JPS61135448A - Mold material for casting pure titanium and titanium alloy and production of casting mold - Google Patents

Abstract

PURPOSE:To obtain a mold material for casting a Ti material which does not oxidize or deteriorate the Ti material in the mold material consisting essentially of silica and contg. a hardener composed of phosphate and basic metallic oxide by adding alumina to silica. CONSTITUTION:The mold material for casting pure Ti or Ti alloy consist of the main material consisting essentially of silica and alumina and the hardener composed of the phosphate and basic metallic oxide. The mold material is obtd. by kneading about 10-82wt% silica, about 10-82% alumina, about 5-15% phosphate and about 5-30% basic metallic oxide with the colloidal silica and calcining the mixture at >=about 1,000 deg.C after curing. Said material is produced by forming the refractory structure of >=1 kinds among mullite, spinel and cordierite in the mold material. The mold material permits casting of the pure Ti and Ti alloy having a high m.p. of 1,600-1,700 deg.C and permits the casting of the molten metal at an ordinary temp.

Description

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

Conventionally, there have been metal casting mold materials 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 magnene aclinker is used as the basic metal oxide.

With regard to this conventional molding material, there is a method of mixing and molding these materials, raising the temperature from room temperature to about 800°C or 900°C, incinerating it, and casting the target molten metal at that temperature. It 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 up to about 1400°C, as represented by 300°C to 1400°C, so the melting point of silica, the main component, is 1550°C.
℃~1600℃, it existed as a molding material in a condition that could be used sufficiently. However, as casting materials for pure titanium and titanium alloys, since the melting point of future titanium and titanium alloys is 1,600°C to 1,700°C, when using a molding material whose main component is silica, the melting point must be sufficiently lowered. Titanium, which is physically unstable in the molten state, combines with oxygen contained in the composition of silica to form titanium oxide, making it impossible to utilize the physical properties of pure titanium and titanium alloys. Deterioration of the metal and burning of the casting surface occurred, making it unusable.

The present invention aims to provide a mold material that can be cast for pure titanium and titanium alloys in view of the relationship between the melting points of conventional mold materials and pure titanium and titanium alloys. Even if these pure titanium and titanium alloys are melted at high temperatures of 1600°C to 1700°C,
The purpose is to provide a mold material that does not cause oxidation or alteration of the metal by reacting with the components in the mold material during melting, and furthermore, it aims to provide a mold material that does not cause oxidation or alteration of the metal by reacting with the components in the mold material during melting. In order to make it easier to handle, in conventional mold materials, molten metal is poured into the casting space formed within the mold material while maintaining it 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. The main points are that, by adding alumina to silica, which is the main component in conventional mold materials, it provides a means to raise the melting point of the mold material, and at the same time, when using mold materials, these The kneaded mixture is fired at a temperature of 1000° C. or higher, and the resulting mold is made stable against molten metal at high temperatures.

Hereinafter, the content of the present invention will be explained in more detail.

The present invention is composed of a main material mainly composed of silica and alumina, and a hardening agent composed of a phosphate and a basic metal oxide. The silica used as a mold material during casting, whose warping force is utilized, is one or more selected from silica stone, silica sand, granular silica sand, cristobalite, etc., each with a purity of 90%. It is desirable to use a purity of 95% or more, preferably a purity of 95% or more.

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 specified.

Further, the alumina is selected from high purity alumina and high alumina minerals, and it is desirable to use one with a purity of 80% or more, preferably 90% or more. In the case of this alumina, impurities such as silicon oxide, calcium oxide, ferric oxide, manganese oxide, sodium oxide, and potassium oxide are included. Among these components, other than silica, which is silicon oxide, there is a significant reaction with titanium, and these impurities If there is a large amount of titanium, the reaction between the molding material and titanium will occur, similar to the case with silica, causing a problem.

Generally, a mineral with a purity of 85% or higher, such as diaspore or boehmite, is used as alumina, or preferably with a high 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.

Phosphates and basic metal oxides are used as hardening agents for the base material.

