JPH08277B2 - Lost wax composition - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lost wax composition used for producing a precision casting model by the lost wax method.

[0002]

2. Description of the Related Art Precision casting by the lost wax method has recently been used.
It is becoming increasingly important in the manufacture of jet engine parts, nuclear reactor parts and general mechanical parts. The method generally involves the following steps. That is, first, a desired wax model is made by injecting a lost wax composition into a mold, immersing this wax model in a slurry of a refractory, sprinkling refractory particles before the slurry is dried, and waxing the refractory particles. The model is covered, the coating layer is thickened by repeating such dipping and sprinkling, the final slurry is covered and dried, and then the wax model is eluted by heating to form a mold. A metal melt is cast using this mold, and the product is made through sand removal, sprue cutting, and finishing.

As a model material used for a wax model in precision casting by such a lost wax method, the peculiarity of the manufacturing process and the product are precision casting products. (1) Good dimensional accuracy, that is, solidification shrinkage. (2) Good releasability from the mold (3) Excellent surface skin of the wax model, that is, flow line (wax inside the mold) (No streaky pattern of flow) and no entrainment of bubbles during injection molding (4) Good fluidity, low melt viscosity and wide molding temperature range (5) Recovered after use and reused many times (6) Large bending strength (7) It is required that there be no shell cracks when making the mold.

As a wax model material, a conventional animal or plant system,
Various types of mineral and synthetic waxes, natural rosins, rosin derivatives and petroleum resins have been used. However, waxes are not only brittle when the molded model has large shrinkage and surface shrinkage, and have low bending strength, and also have the drawback of being inferior in mold releasability from the mold during molding. In addition, the resins have a drawback that they have a large tackiness and remarkably poor releasability.

To improve these drawbacks, various additives such as terephthalic acid, isophthalic acid, benzoic acid, naphthalene, fatty acid amides, pentaerythritol, and other polyhydric alcohols and esters thereof, bisphenol, etc. are added to waxes. It has already been proposed to add powders or spheres of organic compounds, synthetic resins such as polystyrene, polyethylene and polybutylene, or spheres or starches to enhance the strength of the molded model and prevent damage at the time of removal from the mold. Such additives (hereinafter referred to as fillers) reduce the solidification shrinkage rate and are effective to some extent in improving the surface shrinkage, but their action is merely to reduce the amount of molten components in the wax composition. However, it has not been sufficient for solving the problems of the bending strength of the wax model and the defects such as flow lines and wrinkles of the wax model. Further, in the conventional wax composition containing a filler, when a wax model was eluted to form a mold, a phenomenon of cracking in the mold (shell cracking) often occurred, which made it difficult to manufacture a precision cast product.

[0006]

DISCLOSURE OF THE INVENTION The present inventors have improved the deficiency point of the above-mentioned filler-containing lost wax composition and have a high bending strength, a small solidification shrinkage rate, a small surface shrinkage, and stable dimensional accuracy and a surface skin. As a result of intensive studies to obtain a lost wax composition which is smooth and does not cause shell cracking, the purpose was achieved by a lost wax composition in which powdered melamine and a base wax were mixed in a fixed ratio. They have found that they can obtain the present invention and have reached the present invention.

[0007]

The lost wax composition of the present invention comprises 20 to 70% by weight of melamine powder and 80% of base wax.
It is characterized in that it is a composition consisting of ~ 30 wt%.
By using this lost wax composition, the above conditions (1) to (7) can be satisfied, and finally an excellent precision cast product can be obtained.

