US20220176448A1 - Manufacturing system and manufacturing method of sintered product - Google Patents

Manufacturing system and manufacturing method of sintered product Download PDF

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Publication number
US20220176448A1
US20220176448A1 US17/603,346 US201917603346A US2022176448A1 US 20220176448 A1 US20220176448 A1 US 20220176448A1 US 201917603346 A US201917603346 A US 201917603346A US 2022176448 A1 US2022176448 A1 US 2022176448A1
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United States
Prior art keywords
sintered product
manufacturing system
powder
molded article
robot
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Abandoned
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US17/603,346
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English (en)
Inventor
Shin Noguchi
Tatsushi Yamamoto
Tetsuya Hayashi
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Sumitomo Electric Sintered Alloy Ltd
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Sumitomo Electric Sintered Alloy Ltd
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Assigned to SUMITOMO ELECTRIC SINTERED ALLOY, LTD., reassignment SUMITOMO ELECTRIC SINTERED ALLOY, LTD., ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: NOGUCHI, SHIN, YAMAMOTO, TATSUSHI, HAYASHI, TETSUYA
Publication of US20220176448A1 publication Critical patent/US20220176448A1/en
Abandoned legal-status Critical Current

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/12—Both compacting and sintering
    • B22F3/16—Both compacting and sintering in successive or repeated steps
    • B22F3/162—Machining, working after consolidation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/003—Apparatus, e.g. furnaces
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/005—Loading or unloading powder metal objects
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/24—After-treatment of workpieces or articles
    • B22F2003/247—Removing material: carving, cleaning, grinding, hobbing, honing, lapping, polishing, milling, shaving, skiving, turning the surface
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2301/00—Metallic composition of the powder or its coating
    • B22F2301/35—Iron
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
    • B22F2998/10—Processes characterised by the sequence of their steps

Definitions

  • the present invention relates to a manufacturing system and a manufacturing method of a sintered product.
  • Patent Literatures 1 and 2 describe a manufacturing method of a sintered product including: a preparation step of preparing raw material powder containing metal powder; a molding step of uniaxially pressing the raw material powder using a mold to fabricate a powder compact; a processing step of machining the powder compact to fabricate a processed molded article; and a sintering step of sintering the processed molded article to obtain a sintered product.
  • Patent Literature 2 it is recommended to set the average relative density of the whole powder compact to 93% or more in the molding step described above.
  • a manufacturing system includes: a molding apparatus configured to uniaxially press raw material powder containing metal powder to fabricate a powder compact whose whole or part has a relative density of 93% or more; a robot processing apparatus including an articulated robot configured to machine the powder compact to fabricate a processed molded article; and an induction heating sintering furnace configured to sinter the processed molded article by high frequency induction heating to fabricate a sintered product.
  • a manufacturing system includes: a processing apparatus configured to machine a powder compact following 3D data of a target product serving as a reference of a shape to fabricate a processed molded article; and a sintering apparatus configured to sinter the processed molded article to fabricate a sintered product.
  • FIG. 1 is an explanatory illustration showing an outline of a manufacturing method of a sintered product.
  • FIG. 2 is an explanatory illustration showing an example of each of apparatuses used in steps 1 and 2.
  • FIG. 3 is an overall configuration illustration showing an example of a manufacturing facility used in step 3.
  • FIG. 4 is a schematic configuration illustration showing an example of a molding apparatus used in a molding step.
  • FIG. 5 is a schematic configuration illustration showing an example of a processing apparatus used in a processing step.
  • FIG. 6 is a schematic configuration illustration showing an example of a sintering apparatus used in a sintering step.
  • FIG. 7 is a schematic configuration illustration showing an example of an inspection apparatus used in an inspection step.
  • FIG. 8 is an explanatory illustration showing an example of an apparatus used in step 4.
  • FIG. 9 is a schematic configuration illustration showing an example of a movable manufacturing system.
  • a manufacturer of sintered products When there is a customer who is considering replacing a current product with a sintered product, it is preferable for a manufacturer of sintered products to manufacture a sintered product following the current product of the customer as early as possible and present the manufactured sintered product as a sample to the customer.
  • Patent Literatures 1 and 2 however, delivery date of a sintered product to be presented to a customer as a sample is not taken into consideration.
  • an object of the present disclosure is to shorten the delivery date of a sintered product.
  • an object of the present disclosure is such that a manufacturing facility of a sintered product can be made compact.
  • the delivery date of a sintered product can be shortened.
  • a manufacturing facility of a sintered product can be made compact.
  • a manufacturing system includes: a molding apparatus configured to uniaxially press raw material powder containing metal powder to fabricate a powder compact whose whole or part has a relative density of 93% or more; a robot processing apparatus including an articulated robot configured to machine the powder compact to fabricate a processed molded article; and an induction heating sintering furnace configured to sinter the processed molded article by high frequency induction heating to fabricate a sintered product.
  • the induction heating sintering furnace capable of fabricating a sintered product in a shorter time than a belt type continuous sintering furnace, is provided, so that the delivery date of a sintered product can be shortened.
  • the robot processing apparatus needing an installation space smaller than that of a five-axis machining center, and the induction heating sintering furnace needing an installation space smaller than that of a belt type continuous sintering furnace, are provided, so that a manufacturing facility of a sintered product can be made compact.
  • the manufacturing system according to the present embodiment preferably further includes an acquisition unit configured to acquire 3D data of a target product serving as a reference of a shape.
  • the acquisition unit acquires 3D data of a target product serving as a reference of a shape, so that it becomes possible to execute, based on the acquired 3D data, an inspection of the sintered product, creation of a processing program, and the like, as described later.
  • the manufacturing system preferably further includes an inspection apparatus configured to execute, based on the 3D data of the target product, an inspection of at least one of dimensional precision of the sintered product and presence or absence of a defect.
  • the inspection apparatus executes the inspection described above, so that a sintered product with high precision comparable to a target product can be manufactured.
  • the manufacturing system preferably further includes a computer apparatus configured to create, based on the 3D data of the target product, a processing program for controlling operation of the robot processing apparatus such that the robot processing apparatus fabricates the processed molded article based on the processing program.
  • the computer apparatus creates the processing program described above, and the robot processing apparatus fabricates a processed molded article based on the processing program described above, so that the robot processing apparatus can be controlled to process a powder compact into substantially the same shape as a target product.
  • the robot processing apparatus preferably includes a plurality of the articulated robots, in which the plurality of the articulated robots includes a first robot configured to hold a tool for processing the powder compact and a second robot configured to hold the powder compact.
  • the relative density of the powder compact is 93% or more, so that even when cutting work is performed on the powder compact held by the second robot with the tool held by the first robot, the powder compact is not broken. Therefore, the powder compact can be quickly processed.
  • the tool can be brought into contact with the powder compact at an arbitrary angle, so that complicated processing can be quickly executed.
  • a manufacturing system includes a processing apparatus configured to machine a powder compact following 3D data of a target product serving as a reference of a shape to fabricate a processed molded article, and a sintering apparatus configured to sinter the processed molded article to fabricate a sintered product.
  • the processing apparatus machines a powder compact following the 3D data of a target product to fabricate a processed molded article, and the sintering apparatus sinters the processed molded article to fabricate a sintered product, so that a sintered product having substantially the same shape as the target product can be fabricated in a short time.
  • the delivery date of a sintered product can be shortened.
  • the manufacturing system according to the present embodiment preferably further includes a 3D scanner configured to acquire 3D data of the target product in a non-contact manner.
  • the 3D scanner acquires the 3D data of a target product in a non-contact manner, so that even when the 3D data of a target product does not exist, the 3D data of the target product can be quickly acquired.
  • the processing apparatus is a robot processing apparatus including an articulated robot
  • the robot processing apparatus needing an installation space smaller than that of a five-axis machining center, is included, so that a manufacturing facility of sintered products can be made compact.
  • the computer apparatus creates the processing program described above, so that the robot processing apparatus can be controlled to process a powder compact into substantially the same shape as a target product.
