mold. In the cryogenic valve casting method comprising the steps, The filling gel is prepared by mixing an ethylene silica, silica sol and fused silica, The cryogenic valve casting method according to claim 1, wherein the ethyl silicate, the silica sol and the fused silica are mixed at a ratio of 7% by weight to 38% by weight and 55% by weight. delete

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