Patent Application
20240190029
The present disclosure relates to a cutting implement having excellent wear resistance.
Traditionally, kitchen knives made of a material that contains a metal material as a main component have been used. Among these, in recent years, a kitchen knife made of stainless steel that contains nickel and chromium as components has been widely used. Patent Document 1 describes that titanium carbide particles and stainless steel particles having a high hardness are deposited on a leading end portion of a blade body made of stainless steel, and are simultaneously irradiated with a laser beam to be bonded to the blade body to form a bead, and the bead is ground and polished to make a cutting implement.
In the present disclosure, a cutting implement includes a blade body that includes a base portion and a cutting edge portion connected to an end portion of the base portion. The base portion includes a first metal, and the cutting edge portion includes a second metal and hard particles having a hardness higher than the hardness of the second metal. The hard particles include first hard particles having a particle size of 20 μm or more and 50 μm or less and having an angular polyhedral shape.
In the present disclosure, another cutting implement includes a blade body that
includes a base portion and a cutting edge portion connected to an end portion of the base portion. The base portion includes a first metal, and the cutting edge portion includes a second metal and hard particles having a hardness higher than the hardness of the second metal. An interface portion having a crystal grain size larger than the crystal grain size of the cutting edge portion is provided between the base portion and the cutting edge portion.
Hereinafter, a cutting implement according to an embodiment of the present disclosure will be described. Drawings used in the following description are schematic, and dimensional ratios and the like on the drawings do not always match the actual ones.
As illustrated in
The handle 1b connected to the blade body 1a is to be gripped by a hand when a person uses the cutting implement 1. As in the case of the blade body 1a, the shape and size of the handle 1b are set in accordance with the application of the cutting implement 1.
The blade body 1a and the handle 1b may be formed integrally or separately. The cutting implement 1 is not limited to including the handle 1b, and may be composed of only the blade body 1a. In the present embodiment, the blade body 1a and the handle 1b are separately formed. The blade body 1a is partially inserted into the handle 1b, and is fixed to the handle 1b at the insertion portion. A part of the blade body 1a may be welded to the handle 1b made of metal.
The handle 1b includes wood, resin, ceramic, or a metal material. As the metal material, a rust-resistant material such as a titanium-based or stainless-steel-based material may be used. As the resin, for example, an ABS resin (a copolymer of acrylonitrile, butadiene, and styrene) or a polypropylene resin may be used.
The blade body 1a includes a base portion 3 and a cutting edge portion 2 connected to the base portion 3. The base portion 3 includes a first metal. As the first metal, for example, steel, synthetic steel, stainless steel, titanium alloy, or the like may be used. As the synthetic steel, for example, a material including chromium, molybdenum, vanadium, tungsten, cobalt, copper, combinations thereof, or the like may be used. As the stainless steel, chromium-nickel-based stainless steel or chromium-based stainless steel may be used. As the titanium alloy, for example, so-called 64 titanium, which is a titanium alloy including 6% of aluminum (Al) and 4% of vanadium (V), may be used. When the first metal is stainless steel, the corrosion resistance of the base portion 3 against rust or the like can be improved.
In the present embodiment, the first metal is a main component of the base portion 3. Here, a “main component” means a component that accounts for 70 mass % or more of the total of 100 mass % of the components constituting the base portion 3.
As illustrated in
As illustrated in
When made of Inconel, the second metal 2a has a relatively high corrosion resistance, and can reduce thermal stress remaining in the cutting edge portion 2 when a laser is used in the manufacturing method.
When made of Ni-based Colmonoy, the second metal 2a can suppress strength deterioration due to hardening and annealing of the cutting edge during manufacture of the cutting implement 1. The Ni-based Colmonoy is preferably composed of 0.06 mass % or less of carbon, 0.8 mass % or less of iron, 2.4 to 3.0 mass % of silicon, 1.6 to 2.00 mass % of boron, 0.08 mass % or less of oxygen, and the balance of nickel with respect to the total amount of the Ni-based Colmonoy.
In the present embodiment, the second metal 2a forms a metallic matrix as a main component of the cutting edge portion 2, and the hard particles are present in this matrix. Here, a “main component” means a component that accounts for 50 mass % or more of the total of 100 mass % of the components constituting the cutting edge portion 2. Since the second metal 2a is the main component of the cutting edge portion 2, the durability of the cutting edge portion 2 can be further improved.
The plurality of hard particles 4 included in the cutting edge portion 2 have a higher Vickers hardness than the Vickers hardness of the second metal 2a included in the cutting edge portion 2. Thus, the hardness of the entire cutting edge portion 2 can be increased, and the wear resistance of the cutting edge portion 2 can be improved. Since the hard particles 4 are made of a material harder than the second metal 2a, the sharpness of the cutting edge portion 2 against an object is improved by the hard particles 4 coming into contact with the object during the use of the cutting implement 1.