  • the manufacturing system according to the present embodiment preferably further includes an inspection apparatus configured to execute, based on the 3D data of the target product, an inspection of at least one of dimensional precision of the sintered product and presence or absence of a defect.
  • the inspection apparatus executes the inspection described above, so that a sintered product with high precision comparable to a target product can be manufactured.
  • the manufacturing system according to the present embodiment preferably further includes a molding apparatus configured to uniaxially press raw material powder containing metal powder to fabricate the powder compact whose whole or part has a relative density of 93% or more.
  • the molding apparatus uniaxially presses raw material powder containing metal powder to fabricate a powder compact having the relative density described above, so that a powder compact with high precision can be quickly obtained.
  • the delivery date of a sintered product can be shortened.
  • the sintering apparatus is preferably an induction heating sintering furnace configured to sinter the processed molded article by high frequency induction heating.
  • the induction heating sintering furnace can fabricate a sintered product in a shorter time than a belt type continuous sintering furnace, so that the delivery date of a sintered product can be shortened.
  • the induction heating sintering furnace needs an installation space smaller than that of a belt type continuous sintering furnace, so that a manufacturing facility of a sintered product can be made compact.
  • the processing apparatus is a robot processing apparatus including an articulated robot
  • the sintering apparatus is an induction heating sintering furnace configured to sinter the processed molded article by high frequency induction heating
  • apparatuses to be mounted on the mobile apparatus include the robot processing apparatus and the induction heating sintering furnace.
  • the robot processing apparatus and the induction heating sintering furnace are mounted on the mobile apparatus, so that these apparatuses can be transported to a point near the location of a customer. Therefore, a sintered product can be manufactured at a point near the location of a customer.
  • a sintered product can be delivered to a customer in a shorter time than when the sintered product is manufactured in a factory far from the location of the customer.
  • the apparatuses to be mounted on the mobile apparatus preferably include a 3D scanner configured to acquire the 3D data of the target product in a non-contact manner.
  • the 3D scanner acquires 3D data of a target product in a non-contact manner, so that even when a customer or a third party does not store 3D data of a target product, the 3D data of the target product can be quickly acquired.
  • the whole or part of the powder compact preferably has a relative density of 96% or more.
  • the manufacturing method according to the present embodiment is a manufacturing method of a sintered product, in which the sintered product is manufactured by using the manufacturing system according to any one of (1) to (14) described above.
  • the manufacturing method according to the present embodiment achieves the similar operation and effect to those of the manufacturing system according to any one of (1) to (14) described above.
  • FIG. 1 is an explanatory illustration showing an outline of a manufacturing method of a sintered product S.
  • a customer provides a manufacturer with a current product C, which is a current part that is incorporated into, for example, an in-house product (finished product).
  • the manufacturer manufactures the sintered product S following the current product C, and provides the customer with the manufactured sintered product S as a sample.
  • the manufacturing method of the sintered product S according to the present embodiment includes procedures of steps 1 to 5.
  • the manufacturer manufactures the sintered product S having substantially the same shape as the current product C through steps 1 to 5.
  • the outline of each of steps 1 to 5 will be described.
  • Step 1 Acquire 3D Data
  • Step 1 is a step of acquiring three-dimensional CAD (Computer Aided Design) data of a target product (current product C of a customer in the present embodiment), which serves as a reference of the shape of the sintered product S.
  • three-dimensional CAD data is also referred to as “3D data.”
  • step 1 3D data is acquired by reading, for example, an actual article of the current product C with a 3D scanner 1 .
  • the 3D scanner serves as an acquisition unit for the 3D data.
  • the 3D data designated by the customer or the like may be directly input to a computer apparatus 2 of step 2 by data transmission by e-mail, data transfer using a USB memory, or the like.
  • the 3D scanner 1 is unnecessary or not used, and the computer apparatus 2 serves as an acquisition unit for the 3D data.
  • Step 2 Create Molded Article Processing Program (Set Manufacturing Conditions)
  • Step 2 is a step of creating a molded article processing program (hereinafter, also referred to as a “processing program”) from the 3D data acquired in step 1.
  • processing program a molded article processing program
  • the processing program is a computer program for controlling operation of a molded article processing apparatus 32 used in step 3.
  • the processing program is created by the computer apparatus 2 storing, for example, CAD/CAM (Computer Aided Manufacturing) software.
  • Step 3 Manufacture Sintered Product by Processing Molded Article
  • Step 3 is a step of manufacturing the sintered product S by a manufacturing facility 3 .
  • the manufacturing facility 3 used in step 3 includes a step P2 in which the molded article processing apparatus (hereinafter, also referred to as a “processing apparatus”) 32 processes a powder compact M before sintering.
  • the processing apparatus 32 performs predetermined processing on the powder compact M in accordance with the processing program created in step 2.
  • Step 4 Correct Molded Article Processing Program (Optimize Manufacturing Conditions)
  • Step 4 is a step of correcting the processing program based on the 3D data of the sintered product S that is an accepted product manufactured in step 3.
  • the processing program is corrected by a computer apparatus 4 storing, for example, CAD/CAT (Computer Aided Testing) software.
  • a result of correcting the processing program is fed back to the processing apparatus 32 of step 3.
  • the result of correcting the processing program may be fed back to the computer apparatus 2 configured to create the processing program (step 2).
  • Step 5 Provide Sintered Product (Sample)
  • Step 5 is a step of determining one or more of the sintered products S manufactured by the corrected program of step 4 as a sample, and providing the sintered product S determined as the sample to the customer.
  • the customer provided with the sintered product S as a sample can compare the performance of the current product C with the performance of the sintered product S by, for example, an in-house test facility. When the performance of the sintered product S provided as a sample is higher than or equal to the performance of the current product C, the customer can replace the current product C with the sintered product S.
  • the manufacturing facility 3 (see FIG. 3 ) for processing the powder compact M that remains to be sintered is used in step 3, so that processing, such as cutting, is easily performed and productivity is excellent. Therefore, the sintered product S can be manufactured at a lower cost and with a shorter delivery date than, for example, a cast product or a forged product.
  • the customer can expect suppression of the manufacturing cost and shortening of the procurement period by replacing the current product C with the sintered product S.
  • the sintered products S such as sprockets, rotors, gears, rings, flanges, pulleys, vanes, or bearings to be incorporated into machines such as automobiles, can be manufactured.
  • the sintered products S are not limited to products in the automotive field. According to the manufacturing method of the present embodiment, sintered products S, such as turbine blades of aircrafts, artificial bones and artificial joints to be used in the medical field, or radiation shielding parts to be used in the nuclear field, can be manufactured, which can be used in a wide range of applications.
  • FIG. 2 is an explanatory illustration showing an example of each of apparatuses used in step 1 and step 2.
  • the apparatus used in step 1 includes a non-contact type three-dimensional shape measuring machine (hereinafter, referred to as a “3D scanner”) 1 .
  • the non-contact type 3D scanner 1 is an apparatus configured to sense unevenness of a surface (distance to an arbitrary point on a surface) without contacting an object, convert a result of the sensing into three-dimensional CAD data, and incorporate it into the computer apparatus 2 .
  • the 3D scanner 1 acquires three-dimensional coordinate data (X, Y, Z) of each point on the surface of an object while irradiating the object with light.
  • the 3D scanner 1 converts the acquired data of a group of points into polygon data to generate a mesh-like three-dimensional figure.
  • the 3D scanner 1 converts the data of a group of points constituting the three-dimensional figure into three-dimensional CAD data in a predetermined file format, and transmits the converted three-dimensional CAD data to the computer apparatus 2 connected to the 3D scanner 1 .
  • the non-contact type 3D scanner 1 is roughly divided into a “laser light type” and a “patterned light type.”
  • the laser light type is configured to scan an object while irradiating the object with laser beams, identify reflected light from the object by a light receiving sensor, and measure a distance to the object by trigonometry.
