Patent Application
20150217371
1. Technical Field
The present invention relates to a manufacturing method of a compact, a manufacturing method of a structure, and a cutting processed material.
2. Related Art
In the related art, in order to manufacture a structure configured of a metallic material in a desired shape, a casting method, a forging method, a machining processing method, a discharge processing method, a laser processing method, a press processing method, a powder metallurgical method, and the like are known.
For example, in JP-A-2007-215854, a manufacturing method of a metal frame which is a superstructure of a prosthetic implant including a step of attaching a material to a penta-axial control machining center, a step of processing the material from one surface while adjusting a processing position and a slope, and a step of manufacturing a metal frame by inverting the material and by processing the material from the other surface is disclosed.
According to such a method, it is possible to easily manufacture the metal frame with high accuracy even when a user is not a person of experience having advanced skills.
On the other hand, according to a usage of a processed product, a material referred to as a difficult-to-process material or a difficult-to-cut material such as a refractory alloy, which is difficult to process may be used as a metallic material. When a difficult-to-process material is processed by a machining center or the like, it is necessary to sufficiently slow a processing speed. For this reason, a long time is required for manufacturing the metal frame, and thus manufacturing efficiency is low.
In addition, due to the fact that the difficult-to-process material is processed, a processing tool becomes abraded at an early stage, and processing accuracy easily fluctuates.
Further, in order to suppress friction between the processing tool and the material, and to cool the processing tool or the material, a large quantity of cutting oil is used. For this reason, it is necessary to clean the manufactured metal frame, and thus a decrease in manufacturing efficiency or an increase in environmental load is caused.
An advantage of some aspects of the invention is to provide a manufacturing method of a structure enabling a structure to be easily manufactured in a target shape in a short time, a manufacturing method of a compact enabling a compact which forms the structure in the target shape to be easily manufactured in a short time by baking the compact, and a cutting processed material enabling the compact in the target shape to be easily machined in a short time by using the cutting processed material in a cutting process.
An aspect of the invention is directed to a manufacturing method of a compact including pressure molding a composition including a metallic powder and a binder to obtain a green compact in which a relative density of a constituent material of the metallic powder with respect to real density is greater than or equal to 70% and less than or equal to 90%; and processing the green compact to obtain a compact.
With this configuration, it is possible to make high machinability and high shape retainability compatible in the green compact, and thus it is possible to easily manufacture the compact which forms a structure in a target shape in a short time by baking the compact.
In the manufacturing method of a compact according to the aspect of the invention, it is preferable that an average particle diameter of the metallic powder is greater than or equal to 1 μm and less than or equal to 15 μm.
With this configuration, the green compact which enables the process to be more accurately performed, and enables the compact in a designed shape to be efficiently machined is obtained.
In the manufacturing method of a compact according to the aspect of the invention, it is preferable that the binder includes polyvinyl alcohol a saponification degree of which is greater than or equal to 90 mol % and less than or equal to 98 mol %.
With this configuration, when the obtained green compact is used in the processing step, a green compact which is homogeneous and has high green density is obtained, and thus it is possible to impart high machinability to the green compact. In such a green compact, the metallic powder and the binder are uniformly dispersed in an interior portion, and thus irrespective of a process performed, it is difficult for cracking or collapse to occur.
In the manufacturing method of a compact according to the aspect of the invention, it is preferable that the processing includes first processing in which the green compact is subjected to a first process, and thus a processing trace passing through the green compact is formed with a part of a circumference of a region to be the compact being left, and second processing in which the green compact is subjected to a second process, and thus the region is separated from the green compact by eliminating the part, and the compact is obtained.
With this configuration, the compact does not drop out from the green compact during the first processing, and thus it is possible to handle the compact in a state of being integrated with the green compact. For this reason, it is possible to maintain a position of the compact with respect to a processing position reference point of the green compact, and it is possible to suppress a decrease in processing accuracy of the compact in the first processing.
In the manufacturing method of a compact according to the aspect of the invention, the part is in the shape of a rod, and a minimum cross-sectional area of the part is greater than or equal to 0.2 mm2 and less than or equal to 75 mm2.
With this configuration, the compact is prevented from dropping out from the green compact in the first processing, and the part is easily cut in the second processing, and thus at this time, it is possible to inhibit occurrence of deformation or the like in the compact.
Another aspect of the invention is directed to a manufacturing method of a structure including baking the compact obtained by the manufacturing method of a compact according to the aspect to obtain a structure configured of a metal sintered body.
With this configuration, it is possible to easily manufacture the structure in the target shape in a short time.
Still another aspect of the invention is directed to a manufacturing method of a structure including performing a first process with respect to the green compact obtained by the manufacturing method of a compact according to the aspect, and thus forming a processing trace passing through the green compact with a part of a circumference of a region to be the compact being left, and obtaining the compact; baking the compact to obtain a metal sintered body; and eliminating a portion of the metal sintered body corresponding to the part to obtain a structure.
With this configuration, it is possible to easily manufacture the structure in the target shape in a short time.
Yet another aspect of the invention is directed to a cutting processed material including a metallic powder and a binder, in which a relative density of a constituent material of the metallic powder with respect to real density is greater than or equal to 70% and less than or equal to 90%, and the cutting processed material is used in a cutting process.
With this configuration, the cutting processed material which enables the compact in the target shape to be easily machined in a short time by using the cutting processed material in the cutting process is obtained. Therefore, by baking the compact, it is possible to manufacture the structure in the target shape.
The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements.
Hereinafter, a manufacturing method of a compact, a manufacturing method of a structure, and a cutting processed material according to the invention will be described in detail with reference to preferred embodiments illustrated in the attached drawings.
Furthermore, in the following description, for convenience of the description, an upper side of
A manufacturing method of a compact according to this embodiment includes a compacting step in which a composition including a metallic powder and a binder is pressure molded, and a green compact 1 illustrated in
First, the composition including the metallic powder and the binder is pressure molded, and thus the green compact (an embodiment of a cutting processed material according to the invention) 1 is obtained. The green compact 1 is used in the compact processing step described later, and thus is used for machining the compact 2 in a desired shape. That is, the green compact 1 has both mechanical strength withstanding a cutting process and processability.
