KR20230151199A - Metal powder injection molding system for metallic frame and the manufacturing method for metallic frame using the system - Google Patents

Abstract

The present invention relates to a method of manufacturing a metal frame base product used to produce metal frames used as parts of electronic products such as mobile phones, smart keys, remote controls, etc., using a metal powder binder mixture containing metal powder and binder. A metal powder injection molded product system is provided including a manufactured metal powder injection molded product and a support means for fixing the side wall of the molded product so that it does not shrink in the longitudinal direction when the metal powder injection molded product is sintered. By using the basic metal frame product manufactured using the above system, mass production of the metal frame is easy and the production cost can be reduced, as well as the amount of metal consumed in manufacturing the metal frame can be reduced.

Description

Metal powder injection molding system for manufacturing basic metal frame products and method for manufacturing metal frame basic products using the same

The present invention relates to a method of producing metal borders (frames) used as parts of electronic products such as mobile phones, smart keys, remote controls, etc., and is a newly designed metal powder injection molding system that can produce metal borders by sintering metal powder. and its manufacturing method.

In other words, the present invention relates to a method of manufacturing a metal frame using sintered metal, which has never been applied to the production of a metal frame in the past. More specifically, the present invention relates to a method of manufacturing a metal frame using sintered metal, which has a new shape and function designed to be applied to the production of a metal frame using sintered metal. This relates to a metal powder injection molded product system and a metal frame manufacturing method using the same.

Metal frames are widely used to improve the strength and aesthetics of electronic products such as mobile phones, smart keys, and remote controls.

As shown in Figure 1, the conventional metal frame was made through many processes (30 processes were required in the past in Pantech), such as cutting and shaving a lump of metal using various equipment such as a lathe.

Therefore, in the conventional method, the amount of metal cut out is large compared to the amount of metal actually used in the finished product, so not only is there a lot of loss of raw materials, but most of the production cost is taken up by processing costs rather than the metal price of the metal frame itself.

Therefore, despite the many advantages of metal edging, finished product companies such as Samsung Electronics were unable to adopt it for a long time due to high production costs and supply and demand problems.

Meanwhile, Metal Injection Molding (MIM) is a molding method created by combining general plastic injection molding and metal powder sintering technology developed in the powder metallurgy field.

Metal powder injection molding is capable of manufacturing 3D precision parts using all powder materials such as metal, ceramic, cemented carbide, and intermetallic compounds, and can produce precise and complex parts such as difficult-to-process materials or non-castable materials to a stage where post-processing is almost unnecessary. Because it can be molded, it has the advantage of being mass-produced.

However, when molding a high specific gravity metal powder through injection, a binder containing a mixture of resin and wax is used mixed with the metal powder to provide bonding between the metal powders and injection fluidity, so the injection molded product depends on the characteristics of the binder. It affects the molding quality, and since a degreasing process to remove the binder is required, it has a significant impact on the quality and productivity of sintered products manufactured from injection molded products.

In addition, shrinkage of the injection molded product occurs during sintering, so parts with thinner thickness and smaller width than the overall size, such as metal frames, are prone to deformation and destruction due to sintering, so metal powder injection molding is used to make metal parts. Manufacturing a border has not been attempted.

Korean Patent Publication No. 10-2005-0059280 (published on June 17, 2005) Korean Patent Publication No. 10-1997-0002093 (announced on February 22, 1997) Japanese Patent Publication No. 5-171218 (announced on July 9, 1993)

The present invention relates to a new manufacturing method that solves the problems of the prior art in the manufacturing process of metal frames inserted into cases of electronic products such as mobile phones and smart keys.

One problem of the present invention is to solve the problem that the process of making a metal frame through cutting of a metal lump is extremely labor-intensive and is difficult to mass-produce by making individual products.

Another task of the present invention is to solve the problem that conventional metal frame manufacturing involves numerous individual processes, so it takes a lot of time and the unit cost is high.

Another task of the present invention is to solve the problem that the amount of metal cut and discarded is too large compared to the amount of metal frame produced.

The present invention relates to a method of manufacturing a metal frame for electronic products using sintered metal, which has never been applied before. More specifically, a method of producing a basic metal frame product by sintering an injection molded product formed using a metal powder injection molding method. It relates to a metal powder injection molded product with a new shape and function used in the above method and its system.

The metal powder injection molded product system according to the present invention includes molded product side walls for manufacturing a metal border, is arranged to intersect each other and has a closed shape, and is disposed on the inside of a corner where the molded product side walls intersect during sintering. It includes support means that secure the side wall of the molded product so that it does not shrink in the longitudinal direction.

The support means fixes the side wall of the molded product so that it does not shrink in the longitudinal direction during sintering and can be formed to be separable from the side wall of the molded product after sintering.

As shown in Figure 2, metal frame base products require side walls that are thin and long compared to the overall size, and it is not easy to manufacture such thin and long side walls by sintering metal powder injection molded products.

This is because the shrinkage of the side wall of the molded product that occurs during sintering of a metal powder injection molded product causes deformation such as twisting and destruction such as cutting in the side wall of the molded product.

The metal powder injection molded product according to the present invention is sintered while the inside corner of the side wall of the molded product is supported and fixed by a separate support means to prevent deformation and destruction of the side wall of the molded product that occurs during sintering, so that the side wall of the molded product is deformed during the sintering step. , it can be prevented from being destroyed.