As the phosphate as the curing agent, ammonium phosphate is commonly used. However, in addition to the ammonium phosphate, sodium phosphate, aluminum phosphate, potassium phosphate, calcium phosphate, potassium phosphate, etc. may also be freely selected. However, ammonium phosphate as a phosphate has the property of solidification expansion that expands when it hardens, and because titanium or titanium alloys harden and shrink during casting, the expansion of the mold material and the hardening of molten metal. It is required as a manufacturing condition that the degree of shrinkage be similar. Taking these conditions into consideration, it is preferable to use ammonium 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 hardening 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 2800° C., it has sufficient refractory properties to be used as a mold material for casting pure titanium and 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.

As colloidal silica, the silica content is 20% to 40%.
% is used. Currently, commercially available colloidal silica ranges from 20 to 40, so
Although these are easy to use due to cost, 40
% or more of colloidal silica is not an equivalent limitation.

Such a pure titanium or titanium alloy casting mold material according to the present invention is composed of a main material mainly composed of silica and alumina, and a hardening agent composed of a phosphate and a basic metal oxide, In actual use, colloidal silica is used as a kneading liquid. The blending ratio of these was 7 Lika as the main material, the sum of alumina was 90 to 50% by weight, the phosphate as a hardening agent was 5 to 15% by weight, and the basic metal oxide was 5 to 30% by weight. It is hoped that it will be used inside the bag. The fact that the sum of silica and alumina as the main materials is 90 to 50% by weight means that at 90% by weight or more, phosphate and basic metal oxide must be at least 5% by weight each due to restrictions on solidification expansion. Since the sum of silica and alumina must be 90% by weight or less from a certain 0%, it is removed, and in the range of 50% by weight or less, the sum of phosphoric acid and basic metal oxides is 45% by weight or more, it is removed by solidification. The hardening agent is 45% because the expansion will be too much and the casting surface will become rough.
When it is less than 5% by weight, silica and alumina as main materials are
5% by weight or less is unthinkable, and if impurities are included, 50% by weight or less will be removed. Furthermore, phosphate as a hardening agent is 5
~15% by weight is used, but if the weight range is less than 5% by weight, the solidification expansion will be insufficient, causing problems with dimensional accuracy, and if it is more than 15% by weight, the solidification expansion will be large and abnormal expansion may occur. Basic metal oxides are not used because they cause corrosion and seriously roughen the casting surface.Furthermore, basic metal oxides are
~30% by weight is used, but if it is less than 5% by weight, the chemical reaction with the phosphate is insufficient, resulting in insufficient mold strength.
As the curing time becomes longer, workability deteriorates and the amount of spinel produced is also affected, so in the range of 30% by weight or more, the curing time is shortened and the chemical reaction with the phosphate is controlled. excluded from being unable to do so.

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

Next, it is specified that silica and alumina as the main materials are mixed in a mixing ratio of at least 10 parts or more, where the sum of both components is ioo parts. When the amount of silica is less than 10 parts, for example, when the amount of silica is less than 10 parts, the wax pattern is buried in the mold material and
When de-roasted by heating to about 0°C, it will cause surface roughness on the surface of the casting space of the mold, which will cause surface roughness on the cast product. The amount of raw materials required to react with silica to form mullite and spinel structures is too small, and the heat resistance of the created molds is a problem, so they are removed from the intended use as mold materials. From the practical point of view during mold production, it is desirable that the sum of silica and alumina be 100 parts, with one being at least 20 parts or more.