First, the composition including the metallic powder and the binder is prepared. The composition mainly includes the metallic powder and the binder.
The metallic powder is a powder of a metallic material. The metallic material is not particularly limited, and any material may be used insofar as the material is able to be sintered. As an example, an elementary substance such as Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Pd, Ag, In, Sn, Sb, Hf, Ta, W, Ir, Pt, Au, Pb, and Bi, an alloy including these elements, or the like is included. In addition, the metallic powder may be a mixed powder in which two or more types of powders having different compositions from each other are mixed, or may be a mixed powder of a metallic powder and a ceramic powder.
Among them, as an Fe-based alloy, for example, stainless steel, low carbon steel, carbon steel, heat resistant steel, die steel, high-speed tool steel, an Fe—Ni alloy, an Fe—Ni—Co alloy, and the like are included.
In addition, as an Ni-based alloy, for example, an Ni—Cr—Fe-based alloy, an Ni—Cr—Mo-based alloy, an Ni—Fe-based alloy, and the like are included.
In addition, as a Co-based alloy, for example, a Co—Cr-based alloy, a Co—Cr—Mo-based alloy, a Co—Al—W-based alloy, and the like are included.
In addition, as a Ti-based alloy, for example, an alloy of Ti and a metal element such as Al, V, Nb, Zr, Ta, and Mo is included, and specifically, Ti-6Al-4V, Ti-6Al-7Nb, and the like are included.
In addition, as an Al-based alloy, for example, duralumin, and the like are included.
In addition, as a ceramic material configuring the ceramic powder, for example, an oxide-based ceramic material such as alumina, magnesia, beryllia, zirconia, yttria, forsterite, steatite, wollastonite, mullite, cordierite, ferrite, sialon, and cerium oxide, a non-oxide-based ceramic material such as silicon nitride, aluminum nitride, boron nitride, titanium nitride, silicon carbide, boron carbide, titanium carbide, and tungsten carbide are included.
Furthermore, in the materials as described above, a so-called difficult-to-process material may be included. In the invention, it is possible to manufacture the structure 3 in a target shape regardless of processability of the metallic material itself or the ceramic material itself. For this reason, by using the metallic powder of a difficult-to-process material, it is possible to easily manufacture various structures 3 of the difficult-to-process material which are difficult to manufacture by a method of the related art. At this time, this is useful in that a structure having high dimensional accuracy is able to be manufactured regardless of the shape of the structure 3, and thus a structure having a high additional value is able to be manufactured.
In addition, an average particle diameter of the metallic powder is preferably greater than or equal to 1 μm and less than or equal to 15 μm, and is more preferably greater than or equal to 2 μm and less than or equal to 10 μm. By using the metallic powder having such an average particle diameter, the green compact 1 is able to be more accurately processed, and thus the compact with a designed shape is able to be machined efficiently. That is, when the average particle diameter of the metallic powder is below the lower limit described above, mechanical strength of the entire green compact 1 is decreased, and thus cracks or collapse may occur in the green compact 1 which is a processing target according to a size or a shape of the compact to be machined in the compact processing step described later. In addition, a filling property of the metallic powder is decreased, and thus a content ratio of the metallic powder of the green compact 1 decreases. Accordingly, when the compact machined from the green compact 1 is baked in a baking step described later, a contraction ratio increases, and thus dimensional accuracy of a sintered body may decrease. In contrast, when the average particle diameter of the metallic powder exceeds the upper limit described above, the processing tool in the compact processing step described later is more likely to be in contact with the particle of the metallic powder, and flatness of a processed surface is easily degraded, and thus dimensional accuracy of the compact may decrease according to the shape of the compact to be machined.
Furthermore, in a particle size distribution obtained by a laser diffraction method, the average particle diameter of the metallic powder is a particle diameter when a cumulative particle size on a mass basis is 50% from a small diameter side.
In addition, a maximum particle diameter of the metallic powder is preferably greater than or equal to 10 μm and less than or equal to 100 μm, and is more preferably greater than or equal to 10 μm and less than or equal to 50 μm. By using the metallic powder having such a maximum particle diameter, it is possible to especially improve a filling property of the metallic powder of the green compact 1. As a result, it is possible to machine the compact 2 which has high processing accuracy in the compact processing step and excellent flatness of the processed surface. Furthermore, since the increased filling property mainly depends on packing between the particles of the metallic powder, it is considered that the increased filling property is obtained due to especially excellent packing between the particles due to the average particle diameter of the metallic powder being set in the range described above, and the maximum particle diameter being set in the range described above.
In the particle size distribution obtained by the laser diffraction method, the maximum particle diameter of the metallic powder is a particle diameter when the cumulative particle size on a mass basis is 99.9% from the small diameter side.
Further, when the average particle diameter of the metallic powder is D50, the particle diameter when the cumulative particle size on a mass basis is 10% from the small diameter side is D10 in the particle size distribution obtained by performing the laser diffraction method with respect to the metallic powder, and the particle diameter when the cumulative particle size on a mass basis is 90% from the small diameter side is D90, (D90−D10)/D50 is preferably greater than or equal to 0.5 and less than or equal to 5, and is more preferably greater than or equal to 1.0 and less than or equal to 3.5. The metallic powder satisfying such a condition is especially useful from a viewpoint of a filling property of the metallic powder of the green compact 1. That is, the metallic powder satisfying such a condition is able to exert a more uniform compression force on the entire green compact 1 at the time of compacting since the particle size distribution is comparatively narrow. For this reason, in the obtained green compact 1, density is more uniform, and a variation in residual stress at the time of the compacting is suppressed to be small. As a result, compacts 21 and 22 are hardly deformed according to release of stress in the compact processing step described later, and a contraction ratio at the time of sintering described later is more even, and thus it is possible to suppress a decrease in dimensional accuracy according to contraction to a minimum.
In addition, as the metallic powder, for example, a metallic powder which is manufactured by various powderizing methods such as an atomization method (for example, a water atomization method, a gas atomization method, a high-speed rotation water flow atomization method, and the like), a reductive method, a carbonyl method, and a grinding method is used.
