JPH0811275B2 - Method for manufacturing ceramic shell mold - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a mold for precision casting of a high melting point active metal such as titanium or titanium alloy.

[0002]

2. Description of the Related Art A high melting point active metal material such as titanium or a titanium alloy is liable to be contaminated in a cast product by a reaction with a mold refractory and dissociation of the refractory itself in a molten state. For this reason, conventionally, refractory materials such as graphite, yttria, zirconia, calcia, and magnesia, which have heat resistance at high temperatures and low reactivity with titanium, have been conventionally used as template materials for titanium or titanium alloys.

Templates of titanium or titanium alloys are roughly classified into those by the Radom graphite method and the lost wax method. The former uses graphite as the main aggregate as a refractory material,
Using a carbon-based or resin-based binder, graphite particles are filled on a model, and after solidification, the model is demolded, dried, and then baked to form a mold.

The latter is a ceramic shell mold that uses an oxide refractory such as yttria as a main aggregate as a refractory material, and uses an ethyl silicate hydrolyzate, an aqueous or anhydrous colloidal silica sol, an alumina sol or the like as an oxide binder. Is used. A mold using oxide refractory forms a wax pattern similar to the cast product, dips this in oxide refractory slurry to form a slurry layer, and oxidizes the slurry layer. Particles of refractory material are sprinkled to adhere (stucco), and this coating operation is repeated several times to obtain a shell layer thickness of 6 to 1
Use a 0 mm ceramic shell mold. Then, the mold is heated by autoclaving, shock heating, or the like to eliminate the wax pattern in the mold.

Particularly, in the ceramic shell mold in the lost wax method, since the mold thickness is relatively thin as 6 to 10 mm, coating, heat shock, molten metal weight, etc. are caused in each step of coating, dewaxing, firing and casting. It is necessary to have a mold strength that can withstand. For this reason, an oxide binder such as an ethyl silicate hydrolyzate, an aqueous or anhydrous colloidal silica sol, and an alumina sol is generally used.

[0006]

However, in the graphite mold, a reaction layer of the titanium carbide reacts with the molten metal and the mold material in contact therewith to form a reaction layer of titanium carbide on the casting surface of the casting. Further, in the ceramic shell mold, since the binder contains silica or alumina as described above, these refractories are present in the primary coat layer, and when they react with molten titanium, oxygen in the refractory Dissociates and oxidizes titanium, contaminating the casting surface.

Therefore, when these mold materials are used, a step of removing the contaminated layer generated by the reaction with the molten metal such as titanium or titanium alloy is required, which is very expensive and time-consuming. The present invention seeks to provide a ceramic shell mold that suppresses the reaction of titanium or titanium alloy with the molten metal.

[0008]

SUMMARY OF THE INVENTION The present invention is stabilized Jill Konia in a solution of the polycarbonate dissolved in an organic solvent
(Calcia, yttria, magnesia, etc. in zirconia
Added to to produce a solid solution, it refers to stabilized. )
After immersing the wax pattern in the slurry prepared by blending, the primary coat layer to which the refractory particles are adhered is formed, and the backup shell layer made of the shell mold for precision casting is formed on the outside thereof, and the wax pattern is formed. The method is for producing a ceramic shell mold, which comprises firing after removing the.

The backup shell layer is made of mullite, alumina, zircon sand, fused silica, etc. as a refractory material, and ethyl silicate hydrolyzed liquid, a water-based or anhydrous solvent-based colloidal silica sol as a refractory material according to a usual ceramic shell mold manufacturing method. And the like are used for molding.

[0010]

The slurry composed of the polycarbonate solution dissolved in the organic solvent and the refractory powder strengthens the primary coat layer on the wax pattern as the organic solvent vaporizes and binds the refractory particles attached to the layer. Let The primary coat layer thus formed prevents deformation and cracking of the mold in the mold coating step and the dewaxing step due to the water resistance, heat resistance and mechanical strength of the resin. In particular, since the silica-based and alumina-based binders are not used in the primary coat layer, the reaction with the molten titanium is suppressed, and oxygen can be reduced. Therefore, according to the present invention, a sound titanium or titanium alloy casting can be obtained.

