JP2001181857A - Method for hardening edge and mowing edge produced by the same method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for hardening an edge by forming a cemented carbide layer excellent in adhesion on an edge and to provide a mowing edge produced by the same method. SOLUTION: Cemented carbide particles are fed to a jet flow obtained by exploding and burning fuel and compressed air, and the cemented carbide particles carried by the jet flow are applied to an edge at a supersonic speed, preferably, at 900 to 1,200 m/sec, by which a cemented carbide layer excellent in adhesion is formed on the edge. By the use of a mowing edge obtained in this way, the exchanging time of the edge is reduced, and mowing operation can continuously be executed for a long time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for hardening a cutting edge, and more particularly, to a method for cutting cemented carbide particles at a supersonic speed using an injection flow obtained by explosively burning fuel and compressed air. And a method for curing a cutting edge characterized by irradiating the edge. Further, the present invention relates to a long-lasting lawn mowing blade manufactured by the curing method.

[0002]

2. Description of the Related Art Hitherto, wear resistance has been improved by providing a hard layer of ceramics, cemented carbide or the like on the cutting edge of a tool for mowing grass or lawn. For example,
There is a method of forming a cemented carbide layer on the cutting edge of a tool by plasma spraying. However, this method has a problem that the base material is exposed to high-temperature plasma, so that the base material is softened during thermal spraying, and mechanical properties such as hardness required for the tool base material are reduced. In addition, high temperature plasma causes WC
There was also a problem that the particles were oxidized / decomposed.

Further, since the lawn mowing blade is used under severe conditions that may bite sand or pebbles, strong adhesion between the cemented carbide layer and the substrate is required. However, the conventional method does not always provide sufficient adhesion. This is because the density of the cemented carbide layer formed by plasma spraying is low, and the velocity of the cemented carbide particles when sprayed onto the substrate (spraying speed) is low. It is said that one of the causes is that the energy is small and a sufficient bonding force cannot be obtained between the cemented carbide particles or between the cemented carbide particles and the substrate.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and its object is to
Provide a method of hardening the cutting edge that can provide a sufficient bonding force between the cemented carbide particles or between the cemented carbide particles and the base material without causing the softening of the base material when forming the cemented carbide layer on the cutting edge In particular, it is an object of the present invention to provide a method of hardening a cutting edge which is suitable for improving the performance of a tool for mowing grass and lawn and extending the life.

[0005]

That is, according to the present invention, there is provided a method of hardening a cutting edge, in which a base material having a cutting edge is prepared, and cemented carbide particles are supplied to an injection stream obtained by explosively burning fuel and compressed air. In addition, it is characterized in that the blade is irradiated with the cemented carbide particles conveyed by the jet flow at supersonic speed. still,
It is particularly preferable to irradiate the hard metal particles to the cutting edge at 900 to 1200 m / s. Since the cemented carbide particles accelerated to supersonic speed by the jet flow have a large kinetic energy, the kinetic energy is converted into thermal energy when colliding with the base material, and as a result, the cemented carbide particles or each other A sufficient bonding force is obtained between the hard alloy particles and the base material.
Further, by using the jet flow formed by the explosive combustion, it is possible to form a hard cemented carbide layer while preventing oxidation of the WC particles.

In the method for hardening a cutting edge of the present invention, the temperature at which the cemented carbide particles of the cutting edge reach the cutting edge is 1000 to
Preferably it is 1300 ° C. In this case, the surface wettability of the cemented carbide particles is improved, and the cemented carbide particles do not deteriorate, so that a denser and higher quality cemented carbide layer can be formed on the cutting edge.

In the method for hardening a cutting edge of the present invention, the thickness of the cemented carbide layer formed on the cutting edge is preferably 20 to 100 μm. If the thickness is in this region, excellent wear resistance can be provided, and a cemented carbide layer excellent in chipping resistance can be provided.

[0008] In the cutting edge hardening method of the present invention, the surface of the cutting edge irradiated with the cemented carbide particles preferably has irregularities of 5 µm or more. In this case, an even better adhesion of the cemented carbide layer can be achieved by the anchor effect of the substrate surface having irregularities mechanically holding the cemented carbide layer.