Among them, a metallic powder manufactured by the atomization method is preferably used, and a metallic powder manufactured by the water atomization method or the high-speed rotation water flow atomization method is more preferably used. The atomization method is a method of manufacturing a metallic powder by crashing fused metal (molten metal) into fluid (liquid or gas) which is sprayed at a high speed, and by pulverizing and cooling the molten metal. By manufacturing the metallic powder by such an atomization method, it is possible to efficiently manufacture an extremely fine powder. In addition, a particle shape of the obtained powder is similar to a spherical shape due to the action of surface tension. For this reason, when the composition including such a metallic powder is pressure molded to be the green compact 1, the green compact 1 having a high filling rate is obtained.
In addition, when a minor axis of the particle of the metallic powder is S [μm], and a major axis thereof is L [μm], an average value of an aspect ratio defined by S/L is preferably greater than or equal to 0.4 and less than or equal to 1, and is more preferably greater than or equal to 0.6 and less than or equal to 0.9. A shape of the metallic powder having such an aspect ratio is comparatively similar to a spherical shape, and thus a filling rate increases at the time of the compacting. As a result, it is possible to optimize a relative density of the green compact 1.
Furthermore, the major axis is a maximum length which is able to be taken from a projection image of the particle, and the minor axis is a maximum length in a direction perpendicular to the maximum length. Then, an aspect ratio is obtained with respect to 100 particles, and an average value thereof is the “average value of the aspect ratio” described above.
In addition, tap density of the metallic powder is preferably greater than or equal to 3.5 g/cm3, and is more preferably greater than or equal to 4 g/cm3. According to the metallic powder having such a high tap density, when the green compact 1 is obtained, a filling property of the particles is especially improved. For this reason, finally, it is possible to obtain the green compact 1 a relative density of which is optimized. Furthermore, the upper limit is not particularly limited, and for example, is allowed to be a real density of the metallic powder.
As the binder, for example, various resins such as a polyolefin such as a polyethylene, a polypropylene, and an ethylene-vinyl acetate copolymer, an acrylic resin such as polymethyl methacrylate, and polybutyl methacrylate, a styrene resin such as a polystyrene, polyvinyl chloride, polyvinylidene chloride, a polyamide, a polyester such as polyethylene terephthalate, and polybutylene terephthalate, a polyether, polyvinyl alcohol, polyvinyl butyral, polyvinyl pyrrolidone, or a copolymer thereof, a polysaccharide such as a methyl cellulose, an ethyl cellulose, and a hydroxyethyl cellulose, and various organic binders such as a higher fatty acid ester, and a higher fatty acid amide are included, and one, or two or more of these are able to be used by being mixed.
A content ratio of the binder in the green compact 1 is naturally determined according to a relative density of the green compact 1, composition of the metallic powder, or the like, and as an example, is preferably greater than or equal to 10 volume % and less than or equal to 70 volume %, and is more preferably greater than or equal to 20 volume % and less than or equal to 60 volume %. In a case where the content ratio of the binder is within the range described above, when the green compact 1 is used in the compact processing step described later, it is possible to obtain high machinability. That is, when the content ratio of the binder is below the lower limit, an amount of the binder existing between the particles of the metallic powder is reduced, and thus a binding force between the particles of the metallic powder is weakened, and the green compact 1 may be deformed at the time of being processed. In contrast, when the content ratio of the binder exceeds the upper limit, the content ratio of the metallic powder of the green compact 1 relatively decreases. For this reason, a contraction ratio at the time of sintering the compact increases, and thus dimensional accuracy of the sintered body may decrease.
In addition, among them, the binder preferably includes at least one of the polyvinyl alcohol and the acrylic resin as a main material, and more preferably includes a mixture of the polyvinyl alcohol and the acrylic resin as a main material. The binder including such a component as a main material is able to especially improve machinability of the green compact 1. That is, when the green compact 1 including such a binder is used in the compact processing step described later, processability (machinability) by the processing tool is especially improved, and thus the green compact 1 is easily processed into a designed shape. As a result, it is possible to especially efficiently machine the compact in a designed shape.
A content ratio of the polyvinyl alcohol and a content ratio of the acrylic resin in the binder are preferably greater than or equal to 5 mass % and less than or equal to 100 mass %, and are more preferably greater than or equal to 10 mass % and less than or equal to 95 mass %, respectively. By respectively setting the content ratio of the polyvinyl alcohol and the content ratio of the acrylic resin to be within the range described above, it is possible to make machinability and shape retainability of the green compact 1 compatible. For this reason, the green compact 1 is able to be machined into a designed shape, and thus the compact having higher dimensional accuracy is obtained.
In addition, in a case where the polyvinyl alcohol and the acrylic resin are concurrently used, when the content ratio of the acrylic resin is 1, the content ratio of the polyvinyl alcohol is preferably greater than or equal to 0.2 and less than or equal to 5 in a mass ratio, and is more preferably greater than or equal to 0.5 and less than or equal to 3. By setting a combination ratio between the polyvinyl alcohol and the acrylic resin to be within the range described above, it is possible to make machinability and shape retainability of the green compact 1 more highly compatible, and thus it is possible to machine the compact having especially high dimensional accuracy in the compact processing step.
Furthermore, in this case, a copolymer in which the polyvinyl alcohol and the acrylic resin are copolymerized may be used. By using such a copolymer, as described above, an effect attained by concurrently using the polyvinyl alcohol and the acrylic resin is remarkable, and homogeneity of the green compact 1 especially increases, and thus dimensional accuracy of the compact is improved.
As such a copolymer, for example, a copolymer in which an acrylic acid-based resin is copolymerized in partially saponified polyvinyl alcohol, and the like are included.
