JP2016079072A - Producing method of ceramics molding and producing method of casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve dimensional accuracy and surface property of a final molding and to reduce time for degreasing in a producing method of a ceramics molding.SOLUTION: A producing method of a ceramics molding includes: a molding process of solidifying a mixture containing ceramic powder and binder, and forming a primary molding; a setter arranging step of arranging the primary molding on a setter 2 having a concave part corresponding to the shape of the primary molding; a covering step of covering around the primary molding 1 arranged on the setter 2 with powder 5; and a calcination step of forming a final molding by burning the primary molding in the covered state.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a method for manufacturing a ceramic molded body and a method for manufacturing a cast body.

  For example, ceramic molded bodies such as ceramic cores used for casting of gas turbine rotor blades / stator blades are formed by precision casting because high precision is required. In such a precision casting method, a ceramic powder to which a binder is added is poured into a mold and injection molded to form a primary molded body (green mold), and this primary molded body is degreased and fired in general. Is.

  As a method for firing a ceramic molded body, a setter method is known in which a primary molded body is placed and fired on a setter formed in a shape corresponding to the shape of the primary molded body (see, for example, Patent Document 1). The setter method is excellent in that it is supported by a setter corresponding to the shape of the primary molded body and firing occurs, so that the dimensional variation is small and the yield rate is high.

  Further, as a method for firing a ceramic molded body, a kaolin system in which a primary molded body is embedded in an embedding powder such as kaolin powder and fired is also known (see Patent Document 2). The kaolin method is excellent in that the degreasing time can be shortened and degreasing is easy.

JP 2003-176181 A JP 63-100074 A

By the way, when baking using the setter method, there is a problem that degreasing has a long time and it is difficult to degrease a thick portion having a large amount of binder such as wax.
Moreover, when baking using the said kaolin system, there exists a subject that the dimensional dispersion | variation of a final molded object becomes large by factors, such as a pressure density of a filling powder.

  An object of the present invention is to provide a ceramic molded body manufacturing method and a cast body manufacturing method capable of improving the dimensional accuracy and surface properties of the final molded body and reducing the time required for degreasing. .

  According to the first aspect of the present invention, a method for producing a ceramic molded body includes a molding step of solidifying a mixture containing ceramic powder and a binder to form a primary molded body, and the primary molded body, A setter arrangement step of arranging on a setter having a recess corresponding to the shape of the molded body, a coating step of covering the periphery of the primary molded body arranged on the setter with powder, and the primary molding in a coated state A firing step of firing the body to form a final molded body.

  According to such a configuration, since the primary molded body is placed on the setter and fired, deformation of the primary molded body is suppressed by the setter, and the dimensional accuracy of the final molded body can be improved. Moreover, since oxygen is interrupted by the powder, a low oxygen atmosphere is obtained, and the time required for degreasing can be shortened. In addition, since the powder load is uniformly applied to the primary molded body, the dimensional accuracy of the surface can be improved. Further, since oxygen is blocked by the powder, the binder hardly burns on the surface of the primary molded body, and the surface properties of the final molded body can be improved.

  In the method for producing a ceramic molded body, silica or a composite oxide containing silica may be used as the powder.

  According to such a configuration, silica or silica-containing composite oxide absorbs excess binder, while silica or silica-containing composite oxide hardly reacts with the ceramic, so that the final molded body is swollen or cracked, Roughness is less likely to occur, and the surface properties of the final molded body can be improved.

  In the method for manufacturing a ceramic molded body, a cover for preventing oxygen from flowing into the space around the powder may be provided.

  According to such a configuration, since the inflow of oxygen to the primary molded body is further suppressed, the time required for degreasing can be further shortened.

In the method for manufacturing a ceramic molded body, the powder may be formed of a spherical body.
According to such a configuration, the powder filling rate in the coating step can be improved. Thereby, the force which restrains a primary molded object increases, and the dimensional accuracy of a final molded object can be improved.

  According to the second aspect of the present invention, a method for manufacturing a cast body includes a core forming step of forming a core by the method for manufacturing a ceramic formed body according to any one of the above, and the formed core, And a casting step of forming a cast body by placing the mold inside the mold.

  According to such a configuration, it is possible to produce a cast body with less surface defects and excellent smoothness in a shorter time.

  According to the present invention, when manufacturing a ceramic molded body, it is possible to improve the dimensional accuracy and surface properties of the final molded body and reduce the time required for degreasing.