As the base wax, at least one selected from animal and plant waxes, mineral waxes and synthetic waxes conventionally used in the lost wax method, rosin resins and petroleum resins is used. Specific examples of the waxes include paraffin wax (for example, one having 20 to 40 carbon atoms), microcrystalline wax (for example, carbon number).
25-55), ceresin, carnauba wax, coconut wax, castor wax, bran wax, candelilla wax, fatty acids, fatty acid amides, and various synthetic waxes. The petroleum resin is preferably a resin obtained by polymerizing a petroleum-based unsaturated hydrocarbon containing a C5 aliphatic or C9 aromatic unsaturated hydrocarbon as a main component, which is obtained from a high-temperature cracked oil of petroleum. Examples of the rosin-based resin include natural rosin and triethylene glycol, glycerin, esterification products of polyhydric alcohols such as pentaerythritol, esterification products of hydrogenated rosin and the polyhydric alcohols, and polymerized rosins and the polyhydric alcohols. The esterified product of is preferably used. It is preferable to add such petroleum resin or rosin-based resin to waxes because the tackiness is small and the releasability is improved.

Melamine (2, used as a filler
4,6-triamino-1,3,5-triazine) powder has a melting point of 354 ° C. and has very good thermal stability. Melamine has excellent dispersibility in the wax component and can always provide a uniform composition. Further, even commercially available industrial melamine has very few impurities, and is completely disappeared when the mold is fired and does not remain inside the mold, which is convenient without adversely affecting the cast product.

The melamine powder preferably has a relatively coarse particle size, and has an average particle size of 20 to 300 μm, more preferably 70 to 130 μm.
The one of m is used. When a powder having an average particle size that is too fine is used, the surface texture of the wax model is smooth and glossy, but the viscosity of the composition becomes high, and the addition amount is limited.
On the other hand, if the average particle size is too coarse, the surface texture of the model loses its fineness, loses its luster, and adversely affects the casting surface of the product. In the case of the average particle diameter of the present invention, the increase in the viscosity of the wax composition is small and the addition amount can be increased without affecting the surface skin.

In the present invention, the amount of melamine powder added is 20 to 70% by weight, preferably 30 to 55% by weight based on the wax composition.
Weight percent is used. When the content of melamine powder is less than 20% by weight, the allowable temperature range for injection molding becomes narrow and molding is possible, but the finished surface texture becomes poor. 20 melamine powder
When the content is more than 10% by weight, the temperature range in which molding is possible is widened and molding becomes easy. When it exceeds 70% by weight, the melt component in the wax composition is reduced, the viscosity is increased, the fluidity is lowered, and the solidification rate is too fast. For example, when the wax composition is injected into a mold by injection molding, It becomes difficult for the objects to be sufficiently filled in the mold stenosis, resulting in a fatal defect of the wax model. In the range of the addition amount of the filler of the present invention, generally, as the amount of melamine increases, dimensional stability and surface roughness are improved, bending strength is increased, and surface texture is also improved.

The lost wax composition of the present invention is generally injected into a mold by injection molding or the like to obtain a wax model. This wax model has little solidification shrinkage and surface shrinkage, stable dimensional accuracy, and bending strength. Since it is expensive, it can be used on relatively large wax models without any problems. In addition, the surface skin is smooth with very few wrinkles and air bubbles entrained by the flow line, and it greatly contributes to the improvement of product quality. The lost wax composition is recovered after use and the base wax can be reused many times.

The wax model thus obtained is immersed in a refractory slurry by a conventional method, sprinkled with refractory particles while the slurry is not dried, and the wax model is covered with the refractory particles. It is repeatedly covered with the final slurry and dried, and as it is or in a flask, backed up by backing up and dried, the wax composition in the inside is melted by heating and discharged, a cavity of the prototype is formed (formation of the mold), and the mold is baked. After that, a molten metal is caused to flow in and solidify, sand is removed, a gate is cut, and finishing is performed to obtain a desired precision casting. When the melamine-containing wax model of the present invention is used, a precision casting product can be obtained without causing shell cracking because the coefficient of thermal expansion is small when the wax model is eluted to form a mold.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. The parts described in these examples mean parts by weight unless otherwise specified.

