JP7765275B2 - Cutting blade, glass fiber cutting device, glass fiber manufacturing method, and cutting blade manufacturing method - Google Patents

Description

The present invention relates to a technology for cutting glass fibers to a predetermined length.

A glass fiber cutting device is equipped with a cutting roll equipped with multiple cutting blades and a rubber contact roll placed opposite it. By continuously supplying long glass fibers between the cutting roll and the contact roll, chopped glass fibers (chopped strands) are produced. The chopped glass fibers are used as reinforcing materials in a wide range of fields, including automobiles, electrical and electronic devices, and housing equipment.

For example, Patent Document 1 discloses a cutting blade as described above that includes a cutting portion made of cemented carbide, a base portion made of carbon tool steel, and a joint (alloy layer) that joins the cutting portion and the base portion. The joint is made of a nickel alloy or cobalt alloy.

Such cutting blades have excellent wear resistance because the cutting portion is made of cemented carbide, and excellent impact resistance because the base portion is made of carbon tool steel. Furthermore, because nickel or cobalt is melted into the carbon tool steel and cemented carbide to form an integrated structure, the bonding strength between the cutting portion and the base portion is also high. This allows for long-term use of the cutting blade, and has the advantage of making it less likely to break even if an excessive impact load is applied to the cutting blade.

JP 2008-100348 A

This type of cutting blade is manufactured by placing a bonding material made of nickel or cobalt between the blade and base, then heating the bonding material with a laser to bond the blade and base.

However, depending on the type of laser used (e.g., _CO2 laser), excessive heat may be applied to the joint between the blade and the base, resulting in the problem of cracks occurring at the joint when such cutting blades are used for extended periods of time. Such cracks may cause the cutting blade to break.

The objective of this invention is to reliably prevent cracks from occurring at the joints of the cutting blades.

(1) The present invention, which was invented to solve the above problems, provides a cutting blade comprising a cutting portion containing cemented carbide, a base portion containing carbon tool steel, and a joint portion bonding the cutting portion and the base portion and containing nickel or cobalt, wherein the joint portion has a dendritic layer, and in any orthogonal cross section of the joint portion relative to the longitudinal direction of the cutting blade, there are no more than two voids with a circle-equivalent diameter of 50 μm or more per ^mm2 . Here, the "orthogonal cross section of the joint portion" includes the interface between the joint portion and the cutting portion and the interface between the joint portion and the base portion. The "circle-equivalent diameter" refers to the diameter of a circle having an area equal to the area of the void. The "any orthogonal cross section" refers to a single orthogonal cross section randomly selected relative to the longitudinal direction of the cutting blade.

In this way, the anchoring effect of the dendrite layer increases the bond strength between the cutting edge and the base. It also reduces the number of large voids (cavity defects) in the bonded area. This effectively prevents cracks from forming in the bonded area due to voids.

(2) In the configuration of (1) above, it is preferable that the dendrite layer is formed over the entire thickness of the cutting blade.

This will further improve the bond strength between the blade and base.

(3) In the configuration of (1) or (2) above, it is preferable that the number of voids contained in the dendrite layer in an orthogonal cross section of the joint is 10 or less.

This will ensure that the dendrite layer will more reliably improve the bonding strength.

(4) In any of the above configurations (1) to (3), it is preferable that the number of voids having a circle-equivalent diameter of 20 μm or more is four or less per 1 mm ² in the orthogonal cross section of the joint.

This reduces the number of small voids in the joint, making it less likely that cracks will occur starting from voids.

(5) In any of the above configurations (1) to (4), it is preferable that the number of voids having a circle equivalent diameter of 10 μm or more at the interface between the joint and the cutting edge in the orthogonal cross section of the joint is 3 or less per 0.1 ^mm2 .

Generally, cracks are particularly likely to occur at the interface between the joint and the blade portion, but with the above-described configuration, the number of very small voids at the interface between the joint and the blade portion is reduced, making cracks less likely to occur at the interface between the joint and the blade portion.