The support means according to the present invention may include an inner corner support fixed to one side of the support means, and the inner corner support is a portion where the side walls of the molded product intersect for the purpose of preventing shrinkage of the side wall of the molded product in the longitudinal direction. It can be changed in various ways depending on its shape. That is, if the corner of the side wall of the molded product is rounded, a circular inner corner support can be used, or an inner corner support in which only the portion in contact with the corner of the side wall of the molded product is rounded can be used.

The inner corner support and support means may be configured to be easily separated from the metal powder injection molded product after sintering. That is, the inner corner support and the support means may include a ceramic material, and the inner corner support and the support means may be treated so as not to react with the side wall of the metal powder injection molded product.

The support means are treated so that they do not react with the sidewalls of the molded article, either (a) the entire support means is made of a non-reactive material that does not react with the sidewalls of the molded article, or (b) the support means is made entirely of a non-reactive material that does not react with the sidewalls of the molded article, or It may be manufactured by placing a reactive material, or ⒞ applying a non-reactive material or solution to one or more surfaces where the support means and the side wall of the molded product are in contact with each other, and then drying or sintering the molded product.

The metal powder injection molded product according to the present invention includes a metal powder binder mixture in which metal powder and a binder are mixed, and the metal powder includes molybdenum, tungsten, etc. and alloys thereof; Alloy steel containing Fe as a main component; Stainless alloy steel such as SUS630, SUS316, SUS304; It may be composed of one selected from titanium and titanium alloys or a mixture of two or more selected from these.

The metal powder binder mixture contains 47.5 to 65% by volume of stainless alloy steel metal powder; A binder consisting of 40 to 60% by weight of wax and 40 to 60% by weight of polymer material may be included at 35 to 52.5% by volume, and preferably 55 to 60% by volume of stainless steel alloy steel metal powder; A binder consisting of 40 to 60% by weight of wax and 40 to 60% by weight of polymer material may be included at 40 to 45% by volume.

And the binder may include 45-55% by weight of paraffin wax, 1-10% by weight of carnauba wax, 10-20% by weight of polypropylene, 25-35% by weight of polyacetal, and 1-10% by weight of amorphous polyalphaolefin. More preferably, the binder contains 45-50% by weight of paraffin wax, 1-5% by weight of carnauba wax, 10-15% by weight of polypropylene, 25-30% by weight of polyacetal, and 1-5% by weight of amorphous polyalphaolefin. % may be included.

Another metal powder binder mixture according to the present invention contains 45 to 75% by volume of titanium hydride metal powder; A binder consisting of 40 to 60% by weight of wax and 40 to 60% by weight of a polymer material may be included at 25 to 55% by volume; preferably, the binder is 40 to 60% by weight of paraffin wax and 15 to 30% by weight of polypropylene. , may include 10 to 30% by weight of polyethylene and 1 to 10% by weight of amorphous polyalphaolefin, and more preferably, the binder is 55 to 60% by weight of paraffin wax, 15 to 20% by weight of polypropylene, and 15 to 20% by weight of polyethylene. %, and may include 1 to 5 wt% of amorphous polyalphaolefin.

When a metal powder injection molded product is made from a metal powder binder mixture containing the titanium hydride metal powder, a certain distance (restraint gap) is provided between the inner corner of the side wall of the molded product and the inner corner support when fixing the metal powder injection molded product to the support means. There is a need to maintain . This is because hydrogen escapes from titanium hydride during sintering, resulting in greater shrinkage compared to metal powder molded products using stainless alloy steel metal powder. Therefore, when the side walls of the molded product and the inner corner support are placed in contact with each other (i.e., the restraint gap is 0) %) When sintering, the side wall of the molded product is distorted or cracked. The restraint interval may be set to 1.5 to 5.5%, more preferably 1.5 to 5%.

The metal powder injection molded product according to the present invention may have a polygonal shape, and a portion of the inner corner support may have a shape that matches the inside of the corner portion of the polygonal shape.

The metal powder injection molded product system according to the present invention provides a system capable of sintering a plurality of metal powder injection molded products.

As an example, a multi-connected inner corner is configured in which a plurality of metal powder injection molded products are stacked on a support means, and an inner corner support is disposed to penetrate the support means and is caught on the inside of a corner of the plurality of metal powder injection molded products. It may consist of a support.

As another example, a plurality of metal powder injection molded products are stacked in a state separated by a spacing member, and an inner corner support fixed on a support means is configured to hang on the inside of the corner of the plurality of metal powder injection molded products. It may be composed of corner supports.

In another example, two support means are arranged in a standing position facing each other, a plurality of metal powder injection molded products are arranged separated by spacers between the support means, and the inner corner supports fixed through the two support means are the plurality of metal powder injection molded products. It may be composed of a multi-connected inner corner support configured to be hung on the inside corner of a metal powder injection molded product.

As another example of the metal powder injection molded product system according to the present invention, the metal powder injection molded product system may further include a guide supporting one or more of the inner surface, outer surface, inner and outer surface, width direction, or thickness direction of the side wall of the molded product. You can.

The guide may be configured to support not only the thickness direction of the side wall of the molded product, but also the inner side, outer side, inner and outer side, or width direction of the side wall of the molded product. Therefore, the shape of the basic metal frame product can be changed in various ways, making it possible to manufacture metal frames with various shapes. In addition, when the side wall of the molded product is long and it is difficult to support the side wall of the molded product with only the inner corner support, the guide material may be added to a portion of the side wall of the molded product to prevent the side wall of the molded product from being deformed during sintering.

The guide material may be configured not to react with the side wall of the molded product.