[0015]

Example 1 C ₅ Aliphatic unsaturated hydrocarbon-based petroleum resin (Esso Chemical Co., Ltd. trade name Escoletz 1304, average molecular weight 850) 30 parts, rosin-based resin (Harima Chemical Industry Co., Ltd. trade name Hariesta-C) 20
Part, paraffin wax (Nippon Oil Co., Ltd., trade name: paraffin wax 135 degrees), and carnauba wax 20 parts are placed in a stainless steel container and heated and melted at a temperature of 120 to 130 ° C for 15 to 20 minutes. After stirring, 43 parts of industrial melamine having an average particle size of 100 μm was added to this wax component and further stirred at a temperature of 100 to 105 ° C. for 20 minutes to obtain a uniform wax composition. (Melamine content 30% by weight) Examples 2 to 3 122 parts and 150 parts of melamine powder were added to 100 parts of the base wax prepared in the same manner as in Example 1 to obtain a uniform wax composition. Melamine content is 55% by weight
(Example 2) was 60% by weight (Example 3).

Example 4 30 parts of a base wax of C ₉ aromatic unsaturated hydrocarbon petroleum resin (trade name of Arakawa Chemical Industry Co., Ltd., Alcon P-100, average molecular weight: 700), rosin resin (trade name of Arakawa Chemical Industry Co., Ltd. F)
A wax composition was obtained in the same manner as in Example 2 except that 20 parts of GM-21), 30 parts of the same paraffin wax used in Example 1 and 20 parts of carnauba wax were used.

Example 5 A base wax was used as a C ₅ aliphatic unsaturated hydrocarbon-based petroleum resin (trade name Quinton D-100, manufactured by Nippon Zeon Co., average molecular weight).
1600) 15 parts, C ₉ aromatic unsaturated hydrocarbon-based petroleum resin (Esso Chemical Co., Ltd., trade name Escoletz 5300, average molecular weight 290) 15
Parts, the same rosin resin as used in Example 1, 20 parts of paraffin wax and 20 parts of carnauba wax were used to obtain a wax composition in the same manner as in Example 2.

Example 6 100 parts of the base wax compounded in the same manner as in Example 1
An average of 15 μm melamine granules with a range of 0.5 to 30 μm
43 parts were mixed to obtain a uniform wax composition.

Comparative Examples 1 and 2 In the same manner as in Example 1 except that the additives were not added, compositions containing only the base wax were obtained. (Comparative Example 1). Further, 43 parts of terephthalic acid was mixed with the base wax compounded in the same manner as in Example 1 to obtain a uniform wax composition.
(Comparative example 2).

The properties of the wax compositions of Examples 1-6 and Comparative Examples 1-2 are shown in Table 1. Each physical property was measured based on JIS.

[0021]

[Table 1]

Injection Molding Test An injection molding test was conducted using the wax compositions of Examples 1 to 6 and Comparative Examples 1 and 2 under the following conditions.

Molding Conditions Wax Temperature During Injection Wax compositions of Examples 1-6 and Comparative Example 2, 65 ° C. Wax composition of Comparative Example 1, 58 ° C. Injection pressure 30 kg / cm ² Injection holding time 10 seconds Wax of molded article There are two types of models, one for dimension measurement and one for face-down measurement as shown in FIGS.
Molded individually. The solidification shrinkage rate and the surface shrinkage are averages of 5 pieces each.

The wax model obtained was placed in a thermostatic chamber at 25 ° C. for 24 hours.
After being left for a time, when the dimensions became stable, the shrinkage ratio (%) and the surface shrinkage (m / m) were measured. The shrinkage is A of the model for measuring dimensions,
The lengths of the B and C parts were measured with a caliper and determined from the difference from the size of the mold. Further, the chamfer is obtained by measuring the number of m / m cavities of the a and b sides of the chamfer measurement model with the peripheral portion as a reference with a dial gauge. Further, the skin flow line of each model and the inclusion of air bubbles were visually observed.
The results are shown in Table 2.

