JPS6293041A - Molding material for casting pure titanium or titanium alloy - Google Patents

Abstract

PURPOSE:To obtain a molding material which can cast pure titanium and titanium alloy by specifying the components of a main material, auxiliary material for reinforcement and hardener. CONSTITUTION:The titled molding material is constituted of the main material essentially consisting of silica and alumina, 1 or >=2 kinds of the auxiliary materials for reinforcement selected from zirconium oxide, zircon, calcium oxide, spinel and mullite and the hardener constituted of phosphate and metallic oxide made of base. These materials are compounded at such ratios at which the sum of the silica and alumina as the main material is 90-55wt% in the entire material and that the auxiliary materials for reinforcement are 5-50wt% substd. in the ratio with respect to the total amt. of the main material. The phosphate as the hardener is used at 5-15wt% and the metallic oxide made of base is used in a 5-30wt% range.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mold material for casting pure titanium or a titanium alloy.

Conventionally, there are mold materials for metal casting for various metals that contain silica as a main component and use phosphates and basic metal oxides as hardening agents. Silica or silica sand is used as the silica, ammonium phosphate is used as the phosphoric acid, and fused magnesia or magnesia clinker is used as the base metal oxide.

In the case of this conventional molding material, the mixed and molded state of these materials is raised from room temperature to about 800°C or 900°C and incinerated, and the target molten metal is cast at that temperature. is taken.

In the case of casting with conventional metals, such as alloys such as cobalt chromium alloys and nickel chromium alloys, the melting point of the metal is 1.
Most metals, especially dental metals, have a melting point of about 1400°C, as represented by 300°C to 1400°C, so the melting point of silica, which is the main component, is 155
The melting point of titanium and titanium alloys in the future is 1600°C~1600°C, so it existed as a molding material that can withstand use. Since the temperature is 1700°C, when using a molding material whose main component is silica, the melting point is sufficiently exceeded, so titanium, which is physically unstable in the molten state, combines with the oxygen contained in the silica composition. However, the physical properties of pure titanium and titanium alloys cannot be utilized, and these metals deteriorate due to oxidation, and the casting surface suffers from burning, making it unusable.

In view of the relationship between the melting points of conventional mold materials and pure titanium and titanium alloys, the present invention aims to provide a mold material that can be cast for pure titanium and titanium alloys, and furthermore, to provide a mold material that can be cast for pure titanium and titanium alloys. However, even if these pure titanium and titanium alloys are melted at high temperatures of 1,600°C to 1,700°C, these metals will not react with the components in the mold material during melting, causing the metal to oxidize or change in quality. Furthermore, in order to make the mold material easier to manipulate and handle during casting, conventional mold materials are kept at a high temperature of several hundred degrees Celsius. The aim is to develop a mold material that can be used at room temperature.

The present invention was completed based on the above-mentioned objective, with the aim of providing a material that can be fully used at the melting point of pure titanium and titanium alloys and can be cast at room temperature. First, we have developed mold materials for casting pure titanium or titanium alloys and mold manufacturing methods that mainly contain silica and alumina, mold materials for casting pure titanium or titanium alloys that use spinel as the main material, and furthermore, mullite as the main material. The above three applications are pending, but the present invention has been completed as a result of further research, and the gist is that the main material and alumina, which are the main components, are supplemented with reinforcing auxiliary materials. Adding a hardening agent to the mold material gives it heat resistance, and when using the mold material, it is kneaded and fired at a temperature of 1000°C or higher after hardening to improve casting accuracy and fire resistance and prevent hardening. The purpose of this invention is to provide a molding material that can prevent oxidation, discoloration, roughness, etc. and produce cast products in a stable state.

The contents of the present invention will be explained in more detail below. The present invention consists of a main material mainly composed of silica and alumina; a reinforcing auxiliary material composed of zirconium oxide, zircon, calcium oxide, spinel, mullite, etc.; and a reinforcing material composed of phosphate and a basic metal oxide. The silica used here is silica, which has conventionally been used as a mold material when pouring molten metal. As this silica, one or more types selected from silica stone, silica sand, granular silica sand, cristopalite, etc. are used, and it is desirable to use silica with a purity of 90% or more, preferably a purity of 95%. % or more is required. The purity of this silica is 90% or more, which means that silica contains impurities such as ferric oxide, aluminum oxide, calcium oxide, etc. Even if aluminum oxide, that is, alumina, is contained as an impurity in the mold material. However, impurities such as ferric oxide and calcium oxide react significantly with titanium, so a minimum purity of 90% or higher is required. In addition, high purity alumina or high alumina minerals are selected as the alumina.
It is desirable to use one with a purity of 80% or more, preferably 90% or more.

