JPS6117580B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a new disappearing model to replace wax used in precision casting methods such as investment casting methods or lost wax casting methods.

Wax, which is generally used as a model material in the lost wax method, has a large solidification shrinkage and is prone to defects such as deformation, cracks, and sink marks during wax molding.
It was necessary to create a mold that takes into account the combination of various waxes and the shrinkage and distortion of the wax, and perform injection molding.

Therefore, in order to eliminate the above-mentioned drawbacks, the applicant has developed a model material that is essentially different from wax.
In Japanese Patent Publication No. 51-20011, we proposed a method to obtain the desired disappearing model by melting naphthalene or paradichlorobenzole, which have similar physical properties, and injecting it into a mold and solidifying it. Compared to wax models, it has extremely high dimensional accuracy and strength, and it does not require the production of molds, so it has recently become popular as a method that can greatly shorten the process from design to manufacturing. It has become a place that is attracting attention in the industry.

However, even these excellent products have the following drawbacks. That is, when the above-mentioned model material, for example, naphthalene, is dissolved, the naphthalene evaporates and sublimates, resulting in an extremely strong irritating odor, which poses a major problem in operation.

The present invention eliminates the drawbacks of the prior art and creates an excellent vanishing model by using a model material that is essentially different from the conventional wax or the naphthalene or paradichlorobenzole previously proposed by the applicant. The purpose is to provide a manufacturing method.

A feature of the present invention taken to achieve the above-mentioned object is that a molten material containing 75% by weight or more of one or both of cetyl alcohol and stearyl alcohol, with the remainder being wax, is molded. The point is to obtain the required disappearing model by injecting and solidifying.

The present invention will be described in detail below. In general, a model material suitable for manufacturing a vanishing model for precision casting should satisfy the following conditions.

(1) No softening or deformation at room temperature.

(2) Small sink marks during solidification.

(3) The coefficient of thermal expansion is small.

(4) It has a low melting point and good pourability.

(5) Shall not be altered by heating.

(6) Easily removed by dissolution.

(7) High surface hardness and toughness.

(8) No particular pungent odor will be emitted when heated.

As a result of research to find model materials that satisfy the above conditions, the present inventors found that cetyl alcohol (chemical formula CH ₃ (CH ₂ ) ₁₄ CH ₂ OH C=16), stearyl alcohol (octadecyl alcohol, chemical formula CH ₃ ( It has been found that CH ₂ ) ₁₆ CH ₂ OH C=18) is preferred.

That is, the above-mentioned model material of the present invention has the above-mentioned (1) to (8).
However, like the model material naphthalene proposed earlier, it has much better injectability and moldability than commonly used wax, so it can be injected into plaster molds and molded. This completely eliminates the need for mold manufacturing, which was a very large part of the lost wax method in terms of both cost and process. Also, in the case of wax molding,
In order to obtain a wax model faithful to the mold, injection molding using pressure was required, but with the material used in the method of the present invention, such injection molding can be performed without the need for such injection molding.
It is possible to obtain a model that is faithful to the mold.

Particularly when comparing the model material of the present invention with naphthalene, it is found that not only does it have no irritating odor, which is the biggest drawback of naphthalene, but it also has a lower melting point than naphthalene, so it can be used for models coated with refractory shells at low temperatures.
It has the advantage that the model material can be melted and flowed out, and in addition, the surface roughness reproducibility is extremely good compared to naphthalene.

As a recent trend, there is a tendency for precision casting products to gradually increase in size. The larger the product, the larger the model, and proportionately stronger model materials are required. In general, the transverse rupture strength of wax is 10 to 50 Kg/cm ² , whereas the cetyl alcohol according to the present invention has a transverse rupture strength of 4 Kg/cm ² and the stearyl alcohol has a transverse rupture strength of 12 Kg/cm ² , but even with these values, shape retention is sufficient. Therefore, the alcohol is fully applicable as a model material for ordinary precision castings that are small to medium-sized and do not have extremely thin parts.

The former two alcohols have similar chemical structures and carbon numbers, and also have similar physical properties, so they can be used alone or in combination as model materials.

However, when cetyl alcohol, stearyl alcohol, or a mixture thereof is used industrially as a model material, it is advantageous in terms of strength and cost to add wax to the extent that it does not impair moldability. When wax is added to the alcohol, etc., they completely dissolve in the molten state to form a materially one-phase melt, and the solidified product of this melt also forms a complete solid solution.

In order to investigate the addition limit of wax, the present inventor
Wax (product name: PX-2 used, YATES, USA)
A melt of cetyl alcohol and wax with various contents (wt%) (manufactured by MANUFACTURING CO.) was melted and injected into a plaster mold to a length of 100 mm.
Create a rectangular parallelepiped sample with a width of 25.4 mm and a height of 10 mm.
The surface shrinkage shape, shrinkage rate, and bending strength were investigated.