[0025]

[Table 2]

The melamine-containing wax composition shows that the solidification shrinkage rate, the surface shrinkage are small, and the dimensional accuracy is stable, and the flow line and air bubbles are little involved and the surface texture is excellent.

When fine melamine is used, the shrinkage is smaller than when terephthalic acid is used, but it is larger than when melamine having an average particle size of 100 μm or more is used.

Casting Molding Test Using the wax compositions of Examples 1-6 and Comparative Examples 1-2, 1 in FIG. 3; shaft part, 2; gear part, 3; blade part, 4; bottom part, 5; hemisphere An impeller model having a complicated shape with a dent was made by an injection molding machine. The injection conditions were a wax temperature of 65 ° C., an injection pressure of 30 kg / cm ² , and an injection holding time of 10 seconds.

Next, a precision casting product was manufactured using the obtained model. That is, the wax model is colloidal silica,
It is dipped in a slurry consisting of water, zircon flour, fused silica, mullite flour, etc., and zircon flour, zircon sand, alumina sand, etc.
Sprinkle sand consisting of mullite flowers, etc., repeat this operation 6 times, cover the wax model with the final slurry, and dry at 25 ° C. After that, the wax composition was discharged by heating and melting in an autoclave at 7 to 9 kg / cm ² and 150 to 160 ° C. for 10 minutes to make a mold, and cracks (shell cracks) inside and outside the mold were visually observed. Then 1050 ℃,
This mold is fired in 1 hour and immediately stainless steel (S
A molten metal of US 304) was flown in, sand was removed, the gate was cut, and finishing was performed to obtain a mold.

Table 2 shows the results of observation of mold releasability from the mold and shell cracking.

The methods for evaluating releasability and shell cracking are as follows.

Releasability: The mold is washed with a solvent and then continuously molded, showing the number of the molds at which the mold cannot be removed. (Average of 3 experiments) Shell cracks; Large; Very many shell cracks Medium; Some shell cracks are small; Little shell cracks occur The composition of the present invention is excellent in mold releasability and shell cracks. Comparative Example 1 in which no additive was used and Comparative Example 2 in which terephthalic acid was used were inferior to the product of the present invention in both releasability and shell cracking. Also, when fine-grained melamine is used, the releasability and shell cracking tend to be inferior as compared with the case of using large-grained melamine.

[0033]

Since the lost wax composition of the present invention contains a predetermined amount of melamine, it has the following advantages.

(1) Since the molding temperature range is widened, the temperature control of the wax and the wax model making apparatus becomes easy.

(2) The strength of the wax model is increased, so that the model disappears even if the model is left for a long time.
Breakage and breakage problems are reduced, and the yield is improved.

(3) Product quality is improved because the solidification shrinkage rate, the surface shrinkage are reduced, and the variations are reduced.

(4) Since the defects on the surface of the model are eliminated, the defects on the skin of the cast product are eliminated and the product quality is improved.

(5) Since melamine has almost no ash and ash, the amount of residual ash after firing decreases as the amount of filler added increases, and casting defects after casting molten metal decrease.

(6) Since there is almost no shell crack during molding, the quality of the cast product is improved.

[Brief description of drawings]

[Fig. 1] Wax type model for dimension measurement, A, B and C are mold dimensions A = 150 mm, B = 150 mm, C = 30 mm.

FIG. 2 is a wax-type model for measuring surface roughness, and a and b are each side of the mold.

[Figure 3] Impeller wax model for precision casting

[Explanation of symbols]

 1 Shaft part 2 Gear part 3 Blade part 4 Bottom part 5 Hemispherical recess

Claims (3)

[Claims] 1. A lost wax composition comprising 20 to 70% by weight of melamine powder and 80 to 30% by weight of a base wax. 2. The average particle size of the melamine powder is 20 to 300 μm.
The lost wax composition according to claim 1, wherein 3. The lost wax composition according to claim 1, wherein the base wax is at least one selected from animal and plant waxes, mineral waxes and synthetic waxes, rosin resins and petroleum resins.