  • the patterned light type is configured to scan an object while irradiating the object with patterned light, identify a line of a striped pattern, and measure a distance from the scanner to the object.
  • the patterned light type can perform measurement faster than the laser light type. Therefore, in the example of FIG. 2 , a patterned light 3D scanner 1 is adopted. Examples of commercially available products of the patterned light 3D scanner 1 include KEYENCE VL-300 series.
  • the 3D scanner 1 shown in FIG. 2 is a stationary type
  • the 3D scanner 1 may be a handy-type scanner that a user can hold in a hand for measurement.
  • a file of the data may be directly read into the computer apparatus 2 , as shown in FIG. 2 . In this case, the work of scanning the actual current product C becomes unnecessary.
  • the acquisition source of the three-dimensional CAD data of the current product C may be a third party other than the customer.
  • the third party include a manufacturer of the current products C to whom the customer has entrusted the manufacture of the current products, or a company that specializes in disassembling finished products and reading the 3D data of the current product C.
  • the apparatus used in step 2 includes the computer apparatus 2 .
  • the computer apparatus 2 includes, for example, a desktop personal computer (PC).
  • the type of the computer apparatus 2 is not particularly limited.
  • the type of the computer apparatus 2 may be, for example, a notebook type or a tablet type.
  • the computer apparatus 2 includes: an information processor including a central processing unit (CPU) and a volatile memory; a storage device including a nonvolatile memory configured to store a computer program to be executed by the CPU and data necessary for the execution; and the like.
  • the computer apparatus 2 also includes an input device and a display.
  • the CPU reads the computer program into the volatile memory to execute the computer program, whereby the computer apparatus 2 functions as a predetermined controller.
  • the computer apparatus 2 has CAD/CAM software installed.
  • the CAD/CAM software is software that realizes creation of a processing program for operating the molded article processing apparatus 32 in accordance with a user's operation input to a graphical user interface (GUI) of the computer apparatus 2 .
  • GUI graphical user interface
  • CAD/CAM software for example, software such as “MasterCam” or “Robotmater” (both registered trademarks) can be adopted. These pieces of software can generate a processing program in accordance with the type of the molded article processing apparatus 32 (e.g., an articulated robot or a five-axis machining center). In addition, these pieces of software may be capable of generating the processing program described in Japanese Unexamined Patent Publication No. 2009-226562.
  • Examples of the settings necessary for creating the processing program include setting of the shape of a workpiece (powder compact M in the present embodiment), setting of a tool to be used for processing, and tool path setting.
  • the computer apparatus 2 creates a molded article processing program including, for example, a numerical control (NC) program, based on the three-dimensional CAD data of the current product C and the setting information entered by a user.
  • the computer apparatus 2 transmits the processing program created by the CAD/CAM software to the molded article processing apparatus 32 used in step 3.
  • NC numerical control
  • a molding apparatus 31 manufactures the powder compact M having a simple shape such as a cylinder or a hollow cylinder
  • the processing apparatus 32 cuts the powder compact M to fabricate a processed molded article P having the same shape as the current product C.
  • the processing program created by the computer apparatus 2 includes a program that makes the processing apparatus 32 perform cutting on the powder compact M having a predetermined shape.
  • the three-dimensional CAD data of the powder compact M as the workpiece is registered in advance in the computer apparatus 2 .
  • the processing program preferably includes a code that commands the articulated robots 201 , 202 to use a different tool for each type of work.
  • the tool to be used when relatively fine cutting is required for the surface of the powder compact M, the tool to be used may be an end mill. When a groove portion, a window portion, or the like is cut in the powder compact M, the tool to be used may be a side cutter.
  • the tool to be used When cutting is performed to widen the middle of a groove portion formed in the powder compact M, the tool to be used may be a T-slot cutter. When a through hole is cut in the powder compact M, the tool to be used may be a drill.
  • the drill to be used for drilling is preferably a round tip drill having an arc-shaped cutting edge at the tip portion (see, e.g., Japanese Unexamined Patent Publication No. 2016-113657) or a candle-type drill (see, e.g., Japanese Unexamined Patent Publication No. 2016-113658).
  • a rotation speed of the tool used for cutting the powder compact M is preferably, for example, 500 to 50000 rpm.
  • the rotation speed is more preferably 1000 to 15000 rpm.
  • a feed speed of the tool used for cutting the powder compact M is preferably, for example, 20 to 6000 mm/min.
  • the feed speed is more preferably 200 to 2000 mm/min.
  • the cutting depth and cutting position of the powder compact M are calculated based on the three-dimensional CAD data of the powder compact M entered by the user in step 2 and the three-dimensional CAD data of the current product C acquired in step 1.
  • FIG. 3 is an overall configuration illustration showing an example of the manufacturing facility 3 used in step 3.
  • the manufacturing facility 3 is a facility in which apparatuses 31 to 35 that each individually execute steps P1 to P5 are installed in order.
  • the manufacturing facility 3 is installed in a factory of the manufacturer of the sintered product S.
  • the manufacturing facility 3 shown in FIG. 3 includes a production line including: the apparatuses 31 to 35 corresponding to the steps P1 to P5, respectively; a conveyor 36 passing through the vicinity of each of the apparatuses 31 to 35 ; and robot arms 37 that each carry a workpiece (powder compact M or the like) in and out for each of the apparatuses 31 to 35 .
  • a production line including: the apparatuses 31 to 35 corresponding to the steps P1 to P5, respectively; a conveyor 36 passing through the vicinity of each of the apparatuses 31 to 35 ; and robot arms 37 that each carry a workpiece (powder compact M or the like) in and out for each of the apparatuses 31 to 35 .
  • the robot arms 37 each carry the workpiece in from the conveyor 36 to each of the apparatuses 32 to 35 and carry the workpiece out from each off the apparatuses 31 to 35 to the conveyor 36 on a one-by-one basis.
  • Finishing processing is performed to bring the actual dimension of the sintered product S close to the design dimension.
  • steps P1 to P5 will be described.
  • Metal powder serving as a raw material in a molding step P1 is a main material constituting the sintered product S.
  • An example of the metal powder includes iron powder or iron alloy powder containing iron as a main component. Typical examples of the metal powder include pure iron powder and iron alloy powder.
  • the “iron alloy containing iron as a main component” means that an iron element is contained, as a constituent component, in an amount of more than 50 mass %, preferably 80 mass % or more, and further 90 mass % or more.
  • the iron alloy include those containing at least one alloying element selected from Cu, Ni, Sn, Cr, Mo, Mn, and C.
  • the alloying elements described above contribute to an improvement in the mechanical characteristics of an iron-based sintered product.
  • the total content of Cu, Ni, Sn, Cr, Mn, and Mo, among the alloying elements may be set to 0.5 mass % or more and 5.0 mass % or less, and further to 1.0 mass % or more and 3.0 mass % or less.
  • the content of C may be set to 0.2 mass % or more and 2.0 mass % or less, and further to 0.4 mass % or more and 1.0 mass or less.
  • iron powder may be used as the metal powder, and thereto powder of the above-described alloying element (alloyed powder) may be added.
  • the constituent component of the metal powder is iron in the stage of raw material powder, but the iron reacts with the alloying element to be alloyed by sintering in a sintering step P3.
  • the content of the metal powder (including alloyed powder) in the raw material powder may be set to, for example, 90 mass % or more, and further 95 mass % or more.
  • the metal powder those fabricated by, for example, a water atomization method, a gas atomization method, a carbonyl method, or a reduction method can be used.
  • the average particle size of the metal powder may be set to, for example, 20 ⁇ m or more and 200 ⁇ m or less, and further 50 ⁇ m or more and 150 ⁇ m or less.
  • the metal powder is easy to handle and easy to perform pressure molding on.
  • the average particle size of the metal powder is easy to handle and easy to perform pressure molding on.
  • the average particle size of the metal powder is easy to handle and easy to perform pressure molding on.
  • the average particle size of the metal powder to 20 ⁇ m or more, the fluidity of the raw material powder can be easily secured.