The metal powder injection molded product system according to the present invention can provide a method for manufacturing a metal frame base product, which includes designing the shape of the metal powder injection molded product; Manufacturing a mold according to the shape; Injecting the metal powder binder mixture into a mold manufactured to suit the shape of the metal powder injection molded product - the metal powder injection molded product includes molded product side walls for manufacturing a metal border, and the molded product side walls are arranged to cross each other to form a metal powder injection molded product. has a closed shape; After supercritical degreasing and heat degreasing of the metal powder injection molded product, it is fixed on a support means that is placed on the inside of the corner where the side walls of the molded product intersect to prevent the side wall of the molded product from shrinking in the longitudinal direction during sintering, and then sintered. step; It may include the step of separating the metal frame base product from the support means.

The metal powder binder mixture contains 55 to 60% by volume of stainless alloy steel metal powder; 45 to 55% by weight of paraffin wax, 1 to 10% by weight of carnauba wax, 10 to 20% by weight of polypropylene, and 25 to 35% by weight of polyacetal. , a binder containing 1 to 10% by weight of amorphous polyalphaolefin may be included at 40 to 45% by volume; preferably, the binder is 45 to 50% by weight of paraffin wax, 1 to 5% by weight of carnauba wax, and polypropylene. It may contain 10 to 15% by weight, 25 to 30% by weight of polyacetal, and 1 to 5% by weight of amorphous polyalphaolefin.

Another metal powder binder mixture provided by the present invention includes 45 to 75% by volume of titanium hydride metal powder; A binder containing 40 to 65% by weight of paraffin wax, 15 to 30% by weight of polypropylene, 10 to 30% by weight of polyethylene, and 1 to 10% by weight of amorphous polyalphaolefin at 25 to 55% by volume; Preferably, the binder may include 55 to 60% by weight of paraffin wax, 15 to 20% by weight of polypropylene, 15 to 20% by weight of polyethylene, and 1 to 5% by weight of amorphous polyalphaolefin.

In particular, when the metal powder binder mixture contains titanium hydride metal powder, the confinement gap between the support means and the metal powder injection molded product may be 1.5 to 5.5%, and preferably the confinement gap may be 1.5 to 5%.

The present invention provides a new method for manufacturing metal frames inserted into cases of electronic products such as mobile phones, smart keys, etc., thereby facilitating mass production of metal frames and lowering production costs. Additionally, resources can be saved by using a smaller amount of metal compared to conventional metal frame manufacturing.

Figure 1 is a photograph of a metal frame production process according to the prior art.
Figure 2 is a diagram showing an exemplary metal frame base product manufactured from a metal powder injection molded product for a metal frame.
Figure 3 shows an example of a metal powder injection molded product system including a metal powder injection molded product for a metal border and a support means.
Figures 4 to 6 show metal powder injection molded product systems that can simultaneously laminate and sinter two or more metal powder injection molded products as another embodiment of the present invention.
Figure 7 shows another type of metal powder injection molded product system for a metal border according to the present invention, which further includes guide materials for forming various shapes such as thickness and width of the side wall of the molded product.

The advantages and features of the present invention and methods for achieving them will become clear by referring to the embodiments described in detail below along with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and may be implemented in various different forms. The present embodiments are merely provided to ensure that the disclosure of the present invention is complete and to provide a general understanding of the technical field to which the present invention pertains. It is provided to fully inform the skilled person of the scope of the present invention, and the present invention is only defined by the scope of the claims.

The terminology used herein is for describing embodiments and is not intended to limit the invention. As used herein, singular forms also include plural forms, unless specifically stated otherwise in the context. As used in the specification, “comprises” and/or “comprising” does not exclude the presence or addition of one or more other elements in addition to the mentioned elements.

Unless otherwise defined, all terms (including technical and scientific terms) used in this specification may be used with meanings commonly understood by those skilled in the art to which the present invention pertains. Additionally, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless clearly specifically defined.

Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings.

Figure 2 applies the concept of a metal powder injection molded product for a metal frame and the concept of minimizing longitudinal shrinkage without damage in the debinding and sintering processes by significantly delaying the sintering time compared to conventional sintered metal production. This is a diagram illustrating a basic metal frame product to which the present invention is applied before the square metal frame including four intersecting side walls 100 is created.

The metal frame base product has a square shape, but the shape of the metal frame base product can be changed in various ways depending on the shape of the electronic product case, etc. If the corners of the electronic product have a rounded shape, the corners of the metal frame base product may also be rounded.

Here, “metal frame basic product” refers to the final product of the present invention before becoming a metal frame through processing. Metal frame basic products refer to products after the metal powder injection molded product that has been fixed by the support means is removed from the metal powder injection molded product that has gone through the sintering process.

Figure 3 shows an example of a metal powder injection molded product system including a metal powder injection molded product for a metal border and a support means.

As shown, the metal powder injection molded product system includes a metal powder injection molded product having a square shape with four molded product side walls 500 intersecting and four inner corners inside the corner portions 501 to 504 of the metal powder injection molded product. It includes support means 514 provided with supports 540 to 543.

That is, Figure 3 is an example of a metal powder injection molded product system for making a basic metal frame product as shown in Figure 2.

The inner corner supports 540 to 543 are fastened to one surface of the support means 514. Therefore, during the sintering process of metal powder injection molded products, the side walls of the molded products can withstand the force of shrinking in the longitudinal direction. In other words, since the inside of the corner of the side wall of the molded product is fixed by the inner corner support, the shape of the side wall of the metal powder injection molded product can be maintained even during sintering, making it possible to produce basic metal frame products with the desired dimensions and shape. there is.

