JP2000087105A - Production of sintered material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deformation at the time of degreasing or sintering and to obtain a good sintered material having no defective sintering. SOLUTION: A producing method of a sintered material is provided with a process for forming a compact containing metallic powder and a binder through e.g. a metallic powder injection molding method (MIM), a process for applying degreasing treatment to this compact and a process for obtaining the sintered material by sintering the obtd. degreased material. The compact 1 is the one integrated with lens frames 3, 4 at the right and left sides, a spectacle frame portion 2 constituted with a connecting part 5 for connecting these lens frames and a portion as a reinforcing member for reinforcing the spectacle frame portion 2. The portion as the reinforcing member is a left plate 8 and a right plate 9 formed in the inside of an upper bridge 6 and a lower bridge 7 for connecting the lens frames 3, 4 at the right and the left parts to each other and the lens frames 3, 4 at the right and the left sides. The upper bridge 6, lower bridge 7, left plate 8 and right plate 9 are removed after sintering.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a sintered body obtained by sintering a metal powder.

[0002]

2. Description of the Related Art In producing a metal product by sintering a compact containing a metal powder, as a method for producing a compact, a metal powder and an organic binder are mixed and kneaded, and injection molding is performed using the kneaded product. Metal Injection Molding (MIM: Metal In)
jection Molding) method is known.

[0003] The molded article manufactured by the MIM method is as follows.
After being subjected to a degreasing treatment (a binder removal treatment) to remove an organic binder, it is subjected to sintering.

[0004] Metal products manufactured by such a method include, for example, eyeglass frames, watch exterior parts,
Examples include golf club heads, orthodontic parts, and dental parts such as implants.However, those having thin, rod-like or frame-like parts such as eyeglass frames can be used for degreasing or burning due to insufficient strength. Deformation is likely to occur during knotting, resulting in low dimensional accuracy.

[0005] Further, in the case of such a thin, rod-shaped or frame-shaped portion, the passage of the molding material in the cavity of the molding die during metal powder injection molding is narrow.
Since the position and the cross-sectional area of the gate are restricted, the fluidity and the diffusivity of the molding material are inferior, and therefore, the density of each part of the molding becomes uneven. As a result, a sintered body obtained from such a molded body is liable to have a sintering defect such as deformation, cracking, and sink.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method of manufacturing a sintered body capable of preventing deformation during degreasing or sintering and obtaining a good sintered body without sintering defects. Is to do.

[0007]

This and other objects are achieved by the present invention which is defined below as (1) to (10).

(1) A step of forming a molded body containing a metal powder and a binder, wherein a part to be a target sintered product and a part to be a reinforcing member for reinforcing the target sintered product are integrally formed. A method for producing a sintered body, comprising: a step of forming a green body; a step of performing a degreasing treatment on the obtained molded body; and a step of sintering the obtained degreased body to produce a sintered body. .

(2) The method for producing a sintered body according to the above (1), further comprising a step of removing a portion of the reinforcing member from the obtained sintered body.

(3) The method for producing a sintered body according to (2), wherein the portion of the reinforcing member is removed by at least one of mechanical processing, electric discharge machining, laser machining, and etching.

(4) The method for producing a sintered body according to any one of (1) to (3), wherein the molded body is produced by a metal powder injection molding method.

(5) The method for producing a sintered body according to the above (4), wherein a gate for injecting a molding material into a molding die is formed in a portion serving as the reinforcing member and metal powder injection molding is performed.

(6) The method for producing a sintered body according to any one of the above (1) to (5), wherein the target sintered product is an eyeglass frame.

(7) The method of manufacturing a sintered body according to (6), wherein the portion serving as the reinforcing member is formed so as to connect the left and right lens frames of the eyeglass frame.

(8) The method for producing a sintered body according to (6) or (7), wherein the portion serving as the reinforcing member is formed inside the left and right lens frames of the eyeglass frame.

(9) The sintered body according to (6) or (7), wherein the portion serving as the reinforcing member is formed in a plate shape so as to substantially fill the entire inside of the left and right lens frames of the eyeglass frame. Manufacturing method.

