Patent Application
20240269742
The present application is based on, and claims priority from JP Application Serial Number 2023-018978, filed Feb. 10, 2023, the disclosure of which is hereby incorporated by reference herein in its entirety.
The present disclosure relates to a composite sintered compact and a method for producing a composite sintered compact.
Metal materials have a luster unique to metals. As such, metal materials contribute to improving the design quality when used for the exterior of various products.
For example, JP 2017-226216 A discloses a metal sheet having a decoration applied to its surface. The decoration has a symbol, pattern, character, picture, or other information display formed by one or a combination of two or more selected from: lines, points, and surfaces formed of concavities or convexities of 2.0 mm or less; concave or convex surfaces formed due to a step at the boundary of the outer circumference; and coloring. Such a decoration can be clearly recognized because it is a combination of concavities and convexities.
However, depending on the application of the metal sheet described in JP 2017-226216 A, the surface of the metal sheet on which the decoration is provided may be scratched or stained during use, and the design such as a pattern or a character may degrade compared to the initial state. In such a case, the surface of the metal sheet may be re-polished to restore the state of the design.
However, when the surface is re-polished, the depth of a concave surface or the height of a convex surface of the concavities and convexities may be reduced. Further, when the polishing amount during the re-polishing is large, the concavities and convexities disappear. As a result, the function of information display deteriorates and the design quality deteriorates.
In addition, there is a limit to the variations of expression in the decoration formed of concavities and convexities. That is, the types of designs that can be expressed by depths of concavities and heights of convexities are limited. As such, there is room for improvement from the viewpoint of sufficiently improving design quality.
This leads to challenge of realizing a metal material that has a better design quality and in which the design quality can be maintained even when the metal material is subjected to re-polishing.
A composite sintered compact according to an application example of the present disclosure including:
A method for producing a composite sintered compact according to an application example of the present disclosure is a method for producing the composite sintered compact described above, including:
Hereinafter, a composite sintered compact and a method for producing a composite sintered compact of the present disclosure will be described in detail based on an embodiment illustrated in the accompanying drawings.
First, a composite sintered compact according to an embodiment will be described.
The composite sintered compact 1 illustrated in
The first portion 11 is composed of a sintered compact of a first stainless steel. The second portion 12 is composed of a sintered compact of a second stainless steel a steel type of which is different from that of the first stainless steel. The first portion 11 and the second portion 12 are diffusion-bonded to each other at an interface IF between the first portion 11 and the second portion 12. The diffusion-bonding in the present specification particularly refers to sintered diffusion-bonding, which is bonding that utilizes the diffusion of atoms that occurs at the interface IF by bringing powders into close contact with each other at a temperature below the melting point of the constituent materials. By diffusion-bonding, structural integration at the interface IF can be achieved, and gaps are less likely to occur. As such, two portions having different properties can be placed adjacent to each other, making it possible to improve the aesthetic appearance while suppressing the deterioration of the aesthetic appearance and the deterioration of the mechanical properties due to gaps.
In
The step between the first surface 13 and the second surface 14 is 100 μm or less. With such a configuration, the upper surface 101 can be regarded as a substantially flat surface. That is, when the step between the first surface 13 and the second surface 14 is within the above range, a person is hardly aware of the presence of the step even when the step is visible to the person. As such, a person who looks at the upper surface 101 can recognize the upper surface 101 as a flat and smooth surface. As a result, for example, a simple and smart image can be imparted to the upper surface 101, making it possible to improve the design quality of a metal product composed of the composite sintered compact 1. Note that, in the present specification, the term “flat” refers to having a small step regardless of whether the surface is a flat surface or a curved surface. That is, the term “flat” refers to a state in which the first surface 13 and the second surface 14 can be regarded as one surface.
