JPH0628774B2 - Casting mold - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to active metals such as titanium and zirconium, alloys thereof (hereinafter, alloys may be simply referred to as metals in the present specification), chromium, vanadium and the like. The present invention relates to a mold suitable for casting a high melting point metal.

Prior art and prior art Since the calcia refractory is thermodynamically stable at high temperatures and has a unique refining action, the present inventors applied it to the melting of various refractory metals and highly active metals. It is becoming clear that you will get it.

The present inventor has proposed the following melting method.

In a molten chromium or chromium-based alloy in a container whose inner surface is composed of calcia-based furnace material, of high-purity chromium or chromium-based alloy characterized by allowing aluminum and lanthanum to exist under a vacuum or an Alcon atmosphere Production method (Japanese Patent Application No. 60-225450) Production of high-purity chromium characterized in that a rare earth element is allowed to exist in a molten chromium in a container whose inner surface is made of calcia furnace material under vacuum or argon atmosphere. Method (Japanese Patent Application No. 60-64307) According to such a melting method, it is possible to easily carry out melting of a highly active and / or high melting point metal, which was difficult to melt by the conventional method. Moreover, the obtained molten alloy is extremely clean.

In order to obtain a highly clean cast body, it is necessary to melt a highly clean metal melt and use a mold that does not contaminate the melt. Conventionally, as casting molds for titanium or zirconium metals (including alloys) that are active metals, there are known lamb type, investment type, water-cooled copper type, sand type (using zircon sand, olivine sand, etc.). . The lamdo type has graphite powder as an aggregate and is molded and dried with a carbon-based or resin-based binder and then baked. The investment type uses tungsten in a slurry referred to as a tungsten powder coating mold, uses a metallic binder, and a combination of an oxide-based slurry called an oxide mold and an oxide binder, and There are three types of graphite molds in which graphite-based slurry is solidified with a binder containing carbon.

As a titanium or titanium alloy template material, pure magnesia or a magnesia template material containing magnesia as a main component or an aggregate containing magnesia as a main component, to which a hardening accelerator such as a hydrogen carbonate of an alkali metal or aluminum powder was added. Template materials are also known (Japanese Patent Publication No. 58-5749,
JP-A-59-218237).

[Problems to be Solved by the Invention] However, when an active metal is cast into these molds, a reaction occurs with the mold material, and in the case of the graphite mold material, carbon, and in the magnesia or zirconia material, In the case of a mold, oxygen contamination occurs and the casting surface is contaminated. In addition, among the investment type, the oxide binder type has the penetration of not only oxygen but also nitrogen. Such contamination of the surface of the casting surface requires a step of removing the contamination layer on the surface of the casting, which makes the casting step extremely complicated. Further, in the casting method using a water-cooled copper mold, the mold is expensive and there is a risk of water leakage and other problems.

Furthermore, in molds such as oxide-based or graphite-based molds other than the water-cooled copper mold, since the thermal conductivity is low, shrinkage cavities are likely to occur in the center of the casting, and the casting yield is poor. In addition, since all of these oxide-based or graphite-based molds are dense, they have low thermal shock resistance, are prone to cracking, have poor durability, and are not suitable for repeated use of mold materials. There was such a problem.

[Means and Actions for Solving Problems] The mold of the present invention is entirely composed of a calcia material containing 40% by weight or more of CaO and 0.1 to 8% by weight of a halide. Characterize.

[Function] The mold of the present invention has a high melting point and / or a high melting point because it is a calcia substance that is thermodynamically stable at high temperature.
Alternatively, it is possible to easily perform casting of a highly active metal, and it is possible to obtain a casting with no contamination on the surface of the casting surface. Further, since the mold of the present invention contains a halide, the surface of the mold is smooth and therefore a smooth casting surface can be obtained.

In addition, the presence of halide facilitates firing,
Also, the moldability can be improved.

The present invention will be described in more detail below.

The template of the present invention is calcia. As described above, calcia has a high melting point and is thermodynamically stable even at high temperatures. Since the stability and heat resistance of the template of the present invention increase as the content of CaO increases, the template of the present invention contains C
The content of aO is at least 40% by weight (hereinafter,% means% by weight unless otherwise specified), preferably 70% or more and particularly 80% or more.