In the present invention, since silica and alumina are used as the main materials of the mold material, both components can be heated to mullite (melting point: approximately 1850°C), which has a melting point higher than titanium's melting point of 1600°C to 1700°C. ℃), spinel (melting point: approx. 2135℃), cordierite (melting point: approx. 2
000℃), one or more of these structures are formed in the main material, that is, in the mold material, and the melting point of alumina is higher than that of titanium or titanium alloy, that is, 2
Coupled with the temperature of 050°C, even if the mold material is used for casting pure titanium or titanium alloy, these metals will not combine with oxygen molecules in the mold material and oxidize, or cause discoloration or rough casting surfaces. When making a mold using this mold material, heat treatment must be performed after curing to create the composition described above. In the state where the above-mentioned structure has been formed through this heat treatment, the temperature at which molten metal is cast is about 1400° C., as in the case of conventional mold materials whose main component is silica. Therefore, there is no need for products such as mullite, spinel, cordierite, etc. Therefore, if the mold material for casting pure titanium or titanium alloy in a molten state is composed of the main material mainly composed of silica and alumina of the present invention, and a hardening agent of phosphate or basic metal oxide. Ba,
It is possible to cast titanium without changing its physical properties. In addition, pure titanium and titanium alloys shrink in volume during hardening, but the mold of the present invention expands thermally during heating and during solidification, and as a result, the overall expansion coefficient is equal to that of pure titanium and titanium alloys when cooled. Since it is almost the same as the shrinkage rate,
By embedding a wax pattern in the shape of the final product in the mold, an appropriate casting space can be obtained by compensating 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 as the main material and alumina are weighed, silica is 10-82% by weight, alumina is 10-82% by weight.
5 to 15% by weight of phosphate,
As a basic metal oxide, magnesium oxide is used at 5 to 30%
Weigh % by weight, mix these with colloidal silica (silica content = 20 to 40 weight range) or water, and mix the kneaded product with the wax pattern constituting the mold space embedded in the container. Fill it and let it 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, or in the present invention, they 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.

Conventionally, molds were manufactured by firing at temperatures of 5ooc to 900°C, but in conventional molds, firing was first performed at temperatures of 100°C to 900°C.
De-waxing the wax mold at 200℃, then 400℃
Ammonia gas was removed, ie, volatilized, at a temperature of approximately 700°C to 700°C, and phosphorus pentoxide gas was removed at a temperature of approximately 700°C to 900°C.

However, in the present invention, silica,
Alumina, alumina-magnesia, etc. are combined to create a refractory structure of one or more of mullite, spinel, and cordierite in the mold, so that the mold meets the molding conditions for pure titanium and titanium alloys having the above-mentioned melting point. It turns out. Naturally, in this mold number, 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 the silica also In addition, during the firing process, a heat-resistant structure such as mullite is formed on the surface of the mold and the casting space, and silica is located inside the mold, so there is no problem with heat resistance, and the glue strength and alumina are the main components. The mold used as a component is sufficiently usable as a mold material for pure titanium and titanium alloys.

Next, a mold was created using the mold material according to the present invention, and pure titanium and titanium alloy were cast, and the results shown in the following experimental example were obtained.

Experimental example: The main material in the mold material is 80% by weight, and the hardening agent is 2% by weight.
0% was vacuum kneaded with water, the wax pattern was buried in it, a mold was made in the usual way, and after hardening, it was fired in an electric furnace at 1200℃, and then the mold was cooled to room temperature. When molten pure titanium was cast, the results are shown in Table 1. However, the amounts of silica and alumina are shown based on the sum of the two as 100, and the curing agent is 20%.
Regarding each component in the weight percentage, ammonium phosphate is 12% by weight, and magnesia is 8% by weight.

Note that during the determination, ◯ and ∆ marks indicate usable items, and x marks indicate those that are difficult to use. The same applies to Experimental Example 2 and subsequent examples.

Table L (Note L) The tensile strength is the tensile strength of a wire rod with a diameter of 2 gourds and a length of 20 crn obtained through an experiment.

(Note 2) The hardness is the Brinell hardness test result of a flat plate obtained in Experiment 1 with a thickness of 3fi and 2 tri.

Experimental example λ The main material in the mold material is 55% by weight, and the hardening agent is 4% by weight.
5% of the mixture was vacuum kneaded with water, the wax pattern was buried in it, a mold was made as per legal requirements, and after hardening, it was fired at 1200℃ in an electric furnace, and then the mold was cooled to room temperature. When molten pure titanium was cast, the results are shown in Table 2.

However, the amounts of silica and alumina are shown based on the sum of the two as 100%. The composition of each component in the 45% curing agent is ammonium phosphate at 15% by weight and magnesia at 30% by weight.

Table 2 Experimental example 3゜The main material in the mold material is 40% by weight, and the hardening agent is 6% by weight.
A mold made by vacuum kneading 0% with water, embedding the wax pattern, legally making a mold, curing it, firing it at 1200℃ in an electric furnace, and letting it cool to room temperature. When molten pure titanium was cast, the results are shown in Table 3.