The results are shown in FIG. In FIG. 1, the upper row shows the surface shrinkage shape, the middle row shows the shrinkage rate, and the lower row shows the bending strength. The surface shrinkage shape indicates the position and depth (unit: mm) of the maximum shrinkage recess in the longitudinal direction of the sample. The shrinkage rate is a value expressed as (V-V') x 100/V%, where V is the volume of the molding space of the mold and V' is the sample volume.

From FIG. 1, it can be seen that as the wax content increases, the transverse rupture strength also improves, but the shrinkage rate also tends to increase. That is, when the wax content is about 30%, the shrinkage rate is 0.5%, and the shrinkage rate decreases as the wax content decreases, that is, as the cetyl alcohol content increases. If the shrinkage rate exceeds 0.5%, the dimensional accuracy of the model will deteriorate due to the drop in moldability, so to ensure good moldability, it is recommended to keep the cetyl alcohol content at least 75% from a safety standpoint.

Furthermore, from the figure, the maximum shrinkage depth is 0.25 mm within the alcohol content range, and this value is within the dimensional tolerance normally required for precision models.

The inventor also investigated the reproducibility of the mold surface roughness of the model material according to the present invention. That is,
A molten mixture of cetyl alcohol and 7% wax (used in PX-2 above) was injected into molds made with various surface roughnesses, and the surface of the formed model was measured with a surface roughness meter. The reproducibility of the surface roughness of the mold was investigated.

The results are shown in FIG. In the figure, the mold roughness was determined according to JIS B 0601. In addition, in order to intuitively understand the unevenness of the model roughness, the actual unevenness is enlarged 1000 times and this fact is indicated by "(X1000)" on the left shoulder of the figure.

From FIG. 2, it can be seen that the surface roughness of the model formed using the model material according to the present invention is faithfully reproduced in accordance with the mold surface roughness. However, if the mold surface roughness is less than Rmax 1S, the reproducibility deteriorates. However, considering that the reproducibility of naphthalene is about 15μ, it is understood how excellent the reproducibility of the model material according to the present invention is.

Next, the method of coating the model material of the present invention with the refractory slurry is similar to the method generally used in the lost wax method, in which the refractory slurry is coated on the model and the drying process is repeated several times. 3～10
Make a shell with a thickness of mm. The model can be easily disappeared by immersing the model coated with a refractory shell in hot water or by rapidly heating it in a high-temperature atmosphere. In addition, the alcohol used in the method of the present invention does not deteriorate at all due to heating, and all the model materials that melt and flow out can be reused. In particular, unlike naphthalene, there is no irritating odor, and there is no sublimation, so there is no material loss. Without,
Although it is more expensive than naphthalene, it is sufficiently practical in terms of cost.

Examples of the present invention will be described below.

<Example 1> Cetyl alcohol and wax (PX-2) with a weight ratio of 7% to cetyl alcohol are mixed, placed in a container, heated and melted at 50 to 150°C, preferably 70°C, and then heated to a length of about 300 mm. was injected into a plaster mold of a turbine blade. No pressure was applied during injection. After the model had completely solidified, it was removed from the mold, and the shrinkage of the model was extremely small and no warpage was observed. Add 5 to 10 layers of refractory slurry (thickness 5
~10mm) After repeated coating drying, the outer periphery of the model melts and flows out in about 5 minutes by exposing it to hot air at 150-200℃.
I was able to extract the remaining model from Ciel. Immediately after firing this shell, molten 18-8 stainless steel was cast, resulting in a good casting with accurate dimensional accuracy and no surface defects.

<Example 2> Stearyl alcohol was used instead of cetyl alcohol in Example 1, and wax (PX-2)
Casting was carried out in the same manner as in Example 1 using a mixture of 5% of the above, and the same results were obtained.

As described above, the method of the present invention uses a melt with excellent moldability that contains 75% by weight or more of one or both of cetyl alcohol and stearyl alcohol, and the remainder is wax.
A vanishing model with excellent dimensional accuracy and reproducibility of mold surface roughness can be easily obtained without producing an irritating odor. In addition, since the above-mentioned model material has good moldability, there is no need to manufacture a mold that takes into account shrinkage, distortion, etc. of the model material, and precision casting costs can be significantly reduced. This is an extremely excellent method for manufacturing vanishing models used in manufacturing blades, molds such as shell molds, press molds, and other general precision casting products.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the bending strength, shrinkage rate, and surface shape when wax is added to cetyl alcohol, and FIG. 2 is a graph showing the measurement results of roughness fidelity using the same material.

Claims (1)

[Claims] 1. A vanishing model characterized in that a desired vanishing model is obtained by pouring a melt containing 75% by weight or more of one or both of cetyl alcohol and stearyl alcohol, the remainder being wax, into a mold and solidifying it. manufacturing method.