In the above embodiment, the inner corner support is shown as having a square shape according to the shape of the corner of the side wall of the molded product, but for the purpose of preventing shrinkage of the side wall of the molded product in the longitudinal direction, it can be varied depending on the shape of the part where the side walls of the molded product intersect. may be changed. That is, if the inner corner of the molded product has a rounded shape, a circular inner corner support can be used, or an inner corner support in which only the portion in contact with the inner corner of the side wall of the molded product is rounded can be used.

The inner corner support and support means may be configured to be easily separated from the metal powder injection molded product after sintering. That is, the inner corner support and the support means may include a ceramic material, and the inner corner support and the support means may be treated so as not to react with the side wall of the metal powder injection molded product.

The inner corner support and the support means are treated so that they do not react with the side wall of the metal powder injection molded product because the entire inner corner support and the support means are made of a non-reactive material that does not react with the side wall of the molded product, or the outside of the inner corner support and the support means is made of a non-reactive material that does not react with the side wall of the molded product. It may be made of a non-reactive material that does not react with the side wall of the molded product, or it may be dried or sintered by applying a non-reactive material or solution to the contact surface of the inner corner support or support means in contact with the side wall of the molded product. The non-reactive material may be either ceramic powder or graphite powder, or a combination of two or more.

Hereinafter, the metal powder binder mixture required to manufacture metal powder injection molded products will be described.

The metal powder injection molded product according to the present invention can be manufactured by a metal powder injection molding method including a binder and metal powder.

That is, the powder is injection molded into an appropriate shape, and the powder may be subjected to ceramic sintering, metal powder sintering, or a mixture of these sintering processes.

In order to manufacture metal powder injection molded products, in addition to the above powder, a binder (binder) is used to give fluidity to the metal powder and maintain its shape. The main ingredients of the binder are wax and various polymer materials can be used. Of course, when a binder is used in this way, an additional binder removal process must be performed.

Since the injection molding mixture of the metal powder and binder can be injection molded using a precision injection molding machine for general plastics, various types of metal powder injection molded products can be manufactured using an injection molding machine.

The metal powder injection molded product according to the present invention may include metal powder and a binder, and the metal powder includes molybdenum, tungsten, etc. and alloys thereof; Alloy steel containing Fe as a main component; Stainless alloy steel such as SUS630, SUS316, SUS304; It may be composed of one selected from titanium and titanium alloys or a mixture of two or more selected from these, and preferably stainless steel alloy steel or titanium hydride may be used.

Various waxes and various polymer materials can be used as binders for the production of metal powder molded products. Preferably, paraffin wax, carnauba wax, etc. can be used as a mixture of these waxes, and polyacetal (POM, A mixture of two or more selected from among polyacetal), polypropylene (PP), polyethylene (PE, plyethylene), and amorphous polyalphaolefin (APAO) may be used.

One exemplary step for manufacturing a metal powder injection molded product is as follows.

1) Kneading

The above step is a process of mixing a binder with metal powder. This is the step of preheating the kneader to 100 to 250 degrees and putting pre-weighed metal powder and binder into the kneader to produce a metal powder-binder mixture. For example, metal powder and binder are put into a kneader set at 100 to 250 degrees, preferably 140 to 170 degrees, and mixed. At this time, the binder melts due to the high temperature and penetrates between the powders to form dough. This process can be carried out for about 1 to 3 hours to ensure that the binder is evenly mixed between the metal powders, thereby producing a metal powder binder mixture.

2) Injection

The above step is to manufacture the shape of a metal powder injection molded product by putting the metal powder binder mixture into the injection molding machine and moving it to the mold through a nozzle. The injection machine feeds the metal powder binder mixture through the material input port and pushes the material out with a screw. At this time, the speed of the screw is 20 to 50 m/s, and the temperature of the nozzle is preferably 120 to 150 degrees. The material coming out through the nozzle moves to the mold and takes the shape of the product in the mold. During injection, it is advisable to apply a holding pressure of about 800 to 1000 kgf and set the mold temperature to 30 to 50 degrees.

3) Supercritical degreasing

This step is to remove wax from the metal powder injection molded product by putting carbon dioxide into a supercritical state with a high diffusion rate and low surface tension. Carbon dioxide in a supercritical state quickly penetrates into the micropores of metal powder injection molded products and quickly escapes after waxing, enabling effective degreasing. A preferred example of the supercritical degreasing step is performed at a pressure of 200 to 250 bar and a temperature of 70 to 80° C. for 5 to 10 hours.

4) Heat degreasing

The above step is a step of removing the polymer material, which is one of the binder components, by applying heat to the metal powder injection molded product that has completed the degreasing step. After removing the wax in the supercritical degreasing step, the remaining polymer material, which is a binder component, is completely removed by applying heat at over 300℃. A preferred example of the thermal degreasing step is maintaining it at 300°C for 30 minutes under an argon atmosphere and then maintaining it at 450°C for 30 minutes.

5) Sintering

The above step is to manufacture a basic metal frame product by sintering the degreased metal powder injection molded product in a sintering furnace set at 900 to 1,600 degrees. In the above range, sintering of the metal powder proceeds easily, and the mechanical strength and surface properties of the sintered body are excellent. If the sintering temperature is less than 900 degrees, the surface properties and mechanical properties of the sintered body may deteriorate, and if the sintering temperature exceeds 1600 degrees, the mechanical properties of the sintered body may deteriorate. The sintering may be performed in a gas atmosphere containing one or more of hydrogen or argon or under vacuum conditions. When sintering in a gas atmosphere or vacuum, oxidation due to the introduction of oxygen can be prevented.