A difference between the light reflectance of the first surface 13 during polishing and the light reflectance of the second surface 14 during polishing is 2% or greater. With such a configuration, a sufficient difference in light reflectance between the first surface 13 and the second surface 14 can be ensured, and thus it is possible for a person who looks at the upper surface 101 to be aware of the presence of the first surface 13 and the second surface 14, that is, the boundary between the first surface 13 and the second surface 14. Accordingly, appropriately selecting the boundary results in the upper surface 101 that can display a pattern, an image, a character, a symbol, other information, or the like, making it possible to improve the design quality.
As described above, despite being a substantially flat surface, the upper surface 101 is imparted with a design based on a sufficient difference in light reflectance. Since this difference in light reflectance is based on the two steel species of the first stainless steel and the second stainless steel, the difference in light reflectance does not disappear even when the upper surface 101 is subjected to re-polishing. That is, despite being a mirror surface, the upper surface 101 has a design that will not disappear even when being subjected to re-polishing. As such, the configuration described above allows for the realization of the composite sintered compact 1 in which a good design can be maintained even when the upper surface 101 is repeatedly subjected to re-polishing.
As described above, the first portion 11 is composed of a sintered compact of the first stainless steel.
The first stainless steel is appropriately selected based on the relationship with the second stainless steel so as to satisfy the difference in light reflectance described above. Examples of the first stainless steel include austenitic stainless steel, ferritic stainless steel, martensitic stainless steel, precipitation hardening stainless steel, and austenitic-ferritic (duplex) stainless steel.
Examples of austenitic stainless steel include SUS301, SUS301L, SUS301J1, SUS302B, SUS303, SUS304, SUS304Cu, SUS304L, SUS304N1, SUS304N2, SUS304LN, SUS304J1, SUS304J2, SUS305, SUS309S, SUS310S, SUS312L, SUS315J1, SUS315J2, SUS316, SUS316L, SUS316N, SUS316LN, SUS316Ti, SUS316J1, SUS316J1L, SUS317, SUS317L, SUS317LN, SUS317J1, SUS317J2, SUS836L, SUS890L, SUS321, SUS347, SUSXM7, and SUSXM15J1.
Examples of ferritic stainless steel include SUS405, SUS410L, SUS429, SUS430, SUS430LX, SUS430J1L, SUS434, SUS436L, SUS436J1L, SUS445J1, SUS445J2, SUS444, SUS447J1, and SUSXM27.
Examples of martensitic stainless steel include SUS403, SUS410, SUS410S, SUS420J1, SUS420J2, and SUS440A.
Examples of precipitation hardening stainless steel include SUS630 and SUS631.
Examples of austenitic-ferritic (duplex) stainless steel include SUS329J1, SUS329J3L, and SUS329J4L.
Note that, the above grades are material grades based on the JIS. In this specification, steel species are distinguished based on the material grades described above. Therefore, different steel species mean different material grades described above. Needless to say, the first stainless steel and the second stainless steel may have different classifications based on their crystal structures. In addition, the first stainless steel and the second stainless steel may be steel species of the same classification but have different material grades. For example, the first stainless steel and the second stainless steel may both be a steel species of the same classification, such as austenitic stainless steel, as long as the two have different material grades. The material grades do not necessarily have to be based on the JIS, and may be based on another set of standards.
The sintered compact of the first stainless steel in the present specification is obtained by molding and sintering a powder of the first stainless steel. That is, the first portion 11 is a portion produced by powder metallurgy using the powder of the first stainless steel. Powder metallurgy makes it possible to easily form the first portion 11 having a target shape or a shape close to the target shape.
As described above, the second portion 12 is composed of a sintered compact of the second stainless steel.
The second stainless steel is appropriately selected based on the relationship with the first stainless steel so as to satisfy the difference in light reflectance described above. The second stainless steel is appropriately selected from, for example, the steel species exemplified as those of the first stainless steel.
