JP2017024012A - Method for manufacturing powder press-molded body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inexpensively and simply provide a plurality of molded bodies which have the same shape and size and are free from a crack, scratch and a chip using a resin mold which is three-dimensionally shaped using an optical shaping method or a three-dimensional printer without structurally damaging the resin mold, where a sintered product of the molded body is not inferior in strength to a sintered product formed by a metal mold.SOLUTION: A powder press-molded body is manufactured by press-molding raw material powder filling a die cavity formed of a lower punch and a die between upper and lower punches. The mold including the lower punch, the upper punch and the die is a resin mold formed of a photocurable resin containing only a material formed of a resin three-dimensionally shaped using an optical shaping method or a three-dimensional printer, the raw material powder is spherical granulated powder that is obtained by mixing metal powder or ceramic powder and a binder and has a powder grain size (D50) of 50-200 μm, 3-12 mass% of the binder is contained in 100 mass% of the granulated powder, and the granulated powder is press-molded at a press pressure of 50-300 MPa and a press temperature of a heat resistant temperature of the resin mold or lower.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing a molded body by press-molding a metal or ceramic raw material powder using a resin molding die made by an optical modeling method, a three-dimensional (3D) printer or the like.

  The powder press molding method is a method in which raw powder such as metal powder and ceramic powder is placed in a mold using a powder press molding apparatus, and is pressed into a desired product shape by applying a predetermined pressure. After press molding, the molded body can be sintered at a predetermined temperature to obtain a product. The powder press molding apparatus is usually composed of a press molding machine main body, a die set and a mold. The main body of the powder press molding machine has an upper ram for pressurization and a lower ram for demolding, and a die set consisting of an upper punch, a lower punch, a die and a core is attached to the die set. Filling, molding and demolding are performed automatically.

  Conventionally, the die of a powder press molding apparatus generally requires durability such as wear resistance, impact resistance, and chipping resistance, and tool steels such as cemented carbide, cast iron, cast steel, and forged steel are used ( For example, see Patent Documents 1 and 2.)

  On the other hand, as a mold used for injection molding, foam molding, RIM molding, casting, vacuum casting, vacuum molding, RTM molding, powder molding, blow molding, compression molding, press molding, extrusion molding, FRP molding, additive manufacturing method (See, for example, Patent Document 3). Patent Document 3 describes that the mold is superior in strength, wear resistance, durability, and releasability as compared with the conventional mold, and can shorten the time for producing the mold. . This mold is made by a layered manufacturing method using a composite material powder containing spherical carbon and resin powder as essential components.

JP 2005-152961 A (paragraph [0002], paragraph [0004]) JP 2004-306119 A (paragraph [0023]) JP 2010-234800 A (summary, claim 1, paragraph [0001])

  In the case of manufacturing a molded body having a complicated shape with a mold using the tool steel shown in Patent Documents 1 and 2, it takes a lot of manufacturing days and manufacturing costs to manufacture the mold, and a mass-produced product is manufactured. In the previous stage, it was not possible to produce a prototype by this press molding method from the viewpoint of production days and production costs. Moreover, when using a composite material powder obtained by mixing a metal material, a ceramic material, and a resin, including a carbon material shown in Patent Document 3, the above tool steel was used when a resin mold was produced by an additive manufacturing method. While the problem of molds is solved, resin molds with increased strength or heat resistance have complicated compounding ratio settings for obtaining appropriate strength or heat resistance, and the raw materials and production costs have increased. There was a bug to do. Moreover, when powder press molding is performed using this type of resin mold, the press pressure cannot be higher than the press pressure by a mold using tool steel, and is present inside the molded body when it is made into a sintered product. There was a weakness in strength due to vacancies.

  The first object of the present invention is to use a resin molding die made of a photocurable resin that does not contain a material other than a resin that is three-dimensionally modeled using a stereolithography method or a three-dimensional printer. An object of the present invention is to provide a method for easily and inexpensively producing a powder press-molded body having no chip. The second object of the present invention is to provide a method for producing a powder press-molded body having a plurality of shapes having the same shape and the same size without structurally damaging the resin mold even if the molded body is repeatedly produced. is there. In addition, the third object of the present invention is to produce a powder press-molded body that is not inferior in strength compared to a sintered product of a molded body press-molded by a mold using tool steel. It is to provide a way to do.

