JP2014214373A - Method of producing large metal powder injection molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an injection molding method which can produce a high-accuracy large metal powder molding with high productivity without surface defects, e.g. wrinkles or welds.SOLUTION: A method of producing a large metal powder injection molding comprises mixing and kneading a raw material powder consisting of a metal powder or an alloy powder with a binder prepared by blending a wax ingredient and/or a lubricity imparting ingredient, a plastic ingredient and a plant oil in a blend ratio within an appropriate range to obtain a compound, using a die which allows heating or cooling of the cavity surface, heating, with a heating medium, the cavity surface of the die to a temperature equal to or higher than the load deflection temperature and equal to or lower than the thermal decomposition temperature of the plastic ingredient of the binder blended with the compound, injecting the plasticized compound into the cavity to form a molding, cooling the cavity surface to a temperature lower than the load deflection temperature of the plastic ingredient of the binder by using a cooling medium to solidify the compound and taking out the molding.

Description

  TECHNICAL FIELD The present invention relates to a method for producing a metal powder injection molded body by a metal powder injection molding method, and in particular, a method for producing a metal powder injection molded body capable of producing a large part with a weight of 100 g or more stably and with high productivity. About.

  Conventionally, powder injection molding has advantages such as excellent dimensional accuracy of products, stable stability of near net shape, and high productivity, especially in automobiles, precision machinery, etc. In the field, metal powder injection molding is used as a method for manufacturing parts. In the metal powder injection molding method, powders of metals, alloys, etc. are used as raw materials, organic binders are blended, mixed and kneaded to form a mixed kneaded product (compound), and then this mixed kneaded product (compound) is injection molded. Thus, a molded body having a desired shape is obtained, and an organic binder is extracted from the obtained molded body and then sintered to obtain a sintered body having a predetermined shape. However, when manufacturing large parts using the metal powder injection molding method, molding defects such as unfilled and internal defects are likely to occur. In particular, large parts with thin parts are usually unable to be filled. there were. In addition, even if it can be filled, surface defects such as wrinkles and welds are likely to occur on the surface of the molded body, resulting in problems such as extremely low productivity. Therefore, the metal powder injection molding method tends to be limited to application to small parts.

  For such a problem, for example, in Patent Document 1, a coupling agent is added to and mixed with one or a mixture of two or more of sintered body raw materials, and the whole is further mixed to form a slurry compound. The resulting slurry compound is poured into a cooled mold to form a frozen molded body, the frozen molded body is heated at vacuum, reduced pressure or normal pressure, the organic solvent is sublimated, and the molded body is baked. In conclusion, a method for obtaining a highly accurate inorganic sintered body is described. According to the technique described in Patent Document 1, the use of a coupling agent as a sintering raw material can increase the powder filling amount of the compact and can produce a large inorganic sintered compact with high accuracy.

  In Patent Document 2, one or more of a coupling agent, water and an additive are added to and mixed with inorganic powder to form a slurry compound, and the slurry compound is injected into a cooled mold. A frozen molded body is formed, and the frozen molded body is heated at a vacuum, reduced pressure or normal pressure to sublimate low-boiling components, and then the molded body is sintered to obtain a highly accurate inorganic sintered body. A method of manufacturing is described. According to the technique described in Patent Document 2, the use of a coupling agent in the inorganic powder can increase the powder filling amount of the molded body and can produce a large-sized inorganic sintered body with high accuracy.

Japanese Patent Laid-Open No. 10-53466 Japanese Patent Laid-Open No. 10-67006

  However, in the technique described in Patent Document 1, it is necessary to cool the mold to a low temperature and freeze the slurry compound, and after further freezing, the temperature is raised to sublimate the organic solvent. For this reason, a mold that can be frozen, a cooling device and a heating device for freezing are required, resulting in complicated manufacturing equipment, which causes a rise in manufacturing cost. Furthermore, in the technique described in Patent Document 2, since an aqueous solution is used for the compound, there is a problem that inorganic powder such as metal powder is oxidized, and it becomes difficult to secure a predetermined sintered body strength.

  The present invention solves such problems of the prior art, does not use an aqueous solution as a binder, and does not require a mold that can be frozen or a cooling device for freezing, so that surface defects such as wrinkles and welds can be obtained. It is an object of the present invention to provide a method for producing a large metal powder injection molded body, which can produce a high precision large metal powder injection molded body with high productivity. The term “large” as used herein refers to the case where the product weight is 100 g or more and 1000 g or less.