The sintered compact of the second stainless steel in the present specification is obtained by forming and sintering a powder of the second stainless steel. That is, the second portion 12 is a portion produced by powder metallurgy using the powder of the second stainless steel. Powder metallurgy makes it possible to easily form the second portion 12 having a target shape or a shape close to the target shape.
Note that, in the composite sintered compact 1 illustrated in
The step between the first surface 13 and the second surface 14 is 100 μm or less as described above, but is preferably 30 μm or less, more preferably 10 μm or less. When the step is within the range described above, a person who looks at the upper surface 101 can recognize the upper surface 101 as a flat and smooth surface. In addition, even when the upper surface 101 is repeatedly polished, the step after polishing is highly likely to fall within the range described above. Therefore, when the step is within the range described above, it is possible to realize a metal product that has an appearance which hardly changes even when the metal product is subjected to repeated polishing and whose aesthetic appearance can be maintained. Note that, when the step exceeds the upper limit value, a person who looks at the upper surface 101 becomes aware of the presence of the step. As such, the design quality of a metal product composed of the composite sintered compact 1 deteriorates.
The step between the first surface 13 and the second surface 14 is measured by, for example, a stylus type step/surface roughness meter, a laser microscope, or the like. However, a value measured by a laser microscope is preferable from the viewpoint of simplicity and measurement in consideration of in-plane variations.
The difference between the light reflectance of the first surface 13 during polishing and the light reflectance of the second surface 14 during polishing is set to 2% or greater as described above, but is preferably set to 3% or greater, and more preferably set to 4% or greater. This makes it easy to visually recognize the first surface 13 and the second surface 14 as regions different from each other based on the difference in light reflectance. That is, this makes it possible for a person who looks at the upper surface 101 to become aware of the boundary between the first surface 13 and the second surface 14. This results in an improvement to the design quality of a metal product composed of the composite sintered compact 1.
Meanwhile, the upper limit value of the difference in light reflectance does not necessarily need to be set, but is preferably set to 20% or less, and more preferably 10% or less from the viewpoint of avoiding an increase in the procurement cost of materials, that is, from the viewpoint of being able to achieve the effect described above with easily procurable materials.
Providing the difference in light reflectance in this manner allows the upper surface 101 to be a mirror surface based on the above-described favorable flatness and to have information such as a pattern or a character with the mirror surface serving as the background. Such a design has excellent aesthetic appearance and cannot be achieved by a known design utilizing concavities and convexities.
The light reflectance is measured on a polished surface. The polished surface refers to a surface finished according to surface finish symbol #400 specified in JIS G 4304:2005. The light reflectance is the average specular reflectance of light with a wavelength of from 360 to 830 nm that is incident on the polished surface at an incident angle of 5°. The specular reflectance is the ratio of the specularly reflected light beam to the light beam incident on the polished surface. Furthermore, the average specular reflectance is the average value of the specular reflectance in the wavelength range of from 360 to 830 nm. Measuring of the specular reflectance can employ, for example, the UV-visible spectrophotometer V-770DS and the automatic absolute reflectance measurement unit ARMN-920, both available from JASCO Corporation.
Further, the difference in specular reflectance of light with a wavelength of 555 nm is preferably from 2% to 20%, more preferably from 3% to 10%. This ensures a sufficient difference in light reflectance even at the wavelength with the highest relative luminous efficiency. This allows for the realization of a design that appears to have a higher contrast and an excellent aesthetic appearance to a person who looks at the upper surface 101.
The difference between the Vickers hardness of the first surface 13 and the Vickers hardness of the second surface 14 is not limited, but is preferably 300 or less, more preferably 250 or less, and even more preferably 200 or less. By setting the difference in Vickers hardness to be within the range described above, the difference between the polishing amount of the first surface 13 and the polishing amount of the second surface 14 can be made sufficiently small when the upper surface 101 is subjected to polishing. As such, the flatness of the upper surface 101 can be satisfactorily maintained even after polishing. This allows for the realization of a metal product whose initial design quality can be more satisfactorily maintained even when the metal product is subjected to repeated polishing.