  • the sintered product S having a dense structure can be easily obtained.
  • the average particle size of the metal powder means an average particle size of particles constituting the metal powder.
  • the average particle size of the particles is, for example, a particle size (D50) at which a cumulative volume in a volume particle size distribution measured by a laser diffraction particle size distribution measuring device is 50%.
  • the raw material powder preferably contains Fe powder or Fe alloy powder, and C powder.
  • This raw material powder mainly contains Fe powder or Fe alloy powder.
  • Fe powder and Fe alloy powder may be collectively referred to as Fe-based powder.
  • the Fe powder is pure iron powder.
  • the Fe alloy powder contains iron as a main component, and has a plurality of Fe alloy particles containing one or more additive elements selected from, for example, Ni and Mo.
  • the Fe alloy is allowed to contain inevitable impurities.
  • the Fe alloy include Fe—Ni—Mo-based alloys.
  • the Fe-based powder for example, water atomized powder, gas atomized powder, carbonyl powder, or reduced powder can be used.
  • the content of the Fe-based powder in the raw material powder may be, for example, 90 mass % or more, and further 95 mass % or more, based on 100 mass % of the raw material powder.
  • the content of Fe in the Fe alloy may be 90 mass % or more, and further 95 mass % or more, based on 100 mass % of the Fe alloy.
  • the total content of the additive elements in the Fe alloy may be more than 0 mass % and 10.0 mass % or less, and further 0.1 mass % or more and 5.0 mass % or less.
  • the average particle size of the Fe-based powder may be, for example, 50 ⁇ m or more and 150 ⁇ m or less.
  • the Fe-based powder is easy to handle and easy to perform pressure molding on.
  • the average particle size of the Fe-based powder is easy to handle and easy to perform pressure molding on.
  • the average particle size of the Fe-based powder is 50 ⁇ m or more, fluidity can be easily secured.
  • the average particle size of the Fe-based powder By setting the average particle size of the Fe-based powder to 150 ⁇ m or less, the sintered product S having a dense structure can be easily obtained.
  • the average particle size of the Fe-based powder may be further 55 ⁇ m or more and 100 ⁇ m or less.
  • the “average particle size” means a particle size (D50) at which a cumulative volume in a volume particle size distribution measured by a laser diffraction particle size distribution measuring device is 50%. The same applies to the average particle sizes of the C powder and Cu powder described later.
  • the C powder becomes a liquid phase of Fe—C when the temperature is raised, which makes the corners of the pores in the sintered product S round to improve the strength (radial crushing strength) of the sintered product S.
  • the content of the C powder in the raw material powder may be 0.2 mass % or more and 1.2 mass % or less based on 100 mass % of the raw material powder.
  • the content of the C powder is further preferably 0.4 mass % or more and 1.0 mass % or less, and particularly preferably 0.6 mass % or more and 0.8 mass % or less.
  • the average particle size of the C powder is preferably smaller than the average particle size of the Fe powder. This makes it easy to uniformly disperse the C particles between the Fe particles, so that the alloying easily proceeds.
  • the average particle size of the C powder may be, for example, 1 ⁇ m or more and 30 ⁇ m or less, and further 10 ⁇ m or more and 25 ⁇ m or less. From the viewpoint of generating the liquid phase of Fe—C, it is preferable that the average particle size of the C powder is large, but if the average particle size is too large, the time when the liquid phase appears becomes so long that the pores become too large, which may cause a defect. Note that if the raw material powder contains the pure iron powder but does not contain C, the strength of the sintered product S is lower than that of the sintered product S fabricated using a belt type continuous sintering furnace.
  • the raw material powder preferably further contains Cu powder.
  • Cu powder contributes to generating the liquid phase of Fe—C when the temperature is raised in the sintering step described later. Moreover, Cu has a function of increasing the strength by forming a solid solution in Fe. By containing Cu powder, the sintered product S with high strength can be fabricated.
  • the content of the Cu powder in the raw material powder is 0.1 mass % or more and 3.0 mass % or less based on 100 mass % of the raw material powder.
  • the content of the Cu powder By setting the content of the Cu powder to 3.0 mass % or less, Cu diffuses into Fe while the temperature is raised (sintered), so that the Fe particles expand and act to offset the shrinkage during the sintering. Thereby, the sintered product S with high dimensional precision can be easily fabricated.
  • the content of the Cu powder may be further 1.5 mass % or more and 2.5 mass % or less.
  • the average particle size of the Cu powder is preferably made smaller than the average particle size of the Fe powder, similarly to the C powder. This makes it easy to uniformly disperse the Cu particles between the Fe particles, so that it is easy for the alloying to proceed.
  • the average particle size of the Cu powder may be, for example, 1 ⁇ m or more and 30 ⁇ m or less, and further 10 ⁇ m or more and 25 ⁇ m or less.
  • raw material powder obtained by mixing metal powder and an internal lubricant is commonly used to prevent seizure of the metal powder on the mold.
  • an internal lubricant is not contained in the raw material powder or contained in an amount of 0.2 mass % or less based on the whole raw material powder. This is because a decrease in the ratio of the metal powder to the raw material powder is suppressed to obtain the powder compact M having a relative density of 93% or more.
  • an internal lubricant in the raw material powder within a range where the powder compact having a relative density of 93% or more can be fabricated.
  • a metal soap such as lithium stearate or zinc stearate, can be used.
  • organic binder examples include polyethylene, polypropylene, polyolefin, polymethyl methacrylate, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyamide, polyester, polyether, polyvinyl alcohol, vinyl acetate, paraffin, and various waxes.
  • the organic binder may be added as necessary, or may not be added. When an organic binder is added, it is necessary to set the addition amount to such an extent that the powder compact M having a relative density of 93% or more can be fabricated in the molding step P1.
  • the raw material powder is uniaxially pressed using a mold to fabricate the powder compact M.
  • the mold to be used for the uniaxial pressing is a mold including a die and a pair of punches fitted into upper and lower openings of the die.
  • the powder compact M is fabricated by compressing, with the upper punch and the lower punch, the raw material powder filled in the cavity of the die.
  • the powder compact M that can be molded by the mold has a simple shape.
  • Examples of the simple shape include a cylindrical shape, a hollow cylindrical shape, a prismatic shape, and a hollow prismatic shape.
  • a punch having convex portions or concave portions on the punch surface may be used.
  • recesses or protrusions corresponding to the convex portions or the concave portions are formed in the powder compact M having a simple shape.
  • the powder compact having such recesses or protrusions is also included in the powder compact M having a simple shape.
  • the pressure (surface pressure) of the uniaxial pressing may be 600 MPa or more. By increasing the surface pressure, the relative density of the powder compact M can be increased.
  • the surface pressure is preferably 1000 MPa or more, and more preferably 1500 MPa or more.
  • the upper limit of the surface pressure is not particularly limited.
  • the uniaxial pressing it is preferable to apply an external lubricant to the inner peripheral surface of the mold (the inner peripheral surface of the die and the pressing surface of the punch) in order to prevent seizure of the metal powder on the mold.
  • a metal soap such as lithium stearate or zinc stearate
  • fatty acid amide such as lauric acid amide, stearic acid amide, or palmitic acid amide, or higher fatty acid amide, such as ethylene bis-stearic acid amide, can also be used as the external lubricant.
  • the average relative density of the whole powder compact M obtained by the uniaxial pressing is preferably 93% or more.
  • the average relative density is preferably 94% or more or 95% or more, more preferably 96% or more, still more preferably 97% or more, and yet still more preferably 99.8% or more.
  • the dense portion having an average relative density of 93% or more may be the whole or a part of the powder compact M.
  • the average relative density of the whole is preferably 93% or more. This is because, when the whole is dense, it is difficult to chip no matter which portion of the powder compact M is gripped.
  • the sintered product S whose whole has an average relative density of 93% or more can be obtained.
  • the average relative density of the whole sintered compact S is substantially equal to the average relative density of the whole powder compact M before sintering.