Among them, as the polyvinyl alcohol, polyvinyl alcohol a saponification degree of which is greater than or equal to 90 mol % and less than or equal to 98 mol % is preferably used, and polyvinyl alcohol a saponification degree of which is greater than or equal to 92 mol % and less than or equal to 94 mol % is more preferably used. When the green compact 1 is used in the compact processing step described later, such polyvinyl alcohol contributes to imparting higher machinability to the green compact 1. Reasons for attaining such an effect are not clear, but one of the reasons is that a content ratio of a hydroxyl group of the polyvinyl alcohol is optimized by setting the saponification degree of the polyvinyl alcohol to be within the range described above. That is, in a case where the content ratio of the hydroxyl group is optimized, when the metallic powder is granulated, the polyvinyl alcohol readily becomes present between the metal particles, and thus a granulation property increases. Because the content ratio of the hydroxyl group is optimized, the strength of hydrogen bonding between the metallic powder and the polyvinyl alcohol thus increases. Thus, when a granulation property is improved, a granulated powder with a uniform particle size distribution is easily manufactured, and by using such a granulated powder, the green compact 1 having high homogeneous green density is able to be obtained. In such a green compact 1, the metallic powder and the binder are uniformly dispersed in an interior portion, and thus irrespective of a process performed, it is difficult for cracks or collapse to occur.
Furthermore, the saponification degree of the polyvinyl alcohol described above is measured on the basis of a method regulated by JIS K 6726.
In addition, as the polyvinyl alcohol, polyvinyl alcohol a polymerization degree of which is greater than or equal to 100 and less than or equal to 3000 is preferably used, and polyvinyl alcohol a polymerization degree of which is greater than or equal to 200 and less than or equal to 2500 is more preferably used. When the green compact 1 is used in the compact processing step described later, such polyvinyl alcohol improves a binding property between the particles of the metallic powder due to the binder, and thus contributes to imparting higher machinability to the green compact 1. In addition, by setting the polymerization degree to be within the range described above, solubility of the polyvinyl alcohol with respect to a polar solvent is improved. For this reason, when the metallic powder is granulated in manufacturing of the green compact 1, the metallic powder is granulated while the binder including the polyvinyl alcohol is uniformly attached to the vicinity of the particle of the metallic powder, and thus a more homogeneous green compact 1 is obtained. Irrespective of a process performed with respect to such a green compact 1, a compact in a designed shape is able to be machined.
Furthermore, the polymerization degree of the polyvinyl alcohol described above is measured on the basis of a method regulated by JIS K 6726.
In addition, as necessary, in addition to the metallic powder or the binder, various additive agents such as a dispersant, a lubricating agent, a plasticizing agent, an antioxidizing agent, a rust preventive agent, a surfactant agent, and a defatting accelerator may be added to the green compact 1. In this case, it is preferable that a total amount of the additive agents in the green compact 1 is less than or equal to 10 mass %.
Among them, as the plasticizing agent, for example, phthalic acid ester (for example: DOP, DEP, and DBP), adipic acid ester, trimellitic acid ester, sebacic acid ester, and the like are included, and one, or two or more of these are able to be used by being mixed.
In addition, as the lubricating agent, for example, waxes, a higher fatty acid, an alcohol, a fatty acid metal, a non-ionic surfactant agent, a silicone-based lubricating agent, and the like are included, and one, or two or more of these are able to be used by being mixed.
Among them, as the waxes, for example, vegetable wax such as candelilla wax, carnauba wax, rice wax, Japan wax, and jojoba oil, animal wax such as beeswax, lanolin, and spermaceti wax, mineral wax such as montan wax, ozokerite, and ceresin, natural wax such as petroleum-based wax such as paraffin wax, microcrystalline wax, and petrolatum, synthetic hydrocarbon such as a polyethylene wax, modified wax such as a montan wax derivative, a paraffin wax derivative, and a microcrystalline wax derivative, hydrogenated wax such as hardened castor oil, a hardened castor oil derivative, synthetic wax such as a fatty acid such as 12-hydroxystearic acid, an acid amide such as stearic acid amide, and an ester such as phthalic anhydride imide are included.
In addition, as the higher fatty acid, for example, stearic acid, oleic acid, linoleic acid, and the like are included, and in particular, a saturated fatty acid such as lauric acid, myristic acid, palmitic acid, stearic acid, and arachidic acid is preferably used.
In addition, as the alcohol, for example, a polyhydric alcohol, polyglycol, polyglycerol, and the like are included, and in particular, cetyl alcohol, stearyl alcohol, oleyl alcohol, mannitol, and the like are preferably used.
In addition, as the fatty acid metal, for example, a compound of a higher fatty acid such as lauric acid, stearic acid, succinic acid, stearyl lactic acid, lactic acid, phthalic acid, benzoic acid, hydroxystearic acid, ricinoleic acid, naphthenic acid, oleic acid, palmitic acid, and erucic acid, and a metal such as Li, Na, Mg, Ca, Sr, Ba, Zn, Cd, Al, Sn, Pb, and Cd is included, and in particular, magnesium stearate, calcium stearate, sodium stearate, zinc stearate, calcium oleate, zinc oleate, magnesium oleate, and the like are preferably used.
In addition, as the non-ionic surfactant agent, for example, Electrostripper-TS-2, Electrostripper-TS-3 (both are manufactured by Kao Corporation), and the like are included.
In addition, as the silicone-based lubricating agent, for example, dimethylpolysiloxane and a modified product thereof, carboxyl-modified silicone, α-methylstyrene-modified silicone, α-olefin-modified silicone, polyether-modified silicone, fluorine-modified silicone, hydrophilic modified special silicone, polyether-olefin-modified silicone, epoxy-modified silicone, amino-modified silicone, amide-modified silicone, alcohol-modified silicone, and the like are included.
Among them, the composition preferably includes the lubricating agent as the additive agent, and more preferably includes at least one of the higher fatty acid and the fatty acid metal. The additive agent is able to especially improve a lubricating property between the particles of the metallic powder, and is able to especially suppress a negative influence with respect to the binder. For this reason, it is possible to further improve machinability of the binder described above. That is, the lubricating agent improves a lubricating property of the particles of the metallic powder, and thus when the green compact 1 is processed by the processing tool, it is possible to reduce friction resistance between the particles of the metallic powder or friction resistance between the processing tool and the particles of the metallic powder, and thus it is possible to inhibit occurrence of unintended deformation (cracks, collapse, or the like) in the green compact 1 due to the process. Therefore, when the green compact 1 including such a lubricating agent is used in the compact processing step described later, it is possible to especially efficiently machine the compact in a designed shape.