A Vickers hardness meter is used to measure the Vickers hardness. The measurement load is 5 kgf (49 N), and the load holding time is 10 seconds.
The Vickers hardness of each of the first surface 13 and the second surface 14 is preferably from 100 to 500, and more preferably from 150 to 400. This allows the first surface 13 and the second surface 14 to be satisfactorily polished while reducing the likelihood of scratches when the upper surface 101 is subjected to polishing.
The combination of the steel species of the first stainless steel and the second stainless steel is appropriately selected based on the difference in light reflectance as described above. However, the combination is preferably one in which the first stainless steel is austenitic stainless steel and the second stainless steel is precipitation hardening stainless steel. In this combination, the difference in light reflectance is particularly large. This makes it possible to obtain the composite sintered compact 1 that can yield a metal product having a more favorable aesthetic appearance of design.
Note that, in the present embodiment, the second portion 12 surrounds the first portion 11 when the upper surface 101 is seen in plan view. Wish such an arrangement, the first portion 11 can be protected by the second portion 12. In this case, the second stainless steel is preferably a steel species having a Vickers hardness higher than that of the first stainless steel. This can give the second portion 12 higher ability to protect the first portion 11. This makes it possible to obtain the composite sintered compact 1 that can realize a metal product having good design quality with suppressed occurrence of, for example, scratches, dents, chipping, and the like.
It should be noted that the term “surround” preferably means that the second portion 12 forms a closed ring shape as illustrated in
Now, consider a case in which the first stainless steel is, for example, an austenitic stainless steel containing Fe, Ni, and Mo, while the second stainless steel is, for example, a precipitation hardening stainless steel containing Fe, Ni, and Cu. In this case, Mo contained in the first stainless steel is hardly contained in the second stainless steel, whereas Cu contained in the second stainless steel is hardly contained in the first stainless steel. As such, by observing the diffusion states of Mo and Cu at the interface IF between the first portion 11 and the second portion 12, the state of diffusion-bonding between the first portion 11 and the second portion 12 can be evaluated. In addition, since the contents of Ni in the two steel species are very different, the state of diffusion-bonding can also be evaluated by the diffusion state of Ni.
The Cu content in the first stainless steel and the Mo content in the second stainless steel are each preferably 0.1 mass % or less, more preferably 0.05 mass % or less. This can more reliably yield the effects described above.
In the example illustrated in
In the example illustrated in
In the example illustrated in
Further, as in the above example, the first stainless steel and the second stainless steel preferably belong to different classifications of steel species. As such, the first stainless steel and the second stainless steel have different crystal structures, making it possible to achieve a difference in hue. Therefore, a difference in hue between the first portion 11 and the second portion 12 can be achieved, and a design with good contrast can be obtained.
After being subjected to polishing, the upper surface 101 may be subjected to re-polishing. In such a case, a new polishing amount of approximately 100 μm is polished by the re-polishing. In the composite sintered compact 1 according to the embodiment, even when such re-polishing is performed, the difference in light reflectance described above does not significantly decrease, and thus a good design quality can be maintained.
Specifically, the upper surface 101 including the first surface 13 and the second surface 14 is re-polished at a polishing amount of 100 μm. The light reflectance of the first surface 13 before re-polishing is denoted by Ra, and the light reflectance of the first surface 13 after re-polishing is denoted by Rb. In this case, the difference in light reflectance before and after re-polishing, or |Ra-Rb|, is preferably 10% or less, and more preferably 5% or less. As a result, the difference in light reflectance before and after re-polishing can be sufficiently reduced. This allows for the realization of the composite sintered compact 1 having good suitability for repeated re-polishing (durability).
The first surface 13 before re-polishing and the first surface 13 after re-polishing are each finished according to surface finish symbol #400 specified in JIS G 4304:2005.