It is a flowchart explaining the process of the manufacturing method of the ceramic molded body in embodiment of this invention. It is a perspective view explaining the setter arrangement | positioning process in the manufacturing method of the ceramic molded body of embodiment of this invention. It is a perspective view explaining the covering process in the manufacturing method of the ceramic fabrication object of the embodiment of the present invention. It is a perspective view explaining the oxygen interruption | blocking process in the manufacturing method of the ceramic molded body of embodiment of this invention. It is a graph which shows the relationship between the temperature increase rate and time in the baking process of the manufacturing method of the ceramic molded body of embodiment of this invention. It is a top view explaining the manufacturing method of the ceramic molded body of the modification of embodiment of this invention.

  Hereinafter, the manufacturing method of the ceramic molded body of embodiment of this invention is demonstrated in detail with reference to drawings. In the following description, a ceramic molded body is manufactured using a core (core) used in the manufacture of a cast body such as a turbine stationary blade / blade, an aircraft engine rotor blade / vane, etc. I will explain.

For example, since a moving blade of a gas turbine is exposed to a high-temperature working gas, a cooling medium is allowed to flow inside to cool the gas turbine moving blade to keep the temperature applied to the gas turbine moving blade lower. Is adopted.
An internal cooling structure is provided in the gas turbine rotor blade in order to allow the cooling medium to flow inside. When manufacturing a gas turbine rotor blade having an internal cooling structure, a core having the same shape as the flow path of the cooling medium is disposed, and the core is removed after casting.

  Specifically, in the method for producing a cast body, after solidifying the molten metal supplied between the step of obtaining the core produced by this method and the mold and the core installed therein, Obtaining a cast body having a hollow portion by removing the core. That is, in the casting manufacturing method, after the molten metal is supplied to the mold, the core is removed to manufacture a casting having a hollow portion corresponding to the core.

  As shown in FIG. 1, the ceramic molded body manufacturing method S <b> 1 in the present embodiment includes a molding step S <b> 10 that forms an unfired primary molded body, a setter arrangement step S <b> 20 that arranges the primary molded body on a setter, Curing step S30 for carrying out the ring, coating step S40 for covering the primary molded body arranged on the setter with powder, oxygen blocking step S50 for covering the primary molded body and the powder, and firing of the primary molded body And firing step S60.

The molding step S10 is a step of forming an unfired primary molded body by injection molding ceramic powder (silica powder) using a binder. Specifically, a ceramic powder and a binder are mixed to form a mixture, and the mixture is injected into a mold and then solidified to form a primary molded body.
As the ceramic powder, fused silica powder or the like can be used.
As the binder, paraffin, plastic polymer, wax and a mixture thereof can be used.

FIG. 2 is a perspective view for explaining the setter arrangement step S20 in the ceramic molded body manufacturing method S1. As shown in FIG. 2, the setter arrangement step S <b> 20 is a step of arranging the primary molded body 1 formed in the molding step S <b> 10 on the setter 2 having the molded body receiving portion 4 corresponding to the shape of the primary molded body 1. is there.
The setter 2 has a solid rectangular parallelepiped body portion 3 and a plurality of molded body receiving portions 4 formed on the upper surface of the body portion 3. The setter 2 is made of a highly rigid material such as metal or engineering plastic.

  The molded body receiving portion 4 has a shape corresponding to the first surface 1a of the primary molded body 1 molded in the molding step S10. That is, the molded body receiving portion 4 is a concave portion in which no gap is generated between the setter 2 and the primary molded body 1 when the primary molded body 1 is arranged on the setter 2 so that the first surface 1a is on the lower side. It is made into the shape which has.

  The curing step S30 is a step in which the primary molded body 1 is heated while being placed on the setter 2. In the curing step S <b> 30, for example, the setter 2 is heated at a heating rate of 20 ° C./hour to soften the primary molded body 1, thereby causing the primary molded body 1 to follow the setter 2.

FIG. 3 is a perspective view for explaining a covering step S40 in the ceramic molded body manufacturing method S1. As shown in FIG. 3, the covering step S <b> 40 is a step of covering the periphery of the primary molded body 1 arranged on the setter 2 using the powder 5. Specifically, the setter 2 is arranged in the box 7 whose upper part is opened, and the powder 5 is filled in the box 7. At this time, filling is performed without pressing the powder 5 so that a gap is generated between the granular powders 5.
In covering the primary compact 1, the powder 5 may be placed on the primary compact 1 so as to cover at least the entire primary compact 1 without using the box 7.