One specific example for manufacturing a metal powder injection molded product according to the present invention is as follows.

SUS316, one of the stainless steel alloys, is used as a metal powder and mixed with a binder in the same volume ratio as shown in Table 1 to produce a metal powder binder mixture. In Table 1, the composition ratio of the wax and the polymer material constituting the binder is expressed in weight percent, and the composition ratio of the binder and metal powder constituting the metal powder binder mixture is expressed in volume percent.

Metal powder with a particle size of 2 to 20 ㎛ can be used as a metal powder for the production of SUS metal powder injection molded products. As a binder, various waxes and various polymer materials can be used. Preferably, paraffin wax, carnauba wax, and mixtures thereof with a melting point of 55 to 75 degrees and a density of 0.85 to 0.92 can be used, and the polymer material can be used as a binder. Polyacetal (POM) has a melting point of 140 to 170 degrees and a density of 1.05 to 1.20; polypropylene (PP) has a melting point of 130 to 165 degrees and a density of 0.85 to 0.97; and has a melting point of 95 to 135 degrees. Polyethylene (PE, plyethylene) with a density of 0.91 to 0.97, amorphous polyalphaolefin (APAO) with a melting point of 90 to 100 degrees and a density of 0.85 to 0.92, and mixtures of two or more selected from these may be used.

The binder may include 45 to 55% by weight of paraffin wax, 1 to 10% by weight of carnauba wax, 10 to 20% by weight of polypropylene, 25 to 35% by weight of polyacetal, and 1 to 10% by weight of amorphous polyalphaolefin. , more preferably 45 to 50% by weight of paraffin wax, 1 to 5% by weight of carnauba wax, 10 to 15% by weight of polypropylene, 25 to 30% by weight of polyacetal, and 1 to 5% by weight of amorphous polyalphaolefin. You can.

The amorphous polyalphaolefin used as the polymer material improves the cohesion of the metal powder binder mixture and improves the shape stability of the metal powder injection molded product, making it possible to obtain an excellent metal border basic product upon sintering.

A metal powder binder mixture having a composition ratio according to Table 1 is injected into a mold to manufacture a metal powder injection molded product of the type shown in FIG. 3. The metal powder injection molded product has dimensions of 156 mm in width, 74 mm in height, and 9 mm in thickness, and the width of the side wall of the molded product is 7 mm.

The composition ratio of the binder and whether injection is possible depending on the composition ratio of the binder and metal powder are as described in ‘Evaluation of injection performance’ in Table 1.

'○' written in 'Injection performance evaluation' means that the metal powder binder mixture is stably molded into the form of a metal powder injection molded product, '△' means that the shape is maintained but internal defects occur, and '×' means that the metal powder binder mixture does not take the shape of a metal powder injection molded product within the mold.

As shown in Table 1, a metal powder binder mixture containing 40 to 60% by weight of wax and 40 to 60% by weight of polymer material used at 27.5 to 57.5% by volume and metal powder at 42.5 to 72.5% by volume showed good injection performance. indicates.

If the metal powder exceeds a certain volume percentage, the fluidity of the metal powder binder mixture is insufficient, which can easily cause clogging of the injection machine and easily stick to the mold. Also, if the content of the metal powder is too low, the fluidity is high, so molding does not occur and contamination of the mold is likely to occur.

The stably molded metal powder injection molded product is subjected to supercritical degreasing and heat degreasing, and then fixed to a support means as shown in FIG. 3 and then sintered to manufacture a basic metal frame product.

In particular, sintering according to the present invention is preferably performed by raising the temperature to about 1300 degrees in the sintering furnace, but controlling the temperature increase rate to 0.5 degrees or less, which is slower than the commonly used temperature increase rate of 1 to 5 degrees per minute. This is because the fixing bases formed at both ends along the longitudinal direction of the side wall of the molded product are restrained by fixing pins, and sintering proceeds while the longitudinal deformation is suppressed. Therefore, deformation in directions other than the longitudinal direction of the side wall is induced, which occurs in the side wall. This is because an appropriate temperature increase rate per minute is required to prevent rupture.

Metal powder injection molded products manufactured from metal powder binder mixtures are prone to deformation due to shrinkage during sintering, and product defects occur due to distortion, cutting, etc. due to deformation. The state of the basic metal frame product manufactured by sintering the metal powder injection molded product is as described in ‘Sintered state’ in Table 1.

'◎' written in 'sintered state' means that the metal powder injection molded product has been sintered very stably in the form of a basic metal frame product, '○' means that it has been stably sintered, and '△' means that there is some deformation. In case of occurrence, '×' indicates a case in which the basic metal frame product did not take shape due to severe deformation.

As shown in Table 1, injection of metal powder prepared from a metal powder binder mixture containing 40-60% by weight of wax and 60-40% by weight of polymer material, using 35-52.5% by volume and containing 47.5-65% by volume of metal powder. The molded product can be sintered into a good metal frame base product, especially for metals containing 40 to 45% by volume of a binder composed of 40 to 60% by weight of wax and 40 to 60% by weight of polymer material and 55 to 60% by volume of metal powder. Metal powder injection molded parts prepared from the powder mixture can be sintered into very good metal frame base products.