(10) The method for producing a sintered body according to the above (6) or (7), wherein a rib is formed in a portion serving as the plate-like reinforcing member.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a method for producing a sintered body according to the present invention will be described in detail.

FIG. 1 is a process diagram showing an embodiment of a method for manufacturing a sintered body according to the present invention, and FIGS. 2 and 3 are front views showing the structure of an eyeglass frame (molded product, target sintered product), respectively. FIG. Hereinafter, an embodiment of a method for manufacturing a sintered body will be described with reference to the drawings.

[1A] Manufacture of molded body The method of manufacturing a molded body is not particularly limited, and may be a conventional method such as compacting. However, in the present invention, the molded body is manufactured by a metal powder injection molding (MIM) method. Are preferred.

This metal powder injection molding method has the advantages that a relatively small-sized or complicated and finely shaped metal sintered product can be manufactured and that its mechanical strength is high. In applying the invention, the effect is effectively exhibited, which is preferable.

Hereinafter, preparation of a molding material and production of a molded article by the MIM method will be described.

First, a metal powder and a binder (organic binder) are prepared and kneaded with a kneader to obtain a kneaded product (compound).

The metal material constituting the metal powder (hereinafter simply referred to as “metal material”) is not particularly limited. For example, Fe, Ni, Co, Cr, Mn, Zn, Pt, A
u, Ag, Cu, Pd, Al, W, Ti, V, Mo, N
at least one of b, Zr, Pr, Nd, Sm, etc.
And alloys containing (mainly) at least one of these.

In particular, when the target sintered product is an eyeglass frame, stainless steel (for example, SU
S304, SUS316, SUS317, SUS329
J1, SUS410, SUS430, SUS440, S
Fe-based alloys represented by US630), Ti or Ti
Based alloys are preferred.

Examples of metals other than Ti constituting the Ti-based alloy include Fe, Ni, Cr, Pd, Co, Zr,
One or more of Al, V, Mo, Sn, Au, Ag, and Cu are listed. In this case, the total content of metals other than Ti is preferably 60% by weight or less,
More preferably, it is less than 50% by weight.

The average particle size of the metal powder is not particularly limited, but is preferably 150 μm or less.
About 60 μm is more preferable. If the average particle size is too large, the sintering density may decrease depending on other conditions.

The method for producing the metal powder is not particularly limited, and for example, those produced by a water or gas atomization method, a reduction method, a carbonyl method, or a pulverization method can be used.

As the binder, for example, polyethylene,
Polyolefins such as polypropylene and ethylene-vinyl acetate copolymer, acrylic resins such as polymethyl methacrylate and polybutyl methacrylate, styrene resins such as polystyrene, polyvinyl chloride, polyvinylidene chloride, polyamide, polyester, polyether and polyvinyl alcohol Or various resins such as copolymers thereof, various waxes, paraffins, higher fatty acids (eg, stearic acid), higher alcohols, higher fatty acid esters, higher fatty acid amides, and the like. A mixture of more than one species can be used.

Further, a plasticizer may be added to the kneaded material. Examples of the plasticizer include phthalic acid esters (eg, DOP, DEP, DBP), adipic acid esters, trimellitic acid esters, sebacic acid esters, and the like. One or more of these may be mixed. Can be used.

At the time of the kneading, various additives such as a lubricant, an antioxidant, a degreasing accelerator and a surfactant are added as required in addition to the metal powder, the binder and the plasticizer. be able to.

The kneading conditions vary depending on various conditions such as the metal composition and particle size of the metal powder to be used, the composition of the binder and the additives, and the amounts of the additives. For example, the kneading temperature: 2
The kneading time can be about 0 to 200 ° C. and about 20 to 210 minutes. The kneaded material is formed into pellets (small blocks) as necessary. The particle size of the pellet is, for example, 1 to 10 mm
Degree.

Next, using the kneaded material obtained above or pellets granulated from the kneaded material, injection molding is performed by an injection molding machine to produce a molded body having a desired shape and dimensions. In this case, it is possible to easily produce a molded body having a complicated and fine shape by selecting a molding die.

Hereinafter, the target sintered product (sintered metal product)
The case where the eyeglass frame is manufactured will be described.