(6) In any of the configurations (1) to (5) above, the number of voids with a circle-equivalent diameter of 50 μm or more contained in an orthogonal cross section of the joint at one longitudinal end of the cutting blade may be greater than the number of voids with a circle-equivalent diameter of 50 μm or more contained in an orthogonal cross section of the joint at the other longitudinal end of the cutting blade, and the thickness of the dendrite layer contained in the joint at one longitudinal end of the cutting blade may be greater than the thickness of the dendrite layer contained in the joint at the other longitudinal end of the cutting blade.

For example, as in the configuration (10) described below, if the scanning speed of the fiber laser at one end of the joining material is slower than the scanning speed of the fiber laser at the other end of the joining material during the joining process, the amount of heat supplied to the one end of the joining material will be relatively greater. As a result, in the manufactured cutting blade, the number of voids with a circular equivalent diameter of 50 μm or more contained in the orthogonal cross section of one end of the joint may be greater than the number of voids with a circular equivalent diameter of 50 μm or more contained in the orthogonal cross section of the other end of the joint. In this case, there is a concern that cracks originating from voids may be more likely to occur at one end of the joint than at the other end of the joint. However, with the above configuration, the thickness of the dendrite layer contained at one end of the joint is greater than the thickness of the dendrite layer contained at the other end of the joint, resulting in a relatively high joining strength at one end of the joint. This maintains a state in which cracks are less likely to occur at the joint.

(7) The present invention, which was invented to solve the above problems, is a glass fiber cutting device that is equipped with a cutting blade having any of the configurations described above in (1) to (6), and is characterized in that the cutting blade cuts the glass fibers to a predetermined length.

This allows for consistent production of chopped strands.

(8) The present invention, which was invented to solve the above problems, is a method for manufacturing glass fibers, characterized by including a cutting step in which glass fibers are cut to a predetermined length using a cutting blade having any of the configurations described above in (1) to (6).

This allows for consistent production of chopped strands.

(9) The present invention, which was invented to solve the above problems, is characterized by comprising a joining preparation step in which a joining material containing nickel or cobalt is placed between a cutting portion containing cemented carbide and a base portion containing carbon tool steel, and a joining step in which, after the joining preparation step, the joining material is heated by irradiating it with a fiber laser to join the cutting portion and the base portion.

By using a fiber laser in this joining process, a dendrite layer is formed at the joint of the manufactured cutting blade, and the number of voids is greatly reduced. This makes it possible to provide a cutting blade that is less susceptible to cracks originating from voids at the joint.

(10) In the configuration of (9) above, in the joining process, it is preferable that the fiber laser be scanned from one end side to the other end side of the material to be joined along the longitudinal direction of the cutting blade, and that the scanning speed of the fiber laser at one end of the material to be joined be slower than the scanning speed of the fiber laser at other portions of the material to be joined, including the other end.

By relatively slowing the scanning speed of the fiber laser at one end of the joining material in this way, the amount of heat supplied from the fiber laser to one end of the joining material becomes relatively large. This amount of heat melts one end of the joining material while simultaneously preheating the other portion of the joining material, including the other end. Therefore, even if the scanning speed of the fiber laser at the other portion of the joining material, including the other end, is relatively fast, the joining material can be sufficiently melted. This allows the blade portion and base portion to be firmly joined while shortening the time required for the joining process.

This invention reliably prevents cracks from occurring at the joints of the cutting blades.

1 is a side view showing a glass fiber cutting device according to an embodiment of the present invention. FIG. 2 is a front view of a cutting blade according to an embodiment of the present invention. 3 is a cross-sectional view taken along line AA in FIG. 2. 1 is an example of an electron microscope image of a cross section of a joint taken along a plane perpendicular to the longitudinal direction of a cutting blade. 1 is an example of an electron microscope image of a cross section of a joint taken along a plane perpendicular to the longitudinal direction of a cutting blade. FIG. 4 is a diagram schematically illustrating a cross section of a joint portion along the longitudinal direction of a cutting blade. FIG. 3 is a flowchart showing a method for manufacturing a cutting blade according to an embodiment of the present invention. 10 is a cross-sectional view showing a joining preparation step included in the manufacturing method of the cutting blade. FIG. 4 is a cross-sectional view showing a joining step included in the manufacturing method of the cutting blade. FIG. FIG. 10 is a front view showing a joining step included in the manufacturing method of the cutting blade.

