JPS62144846A - Casting mold for high melting point metal and its production - Google Patents

Abstract

PURPOSE:To permit quick collapse of a casting mold for a high melting metal by incorporating a specific ratio of calcium oxide into a molding material and casting said material then crushing and removing the same by an acid or water. CONSTITUTION:>=5wt% Calcium oxide is incorporated into the molding material and one kind selected from refractory particles, gypsum and binder is incorporated therein. The refractory particles consist of one kind selected from silica sand, silicon nitride, silicon carbide, magnesia, etc. The binder is sodium silicate, Kibushi clay, water glass cement, etc., or the mixture composed thereof. One kind is selected from sulfuric acid, hydrochloric acid and nitric acid for the acid for removing the molding material. The molding material contains a liquid org. compd. and/or a peptizer and the liquid org. compd. is a cyclohexanol, benzene, etc. The peptizer is linseed oil, surface active agent, etc. The casting mold formed of such material collapses quickly when immersed in the acid or water and is satisfactorily usable as the casting mold for a high melting metal.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a mold for a high melting point metal that facilitates the removal of the mold after casting. More particularly, the present invention relates to acid- or water-disintegratable molds for refractory metals that can be disintegrated and removed by casting acid or water.

Conventional technology molds can be classified into sand molds, metal molds, plaster molds, etc. according to the type of their constituent materials. Traditionally, molds for high melting point metals used in precision castings and medical castings include:
A mold made of refractory particles as a base material to which a caking agent or the like has been added has been used.

In general, the characteristics required of a mold are (a) fire resistance, c) ease of molding, and (c) v? (d) Removal of the mold after molding (removal from the mold) is easy and quick;
(e) have sufficient air permeability; (f) have flexibility against solidification shrinkage after casting molten metal; (g) have a dense casting surface and (h) It has reusability, and (1) It is inexpensive. Among the above characteristics, (C) is attracting attention as production lines become automated. There is.

That is, with conventional molds, it is necessary to manually remove the mold after casting, and removal requires a lot of time, especially when the shape is complex or when used as a core. This means that when automating the production of castings,
Therefore, there has been an increasing demand for molds that can be easily released from the mold and that can automate casting production.

Molds that can meet the above requirements include water-soluble molds made of refractory particles as a base material and to which a water-soluble compound is added as a binding agent (Japanese Patent Application Laid-open No. 54-96424, 54-96425, and 54-151507). No.) etc. have already been developed.

The molds disclosed in JP-A Nos. 54-96424, 54-96425, and 54-96425 are based on refractory particles such as silica sand, alumina, magnesia, zircon, chromite, and olivine, and contain water-soluble compounds. The following binders are added as binders and subjected to flow molding or pressure molding, and the following binders are used as water-soluble compounds: ■ Calcium phosphate, calcium oxide, and calcium oxide with a CaO/P2O3 molar ratio of 0.1 to 2.85. A mixture of one selected from the group consisting of calcium hydroxide and phosphoric acid, or further at least one of sodium phosphate, potassium phosphate, magnesium phosphate and zinc phosphate.
Binder containing seeds (JP-A-54-96424), ■ Binder consisting of at least one of metaphosphates of potassium, sodium, calcium, magnesium, barium, aluminum or zinc (JP-A-54-964)
(No. 25) ■ A binder consisting of barium hydroxide and an aluminate of an alkali metal (Japanese Patent Application Laid-open No. 151507/1983) is used.

The above invention improves heat resistance by using refractory particles, further adds a binder made of a water-soluble compound to make the mold to be formed water-soluble, and removes the mold after casting by immersing it in water. The main purpose of this method was to make the process easier and faster, and also to increase the strength of the mold, and it has achieved considerable results.

Problems to be Solved by the Invention As mentioned above, as a mold for high-melting point metals that has higher strength and heat resistance than before and is easier to remove after casting, a water-soluble compound is added to the refractory particles as described above. Products added as binders have been developed. However, the above mold had problems as detailed below.