In the case of this alumina, impurities include silicon oxide, calcium oxide, ferric oxide, manganese oxide, sodium oxide,
Contains potassium oxide, etc., and other than silica, which is silicon oxide among these components, it reacts significantly with titanium, and if these impurities are present in large quantities, the mold material and titanium will react with each other, similar to the case with silica, causing problems. Become.

Generally, a mineral with a purity of 85% or higher, such as diasbore or boehmite, is used as alumina, but preferably a mineral with a purity of 9.
If 0% or more alumina is used, the reaction between the metal and the mold material during molten metal casting can be minimized.

As reinforcing auxiliary materials, zirconium oxide (melting point: 2850°C), which is an oxide of zirconium, and zircon, which is a silicate, are used because of their fire resistance properties, and calcium oxide with a purity of 95% or more is used. Melting point is 257
0°C and high refractory resistance (using its chemical stability and non-bonding properties at high temperatures, spinel, which is an oxide of magnesium and aluminum, has a melting point of 2135"C and has a higher refractory resistance than alumina under high-temperature loads. In addition, mullite, which is a combination of silica and alumina, is a stable fire-resistant compound with a high melting point of 1850°C.As mentioned above, each reinforcing auxiliary material has a high melting point and is a chemically stable material. By adding this to the main material and kneading it, the refractory compound is mixed into the mold material before firing, making the mold material even better in fire resistance.

Phosphates and basic metal oxides are used as hardeners for the base material. Ammonium phosphate is commonly used as the curing agent. However, in addition to the ammonium phosphate, sodium phosphate, aluminum phosphate, magnesium phosphate, calcium phosphate, potassium phosphate, etc. may also be freely selected. However, ammonium phosphate as a phosphate salt is
Since titanium or titanium alloy has the property of solidification expansion that expands during hardening, etc., and hardens and contracts during casting, it is important that the expansion of the mold material and the degree of contraction during hardening of the molten metal are similar. Required as a condition. Considering both conditions, it is preferable to use potassium phosphate, which has the property of solidification and expansion, as a mold material for casting pure titanium or titanium alloys. However, some of the other various phosphates mentioned above do not have this solidification-expansion characteristic, but when using them, it is natural to design the casting space to be slightly larger, and also to make the mold. There must be.

Next, examples of basic metal oxides used as curing agents include magnesium oxide, fused magnesia, and magnesia clinker.
Those selected from the following are used. Since magnesia has a high melting point of about 2,800° C., its refractory properties are sufficient for use as a mold material for casting pure titanium or titanium alloys.

When manufacturing using these main materials and curing agent as a mold, a kneading liquid is used, and this kneading liquid is usually made of colloidal silica in order to increase mold strength and solidification expansion. The colloidal silica used has a silica content of 20% to 40%. Currently, colloidal silica with a concentration of 20% to 40% is commercially available, and it is easy to use these in terms of cost.However, there are no restrictions on using colloidal silica with a concentration of 40% or more. It's not a matter.

The mold material for casting pure titanium or titanium alloy according to the present invention has a main material mainly composed of silica and alumina, and one or more types of reinforcement selected from zirconium oxide, zircon, calcium oxide, spinel, and mullite. It is composed of a curing agent composed of a phosphate, a phosphate, and a basic metal oxide, and in actual use, colloidal silica is used as a kneading liquid. The compounding ratio of these is silica as the main material, and the sum of alumina is 90 to 55 in all materials.
% by weight, and auxiliary reinforcing materials are used in an amount of 5 to 50% by weight based on the total amount of the main material, phosphates as hardening agents are used in amounts of 5 to 15% by weight, and basic metal oxides are used in an amount of 5 to 15% by weight. 5-3
It is desirable to use it within the range of 0% by weight.

The sum of silica and alumina as the main material is 90 to 55% by weight.
The meaning of this is that for 90% or higher, phosphate and base metal oxide must be at least 5% by weight each due to restrictions on solidification and expansion, so the sum of silica and alumina must be 90% by weight or less. 5.
If the sum of phosphoric acid and basic metal oxide exceeds 45% by weight, too much solidification expansion will occur and the casting surface will become rough, so if the hardening agent is less than 45% by weight, the main material The content of silica and alumina is 55% by weight or less.