  • the average relative density of the sintered product S is preferably 95% or more, more preferably 96% or more, and still more preferably 97% or more. The higher the average relative density, the higher the strength of the sintered product S.
  • the average relative density of the whole powder compact M can be determined by taking cross sections (preferably orthogonal cross sections) of the powder compact M, respectively intersecting with the pressing axis direction at positions near the center, near one end side, and near the other end side in the pressing axis direction, and by performing image analysis on each cross section.
  • cross sections preferably orthogonal cross sections
  • the respective images of field of view are preferably acquired from positions distributed as evenly as possible in the cross section.
  • each of the acquired images of field of view is binarized to determine the area ratio of the metal particles to the field of view, and the area ratio is regarded as a relative density for the field of view.
  • the average relative densities determined from the respective fields of view are averaged to calculate the average relative density of the whole powder compact.
  • the portion near one end side may be a position, for example, within 3 mm from the surface of the powder compact M.
  • the powder compact M fabricated by the uniaxial pressing is machined without being sintered.
  • the machining is typically cutting.
  • the powder compact M is processed to have a predetermined shape using a cutting tool.
  • the cutting include rolling and turning, and the rolling includes drilling.
  • the cutting tool include a drill or a reamer to be used in drilling, a milling cutter or an end mill to be used in rolling, and a turning tool and an interchangeable cutting tip to be used in turning. Cutting may be performed using a hob, a broach, a pinion cutter, or the like, other than those described above.
  • machining is performed so that the metal particles are peeled off from the surface of the powder compact M by a cutting tool.
  • the friction on the cutting tool is much smaller than when, for example, a cast article or a pre-sintered article is cut, which can greatly shorten the life of the tool.
  • the processing waste generated by the machining is composed of metal powder separated from the individual metal particles constituting the powder compact M. The powdery processing waste can be reused without being dissolved.
  • the sintering temperature may be, for example, 1100° C. or higher and 1400° C. or lower, and further 1200° C. or higher and 1300° C. or lower.
  • the sintering time may be, for example, 15 minutes or longer and 150 minutes or shorter, and further 20 minutes or longer and 60 minutes or shorter.
  • the degree of processing in the processing step P2 may be adjusted based on the difference between the actual dimension and the design dimension of the sintered product S.
  • the degree of processing in the processing step P2 can be adjusted based on the difference between the actual dimension after sintering and the design dimension.
  • the efforts and time of the next finishing step P4 can be reduced.
  • the degree of processing can be easily adjusted.
  • the surface of the sintered product S is polished and the like to reduce the surface roughness of the sintered product S, and the dimension of the sintered product S is matched to the design dimension (dimension of the current product C).
  • the polishing finish is performed by a not-shown polishing apparatus.
  • the three-dimensional CAD data of the current product C, acquired in step 1 is input to the polishing apparatus.
  • the polishing apparatus calculates the design dimension of the sintered product S from the input data, and polishes each portion of the sintered product S so as to have the calculated design dimension. For example, when the sintered product S includes a gear, the tooth surface of the gear is polished.
  • an inspection step P5 at least one of whether the sintered product S conforms to the design dimension (dimension of the current product C) and whether there is no defect such as a crack is inspected.
  • These inspections are preferably performed by a non-contact type 3D scanner (e.g., 3D scanner of laser light type or of patterned light type) or a non-contact, non-destructive inspection apparatus.
  • a non-contact type 3D scanner e.g., 3D scanner of laser light type or of patterned light type
  • a non-contact, non-destructive inspection apparatus By using these inspection apparatuses, the sintered products S can be automatically inspected one by one.
  • FIG. 4 is a schematic configuration illustration showing an example of the molding apparatus 31 used in the molding step P1.
  • the molding apparatus 31 used in the molding step P1 includes, for example, a uniaxial pressing press molding apparatus driven by a hydraulic servo method.
  • the press molding apparatus 31 includes a base plate 101 having a rectangular shape, pillars 102 provided at four corners of the base plate 101 , a ceiling frame 103 fixed to upper ends of the pillars 102 , and an upper plate 104 vertically movably supported by the upper portions of the pillars 102 .
  • a punch set 106 whose vertical position is controlled by a hydraulic cylinder mechanism 105 is provided above the base plate 101
  • a punch set 108 whose vertical position is controlled by a hydraulic cylinder mechanism 107 is provided below the upper plate 104 .
  • a hydraulically-driven upper cylinder 109 is provided in a central portion of the ceiling frame 103 .
  • the lower end of the rod of the upper cylinder 109 and the upper surface of the upper plate 104 are connected via a link mechanism 110 .
  • the upper plate 104 descends to a position where raw material powder 116 is prepared. Thereafter, the punch set 106 and the punch set 108 are joined by driving the upper and lower hydraulic cylinder mechanisms 105 , 107 , so that the raw material powder 116 is pressed.
  • the upper and lower hydraulic cylinder mechanisms 105 , 107 have a structure in which a plurality of hydraulic cylinders are coaxially multilayered, and the axial center of each hydraulic cylinder is at the center position of the base plate 101 .
  • the press molding apparatus 31 has a slim structure without any member protruding outside the base plate 101 , and can be installed without a pit. Therefore, the press molding apparatus 31 has advantages that the installation area and the installation cost are small.
  • the lower punch set 106 includes a hollow cylindrical die 111 , a core rod 112 , an outer punch 113 , and an inner punch 114 .
  • a cavity is formed by the inner peripheral surface of the die 111 and the outer peripheral surface of the core rod 112 .
  • the upper punch set 108 includes an upper punch 115 .
  • the upper punch 115 has a hollow cylindrical shape having a passage hole for the core rod 112 .
  • the upper end surface of the core rod 112 is made to protrude from the upper end surface of the die 111 , and the outer punch 113 is set at a deeper position than the inner punch 114 .
  • the cavity is filled with the raw material powder 116 .
  • the upper punch 115 is lowered while the outer punch 113 and the lower punch 114 are being raised together.
  • the rising speed is controlled so that the outer punch 113 and the inner punch 114 simultaneously reach the top dead center at the same position.
  • the powder compact M having a uniform thickness is molded.
  • the powder compact M becomes a substantially donut-shaped tablet having a high-density region M 1 in the outer peripheral portion and a low-density region M 2 in the inner peripheral portion.
  • the molding method described above is suitable for manufacturing the sintered product S having a sliding portion continuous along the outer peripheral edge, such as an external teeth gear or a sprocket.
  • an external teeth gear external teeth having high rigidity and excellent wear resistance can be obtained by defining the outer peripheral side of the powder compact M as the high-density region M 1 .
  • the powder compact M is obtained in which the inner peripheral portion is the high-density region M 1 and the outer peripheral portion is the low-density region M 2 .
  • the molding method described above is suitable for manufacturing the sintered product S having a sliding portion continuous along the inner peripheral edge, like an internal teeth gear.
  • internal teeth having high rigidity and excellent wear resistance can be obtained by defining the inner peripheral side of the powder compact M as the high-density region M 1 .
  • the relative density of the high-density region M 1 may be set to 93% or more, and the relative density of the low-density region M 2 may be less than 93%.
  • the powder compact M whose whole has an average relative density of 93% or more can also be molded using the press molding apparatus 31 .
  • FIG. 5 is a schematic configuration illustration showing an example of the processing apparatus 32 used in the processing step P2.
  • the processing apparatus 32 used in the processing step P2 includes, for example, a robot processing apparatus configured to process the powder compact M using the articulated robots 201 , 202 .
  • Such a robot processing apparatus 32 needs an installation space smaller than, for example, a five-axis machining center, it contributes to making the manufacturing facility 3 of the sintered product S compact.
  • the robot processing apparatus 32 includes two articulated robots 201 , 202 and a controller 203 configured to control operation of both the articulated robots 201 , 202 .
  • a first robot 201 of one side is a robot configured to hold a tool 204 such as a drill.
  • a second robot 202 of the other side is a robot configured to hold the powder compact M.