Table 1. Examples of metal powder injection molded products using SUS metal powder binder mixture number Mixture for metal powder injection molding (volume %) Injection performance evaluation sintered state SUS316 bookbinder Composition ratio (% by weight) wax polymer materials Example 1 40 60 30 70 × Example 2 42.5 57.5 40 60 ○ × Example 3 45 55 50 50 ○ × Example 4 47.5 52.5 60 40 ○ ○ Example 5 50 50 70 30 × Example 6 52.5 47.5 30 70 × Example 7 55 45 40 60 ○ ◎ Example 8 57.5 42.5 50 50 ○ ◎ Example 9 60 40 60 40 ○ ◎ Example 10 62.5 37.5 70 30 × Example 11 65 35 30 70 × Example 12 67.5 32.5 40 60 ○ △ Example 13 70 30 50 50 ○ × Example 14 72.5 27.5 60 40 ○ × Example 15 75 25 70 30 × Example 16 65 35 60 40 ○ ○ Example 17 65 35 40 60 ○ ○

A preferred binder composition includes 45-55% by weight of paraffin wax and 1-10% by weight of carnauba wax as wax components, and 10-20% by weight of polypropylene, 25-35% by weight of polyacetal, and amorphous poly as polymer material components. When 1 to 10% by weight of alpha olefin is used, good injection performance and sintering state are shown, and more preferably, 45 to 50% by weight of paraffin wax, 1 to 5% by weight of carnauba wax, 10 to 15% by weight of polypropylene, and poly It may contain 25-30% by weight of acetal and 1-5% by weight of amorphous polyalphaolefin.

The above example illustrates a method of manufacturing a metal frame base product having the same form as shown in Figure 3, but is not limited thereto and includes not only the metal frame base product according to the present invention, but also a metal frame base having various shapes and thicknesses. Can be applied to products.

By separating the metal powder injection molded product that has gone through the sintering process from the inner corner support of the support means, a basic metal frame product as shown in FIG. 2 can be obtained.

One specific example of another form for manufacturing a metal powder injection molded product according to the present invention is as follows.

Titanium hydride with a particle size of 5-30㎛ is used as a metal powder and mixed with a binder in the same volume ratio as shown in Table 2 to prepare a metal powder binder mixture.

Titanium is a non-magnetic material and has a low coefficient of thermal expansion and excellent oxidation resistance. It has superior strength compared to other metal materials such as SUS alloy steel and carbon steel, but its specific gravity is low, so it has the advantage of being able to produce lightweight metal frame basic products. On the other hand, it is difficult to mass-produce metal frames using titanium due to its high melting point and difficult processing.

In particular, titanium hydride, to which metal powder injection molding can be applied, inevitably experiences greater shrinkage due to the dehydrogenation reaction during sintering, making it more difficult to manufacture metal frames using metal powder injection molding products.

The manufacturing process of the basic metal frame product using titanium hydride is the same as the case using the above-mentioned SUS metal powder unless specifically mentioned.

The preferred binder composition when titanium hydride metal powder is used is as follows. As a binder, it may contain 40 to 60% by weight of paraffin wax with a melting point of 55 to 75 degrees and a density of 0.85 to 0.92, and as a polymer material component, 15 to 30% polypropylene with a melting point of 130 to 165 degrees and a density of 0.85 to 0.97. % by weight, may include 10 to 30% by weight of polyethylene with a melting point of 95 to 135 degrees and a density of 0.91 to 0.97, and 1 to 10% by weight of amorphous polyalphaolefin with a melting point of 90 to 100 degrees and a density of 0.85 to 0.92; , more preferably 55 to 60% by weight of paraffin wax, 15 to 20% by weight of polypropylene, 15 to 20% by weight of polyethylene, and 1 to 5% by weight of amorphous polyalphaolefin.

The ‘injection performance evaluation’ in Table 2 shows whether injection is possible depending on the composition ratio of the binder and the composition ratio of the binder and metal powder.

As shown in Table 2, a metal powder mixture containing 40-60% by weight of wax and 40-60% by weight of polymer material using 25-55% by volume of binder and 45-75% by volume of metal powder shows good injection performance. .

Stably molded metal powder injection molded products are subjected to supercritical degreasing and heat degreasing.

When titanium hydride is used, the degreasing process must be carried out under a hydrogen atmosphere. Although not specifically listed in Table 2, even for stably molded metal powder injection molded products, if the degreasing process does not proceed in a hydrogen atmosphere and the degreasing process proceeds in a non-hydrogen atmosphere, the sintering condition will be poor in the next sintering process. . This is because hydrogen escapes during the degreasing process, and even metal powder injection molded products in good condition are deformed after sintering.

The metal powder injection molded product that has completed the degreasing process is fixed to a support means as shown in Figure 3 and then sintered to manufacture a basic metal frame product.

In particular, in the titanium hydride according to this embodiment, hydrogen escapes during sintering, resulting in greater shrinkage compared to metal powder molded products using SUS metal powder. Therefore, if the side wall of the molded product and the inner corner support are placed in contact with each other (i.e., when the confinement gap is 0%), the side wall of the molded product will be distorted or cracked during sintering. Therefore, when fixing a degreased metal powder injection molded product to a support means, it is necessary to maintain a certain distance between the inner corner of the side wall of the molded product and the inner corner support.

A certain distance between the inner part of the side wall corner of the molded product and the inner corner support is expressed as the confinement interval, and the confinement interval is calculated by dividing the distance between the side wall of the molded product and the inner corner support by the length of the molded product in the distance direction between the side wall of the molded product and the inner corner support. It is defined as half the value multiplied by 100.

As shown in Table 2, 35 to 55% by volume is used as a binder consisting of 40 to 60% by weight of wax and 40 to 60% by weight of polymer material, and 1.5 to 5.5% of metal powder injection molded products contains 45 to 75% by volume of metal powder. When fixed to a support means with a restraining interval of , the desired metal frame base product can be obtained. In particular, if the restraint interval is 1.5 to 5%, a metal frame base product with a good shape can be obtained.