Furthermore, regarding zirconium oxide and zircon as auxiliary reinforcing materials, each is used in an amount of 5 to 50% by weight of the total amount of the main material, but if the amount is less than 5% by weight, the surface condition of the cast product and The occurrence of cavities is not significantly different from the case without addition, so it is excluded, and in the range of 50% by weight or more, the shrinkage rate of the mold becomes large due to roughness of the surface and blue discoloration, and due to hardening during firing. Therefore, the difference cannot be compensated for by solidification and thermal expansion, resulting in poor precision of the cast product, so quantities of 50% or more are excluded. Next, calcium oxide should be 5 to 50% by weight of the total amount of the main material.
The range below 50% by weight is excluded because the surface condition, the occurrence of cavities, the fire resistance, etc. are not significantly different from the case without addition, and the range above 50% by weight is due to bonding due to chemical reaction between the main material and the hardening agent. It was excluded because it excessively reduced the action and became brittle.

In addition, spinel and mullite should be 5 to 50% by weight, but 5% by weight or less] -' range is excluded because there is no major difference in surface condition, nest formation, discoloration, etc. from the case without additives, and 50% by weight or less. The above ranges are excluded because there are many cavities and the coagulation and heating expansion coefficients are small, resulting in poor accuracy.

Further, phosphate as a hardening agent is used in an amount of 5 to 15% by weight, but if it is less than 5% by weight, solidification and expansion will be insufficient, causing problems with dimensional accuracy. In this range, the solidification expansion becomes large, causing expansion and roughening of the casting surface, so it is not used.Furthermore, basic metal oxides are used in an amount of 5 to 30% by weight, but within this range of 5% by weight or less. For example, if the chemical reaction with phosphate is insufficient, the strength of the mold will be insufficient, and the amount of spinel produced will also be affected. Chemical reaction controls? 111 will not be possible, so it will be excluded.

A combination of these silica, alumina, a reinforcing auxiliary material, a phosphate as a hardening agent, and a basic metal oxide is used as a mold material for casting pure titanium or titanium alloys.

Next, it is stipulated that silica and alumina as main materials are mixed in a mixing ratio of at least 10 parts or more when the sum of both components is 100 parts. When the amount of silica is less than 10 parts, for example when the amount of silica is less than 10 parts, when the wax pattern is embedded in the mold material and heated to about 100 to 150 degrees Celsius to dewax, the surface of the casting space of the mold is Also, when the amount of alumina is less than 10 parts, the amount of raw material to react with silica and create a mullite or spinel structure is too small. Since there is a problem with the heat resistance of the created mold, each of them is removed from the purpose of use as the main mold material. In practice when manufacturing molds, it is better to make the sum of silica and alumina 100 parts, and when adding auxiliary materials such as zirconium oxide, zircon, and calcium oxide, mix 20 parts or more of one of them for better results. It's Uruchino.

In the present invention, silica and alumina are used as the main materials of the mold material, and by heat-treating the mold material to which one or more of zirconium oxide, zircon, calcium oxide, spinel, and mullite are added as reinforcing auxiliary materials, Mullite (melting point 1850'C) Spinel (melting point 2135°C) Copeillite (melting point 2000'C)
) is formed in the main material, immediately in the mold material, and the effect of adding a reinforcing auxiliary agent is also added. That is, the addition of zirconium oxide or zircon has a melting point as high as 2850°C, which improves the fire resistance and prevents seizure.Addition of an appropriate amount of zirconium oxide or zircon, for example, 20% to 30% by weight, promotes the formation of copillite even at the same firing temperature. It has the effect of improving the density of the tissue.

By adding calcium oxide, its melting point is as high as 2,570 degrees, which improves the fire resistance of the mold material, and its chemical bonding properties at high temperatures prevent excessive engagement of structures, resulting in molds that release easily. It has the effect of forming materials. Furthermore, with the addition of spinel and mullite, the formation of spinel, mullite, and coppillite by conventional firing was mainly formed on the surface layer, but by pre-mixing the auxiliary material before firing, it is possible to mix evenly into the inside of the mold material. As a result, the firing conditions are improved and a homogeneous structure with high refractory properties is obtained.