In order to achieve the above-mentioned object, the present inventors have surface defects such as wrinkles and welds, which are defects specific to a large metal powder injection molded body, particularly insufficient filling of materials in a large product with a small thickness, We have intensively studied various factors affecting the occurrence of internal defects.
In a normal metal powder injection molding method, a plasticized compound in an injection molding machine is injected into a mold in which cooling water is circulated and kept at a low temperature, and solidified to obtain a molded body having a desired shape. Yes. Therefore, a compound containing a metal powder having a high thermal conductivity is easily cooled when injected into a mold. In addition, when the product is enlarged, the time required for injection is increased, the flow of the compound in the mold is stopped, the metal powder is insufficiently filled in the entire mold, and the product is poorly filled. Moreover, in a large-sized thick product, since the internal defect which arises during the flow of a compound cannot be crushed with the pressure which fills a compound, it becomes a molded object in which many internal defects exist.

  Therefore, the present inventors rapidly raise the mold temperature to a temperature at which the fluidity of the compound becomes high at the time of injection, and further to a low temperature at which the molded body is cooled and solidified after injection. It is considered that the above-mentioned defects can be avoided even in a large metal injection molded body by rapidly cooling the mold, and the heating medium and cooling are positioned close to the mold cavity surface during injection molding. It has been conceived to apply a heat cycle method for applying a heat cycle using a mold provided with channels that are alternately heated and cooled by a medium.

  Furthermore, in order to produce a large-sized metal powder injection molded body with high accuracy, the present inventors blended a binder used with a wax component and / or a lubricity-imparting component, a plastics component, and a vegetable oil. The plastic component to be blended is one or more of polypropylene resin, polyacetal resin and polyethylene resin, and the vegetable oil to be blended is added to castor oil, and one or two of peanut oil, olive oil and salad oil We found that it should be more than seeds.

The present invention has been completed based on such findings and further studies. That is, the gist of the present invention is as follows.
(1) A metal powder or an alloy powder is used as a raw material powder, a binder is blended into the raw material powder, kneaded and pulverized to form a compound, and the compound is inserted into a metal powder injection molding apparatus and injection molded into a mold. In the method of manufacturing a metal powder injection molded body, which is a molded body having a shape, a mold that can heat or cool the cavity surface of the mold with a heating medium or a cooling medium is used at the time of the injection molding. The cavity surface is heated to a heating temperature that is higher than the deflection temperature under load and lower than the thermal decomposition temperature of the plastics component of the binder blended in the compound using steam as a heating medium, and then into the heated cavity. A predetermined amount of the plasticized compound is injected, the cavity is filled, and after the filling is completed, the mold cavity table is filled. Applying a heat cycle method that comprises cooling the load to below the deflection temperature under load of the plastics component of the binder using water as a cooling medium, solidifying the compound, and taking out the molded body. A method for producing a large metal powder injection molded body, characterized in that it is a large metal powder injection molded body weighing 100 g or more.
(2) In (1), the binder and / or lubricity-imparting component is added in an amount of 30 to 45 with respect to 100% by volume of the total amount of the wax component and / or lubricity-imparting component, plastics component and vegetable oil. A method for producing a large metal powder injection-molded article, comprising: volume%, 30 to 45 volume% of the plastics component, and 5 to 40 volume% of the vegetable oil.
(3) The method for producing a large metal powder injection molded body according to (2), wherein the plastic component of the binder is one of polypropylene resin, polyacetal resin, and polyethylene resin.
(4) The large metal powder injection according to (2) or (3), wherein the vegetable oil of the binder is added to castor oil to be one or more of peanut oil, olive oil, and salad oil Manufacturing method of a molded object.
(5) A large metal powder injection molded product produced by the method for producing a large metal powder injection molded product according to any one of (1) to (4).

  According to the present invention, there is no defect such as surface defects such as wrinkles and welds and insufficient filling due to the stoppage of the flow of the compound in the mold, and a high-precision large-sized metal powder injection molded body has high productivity. It can be manufactured and has a remarkable industrial effect.