  • the first robot 201 has a grip unit 205 for the tool 204 at the arm tip. In accordance with a command from the controller 203 , the first robot 201 can grip different types of tools 204 with the grip unit 205 .
  • the second robot 202 has a grip unit 206 for the powder compact M at the arm tip.
  • the second robot 202 can grip the powder compact M being conveyed on the conveyor 36 with the grip unit 206 .
  • the second robot 202 can also return the processed molded article P to the conveyor 36 .
  • the controller 203 includes a first communication unit 207 , a second communication unit 208 , a control unit 209 , and a storage unit 210 .
  • the first communication unit 207 includes a communication interface configured to communicate with an external device according to a predetermined communication standard such as Ethernet (registered trademark).
  • the second communication unit 208 includes a communication interface communicably connected to the first and second arms 201 , 202 .
  • the control unit 209 includes an information processor including a CPU, a volatile memory, and the like.
  • the storage unit 210 includes a storage device including a recording medium such as a hard disk drive (HDD) or a solid state drive (SSD).
  • HDD hard disk drive
  • SSD solid state drive
  • the first communication unit 207 When receiving the processing program from the computer apparatus 2 of step 2, the first communication unit 207 provides the received program to the control unit 209 .
  • the control unit 209 extracts an operation code (e.g., a G code or an M code) from the received processing program.
  • the control unit 209 sequentially outputs the respective operation codes extracted to the second communication unit 208 to make the second communication unit 208 transmit the operation codes to the articulated robots 201 , 202 .
  • the articulated robots 201 , 202 execute predetermined work in accordance with the received operation codes.
  • the articulated robots 201 , 202 perform predetermined processing on the powder compact M in accordance with a command from the controller 203 .
  • the first and second robots 201 , 202 each have an arm structure with at least six degrees of freedom.
  • the second robot 202 having a degree of freedom of less than 6 may be adopted when the position and posture of the powder compact M are not required to be adjusted with a high degree of freedom, such as being held at the same position while being processed.
  • the relative density of the powder compact M is 93% or more, so that the powder compact M is not broken even when cutting is performed on the powder compact M held by the second robot 202 with the tool 204 of the first robot 201 . Therefore, the powder compact M can be quickly processed.
  • At least the first robot 201 has six degrees of freedom, so that the tool 204 can be brought into contact with the powder compact M at an arbitrary angle, by which complicated processing can be quickly executed.
  • FIG. 6 is a schematic configuration illustration showing an example of a sintering apparatus 33 used in the sintering step P3.
  • the sintering apparatus 33 used in the sintering step P3 includes, for example, an induction heating sintering furnace configured to heat the processed powder compact M (processed molded article P) by a high frequency induction method.
  • the processed molded article P can be heated to a predetermined temperature in a short time. Therefore, the sintered product S can be easily manufactured in a short time.
  • the induction heating sintering furnace 33 includes a chamber 301 that is vertically long, a hollow cylindrical heating container 302 housed in the chamber 301 , a cooling container 303 arranged below the heating container 302 , and a lifting table 304 arranged below the heating container 302 .
  • An induction coil 305 is wound around the outer peripheral surface of the heating container 302 , and the inside of the heating container 302 and the inside of the cooling container 303 communicate with each other in the vertical direction.
  • the lifting table 304 can lift or lower the processed molded article P to the height of either the inside of the heating container 302 or the inside of the cooling container 303 .
  • the induction heating sintering furnace 33 also includes a power supply (not shown) capable of adjusting an output value (e.g., a power value) and a frequency for the induction coil 305 .
  • a power supply (not shown) capable of adjusting an output value (e.g., a power value) and a frequency for the induction coil 305 .
  • the processed molded article P is placed on the lifting table 304 by the robot arm 37 .
  • the lifting table 304 positions the processed molded article P inside the heating container 302 .
  • the lifting table 304 positions the processed molded article P after sintering inside the cooling container 303 .
  • the induction heating sintering furnace 33 preferably includes a gas supply path for supplying an inert gas into the heating container 302 and a gas discharge path for discharging a gas to the outside of the heating container 302 .
  • the processed molded article P can be sintered under a non-oxidizing gas atmosphere.
  • the inert gas include nitrogen gas and argon gas.
  • the induction heating sintering furnace 33 can raise the temperature of an object at a high rate, and can raise the temperature of the processed molded article P to a predetermined temperature in a short time.
  • the sintered product S can be manufactured in a shorter time than, for example, a belt type continuous sintering furnace.
  • the induction heating sintering furnace 33 has a high heating rate, there is also an advantage that a smaller installation space is sufficient than, for example, a belt type continuous sintering furnace.
  • a relatively small chamber 301 e.g., 1.5 m ⁇ 1.5 m
  • the induction heating sintering furnace 33 takes a short time to sinter the processed molded article P, and it is not necessary to keep the temperature of the sintering furnace 33 while the processed molded article P is not sintered. Thus, there is also an advantage that more energy can be saved than, for example, a belt type continuous sintering furnace.
  • a heating process, a sintering process, and a cooling process are passed in sequence.
  • a temperature course preferable when the induction heating sintering furnace 33 is used will be described.
  • the temperature of the processed molded article P is controlled to satisfy all of the following conditions (I) to (III).
  • a point A 1 is about 738° C.
  • a point A 3 is about 910° C.
  • the temperature is raised without being kept in a temperature range from the point A 1 or higher to lower than the sintering temperature of the processed molded article P in an Fe—C system phase diagram.
  • the heating rate in the temperature range from the point A 1 to the point A 3 in the Fe—C system phase diagram is set to 12° C./sec or more.
  • the heating rate from the point A 3 to the sintering temperature of the processed molded article P in the Fe—C system phase diagram is set to 4° C./sec or more.
  • An atmospheric temperature is raised without being kept in an atmospheric temperature range corresponding to from the point A 1 or higher to lower than the sintering temperature of the processed molded article P in the Fe—C system phase diagram.
  • the heating rate in an atmospheric temperature range corresponding to from the point A 1 to the point A 3 in the Fe—C system phase diagram is set to 12° C./sec or more.
  • the heating rate in an atmospheric temperature range corresponding to from the point A 3 to the sintering temperature of the processed molded article P in the Fe—C system phase diagram is set to 4° C./sec or more.
  • the atmospheric temperature is an atmospheric temperature in the heating container 302 , and is a temperature measured with a thermocouple (diameter y 3.5 mm) arranged within 8.5 mm from the processed molded article P.
  • the atmospheric temperature in the heating container 302 is heated by the heat of the processed molded article P that has been induction-heated, the atmospheric temperature is often slightly lower than the temperature of the processed molded article P itself that has been induction-heated.
  • the atmospheric temperature corresponding to the point A 1 is the temperature of the atmosphere when the temperature of the processed molded article P reaches the point A 1 , and is often a temperature lower than or equal to the point A 1 .
  • the sintered product S with high strength can be manufactured.
  • the reason is considered as follows:
  • C particles adjacent to Fe particles remain as a solid phase, and adjacent interfaces between the Fe particles and the C particles, and the like become a C-rich phase (sometimes only C is present).
  • the heating rate can be adjusted by adjusting the output or frequency of the power supply of the induction heating sintering furnace 33 .
  • Examples of the setting of the output or the frequency include setting of the output or the frequency satisfying the heating rate of the condition (II).
  • the setting of the output or the frequency may be made constant from the temperature range of the condition (II) to the temperature range of the condition (III), or may be changed when the temperature range of the condition (II) is shifted to the temperature range of the condition (III).
  • the heating rate of the condition (III) is smaller than the heating rate of the condition (II).
  • the heating rate of the condition (III) can be further increased, and eventually the heating rate can be made approximately equal to the heating rate of the condition (II).
  • the heating rate of the condition (II) is preferably as high as possible, and more preferably, for example, 12.5° C./sec or more.
  • the upper limit of the heating rate of the condition (II) may be, for example, 50° C./sec or less, and more preferably 15° C./sec or less.