Next, a method for producing a composite sintered compact according to an embodiment will be described. Here, a method for producing the composite sintered compact 1 described above will be used as an example.
The method for producing the composite sintered compact illustrated in
In the molding step S102, multicolor molding is performed using a first composition 110 and a second composition 120, resulting in a multicolor molded object 10 illustrated in
The average particle size of each of the first powder and the second powder is not limited, but is preferably from 0.5 μm to 30.0 μm, more preferably from 3.0 μm to 15.0 μm, and even more preferably from 5.0 μm to 12.0 μm. Thereby, further densification of the composite sintered compact 1 can be achieved.
The average particle size refers to the particle size D50 at which the cumulative frequency is 50% from the small diameter side in the volume-based cumulative particle size distribution of powder obtained using a laser diffraction particle size distribution measuring device.
The multicolor molding employs a multicolor molding method in which forming is performed by using two or more kinds of compositions in, for example, metal injection molding (MIM), extrusion molding, fused deposition modeling (FDM), or the like. Among these, metal injection molding is preferable. In metal injection molding, a molded object is produced by injecting raw materials into a mold, thereby efficiently producing a multicolor molded object with high dimensional accuracy.
In addition, in injection molding, the first composition and the second composition are injected into the cavity of a mold at the same time or in an alternating manner. Thereby, two kinds of compositions can be filled in the cavity. Note that, in multicolor molding, three or more kinds of compositions may be used.
In the multicolor molding method, by balancing the physical properties of the first composition and the second composition with each other, the occurrence of gaps at the interface IF is suppressed, giving the resulting composite sintered compact 1 a higher integrity.
Specifically, a temperature difference |T1−T2| between a shrinkage starting temperature T1 [° C.] of the first powder and a shrinkage starting temperature T2 [° C.] of the second powder is set to 50° C. or less. The shrinkage starting temperature T1 refers to the temperature at which shrinkage due to sintering starts to become larger than thermal expansion when the temperature of the first powder rises in a sintering treatment to be described later. The shrinkage starting temperature T2 is the temperature at which shrinkage due to sintering starts to become larger than thermal expansion of the second powder. By setting the temperature difference |T1−T2| to be within the above range, sintering can start in a temperature range where there is an overlap for the molded object of the first composition and the molded object of the second composition. Thereby, atoms constituting both powders can sufficiently diffuse at the interface IF. This allows for the production of the composite sintered compact 1 in which the first portion 11 and the second portion 12 are diffusion-bonded at the interface IF between the first portion 11 and the second portion 12. The temperature difference |T1−T2| is preferably 30° C. or less, more preferably 20° C. or less.
The shrinkage starting temperatures T1 and T2 can be determined by thermomechanical analysis (TMA). In TMA, the molded object of the first composition and the molded object of the second composition are used as samples, and the deformation amount is obtained while heating the samples in an inert atmosphere such as an argon atmosphere or a nitrogen atmosphere. The temperatures at which the samples start to shrink are referred to as shrinkage starting temperatures T1 and T2. Note that, the amount of organic binder in a sample is 10 mass % of the powder.
Each TMA curve illustrated in
In
As such, the shrinkage starting temperatures T1 and T2 can be adjusted by the steel species, particle size, specific surface area, and the like of each powder. For example, the shrinkage starting temperatures T1 and T2 can be lowered by decreasing the particle sizes of the powders or increasing the specific surface areas thereof. Further, ferritic stainless steel and austenitic stainless steel tend to have lower shrinkage starting temperatures T1 and T2 than precipitation hardening stainless steel.
The resulting multicolor molded object may be subjected to a degreasing treatment as necessary.
The heating conditions in the degreasing treatment vary slightly depending on the steel species as well as the composition and the blending amount of the organic binder, but are preferably a temperature of from 100° C. to 750° C. and a time of from 0.1 hour to 20 hours, and more preferably a temperature of from 150° C. to 600° C. and a time of from 0.5 hour to 15 hours.
