JPH04173902A - Powder injection compacting sintering method - Google Patents

Abstract

PURPOSE:To easily execute powder injection compacting to make a product having shape of difficult-to-removal from die to obtain a sintered parts by injection powder containing binder into cavity in a die setting a core and removing the core after removing the obtd. green body from the die. CONSTITUTION:The injection compacting is executed to the powder, and after degreasing, this is sintered to obtain the sintered body. In the injection compacting and sintering method, the core is inserted into the prescribed position in the cavity in the die. This core is manufactured with the kind of material different from the material forming the product body, e.g. in the case of forming the product body with Ni-base heat resistant alloy, this is preferably used for thermosetting resin, etc. Successively, into the cavity in the die setting the above core, the powder imparted with fluidity with the binder is injected. The green body integrated with the core obtd. with this injection-compacting is released from the die. At the time of degreasing and sintering this released product from the die, the above core is removed to a large part thereof, and if necessary, by using salt bath, etc., the remaining core is dissolved and removed from the sintered product.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a powder injection molding and sintering method for molded articles having shapes that are difficult to demold.

(Prior art) In powder injection molding, fluidity is imparted to a powder material such as metal, ceramic, or cermet by wax or thermoplastic resin mixed as a binder, and the mixture is injected into a mold cavity. It is something.

As the demand for sintered parts using these powder materials increases in many advanced technology fields, sintered parts with complex shapes are required. In general, injection molding is more effective at producing complex shapes than press molding. However, even with injection molding, there are some shapes that are difficult or impossible to mold, and this tendency is particularly noticeable in the shape of the inside of the molded product.

Conventionally, for products with complex shapes that are difficult to mold by a single injection molding method, post-processing or a method of dividing the products and bonding them after molding has been used.

(Problem to be Solved by the Invention) However, the above-mentioned methods all have the problem of requiring a large number of man-hours and increasing costs. Furthermore, in the split molding method, there is also a problem in the bonding strength between the parts after the split molding.

The present invention aims to solve the above-mentioned problems, and proposes a method of manufacturing a sintered part by molding a product with a shape that is difficult to mold using conventional methods by a single injection molding process.

(Means for Solving the Problems) In order to achieve the above object, the present invention uses an injection molding method in which a core made of a material different from that of the molded product body is inserted into a mold cavity, a molding material is injected into the mold cavity, and a molding material is injected into the mold cavity. This invention provides a powder injection molding and sintering method characterized in that a green body integrated with a core is molded, and after demolding, a desired shape is expressed by disassembling or dissolving and removing the core.

Therefore, in the powder injection molding as described above, the present invention creates a core made of a material different from the material forming the molded product body, and places this core at a predetermined location in the mold cavity. A core insertion process in which the core is inserted and installed, an injection process in which powder imparted with fluidity by a binder is injected into the mold cavity in which the core is installed, and a green body obtained by being integrated with the core by injection molding. A powder injection molding sintering method characterized by having a demolding step of demolding from a mold to obtain a demolded product, and a core removal process of removing a core that is integrated inside the demolded product. This is the summary.

After the solidification of the green body, depending on the material composition of the core,
When decomposing and removing in the degreasing and sintering process, and when molded bodies and
The core removal process may be performed by degreasing and sintering the core integrally, and then dissolving and removing the core using, for example, an alkaline solution.

(Function) According to the powder injection molding and sintering method of the present invention, injection molding is performed using a core that expresses the inner shape, and the core is decomposed or removed after molding, so complex shapes that are difficult to mold can be fabricated. Even a molded article having the following properties can be obtained by one injection molding.

(Example) Next, a specific example of the method of the present invention will be described.

Example 1 - A blade for a gas turbine used in a high speed rotation state was manufactured. The blade in this embodiment is hollow inside for the purpose of preventing overheating.