In addition, the addition of an appropriate amount of spinel results in a chemically stable structure at high temperatures, resulting in less deformation under load and a good surface condition of the cast surface. Furthermore, addition of an appropriate amount of mullite further improves fire resistance and chemical stability, provides a dense and strong structure with high resistance to thermal shock, and reduces the occurrence of casting cavities. In other words, the mold material obtained by adding the reinforcing auxiliary material to the main material and firing it as described above has a higher melting point ( (2050°C) and high chemical stability even when used for casting pure titanium or titanium alloys, these metals can combine with oxygen molecules in the mold material and oxidize, causing discoloration and rough casting surfaces. That is not the case.

Therefore, as a mold material for casting pure titanium or titanium alloy in a molten state, the main material mainly composed of silica and alumina of the present invention, zirconium oxide, zircon,
If it is composed of one or more reinforcing auxiliary materials selected from calcium oxide, spinel, and mullite, and a hardening agent of phosphate or basic metal oxide, it can be cast without changing the physical properties of titanium. It is possible. Furthermore, pure titanium and titanium alloys shrink in volume during hardening, but the mold of the present invention undergoes thermal expansion during heating and expansion during solidification, and the resulting overall expansion rate is equal to the shrinkage rate during cooling of pure titanium and titanium alloys. Therefore, by embedding a wax pattern in the shape of the final product in the mold, an appropriate casting space can be obtained by canceling out the expansion rate on one side and the contraction rate on the other side.

Next, the production of pure titanium and titanium alloy casting molds according to the present invention will be described with reference to examples.

First, a general manufacturing method for making a mold using the mold material according to the present invention will be described.

Silica and alumina, which are the main materials, are weighed at 90% to 50% by weight of all materials, silica accounts for 10% to 90% of the main material, and alumina accounts for 10% to 90% of the main material. At the same time, one or more supplementary materials to be added are weighed in an amount of 5% to 50% by weight of the total amount of the main material, and phosphate is 5% to 15% by weight of the total amount of the base metal oxide. Magnesium oxide is used in a proportion of 5 to 30% by weight in all materials, and these are combined with colloidal silica (silica content: 20
~40 weight percent) by weight or water, and the kneaded product is filled with the wax pattern constituting the mold space embedded in the container and allowed to harden naturally.

This operation is similar to conventional molding, such as dental molding.

In the present invention, after the hardened mold is heated and de-roasted, it is further heated and fired using an appropriate heating method, for example, placed in an electric furnace and fired to 1000°C or higher, preferably about 1200°C. The fired mold is cooled to room temperature and used for casting. Usually, this mold is used because it can be cast at temperatures below 400°C.

Conventional molds are mostly used in a heated state, but in the present invention, it can be cooled and cast at room temperature, and the strength of the mold is higher than the melting point of the molten metal to be cast. In addition, it must be physically stable.

Traditionally, molds were manufactured by firing at 800°C to 900°C;
The wax mold was dewaxed at ~200°C, and
The process involved removing ammonia gas, that is, volatilizing it, at a temperature of about 700°C to about 700°C, and removing phosphorus pentoxide gas at a temperature of about 700°C to 900°C.

However, in the present invention, by firing at a temperature of 1000°C or higher,
Tsuka, alumina, magnesia, etc. combine to create a murai.
By creating a refractory structure of one or more types of spinel or coppillite in the mold, and adding reinforcing auxiliary materials, a chemically stable structure with high refractory properties is created, and this mold is This will ensure that the mold conditions are met. Naturally, in this mold, at the same time as these refractory structures are formed, the melting point of the alumina itself used for this is much higher than that of pure titanium or titanium alloys, and silica also has a relationship with casting time. In addition, a heat-resistant structure such as mullite is formed on the surface of the mold and the casting space during the firing process, and a highly refractory structure is formed inside due to the addition of reinforcing auxiliary materials. A mold made by adding auxiliary materials to the material can be used satisfactorily as a mold material for pure titanium and titanium alloys.

Next, a mold is created using the mold material according to the present invention, and pure titanium and titanium are combined. ,・E:1 sieve'j, LJ 7j?
J',, ', -be, here: ・1e ゛ Tip The result run is ~1-21 as in the example.

Experimental example A mixture of 90% main material and 10% hardening agent by weight was vacuum kneaded with water, 40mm long x 30m wide.
M x FT 5mm thick plate with L Nox pattern was filled C', a mold was made as usual, and after hardening, it was fired at 1200℃ in an electric furnace and then lowered to room temperature to create it. When molten pure titanium was poured into a mold, the results were as shown in the attached table.