The template of the present invention contains a halide in addition to CaO. Examples of halides include fluorides and chlorides of alkali metals, alkaline earth metals and lead, and double salts containing them. Specifically, for example, CaF ₂ , MgF
₂ , BaF ₂ , SrF ₂ , NaF, LiF, KF, Pb
F ₂ , CsF, Na ₃ AlF ₆ , CaCl ₂ , MgCl
₂ , NaCl, KCl and the like.

Many of these halides have much higher digestion resistance than CaO, and also have a low melting point, so in addition to improving the hydration resistance due to the presence of themselves, they promote the sintering of the green body during firing. However, it has the effect of increasing the compactness of the sintered body structure, and these effects are superimposed to give the mold excellent hydration resistance. In addition, the strength of the obtained mold is remarkably improved by the sintering promoting action. It should be noted that a large amount of the halide is present at the grain boundaries, and the layer containing a large amount of the halide encloses the CaO particles, which is also considered to improve the hydration resistance of the template. The content of this halide is 8% or less, preferably 5% or less, because if the amount of addition is too large, the fire resistance of the mold is lowered.
Further, as a matter of course, if the addition amount is too small, the above-mentioned effects cannot be obtained, so 0.1% or more, preferably 0.3
The content rate is not less than%.

Further, the template of the present invention may include oxides, carbides, and nitrides as substances other than CaO. Specific examples of the oxide include magnesia (MaO) and zirconia (Zr).
Those having a high melting point such as O ₂ ) are preferable. Examples of carbides and nitrides include silicon carbide, silicon nitride, and aluminum nitride.

As a raw material used for producing the calcia mold, limestone, calcined or fully calcined lime, dead calcined lime, electrofused calcia dissolved in an arc furnace, calcium hydroxide, etc. are also used. obtain. Further, CaO-containing minerals such as ralnite, melwinite, anorthite and dolomite may be used.

In order to produce the mold of the present invention, such a calcia material, a halide, and optionally the above oxide,
One or two or more of carbides and nitrides are used together as a main raw material. Then, if necessary, an appropriate binder is added to this main raw material, and molding and firing are performed to form a mold.

A non-aqueous binder is used as this binder.

The non-aqueous binder may be either liquid or solid. As the liquid type, alcohol (monohydric or polyhydric alcohol) in which anhydrous calcium chloride or mastic rubber is dissolved, oleic acid dissolved in toluene, oleic acid dissolved in alcohol, oil It is a non-aqueous liquid that does not digest calcia, such as mineral oil, animal oil, vegetable oil, etc., although oleic acid dissolved in, carbon tetrachloride dissolved in beeswax, isobutyl acetate, etc. are preferable. Anything can be used.

As the solid binder, polyethylene, polypropylene, cellulose acetate, acrylic resin, thermoplastic resin such as polyvinyl alcohol, thermosetting resin such as novolac, paraffin or the like can be preferably used, but imparts moldability. Other materials may also be used.

As the molding method, various methods such as mold molding, slip casting, rubber pressing, injection molding, warm pressing, stamping and the like are used.

Note that hot press molding may be performed without using the binder or using a small amount of the binder.

The molded body or stamped mold is optionally dried, and then preferably calcined at a temperature lower than the main-baking temperature, and then main-baked and sintered. This firing temperature is 900
Above 1200C, 1200-1800C is especially suitable. The firing atmosphere may be an air atmosphere, but may be another atmosphere.

High melting point and / or highly active metals can be easily cast using the mold of the present invention. In the case of a refractory metal, for example, a pure metal such as chromium or vanadium, or an alloy containing a large amount thereof, one having a high CaO content, for example, one containing 80% by weight or more of CaO is suitable as a template. Also,
Also when casting a highly active pure metal such as titanium or zirconium or an alloy containing a large amount thereof, it is preferable to use a mold having a high CaO content.

The high melting point and highly active metal elements constituting the metal suitable for casting with the mold of the present invention include the following, and the alloy thereof is one or more of these elements. Some include. Lanthanide elements such as Sc, Y, La, Ce and Pr having atomic numbers 58 to 71, T
i, Zr, Hf, V, Nb, Ta, Cr, Mo, W, M
n, Tc, Re, Ru, Os, Co, Ni, Rh, P
d, Ir, Pt.

The mold of the present invention can be applied not only to the outer mold but also to the inner mold called a core. Further, since CaO has a digestibility, the template of the present invention can be removed by utilizing this digestibility.

For casting in the present invention, the atmosphere is preferably a vacuum or an inert gas atmosphere such as argon.