However, the amount of silica and alumina is expressed by taking the sum of the two as xoo%, and the composition of each component in the curing agent 60 range is as follows: ammonium phosphate is 20% by weight, magnesia is 30% by weight. %.

Table 3゜Experiment example 4゜The main material in the mold material is 90% duck by weight, and the hardening agent is 1% by weight.
A mold made by vacuum kneading 0% with water, embedding the wax pattern, legally making a mold, curing it, firing it at 1200℃ in an electric furnace, and letting it cool to room temperature. When molten pure titanium was cast, the results are shown in Table 4.

However, the amount of IJ strength and alumina are shown based on the sum of both as 100%. Also, each component in the 10% curing agent is ammonium phosphate at 5% by weight and magnesia at 5% by weight. It is 5%.

Surface Experiment Example 5゜When the sum of silica and alumina is 90% by weight or more, ammonium phosphate is 5% by weight or less as a hardening agent, and magnesia is 5% by weight or less, mechanical strength (tensile strength, elongation, hardness) ) is good, but in dental applications, if the ammonium phosphate content is less than 5% by weight, the solidification expansion will be insufficient and the size of the cast body and shrinkage of the metal (titanium) cannot be compensated for. Furthermore, if magnesia is less than 5% by weight, there is no mold green strength after hardening, resulting in surface roughness during removal. Due to the above two points, it is unsuitable for dental use.

However, in parts for the construction industry, there is no need to produce solidification expansion (it is possible to create a wax pattern in advance, taking into account the shrinkage of titanium as a casting metal of 2 to 3%, Furthermore, if the de-rossing work is carried out carefully and over time, rough skin can be prevented, so it can be used even when the total amount of curing agent is less than 10% by weight.

Table 5゜Experiment Example 6゜The main material in the mold material is 80% by weight, and the hardening agent is 2% by weight.
0% is vacuum kneaded with colloidal silica or water, the wax pattern is embedded, a mold is made as per legal procedures, and after hardening, it is fired at 1200°C in an electric furnace.
Furthermore, the molten titanium alloy (T
i-6A L-4V) was cast, and the results were as shown in Table 6. However, the amounts of silica and alumina are shown as the blending ratio of both, with the sum of the two as 100.
Further, in the 20% by weight of the curing agent, ammonium phosphate has a weight ratio of 12%, and magnesia has a weight ratio of 8%.

Table 6゜

Claims (1)

[Claims] 1) A mold material for casting pure titanium or a titanium alloy, comprising: a main material mainly composed of silica and alumina, and a hardening agent composed of a phosphate and a basic metal oxide. 2) The sum of silica and alumina as the main material is 90 to 50% by weight, and the phosphate as a hardening agent is 5 to 15% by weight.
The mold material for casting pure titanium or titanium alloy according to claim 1, which contains a basic metal oxide in an amount of 5 to 30% by weight. 3) The mold material for casting pure titanium or titanium alloy according to claim 1 or 2, wherein the sum of silica and alumina is 100 parts, and one of them is at least 10 parts. 4) The mold material for casting pure titanium or titanium alloy according to claim 3, wherein the sum of silica and alumina is 100 parts, one of which is at least 20 parts. 5) As silica, one or more types selected from silica stone, silica sand, granular silica sand, or cristobalite with a purity of 90
% or more of pure titanium or a titanium alloy casting mold material according to claims 1 to 4. 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 4. 7) The mold material for casting pure titanium or titanium alloy according to claims 1 to 4, wherein the phosphate is one selected from ammonium phosphate, potassium phosphate, and sodium phosphate. 8) The mold material for casting pure titanium or titanium alloy according to claims 1 to 4, wherein the basic metal oxide is 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. 10) Silica 10-82% by weight, alumina 10-82% by weight, phosphate 5-15% by weight, basic metal oxide 5-5% by weight
30% by weight was kneaded with colloidal silica, and after curing 10% by weight was mixed with colloidal silica.
Sintered at 00℃ or higher, mullite, spinel,
A method for producing a mold for casting pure titanium or a titanium alloy, which is formed by producing one or more refractory structures of cordierite.