The atmosphere at the time of heating the multicolor molded object is not limited, and examples thereof include an inert atmosphere such as nitrogen or argon, an oxidizing atmosphere such as air, and a reduced-pressure atmosphere obtained by reducing the pressure of these atmospheres.
In the sintering step S104, the resulting multicolor molded object is subjected to a sintering treatment. This results in the composite sintered compact 1.
As described above, the multicolor molded object has an optimized temperature difference |T1−T2|. As such, the timing at which the first powder starts to shrink and the timing at which the second powder starts to shrink can be aligned in the temperature raising process during sintering. Thereby, in the resulting composite sintered compact 1, the occurrence of gaps at the interface IF between the first portion 11 and the second portion 12 can be suppressed. This allows for the production of the composite sintered compact 1 in which the first portion 11 and the second portion 12 are satisfactorily diffusion-bonded at the interface IF between the first portion 11 and the second portion 12.
The sintering temperature varies depending on the steel species, the particle size of the powder, and the like, but is set to approximately from 980° C. to 1450° C. as an example. The sintering temperature is preferably set to approximately from 1050° C. to 1400° C.
The sintering time is set to from 0.2 hours to 7 hours, and preferably set to approximately from 1 hour to 6 hours.
Examples of the atmosphere for the sintering treatment include a reducing atmosphere such as hydrogen, an inert atmosphere such as nitrogen or argon, and a reduced-pressure atmosphere obtained by reducing the pressure of these atmospheres. The pressure of the reduced-pressure atmosphere is not limited as long as it is less than the standard pressure (100 kPa), but it is preferably 10 kPa or less, more preferably 1 kPa or less.
Thereafter, the upper surface 101 of the composite sintered compact 1 is subjected to a polishing treatment as necessary. When the step generated on the upper surface 101 exceeds 100 μm, the polishing treatment can be performed not only for the purpose of reducing the step to 100 μm or less but also for the purpose of improving the aesthetic appearance of the upper surface 101. Note that the polishing treatment may be mirror polishing or semi-mirror polishing.
Moreover, an optional finishing treatment may be performed in place of or in addition to the polishing treatment. Examples of the finishing treatment include embossing treatment, hairline treatment, vibration treatment, dulling treatment, etching treatment, chemical coloring treatment, oxidation blackening treatment, and oxidation coloring treatment.
As described above, the composite sintered compact according to the embodiment includes the first portion 11 and the second portion 12. The first portion 11 is composed of a sintered compact of the first stainless steel. The second portion 12 is composed of a sintered compact of the second stainless steel a steel type of which is different from that of the first stainless steel, and the second portion 12 is diffusion-bonded to the first portion 11 at the interface IF. The surface where the first portion 11 is exposed is referred to as the first surface 13, and the surface where the second portion 12 is exposed is referred to as the second surface 14. The step between the first surface 13 and the second surface 14 is 100 μm or less. The difference between the light reflectance of the first surface 13 during polishing and the light reflectance of the second surface 14 during polishing is 2% or greater.
Such a configuration allows for the composite sintered compact 1 whose upper surface 101 (front surface) has good design quality associated with different steel species and in which the design quality can be maintained even when the upper surface 101 is subjected to re-polishing. This allows for the realization of a metal product whose initial design quality can be more satisfactorily maintained even when the metal product is subjected to repeated polishing. In addition, since gaps are less likely to occur at the interface IF, the deterioration of the aesthetic appearance and the deterioration of the mechanical properties due to gaps can be suppressed.
Examples of such metal product include: exterior parts of watches, cameras, mobile terminal devices accessories; tableware; sporting goods; name plates; panels; trophies; interior parts of transportation equipment such as automobiles; and other housings.
Further, in the composite sintered compact according to the embodiment, the difference between the Vickers hardness of the first surface 13 and the Vickers hardness of the second surface 14 is preferably 300 or less.