It is a further object of the present invention to supply cemented carbide particles to an injection stream obtained by explosively burning fuel and compressed air, and to cause the cemented carbide particles carried by the injection stream to be supersonic at a cutting edge. An object of the present invention is to provide a lawn mowing blade having a cemented carbide layer formed by irradiation, and in particular, to provide a lawn mowing blade characterized by the following configuration. As shown in FIG. 2A, the lawn mowing blade 4 has a rake face 41, a flank face 42, and a cutting edge 43 between them. On the rake face 41 of the lawn mowing blade, a region of 5 mm to 50 mm in a direction away from the cutting edge 43 is a region where a cemented carbide layer is not formed, that is, a region 4 where a cemented carbide layer is not formed.
5 The unformed area 4 on the rake face 41
The region adjacent to 5 is a region where a cemented carbide layer is formed, that is, a region 46 where a cemented carbide layer is formed. By supplying cemented carbide particles to the jet stream obtained by explosive combustion of fuel and compressed air, and by irradiating the cemented carbide particles carried by the jet stream to the formation region 46 and the flank 42 at supersonic speed, Cemented carbide layer 5 is formed. FIG. 2B is a schematic diagram showing a damaged (worn) state after the lawn mowing operation has been performed for a predetermined time using the lawn mowing blade. The unformed region 45 of the cemented carbide layer is worn, but the cutting edge 43 is kept sharp. Further, it can be seen that the progress of abrasion in the unformed region 45 is suppressed by the cemented carbide layer 5 on the formed region 46.

It is also preferable to provide a lawn mowing blade having the following features. As shown in FIG. 3, the mowing blade includes a rake face 61, a flank face 62, a movable blade 6 having a cutting edge 63 therebetween, and a fixed blade 7 having a cutting edge 73 at a corner portion. On the rake face 61 of the movable blade 6, the cemented carbide layer 5 is formed over a predetermined region in a direction away from the cutting edge 63. On the other hand, the side surface 71 of the fixed blade 7
Above, the cemented carbide layer 5 is formed over a predetermined region in a direction away from the cutting edge 73. The cemented carbide layer 5 supplies cemented carbide particles to the jet stream obtained by explosive combustion of fuel and compressed air, and super-sonically moves the cemented carbide particles carried by the jet stream between the movable blade and the fixed blade. It is formed by irradiating a predetermined area.

[0011]

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be described in more detail with reference to the accompanying drawings.

FIG. 1 is a schematic view of an apparatus used in the method for hardening a cutting edge according to the present invention. The apparatus includes a combustion vessel 10 that provides a combustion chamber 1 and a nozzle 20 connected to the vessel 10 for irradiating the jet flow generated in the combustion chamber to the outside. The container 10 is an ignition device for igniting a fuel gas.
(Not shown), and a fuel supply port 12 provided on the side facing the nozzle 20. The nozzle 20 is provided with a compressed air supply port 21 and a supply port 22 for cemented carbide powder. A compressed air supply line 30 for sending compressed air to the fuel supply port 12 is connected to the fuel supply port 12 from the compressed air supply port 21 through the nozzle 20 and the inside of the wall of the container 10 as shown in FIG. Is extended.

In the combustion chamber 1, compressed air and fuel are mixed, ignited, and explosively burned. The jet 2 generated by the explosive combustion is jetted from the nozzle 20. At this time, the cemented carbide powder is supplied through the supply port 22. The particle size of the cemented carbide particles is preferably 15 to 60 μm. Jet 2
Gives a large kinetic energy to the injected cemented carbide powder. Upon collision with the substrate 3, this kinetic energy is converted into thermal energy, which is used to achieve a high bonding force between the cemented carbide particles or between the cemented carbide particles and the substrate. Hereinafter, Examples 1 to 7 and Comparative Examples 1 to 4 based on the present invention will be described.