As shown in FIGS. 2 and 3, the molded body 1 manufactured by the MIM method includes a portion to be an eyeglass frame (a target sintered product) (hereinafter, referred to as an “eyeglass frame portion 2”). And a portion serving as a reinforcing member for reinforcing the eyeglass frame portion 2.

The eyeglass frame portion 2 is mainly located between the pair of left and right lens frames 3, 4 and the middle of the lens frames 3, 4.
And a connecting portion 5 for connecting these.

There are four portions serving as reinforcing members for reinforcing the eyeglass frame portion 2. That is, the tie-bar-shaped upper bridge (connecting member) 6 that connects the left and right lens frames 3 and 4 at the upper portion in FIG. 2 and the left and right lens frames 3 and 4 are connected at the lower portion in FIG. A tie bar-shaped lower bridge (connecting member) 7, a left plate (plate-like reinforcing member) 8 formed inside the left lens frame 3, and a right plate (plate-shaped member) formed inside the right lens frame 4. Four (reinforcement members) 9 are portions serving as reinforcement members for reinforcing the eyeglass frame portion 2.

In this case, the left plate 8 holds the left lens frame 3
The right plate 9 is formed so as to fill the entire inside (inside portion) of the right lens frame 4. By providing such a left plate 8 and a right plate 9, the left lens frame 3 and the right lens frame 4 are deformed into a shape different from the target shape at the time of degreasing or sintering, which will be described later (hereinafter, simply referred to as "deformation"). Is prevented.

By providing the upper bridge 6 and the lower bridge 7, deformation of the entire eyeglass frame portion 2 is prevented, and in particular, the positional relationship between the left and right lens frames 3, 4 can be made appropriate.

The upper bridge 6, the lower bridge 7,
Both the left plate 8 and the right plate 9 are formed integrally with the glasses frame portion 2 by metal powder injection molding.

On the front sides of the left plate 8 and the right plate 9, there are formed ribs 81 and 91, each of which is formed as a ring-shaped projection. These ribs 81 and 91 are
It mainly has a function of preventing deformation of the left plate 8 and the right plate 9 in the thickness direction. Therefore, by providing the ribs 81 and 91, the deformation of the left lens frame 3 and the right lens frame 4 can be more reliably prevented.

The injection of the molding material into the mold during the metal powder injection molding is performed using two gates near the center of the left plate 8 and near the center of the right plate 9.
Therefore, as shown in FIGS. 2 and 3, the molded body 1 has a convex gate trace 82 corresponding to the gate of the molding die at substantially the center of the rear surface of the left plate 8 and the right plate 9.
And 92 are formed. As a result, the molding material is passed through the left plate 8 and the right plate 9 to form the molded body 1.
Can be uniformly flowed and diffused throughout the entire surface. Also,
The gate cross-sectional area, that is, the cross-sectional area of the gate traces 82 and 92 can be larger. For this reason, molding defects can be effectively prevented, and the density of the molded body 1 can be made uniform. Accordingly, deformation of the molded body (degreasing body) 1 during degreasing or sintering, which will be described later, is prevented, and sintering defects such as cracks and sink marks are also prevented.

The shape and dimensions of the molded article 1 to be manufactured are determined in consideration of the amount of shrinkage of the molded article 1 due to the subsequent degreasing and sintering.

The molding conditions of the metal powder injection molding vary depending on various conditions such as the metal composition and particle size of the metal powder to be used, the composition of the binder and the amount of the binder, and for example, the material temperature is preferably The injection pressure is preferably about 20 to 200 ° C and the injection pressure is preferably about 30 to 150 kgf / cm ² .

The molded body 1 thus obtained is in a state where the metal powder is substantially uniformly dispersed in the binder.

The shape, installation position, number, and the like of the portions serving as the reinforcing members for reinforcing the eyeglass frame portion 2 are not limited to those shown in the drawings. In particular, when a reinforcing member is formed inside the left lens frame 3 and the right lens frame 4, the reinforcing member is not limited to a plate-like member as shown in FIG. At least one rod-shaped body may be integrated.

The shape of the spectacle frame portion 2 is not limited to the illustrated one, but may be, for example, a nylon roll type (having no lower half of the left lens frame 3 and the right lens frame 4). Also in this case, it is preferable to provide a connecting member for connecting both lens frames and a plate-like reinforcing member for filling the inside of both lens frames.