  The present inventors have replaced a resin molding die by a layered molding method using a composite material powder in which a carbon material, a metal material, a ceramic material and a resin are mixed, and a material other than a resin by an optical modeling method or a three-dimensional printer. A resin-molding die made of a photo-curing resin containing no curable resin is prepared. On the other hand, as a raw material powder, a spherical granulated powder having a powder particle size (D50) containing 3 to 12 mass% of a binder and having a particle size of 50 to 200 μm If the press molding is repeated at a pressure of 50 to 300 MPa and a press temperature lower than the heat resistance temperature of the resin mold, the predetermined dimensions without cracks, scratches and chips are obtained without structurally damaging the resin mold. It is possible to easily and inexpensively produce multiple powder press-molded bodies of the same size and size as the streets, and when compared to sintered products of powder press-molded bodies made with conventional molds, the strength is inferior. Focusing on the absence, we have reached the present invention.

  According to a first aspect of the present invention, there is provided a method for producing a powder press-molded body by press-molding a raw material powder filled in a die cavity formed by a lower punch and a die between the lower punch and the upper punch. A molding die including a lower punch, the upper punch and the die is a resin molding die made of a photocurable resin that does not include a material other than a resin that is three-dimensionally modeled using an optical modeling method or a three-dimensional printer, The raw material powder is a spherical granulated powder having a powder particle size (D50) obtained by mixing a metal powder or ceramic powder and a binder of 50 to 200 μm, and 3% of the binder is contained in 100% by mass of the granulated powder. Powder press molding characterized by containing ~ 12% by mass, and performing press molding of the granulated powder at a press pressure of 50 to 300 MPa and a press temperature not higher than the heat resistance temperature of the resin mold. It is a method of manufacture.

  A second aspect of the present invention is an invention based on the first aspect, wherein the metal powder is iron powder, Ni powder, Co powder or a mixed powder thereof, alloy steel powder, stainless steel powder, corrosion-resistant alloy powder. Or a magnetic alloy powder.

A third aspect of the present invention is the invention based on the first aspect, wherein the ceramic powder is zirconia (ZrO ₂ ) powder, alumina (Al ₂ O ₃ ) powder, or aluminum nitride (AlN) powder. It is characterized by.

  A fourth aspect of the present invention is the invention according to any one of the first to third aspects, wherein the binder is polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC). Or any of polyethylene glycol (PEG) or a combination thereof.

  A fifth aspect of the present invention is a method for producing a sintered product by sintering a powder press-molded body produced by the method of any one of the first to fourth aspects.

  In the method for producing a powder press-molded body according to the first aspect of the present invention, powder is produced using a resin-made mold made of a photocurable resin that does not contain a material other than a resin made by an optical modeling method or a three-dimensional printer. In order to produce a press-molded body, it is manufactured by the additive manufacturing method using a composite material powder in which an expensive metal mold and carbon material, metal material, ceramic material and resin mixed with conventional machining are used. Compared with the conventional resin mold, the molded product can be produced easily and inexpensively. In particular, in the optical modeling method, the three-dimensional printer, and the like, even if the required shape of the product is complicated and fine, the shape of the resin mold can be created by faithfully and precisely matching the shape. In addition, a spherical granulated powder containing 3 to 12% by mass of a binder and having a powder particle size (D50) of 50 to 200 μm is used as a raw material powder, with a pressure of 50 to 300 MPa and a press temperature not higher than the heat resistance temperature of the resin mold. Even if it is a resin mold made of a single type of resin, the resin mold is elastically deformed during pressing and returns to the original mold after depressurization. Repetitive molding can be performed without causing damage. As a result, a plurality of powder press-molded bodies having the same shape and the same size can be produced without cracks, scratches and chips. In addition, in the conventional press molding with a mold or the like, a large pressing pressure is required when producing a green compact that retains its shape by crushing a metal powder or the like. If a green compact is formed by press molding without crushing metal powder or the like at a low temperature, and this powder press molded body is sintered, a sintered product whose strength does not decrease can be obtained. This makes it possible to easily manufacture powder press-molded bodies for prototypes such as toys, household goods, automobile parts, and electrical parts.