In the present embodiment, the hard particles 4 are made of a material that is harder than the second metal 2a and also harder than the first metal. As described above, by using the hard particles 4 having a sufficient hardness, an effect of improving the sharpness and the wear resistance of the cutting edge portion 2 can be enhanced. The hard particles 4 may have, for example, a Vickers hardness of 1000 Hv or more and 4000 Hv or less. The Vickers hardnesses of the hard particles 4, the first metal, and the second metal 2a can be measured using a method according to JIS Z 2244 (ISO 6507-2, the same applies hereinafter).
The hard particles 4 are preferably exposed on a surface of the cutting edge portion 2. In order for the hard particles 4 to be easily exposed on a surface of the cutting edge portion 2 even when the cutting edge portion 2 is polished, the hard particles 4 are preferably dispersed not only in a length direction (x-axis direction) and a width direction (y-axis direction) of the base portion 3 but also in a thickness direction (z-axis direction) of the base portion 3 inside the cutting edge portion 2.
Examples of the hard particles 4 include a cemented carbide alloy including tungsten carbide (WC), and a cermet including titanium carbide (TiC), titanium nitride (TiN), tantalum carbide (TaC), and vanadium carbide (VC). As the hard particles 4, a plurality of materials such as tungsten carbide, titanium carbide, and the like may be mixed and used.
The hard particles 4 preferably include first hard particles 41 having an angular polyhedral shape (see
Preferably, the first hard particles 41 having an angular polyhedral shape and a particle size of 20 μm or more and 50 μm or less are included in the matrix of the second metal 2a at an area ratio of 3% or more in cross section. The first hard particles 41 having such a relatively large particle size are susceptible to cracking. However, in the present disclosure, since the first hard particles 41 are present in the matrix of the second metal 2a, the growth of cracks can be suppressed by the matrix, and thus the hard particles 4 having a relatively large particle size can be used. Here, when the particle size of the first hard particles 41 is 20 μm or more, the wear resistance is improved. On the other hand, when the particle size is 50 μm or less, the occurrence of cracks in the first hard particles 41 can be suppressed. In order to set the particle size of the first hard particles 41 as described above, for example, particles having a particle size of less than 20 μm and particles having a particle size of more than 50 μm may be screened out by using a sieve.
Note that the percentage of particles at an area ratio in a cross section is measured by calculating a region of hard particles by using the software “Image J”.
As described above, the hard particles 4 preferably include particles (first hard particles 41) having a particle size (average particle size, the same applies hereinafter) of 20 μm or more and 50 μm or less. When the hard particles 4 include particles having a particle size of 20 μm or more, the wear resistance is improved. On the other hand, when the hard particles 4 include particles having a particle size of 50 μm or less, the occurrence of cracks in the hard particles 4 can be suppressed.
The hard particles 4 may include particles (second hard particles 42 to be described later) having a particle size of 2 μm or more and 10 μm or less. When such fine hard particles 42 are dispersed in the cutting edge portion, the strength of the cutting edge portion is improved and the wear resistance is also improved.
The hard particles 4 may include particles (third hard particles 43 to be described later) crystallized in a dendritic shape from the matrix of the second metal 2a. The anchor effect of such dendritic particles can suppress degranulation of the hard particles 43.
The hard particles 4 may be included in the cutting edge portion 2 in an amount of 10 mass % or more. In that case, the hard particles 4 having a particle size outside of the range of 20 μm or more and 50 μm or less may be included, but the hard particles 4 having a particle size of 20 μm or more and 50 μm or less are preferably included at an area ratio of 3% or more in a cross section as described above. Accordingly, the sharpness and the wear resistance of the cutting edge portion 2 can be further improved. The hard particles 4 may be included in the cutting edge portion 2 in an amount of 50 mass % or less. In that case, the productivity of the cutting edge portion 2 can be maintained at a high level. At this time, the content of the hard particles 4 having a particle size of 20 μm or more and 50 μm or less is preferably 32% or less as an area ratio in cross section.
Note that the content of the hard particles 4 can be obtained by observing a cross section (a cross section parallel to a yz plane) of the cutting edge portion 2 using an SEM and calculating a ratio of a total area of the hard particles 4 to an area of the entire cutting edge portion 2 as area percentage based on a photograph of the observed image.
A cross section of the blade body 1a (a cross section parallel to a yz plane) will be described with reference to
In the present embodiment, at least one of the hard particles 4 is preferably exposed from the cutting edge 2A. Accordingly, when an object is cut by using the cutting implement 1, the hard particles 4 exposed from the cutting edge 2A come into contact with the object, and the sharpness of the cutting edge 2A can be improved.
A method for manufacturing the cutting implement 1 will be described with reference to
First, the base portion 3 including the first metal is prepared. The base portion 3 has a shape as illustrated in
On the other hand, separately from the preparation of the base portion 3, metal powder constituting the second metal and raw material powder forming the hard particles 4 are prepared.