That is, first of all, the above-mentioned conventional mold has the problem that water-soluble compounds such as aluminate, barium hydroxide, and phosphate used as a binder composition are expensive. As a result, the cost of the mold to be formed increases, which is a very disadvantageous condition for mass production of castings.

Next, metal elements such as aluminum, magnesium, potassium, or barium contained in the water-soluble compounds; aluminates; phosphoric acid and phosphates; meclic acid and metaphosphates, etc. have an adverse effect on the natural environment and working environment. Therefore, there was a risk that special waste liquid processing equipment would have to be installed to remove the above-mentioned contaminants contained in the waste liquid during mold removal until they were below the standard value.

Metals that are easily oxidized at high temperatures, such as titanium, or metals that are naturally easily oxidized, such as rare earth metals, and alloys containing these metals should be cast in a vacuum, an inert gas atmosphere, or using a solvent such as barium chloride. However, when a conventional water-soluble mold is used, the molten metal and the water-soluble compound react with each other, and the metal is oxidized, so it cannot be used.

Furthermore, since the above-mentioned conventional template is water-soluble, the removal process can be automated without manual work.
There is still a problem that the time required for this process cannot be sufficiently shortened. As a result, when casting production is implemented as a closed system, this mold removal process may become the rate-limiting step.

As mentioned above, conventional water-soluble templates are expensive, have a risk of environmental pollution due to the contained metal elements or acids and their salts, and cannot be used for active metals that are easily oxidized. However, it is an object of the present invention to solve these problems and to provide a method that is inexpensive, has no environmental pollution problem, and can be used for active metals. It is an object of the present invention to provide a mold for a high melting point metal that can be easily and quickly removed.

Means for Solving the Problems As a result of various studies and studies to solve the above-mentioned problems with conventional molds, the inventors decided to use a mold material containing calcium oxide, and removed the mold using acid or water. The present invention was developed based on the finding that the above-mentioned method is extremely advantageous in achieving the above object of the present invention.

That is, the mold for high-melting point metal of the present invention includes a υI shape material containing at least one selected from the group consisting of refractory particles, gypsum, and a binder, and calcium carbonate, and includes casting acid immersion or water immersion. It is characterized by collapsing due to

In the mold for high melting point metal according to the present invention, the calcium oxide can be added to the mold material in advance, and the calcium oxide can also be added as quicklime or fused calcia. Furthermore, at least one calcium compound that produces calcium oxide upon thermal decomposition, such as calcium carbonate, calcium hydrogen carbonate, calcium oxalate, calcium sulfite, and calcium hydroxide, is added to the mold material, and after molding, the calcium compound is decomposed. It can also be contained in the mold by heating above the temperature, and the calcium hydroxide can also be added as slaked lime or silica lime.

Further, the amount of calcium oxide contained in the mold is preferably 5% by weight or more, and if it is less than 5% by weight, the desired acid or water disintegratability cannot be obtained. Furthermore, when only calcium oxide is used, it has sufficient strength and disintegrability.

Further, the refractory particles may be of any material as long as it has fire resistance and can achieve the properties of the mold, such as providing sufficient strength to the mold to be formed, such as silica sand, alumina, magnesia, zircon, zirconia, etc. , chromite, olivine,
Various conventionally known materials such as kaolin and chamotte can be used.

In addition, the above-mentioned binder may be one that satisfies the same conditions as the above-mentioned refractory particles. Examples of inorganic binders include sodium silicate Kibushi clay, bentonite, water glass, cement, etc.; polyvinyl alcohol, linseed oil,
Examples include phenolic resins, furfural resins, polyisocyanate resins, and natural resins such as gum rosin and wood rosin.

The acid used for removing the mold according to the present invention after casting is preferably selected appropriately depending on the type of metal to be cast. For example, for metals such as gold, silver, and platinum, most acids and water such as sulfuric acid, hydrochloric acid, and nitric acid can be used for highly acid-resistant metals such as stainless steel and titanium alloys, and for copper alloys, hydrochloric acid can be used. , sulfuric acid, etc., and nitric acid is preferable in the case of metals that are easily corroded by alkaline aqueous solutions, such as aluminum alloys.