It is the schematic which shows typically an example of a structure of the metal powder injection molding apparatus used by this invention. It is explanatory drawing which shows the flow (flow) in the manufacturing method of this invention metal powder injection molding. It is explanatory drawing which shows an example of the process of the metal powder injection molding method.

The present invention is a method for producing a large metal powder injection molded body. The metal powder injection molded article targeted by the present invention is a large metal powder injection molded article having a weight of 100 g or more and 1000 g or less.
An example of the manufacturing process of the metal powder injection molded body is shown in FIG.
In the present invention, first, raw material powder is prepared. The raw material powder is a metal powder or an alloy powder. Depending on the application, examples of the metal powder include pure metal powders such as pure iron powder, pure titanium powder, and pure Ni, and examples of the alloy powder include powders of stainless steel, heat-resistant steel, tool steel, superalloy, and the like. The raw material powder is preferably a water atomized powder having an average particle size of 15 μm or less from the viewpoint of fluidity and sintered density. In addition, the value measured using the microtrack method shall be used for the average particle diameter of powder.

A desired amount of raw material powder is blended with a binder, preferably kneaded while heating at an appropriate temperature and an appropriate pressure, cooled and solidified, and then pulverized to obtain a kneaded product (compound).
In addition, the compounding quantity of a binder is a volume ratio with respect to the total amount of raw material powder and a binder, and it is preferable to set it as 30 to 60%. If the blending amount of the binder is less than 30%, the thermal conductivity is too low to make the molding difficult. On the other hand, if it exceeds 60%, the amount of deformation after sintering becomes large. For this reason, the binder to be blended is 30% to 60% by volume% based on the total amount of the raw material powder and the binder.

The binder used in the present invention is 30 to 45 volume of the wax component and / or lubricity imparting component with respect to 100% by volume of the total amount of the wax component and / or lubricity imparting component, the plastics component and the vegetable oil. %, 30 to 50% by volume of the plastics component, and 5 to 40% by volume of the vegetable oil.
A wax component is a component mainly extracted at the time of a degreasing process, and if it is a component which can be extracted at the time of a degreasing process, it is not necessary to limit the kind. Preferred examples of the wax component include paraffin wax and microcrystalline wax, and paraffin wax is particularly preferred from the viewpoint of degreasing properties.

  Further, in the present invention, in order to ensure the strength of the molded product after degreasing, the blending amount of the wax component is reduced as much as possible, and the total amount of the wax component, the plastics component, and the vegetable oil is 100% by volume, 30 to 45%. It is preferable to set it as volume%. When the wax component is less than 30% by volume, less binder is extracted by the degreasing treatment. Moreover, fluidity | liquidity falls at the time of injection molding, and defects, such as insufficient filling of a molded object, arise. On the other hand, when the wax component exceeds 45% by volume, the amount of the plastics component is reduced as a result, the strength of the molded body after degreasing is reduced, and the molded body is deformed or handled. Problems such as damage to the product occur. Therefore, it is preferable to limit the blending amount of the wax component to a range of 30 to 45% by volume with respect to 100% by volume of the total amount of the wax component, the plastics component, and the vegetable oil. In addition, More preferably, it is 30-40 volume%.

  In the present invention, a lubricity imparting component may be used instead of a part or all of the wax component. “Lubricity-imparting component” as used herein is added to impart lubricity and improve fluidity to the metal powder or alloy powder that is the raw material powder of the powder injection-molded body, and facilitates injection molding. The strength of the molded article can also be increased, and if necessary, it can be blended in place of part or all of the wax component. The lubricity-imparting component is preferably stearic acid or a metal salt of stearic acid. Examples of the metal salt of stearic acid include zinc stearate and stearyl stearate.

  Further, the plastics component to be blended is not particularly limited as long as it remains in the injection molded body and can secure the strength of the molded body, but in the production of a large metal powder injection molded body From the viewpoint of securing the strength of the desired molded article, it is preferable to use a thermoplastic resin such as a polypropylene resin, a polyacetal resin, or a polyethylene resin. Among these, a polypropylene resin is preferable from the viewpoint of degreasing properties.

  In addition, it is preferable that the compounding quantity of a plastics component shall be 30-50 volume% with respect to 100 volume% of total amounts of a wax component and / or a lubricity provision component, a plastics component, and vegetable oil. If the amount of the plastics component is less than 30%, the strength of the molded body after degreasing is insufficient, and problems such as deformation and breakage occur. On the other hand, if it is added in a large amount exceeding 50%, the moldability is lowered, and in addition, the degreasing rate is lowered due to a decrease in wax components and the like. For this reason, the compounding amount of the plastics component is limited to a range of 30 to 50% by volume. In addition, More preferably, it is 35-50 volume%.