Example 1 Using the apparatus shown in FIG. 1, a cemented carbide layer was formed on the cutting edges of a movable blade and a fixed blade of a lawn mowing tool. The composition of the cemented carbide particles supplied through the supply port 22 is WC-12% Co, and the particle size is 15 to 45%.
μm. The jet flow containing cemented carbide particles is 1000 m
Irradiation at a supersonic speed of / sec. The thickness of the obtained cemented carbide layer was 50 ± 5 μm. After preparing 10 mowing tools equipped with the movable blade and the fixed blade manufactured by this method, and performing mowing work of a predetermined area three times for each,
We evaluated whether we could cut a postcard. As a result, postcards could be cut in all ten pieces.
Further, no peeling of the cemented carbide layer was observed after the test.

Example 2 Using the apparatus shown in FIG. 1, a cemented carbide layer was formed on the cutting edges of a movable blade and a fixed blade of a lawn mowing tool. The composition of the cemented carbide particles supplied through the supply port 22 is WC-17% Co, and the particle size is 15 to 60%.
μm. The jet flow containing cemented carbide particles is 1000 m
Irradiation at a supersonic speed of / sec. The thickness of the obtained cemented carbide layer was 40 ± 10 μm. Prepare 10 lawn mowing tools equipped with movable blades and fixed blades manufactured by this method,
After performing lawn mowing work three times for each of them, it was evaluated whether the postcard could be cut. As a result, postcards could be cut in all ten pieces. Further, no peeling of the cemented carbide layer was observed after the test.

Example 3 Using the apparatus shown in FIG. 1, a cemented carbide layer was formed on the cutting edges of a movable blade and a fixed blade of a lawn mowing tool. The composition of the cemented carbide particles supplied through the supply port 22 is WC-12% Co, and the particle size is 15 to 45%.
μm. The jet containing cemented carbide particles is 800 m /
Irradiated at supersonic speeds of seconds. The temperature at the time of collision with the substrate is 1
200 ° C. The unevenness of the surface of the blade to be irradiated was 5 μm or more. The thickness of the obtained cemented carbide layer was 50 ± 5 μm. Prepare 100 lawn mowing tools equipped with movable blades and fixed blades manufactured by this method,
After performing lawn mowing work three times for each of them, it was evaluated whether the postcard could be cut. As a result, fine peeling of the cemented carbide layer was observed in two pieces, but postcards could be cut for the remaining 98 pieces.

Example 4 Using the apparatus shown in FIG. 1, a cemented carbide layer was formed on the cutting edges of a movable blade and a fixed blade of a lawn mowing tool. The composition of the cemented carbide particles supplied through the supply port 22 is WC-17% Co, and the particle size is 15 to 60%.
μm. The jet containing cemented carbide particles is 1200m
Irradiation at a supersonic speed of / sec. The temperature at the time of collision with the substrate is
1000 ° C. The unevenness of the surface of the blade to be irradiated was 5 μm or more. The thickness of the obtained cemented carbide layer was 40 ± 10 μm. 100 lawn mowing tools equipped with a movable blade and a fixed blade manufactured by this method were prepared, and after performing lawn mowing work of a predetermined area three times for each of them, it was evaluated whether a postcard could be cut.
As a result, postcards could be cut in all 100 pieces. Further, no peeling of the cemented carbide layer was observed after the test.

Example 5 Using the apparatus shown in FIG. 1, a cemented carbide layer was formed on a lawn mowing blade. As shown in FIG. 2 (a), the area where the cemented carbide layer was formed in the present embodiment was formed on the rake face 41 of the lawn mowing blade in an area 4mm between the cutting edge and 10 mm.
5, the cemented carbide layer 5 was not formed, but in the region 46 further away from the cutting edge, the cemented carbide layer 5 was formed over a predetermined distance. In the flank 42 of the mowing blade, the cemented carbide layer 5 extends over the length of the flank from the cutting edge.
Was formed. The composition of the cemented carbide particles supplied through the supply port 22 is WC-25% Co, and the particle size is 20%.
〜60 μm. The jet stream containing the cemented carbide particles is 95
Irradiation was performed at a supersonic speed of 0 m / sec. The thickness of the formed hard metal layer was 40 ± 10 μm. Ten lawn mowing blades manufactured by this method were prepared, and after performing lawn mowing work of a predetermined area twice with each lawn mowing blade, it was evaluated whether a postcard could be cut. As a result, postcards could be cut in all ten pieces. Further, no peeling of the cemented carbide layer was observed after the test.