Furthermore, the amount of the acid or water may be less than or equal to the amount of calcium carbonate contained in the mold. In the case of an acid, the initial concentration is preferably IN or higher. Furthermore, the higher the initial concentration, the faster the mold disintegrates and speeds, but there is a limit depending on the acid resistance of the casting.

Heat is generated when removing the mold, but this can be effectively countered by measures such as increasing the amount of liquid I, cooling the liquid, and treating it under running water.

The mold for high-melting point metals according to the present invention is produced by adding calcium oxide to a molding material consisting of refractory particles, stone bones, and a binder and compression-molding it, or further adding a liquid organic compound and, if necessary, a peptizer. It can be manufactured by adding and fluid molding, followed by drying.

In addition, the mold for high melting point metal according to the present invention includes calcium compounds that generate calcium oxide upon thermal decomposition, such as calcium carbonate, calcium hydrogen carbonate,
It can also be produced by adding at least one of calcium oxalate, calcium sulfite, and calcium hydroxide, performing flow molding or pressure molding, and then heating to a temperature higher than the decomposition temperature of the calcium compound to convert the calcium compound into calcium oxide. It is possible.

Eaves" In order to solve the above-mentioned problems with conventional molds, it is preferable to manufacture the mold from the above-mentioned composition containing calcium oxide and remove it with acid or water after casting.

That is, calcium oxide reacts with acid or water according to the following reaction formula = CaO+28"-+Ca"+H20...■Ca○
10H20→Ca (○H)2...Reacts as shown in ■. Therefore, molds according to the invention containing calcium carbonate quickly disintegrate when immersed in acid or water.

In particular, the mold collapses more quickly when immersed in acid.

The above reaction only needs to be carried out to the extent that the template can be completely disintegrated, and it is not necessary that all of the calcium oxide contained in the template be dissolved. Therefore, the acid and water contained in the aqueous solution used for the template removal treatment may be equal to or less than the equivalent amount of calcium carbonate contained in the template, and in the case of acid, the concentration thereof is preferably IN or higher.

In addition, calcium oxide, calcium carbonate, calcium hydrogen carbonate, calcium oxalate, calcium sulfite, calcium hydroxide, etc. are not only inexpensive and can be produced stably by hand in large quantities, but they also have the potential to have a negative impact on the natural environment or work environment. Therefore, the waste liquid generated when removing the mold can be treated by simply neutralizing it, and special waste water treatment equipment is not required.

Furthermore, calcium oxide is a thermodynamically very stable material, so the molds of the present invention can be used for casting active metals. That is, since calcium is an element with a low electronegativity of 1.0, it forms a stable oxide, so if it is a metal with a higher electronegativity than calcium, it will not cause an acid red exchange reaction. In other words, any metal whose free energy of formation of its oxide is greater than that of calcium oxide can be used for casting.

Hereinafter, the present invention will be described in more detail based on Examples, but the following Examples do not limit the scope of the claims of the present invention in any way.

Examples Example 1 Quicklime (Cab) or fused calcia (Cab) and cyclohexanol were mixed and flow molded to a size of 80φ x 70mm. A molded product was vacuum dried and then heated to a temperature of 170°C.
After heating at 0°C for 2 hours and cooling to room temperature, water, 5N-
The time required for the molded product to disintegrate after being immersed in hydrochloric acid, 5N sulfuric acid, or 5N nitric acid was investigated. The results are shown in Table 1.

As is clear from Table 1, the molded bodies disintegrated in an extremely short time in all cases. Similar results were also obtained when a mixture of one or more of the acids mentioned above was used.

Example 2 80% of molding material mixed with refractory particles and quicklime (Cab)
A molded body of φX70mm was compression molded or fluidized with benzene and linseed oil added as a peptizer and binder, heated at a temperature of 1000°C for 2 hours, cooled to room temperature, and then heated with water. The time required for the molded body to disintegrate was investigated by immersing it in water.