  Moreover, as a vegetable oil to mix | blend, it is preferable to set it as a non-drying vegetable oil. Examples of non-drying vegetable oils include peanut oil, castor oil, olive oil, and salad oil, and it is preferable to use one or more selected from among them. In addition, when using 2 or more types of vegetable oil, it is preferable to set it as the combination of 1 type, or 2 or more types chosen from castor oil and other peanut oil, olive oil, and salad oil. By adding vegetable oil to the binder, the freezing point of the binder is lowered, the fluidity of the binder is improved, the compatibility of the binder with metal powder and plastics powder is improved, and the amount of shrinkage during cooling is reduced. As a result, the occurrence of cracks in the molded body is suppressed, and the detachability from the mold is improved.

  In addition, it is preferable that the compounding quantity of vegetable oil shall be 5-40 volume% with respect to 100 volume% of total amounts of a wax component and / or lubricity provision component, a plastics component, and vegetable oil. When the blending amount of the vegetable oil is less than 5%, the fluidity is lowered and the moldability is lowered. On the other hand, if it exceeds 40%, the amount of the wax component or plastics component is reduced, resulting in a decrease in strength of the molded product after degreasing, an increase in defects such as deformation and breakage, and high-temperature gold. There is a problem that oil is separated when injected into the mold. For this reason, it is preferable to limit the compounding quantity of vegetable oil to 5-40 volume%. In addition, More preferably, it is 10-35 volume%.

In the present invention, the kneaded product (compound) subjected to the kneading and pulverizing steps as described above is charged into a metal powder injection molding apparatus, plasticized, and then injection molded to obtain a molded body having a predetermined shape.
First, a preferable configuration of the metal powder injection molding apparatus used in the present invention will be described. In FIG. 1, an example of a structure of the metal powder injection molding apparatus used by this invention is shown.
The metal powder injection molding apparatus shown in FIG. 1 has a fixed mold 1 and a moving mold 2 as molds. The moving side mold 2 is configured so as to be able to move toward and away from the fixed side mold 1. The fixed mold 1 and the movable mold 2 are configured in such a shape that a cavity 3 can be formed between the fixed mold 1 and the movable mold 2 at the time of joining (clamping). Needless to say, the cavity 3 is formed in a shape corresponding to a desired product shape.

  Further, the fixed side mold 1 and the moving side mold 2 are provided with a plurality of flow paths 6 in the vicinity of the surface 1a and the surface 2a of the cavity 3, respectively. The flow path 6 is connected to a heating medium supply source 7 and a cooling medium supply source 8 through a valve 9, and a heating medium (for example, steam) or a cooling medium (for example, water) is selectively flowed by the valve 9. Thereby, the surface 1a and the surface 2a of the cavity 3 are rapidly heated or rapidly cooled.

The fixed mold 1 is provided with a gate 4 to which a metal powder injection molding apparatus 10 is connected. The plasticized compound is injected into the cavity 3 through the gate 4 by the metal powder injection molding apparatus 10.
In the present invention, a metal powder or an alloy powder is used as a raw material powder, a binder is mixed into the raw material powder, kneaded and pulverized to form a compound, and the compound is preferably charged into a metal powder injection molding apparatus having the above-described configuration. By applying a heat cycle method having the following procedure, a large-sized metal powder injection molded body having a predetermined shape is obtained.

The basic flow of the manufacturing method of the large metal powder injection molding of this invention is shown in FIG. Hereinafter, the manufacturing method of the large metal powder injection molded body of the present invention will be described with reference to FIG.
First, the fixed mold 1 and the movable mold 2 are brought into close contact with each other, and the fixed mold 1 and the movable mold 2 are clamped with a predetermined clamping force (step 21). As a result, a cavity 3 is formed between the fixed mold 1 and the movable mold 2. Next, the heating medium is flowed from the heating medium supply source 7 to the flow path 6 through the valve 9 to perform mold heating for heating the mold surface (cavity 3 surface) (step 22). The heating medium is preferably steam, high-temperature water (hot water), or high-temperature oil.

