JP2995661B2 - Manufacturing method of porous cemented carbide - Google Patents

Description

The present invention relates to a method for producing a porous cemented carbide,
The properties having both porosity and abrasion resistance are used in many fields. Examples of the one end include oil-impregnated bearings as sliding parts, the tip of a suction jig as a tool material, and resin or the like for a mold to discharge air or gas for a mold.

[Summary of the Invention]

In the method for producing a porous cemented carbide according to the present invention, the raw material powder is granulated without adding an organic substance such as a resin to the raw material powder, and without pressure molding, and vibration is applied to an arbitrary carbon mold. The shape is adjusted by temporary sintering in a vacuum furnace. This temporary sintered body is temporarily placed on a ceramic or the like and subjected to main sintering, and a cemented alloy having air permeability is obtained by a process of solidifying by melting Co or Ni as a binder.

[Conventional technology]

Many proposals have been made on the production of porous cemented carbide by the powder metallurgy method. Recently, for example, a technical journal “Powder and Powder Metallurgy” Vol. 36, No. 2
No. (March 1989, Issued by the Japan Powder Metallurgy Association) (31)-
(35) There is a document "Manufacturing of cemented carbide for sliding with pores dispersed therein and its various properties" described on page (35). As shown in the literature, in the conventional production method, a resin was added to and mixed with a WC-Co alloy powder, and the mixture was pressed and then vacuum-sintered. Good pore dispersion is obtained by the action of organic substances that evaporate during this sintering.

[Problems to be solved by the invention]

In the above-described conventional manufacturing method, a raw material powder to which an organic substance such as a resin is added is subjected to pressure molding before sintering. This method is
Pore is formed in that part by volatilization of organic matter during sintering.Therefore, there is contamination of the sintering furnace, and in order to secure brittleness as a super hard material, it is necessary to press It was essential to obtain a uniform bond and eliminate local defects.

The present invention provides a manufacturing method based on a novel idea without applying the above essential requirements. That is, the problem is solved by directly granulating the raw material powder without adding an organic substance into a carbon mold and performing sintering treatment without applying pressure.

[Means for solving the problem]

In order to solve the above-mentioned problem, the production method of the present invention uses WC
, A raw material powder comprising Ni or Co as a binding component and a property improving component is granulated, injected into a carbon mold while applying vibration, and temporarily sintered. Next, the problem is solved by subjecting the pre-sintered body taken out of the carbon mold to a main sintering step at a higher temperature than the above-described pre-sintering.

[Action]

The feature of the method for producing a porous cemented carbide according to the present invention is 3
There are points, and the events that work are explained. The first point is,
By obtaining uniform pores without adding an organic substance, this is a technique in which the surfaces of the granulated particles come into contact with each other and voids formed therein lead to the formation of pores in the final sintered body.

The second point is that the compression step is not applied. This is because the above-mentioned respective particles are uniformly dispersed, and the contact between the surfaces is multi-point and the contact pressure becomes uniform. I have. This can be realized by adding mechanical kinetic energy such as vibration when the raw material particles are injected into the carbon mold or after the injection.

Next, the third point is temporary sintering for forming a temporary temporary shape in the above-mentioned casting state without pressurization, and then main sintering to form a full-scale super hard material. Applying two sintering steps.

The features of the first and second aspects of the present invention composed of the above three aspects are based on a novel idea that basically reverses the conventional technical idea. That is, in the production of a porous cemented carbide, brittleness countermeasures, which are indispensable for cemented carbide, are an important issue, and it is thought that cracks and chips are induced from defects in the metal structure. Conventionally, to eliminate this defect,
Pressure was applied to make the entire density uniform and sintered to obtain a defect-free structure.

On the other hand, in the present invention, the entire metal structure is formed into a defect structure, whereby impacts and stresses are uniformly applied to the entire structure, stress concentration is prevented, cracks and chips are prevented from occurring, and the defect structure is formed. The gap serves as a pore and exhibits a breathable action.

〔Example〕

One embodiment of the present invention will be described in the order of steps.
First, WC as the main component of the raw material powder and about 13% Co as the binder
Is granulated to an average particle size of 150 μm by tumbling granulation and, if necessary, sieved. The raw material particles (hereinafter simply referred to as particles) are poured into a mold for a container made of a carbon material having an arbitrary shape. At the time of this injection, it is preferable to perform injection while applying vibration to the mold, but vibration may be applied after injection. The control of the excitation energy uses an AC commercial power supply. The upper limit of the strength is that the grains do not break, and the lower limit is that the grains are distributed at a uniform density.