The target sintered product (metal sintered product)
It goes without saying that is not limited to eyeglass frames.

[2A] Degreasing treatment of molded article The molded article 1 obtained in the step [1A] is subjected to a degreasing treatment (a binder removal treatment).

The degreasing treatment includes a non-oxidizing atmosphere,
For example, under vacuum or reduced pressure (for example, 1 × 10 ⁻¹ to 1
× 10 ⁻⁶ Torr) or by performing a heat treatment in an inert gas such as a nitrogen gas or an argon gas.

In this case, the heat treatment is preferably performed at a temperature of about 150 to 750 ° C. for about 0.5 to 40 hours,
More preferably, the temperature is about 250 to 650 ° C. for about 1 to 24 hours.

The degreasing by such a heat treatment may be performed in a plurality of steps (steps) for various purposes (for example, for shortening the degreasing time). In this case, for example, a method in which the first half is degreased at a low temperature and the second half at a high temperature, or a method in which the low temperature and the high temperature are repeatedly performed.

The degreasing treatment may be performed by eluting a specific component in the binder or the additive using a predetermined solvent (liquid or gas).

As described above, since the density of the molded body 1 is uniform, when such a degreasing treatment is performed, the degreasing from the molded body 1 is made uniform, and the reinforcing effect of the reinforcing member is also reduced. Together, deformation is prevented.

[3A] Sintering The degreased body obtained as described above is fired and sintered in a sintering furnace to produce a metal sintered body.

By this sintering, the metal powder diffuses and grows to form crystal grains, which are dense as a whole, ie, have a high density.
A sintered body having a low porosity is obtained.

The sintering temperature in sintering is not particularly limited. For example, when the metal composition is Fe or an Fe-based alloy, the sintering temperature is preferably about 950 to 1450 ° C., more preferably about 1100 to 1400 ° C. In the case of a Ti-based alloy, the temperature is preferably about 900 to 1350 ° C, more preferably about 1000 to 1300 ° C.

The sintering time is preferably about 0.5 to 8 hours, more preferably about 1 to 8 hours at the sintering temperature as described above.
About 5 hours.

The sintering atmosphere is preferably a non-oxidizing atmosphere containing no hydrogen. This improves the safety during sintering and contributes to reducing the porosity of the sintered body.

The preferred sintering atmosphere is 1 × 10
⁻² Torr or less (more preferably 1 × 10 ⁻² to 1 × 10
The pressure is preferably a reduced pressure (vacuum) of ^-6 Torr or an inert gas atmosphere of 1 to 760 Torr such as nitrogen gas or argon gas.

The sintering atmosphere may change during sintering. For example, first, 1 × 10 ⁻² to 1 × 10 ⁻⁶
The pressure can be reduced to Torr (vacuum), and the gas can be switched to the inert gas as described above.

Sintering under the above conditions contributes to further reduction of the porosity, that is, higher density of the sintered body, high dimensional accuracy is obtained, and sintering efficiency is improved. Good sintering can be performed in a shorter sintering time, safety of sintering operation is high, and productivity is improved.

The sintering may be performed in two or more stages. For example, first sintering and second sintering under different sintering conditions can be performed. In this case, the sintering temperature of the second sintering can be higher than the sintering temperature of the first sintering. Thereby, the sintering efficiency is further improved, and the porosity can be further reduced.

As described above, since the density of the compact (degreasing body) 1 is uniform, sintering (grain growth) proceeds uniformly when such sintering is performed. Therefore, the molded body (degreased body) 1 is uniformly shrunk, and the sintering defects such as deformation, cracks, sink marks and the like are prevented in combination with the reinforcing effect of the reinforcing member.

[4A] Removal of Reinforcing Member The sintered body obtained as described above has an eyeglass frame portion and a reinforcing member portion integrated. Therefore, unnecessary portions of the reinforcing member (upper bridge 6, lower bridge 7, left plate 8, and right plate 9) are removed from the sintered body.