  The method for producing a powder press-molded body according to the second aspect of the present invention is a metal powder of iron powder, Ni powder, Co powder or a mixed powder thereof, alloy steel powder, stainless steel powder, corrosion-resistant alloy powder, or magnetic alloy powder. By using as a raw material powder, various metal molded bodies can be produced.

The method for producing a powder press-molded body of the third aspect of the present invention uses a ceramic powder of zirconia (ZrO ₂ ) powder, alumina (Al ₂ O ₃ ) powder or aluminum nitride (AlN) powder as a raw material powder, Various ceramic molded bodies can be manufactured.

  In the method for producing a powder press-molded body according to the fourth aspect of the present invention, water solubility of any one of polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), polyethylene glycol (PEG), or a combination thereof. This binder is used. Thereby, this binder aqueous solution and metal powder or ceramic powder can be mixed and slurried, and the desired granulated powder of metal powder or ceramic powder can be manufactured. Moreover, the compacting characteristics of the granulated powder are improved, and it is easy to degrease when the powder press-molded body is sintered.

  According to the method of the fifth aspect of the present invention, a sintered product is produced by sintering the powder press-molded body produced by the method of any one of the first to fourth aspects. Thus, it is possible to produce a sintered product made of metal or ceramic having a small variation in size and shape and having a strength not inferior to that of a sintered product of a powder press-molded body using a conventional mold.

It is a block diagram of the apparatus which manufactures the powder press molded object which concerns on embodiment of this invention. FIG. 1A shows a state in which raw material powder is filled in a die cavity, and FIG. 1B shows a state in which raw material powder is press-formed between upper and lower punches. It is a figure which shows the condition before filling raw material powder in the die cavity which concerns on embodiment of this invention. It is an external appearance perspective view of the powder press molding manufactured by embodiment of this invention. It is a schematic sectional drawing which shows the optical lamination molding method for manufacturing the lower punch which concerns on embodiment of this invention. FIG. 4A shows a state in which a first cured thin layer having a predetermined shape is formed, and FIG. 4B shows a state in which the table is moved slightly downward to form a second cured thin layer. FIG. 4C shows a state in which a lower punch which is an optically shaped object having a predetermined three-dimensional shape is formed. The sintered product obtained by the Example and the comparative example is shown. FIG. 5A shows a plan view thereof, and FIG. 5B shows a side view thereof. It is a figure which shows the bending test of the sintered product obtained in the Example.

  Next, modes for carrying out the present invention will be described with reference to the drawings.

[Production method of granulated powder as raw material powder]
Initially, the manufacturing method of the granulated powder which is a raw material powder for making a powder press molding body is demonstrated. The raw material powder of this embodiment is a granulated powder obtained by mixing metal powder or ceramic powder and a binder. Examples of the metal powder include iron powder, Ni powder, Co powder or a mixed powder thereof, alloy steel powder, stainless steel powder, corrosion-resistant alloy powder, and magnetic alloy powder. In particular, examples of stainless steel powder include SUS316L, SUS630, SKD11, and SKH57. Examples of the ceramic powder include zirconia (ZrO ₂ ) powder, alumina (Al ₂ O ₃ ) powder, and aluminum nitride (AlN) powder. The powder particle size (D50) of the metal powder or ceramic powder is preferably 20 μm or less. Furthermore, 10 μm or less is more preferable. In metal powder or ceramic powder having a particle size exceeding 20 μm, when formed into a press-molded body at the pressure described later, voids are formed between the powders, and the voids remain during sintering in the subsequent process. The density and strength of the steel tends to decrease. In this specification, the powder particle size (D50) means the median value of the particle distribution (diameter) measured by a laser diffraction scattering type particle distribution measuring device (model name: HORIBA LA-950) three times. Mean value.

  Examples of the binder include water-soluble binders such as polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), polyethylene glycol (PEG), or a combination thereof. The binder serves as a glue that aggregates metal powder or ceramic powder. This aqueous binder solution and a metal powder or ceramic powder can be mixed and slurried to produce a desired granulated powder of metal powder or ceramic powder. Moreover, when granulated powder is made with this binder, the compacting characteristics of the granulated powder are improved, and it is easy to degrease when the powder press-molded body is sintered.