On the rake face 41 of the lawn mowing blade,
Substantially the same as above except that the cemented carbide layer 5 was not formed in the region 45 between 100 mm from the cutting edge, and the cemented carbide layer 5 was formed over a predetermined distance in the region 46 further away from the cutting edge. Then, a cemented carbide layer was formed on the lawn mowing blade. Ten lawn mowing blades manufactured by this method were prepared, and after performing lawn mowing work of a predetermined area once with each lawn mowing blade, it was evaluated whether a postcard could be cut. As a result, postcards could be cut in four pieces, but postcards could not be cut in the remaining six pieces. This result indicates that when the method for hardening the cutting edge of the present invention is applied to a lawn mowing blade as shown in FIG. 2 (a), if the region where the cemented carbide layer is to be formed is not properly selected, the cemented carbide layer is not This indicates that the performance cannot be fully exhibited.

Example 6 A cemented carbide layer was formed on the inner and outer blades of an electric razor using the apparatus shown in FIG.
The composition of the cemented carbide particles supplied through the supply port 22 is as follows:
WC-25% Co, and its particle size is 15 to 60 μm. The jet containing the cemented carbide particles was irradiated at a supersonic speed of 900 m / sec. The temperature at the time of collision with the substrate is 950 ° C.
Met. The thickness of the formed cemented carbide layer is 40 ± 10
μm. One hundred electric razors equipped with an inner blade and an outer blade manufactured by this method were prepared, and after shaving the beard equivalent to two years of an average adult male with each, it was evaluated whether the fishing line could be cut. As a result, 99 fishing lines could be cut. At this time, fine peeling of the cemented carbide layer was observed in two pieces.

(Embodiment 7) Using the apparatus shown in FIG. 1, a cemented carbide layer was formed on the cutting edge of the inner blade and the outer blade of the electric razor.
The composition of the cemented carbide particles supplied through the supply port 22 is as follows:
WC-12% Co, and its particle size is 15 to 60 μm. The jet containing the cemented carbide particles was irradiated at a supersonic speed of 900 m / sec. The temperature at the time of collision of the jet with the substrate is
It was 1200 ° C. The thickness of the formed cemented carbide layer is
70 ± 10 μm. One hundred electric razors equipped with an inner blade and an outer blade manufactured by this method were prepared, and after shaving the beard equivalent to two years of an average adult male with each, it was evaluated whether the fishing line could be cut. as a result,
The fishing line could be cut in all 100 pieces. At this time, no delamination was observed in the cemented carbide layer.

(Comparative Example 1) Ten lawn mowing tools equipped with the same movable blade and fixed blade as those used in Example 1 except that the cemented carbide layer was not provided on the cutting edge were prepared. After performing a lawn mowing operation once for a predetermined area, it was evaluated whether a postcard could be cut. As a result, postcards could be cut for two pieces, but postcards could not be cut for the remaining eight pieces. As described above, the blade edge deteriorated in one lawn mowing operation.

Comparative Example 2 Using the apparatus shown in FIG. 1, a cemented carbide layer was formed by plasma spraying on the cutting edges of a movable blade and a fixed blade of a lawn mowing tool. The composition of the cemented carbide particles used is WC-12% Co, and the particle size is 20-50 μm.
m. The thickness of the formed cemented carbide layer is 70 ± 10
μm. Ten lawn mowing tools equipped with a movable blade and a fixed blade manufactured by this method were prepared, and after performing a lawn mowing operation of a predetermined area once for each of them, it was evaluated whether a postcard could be cut. As a result, postcards could be cut for five pieces, but postcards could not be cut for the remaining five pieces. in this way,
Degradation of the cutting edge was progressing in one lawn mowing operation.

Comparative Example 3 Using the apparatus shown in FIG. 1, a cemented carbide layer was formed by plasma spraying on the cutting edges of a movable blade and a fixed blade of a lawn mowing tool. The composition of the cemented carbide particles used is WC-12% Co, and the particle size is 20-50 μm.
m. The thickness of the formed cemented carbide layer is 70 ± 10
μm. 100 lawn mowing tools equipped with a movable blade and a fixed blade manufactured by this method were prepared, and after each lawn mowing operation of a predetermined area was performed once, it was evaluated whether a postcard could be cut. As a result, postcards could be cut for 12 pieces, but postcards could not be cut for the remaining 88 pieces. In addition, 1
The peeling of the cemented carbide layer was observed in 81 times in the lawn mowing operation.