The following describes an embodiment of the present invention with reference to the drawings. Note that X, Y, and Z in the drawings represent a Cartesian coordinate system.

As shown in Figure 1, the glass fiber cutting device 1 according to this embodiment includes a cutting roll 2 and a contact roll 3 facing it.

The cutting roll 2 has multiple cutting blades 4 arranged radially on its outer circumferential surface. In this embodiment, the multiple cutting blades 4 are arranged at equal intervals in the circumferential direction of the outer circumferential surface of the cutting roll 2.

The contact roll 3 has a rubber layer 5 on its outer surface.

In the cutting process included in the glass fiber manufacturing method according to this embodiment, long glass fibers G are continuously supplied between the cutting roll 2 and contact roll 3 while they are rotating, and glass fibers (chopped strands) S are produced that are cut to a predetermined length (e.g., 1.5 to 12 mm) by the cutting blade 4. The cut glass fibers S are used, for example, in fiber-reinforced thermoplastics (FRTP) and glass fiber-reinforced cement (GRC). Note that while the glass fibers G and S may be monofilaments, in this embodiment they are made by bundling a large number of monofilaments using a sizing agent.

As shown in Figures 2 and 3, the cutting blade 4 comprises a blade portion 6, a base portion 7, and a joint portion 8 that joins the base end 6b of the blade portion 6 and the tip end 7a of the base portion 7.

The thickness (dimension in the Z direction) of the cutting blade 4 is preferably 0.3 to 4.5 mm, and more preferably 0.3 to 1.5 mm. If the cutting blade 4 is too thin, the strength of the cutting blade 4 will decrease, and if the cutting blade 4 is too thick, it will be difficult to shorten the cutting length of the glass fiber G.

The blade portion 6 is formed from a cemented carbide alloy, and the tip 6a is a sharp cutting edge. As the cemented carbide alloy, an extremely hard alloy made by blending and sintering a powder of a metal element carbide and a powder of a metal can be used. The cemented carbide alloy preferably has excellent wear resistance and can be reused by polishing even if worn. Specifically, WC-Co-based, WC-TaC-Co-based, WC-TiC-Co-based, and WC-TiC-TaC-Co-based alloys can be used, and the thermal expansion coefficient of these alloys is 48 to 62 × 10 ^-7 /°C in the temperature range of 25 to 200°C.

The cutting edge 6 can be obtained by blending and sintering 85-95% by mass of tungsten carbide (WC) powder with an average particle size of 0.3-1.0 μm and 5-15% by mass of cobalt (Co) powder, and then forming it into a predetermined shape and size (for example, a dimension of 3-7 mm from the base end 6b to the tip 6a of the cutting edge 6).

The base portion 7 is made of carbon tool steel. Carbon tool steel is made by quenching and tempering iron containing carbon. It is preferable that the carbon tool steel has excellent impact resistance. Specifically, SK-5, SK-2, etc. can be used, and their thermal expansion coefficients are 100 to 120 × 10 ^-7 /°C in the temperature range of 25 to 200°C.

The base portion 7 can be obtained by quenching and tempering iron (Fe) containing, for example, 0.8 to 1.3 mass% carbon (C) to form it into a predetermined shape and size (for example, a dimension of 12 to 20 mm from the base end 7b to the tip end 7a of the base portion 7).

The Vickers hardness of the blade portion 6 is preferably 2.0 to 3.0 times that of the base portion 7. If the ratio of the Vickers hardness of the blade portion 6 to that of the base portion 7 becomes too small, the entire cutting blade 4 will be prone to excessive deformation (stickiness) when cutting the glass fiber G. In particular, if the contact roll 3 becomes worn, the blade portion 6 will not accurately contact the glass fiber G, making cutting defects more likely. Furthermore, if the ratio of the Vickers hardness of the blade portion 6 to that of the base portion 7 becomes too large, the difference in thermal expansion coefficients between the base portion 7 and the blade portion 6 will become too large, which may make it difficult to achieve a stable bond.