  Next, the temperature of the cavity surface 1a, 2a is measured by a temperature sensor (not shown) to confirm whether the temperature of the cavity surface 1a, 2a has reached a predetermined temperature (step 23). If the temperature of the cavity 3 surfaces 1a and 2a has reached a predetermined temperature, the process proceeds to the next step. If the predetermined temperature has not been reached, further heating of the mold surface is continued. The “predetermined temperature” here is preferably not less than the deflection temperature under load of the plastic component blended in the compound and not more than the thermal decomposition temperature. Here, “deflection temperature under load” is a temperature measured at a load of 1.8 MPa in accordance with the provisions of international standard ISO 75 (JIS 7191).

After confirming that the temperatures of the surfaces 3a and 2a of the cavity 3 have reached a predetermined temperature, the plasticized compound is injected into the cavity 3 through the gate 4 by the metal powder injection molding apparatus 10, and the cavity 3 3 is filled to form a molded body having a predetermined shape (step 24).
A predetermined amount of this compound is injected into the cavity 3, and it is confirmed whether or not the predetermined amount of the compound is filled in the cavity 3 (step 25). When a predetermined amount of compound is filled in the cavity 3, the process proceeds to the next step. When a predetermined amount of the compound is not filled in the cavity 3, the metal powder injection molding apparatus 10 continues to inject the compound. Preferably, after injecting the compound, it is preferable to apply a holding pressure that maintains a predetermined pressure for a certain period of time.

  When a predetermined amount of the compound is filled in the cavity 3, a signal notifying that the predetermined amount of the compound has been injected is sent from the metal powder injection molding apparatus 10 (step 26). When this signal is detected, the valve 9 is operated, the supply of the heating medium from the heating medium supply source 9 to the flow path 6 is stopped, and the supply of the cooling medium from the cooling medium supply source 8 to the flow path 6 is started. Mold cooling is performed (step 27). As a result, the vicinity of the flow path 6, that is, the vicinity of the cavity 3 surfaces 1a and 2a is rapidly cooled, and the temperature of the molded body is lowered to a temperature at which the compound is not deformed. After further cooling and solidification of the compound, the moving side mold 2 is moved to open the mold, and the molded body is taken out (step 28).

  Preferably, when injection molding is performed using the above-described compound, a high-precision large-sized metal powder injection-molded body can be produced by applying the above-described heat cycle method. Although not particularly limited in the present invention, a large metal powder injection molded body obtained by the above-described manufacturing method is degreased part of the binder and then sintered under appropriate conditions to have a large characteristic. It can be set as the metal powder injection molding sintered compact.

The alloy powder shown in Table 1 was used as a raw material powder. Moreover, the binder raw material of the mixing | blending shown in Table 2 was mixed, and it melt-stirred at temperature: 170-240 degreeC, and was set as various binders. The raw material powder, various binders, and the raw material powder were mixed in the blending amounts shown in Table 3, and kneaded at a temperature of 170 to 240 ° C. to obtain a mixed kneaded product (compound).
Furthermore, the cooled and solidified mixed kneaded material (compound) is pulverized to form an injection molding compound, which is put into a hopper of a metal powder injection molding apparatus and plasticized at a cylinder temperature of 160 to 230 ° C. Was injected into the mold cavity at a pressure (60 MPa) to obtain a metal powder injection molded body having a predetermined shape.

  For injection molding, we used an “EC100N II-2Y molding machine” manufactured by Toshiba Machine Co., Ltd. equipped with “High-speed heat cycle molding unit” manufactured by Ono Sangyo Co., Ltd., which has a heating medium supply source and a cooling medium supply source. . The mold used has a flow path 6 in the vicinity of the cavity surface as shown in FIG. 1, and the cavity shape is (a) a flower pot-shaped product having a weight of 260 g (bottom surface: 80 mmφ, top surface: 120 mmφ, height: 100mm, wall thickness: 3mm) (a) Fan-shaped product with a weight of 200g (fan shape: 120mmφ, maximum wall thickness 3mm, thin-walled part 2mm), (c) is a box-shaped product with a weight of 220g (wall thickness: 3.0mm, (Size: 80 × 120 × 15 mm).