As the powder 5 used in the coating step S40, silica (silicon dioxide, SiO ₂ ) alone or a composite oxide containing silica is preferable. Examples of the composite oxide containing silica include zircon (ZrSiO ₄ ), kaolin (kaolinite, Al ₄ Si ₄ O ₁₀ (OH) ₈ ), mullite (Al ₆ O ₁₃ Si ₂ ), and the like.
Further, the particle size of the powder 5 is preferably a predetermined particle size having appropriate fluidity. Furthermore, the powder 5 is preferably a spherical body. Specifically, the average particle diameter of the grains constituting the powder 5 is 20 μm to 60 μm.

FIG. 4 is a perspective view for explaining an oxygen blocking step S50 in the ceramic molded body manufacturing method S1. As shown in FIG. 4, the oxygen blocking step S50 is a step of providing the cover 8 at the opening of the box 7 used in the covering step S40. The cover 8 does not seal the space in the box 7, and the cover 8 only needs to be placed on the top of the box 7. Thereby, a slight gap is generated between the cover 8 and the box 7.
When the box body 7 is not used, for example, the lid may be covered by covering the primary molded body 1 with the box body 7 opened at the bottom.

FIG. 5 is a graph showing the relationship between the rate of temperature increase and time in the firing step S60 of the ceramic molded body manufacturing method S1. The firing step S60 is a step of firing (baking, sintering) by heating the primary molded body 1 supported by the setter 2 and covered with the powder 5.
Specifically, as shown by the solid line in FIG. 5, the primary molded body 1 is heated to the maximum temperature T, and the ceramic powders are bonded to advance and promote densification. The maximum temperature T is preferably 1,100 ° C to 1,300 ° C.
At this time, vapor generated by the evaporation of the binder leaks from the gap between the cover 8 and the box 7. When the binder vapor leaks from the gap, the outside air (oxygen) does not flow into the box 7 from the gap.

  Next, the final molded body is cooled. At this time, in order to prevent shrinkage of the final molded body, the temperature is lowered at a temperature lowering rate suitable for the ceramic molded body without rapid cooling.

(Example)
Using the plurality of types of powders 5, the above-described ceramic molded body production method S1 was carried out.
As raw materials for the powder 5, alumina (aluminum oxide, Al ₂ O ₃ ), silica (SiO ₂ ), zircon (ZrSiO ₄ ), kaolin (Al ₄ Si ₄ O ₁₀ (OH) ₈ ), mullite (Al ₆ O _13). Si ₂ ) was used. Of these, alumina is an oxide that does not contain silica, and zircon, kaolin, and mullite are complex oxides that contain silica.

Here, the effect of the present embodiment will be described by way of examples. When the compact covering step S40 is performed using alumina powder, that is, powder not containing silica, alumina constitutes the primary compact 1. The alumina adhered to the primary molded body 1 by reacting with the ceramic. That is, a problem remained in the surface properties of the primary molded body 1.
On the other hand, when the molded body covering step S40 is performed using the powder 5 formed of silica or a composite oxide containing silica, the powder 5 does not adhere to the primary molded body 1 and surface defects are present. There were few ceramic molded bodies excellent in smoothness.

Moreover, in FIG. 5, the dotted line has shown the relationship between the temperature increase rate and time in the baking process S60 of the conventional setter method, and the continuous line has the relationship between the temperature increase rate and time in the baking process S60 of this embodiment. Is shown.
In the setter method, the primary molded body 1 is disposed between a lower setter similar to the setter 2 of the present embodiment and an upper setter having a shape corresponding to the surface opposite to the first surface 1a of the primary molded body 1. In this method, firing is performed.

As shown by the dotted line in FIG. 5, in the case of the conventional setter method, the temperature is gradually increased in order to remove moisture, binder, and the like from the mixture. That is, a long time is required for the degreasing process until the maximum temperature T is reached.
On the other hand, as shown by the solid line in FIG. 5, the degreasing process up to the maximum temperature T can be shortened in the ceramic molded body manufacturing method S <b> 1 of the present embodiment. That is, in the ceramic molded body manufacturing method S1 of the present embodiment, the powder 5 covering the primary molded body 1 can be fired in a low oxygen atmosphere, so that degreasing can be performed in a short time.