  In order to produce granulated powder, first, the binder is dissolved in pure water to form an aqueous solution, and the metal powder or ceramic powder and the binder aqueous solution are mixed to form a slurry in which the metal powder or ceramic powder is uniformly dispersed. Here, a binder contains 3-12 mass% in a slurry, Preferably it contains 5-8 mass%. If it is less than 3% by mass, the particle size (D50) of the granulated powder to be produced is too small, and if it exceeds 12% by mass, the particle size (D50) of the granulated powder to be produced is too large. When the hardness of the metal powder or ceramic powder to be used is high, or when these powder particle sizes (D50) are small, it is preferable to contain much this binder within the said range.

  The granulating apparatus of this embodiment is configured as follows. A slurry tank for storing the slurry is disposed at the upper center of the inverted truncated cone-shaped cylinder, a rotating disk is horizontally disposed at the upper center of the cylinder, and hot air is further directed toward the cylinder at the upper part of the cylinder. A dryer that blows out is arranged. The lower end (conical tip) of the inverted truncated cone-shaped cylinder is opened, and a granulated powder collection container is disposed below the bottom. In order to make the granulated powder, a horizontally disposed disk is rotated at a speed of 10,000 to 20,000 rpm, and the slurry is dropped from the slurry tank at a rate of 300 to 500 kg / h on the rotating disk. The minute droplets of the slurry scattered from the disk become spherical granulated powder which is powder particles which are dried and aggregated by removing moisture by hot air from a dryer in the cylinder. Spherical granulated powder travels through the cone of the inverted truncated cone-shaped cylinder under its own weight, falls to the lower end of the cylinder, and enters the collection container from the lower opening of the cylinder.

  The granulated powder produced by the above method is a spherical powder having a powder particle size (D50) of 50 to 200 μm. This powder particle size (D50) is obtained by adjusting the binder concentration, the amount of slurry dropped per unit time, and the rotational speed of the disc. The powder particle size (D50) of the spherical granulated powder is preferably 80 to 100 μm. The spherical granulated powder is excellent in fluidity into a mold including an upper punch, a lower punch and a die, which will be described later. When the powder particle size (D50) of the granulated powder is less than 50 μm, the granulated powder is ejected from the clearance of the mold, and a desired press-molded product cannot be obtained. On the other hand, if it exceeds 200 μm, when the granulated powder is filled in the mold, it is difficult to fill the fine mold with the granulated powder or to fill the mold with the necessary and sufficient amount of granulated powder. Or pores remain between the granulated powders, and a press-formed body having a desired shape or a desired density cannot be obtained. The spherical granulated powder in the above-mentioned powder particle size (D50) range is shaped in three dimensions using a stereolithography or a three-dimensional printer, and even if the mold is complicated, every corner in the mold The granulated powder can be spread all the way to the above, and the moldability of the powder press-molded body described later can be improved.

[Production method of powder press-molded body]
Next, a method for producing a powder press-molded body using the granulated powder obtained by the above method will be described. First, an apparatus (hereinafter referred to as a powder press molding apparatus) for producing a powder press molded body according to an embodiment of the present invention will be described. As shown in FIG. 2, the powder press molding apparatus 10 according to this embodiment includes a powder feeding apparatus in a die cavity 14 formed by a die 12 attached to a die plate 11 and a lower punch 13 fitted to the die 12. An apparatus for filling granulated powder M, which is a raw material powder, from 20 and compression-molding granulated powder M in die 12 between upper punch 15 and lower punch 13 as shown in FIGS. 1 (a) and 1 (b). It is. A powder feeding device 20 shown in FIG. 2 is configured by connecting a hopper 16 provided at a high position for storing granulated powder, which is a raw material powder, and a box-shaped feeder 17 having no bottom, by a flexible hose 18. The The feeder 17 advances from the standby position shown in FIG. 2 toward the die (leftward in the figure) by the actuator drive rod 19, reaches the die 12, and feeds the granulated powder as raw material powder into the die cavity 14. Then, the granulated powder, which is the raw material powder poured into the die, is moved back to the standby position while the upper surface is flattened at the lower edge of the feeder 17 to complete one cycle of filling.

  As shown in FIGS. 1A and 1B, the lower punch 13 of the powder press molding apparatus 10 is fixed to a base 22 via a ground plate 21. The die plate 11 to which the die 12 is attached is supported by the column plate 24 via the column 23 penetrating the ground plate 21, and the column plate 24 is attached to the lower ram 26.