Comparative Example 4 Using the apparatus shown in FIG. 1, a cemented carbide layer was formed on the cutting edges of the movable blade and the fixed blade of a lawn mowing tool. The composition of the cemented carbide particles supplied through the supply port 22 is WC-17% Co, and the particle size is 15 to 60%.
μm. The jet stream containing the cemented carbide particles was irradiated at a low speed of 300 m / sec or less, which was lower than the speed of sound. The thickness of the formed hard metal layer was 40 ± 10 μm. A lawn mowing tool equipped with a movable blade and a fixed blade manufactured by this method is 100
Individual pieces were prepared, and after each lawn mowing operation of a predetermined area was performed, it was evaluated whether a postcard could be cut. As a result, 14 postcards could be cut, but the remaining 86 postcards could not be cut. In addition, peeling of the cemented carbide layer was observed in 90 pieces in one lawn mowing operation.

[0026]

Since the lawn mowing blade is used under severe conditions that may bite sand or pebbles, it is an issue to extend the tool life. In the present invention, by irradiating the cemented carbide particles to the cutting edge at supersonic speed, a high adhesion force is provided between the cemented carbide particles or between the cemented carbide particles and the base material, and the blade adheres to the cutting edge of the lawn mowing blade. Since a cemented carbide layer with excellent properties can be formed, the number of blade replacements can be reduced and lawn mowing can be continued for a long time.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a supersonic flame spraying apparatus used in a method for hardening a cutting edge according to the present invention.

2A is a partial cross-sectional view of a lawn mowing blade according to the present invention, and FIG. 2B is a partial cross-sectional view showing a damaged state after lawn mowing work using the lawn mowing blade of FIG. It is.

FIG. 3 is a partial sectional view of another mowing blade according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Combustion chamber 2 Injection flow 3 Substrate 10 Combustion container 12 Fuel supply port 20 Nozzle 21 Compressed air supply port 22 Supply port of cemented carbide particles 30 Compressed air supply line

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor, Tadashi Hamada 1048, Kazuma, Kadoma, Osaka Pref. F-term in Matsushita Electric Works, Ltd. (reference)

Claims (7)

[Claims] 1. A base material having a cutting edge is prepared, and cemented carbide particles are supplied to a jet flow obtained by explosively burning fuel and compressed air, and the cemented carbide particles conveyed by the jet flow are super-cooled. A method of hardening a cutting edge, wherein the cutting edge is irradiated at a sonic speed. 2. The method according to claim 1, wherein the cemented carbide particles are 900 to 1200.
2. Irradiating the cutting edge at m / s.
The curing method described in 1. 3. The method according to claim 1, wherein the temperature at which the cemented carbide particles reach the cutting edge is 1000 to 1300 ° C. 4. The cemented carbide layer formed on the cutting edge has a thickness of 20 to 100 μm.
The curing method described in 1. 5. The hardening method according to claim 1, wherein the surface of the cutting edge irradiated with the cemented carbide particles has irregularities of 5 μm or more. 6. A method in which cemented carbide particles are supplied to an injection stream obtained by explosive combustion of fuel and compressed air, and the cemented carbide particles conveyed by the injection stream are irradiated at a supersonic speed to a cutting edge. A mowing blade characterized by including a cemented carbide layer formed thereon. 7. A lawn mowing blade having a rake face, a flank, and a cutting edge therebetween, wherein an area of 5 mm to 50 mm in a direction away from the cutting edge on the rake face is not formed with a cemented carbide layer. Region, and a region adjacent to the unformed region on the rake face is defined as a region for forming a cemented carbide layer. Accordingly, the cemented carbide layer is super-cooled to an injection flow obtained by explosively burning fuel and compressed air. A lawn mowing blade formed by supplying hard alloy particles and irradiating cemented carbide particles conveyed by the jet stream to the formation area and the flank at a supersonic speed.