[Examples] Examples will be described below, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

Example 1 85 parts by weight of electrofused calcia (CaO purity 99%) crushed and classified to 0.2 mm or less, reagent grade CaF ₂
5 parts by weight and 10 parts by weight of a magnesia clinker pulverized to 0.2 mm or less were mixed to prepare 100 parts by weight of raw material powder. Further, 10 parts by weight of anhydrous calcium chloride dissolved in ethyl alcohol to a concentration of 4% was prepared. These were mixed and mold-molded.

After drying this molded body at 100 ° C. for 1 hour, 950 ° C. ×
Sintering was performed by firing for 3 hours. The firing was performed in an air atmosphere. The sintered body thus obtained is the first
It had the shape and dimensions shown in the figure.

Pure Ti was cast using this mold. The atmosphere during casting is Ar 1 atm, and the temperature of the molten metal during casting is 1700 ° C. Table 1 shows the results of chemical analysis of O and N on the surface of the casting after the molten metal was cast into the mold and solidified.

Example 2 A mold and casting using the same were performed in the same manner as in Example 1 except that the conditions were changed as in (a) to (f) below.

(A) The ingredients are mixed as follows.

Dolomite clinker (CaO 64.3%, MgO 30.
9%, Fe ₂ O ₃ 2.3%, SiO ₂ 1.8%, Al ₂
90 parts by weight of O ₃ 0.4%) crushed and classified to 0.3 mm or less, 3 parts by weight of CaCl _{2, and} 10 parts by weight of limestone crushed to 1 mm or less.

(B) An alcohol solution of calcium chloride (5%) is used as a binder.

(C) The mixing ratio of the solid raw material and the binder is 100: 1.
Set to 0.

(D) The conditions for the main firing are 1100 ° C. × 3 hours.

(E) Cast alloy is made of Zr 60% and Co 40%.

(F) The temperature of the molten metal during casting is set to 1550 ° C.

Table 1 shows the chemical analysis results of the surface of the obtained casting.

Example 3 A mold was produced and casting was performed in the same manner as in Example 1 except that the conditions were changed as described in (a) to (f) below.

(A) The ingredients are mixed as follows.

Commercial quicklime (CaO 98.0%, SiO ₂ 0.08
%) Was crushed and classified to 0.1 mm or less, 85 parts by weight, MgCl ₂ 5 parts by weight, and dolomite clinker (same as in Example 2) was crushed to 0.1 mm or less, 10 parts by weight.

(B) An alcohol solution of calcium chloride (5%) is used as a binder.

(C) The mixing ratio of the solid raw material and the binder is 100: 1.
Set to 0.

(D) The conditions for the main firing are 1350 ° C. × 3 hours.

(E) The casting alloy is Ni 68% and La 32%.

(F) The temperature of the molten metal during casting is set to 1400 ° C.

Table 1 shows the chemical analysis results of the surface of the obtained casting.

Comparative Example 1 A mold and casting using the same were performed in the same manner as in Example 1 except that the conditions were changed as described in (a) to (d) below.

(Ii) The raw material is only commercially available silica sand powder (SiO ₂ 98%).

(B) Water glass was used as a binder and cured with CO ₂ gas.

(C) The mixing ratio of the solid raw material and the binder is 100: 5.
And

Comparative Example 2 In Example 2, manufacture of a mold and casting using the same were performed in the same manner except that the commercially available silica sand was used as the raw material of the mold.

Table 1 shows the chemical analysis results of the surface of the obtained casting.

Comparative Example 3 In Example 3, the production of a mold and the casting using the same were performed in the same manner except that the commercially available silica sand was used as the raw material of the mold.

Table 1 shows the chemical analysis results of the surface of the obtained casting.

[Effects of the Invention] As is clear from the above description, according to the present invention, it is possible to easily cast a highly active metal, a high melting point metal, or an alloy thereof. The obtained casting becomes highly clean without contamination with C, O, N, etc., and no post-treatment such as removal of the cast skin contamination layer is required. Further, the mold material of the present invention is inexpensive and can be recovered after casting and repeatedly molded and used, and the casting cost can be significantly reduced.

[Brief description of drawings]

 FIG. 1 is a dimensional diagram showing the shape of the mold.

Claims (1)

[Claims] 1. A mold which is entirely made of a calcia refractory material containing 40% by weight or more of CaO and 0.1 to 8% by weight of a halide.