  In the powder press molding apparatus 10 configured as described above, the die 12 moves up and down simultaneously as the lower ram 26 moves up and down. As shown in FIG. 1 (a), the upper punch 15 is lowered and inserted into the die cavity 14 with respect to the die 12 that has been filled with the granulated powder M, which is a raw material powder, and has been raised. Then, the granulated powder that is the raw material powder is compressed. As shown in FIG. 1B, the granulated powder as the raw material powder is compressed by the upper punch 15, and the lower punch 13 is raised to further compress the granulated powder as the raw material powder. By pressing the granulated powder, which is a raw material powder, by the upper punch 15 and the lower punch 13, a powder press-molded body P shown in FIG.

  The press molding pressure when forming the powder press-molded body P is 50 to 300 MPa, preferably 100 to 200 MPa. When the press molding pressure is less than 50 MPa, the granulated powder is not easily broken or deformed by the press molding pressure, and voids remain in the powder press molded body. Even if this powder press molded body is sintered, the density of the sintered product And the strength cannot be increased. On the other hand, when the press molding pressure exceeds 200 MPa, a resin mold described later is worn during pressing, or cracks and cracks occur. Further, the press molding temperature does not need to be raised by special heating in this embodiment. The temperature of the resin mold due to frictional heat between the granulated powders when repeatedly press-molded, frictional heat when extruding the powder press-molded body from the mold, or the like may be lower than the heat resistance temperature of the resin mold.

  The mold composed of the die 12, the lower punch 13 and the upper punch 15 of the present embodiment is a resin mold, and is three-dimensionally formed using an optical modeling method or a three-dimensional printer. In this embodiment, the resin mold which is an optical modeling object is manufactured by the optical three-dimensional modeling method represented by the optical lamination modeling method. 4A to 4C show a process of modeling the lower punch 13 by an optical layered modeling method. The three-dimensional data of the shaped object corresponding to the lower punch 13 is acquired in advance, and the data is cut into circles at equal intervals and stored as slice data. As shown in FIG. 4 (a), it moves in the vertical direction so that the upper surface is located at a slight distance from the liquid surface 33 in the liquid tank of the container 32 containing the liquid photocurable composition 31. A possible table 34 is arranged. The liquid photocurable composition contains a radically polymerizable compound such as a (meth) acrylic monomer, a polymerizable monomer containing a cationically polymerizable compound such as an epoxy compound, a photopolymerization initiator, and the like. After arranging the table 34, the thin layer of the liquid photocurable composition 31 on the table 34 is scanned with the ultraviolet laser beam 37 from the ultraviolet laser device 36 in a predetermined pattern based on the stored data, A first cured thin layer 13a having a predetermined shape is formed. Next, as shown in FIG. 4B, by moving the position of the table 34 downward by a small distance, a thin layer of the liquid photocurable composition 31 is formed on the first cured thin layer 13a. After the formation, the ultraviolet laser beam 37 is scanned on the thin layer in a predetermined pattern based on the stored data to form the second cured thin layer 13b having a predetermined shape. Thereafter, the same operation is repeated, and finally, as shown in FIG. 4C, stereolithography having a predetermined three-dimensional shape that is an aggregate of a plurality of cured thin layers 13a, 13b,. The lower punch 13 which is a thing is obtained. Although not shown, the upper punch and the die are manufactured by the same method as that for the lower punch 13.

  In addition, the resin mold which is a modeled article of the present invention is not limited to the above-described optical layered modeling method, but is an inkjet ultraviolet curing method using an acrylic photocuring resin or an ABS resin (acrylonitrile) using a three-dimensional printer. A heat melting lamination method using butadiene / styrene copolymer synthetic resin) or a powder fixing method using powder may be used. In addition, the resin mold of the present invention does not include any material other than a resin intended to bring the strength or heat resistance of carbon materials, metal materials, ceramic materials, etc. close to those of conventional molds from the viewpoint of materials. Not. Therefore, the heat-resistant temperature of the resin mold of the present invention is in the range of 70 to 100 ° C., although it depends on the material of the raw material resin. In this specification, the “heat-resistant temperature of the resin mold” means that the material constituting the resin mold does not undergo degradation such as decomposition and dissolution, and maintains a structure equivalent to that at room temperature (25 ° C.). Says the highest temperature. Furthermore, the resin mold of the powder press molding apparatus of the present invention includes a die constituted by a die, a lower punch, an upper punch and a core.