As illustrated in
The metal powder 2a1 is preferably melted and baked by laser. That is, a cladding technique using laser is preferably used. Specifically, as illustrated in
As illustrated in
When the powder-particle mixture 5 is irradiated with the laser beam 7, the powder-particle mixture 5 excluding the hard particles 4 is melted and adheres to the end portion 3C. On the other hand, the hard particles 4 have a high melting point, and thus are not likely to be melted by the laser beam 7. Therefore, when the powder-particle mixture 5 is melted, the build-up portion 6 in which the plurality of hard particles 4 are dispersed can be obtained at the cutting edge portion 2. As will be described later, the hard particles 4 are partially solid-dissolved into the matrix during a build-up process, and the hard particles 4 are crystallized from the matrix, which has become a supersaturated solid solution.
The cutting edge portion 2 is formed on the end portion 3C of the base portion 3 by polishing a part of the build-up portion 6. Only the build-up portion 6 may be polished, or a part of the base portion 3 may be polished in addition to the build-up portion 6. Polishing can be performed by using a polishing stone having a surface coated with, for example, aluminum oxide (Al2O3), silicon carbide (SiC) or diamond, mixed particles of silicon carbide (SiC) or diamond. Polishing may be performed in a plurality of steps.
In
The first hard particles 41 have a particle size of 20 μm or more and 50 μm or less, and have an angular polyhedral shape. The first hard particles 41 retain the shape of the raw material powder of the hard particles (WC) to some extent. The presence of the first hard particles 41 being coarse in size as described above improves the wear resistance of the cutting edge portion 2.
As illustrated in
The first hard particles 41 are formed in such a manner that the hard particles 4 having a raw material powder size are not melted while being processed and are present as is in the build-up portion.
The second hard particles 42 are fine hard particles having a particle size of 2 μm or more and 3 μm or less. When the second hard particles 42 which are fine in size as described above, are dispersed in the matrix of the second metal 2a, the strength of the cutting edge portion 2 is improved and the wear resistance is improved. The second hard particles 42 are assumed to have been obtained in such a manner that the raw material powder is ground to be fine and dispersed. The second hard particles 42 are formed by grinding hard particles having a raw material powder size while being processed.
The third hard particles 43 are illustrated in
In the present embodiment, the first, second, and third hard particles 41, 42, and 43 are present in the build-up portion 6. This is presumed because the raw material powder of the hard particles 4 has a relatively large particle size, the hard particles are likely to be ground, and the energy during the processing locally has enough power to melt the hard particles. Not all the three types of hard particles 41, 42, and 43 need to be present in one build-up portion 6, but at least one type out of the hard particles 41, 42, and 43 needs to be present.
As is apparent from
It is assumed that the crystal grains are coarsened in the interface portion 8 as described above because the base portion 3 is heated by the irradiation of the laser beam 7, and thus the cooling rate becomes lower toward the vicinity of the boundary between the base portion 3 and the build-up portion 6 than in the interior of the build-up portion 6 after the build-up process. A length L of the interface portion 8 is preferably about 10 μm or more and 200 μm or less with respect to the entire length of the build-up portion 6.
It can be seen from Table 1 that, in the region (2) of the interface portion 8, iron (Fe) mainly dispersed from the base portion 3 forms a Ni—Fe alloy phase.
In the present embodiment, preferably, after the build-up portion 6 is formed by the laser beam 7, heat treatment such as annealing of the cutting edge, which is performed in a normal manufacturing process for a cutting tool, is not performed, or a mild heat treatment is performed. This is because the interface portion 8 may disappear, resulting in a uniform structure, and the hardness in the interface portion 8 to be described later may not decrease. Therefore, the heat treatment such as annealing is preferably performed before the build-up portion 6 is formed by the laser beam 7.
As illustrated in
The measurement result of the Vickers hardness distribution is illustrated in
Since the hardness of the interface portion 8 is low as described above, the toughness of the boundary region between the cutting edge portion and the base portion 3 in the cutting implement 1 is high. As a result, when the cutting implement 1 is used or the like, the interface portion 8 serves as a so-called buffer against an impact applied to the cutting implement 1, and thus cracking or breakage of the cutting edge portion 2 can be reduced, which is advantageous in increasing the life of the cutting implement 1. In order to achieve such an effect, the Vickers hardness of the interface portion 8 is suitably 400 HV or more and 450 HV or less.
As illustrated in
As illustrated in
The embodiment of the present disclosure has been described above, but the cutting implement according to the present disclosure is not limited thereto, and various changes and improvements can be made within the range set forth in the present disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-062090 | Mar 2021 | JP | national |
| 2021-062091 | Mar 2021 | JP | national |
| 2021-062092 | Mar 2021 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2022/015188 | 3/28/2022 | WO |