Figures 4 to 6 show metal powder injection molded product systems that can simultaneously laminate and sinter two or more metal powder injection molded products as another embodiment of the present invention.

Example of metal powder injection molded product using titanium hydroxide metal powder and binder mixture number Mixture for metal powder injection molding (volume %) Injection performance evaluation restraint interval sintered state titanium hydride bookbinder Composition ratio (% by weight) wax polymer materials Example 18 30 70 30 70 × Example 19 35 65 40 60 ○ 0.5% × Example 20 40 60 50 50 ○ One% × Example 21 45 55 60 40 ○ 1.5% ○ Example 22 50 50 70 30 × Example 23 50 50 30 70 × Example 24 55 45 40 60 ○ 3% ○ Example 25 55 45 50 50 ○ 3.5% ○ Example 26 60 40 60 40 ○ 4% ○ Example 27 60 40 70 30 × Example 28 65 35 30 70 △ 5% △ Example 29 70 30 40 60 ○ 4% ○ Example 30 70 30 40 60 ○ 5.5% △ Example 31 75 25 50 50 ○ 6% △ Example 32 30 70 60 40 ○ 0% × Example 33 35 65 70 30 × Example 34 40 60 30 70 × Example 35 45 55 40 60 ○ 1.5% ○ Example 36 50 50 50 50 ○ 2% ○ Example 37 50 50 60 40 ○ 2.5% ○ Example 38 55 45 70 30 × Example 39 55 45 30 70 × Example 40 60 40 40 60 ○ 4% ○ Example 41 60 40 50 50 ○ 4.5% ○ Example 42 65 35 60 40 ○ 5% △ Example 43 70 30 70 30 △ 5.5% △ Example 44 75 25 30 70 △ 6% △

Referring to FIG. 4, a plurality of metal powder injection molded products 200 are disposed on a plurality of support means 614 and arranged on each support means by a multi-connected inner corner support 242 that penetrates the plurality of support means. It represents a metal powder injection molding system in which the inner corner of the metal powder injection molded product is fixed. In other words, since a plurality of support means are provided so that metal powder injection molded products can be combined to be stacked along the thickness direction, multiple metal frame base products can be produced simultaneously.

Referring to FIG. 5, one support means 714 is provided with a multi-connected inner corner support 742, and a plurality of metal powder injection molded products are separated by a spacer 700a disposed on the multi-connected inner corner support. 700 represents a metal powder injection molding system arranged along the height direction.

Referring to Figure 6, a pair of support means arranged perpendicularly to the ground and spaced apart from each other in parallel are provided, and a multi-connected inner corner support 742 is fixed perpendicular to the two support means, and the It shows a metal powder injection molding system in which a plurality of metal powder injection molded products 700 are separated and fixed to a connected inner corner support 742 by a spacer 700a. That is, the inside of the corner portion of each of the plurality of metal powder injection molded products may be arranged to be stacked perpendicular to the ground while hanging from the multi-connected inner corner support 742.

The support means, the multi-connected inner corner support, and the spacing member of the metal powder injection molded product system may contain a non-reactive material to prevent reaction with the metal powder injection molded product during sintering. The method of including the non-reactive material is Same as described above.

In another embodiment of the present invention, various means for further supporting the side wall of the metal powder injection molded product may be further provided, an example of which is shown in FIG. 7. As shown, the metal powder injection molded product system for a metal border may further include a guide material for forming various shapes such as the thickness and width of the side wall of the molded product, and the guide material 150 shown in FIG. 7 is the side wall of the molded product ( By supporting the thickness direction of 100), it helps form a thin-thick part during sintering, and the shape of the basic metal frame product can be changed in various ways due to the use of the guide material, making it possible to manufacture metal frames with various shapes. do.

The guide material in FIG. 7 is illustrated as supporting the thickness direction of the side wall of the metal powder injection molded product, but the guide material may be configured to support the inner side, outer side, inner and outer side, or width direction of the side wall of the molded product. In addition, when the side wall of the molded product is long and it is difficult to support the side wall of the molded product with only the inner corner support, a guide material may be added to a part of the side wall of the molded product to prevent the side wall of the molded product from being deformed during sintering.

The guide material must also be constructed so that no reaction occurs with the metal powder injection molded product during sintering, and the above-described method can be used for this method.

In the method of manufacturing a basic metal frame product according to various embodiments of the present invention, the sintering process is carried out in a state in which a support means for fixing the inner part of the corner is provided in the metal powder injection molded product, so that the length deformation that occurs during the sintering process is minimized and the size is reduced. Basic metal frame products with excellent precision can be manufactured reliably. As a result, it is possible to manufacture metal frame products of the desired shape by dramatically reducing the amount of post-processing, thereby significantly saving the manufacturing process time and cost of metal frame products, and making mass production possible.

As described above, the method for manufacturing a basic metal frame product according to the present invention has been described with reference to the illustrative drawings, but the present invention is not limited by the embodiments and drawings described above, and the technology to which the present invention pertains within the scope of the patent claims. Various implementations are possible by those with ordinary knowledge in the field.