[Method of manufacturing sintered product]
Next, a method for producing a sintered product using the powder press-molded product P obtained by the above method will be described. First, the powder press-molded body is degreased. In the degreasing step, the binder contained in the powder press molded body is removed. For example, the powder press-molded body is heat-treated at a temperature of 200 to 500 ° C. for 2 to 8 hours in the air and in a non-oxidizing atmosphere such as nitrogen gas.

  Subsequently, the degreased powder press-molded body is heated to 1000 to 1500 ° C. under a normal sintering condition, for example, a non-oxidizing atmosphere such as nitrogen gas in the atmosphere, and the temperature is 0.5 to 8 hours. Hold and baked. Thereby, a sintered product is obtained. Note that degreasing and sintering may be performed in separate heating furnaces or in the same heating furnace.

  Next, examples of the present invention will be described in detail together with comparative examples.

<Production example of granulated powder>
As shown in Table 1, granulated powder (No. 1 to No. 6) obtained by mixing SUS316L, which is stainless steel powder, and PVA, which is a binder, and zirconia (ZrO ₂ ) powder, which is a ceramic powder, and a binder. Seven types of granulated powder were produced using granulated powder (No. 7) mixed with CMC as raw material powder. The powder particle size (D50) of the stainless steel powders of No. 1 to No. 6 was all 7 μm, and the powder particle size (D50) of the zirconia powder of No. 7 was 0.09 μm. The particle size (D50) of the granulated powders No. 1 to No. 6 was adjusted to 45 to 210 μm by changing the content of CMC in the binder. The powder particle size (D50) of the granulated powder of No. 7 was adjusted to 80 μm.

<Example of mold production>
First, a molding die composed of a lower punch, an upper punch, and a die each made of an ultraviolet curable resin each modeled by a three-dimensional printer was prepared. Here, as shown in FIGS. 5 (a) and 5 (b), a dumbbell-shaped test piece S according to JISZ2201 No. 14 (thickness 3.5 mm, parallel part width 6 mm, parallel part length 30 mm, shoulder part) A mold was prepared so that a radius of 20R, a grip width of 10 mm, and a total length of 100 mm were obtained as a sintered product.

<Example 1>
The granulated powder containing SUS316L stainless steel powder of No. 3 shown in Table 1 is filled in the mold of the powder press molding apparatus, and the powder press molding is performed under the press molding pressure of 50 MPa and the powder press molding conditions at room temperature shown in Table 2. did. The molded body was degreased by holding it at a temperature of 320 ° C. for 120 minutes under a nitrogen gas atmosphere, and then the degreased molded body was held at a temperature of 1300 ° C. for 120 minutes under a nitrogen gas atmosphere and sintered as shown in FIG. I got a product.

<Example 2>
Under the same conditions as in Example 1 except that the granulated powder containing SUS316L stainless steel powder of No. 2 shown in Table 1 is filled in the mold of the same powder press molding apparatus as in Example 1 and the press molding pressure is 100 MPa. A sintered product was obtained by press molding, degreasing and sintering.

<Example 3>
Under the same conditions as in Example 1 except that the granulated powder containing SUS316L stainless steel powder of No. 3 shown in Table 1 is filled in the mold of the same powder press molding apparatus as in Example 1 and the press molding pressure is 100 MPa. A sintered product was obtained by press molding, degreasing and sintering.

<Example 4>
Under the same conditions as in Example 1 except that the granulated powder containing SUS316L stainless steel powder of No. 4 shown in Table 1 is filled in the mold of the same powder press molding apparatus as in Example 1 and the press molding pressure is 100 MPa. A sintered product was obtained by press molding, degreasing and sintering.

<Example 5>
Under the same conditions as in Example 1, except that the granulated powder containing SUS316L stainless steel powder of No. 5 shown in Table 1 is filled in the mold of the same powder press molding apparatus as in Example 1 and the press molding pressure is 100 MPa. A sintered product was obtained by press molding, degreasing and sintering.