With such a configuration, the difference between the polishing amount of the first surface 13 and the polishing amount of the second surface 14 can be made sufficiently small when the upper surface 101 including the first surface 13 and the second surface 14 is subjected to polishing. As such, the flatness of the upper surface 101 can be satisfactorily maintained even after polishing. This allows for the realization of a metal product whose initial design quality can be more satisfactorily maintained even when the metal product is subjected to repeated polishing.
In the composite sintered compact according to the embodiment, the first stainless steel is preferably an austenitic stainless steel containing Fe, Ni, and Mo while the second stainless steel is preferably a precipitation hardening stainless steel containing Fe, Ni, and Cu. Further, Mo is preferably diffused in a width of from 5 μm to 200 μm across the interface IF, and Cu is preferably diffused in a width of from 10 μm to 300 μm across the interface IF.
Such a configuration can improve the adhesion between the first portion 11 and the second portion 12. As a result, even when the upper surface 101 is subjected to repeated polishing, gaps or the like are less likely to occur at the interface IF, and a favorable design quality is easily maintained.
In the composite sintered compact according to the embodiment, the first surface 13 and the second surface 14 are re-polished at a polishing amount of 100 μm, and the light reflectance of the first surface 13 before re-polishing is denoted by Ra while the light reflectance of the first surface 13 after re-polishing is denoted by Rb. In this case, |Ra-Rb| is preferably 10% or less.
Such a configuration can sufficiently reduce the difference in light reflectance before and after re-polishing. This allows for the realization of the composite sintered compact 1 having good suitability for repeated re-polishing (durability).
Further, the method for producing a composite sintered compact according to the embodiment is a method for producing the composite sintered compact according to the embodiment, and includes a molding step S102 and a sintering step S104. In the molding step S102, multicolor molding is performed using the first composition containing the first powder composed of the first stainless steel and the second composition containing the second powder composed of the second stainless steel, resulting in the multicolor molded object. In the sintering step S104, the multicolor molded object is sintered, resulting in the composite sintered compact. The temperature difference |T1−T2| between the shrinkage starting temperature T1 of the first powder and the shrinkage starting temperature T2 of the second powder is 50° C. or less.
Such a configuration allows for the production of the composite sintered compact 1 whose upper surface 101 (front surface) has good design quality associated with different steel species and in which the design quality can be maintained even when the upper surface 101 is subjected to re-polishing. In addition, the first portion 11 and the second portion 12 are satisfactorily diffusion-bonded at the interface IF between the first portion 11 and the second portion 12, which allows for the production of the composite sintered compact 1 capable of suppressing the deterioration of the aesthetic appearance and the deterioration of the mechanical properties due to gaps.
Although the composite sintered compact and the method for producing a composite sintered compact according to the present disclosure have been described above based on the illustrated embodiment, the present disclosure is not limited thereto.
For example, in the composite sintered compact according to the present disclosure, each part of the embodiment described above may be replaced with any component having a similar function, and any component may be added to the embodiment described above.
In addition, the method for producing a composite sintered compact according to the present disclosure may be the embodiment described above plus an additional step having any purpose.
Next, specific examples of the present disclosure will be described.
First, SUS316L powder having an average particle size of 10.6 μm was prepared as a first powder, and SUS630 powder having an average particle size of 6.0 μm was prepared as a second powder. Note that SUS316L is an austenitic stainless steel, and SUS630 is a precipitation hardening stainless steel. The shrinkage starting temperatures of the first powder and the second powder are as presented in Table 1.
Next, a compound (first composition) containing the first powder and an organic binder and a compound (second composition) containing the second powder and an organic binder were prepared.
Next, the prepared compounds were used to prepare a multicolor molded object by metal injection molding. Subsequently, the multicolor molded object was subjected to a degreasing treatment and a sintering treatment, resulting in a composite sintered compact.