100, 200, 500, 700: side wall
501, 502, 503, 504: Edges
514, 614, 714: means of support
700a: Separation member
242, 541, 542, 543, 742, : inner corner support or multi-connected corner inner support
150: Guide material

Claims (22)

A metal powder injection molded product including side walls for manufacturing metal frame base products - the side walls of the molded product are arranged to intersect each other, so that the metal powder injection molded product has a closed shape; and a support means disposed on a portion of the inner side of a corner where the side walls of the molded product intersect to prevent the side wall of the molded product from shrinking in the longitudinal direction during sintering. The metal powder injection molded product system according to claim 1, wherein the support means includes an inner corner support fixed to one side of the support means. The metal powder injection molded product system according to claim 1 or 2, wherein the support means is treated so as not to react with the side walls of the molded product. The method of claim 3, wherein the support means is treated so that it does not react with the side walls of the molded article.
(a) the entire support means is made of a non-reactive material that does not react with the side walls of the molded article, or
⒝ Place a non-reactive material that does not react with the sidewall of the molded article outside the support means, or
⒞ A metal powder injection molded product system, characterized in that it is manufactured by applying a non-reactive material or solution to at least one surface where the support means and the side wall of the molded product contact each other and drying or sintering. The metal powder injection molded product system according to claim 1, wherein the metal powder injection molded product includes a metal powder binder mixture in which metal powder and a binder are mixed. The method according to claim 5, wherein the metal powder binder mixture includes 47.5 to 65% by volume of stainless alloy steel metal powder; 35-52.5% by volume of binder consisting of 40-60% by weight of wax and 40-60% by weight of polymer material; A metal powder injection molded product system characterized in that it is included. The method according to claim 5, wherein the metal powder binder mixture includes 55 to 60% by volume of stainless alloy steel metal powder; 40 to 45% by volume of binder consisting of 40 to 60% by weight of wax and 40 to 60% by weight of polymer material; A metal powder injection molded product system characterized in that it is included. The method of claim 6 or 7, wherein the binder contains 45 to 55% by weight of paraffin wax and 1 to 10% by weight of carnauba wax, and the polymer material components include 10 to 20% by weight of polypropylene, 25 to 35% by weight of polyacetal, Metal powder injection molded product system containing 1 to 10% by weight of amorphous polyalphaolefin. The method of claim 8, wherein the binder is 45 to 50% by weight of paraffin wax, 1 to 5% by weight of carnauba wax, 10 to 15% by weight of polypropylene, 25 to 30% by weight of polyacetal, and 1 to 5% by weight of amorphous polyalphaolefin. A metal powder injection molded product system including. The method according to claim 5, wherein the metal powder binder mixture includes 45 to 75% by volume of titanium hydride metal powder; 25-55% by volume of binder consisting of 40-60% by weight of wax and 40-60% by weight of polymer material; A metal powder injection molded product system characterized in that it is included. The metal powder injection method according to claim 10, wherein the binder contains 40 to 60% by weight of paraffin wax, 15 to 30% by weight of polypropylene, 10 to 30% by weight of polyethylene, and 1 to 10% by weight of amorphous polyalphaolefin. Molded product system. The metal powder injection method according to claim 11, wherein the binder contains 55 to 60% by weight of paraffin wax, 15 to 20% by weight of polypropylene, 15 to 20% by weight of polyethylene, and 1 to 5% by weight of amorphous polyalphaolefin. Molded product system. The metal powder injection molded product system according to claim 12, wherein the restraining interval between the support means and the metal powder injection molded product is set to 1.5 to 5.5%. The metal powder injection molded product system according to claim 13, wherein the confinement interval is 1.5 to 5%. The metal powder injection molded product system according to claim 2, wherein the metal powder injection molded product has a polygonal shape, and a portion of the inner corner support has a shape that matches the inner side of the corner portion of the polygonal shape. The method according to claim 2, wherein a plurality of metal powder injection molded products are stacked on a plurality of support means, and the inner corner support is disposed to penetrate the support means and is configured to be caught on the inside of a corner of the plurality of metal powder injection molded products. A metal powder injection molded product system characterized by consisting of a connected inner corner support. The method according to claim 2, wherein a plurality of metal powder injection molded products are stacked in a state separated by a spacing member, and an inner corner support fixed on a support means is configured to be caught on the inside of a corner of the plurality of metal powder injection molded products. A metal powder injection molded product system characterized by consisting of an inner corner support. The method according to claim 2, wherein two support means are arranged in a standing form facing each other, a plurality of metal powder injection molded products are disposed separated by spacers between the support means, and an inner corner is fixed through the two support means. A metal powder injection molded product system, characterized in that the support is composed of a multi-connected inner corner support configured to be hung on the inside of the corner portion of the plurality of metal powder injection molded products. The metal powder injection molded product system according to claims 16 to 18, wherein the support means and the multi-connected inner corner support are configured not to react with the side wall of the molded product. The metal powder injection molding system according to claim 1 or 2, wherein the metal powder injection molded product system further includes a guide supporting one or more of the inner surface, outer surface, inner and outer surface, width direction, or thickness direction of the side wall of the molded product. Molded product system. The metal powder injection molded product system according to claim 20, wherein the guide material is configured not to react with the side wall of the molded product. Designing the shape of a metal powder injection molded product;
Manufacturing a mold according to the shape;
Injecting the metal powder binder mixture into a mold manufactured to fit the shape of the metal powder injection molded product - the metal powder injection molded product includes molded product side walls for manufacturing a metal border, and the molded product side walls are arranged to cross each other to form a metal powder injection molded product. has a closed shape;
After supercritical degreasing and heat degreasing of the metal powder injection molded product, it is placed on the inside of the corner where the side walls of the molded product intersect and is fixed on a support means that prevents the side wall of the molded product from shrinking in the longitudinal direction during sintering and then sintered. step;
A method of manufacturing a metal frame base product comprising: separating the metal frame base product from the support means.