  First, “mold heating” was performed in which steam as a heating medium was passed through the flow path 6 to heat the cavity surfaces 1 a and 2 a of the mold to a predetermined temperature. The predetermined temperature (heating temperature) was set to 60 to 120 ° C., which is higher than the deflection temperature under load of the polypropylene resin, which is a plastic component of the binder blended in the compound, and lower than the thermal decomposition temperature. After the cavity surfaces 1a and 2a reach a predetermined temperature, an "injection" is performed in which a predetermined amount of the plasticized compound is injected from the metal powder injection molding apparatus 10 into the cavity 3 through the gate 4 and filled. . Then, after applying “holding pressure” for holding for a certain time at a predetermined pressure, water is allowed to flow as a cooling medium through the flow path 6, and the temperature of the cavity surfaces 1a and 2a is 30 to 40 ° C., which is a temperature at which the molded body does not deform. The “cooling of the mold” was performed. Next, after performing “opening” in which the moving side mold 2 was moved to open the mold, the molded body was taken out. Table 3 shows the time of one cycle of the mold heating, injection, holding pressure, mold cooling, mold opening, and taking-out process. In some cases, only the cooling medium was used without supplying the heating medium to the mold.

About the obtained metal powder injection-molded body, surface appearance property inspection and internal defect inspection were performed. The test method was as follows.
(1) Surface appearance property inspection About the obtained molded object, the external appearance was observed visually and the presence or absence of surface defects, such as a wrinkle and a weld, shape defects, such as insufficient filling, and a crack (defect) was investigated. When one or more of these defects existed, it was evaluated as x, and when the defect did not exist at all, the appearance property was evaluated as ◯.
(2) Internal property inspection About the obtained molded object, the internal property was investigated by the X-ray transmission inspection, and the presence or absence of the defect was investigated. The case where a defect exists was set as x, and other cases were set as ◯, and the internal properties were evaluated.

  The obtained results are shown in Table 3.

  In all of the examples of the present invention, neither a surface defect nor an internal defect exists, and a large-sized metal powder injection molded article having a good appearance property and internal property is obtained. On the other hand, in comparative examples that are outside the scope of the present invention, surface defects are present and appearance properties are reduced, or internal defects are present and internal properties are reduced.

DESCRIPTION OF SYMBOLS 1 Fixed side metal mold | die 2 Movement side metal mold | die 3 Cavity 4 Gate 6 Flow path 7 Heating medium supply source 8 Cooling medium supply source 9 Valve
10 Metal powder injection molding equipment

Claims (5)

Metal powder or alloy powder is used as a raw material powder, a binder is mixed into the raw material powder, kneaded and pulverized into a compound, and the compound is charged into a metal powder injection molding apparatus and injection molded into a mold to form a predetermined shape. In the method for producing a metal powder injection molded body,
During the injection molding,
A plastic of the binder in which a mold capable of heating or cooling the cavity surface of the mold by a heating medium or a cooling medium is used, and the cavity surface of the mold is blended with the compound using steam as a heating medium Heating to a heating temperature that is higher than the deflection temperature under load and lower than the thermal decomposition temperature,
Next, a predetermined amount of the plasticized compound is injected into the heated cavity, and the cavity is filled.
After the filling is complete, the cavity surface of the mold is cooled to below the deflection temperature under load of the plastics component of the binder using water as a cooling medium,
A large metal powder injection molding characterized by applying a heat cycle method comprising solidifying the compound and then taking out the molded body, and forming the molded body into a large metal powder injection molded body having a weight of 100 g or more. Body manufacturing method.   The binder component is 30% to 45% by volume of the wax component and / or lubricity imparting component with respect to 100% by volume of the total amount of the wax component and / or lubricity imparting component, the plastics component and the vegetable oil, and the plastics component The method for producing a large metal powder injection-molded article according to claim 1, wherein 30 to 45% by volume and 5 to 40% by volume of the vegetable oil are blended.   The method for producing a large metal powder injection molded body according to claim 2, wherein the plastic component of the binder is one of polypropylene resin, polyacetal resin, and polyethylene resin.   The said vegetable oil of the said binder is added with a castor oil, and is 1 type, or 2 or more types among peanut oil, olive oil, and salad oil, The manufacture of the large metal powder injection molded object of Claim 2 or 3 characterized by the above-mentioned. Method.   A large metal powder injection molded product produced by the method for producing a large metal powder injection molded product according to any one of claims 1 to 4.

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