In the method for producing a ceramic shell mold of the present invention, the organic solvent that dissolves the binder of the slurry for primary coating includes a ketone type, an aromatic type,
Examples include ester-based, ether-based, phenol-based, and chlorine-based. In particular, chloroform is used as chloroform, chlorobenzene, ether is used as tetrahydrofuran, dioxane, and phenol is used as cresol. Tetrahydrofuran is preferable in terms of solubility and work environment safety.

As the binder, in addition to polycarbonate, ABS resin, polyamide, acrylic resin, polyether sulfone and the like can be mentioned. Among these resin materials, thermal deformation occurs in the mold during the dewaxing process. Some have poor solubility of the binder in the organic solvent. In the present invention, polycarbonate is preferably used as the binder.

Specific examples of the present invention will be given below to describe in more detail.

[0014]

[Examples] Three examples of producing a slurry will be shown. 60 g of polycarbonate (molecular weight≈50000) was mixed with 888 g of tetrahydrofuran and dissolved at 60 ° C. with stirring to obtain a binder solution. To 400 g of this solution, 1200 g of calcia-stabilized zirconia having a purity of 92.0% and passing through 350 mesh of 60 to 80% was added to prepare a slurry (Preparation Example 1).

A slurry was prepared by adding 1260 g of yttria-stabilized zirconia having a 325 mesh passage of 60 to 80% to 400 g of the polycarbonate solution of the slurry preparation example 1 (preparation example 2). To 400 g of the polycarbonate solution of Slurry Preparation Example 1, 300 to 40% of electromelted calcia powder having a mesh of 40 to 60% (purity: 99.7) was used.
%) 1100 g to prepare a slurry (Preparation Example 3).

Next, an example of producing a ceramic shell mold using the slurry produced in the above example of production will be shown. The wax pattern was dipped in the electrofused calcia slurry prepared in Slurry Preparation Example 3, and then the purity was set to 9 before the solvent was vaporized.
2% and calcia particles having a particle size of 0.2 to 0.4 mm were adhered to form a primary coat layer. Then, coating was performed based on a usual ceramic shell mold manufacturing method to form a backup coat layer. Anhydrous colloidal silica was used as the binder, mullite flour was used as the refractory for the slurry at this time, and alumina was used as the refractory for the stucco.

After dewaxing the mold thus formed on the wax pattern in a furnace at 1000 ° C., it is baked at 1400 ° C. for 1 hour in a baking furnace so that the primary coat layer is calcia. A ceramic shell mold for casting titanium or high titanium alloys consisting of stabilized zirconia was obtained. Pure titanium was cast using this mold. The atmosphere during casting was 1 atm of argon, and the temperature of the molten metal was about 1700 ° C. After cooling the furnace, the ceramic shell mold was removed from the casting, and the micro Vickers hardness of the product was measured. As a result, the casting surface had 198 Hv and the portion 300 μm away from the casting surface had 119 Hv. Since the micro Vickers hardness of pure titanium is about 100 Hv, the casting surface of the cast product using the ceramic shell mold is good with almost no contamination layer.

[0018]

As described above, according to the present invention, a ceramic shell mold having a primary coat layer formed of a polycarbonate which is dissolved in an organic solvent and a slurry of a refractory material which is chemically stable at high temperature is provided. ,
Since the reaction with molten titanium is suppressed, it can be provided as a mold for casting titanium or titanium alloy.

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Watano Mizuno 150 Nikamicho, Takaoka City, Toyama Prefecture, Toyama Industrial Technology Center (56) Reference JP-A-3-8533 (JP, A) Japanese Patent Publication No. 54-22774 (JP, B2) Toyama Industrial Technology Center Research Report No. 4 (October 1, 1990) Announced on pages 37 and 38

Claims (1)

[Claims] [Claim 1 was dipped wax pattern in a slurry prepared by blending a stabilizing Jill Konia powder in a solution of the polycarbonate dissolved in an organic solvent, to form a primary coating layer sprinkle the refractory grains, A method for producing a ceramic shell mold, which comprises forming a backup shell layer made of a shell mold for precision casting on the outside thereof, then eliminating the wax pattern, and then calcining the mold.