WO2023176818A1 - Cutting blade made of cemented carbide - Google Patents

Abstract

This cutting blade made of cemented carbide comprises a base part and a blade part that is provided on a line of extension of the base part and that has a blade edge at the farthest edge end. The recess depth of Co parts constituting the left and right blade surfaces forming the blade edge is 0.008-0.3 μm inclusive.

Description

Cemented carbide cutting blade

The present disclosure relates to a cutting blade made of cemented carbide. This application claims priority based on Japanese Patent Application No. 2022-043429, which is a Japanese patent application filed on March 18, 2022. All contents described in the Japanese patent application are incorporated herein by reference.

Conventionally, cutting blades made of cemented carbide have been disclosed, for example, in JP-A-10-217181 (Patent Document 1), WO 2014-050884 (Patent Document 2), and JP-A-2004-17444 (Patent Document 3). has been done.

Japanese Patent Application Publication No. 10-217181 International Publication No. 2014-050884 Japanese Patent Application Publication No. 2004-17444

The cemented carbide cutting blade includes a base, and a blade part that is provided on an extension of the base and has a cutting edge that is the cutting edge, and the recess depth of the Co part that constitutes the left and right blade surfaces forming the cutting edge. The present invention relates to a cutting blade made of cemented carbide having a diameter of 0.008 μm or more and 0.3 μm or less.

FIG. 1 is a front view of a cutting blade 1 made of cemented carbide. FIG. 2 is a perspective view of the cutting blade 1 made of cemented carbide. FIG. 3 is a perspective view of the two-stage cemented carbide cutting blade 1. FIG. 4 is a photograph showing the surfaces of the blade surfaces 201 and 202. FIG. 5 shows a formula for determining kurtosis Sku. FIG. 6 is a front view of the cemented carbide cutting blade 1 shown for explaining the cutting method.

[Problems to be solved by this disclosure]
Conventional cemented carbide cutting blades have had the problem of low cutting performance.

Patent Document 1 (Japanese Unexamined Patent Publication No. 10-217181) discloses a flat cutting blade for cutting thin plate-like workpieces such as ceramic green sheets, which secures a narrow cutting edge angle that enables high-precision cutting. The present invention discloses a flat cutting blade that has high buckling strength.

A solution to this problem is to form the cutting edge with a flat or concave curved surface that is symmetrical with respect to the center line Y, and to connect the cutting edge and the base with one or more reinforcing parts of the symmetrical concave curved surface. It is proposed to shorten the distance of the cutting section to ensure high-precision cutting while increasing buckling strength.

Patent Document 2 (International Publication No. 2014-050884) discloses a base on a flat plate, left and right blade surfaces that are inclined to approach each other from both sides of the base, and a convex curved surface formed to connect the left and right blade surfaces. In the cross-sectional shape in the plate thickness direction, the short distance between the intersection of two straight lines along the left and right blade surfaces and the tip of the cutting edge is 1 μm or more and 10 μm or less, and the tip The length of the portion is different on the left and right sides with respect to the center line of the base, and the difference is 1 μm or more and 20 μm or less, and further, the internal angle of the intersection angle of the two straight lines along the left and right blade surfaces is 4 μm. We have proposed a flat cutting blade characterized by an angle of at least 60 degrees.

Patent Document 3 (Japanese Unexamined Patent Publication No. 2004-17444) discloses that grinding grooves can be easily formed using a cup-shaped grindstone. A substantially rectangular cutting blade for cutting a plate-shaped ceramic body by applying a pressing force in the thickness direction thereof, the blade having a blade surface formed by a plane along one side in the long side direction; A grinding groove extending in the short side direction is formed on the blade surface, and the blade surface is composed of a plurality of stepped surfaces divided in the short side direction, and the stepped surface on the cutting edge side has a larger angle. Discloses a cutting blade characterized by:

In recent years, downsizing of large MLCCs has been progressing due to the high-density stacking technology of MLCCs (Multilayer Ceramic Capacitors). Downsizing has increased the number of stacked Ni electrodes, and by reducing the particle size of the dielectric barium titanate to tens of nanometers, the distance between the electrodes in the thickness direction has become less than a few hundred nanometers. There is. Therefore, in addition to increasing the hardness of the green sheet, when the distance between the electrodes becomes short, the quality of the cut surface tends to deteriorate. Under such circumstances, the present inventors have discovered a cemented carbide cutting blade that can cut a workpiece with low cutting resistance and reduce damage to the cut surface.

In addition, in the MLCC manufacturing process where this cutting blade is used, there is a demand for cutting blades that can cut with precision, but there are problems unique to push-cutting blades such as re-adhesion after cutting, and the unevenness of the blade surface causes adhesive pooling. It is also a cutting blade that prevents MLCC (green sheet small pieces) from re-adhering after cutting by having this function.

In order to manufacture multilayer ceramic capacitors, there is a need to cut laminated green sheets with a thickness of several hundred μm to several mm. After cutting this continuously with high precision, each piece is fired and electrodes are attached to both ends to create a capacitor. In recent years, there has been an increasing demand for capacitors to be smaller in size to accommodate small devices such as smartphones, which requires a high level of cutting precision. In order to realize such a small-sized ceramic capacitor, it is necessary to give the cutting edge of the cutting blade a function so as not to damage the cutting surface.