Further, in the composition for manufacturing the green compact 1, as necessary, a solvent may be included. The solvent is not particularly limited insofar as the binder is able to be dissolved or dispersed in a solvent, and an organic solvent such as terpineol, butyl carbitol, acetone, and toluene is used in addition to water.
In addition, as necessary, the composition may be in the form of a granulated powder which is obtained through a granulating process, or may be in the form of a kneaded product which is obtained through a kneading process. The form of the composition is suitably selected according to a molding method of a composition described later.
Among them, an average particle diameter of the granulated powder is not particularly limited, and is preferably greater than or equal to 10 μm and less than or equal to 300 μm, and is more preferably greater than or equal to 30 μm and less than or equal to 150 μm. Accordingly, in the manufacturing of the green compact 1 described later, a pressurizing force is easily exerted on the granulated powder. As a result, the green compact 1 having excellent easiness of processing and excellent shape retainability is obtained.
Furthermore, in a particle size distribution obtained by a laser diffraction method, the average particle diameter of the granulated powder is a particle diameter when a cumulative particle size on amass basis is 50% from a small diameter side.
Further, the average particle diameter of the granulated powder is preferably greater than or equal to 2 times and less than or equal to 30 times the average particle diameter of the metallic powder included therein, and is more preferably greater than or equal to 3 times and less than or equal to 20 times the average particle diameter of the metallic powder. By setting the average particle diameter of the granulated powder to be within the range described above, it is possible to further improve easiness of processing and shape retainability of the green compact 1.
Next, the prepared composition is pressure molded, and thus the green compact 1 is obtained.
A molding method is not particularly limited, and a press molding method, an extrusion molding method, an injection molding method, and the like are included.
A molding pressure in the press molding method is preferably greater than or equal to 10 MPa and less than or equal to 1000 MPa (greater than or equal to 0.1 t/cm2 and less than or equal to 10 t/cm2), and is more preferably greater than or equal to 50 MPa and less than or equal to 300 MPa.
In addition, a molding temperature in the press molding method is preferably greater than or equal to 20° C. and less than or equal to 70° C. as a temperature of the composition.
A molding pressure in the extrusion molding method is preferably greater than or equal to 10 MPa and less than or equal to 500 MPa (greater than or equal to 0.1 t/cm2 and less than or equal to 5 t/cm2), and is more preferably greater than or equal to 50 MPa and less than or equal to 200 MPa.
In addition, a molding temperature in the extrusion molding method is preferably greater than or equal to 80° C. and less than or equal to 210° C. as the temperature of the composition.
A molding pressure in the injection molding method is preferably greater than or equal to 10 MPa and less than or equal to 500 MPa (greater than or equal to 0.1 t/cm2 and less than or equal to 5 t/cm2), and is more preferably greater than or equal to 50 MPa and less than or equal to 200 MPa.
In addition, a molding temperature in the injection molding method is preferably greater than or equal to 80° C. and less than or equal to 210° C. as the temperature of the composition.
By setting the molding pressure and the molding temperature to be within the range described above, the green compact 1 having a high relative density and excellent mechanical characteristics is obtained. That is, suitable packing between the particles of the metallic powder occurs, and thus mechanical characteristics of the green compact 1 are sufficiently improved, and the green compact 1 which is able to withstand the compact processing step described later is obtained. In addition, the binder is solidified by being fused and then cooled according to the molding temperature, and thus the particles of the metallic powder are fixed to each other through the binder. From this viewpoint, it is possible to improve mechanical characteristics of the green compact 1. Then, such a green compact 1 is processed, and thus it is possible to efficiently machine the compact 2 having high dimensional accuracy.
Here, machinability and shape retainability of the green compact 1 including the metallic powder, the binder, or the like in the compact processing step depend on a compacting state thereof.
The inventors have intensively performed studies regarding a balance between such machinability and shape retainability. Then, it was found that high machinability and high shape retainability of the green compact 1 are able to be compatible when a relative density of the green compact 1 is greater than or equal to 70% and less than or equal to 90%, and thus the invention has been completed.
That is, when the relative density of the green compact 1 is below the lower limit, it is considered that a filling property of the metallic powder or the binder of the green compact 1 is degraded, or a content ratio of the metallic powder in the green compact 1 decreases, and as a result thereof, the green compact 1 may be easily deformed in the compact processing step, or a contraction ratio of the compact 2 may be easily deformed largely at the time of the sintering. In contrast, when the relative density of the green compact 1 exceeds the upper limit, it is considered that stress at the time of the compacting easily remains in the green compact 1, or a content ratio of the binder in the green compact 1 decreases and mechanical strength decreases, and as a result thereof, the green compact 1 may be easily deformed by the stress remaining in the green compact 1 being released in the compact processing step, or the green compact 1 may be easily deformed due to interference with the processing tool.
Furthermore, the relative density of the green compact 1 is obtained by measuring density of the green compact 1, and by calculating a relative value of the density with respect to real density of a constituent material of the metallic powder.
In addition, the shape of the green compact 1 is not particularly limited, and for example, may be a cuboid, a cube, a sphere, a polygonal columnar body, and the like, and the green compact 1 illustrated in
Furthermore, in the compact processing step described later, an example in which a main surface 11 and a main surface 12 (refer to
Next, as illustrated in
Furthermore, in the compact processing step, the compact 2 may be machined at one time from the green compact 1 by a single machining process, and in this embodiment, a case where the compact processing step is divided into a “first processing step” and a “second processing step” will be described.
First, the green compact 1 illustrated in
The green compact 1 illustrated in
In the green compact 1 illustrated in
In addition, when each of the compacts 21 and 22 is completely surrounded by the processing trace 26, the compacts 21 and 22 drop out from the green compact 1, and thus in the first processing step, a part which is not a portion of the processing trace 26 is disposed in the circumference of the two compacts 21 and 22 in order to prevent the dropping out of the compacts 21 and 22. The portion is a connection portion 25 connecting the compacts 21 and 22 and the green compact 1. By disposing such a connection portion 25, the compacts 21 and 22 do not drop out from the green compact 1 in the middle of the first processing step, and the compacts 21 and 22 are handled in a state of being integrated with the green compact 1. For this reason, it is possible to maintain a position of the compacts 21 and 22 with respect to a point which is a processing position reference point of the green compact 1, and it is possible to suppress a decrease in processing accuracy of the compacts 21 and 22 in the first processing step. Furthermore, the processing trace 26 may not be formed, and the processing trace 27 may surround each of the compacts 21 and 22. In this case, in the second processing step described later, a volume to be processed increases, and thus it is possible to suppress a decrease in processing accuracy of the compacts 21 and 22 in the first process.