Next, the upper surface of the composite sintered compact was subjected to a polishing treatment.
Composite sintered compacts were obtained in the same manner as in Example 1, except that the production conditions for the composite sintered compacts were changed to those presented in Table 1.
Composite sintered compacts were obtained in the same manner as in Example 1, except that the production conditions for the composite sintered compacts were changed to those presented in Table 1.
Laser processing was performed on an ingot of SUS316L, forming a pattern expressed by concavities and convexities. Note that the depth of the concavities and convexities was 100 μm at maximum. The ingot on which the pattern was formed was used as the composite sintered compact of Comparative Example 4.
The composite sintered compacts of Examples and Comparative Examples 1 to 3 were each subjected to a measurement of the light reflectance of the first surface and the light reflectance of the second surface. The differences in light reflectance were then calculated. The calculation results are presented in Table 1.
A surface profile straddling the boundary between the first surface and the second surface was obtained for each composite sintered compact of Examples and Comparative Examples 1 to 3. A laser microscope was used to obtain the surface profile.
Next, the step at the boundary was calculated from the surface profile. The calculation results are presented in Table 1.
The composite sintered compacts of Examples and Comparative Examples were each subjected to a measurement of the Vickers hardness of the first surface and the Vickers hardness of the second surface. Then, the differences in Vickers hardness were calculated. The calculation results are presented in Table 1. Note that, in Comparative Example 4, the difference in Vickers hardness between the portion where concavities and convexities were formed and the portion where concavities and convexities were not formed was calculated and presented in Table 1.
The upper surface of the composite sintered compact of each Example and each Comparative Example was subjected to re-polishing. The polishing amount was 100 μm. Then, the differences in light reflectance before and after the re-polishing were calculated. The calculation results are presented in Table 1. Note that, in Comparative Example 4, the light reflectances before and after re-polishing were measured for the portion where concavities and convexities were formed, and the difference was calculated.
The upper surface of the composite sintered compact of each Example and each Comparative Example before re-polishing was observed. The observation results were evaluated in accordance with the following evaluation criteria. The evaluation results are presented in Table 1.
The upper surface of the composite sintered compact of each Example and each Comparative Example after re-polishing was observed. The observation results were evaluated in accordance with the evaluation criteria above.
Next, the change in aesthetic appearance before and after re-polishing was evaluated in accordance with the following evaluation criteria. The evaluation results are presented in Table 1.
The composite sintered compacts of Examples 1 to 4 and Comparative Example 1 were cut in the thickness direction, and the cross-sections were polished.
Next, elemental analysis was performed on the polished cross-sections to determine the diffusion-bonding widths of Cu and Mo. The obtained diffusion-bonding widths were evaluated in accordance with the following evaluation criteria. The evaluation results are presented in Table 1.
As presented in Table 1, the composite sintered compact of each Example had a good aesthetic appearance before re-polishing. In particular, it was recognized that a difference in hue due to the difference in steel species was formed in a smooth surface, resulting in a unique and high design quality. Further, no change in the aesthetic appearance before and after re-polishing was observed. Furthermore, in the composite sintered compacts of Examples 1 to 4, it was found that satisfactory diffusion-bonding occurred at the interface between the first portion and the second portion.
Meanwhile, in the composite sintered compacts of Comparative Examples 1 and 2, a large step occurred at the interface. This is considered to be because there was a large difference in the shrinkage starting temperatures between the powders.
Furthermore, in the composite sintered compact of Comparative Example 3, the difference between the light reflectance of the first surface during polishing and the light reflectance of the second surface during polishing was small.
Further, in the composite sintered compact of Comparative Example 4, the concavities and convexities disappeared due to re-polishing. Therefore, it was found that the composite sintered compact of Comparative Example 4 cannot accommodate re-polishing, that is, does not have suitability for re-polishing.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-018978 | Feb 2023 | JP | national |
