JPS59169646A - Expendable pattern for ceramic shell mold for casting and its production - Google Patents

Abstract

PURPOSE:To prevent cracking in a casting mold and to improve dimensional accuracy by dispersing and adding fine grains of glass, etc. to an expendable hot melt material and molding an expendable pattern for a ceramic shell mold for casting. CONSTITUTION:An expendable hot melt material such as wax, naphthalene or the like is heated to the m.p. thereof or higher. On the other hand, fine grains such as glass beads, sand grain, metallic grains or the like are heated to approximately the same temp. as the temp. of the molten material and are charged and added to the molten material under stirring with a sirrer, etc. to accomplish uniform dispersion. The resulted mixture is cast into a mold for forming a desired pattern and thereafter the mixture is cooled to solidify. The solidified molding is removed from the mold for forming the pattern and the pattern is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fugitive model and a method for producing the same, which can provide an excellent monolithic ceramic mold without cracks.

It is well known that when manufacturing a ceramic shell mold, a refractory slurry is applied to the surface of a fugitive model that has been molded with a fugitive heat-melting substance such as wax, styronaphthalene and its mixture, or urea. Coarse-grained refractories are immediately deposited on the surface by sanding, dried to form the first layer, and this process is repeated 5 to 10 times to form layered refractories on the model. After that, heat-treat the fugitive model,
The refractory material layer is rapidly dissolved, melted, etc., and disappeared by solution treatment, gas treatment, etc., and the refractory layer is fired to form a hollow mold. However, when wax is used as a material for fugitive models, there are problems with wax deformation and expansion and contraction due to heat, making it unsuitable for large objects of 300 mm or more. Since the thermal expansion of the wax is greater than the rate of disappearance, cracks are likely to occur in the refractory layer, that is, on the mold side, and therefore it is difficult to put it into practical use. Mata Styrona 7
Models made of resin, mixtures thereof, urea, etc. are similar to wax in terms of expansion and contraction due to heat, and are advantageous for larger objects than wax models, but there still remains the problem of cracks occurring on the mold side. . Therefore, in order to solve the above-mentioned problems, efforts have been made to research the composition of fugitive heat-melting substances themselves and to discover new substances, but so far nothing that is practically satisfactory has been obtained. This is the current situation.

Based on the above technical background, the present inventor has conducted various researches and as a result, has solved the above-mentioned conventional drawbacks and obtained a practical fugitive model for ceramic molds.The main points of the present invention are as follows. is a fugitive model for a ceramic mold, which is formed by dispersing and molding a fugitive heat-fusible substance with fine particles such as glass, sand, metal, etc., which have a small coefficient of thermal expansion. The object of the present invention is to provide an excellent mold that does not cause cracks when a mold is formed using this model.

The present invention will be explained in detail below.

First, examples of the fugitive heat-melting substance used in the present invention include wax, nuclin, a mixture thereof, urea, etc., and other conventionally known substances are used. On the other hand, the fine particles used in the present invention include glass peas, Examples include sand grains and metal grains. These fine particles have a significantly smaller coefficient of expansion than the first VC heat-melting material, in order to alleviate and cancel out the effects on the refractory layer (cell layer) due to the large coefficient of expansion of the first VC heat-melting material;
Second, it must have high strength to the extent that it will not break under the influence of VC heat and during handling. Sixth, when mixed with a heat-molten substance, it will hold up well both in the molten state and in the state in which it cools and solidifies in the mold for molding the model. Fourthly, it is convenient to handle, has a minimum surface area, and has a minimum surface area and a direction of expansion. A spherical body with a richly uneven surface is desirable because it is uniform in the radial direction and has sufficient bonding with the hot melt substance. The size #i is preferably 0.3 to 5.0 cm in diameter.

The fugitive model of the present invention is made of two materials, the above-mentioned hot-melting substance and fine particles, and the manufacturing method thereof will be explained below.

First, the fugitive thermofusible substance is heated above its melting point.

Normal temperature is 10-30'C. This temperature is appropriately selected in consideration of workability such as room temperature and processing time.

- The fine grains are heated to approximately the same temperature as the molten substance by an appropriate means, added to the molten substance, and stirred with a stirrer or the like to uniformly disperse them. A model is obtained by pouring the mixture thus obtained into a desired model mold, cooling and solidifying it, and then taking it out from the mold. The addition ratio of fine particles to the hot melt substance is 1° to 80° by volume.
If it is less than 10%, the mold formed with this model will not be prevented from cracking, and if it exceeds 8°, it cannot be called a vanishing model, and it has deviated from its original function as a vanishing model. Therefore, 40 to 70% is a practical preferred range.

Kibatsu F! A/fi As mentioned above, this is a fugitive model used for a one-piece LAMITSUSHEL mold made of a fugitive heat-melting substance with fine particles such as glass dispersed therein, and this model was used to mold the mold. In this case, cracks that occur in the mold, which was a problem in the past, hardly occur. Furthermore, it was confirmed that the dimensional accuracy of the mold model was significantly improved. In addition, since the method of manufacturing the fugitive model of the present invention uses a casting method, there is no need for an injection machine that was conventionally used for model molding using hot melt materials such as wax. This makes it possible to create a model, and it is practically excellent as a vanishing model that eliminates the drawbacks of conventional models.

Examples of the present invention will be given below.

<Example> Wax was melted by heating and maintained at 7°C ± 5°C, and a diameter 1mm wax was separately prepared with unevenness on the surface. - Prepare 60% (volume) of the glass beads based on the wax, heat this to 90°C, put the glass beads into the wax, and stir with a stirrer to uniformly disperse the beads in the liquid. This was poured into a model mold with a size of 500 m. After this was cooled and solidified, it was taken out from the mold.

A ceramic shell layer is formed on the model thus obtained by a conventional method known in the art, and after drying, the layer is heated to eliminate the model (wax and glass beads are expelled) to form an integrated ceramic shell mold. was gotten. When this mold was inspected, no cracks were found anywhere, and when it was subsequently fired and measured, the dimensional accuracy of the mold was significantly improved compared to conventional molds.

Patent applicant: Kubota Iron Works Co., Ltd.

Claims (1)

[Claims] L. A ceramic shell mold comprising a fugitive heat-melting substance dispersed with fine particles having a smaller coefficient of expansion than the heat-melting substance such as glass, sand, metal, etc., and molded. Vanishing model. 2 A fugitive heat-melting substance heated above its melting point contains fine particles having a smaller coefficient of body expansion than the heat-melting substance, such as glass, sand, metal, etc., which have been previously heated to approximately the same temperature as the heat-melting substance. A method for producing a fugitive model for a ceramic shell mold, which comprises adding and stirring the mixture, pouring it into a mold for molding the model, and then cooling and solidifying it.