According to the embodiment, since the primary molded body 1 is placed on the setter 2 and fired, deformation of the primary molded body 1 is suppressed by the setter 2 and the dimensional accuracy of the final molded body can be improved. Moreover, since oxygen is interrupted | blocked by the powder 5, it becomes a low-oxygen atmosphere and can shorten the time required for degreasing.
Moreover, since the load of the powder 5 is uniformly applied to the primary molded body 1, the dimensional accuracy of the surface can be improved. Moreover, since oxygen is interrupted | blocked by the powder 5, a binder becomes difficult to burn on the surface of the primary molded object 1, and the surface property of the final molded object can be improved. That is, a ceramic molded body having few surface defects and excellent smoothness can be produced.

  In addition, silica or a composite oxide containing silica absorbs an excess binder, while silica or a composite oxide containing silica hardly reacts with the ceramic, so that the final molded body is less likely to be swollen, cracked or roughened. The surface property of the final molded body can be improved.

In addition, by providing the cover 8 that prevents the inflow of oxygen in the peripheral space of the powder 5, the inflow of oxygen into the primary molded body 1 is further suppressed, so that the time required for degreasing can be further shortened.
Furthermore, by making the powder 5 spherical, the filling rate of the powder 5 in the coating step S40 can be improved. Thereby, the force which restrains the primary molded object 1 increases, and the dimensional accuracy of a final molded object can be improved.

The ceramic molded body manufacturing method S1 of the present embodiment is optimal for manufacturing precision casting cores used in the manufacture of castings such as turbine stator blades / blades, aircraft engine rotor blades / vanes, etc. It is.
The manufacturing method of the cast body using such a core includes a step of acquiring the core manufactured by the manufacturing method S1 of the ceramic molded body of the above embodiment (core forming step), a mold, and an interior thereof. After solidifying the molten metal supplied between the core and the core to be removed, the step of obtaining a cast body having a hollow portion by removing the core (casting step). That is, in the casting manufacturing method, after the molten metal is supplied to the mold, the core is removed to manufacture a casting having a hollow portion corresponding to the core.

Next, the manufacturing method S1 of the ceramic molded body of the modification of this embodiment is demonstrated.
As shown in FIG. 6, the ceramic molded body manufacturing method S <b> 1 according to the present modification is characterized in that the setter 2 </ b> B has a trapezoidal shape in plan view.
The shape of the setter 2B of the present embodiment in plan view has a length in one direction and a width W2 on the second side opposite to the first side than the width W1 on the first side in the longitudinal direction. The shape corresponds to the shape of the wide ceramic molded body C. Specifically, the trapezoidal setter 2B includes upper and lower bases 2a and 2b having lengths corresponding to the first and second sides of the ceramic molded body having the above-described shape, and the upper and lower bases 2a and 2b. It is an isosceles trapezoid shape which has a pair of leg 2c which connects the bottom 2b.
As shown in FIG. 6, the plurality of setters 2 </ b> B of the present modification are arranged such that the longitudinal directions are aligned and the longitudinal directions of adjacent setters 2 </ b> B are opposite.

  According to this modification, when a plurality of setters 2B are fired simultaneously, firing can be performed with less installation space.

DESCRIPTION OF SYMBOLS 1 Primary molded object 1a 1st surface 2,2B Setter 3 Main-body part 4 Molded object receiving part 5 Powder 7 Box 8 Cover S1 Manufacturing method of ceramic molded object S10 Molding process S20 Setter arrangement process S30 Curing process S40 Covering process S50 Oxygen blocking process S60 Firing process T Maximum temperature

Claims (5)

A molding step of solidifying a mixture containing ceramic powder and a binder to form a primary molded body;
A setter arrangement step of arranging the primary molded body on a setter having a recess corresponding to the shape of the primary molded body;
A covering step of covering the periphery of the primary molded body arranged on the setter with powder;
A firing step of firing the primary compact in a coated state to form a final compact, and a method for producing a ceramic compact.   The method for producing a ceramic formed body according to claim 1, wherein silica or a composite oxide containing silica is used as the powder.   The method for producing a ceramic molded body according to claim 1 or 2, wherein a cover for preventing inflow of oxygen is provided in a peripheral space of the powder.   The method for producing a ceramic molded body according to any one of claims 1 to 3, wherein the powder is formed of a spherical body. A core forming step of forming a core by the method for manufacturing a ceramic formed body according to any one of claims 1 to 4,
A casting process comprising: forming the cast core by placing the molded core in a mold and casting the core.

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