<Example 6>
Under the same conditions as in Example 1, except that the granulated powder containing SUS316L stainless steel powder of No. 3 shown in Table 1 is filled in the mold of the same powder press molding apparatus as in Example 1 and the press molding pressure is 200 MPa. A sintered product was obtained by press molding, degreasing and sintering.

<Comparative Example 1>
The granulated powder containing stainless steel powder of No. 1 SUS316L shown in Table 1 was filled in the same mold of the powder press molding apparatus as in Example 1 and molded at a press molding pressure of 100 MPa. %, And the powder particle size (D50) of the granulated powder was as small as 45 μm, so a molded product having a desired shape could not be produced, and degreasing and sintering were not performed.

<Comparative example 2>
The granulated powder containing SUS316L stainless steel powder of No. 3 shown in Table 1 was filled in the mold of the same powder press molding apparatus as in Example 1 and molded at a press molding pressure of 45 MPa. The molding pressure was 45 MPa. Since it was low, the molded object which has a desired shape could not be made, and degreasing and sintering were not performed.

<Comparative Example 3>
The granulated powder containing SUS316L stainless steel powder of No. 3 shown in Table 1 was filled in the mold of the same powder press molding apparatus as in Example 1 and molded at a press molding pressure of 210 MPa. The molding pressure was 210 MPa. Since it was high, the lower punch and the upper punch were cracked and could not be molded. For this reason, degreasing and sintering could not be performed.

<Comparative example 4>
Under the same conditions as in Example 1, except that the granulated powder containing SUS316L stainless steel powder of No. 6 shown in Table 1 is filled in the mold of the same powder press molding apparatus as in Example 1 and the press molding pressure is 100 MPa. A sintered product was obtained by press molding, degreasing and sintering.

<Reference Example 1>
The same powder press molding apparatus as in Example 1, except that the lower punch, the upper punch and the die of the mold are made of tool steel and contain No. 3 SUS316L stainless steel powder shown in Table 1. Granules were filled in a mold, and press-molded at room temperature with a press-molding pressure of 300 MPa. The molded body was degreased and sintered under the same conditions as in Example 1 to obtain a sintered product.

<Example 7>
The granulated powder containing No. 7 zirconia powder shown in Table 1 is filled in the same mold of the powder press molding apparatus as in Example 1, and the powder is pressed under the press molding conditions of 200 MPa and room temperature under the conditions shown in Table 2. Press molded. The molded body was degreased by holding it at a temperature of 500 ° C. for 120 minutes in a nitrogen gas atmosphere, and then the sintered body shown in FIG. I got a product.

<Comparison result 1 (Press evaluation and presence or absence of breakage of mold)>
About the molded object press-molded by Examples 1-7, Comparative Examples 1-4, and Reference Example 1, in order to confirm whether the shape was hold | maintained after shaping | molding, the presence or absence of a crack, a crack, and a chip | tip was determined visually. Further, the presence or absence of breakage of the upper punch, the lower punch, and the die was visually determined. These results are shown in Table 3.

<Comparison result 2 (evaluation of sintered product)>
For the sintered products of SUS316L obtained in Examples 1 to 7, Comparative Example 4 and Reference Example 1, the relative density with respect to the theoretical density (100%) was obtained as a percentage by Archimedes method, and Examples 1 to 6 and Reference About the dumbbell-shaped test piece according to No. 14 of JISZ2201 which is a sintered product of SUS316L of Example 1, the tensile strength was measured at room temperature according to JISZ2241 (2011) (metallic material tensile test method). The results are shown in Table 3. As shown in FIG. 6, the dumbbell-shaped test piece S, which is a sintered product of the zirconia powder of Example 7, is placed on two fulcrums 41, 41 having a distance between fulcrums of the substrate 40 of 20 mm. A load was applied to the position T corresponding to the center of the fulcrums 41, 41 at a speed of 1 mm / min at room temperature, a three-point bending test was performed, and the bending strength was measured. The bending strength was the value of stress when the bending load reached the maximum. The results are shown in Table 4.