This blade is made of a material that has excellent high-temperature strength, such as a Ni-based super super heat-resistant alloy (trade name: TNCO713C (manufactured by Inco Corporation)). The hollow portion as described above is created by a core, and the material of this core is preferably one that maintains the shape stability of the core when exposed to heat when obtaining the desired shape of the product by injection molding. In the examples, thermosetting resin was used.

A core with a shape corresponding to the hollow part when forming the target shape is created by, for example, injection molding or transfer molding, and the inside of the injection mold cavity is made into a shape corresponding to the outer shape of the target shape. It was installed in

Next, a sintered metal material obtained by blending the Ni-based super super heat-resistant alloy metal powder with a binder consisting of wax and a thermoplastic resin was injection molded, and a demolded product was obtained by a known method. This demolded product is in a state called a green body before being subjected to the degreasing and sintering steps. The green body including the resin core is solidified by the resin component in the binder with a strength sufficient to withstand a certain pressure while being cooled, and has shape retention properties.

Next, such a green body is heated and degreased, and most of the core forming the inner shape is decomposed and removed by heat in this heat degreasing step.

In the next sintering step, the core was completely removed to obtain a gas turbine blade having hollow portions of a predetermined shape at required internal locations.

Example 2 In manufacturing a gas turbine blade similar to Example 1, a core for creating a hollow portion provided in the blade was made of a ceramic material. The material used for this core was a fused silica ceramic material. This ceramic material was used as an aggregate, a binder consisting of a thermosetting resin and wax was blended, and the mixture was molded by transfer molding. Using the ceramic core thus obtained, a green body was obtained which had cores of the shape corresponding to the hollow part when forming the desired shape at the required locations by the same means as in Example 1. .

The green body in which the product part and the core were integrated was subjected to a degreasing treatment to remove the binder as it was, and then sintered in a furnace in a non-oxidizing atmosphere.

The core in which the ceramic material held in the blade was sintered was dissolved and removed from the sintered plate using a salt lotus or the like. Caustic potash or the like can be used as a solvent for dissolving the ceramic core. By dissolving and removing the core, a gas turbine blade having hollow portions of a predetermined shape at required internal locations was obtained.

In particular, in this Example 2, the demolded product after powder injection molding is in a state called a so-called green body, and at the same time,
The core contained in the demolded product is also in a state called a green body. Therefore, both the product part and the core have almost the same shrinkage rate during sintering, and almost no thermal stress is generated due to the difference in shrinkage rate between the two during the sintering process.
The precision of the product has improved, and the yield has also improved.

In this example, a blade for a gas turbine was produced, but it goes without saying that the present invention can be applied to the production of other general mechanical parts.

(Effects of the Invention) According to the powder injection molding and sintering method of the present invention, the desired molded product can be obtained by injection molding at a -degree level, so that the required man-hours are reduced and this contributes to improved productivity. In particular, when the green body is made into a green body in which a product part of the desired shape and a core are integrated, and the core is removed after degreasing and sintering, the product part and core shrink during sintering. Approximately the same rate improves product accuracy and yield.

Applicant: Komatsu Howmet Co., Ltd. -1 bow

Claims (1)

[Claims] 1. In a powder injection molding and sintering method that is performed through the stages of powder injection molding, degreasing, and sintering, a core is made of a material different from the material forming the molded product body. a core insertion step in which the core is inserted into a predetermined location within the mold cavity; an injection step in which powder imparted with fluidity by a binder is injected into the mold cavity in which the core is installed; A demolding process in which the green body obtained by being integrated with the core by injection molding is removed from the mold to produce a demolded product, and a core removal process in which the core that is integrated and present inside the demolded product is removed. A powder injection molding sintering method characterized by having a step. 2. The powder injection molding and sintering method according to claim 1, wherein the core removal step is performed by decomposing and removing the core in a degreasing and sintering step. 3. The powder injection molding and sintering method according to claim 1, wherein the core removal step is performed by dissolving and removing the core after the degreasing and sintering step of degreasing and sintering the demolded product. .