  • the heating rate of the condition (III) is preferably as high as possible, similarly to the condition (II). It is preferably, for example, 5° C./sec or more, and more preferably 10° C./sec or more.
  • the upper limit of the heating rate of the condition (III) may be, for example, 50° C./sec or less, and more preferably 15° C./sec or less.
  • the temperature of the processed molded article P is further preferably controlled to satisfy either a condition (IV) or a condition (V).
  • a temperature is not kept in a temperature range where the temperature of the processed molded article P is 410° C. or higher and lower than the point A 1 in the Fe—C system phase diagram, and the heating rate in this temperature range is set to 12° C./sec or more.
  • the sintered product S with high strength can be manufactured in a shorter time than when the conditions (V) and (v) are satisfied.
  • the heating rate of the conditions (IV) and (iv) can be achieved by, for example, setting the output or the frequency to be the same as the output or the frequency that satisfies the heating rate of the conditions (II) and (ii).
  • the setting of the output or frequency of the power supply of the induction heating sintering furnace 33 is always made constant from the start of the heating to the time of sintering, and an atmospheric temperature from the atmospheric temperature at the start of the heating to the atmospheric temperature during the sintering is not kept. Since an atmospheric temperature lower than the atmospheric temperature during the sintering is not kept, the sintered product S can be manufactured in a short time.
  • the heating rate at the atmospheric temperature of the conditions (IV) and (iv) is further preferably 15° C./sec or more, and particularly preferably 20° C./sec or more.
  • the processed molded article P can be heated more uniformly than when the conditions (IV) and (iv) are satisfied. That is, the conditions (V) and (v) are particularly suitable when the processed molded article P having a complicated shape is sintered.
  • the temperature range of the condition (V) is further preferably 735° C. or lower, and particularly preferably 700° C. or lower.
  • the atmospheric temperature of the condition (v) is further preferably 600° C. or lower, and particularly preferably 500° C. or lower.
  • the keeping time for keeping the atmospheric temperature of the conditions (V) and (v) is further preferably 45 seconds or longer and 75 seconds or shorter.
  • the heating rates, after the temperature of the condition (V) or the atmospheric temperature of the condition (v) is kept, are set to the heating rates of the conditions (II), the conditions (ii) and (III), and the condition (iii).
  • the holding time of the processed molded article P at the atmospheric temperature during the sintering depends on the atmospheric temperature (sintering temperature) and the size of the molded article, but it is preferably, for example, 30 seconds or longer and 90 seconds or shorter.
  • the holding time When the holding time is set to 30 seconds or longer, the processed molded article P can be sufficiently heated, so that the sintered product S with high strength can be easily manufactured.
  • the holding time When the holding time is set to 90 seconds or shorter, the holding time is short, so that the sintered product S can be manufactured in a short time.
  • the holding time is further preferably 90 seconds or shorter, and particularly preferably 60 seconds or shorter. Note that in the case of the processed molded article P having a large size, or the like, it may be effective to set the holding time to 90 seconds or longer.
  • the sintering temperature of the processed molded article P may be higher than or equal to a temperature at which the liquid phase of Fe—C is generated, and may be 1153° C. or higher.
  • the sintering temperature is set to 1153° C. or higher, the liquid phase is generated and the corners of the pores can be easily rounded, so that the sintered product S with high strength can be easily manufactured.
  • the sintering temperature is preferably, for example, 1250° C. or lower. In this case, the temperature is not too high and the liquid phase can be suppressed form being excessively generated, so that the sintered product S with high dimensional precision can be easily manufactured.
  • the sintering temperature is further preferably 1153° C. or higher and 1200° C. or lower, and particularly preferably 1155° C. or higher and 1185° C. or lower.
  • the atmospheric temperature during the sintering of the processed molded article P is preferably 1135° C. or higher and lower than 1250° C.
  • the sintering temperature of the processed molded article P satisfies 1153° C. or higher
  • the atmospheric temperature during the sintering of the processed molded article P satisfies 1135° C. or higher.
  • the atmospheric temperature during the sintering of the processed molded article P satisfies lower than 1250° C.
  • the atmospheric temperature during the sintering is further preferably 1135° C. or higher and 1185° C. or lower, and particularly preferably 1135° C. or higher and lower than 1185° C.
  • a cooling rate in the cooling process of the sintering step P3 is preferably increased.
  • a bainite structure is easily formed, and furthermore a martensite structure is easily formed, so that the strength of the sintered product S is easily increased.
  • the cooling rate is preferably 1° C./sec or more. As a result, the processed molded article P can be quickly cooled.
  • the cooling rate is further preferably 2° C./sec or more, and particularly preferably 5° C./sec or more.
  • the cooling rate may be, for example, 200° C./sec or less, further 100° C./sec or less, and particularly 50° C./sec or less.
  • a temperature range where the processed molded article P is cooled at this cooling rate may be set to a temperature range from the start of the cooling (the sintering temperature of the processed molded article P) to the completion of the cooling (e.g., about 200° C.).
  • the temperature range is particularly preferably set to a temperature range (atmospheric temperature range) from the temperature of the processed molded article P (atmospheric temperature) of 750° C. (700° C.) to 230° C. (200° C.).
  • Examples of the cooling method include spraying a cooling gas onto the sintered product S.
  • Examples of the type of the cooling gas include inert gases such as nitrogen gas and argon gas. Due to the rapid cooling, the subsequent heat treatment step can be omitted.
  • FIG. 7 is a schematic configuration illustration showing an example of an inspection apparatus 35 used in the inspection step P5.
  • the inspection apparatus 35 used in the inspection step P5 includes first and second sensor apparatuses 501 , 502 and a computer apparatus 503 communicably connected to each of the sensor apparatuses 501 , 502 .
  • the computer apparatus 503 includes, for example, a desktop personal computer (PC).
  • the type of the computer apparatus 503 is not particularly limited.
  • the type of the computer apparatus 503 may be, for example, a notebook type or a tablet type.
  • the computer apparatus 503 includes: an information processor including a CPU and a volatile memory; a storage device including a nonvolatile memory configured to store a computer program to be executed by the CPU and data necessary for the execution; and the like.
  • the computer apparatus 2 also includes an input device and a display.
  • the CPU reads the computer program into the volatile memory to execute the computer program, whereby the computer apparatus 503 functions as a predetermined controller.
  • the first sensor apparatus 501 includes, for example, a non-contact type 3D scanner.
  • the 3D scanner may be the afore-mentioned patterned light 3D scanner 1 (see FIG. 2 ), or may be a laser light 3D scanner.
  • the first sensor apparatus 501 scans the sintered products S subjected to the finishing step P4 one by one to generate three-dimensional CAD data, and transmits the generated data to the computer apparatus 503 .
  • the second sensor apparatus 502 includes, for example, a digital camera capable of acquiring a digital image.
  • the second sensor apparatus 502 photographs the sintered products S subjected to the finishing step P4 one by one to generate image data, and transmits the generated image data to the computer apparatus 503 .
  • the computer apparatus 503 stores three-dimensional CAD data of the current product C.
  • This data is, for example, the data received from the computer apparatus 2 of step 2, or the data stored in the computer apparatus 503 via a recording medium such as a USB memory.
  • the computer apparatus 503 calculates a dimensional error between the sintered product S and the current product C, based on the three-dimensional CAD data of the sintered product S and the three-dimensional CAD data of the current product C. Based on the calculated dimensional error, the computer apparatus 503 determines whether the sintered product S passes or fails. Specifically, the sintered product S having a dimensional error of a predetermined value or less is determined to be acceptable, and the sintered product S having a dimensional error exceeding the predetermined value is determined to be unacceptable (defective).
  • the computer apparatus 503 transmits the three-dimensional CAD data of the sintered product S determined to be acceptable to the computer apparatus 4 used in step 4.
  • the computer apparatus 503 determines the presence or absence of a crack or a scratch on the surface based on the image data acquired from the second sensor apparatus 502 , and determines the sintered product S having a crack or a scratch to be unacceptable (defective).