The joint 8 is formed from a nickel alloy layer or a cobalt alloy layer. In particular, the nickel alloy layer has a thermal expansion coefficient (40 to 47 × 10 ^-7 /°C in the temperature range of 30 to 300°C) that is close to that of cemented carbide, and therefore has the advantage that residual stress is less likely to occur in the joint 8 and deformation of the joint 8 can be suppressed.

As shown in Figure 4, in an orthogonal cross section of the joint 8 relative to the longitudinal direction X of the cutting blade 4 (hereinafter simply referred to as the "orthogonal cross section of the joint 8"), the joint 8 has a dendrite layer 9. The orthogonal cross section of the joint 8 is a cross section along the Y direction, such as the A-A cross section in Figure 2. The dendrite layer 9 is a layer containing dendrites (branched crystals) D. The dendrites D are, for example, Ni-Co precipitates, and are presumed to have precipitated as a result of the components of the cutting edge 6 (for example, Co) diffusing into the joint 8 (for example, Ni).

In this embodiment, the dendrite layer 9 is formed in a region of the joint 8, including the vicinity of the interface 8a with the blade portion 6. The dendrite layer 9 is preferably formed uniformly throughout the entire thickness direction Z of the cutting blade 4. The dendrites D contained in the dendrite layer 9 spread in a dendritic pattern from the interface 8a with the blade portion 6 into the joint 8, thereby improving the adhesion between the joint 8 and the blade portion 6 due to the anchor effect. The dendrite layer 9 may also be formed in a region of the joint 8, including the vicinity of the interface 8b with the base portion 7. In this case, the anchor effect improves the adhesion between the joint 8 and the base portion 7. Therefore, from the perspective of improving the bonding strength of the joint 8, the dendrite layer 9 is preferably formed in the region of the joint 8, from the interface 8a with the blade portion 6 to the interface 8b with the base portion 7 (the entire Y-direction of the joint 8). The thickness of the dendrite layer 9 does not need to be uniform in the longitudinal direction X of the cutting blade 4. For example, as described below, the thickness T1 of the dendrite layer 9 included at one end 8c of the joint 8 in the longitudinal direction X may be different from the thickness T2 of the dendrite layer 9 included at the other end 8d of the joint 8 in the longitudinal direction X (see Figure 6).

Although not shown in the figure, a diffusion layer is formed on the base end 6b side of the blade portion 6, where the components of the joint 8 (e.g., Ni) are diffused into the blade portion 6.

As shown in FIG. 5 , in an orthogonal cross section of the joint 8, the joint 8 may contain voids V (shown in black in FIG. 5 ). However, in any orthogonal cross section of the joint 8, the number of voids V with a circular equivalent diameter of 50 μm or more is two or less per 1 ^mm2 . The number of voids V with a circular equivalent diameter of 50 μm or more is preferably one or less per 1 ^mm2 , and more preferably zero. This reliably prevents cracks from occurring in the joint 8 starting from the voids V. Note that the orthogonal cross section may be selected randomly from one central location in the longitudinal direction X, or one central location, one end 8c, and one end 8d in the longitudinal direction X.

In any orthogonal cross section of the joint 8, the dendritic layer 9 preferably contains 10 or fewer voids V.

In any orthogonal cross section of the joint 8, the number of voids V having a circle equivalent diameter of 20 μm or more is preferably 4 or less per 1 mm ² , more preferably 2 or less, and even more preferably 0.

At the interface 8a with the cutting portion 6 in any orthogonal cross section of the joint 8, the number of voids V with a circle equivalent diameter of 10 μm or more per 0.1 ^mm2 is preferably 3 or less, more preferably 2 or less, and even more preferably 0. The number of voids V with a circle equivalent diameter of 10 μm or more is the number of voids V contained per 0.1 ^mm2 region including the interface 8a.