In addition, the processing trace 27 which does not pass through the green compact 1 is formed, and thus the connection portion 25 illustrated in
In addition, a plurality of connection portions 25 illustrated in
Furthermore, a shape of each of the connection portions 25 illustrated in
That is, when the minimum cross-sectional area of each of the connection portions 25 is below the lower limit, mechanical strength of each of the connection portions 25 is insufficient, and the connection portion 25 may break, and thus deformation may occur according to the shape of the compacts 21 and 22. In contrast, when the minimum cross-sectional area of each of the connection portions 25 exceeds the upper limit, in the second processing step described later, each of the connection portions 25 is difficult to cut off, and thus deformation or the like may occur in the compacts 21 and 22 at the time of the cutting off operation.
Furthermore, as described above, when operational efficiency of the second processing step is considered, the number of connection portions 25 disposed in each of the compacts 21 and 22 may be minimized, and the minimum cross-sectional area of each of the connection portions 25 may be minimized, but when easiness of the deformation of the compacts 21 and 22 in the first processing step is considered, the number of connection portions 25 disposed in each of the compacts 21 and 22 may be maximized, and the minimum cross-sectional area of each of the connection portions 25 may be maximized, and thus the number of connection portions 25 and the minimum cross-sectional area may be determined based on this.
In addition, a thickness t of each of the connection portions 25 is preferably set to be greater than or equal to 5% and less than or equal to 90% of the length L, and is more preferably set to be greater than or equal to 10% and less than or equal to 80% of the length L. Accordingly, each of the connection portions 25 has sufficient mechanical strength in order to support each of the compacts 21 and 22.
Line A-A of
Furthermore, when the green compact 1 is subjected to the first process, any one of the main surfaces 11 and 12 of the green compact 1 is usually placed to be in contact with an upper surface of a stage of a processing device. For this reason, in the first process, in order to form the processing traces 26 and 27 having a cross-sectional shape as illustrated in
However, an inverting operation of the green compact 1 may not be necessary according to a holding method of the green compact 1. For example, when there is a region which is not used for forming the compacts 21 and 22 such as an outer circumferential portion of the green compact 1, and the like, the first processing step is able to be performed without performing a replacing operation such as inversion of the green compact 1 by simply holding this region. In this case, a processing device which is able to perform multi-axial control is preferably used.
In the first process, any processing device is able to be used. For example, as the processing device, a machining center, a milling machine, a drilling machine, a lathe, and the like are included. Among them, a processing device provided with a computer aided manufacturing (CAM) system is preferably used. In the CAM system, an accurate process which is able to faithfully reproduce a model designed by a computer aided design (CAD) system is able to be performed. For this reason, it is useful in that the compacts 21 and 22 are able to be efficiently machined to be similar to a target shape even when the user is not a person skilled in the art.
Next, the green compact 1 after being subjected to the first processing step is subjected to a second process (the second processing step).
The compacts 21 and 22 illustrated in
Furthermore, in the second process which cuts off and eliminates the connection portion 25, a small force is necessary for the process, and a volume to be processed is limited, and thus it is possible to perform a manual process in addition to the process by the processing device as described above.
As described above, the compact processing step has been described, but the number of steps divided in the compact processing step is not limited to the two steps described above, and may be divided into three steps or more.
Furthermore, the compact 2 contracts in the baking step described above, and thus in this compact processing step, the shape or the size of the compact 2 is suitably set such that the sintered body has a target shape and a target size on the basis of an amount of the contraction.
First, a first embodiment of a manufacturing method of a structure according to the invention will be described.
The manufacturing method of a structure according to this embodiment has a step in which the compact 2 manufactured by the manufacturing method of a compact according to the embodiment is baked, and thus the sintered body is obtained. Thus, the structure 3 illustrated in
First, before the baking, the compact 2 may be subjected to a defatting treatment. By performing the defatting treatment (a debinding treatment), a defatted body is obtained.
Specifically, the defatting treatment is performed by decomposing the binder by heating the compact 2, and by eliminating the binder from the compact 2.
As the defatting treatment, for example, a method of heating the compact 2, a method of exposing the compact 2 to gas decomposing the binder, and the like are included.
When the method of heating the compact 2 is used, heating conditions of the compact 2 vary slightly according to a composition or an amount of the binder mixed in, are preferably a temperature greater than or equal to 100° C. and less than or equal to 750° C.×a time greater than or equal to 0.1 hours and less than or equal to 20 hours, and are more preferably a temperature greater than or equal to 150° C. and less than or equal to 600° C.×a time greater than or equal to 0.5 hours and less than or equal to 15 hours. Accordingly, it is possible to perform necessary defatting of the compact 2 sufficiently without sintering the compact 2. As a result, it is possible to prevent a large quantity of the binder component from remaining in the defatted body.
In addition, an atmosphere at the time of heating the compact 2 is not particularly limited, and an atmosphere of a reducing gas such as hydrogen, an atmosphere of an inert gas such as nitrogen and argon, an atmosphere of an oxidizing gas such as atmospheric air, or a reduced pressure atmosphere in which these atmospheres are reduced in pressure, and the like are included.
On the other hand, as the gas decomposing the binder, for example, ozone gas and the like are included.
Furthermore, such a defatting step is performed in a plurality of stages (steps) having different defatting conditions, and thus it is possible to more rapidly decompose and eliminate the binder in the compact 2 such that the binder does not remain in the compact 2.
In addition, as necessary, the defatted body may be subjected to a machining process such as cutting, grinding, and cutting off. The defatted body has comparatively low hardness and comparatively excellent plasticity, and thus it is possible to prevent a shape of the defatted body from collapsing, and it is possible to easily perform the machining process. According to such a machining process, finally, a sintered body having high dimensional accuracy is able to be easily obtained.