The results are shown in Table 2.

As is clear from Table 2, the molded bodies disintegrated in a short time in all cases. Similar results were obtained using hydrochloric acid, sulfuric acid, nitric acid and mixtures of one or more of these acids. Also,
Naturally, organic solvents other than benzene and peptizers and binders other than linseed oil can also be used.

It goes without saying that refractory particles other than the seven types shown in Table 2, such as silicon nitride and silicon carbide, can also be used. It is also naturally possible to use a mixture of a plurality of refractory particles. It is of course also possible to use mixtures of quicklime and other calcium compounds. Compression molding is also possible.

Table 2 Results of Example 2 Example 3 A mold material containing a calcium compound and alumina as refractory particles and silicic acid as a binder was added with IJum and mixed with water to a size of 80φ x 70mm. The fluidized molded body was heated to the decomposition temperature of the calcium compound for 2 hours, then cooled to room temperature, and immersed in water to examine the time until the molded body disintegrated.

The results are shown in Table 3. In both cases, the molded bodies disintegrated in a short time. Similar results were obtained using hydrochloric acid, nitric acid, sulfuric acid and mixtures of one or more of these acids.

It goes without saying that refractory particles other than alumina can also be used. Naturally, inorganic binders and organic binders other than sodium silicate can also be used.

In addition to the five types of calcium compounds shown in Table 3, compounds that can be thermally decomposed into calcium oxide and mixtures of one or more of these calcium compounds are also possible.

Table 3 Results of Example 3 Example 4 A molding material made of a mixture of industrial heavy calcium carbonate and gypsum or refractory particles was mixed with water and flow-molded into a size of 80φ x 70mm. The molded product was heated for a period of time, cooled to room temperature, and then immersed in water to examine the time required for the molded product to disintegrate. However, if necessary, IJum (silicic acid) was added to the mold material as a binding agent. The results are shown in Table 4.

As is clear from Table 4, all molded bodies disintegrated in a short time. Similar results were also obtained when nitric acid, hydrochloric acid, sulfuric acid, and mixtures of one or more of these acids were used.

It goes without saying that molding materials other than the plaster and types of refractory particles shown in Table 4 can also be used.

It is also naturally possible to mix and use a plurality of mold materials. Naturally, inorganic binders and organic binders other than IJum (silicic acid) can also be used.

Calcium compounds other than calcium carbonate that thermally decompose into calcium oxide and one of these calcium compounds
Naturally, mixtures of more than one species can also be used.

(*This is the result of 240 minutes) Example 5 Water was added to a mixture of 95 parts of wollastonite (CaSiO3) particles and 5 parts of sodium silicate as a binder, and the mixture was fluidized.
After heating at 800℃ for 2 hours and cooling to room temperature,
The time required for the molded product to disintegrate after being immersed in N hydrochloric acid was investigated. As a result, the molded body disintegrated in about 2 minutes. Similar results were obtained when nitric acid, sulfuric acid, and a mixture of one or more of these acids were used in addition to hydrochloric acid. It is of course also possible to use a mixture of wollastonite and a molding material such as refractory particles or plaster.

Naturally, inorganic binders and organic binders other than sodium silicate can also be used. Compression molding is also possible.

Example 6 A molding material made of a mixture of silica sand and quicklime (Cab) was mixed with benzene and linseed oil, and a molded body was flow-molded to a size of 80φ x 70mm. After vacuum drying and smoking, it was heated at a temperature of 1000°C for 2 hours.
After heating for a period of time, the molded body was cooled to room temperature, and then immersed in water to investigate the relationship between the amount of calcium oxide contained in the mold and the time required for the molded body to disintegrate.