The number of voids V with a circular equivalent diameter of 50 μm or more in an orthogonal cross section of one end 8c of the joint 8 in the longitudinal direction X may be greater than the number of voids V with a circular equivalent diameter of 50 μm or more in an orthogonal cross section of the other end 8d of the joint 8 in the longitudinal direction X. In this case, as shown in Figure 6, it is preferable that the thickness (Y-direction dimension) T1 of the dendrite layer 9 included in one end 8c of the joint 8 in the longitudinal direction X is greater than the thickness T2 of the dendrite layer 9 included in the other end 8d of the joint 8 in the longitudinal direction X. As a result, even if the number of voids V is relatively large at one end 8c of the joint 8, the thickness of the dendrite layer 9 is increased at that portion 8c, thereby maintaining a state in which the joint 8 is less susceptible to cracking. Note that Figure 6 is a cross section of the joint 8 taken along the longitudinal direction X, and schematically shows the area in which the dendrite layer 9 is formed (the cross-hatched area). The thicknesses T1 and T2 of the dendritic layer 9 may be measured, for example, in an orthogonal cross section of the joint 8 where the number of voids V is measured. If the thickness of the dendritic layer 9 varies within the orthogonal cross section of the joint 8, the thicknesses T1 and T2 are defined, for example, by the maximum thickness of the dendritic layer 9 included in that cross section.

In addition, if the thickness of the dendrite layer 9 varies in the longitudinal direction X, although not shown in the figure, the thickness of the diffusion layer (a layer in which components of the joint 8 have diffused into the blade portion 6) included at one end of the blade portion 6 in the longitudinal direction X (the end on the side of one end 8c of the joint 8) may also be greater than the thickness of the diffusion layer included at the other end of the blade portion 6 in the longitudinal direction X (the end on the side of the other end 8d of the joint).

Next, we will explain the manufacturing method for the cutting blade 4 configured as described above.

As shown in Figure 7, this manufacturing method includes a blade portion preparation process S1 for preparing a blade portion 6, a base portion preparation process S2 for preparing a base portion 7, a joining preparation process S3 for placing a joining material 11 between the blade portion 6 and the base portion 7, a joining process S4 for joining the blade portion 6 and the base portion 7 using the joining material 11, and a sharpening process S5 for grinding the tip 6a of the blade portion 6 joined to the base portion 7.

In the cutting edge preparation process S1, the cutting edge 6 is prepared by blending and sintering 85-95% by mass of tungsten carbide (WC) powder with an average particle size of 0.3-1.0 μm and 5-15% by mass of cobalt (Co) powder to form a cemented carbide alloy of specified dimensions (for example, a dimension of 3-7 mm from the base end 6b to the tip end 6a of the cutting edge 6).

In the base preparation process S2, the base 7 is prepared from carbon tool steel that is formed into a predetermined shape and size (for example, the dimension from the base end 7b to the tip end 7a of the base 7 is 12 to 20 mm) by quenching and tempering iron (Fe) containing 0.8 to 1.3 mass% carbon (C).

As shown in Figure 8, in the joining preparation process S3, the base portion 7, blade portion 6, and joining material 11 are positioned so that the tip end 7a of the base portion 7 and the base end 6b of the blade portion 6 are aligned with each other in the longitudinal direction X, sandwiching the joining material 11 on both sides. The joining material 11 is, for example, nickel foil or cobalt foil with a thickness of 0.2 to 0.5 mm.

As shown in Figure 9, in the joining process S4, the joining material 11 is heated by irradiation with a fiber laser L. This locally heats the joining material 11 and its vicinity, forming a joining portion 8 that joins the blade portion 6 and the base portion 7. The joining portion 8 is formed from a nickel alloy layer or a cobalt alloy layer. The alloy layer is formed when nickel or cobalt forms a solid solution with iron, the main component of carbon tool steel, and melts into the cemented carbide alloy. The fiber laser L is a type of solid-state laser that uses an optical fiber as an amplification medium.

By using a fiber laser L in the joining process S4 in this way, as described above, a dendrite layer 9 is formed at the joint 8, and the number of voids V at the joint 8 is also greatly reduced. Therefore, cracks originating from voids V are less likely to occur at the joint 8.