Furthermore, when the amount of the binder in the compact 2 is small, the baking treatment described later may also serve as the defatting treatment, and thus, in this case, the defatting treatment is able to be omitted.
Next, the defatted body (or the compact 2) is subjected to the baking treatment.
Due to the baking, the metallic powder of the defatted body diffuses into interfaces between the particles, and thus is sintered. Accordingly, the sintered body of the metallic powder is obtained, and the structure 3 is obtained.
A baking temperature varies according to a composition, a particle diameter, or the like of the metallic powder used for manufacturing the compact 2, and as an example, the baking temperature is greater than or equal to 980° C. and less than or equal to 1330° C. In addition, the baking temperature is preferably greater than or equal to 1050° C. and less than or equal to 1260° C.
In addition, a baking time is greater than or equal to 0.2 hours and less than or equal to 7 hours, and is preferably greater than or equal to 1 hour and less than or equal to 6 hours.
Furthermore, in the middle of the baking step, a sintering temperature, or a baking atmosphere described later may be changed.
By setting a baking conditions to be within such a range, it is possible to prevent a crystalline structure from being excessively sintered due to excessive sintering and thus from becoming bloated, and it is possible to sufficiently sinter the entire defatted body. As a result, it is possible to obtain a sintered body having high density and excellent mechanical characteristics.
In addition, an atmosphere at the time of the baking is not particularly limited, and when prevention of excessive oxidation of the metallic powder is considered, an atmosphere of a reducing gas such as hydrogen, an atmosphere of an inert gas such as argon, or a reduced pressure atmosphere in which these atmospheres are reduced in pressure, and the like are preferably used.
Furthermore, in the structures 3 illustrated in
As described above, according to the manufacturing method of a structure according to the invention, the compact 2 in a target shape is machined by processing the green compact 1 in which the particles of the metallic powder are bound by the binder, and thus the sintered body (the structure 3) in a target shape is obtained by baking the compact 2. For this reason, compared to a case where a metallic material is subjected to a process, it is possible to extremely easily perform a processing operation in a short time, and it is possible to improve processing accuracy. As a result, it is possible to easily obtain the structure 3 in a target shape in a short time.
In addition, since the processing accuracy is high, it is possible to faithfully reflect design data by the CAD system in the shape of the compact 2 by the CAM system. For this reason, even when the user is not a person of experience having advanced skills, it is possible to manufacture the structure 3 in a target shape.
Further, even when the metallic powder included in the green compact 1 is a powder of a difficult-to-process material or a difficult-to-cut material, there is little influence on the machinability of the green compact 1. Therefore, the structure 3 in a target shape which is configured of the difficult-to-process material is also able to be easily obtained in a short time.
In addition, in the cutting process of the green compact 1, friction occurring between the green compact 1 and the processing tool 5 is extremely small compared to a case where the metallic material is subjected to the cutting process. Therefore, in the invention, it is not necessary to use cutting oil necessary for cooling the processing tool 5 or the like, and thus it is possible to inhibit transmutation or degradation of the metallic powder due to being in contact with the cutting oil. In addition, it is not necessary to perform cleaning off of the cutting oil, and thus it is possible to suppress the environmental load, and to realize cost reduction of the manufacturing of the structure 3.
Further, since the friction occurring between the green compact 1 and the processing tool 5 is small, it is possible to inhibit abrasion of the processing tool 5. For this reason, it is possible to prolong the life of the processing tool 5, and thus it is possible to realize cost reduction and high efficiency.
Next, a second embodiment of the manufacturing method of a structure according to the invention will be described.
Hereinafter, the second embodiment will be described, and in the following description, differences between the first embodiment described above and the second embodiment will be mainly described, and the description of the same matters will be omitted.
This embodiment is identical to the first embodiment, except that the baking step is positioned between a step corresponding to the first processing step and a step corresponding to the second processing step. Therefore, the step (a “sintered body processing step” described later) corresponding to the second processing step of the first embodiment is not a processing step which is performed with respect to the green compact 1, but is a processing step which is performed with respect to the sintered body obtained by sintering the green compact 1.
First, similar to the first embodiment, the green compact 1 is obtained.
Next, similar to the first processing step of the first embodiment, the green compact 1 in which the compact 2 and each of the connection portions 25 are formed is obtained. Furthermore, in this embodiment, only the first processing step with respect to the green compact 1 is referred to as the compact processing step.
3 Baking Step
Next, the green compact 1 in which the compact 2 and each of the connection portions 25 are formed is subjected to the baking treatment. Accordingly, the green compact 1 in which the compact 2 and each of the connection portions 25 are formed is sintered, and thus the sintered body is obtained.
Next, the obtained sintered body is subjected to the same process as that of the second processing step of the first embodiment. That is, in the sintered body, a portion corresponding to the connection portion 25 is cut off and eliminated. Accordingly, the sintered body of the compact 2, that is, the structure 3 is obtained.
In the second embodiment as described above, a portion to be processed in the sintered body processing step is a portion corresponding to the connection portion 25 in the sintered body, and is a portion having an extremely small processed area compared to a size of the entire sintered body. Therefore, it is possible to efficiently perform the sintered body processing step, and the shape of the compact 2 is hardly influenced at the time of the process, and thus similar to the first embodiment, it is possible to easily obtain the sintered body (the structure 3) having high dimensional accuracy.
Thus, in the second embodiment as described above, the same actions and the same effects as those of the first embodiment are obtained.
As described above, the manufacturing method of a compact, the manufacturing method of a structure, and the cutting processed material according to the invention have been described on the basis of the preferred embodiments, but the invention is not limited thereto.
Next, specific examples of the invention will be described.
1 First, a Co—Cr—Mo—Si—N-based alloy raw material was fused in a high-frequency induction furnace, and was powderized by a high-speed rotation water flow atomization method, and thus a metallic powder was obtained. Next, the metallic powder was graded by using a standard sieve having a sieve pore size of 150 μm. An alloy composition of the obtained metallic powder will be described later. Furthermore, for specifying the alloy composition, a solid-state emission spectrometer manufactured by SPECTRO Co., Ltd. (a spark emission spectrometer, model: SPECTROLAB, and type: LAVMB08A) was used. In addition, for quantitative analysis of C (carbon), a carbon and sulfur analyzer (CS-200) manufactured by LECO Co., Ltd. was used.