However, the main material accounts for 90% by weight of all materials, and this is 1.
00%, a part of the sum of silica and alumina is replaced with zirconium oxide, and the color, surface baking, roughness,
I checked the nests (of some numbers).

Note that during the determination, × indicates an unusable state, Δ indicates a usable state with some problems, O indicates a usable state, and ◎ indicates a suitable usable state.

As shown in Table 1 above (zirconium oxide is 50% of the main material)
It has been found that up to % can be used, preferably between 10% and 40%. Furthermore, by adding zirconium oxide, the fire resistance of the mold is further improved, seizure is prevented, oxidation and discoloration are reduced, and the occurrence of cavities is also reduced. This is because the melting point of zirconium oxide is 2850°C.
It is presumed that this is the result of improved overall fire resistance performance.

If the addition rate is increased to 50% or more, the shrinkage of the mold will increase due to hardening during firing, which will be difficult to compensate for through solidification and thermal expansion, making it unsuitable for dental use. Therefore, the pass/fail judgment is ×.

Table 2 shows the same results as in Table 1 when zirconium oxide was added by changing the mixing ratio of the main materials of silica and alumina.

Furthermore, almost similar experimental results were obtained for other adjuvants such as zircon, calcium oxide, spinel, and mullite.

That is, usable range of zircon: 10% to 50%, preferred range: 20% to 40%, usable range of calcium oxide: 10% to 50%, preferred range: 20% to 40%, usable range of spinel: 10% to 50%. %, preferred range 20% to 40%, usable range of mullite 10% to 50%, preferred range 20% to 40%, as mentioned above, up to 50% of the main material can be used, preferably 20% to 40% Met.

According to the results of an experiment in which two or more auxiliary materials were mixed in equal amounts and replaced with a part of the main material, the usable range of the mixture of zirconium oxide, calcium oxide, and spinel was 10%.
~50%, and the usable range of the mixture of zirconium oxide, calcium oxide, and mullite was 10% to 50%, etc., and almost the same results as in the case of adding only the auxiliary material were obtained.

The above experimental results show that by adding auxiliary materials to the main material of the present invention, the fire resistance and chemical stability of each auxiliary material are high, so there is no problem with baking hardening, mold shrinkage, etc., and 50%
It was confirmed that the molding material can be used in terms of surface condition, hue, occurrence of cavities, etc. within the range of addition so far.

Claims (1)

[Scope of Claims] 1) A main material mainly composed of silica and alumina, one or more reinforcing auxiliary materials selected from zirconium oxide, zircon, calcium oxide, spinel, and mullite, and phosphate. and a hardening agent consisting of a basic metal oxide, and a mold material for casting pure titanium or titanium alloy. 2) The pure titanium or titanium alloy casting mold material according to claim 1, wherein the total amount of the main material is 90 to 55% by weight of the total material. 3) The pure titanium or titanium alloy casting mold material according to claims 1 to 2, wherein the amount of one of the main materials is 10 to 90% by weight of the total amount of the main materials. 4) The mold material for casting pure titanium or titanium alloy according to claims 1 to 3, wherein 5 to 50% by weight of the total amount of the main material is replaced with a reinforcing auxiliary agent. 5) As silica, one or more types selected from silica stone, silica sand, granular silica sand, or cristopalite with a purity of 90
% or more of pure titanium or a titanium alloy casting mold material according to claims 1 to 3. 6) Claim 1 in which high-purity alumina or high alumina mineral with a purity of 80% or more is used as the alumina.
A mold material for casting pure titanium or titanium alloy according to items 1 to 3. 7) Claims 1 to 4 in which 5 to 15% by weight of the total material is used as the phosphate, and one or more selected from ammonium phosphate, potassium phosphate, and sodium phosphate are used. Mold material for casting pure titanium or titanium alloy as described. 8) 5 to 30% by weight of the total material as basic metal oxide
The mold material for casting pure titanium or titanium alloy according to claim 1, which is made of one or more selected from magnesium oxide, fused magnesia, and magnesia clinker. 9) A mold material for casting pure titanium or titanium alloy, which is obtained by mixing 20 to 40% colloidal silica liquid as a mixing liquid into the mold material described in item 1.