The wavelength of the fiber laser L is, for example, 1.06 μm. The laser output of the fiber laser L is preferably 500 to 1000 W, and more preferably 600 to 800 W. The spot diameter of the fiber laser L is preferably 50 to 300 μm, and more preferably 100 to 200 μm.

As shown in FIG. 10, the fiber laser L is scanned along the longitudinal direction X from one end 11c of the bonding material 11 to the other end 11d. The scanning speed of the fiber laser L may be constant or may vary along the longitudinal direction X of the bonding material 11.

When changing the scanning speed of the fiber laser L, it is preferable to set the scanning speed R1 of the fiber laser L at one end 11c of the joining material 11 (the end where welding starts) slower than the scanning speed R2 of the fiber laser L at other portions of the joining material 11, including the other end 11d of the joining material 11. The scanning speed R2 is, for example, 1.2 to 2.0 times the scanning speed R1. This increases the amount of heat supplied from the fiber laser L to the one end 11c of the joining material 11. Therefore, the amount of heat supplied to the one end 11c of the joining material 11 melts the one end 11c of the joining material 11 while simultaneously preheating the other portions of the joining material 11, including the other end 11d. Therefore, the other portions of the joining material 11, including the other end 11d, are already in a state where they are more likely to melt with less heat, which has the advantage that the joining material 11 can be sufficiently melted even when the scanning speed R2 of the fiber laser L is set relatively fast.

In this case, the number of voids V with a circular equivalent diameter of 50 μm or more contained in an orthogonal cross section of one end 8c of the joint 8 is likely to be greater than the number of voids V with a circular equivalent diameter of 50 μm or more contained in an orthogonal cross section of the other end 8d of the joint 8. Meanwhile, the thickness T1 of the dendrite layer 9 contained in one end 8c of the joint 8 is likely to be greater than the thickness T2 of the dendrite layer 9 contained in the other end 8d of the joint 8. Therefore, the thickness of the dendrite layer 9 increases in areas where there are a large number of voids V, increasing the bonding strength, and maintaining a state in which the joint 8 is less susceptible to cracking.

In the sharpening process S5, the tip 6a of the cutting portion 6 is ground to form a sharp cutting edge. This produces a cutting blade 4 comprising the cutting portion 6, the base portion 7, and a joint portion 8 that joins the cutting portion 6 and the base portion 7. In the sharpening process S5, if necessary, excess portions of the joint portion 8 that bulge outward from both main surfaces of the cutting blade 4 may be ground away.

The present invention is not limited to the configuration of the above-described embodiment, nor is it limited to the above-described effects. Various modifications are possible to the present invention without departing from the spirit of the present invention.

In the above embodiment, the glass fiber manufacturing method may include the following steps: a spinning process in which molten glass is drawn out from multiple nozzles formed at the bottom of the bushing and spun out as continuous, thin glass filaments; a cooling process in which the glass filaments are cooled with a water spray; a bundling process in which a sizing agent is coated on the surface of the glass filter to bundle hundreds to thousands of glass strands into glass strands; a winding process in which the glass strands are wound with a winder; and a cutting process in which the wound glass strands are cut to a predetermined length to form glass chopped strands. The cutting process uses the above-mentioned cutting device 1 (cutting blade 4).

The present invention will be described in detail below based on examples, but the present invention is not limited to these examples.

(1) Cutting Edge A cemented carbide alloy was prepared as the cutting edge by blending tungsten carbide (WC) powder and cobalt (Co) powder, sintering the mixture, and molding it into a predetermined shape and size.
(2) Base Part As the base part, carbon tool steel formed into a predetermined size and shape by quenching and tempering iron (Fe) containing carbon (C) was prepared.
(3) Bonding material (joint part)
Nickel foil (thickness: 0.35 mm) was prepared as a bonding material.