In a composition ratio of the Co—Cr—Mo—Si—N-based alloy, Co was a main component, a content ratio of Cr was greater than or equal to 26 mass % and less than or equal to 35 mass %, a content ratio of Mo was greater than or equal to 5 mass % and less than or equal to 12 mass %, a content ratio of Si was greater than or equal to 0.3 mass % and less than or equal to 2.0 mass %, and a content ratio of N was greater than or equal to 0.09 mass % and less than or equal to 0.5 mass %.
In addition, Vickers hardness of the Co—Cr—Mo—Si—N-based alloy was 500, and real density thereof was 8.32 g/cm3.
2 Next, a binder was dissolved in water, and a binder solution was prepared. Furthermore, an amount of water in the binder solution was 50 g per 1 g of the binder. In addition, as the binder, polyvinyl alcohol was used. Furthermore, physical properties of the polyvinyl alcohol used were as shown in Table 1.
3 Next, a metallic powder was put into a treatment container of a granulation device. Then, the binder solution was sprayed from a spray nozzle of the granulation device onto the metallic powder in the treatment container, and the metallic powder was rolled and granulated, and thus a granulated powder (a composition) was obtained.
4 Next, the obtained granulated powder was used for molding under the following molding conditions, and thus a green compact was obtained. The obtained green compact was in the shape of a disk having a diameter of 100 mm and a thickness of 15 mm. In addition, a relative density of the green compact was 84%.
Molding method: press molding
Molding pressure: 100 MPa (1 t/cm2)
5 Next, the obtained green compact was subjected to a cutting process (a first process) by using a penta-axial processing machine. Accordingly, a processing trace was formed in the green compact such that a compact and connection portions illustrated in
Furthermore, a minimum cross-sectional area of each of the connection portions was confirmed as being within a range greater than or equal to 1 mm2 and less than or equal to 10 mm2.
A photograph illustrating a state of the green compact after being subjected to the first process is illustrated in
6 Next, a process (a second process) which cuts off and eliminates the connection portion was performed. Accordingly, a compact as illustrated in
7 Next, the machined compact was subjected to a defatting treatment under the following defatting conditions, and thus a defatted body was obtained.
Heating temperature: 470° C.
Heating time: 1 hour
Heating atmosphere: a nitrogen atmosphere
8 Next, the obtained defatted body was subjected to a baking treatment under the following baking conditions, and thus a sintered body (a structure) as illustrated in
Heating temperature: 1300° C.
Heating time: 3 hours
Heating atmosphere: an argon atmosphere
9 Next, the obtained sintered body was assembled, and thus a clamp (a structure) as illustrated in
A photograph of the clamp obtained thereby is illustrated in
Each clamp (a structure) was obtained in the same manner as described in the Sample No. 1 except that manufacturing conditions of the green compact were changed as shown in Table 1. Furthermore, ASTM F75 described in the table indicates a casting material F75 of a cobalt chromium alloy in an ASTM standard. In addition, SKH51 described in the table indicates one type of high-speed tool steel regulated by a JIS standard.
An ingot satisfying F75 which is the ASTM standard of the casting material of the cobalt chromium alloy was prepared.
Next, the ingot was subjected to the cutting process by using the penta-axial processing machine. Accordingly, a member as illustrated in
Next, the obtained member was assembled, and the clamp as illustrated in
Each clamp (a structure) was obtained by the same manner as described in the Sample No. 1 except that the manufacturing conditions of the green compact were changed as shown in Table 1.
As described above, the manufacturing conditions of the structure of each Sample No. are shown in Table 1.
Furthermore, in Table 1, the samples which correspond to the invention are referred to as “Example”, and samples which do not correspond to the invention are referred to as “Comparative Example”.
Dimensions of the structure of each Sample No. were measured. Then, the measured dimensions and dimensions of design data were compared, and thus dimensional accuracy was evaluated according to the following evaluation standards.
A: Dimensional accuracy was extremely high (a deviation from a design value was less than 0.2 mm)
B: Dimensional accuracy was high (a deviation from a design value was greater than or equal to 0.2 mm and less than 0.5 mm)
C: Dimensional accuracy was slightly high (a deviation from a design value was greater than or equal to 0.5 mm and less than 0.7 mm)
D: Dimensional accuracy was low (a deviation from a design value was greater than or equal to 0.7 mm) 2.2 Evaluation of Processing Time
When the structure of each Sample No. was obtained, a time (a processing time) required for the compact to be machined from the green compact was obtained. Next, when a time required for the compact of the Sample No. 16 to be machined was set to 1, a relative value of the time required for the compact of each Sample No. to be machined was obtained. Then, the obtained relative value was evaluated according to the following evaluation standards.
A: Processing time was extremely short (the relative value was less than 0.7)
B: Processing time was short (the relative value was greater than or equal to 0.7 and less than 0.85)
C: Processing time was slightly short (the relative value was greater than or equal to 0.85 and less than 1)
D: Processing time was long (the relative value was greater than or equal to 1)
Surface roughness of a surface corresponding to a processed surface of the structure of each Sample No. at the time of being machined from the green compact was evaluated according to the following evaluation standards.
A: Surface roughness was extremely small
B: Surface roughness was small
C: Surface roughness was slightly small
D: Surface roughness was large
As described above, evaluation results of 2.1 to 2.3 are shown in Table 1.
As is clear from Table 1, structures manufactured by a method corresponding to Examples had high dimensional accuracy. In addition, a time required for manufacturing the structure was relatively short. Further, it was confirmed that the surface roughness of the processed surface was small and smoothness was comparatively high.
In contrast, structures manufactured by a method corresponding to Comparative Examples had low dimensional accuracy. From this, it was confirmed that the dimensional accuracy of the manufactured structure decreased when the relative density of the green compact was excessively low or excessively high. In addition, it could be understood that the dimensional accuracy was high and a time required for the process was extremely long when the structure was machined from the ingot.
The entire disclosure of Japanese Patent Application No. 2014-016648, filed Jan. 31, 2014 is expressly incorporated by reference herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2014-016648 | Jan 2014 | JP | national |