Next, the cast product is temporarily sintered in a vacuum furnace. The condition is that the temperature is raised to 500 ° C in 2 hours with a vacuum degree of about 2 × 10 ^-2 Torr, then the temperature is raised to 1160 ° C in 2 hours, pre-sintering is performed for about 30 minutes, and the furnace is cooled and removed. . The temperature range to be controlled by the pre-sintering temperature is + 20 ° C., and the carbon material of the mold reacts with the grains, so that free carbonization occurs in the composition of the grains and the releasability deteriorates. On the other hand, when the temperature is as low as −20 ° C., there is no connection as a bonding force between the surfaces of the grains, and the grains are easily broken when the mold is released. FIG. 1 shows an SEM photograph of the structure after the preliminary sintering. The powdery phenomenon on the surface of the particles shown in this figure is not a smooth surface because the particles according to the present invention do not contain an organic binder, and is a surface on which the raw material powder is irregularly attached. However, this substantially conical surface contributes to the action of binding the grains in the above-described temporary sintering.

In this pre-sintering process, the pre-sintered body in the carbon mold is
With shrinkage of about 5%, the mold is released from the mold, and there is no binding due to the reaction with the carbon material. Therefore, it can be easily removed from the mold. However, care must be taken when handling since the binding force between grains is weak. In addition, although the carbon material is exemplified as the mold for the temporary sintering, the material is selected from the workability for an arbitrary shape, heat resistance, economy, and the like, and is not limited thereto.

Next, the pre-sintered body is placed on a heat-resistant base such as a ceramic plate and main-sintered at a degree of vacuum of 2 × 10 ⁻² Torr.
The sintering conditions are as follows: 500 ° C. for 1 hour, 1250 ° C. for 1 hour, then 37 minutes to 1370 ° C., main sintering at this temperature for 1 hour, and furnace cooling to end.

Due to the temperature of this sintering, Co as a binder melts,
WC super hard material is obtained. The volume shrinkage in this sintering example was about 20%, and the porous air permeability was about 28%. FIG. 2 shows an SEM photograph of the structure of the surface of the sintered body of the above-described embodiment, which is shown by SEM photograph. Since the magnification is the same as that in FIG. 1, the degree of shrinkage is clear, and the surface of each grain is fused with the molten Co and is smooth. FIG. 3 shows an SEM photograph of the fusion of the grains and the state of the pores formed in the gaps. The figure shows the state of the surface of the sintered body according to the above-mentioned embodiment, which was polished, and there was no boundary in the melt contact surface of each grain, and the pores were uniformly distributed. The sintering conditions in the embodiment described here are only examples. For example, if the sintering temperature is increased, the fusion contact surface shown in FIG. 3 is widened, and the mechanical strength such as the transverse rupture strength is improved accordingly. I do. However, on the other hand, the air permeability decreases. The selection and control of these characteristics are optional depending on the conditions set for the main sintering, and in order to improve the characteristics,
It is optional to add components such as Cr, Ti, and Ta as needed.

〔The invention's effect〕

As described above, according to the method of the present invention, it is possible to obtain an inexpensive and stable porous cemented carbide material by a simplified process without mixing organic substances and without applying a compression molding process. In particular, there is no quality reduction or work management due to contamination of the sintering furnace due to the volatilization of the organic binder, and a remarkable effect in production technology is exhibited.

[Brief description of the drawings]

FIG. 1 is a micrograph showing the particle structure of the pre-sintering according to the present invention. 2 and 3 are micrographs showing the grain structure of the main sintering according to the present invention.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) B22F 5/00 C22C 1/08

Claims (4)

(57) [Claims] (1) WC as a main component, and Ni or Co as a binding component.
The raw material powder containing the raw material powder is granulated to form raw material particles, a step of temporarily sintering the raw material particles while applying vibration to a mold serving as a container, A method for producing a porous cemented carbide, comprising a step of main sintering at a temperature higher than the preliminary sintering temperature. 2. A composition comprising WC as a main component and Ni or Co as a binding component.
After granulating the raw material powder containing
Vibrating the container, pre-sintering, and main-sintering the pre-sintered body after the pre-sintering step at a temperature higher than the pre-sintering temperature. Manufacturing method of hard alloy. 3. A raw material powder comprising Cr, Ti,
The method for producing a porous cemented carbide according to claim 1 or 2, wherein one or more kinds of Ta are added. 4. The granulation according to claim 1, wherein said granulation is rolling granulation.
A method for producing a porous cemented carbide according to any one of the above.