The method of removing the portion of the reinforcing member is not particularly limited. For example, various types of machining such as punching (press punching), cutting, cutting, and grinding, electric discharge machining, laser machining, and the like. Etching can be used, and one or more of these methods can be used in combination. Of these, mechanical processing such as press punching, cutting, cutting, and grinding, electric discharge machining, and laser machining are particularly preferable for reducing the process time (improving productivity).

Further, if necessary, the portion of the spectacle frame from which the reinforcing member has been removed can be subjected to post-processing such as grinding, polishing and chemical treatment.

In the present invention, for any purpose,
A step before the step [1A], an intermediate step existing between the steps [1A] to [4A], or a step after the step [4A] may be present.

[0069]

As described above, according to the present invention, the molded body is provided with a portion serving as a reinforcing member for reinforcing the target sintered product, thereby preventing deformation during degreasing or sintering.
A metal sintered product with high dimensional accuracy can be obtained.

In particular, when a molded article is produced by metal powder injection molding, the flowability and diffusibility of the molding material during molding can be improved, molding defects can be prevented, and the density of each part of the molded article can be made uniform. As a result, it is possible to prevent sintering defects such as deformation, cracks and sink marks.
Therefore, the mechanical strength and quality of the metal sintered product can be improved.

In the case of manufacturing a molded body by metal powder injection molding, the gate position can be set to a portion serving as a reinforcing member, and the restriction on the gate position is reduced, so that the degree of freedom of the shape is increased. In particular, the gate position can be set so as to be advantageous for the flow and diffusion of the molding material, and the gate cross-sectional area can be increased, so that the above-mentioned effect is more remarkably exhibited.

For this reason, for example, those having a thin-walled, rod-shaped or frame-shaped portion such as an eyeglass frame,
In the case of manufacturing a product that tends to be insufficient in strength, a product having a complicated shape, and the like, the above-described effect is more effectively exhibited, which is advantageous.

[Brief description of the drawings]

FIG. 1 is a process chart showing an embodiment of a method for producing a sintered body of the present invention.

FIG. 2 is a front view showing a configuration of an eyeglass frame (a molded product, a target sintered product).

FIG. 3 is a sectional view taken along line AA in FIG. 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Molded body (degreasing body) 2 Glasses frame part 3 Left lens frame 4 Right lens frame 5 Connecting part 6 Upper bridge 7 Lower bridge 8 Left plate 81 Rib 82 Gate mark 9 Right plate 91 Rib 92 Gate mark 1A Molding body manufacturing process 2A Degreasing process 3A Sintering process 4A Reinforcing member removal process

Claims (10)

[Claims] 1. A step of forming a molded body containing a metal powder and a binder, wherein a portion serving as a target sintered product and a portion serving as a reinforcing member for reinforcing the target sintered product are integrally formed. A method for producing a sintered body, comprising: a forming step; a step of degreasing the obtained molded body; and a step of sintering the obtained degreased body to produce a sintered body. 2. The method for producing a sintered body according to claim 1, further comprising a step of removing a portion of the reinforcing member from the obtained sintered body. 3. The method of manufacturing a sintered body according to claim 2, wherein the portion of the reinforcing member is removed by at least one of mechanical processing, electric discharge machining, laser machining, and etching. 4. The method for producing a sintered body according to claim 1, wherein the molded body is produced by a metal powder injection molding method. 5. The method for producing a sintered body according to claim 4, wherein a gate for injecting a molding material into a molding die is formed in a portion serving as the reinforcing member, and metal powder injection molding is performed. 6. The method for producing a sintered body according to claim 1, wherein the target sintered product is an eyeglass frame. 7. The method for manufacturing a sintered body according to claim 6, wherein the portion serving as the reinforcing member is formed so as to connect left and right lens frames of the eyeglass frame. 8. The method for manufacturing a sintered body according to claim 6, wherein the portion serving as the reinforcing member is formed inside the left and right lens frames of the eyeglass frame. 9. The method of manufacturing a sintered body according to claim 6, wherein the portion serving as the reinforcing member is formed in a plate shape so as to substantially fill the entire inside of the left and right lens frames of the eyeglass frame. 10. The method for producing a sintered body according to claim 6, wherein a rib is formed in a portion serving as the plate-like reinforcing member.