In the comparative example, the joining material was heated using a _CO2 laser to join the blade portion and the base portion to produce a cutting blade. In contrast, in examples 1 and 2, the joining material was heated using a fiber laser to join the blade portion and the base portion to produce a cutting blade. The orthogonal cross section of the joint of each cutting blade was then observed using an electron microscope to check for the presence or absence of a dendrite layer and the number of voids in the orthogonal cross section of the joint. The results are shown in Table 1.

Table 1 above confirms that the cutting blade according to the comparative example, which was bonded using a _CO2 laser, did not form a dendrite layer and had a large number of voids of various sizes in the orthogonal cross section of the bonded portion. In contrast, Table 1 above confirms that the cutting blades according to Examples 1 and 2, which were bonded using a fiber laser, formed a dendrite layer and had a very small number of voids of various sizes in the orthogonal cross section of the bonded portion. In particular, Example 2, in which the fiber laser output was 800 W, produced favorable results, with a densely formed dendrite layer and zero voids of various sizes. Furthermore, while the cutting blade according to the comparative example developed cracks originating from voids in the bonded portion after long-term use (e.g., 200 hours), the cutting blades according to Examples 1 and 2 did not develop cracks originating from voids in the bonded portion even after long-term use.

REFERENCE SIGNS LIST 1 Cutting device 2 Cutting roll 3 Contact roll 4 Cutting blade 5 Rubber layer 6 Blade portion 7 Base portion 8 Bonding portion 9 Dendrite layer 11 Bonding material V Void (cavity defect)
D Dendrite (branched crystal)
G: Glass fiber L: Fiber laser S: Chopped strand S1: Blade preparation step S2: Base preparation step S3: Joint preparation step S4: Joint step S5: Blade sharpening step

Claims (8)

A cutting blade comprising a blade portion including a cemented carbide alloy, a base portion including a carbon tool steel, and a joining portion that joins the blade portion and the base portion and that includes nickel or cobalt,
the joint has a dendritic layer,
In any cross section of the joint portion perpendicular to the longitudinal direction of the cutting blade, the number of voids having a circle equivalent diameter of 50 μm or more is 2 or less per ¹ mm2,
the number of voids having a circle equivalent diameter of 50 μm or more included in the orthogonal cross section of the joint portion at one end in the longitudinal direction of the cutting blade is greater than the number of voids having a circle equivalent diameter of 50 μm or more included in the orthogonal cross section of the joint portion at the other end in the longitudinal direction of the cutting blade;
A cutting blade characterized in that the thickness of the dendrite layer included in the joint at one end of the cutting blade in the longitudinal direction is greater than the thickness of the dendrite layer included in the joint at the other end of the cutting blade in the longitudinal direction. The cutting blade according to claim 1, wherein the dendrite layer is formed across the entire thickness of the cutting blade. A cutting blade as described in claim 1 or 2, wherein the number of voids contained in the dendrite layer in the orthogonal cross section of the joint is 10 or less. The cutting blade according to any one of claims 1 to 3, wherein the number of voids having a circular equivalent diameter of 20 µm or more is 4 or less per 1 ^mm2 in the orthogonal cross section of the joint. The cutting blade according to any one of claims 1 to 4, wherein the number of voids having a circle equivalent diameter of 10 µm or more is 3 or less per 0.1 ^mm2 at the interface between the joint portion and the blade portion in the orthogonal cross section of the joint portion. A glass fiber cutting device equipped with the cutting blade described in any one of claims 1 to 5, characterized in that the cutting blade cuts glass fibers to a predetermined length. A method for manufacturing glass fibers, comprising a cutting step in which glass fibers are cut to a predetermined length using a cutting blade according to any one of claims 1 to 5. a joining preparation step of disposing a joining material containing nickel or cobalt between a cutting portion containing cemented carbide and a base portion containing carbon tool steel;
a joining step of heating the joining material by irradiating it with a fiber laser after the joining preparation step, and joining the blade portion and the base portion together,
In the joining step , a fiber laser is scanned from one end side to the other end side of the joining material along the longitudinal direction of the cutting blade, and
A method for manufacturing a cutting blade, characterized in that the scanning speed of a fiber laser at one end of the joining material is slower than the scanning speed of the fiber laser at other portions including the other end of the joining material.