  As is apparent from Table 3, in Reference Example 1 in which a mold was used as the mold, it was natural that the moldability was good and the mold was not damaged. As described above, in Comparative Examples 1 and 2, the mold was not damaged, but a molded body having a desired shape could not be produced. Further, in Comparative Example 3, the mold (upper and lower punches) was damaged and could not be molded. On the other hand, in Examples 1 to 6 and Comparative Example 4, a molded body having a desired shape could be produced, and the mold was not damaged. Regarding the relative density and the tensile strength, the relative density of the sintered product of SUS316L obtained in Reference Example 1 was as high as 97%, and the tensile strength was as high as 520 MPa. On the other hand, the relative density of the sintered product of SUS316L obtained in Comparative Example 4 was 89% lower than that of Reference Example 1, and the tensile strength was 404 MPa lower than that of Reference Example 1. This is presumably because the granulated powder of Comparative Example 4 had a high binder content of 13% by mass and the granulated powder had a powder particle size (D50) of 210 μm, so that pores remained in the powder press compact. . Moreover, the relative density of the sintered product of SUS316L obtained in Examples 1 to 6 is 93 to 96% which is slightly lower than that of Reference Example 1, and the tensile strength thereof is also 451 to 497 MPa. The tensile strength was almost the same. Thus, it was found that the sintered products of Examples 1 to 6 were not inferior in density and strength to the sintered product made from a powder press-molded body using a conventional mold. As is clear from Table 4, the relative density of the sintered product made from the zirconia powder obtained in Example 7 was 99%, which was the same as that of Reference Example 1, and the bending strength was 832 MPa.

<Comparison result 3 (repetitive press formability evaluation)>
Using the same powder press molding apparatus as in Example 1, the same granulated powder as in Example 1 is filled in a mold consisting of the same upper punch, lower punch and die as in Example 1, and powder press molding is repeated. It was. After 100 times of powder press molding, the upper punch, the lower punch and the die were visually inspected for cracks, scratches, chips and the like. In addition, the presence or absence of cracks, scratches, and chips in 100 press-formed bodies was visually determined. Further, it was visually determined whether the molded body was press-molded according to predetermined dimensions. As a result, the upper punch, the lower punch and the die had the same appearance as after the first press molding, and there were no cracks, scratches or chips. This is also demonstrated by the fact that the 100th press-molded body was the same shape and size as the first pressed body, and there were no cracks, scratches, or chips as with the upper punch, lower punch and die. It was.

M Granulated powder which is raw material powder P Powder press molding body 10 Equipment for producing powder press molding body (powder press molding equipment)
11 Die Plate 12 Die 13 Lower Punch 14 Die Cavity 15 Upper Punch 16 Hopper 17 Feeder 18 Flexible Hose 19 Drive Rod 21 Ground Plate 22 Base 23 Column 24 Column Plate 26 Lower Ram

  The method for producing a powder press-molded body of the present invention is used to easily and inexpensively produce a molded body for prototypes such as toys, daily goods, automobile parts, and electrical parts.

Claims (5)

In a method for producing a powder press-molded body by press-molding a raw material powder filled in a die cavity formed by a lower punch and a die between the lower punch and the upper punch,
The molding die including the lower punch, the upper punch, and the die is a resin molding die made of a photocurable resin that does not contain a material other than a resin that is three-dimensionally modeled using a stereolithography method or a three-dimensional printer. ,
The raw material powder is a spherical granulated powder having a powder particle size (D50) obtained by mixing a metal powder or ceramic powder and a binder of 50 to 200 μm, and 3% of the binder is contained in 100% by mass of the granulated powder. Containing ~ 12% by mass,
A method for producing a powder press-molded product, wherein the granulated powder is press-molded at a press pressure of 50 to 300 MPa and a press temperature not higher than a heat resistant temperature of the resin mold.   The method for producing a powder press-molded body according to claim 1, wherein the metal powder is iron powder, Ni powder, Co powder or a mixed powder thereof, alloy steel powder, stainless steel powder, corrosion-resistant alloy powder, or magnetic alloy powder. The method for producing a powder press-molded body according to claim 1, wherein the ceramic powder is zirconia (ZrO ₂ ) powder, alumina (Al ₂ O ₃ ) powder, or aluminum nitride (AlN) powder.   The powder press molding according to any one of claims 1 to 3, wherein the binder is polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), polyethylene glycol (PEG), or a combination thereof. Body manufacturing method.   A method for producing a sintered product by sintering a powder press-molded product produced by the method according to claim 1.

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