In addition, water was added to a molding material made of a mixture of gypsum and industrial heavy calcium carbonate, and a molded body was fluid-molded to a size of 80φ x 70mm, heated at a temperature of 850°C for 2 hours, cooled to room temperature, and then immersed in water. The relationship between the amount of calcium oxide contained in the mold and the time it takes for the molded body to disintegrate is shown in attached Figure 1 with old marks.

In any of the above cases, as the amount of calcium oxide contained in the mold after heating increases, the time to collapse the molded body becomes shorter, but even if the amount of calcium oxide increases to 5% by weight or more, the time to collapse is too short. Must not be. Further, if the content of calcium oxide is 5% or more, the mold has sufficient resiliency for practical use.

Effects of the Invention As described above, the template containing calcium oxide according to the present invention can be removed more easily and quickly by treatment with acid or water compared to conventional water-soluble templates. Not only is it possible to easily produce cast products with extremely complex shapes and cores with small openings, which were difficult to produce with conventional molds, but it is also cheaper and less likely to pollute the environment. Less is.

The mold according to the invention further has the following advantages. That is, since calcium oxide is a very stable substance, it can be used even when casting active metals that are easily oxidized. Also, the refractory particles are reusable.

Due to the above advantageous properties, the casting according to the invention can be effectively used when automating the casting of refractory metals.

[Brief explanation of drawings]

Attached FIG. 1 is a graph showing the relationship between the calcium oxide content of a mold and the disintegration time when the mold is immersed in water.

Claims (14)

[Claims] (1) A mold for a high-melting point metal, which contains at least 5% by weight of calcium oxide and is removed by acid or water after casting. (2) The mold for a high-melting point metal according to claim 1, which contains at least one member selected from the group consisting of refractory particles, gypsum, and a binder. (3) The refractory particles are silica sand, silicon nitride, silicon carbide,
The mold for high melting point metal according to claim 2, characterized in that the mold is made of at least one member selected from the group consisting of magnesia, titania, alumina, zircon, zirconia, chromite, olivine, kaolin, and chamotte. (4) The binder is sodium silicate, Kibushi clay, bentonite, water glass, cement, polyvinyl alcohol, linseed oil, phenolic resin, furfural resin, polyisocyanate resin, or a mixture thereof. A mold for high melting point metal according to claim 2 or 3. (5) The high melting point according to any one of claims 1 to 4, wherein the acid is at least one selected from the group consisting of sulfuric acid, hydrochloric acid, and nitric acid. Mold for metal. (6) A method for producing a mold for a high melting point metal, which comprises molding a mold material containing at least 5% by weight of calcium oxide. (7) Manufacturing a mold for a high melting point metal according to claim 6, wherein the mold material contains at least one selected from the group consisting of refractory particles, gypsum, and a binder. Law. (8) The method for manufacturing a mold for a high melting point metal according to claim 6 or 7, wherein the mold material is compression molded. (9) A mold for a high melting point metal according to claim 6 or 7, wherein the mold material contains a liquid organic compound and/or a peptizing agent, and is dried after fluid molding. manufacturing method. (10) The liquid organic compound is cyclohexanol,
10. The method for producing a mold for a high melting point metal according to claim 9, wherein benzene, alcohol, kerosene, or light oil is used. (11) The method for producing a mold for a high melting point metal according to claim 9 or 10, wherein the deflocculant is linseed oil, a surfactant, ethylene glycol or polyethylene glycol. (12) After flow molding or pressure molding a molding agent containing a calcium compound that produces calcium oxide when heated, the mold is heated to a temperature higher than the decomposition temperature of the calcium compound, and the resulting mold contains 5% by weight or more of calcium oxide. A method for producing a mold for a high-melting point metal, the method comprising: (13) Claim 12, wherein the calcium compound contains at least one selected from the group consisting of calcium carbonate, calcium hydrogen carbonate, calcium oxalate, calcium sulfite, and calcium hydroxide. A method for manufacturing molds for high melting point metals. (14) The high melting point metal according to claim 12 or 13, wherein the molding material contains at least one selected from the group consisting of refractory particles, gypsum, and a binder. Manufacturing method for molds.