  • the sintered product S having a crack or a scratch is excluded as a defective product.
  • the determination processing can be performed, for example, by determining whether or not a partial image obtained by dividing the image data into a grid pattern includes something that is included in the target events, such as a scratch, that are included in the classification models obtained by machine learning (see Japanese Unexamined Patent Publication No. 2018-81629).
  • the powder compact M having a simple shape and a high density is fabricated by uniaxial pressing, the powder compact M is processed by the robot processing apparatus 32 having a high degree of freedom in processing to fabricate the processed molded article P, and the processed molded article P is sintered to manufacture the sintered product S.
  • the sintered product S with high precision can be manufactured without using a mold having a complicated shape that takes several months to manufacture.
  • the delivery date of the sintered product S can be shortened.
  • the induction heating sintering furnace 33 capable of manufacturing the sintered product S in a shorter time than a belt type continuous sintering furnace, is adopted, so that the delivery date of the sintered product S can be shortened also in this respect.
  • the robot processing apparatus 32 needing an installation space smaller than a five-axis machining center, and the induction heating sintering furnace 33 , needing an installation space smaller than a belt type continuous sintering furnace, are adopted, so that there is also an advantage that the manufacturing facility 3 can be made compact.
  • FIG. 8 is an explanatory illustration showing an example of an apparatus used in step 4.
  • the apparatus used in step 4 includes the computer apparatus 4 .
  • the computer apparatus 2 includes, for example, a desktop personal computer (PC).
  • the type of the computer apparatus 2 is not particularly limited.
  • the type of the computer apparatus 2 may be, for example, a notebook type or a tablet type.
  • the computer apparatus 4 includes: an information processor including a CPU and a volatile memory; a storage device including a nonvolatile memory configured to store a computer program to be executed by the CPU and data necessary for the execution; and the like.
  • the computer apparatus 2 also includes an input device and a display.
  • the CPU reads the computer program into the volatile memory to execute the computer program, whereby the computer apparatus 4 functions as a predetermined controller.
  • the CAD/CAT software is installed in the computer apparatus 4 .
  • the CAD/CAT software is software that realizes comparison processing between the three-dimensional CAD data of a determination target (here, the sintered product S that has passed the inspection in the inspection step P5) and the design data (three-dimensional CAD data of the current product C) serving as a reference of the shape of the sintered product S, in accordance with a user's operation input to the GUI of the computer apparatus 4 .
  • the computer apparatus 4 receives the three-dimensional CAD data of a plurality of the sintered products S from the computer apparatus 503 of the inspection step P5.
  • the computer apparatus 4 stores the three-dimensional CAD data of the current product C.
  • This data is, for example, the data received from the computer apparatus 2 of step 2, the data received from the computer apparatus 503 of the inspection step P5, or the data stored in the computer apparatus 4 via a recording medium such as a USB memory.
  • the computer apparatus 4 determines whether or not a statistically dominant number of excessively cut or insufficiently cut portions have been detected.
  • the computer apparatus 4 When detecting the excessively cut or insufficiently cut portions, the computer apparatus 4 generates a corrected program (e.g., an NC program) of the processing program.
  • the corrected program includes, for example, an operation code for increasing the cutting depth of an excessively cut portion or an operation code for increasing the cutting depth of an insufficiently cut portion.
  • the computer apparatus 4 transmits the generated corrected program to the processing apparatus 32 used in the processing step P2 of step 3.
  • the molded article processing apparatus 32 that has received the corrected program processes the powder compact M at the corrected cutting depth.
  • the computer apparatus 4 may transmit the corrected program to the computer apparatus 2 of step 2 (see FIG. 2 ).
  • the computer apparatus 2 of step 2 may forward the received corrected program to the processing apparatus 32 .
  • the molding apparatus 31 used in the molding step P1 of step 3 may be a press molding apparatus configured to mold the powder compact M whose whole has an average relative density of less than 93%.
  • the processing apparatus 32 used in the processing step P2 of step 3 may be a robot processing apparatus including only the first robot 201 .
  • the first robot 201 performs predetermined processing on the powder compact M set on a fixing table.
  • the processing apparatus 32 used in the processing step P2 of step 3 may be a robot processing apparatus including a plurality of at least one of the first and second robots 201 , 202 . That is, the number of the first and second robots 201 , 202 may be plural.
  • the processing apparatus 32 used in the processing step P2 of step 3 may be a processing apparatus adopting a five-axis machining center instead of the articulated robots 201 , 202 .
  • the sintering apparatus 33 used in the sintering step P3 of step 3 may be a belt type continuous sintering furnace instead of the induction heating sintering furnace.
  • the inspection step P5 of step 3 is not limited to a case where the inspection is performed fully automatically using the inspection apparatus 35 , and the inspection work may be performed wholly or partially by a human.
  • the inspection step P5 of step 3 may include correction of the processing program in step 4. That is, the arithmetic processing and the communication processing to be executed by the computer apparatus 4 of step 4 may be executed by the computer apparatus 503 of the inspection step P5. In this case, the computer apparatus 4 of step 4 is unnecessary.
  • FIG. 9 is a schematic configuration illustration showing an example of a movable manufacturing system.
  • a manufacturing system includes a mobile apparatus 601 capable of traveling on a road, and predetermined storage elements to be stored in a storage 602 of the mobile apparatus 601 .
  • the predetermined storage elements mean constituent elements necessary for manufacturing the sintered product S.
  • the mobile apparatus 601 includes, for example, a large truck, and the storage 602 includes a container fixed to the cargo bed of the large truck.
  • the predetermined storage elements include the 3D scanner 1 used in step 1, the computer apparatus 2 used in step 2, the robot processing apparatus 32 used in the processing step P2 of step 3, and the induction heating sintering furnace 33 used in the sintering step P3 of step 3.
  • the predetermined storage elements are placed in the storage 602 of the mobile apparatus 601 , so that the sintered product S can be manufactured by the following procedures.
  • the sintered product S (sample) following the current product C can be provided to the customer in a short time (e.g., several hours).
  • Procedure 1 Drive the mobile apparatus 601 to a point near the location of the customer in order to transport the predetermined storage elements placed in the storage 602 to the nearby point.
  • Procedure 2 Receive the current product C that is lent from the customers.
  • Procedure 3 Execute steps 1 to 3 to manufacture the sintered product S following the current product C on site.
  • Procedure 4 Provide the manufactured sintered product S (sample) to the customer.
  • the powder compact M to be processed by the robot processing apparatus 32 may be fabricated in advance in the manufacturer's own factory and loaded on the mobile apparatus 601 .
  • the 3D scanner 1 may be excluded from the predetermined storage elements.
  • the 3D data generated by the 3D scanner 1 outside the vehicle may be transmitted to the computer apparatus 2 inside the vehicle.
  • the 3D data of the current product C, acquired from the customer or the like, may be transmitted to the computer apparatus 2 inside the vehicle.
  • the computer apparatus 2 may be excluded from the predetermined storage elements.
  • the computer apparatus 2 outside the vehicle may generate the molded article processing program from the 3D data of the current product C, and transmit the generated program to the robot processing apparatus 32 inside the vehicle.
  • the molding apparatus 31 used in the molding step P1 of step 3 may be included in the predetermined storage elements.
  • the powder compact M can also be molded on site.
  • the apparatus used in the finishing step P4 of step 3 may be included in the predetermined storage elements.
  • the sintered product S can also be finished on site.
  • the inspection apparatus 35 used in the inspection step P5 of step 3 may be included in the predetermined storage elements. In this case, inspections, such as determination on whether the sintered product S passes or fails, can also be performed on site.
  • the apparatus used in step 4 may be included in the predetermined storage elements.
  • the correction of the processing program in step 4 can also be performed on site.
  • the target product serving as a reference of the shape of the sintered product S is not limited to the existing current product C, and may be an article under planning that has not yet been commercialized.

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