As methods for cutting green sheets, there are a method of cutting with a rotating round blade called a dicing method, and a push cutting method using a flat cutting blade as disclosed in the present disclosure. The former method has disadvantages such as poor material yield due to a large amount of cutting waste and poor cutting speed, so the push-cutting method is useful for small-sized products.

FIG. 1 is a front view of a cemented carbide cutting blade 1. FIG. 2 is a perspective view of the cutting blade 1 made of cemented carbide. FIG. 3 is a perspective view of the two-stage cemented carbide cutting blade 1.

As shown in FIGS. 1 to 3, a cutting blade 1 made of cemented carbide includes a cutting edge part 2 that performs cutting, a connecting part 3 connected to the cutting edge part 2, and a cutting blade fixing part 5 connected to the connecting part 3. It has a base 4 fixed by.

The object to be cut 100 can be cut by pressing the cutting edge portion 2 against the object to be cut 100. A cutting blade 1 made of cemented carbide as a flat cutting blade extends in the x direction orthogonal to the y and z directions in FIG.

Blade surfaces 201 and 202 are provided on both sides of the cutting edge portion 2. In FIG. 3, the blade surfaces 203 and 204 are provided, resulting in a two-stage blade. Each blade surface 201 to 204 may have a linear shape or a curved shape. The ridgeline where the blade surface 201 and the blade surface 202 intersect is the blade edge 210.

The cemented carbide cutting blade 1 according to the present disclosure includes a connecting portion 3 as a base, and a cutting edge portion 2 as a blade portion that is provided on an extension of the connecting portion 3 and has a cutting edge 210 as the most distal end. The recess depth of the Co part constituting the left and right blade surfaces 201 and 202 forming the cutting edge is 0.008 μm or more and 0.3 μm or less.

In the cemented carbide cutting blade 1 configured in this way, since the Co portion constituting the blade surface is recessed, the contact area between the object to be cut and the blade surface is reduced, thereby reducing cutting resistance. can. It is possible to prevent adhesive components from adhering to the recessed areas. As a result, cutting performance can be improved. If the depth of the recess in the Co portion is less than 0.008 μm, the effect of the recess is not sufficient. If the depth of the recess in the Co portion exceeds 0.3 μm, the surface of the blade surface becomes rough, resulting in a rough cut surface.

Preferably, the ratio of the area of the Co depression on the left and right blade surfaces forming the cutting edge is 6% or more and 30% or less.

Preferably, the depth of the Co depression on the left and right blade surfaces forming the cutting edge is 0.010 μm or more and 0.3 μm or less.

Preferably, the kurtosis (Sku), which is a parameter of the surface roughness of the left and right blade surfaces forming the cutting edge, is Sku>3.

Preferably, the cobalt content in the cemented carbide is in the range of 3% by mass or more and 25% by mass or less.

Preferably, the hardness of the cemented carbide is a Vickers hardness Hv of 1300 or more and 2030 or less.

Such thin blades are made of hard materials such as carbon tool steel, stainless steel, and cemented carbide. However, machining is not easy, and the reasons for this are that, although the material is hard, although it has rigidity, it is difficult to cut, has low toughness and is easily chipped, and if the blade is thin, it is made of hard material. Particularly at the tip of the cutting edge, the blade tends to escape due to the pressure of the grindstone during machining.

Conventionally, various cutting blades have been proposed to meet the above characteristics, but if the shape is complicated, it is inevitable that processing becomes even more difficult. A cutting blade that does this has not been obtained.

Effect The present inventor attempted to reduce the contact area on which the cutting edge acts by making the WC convex by making the Co constituting the blade surface into a concave shape from the viewpoint of tribology. It has been confirmed that this reduces the cutting resistance and also reduces the phenomenon in which the glue that adheres to the blade surface when cutting the MLCC green sheet is transferred to the cut surface and the green sheet is reattached. This provides the following effects.

1) Reduction of cutting resistance Compared to the blade surface finished by conventional grinding, the blade surface is made convex with WC and concave with Co, reducing the contact area of the blade surface and lowering the frictional resistance during cutting. Even if the cutting edge angle θ is not made acute, cutting resistance can be reduced by 15% to 28% while suppressing cutting edge breakage at a cutting edge angle θ that is less likely to break.

2) By making the blade surface crater-shaped (WC convex, Co concave), adhesive adhesion to the cut surface of MLCC is suppressed. Re-adhesion of cut MLCC green sheets (a phenomenon in which cut workpieces stick together again) can be reduced. can. The MLCC green sheet is cut using a cutting blade by adhering the green sheet with a single-sided tape using a foam release agent and pressing it. The cutting edge of the cutting blade cuts into the area of the glue that adheres the green sheet, but at that time, the glue adheres to the cutting edge. Furthermore, after cutting into the green sheet, when the cutting blade is removed from the cutting edge with poor sharpness, the green sheet elastically recovers, and the width of the green sheet is restored to be larger than the set cutting width. At this time, the glue adhering to the first blade surface comes into contact with the cut surface of the green sheet, causing re-adhesion. In response to this phenomenon, the amount of glue adhering to the workpiece can be suppressed by forcibly removing the Co part on the blade surface and increasing the area of the recessed part to serve as a glue reservoir. Therefore, reattachment (sticking together again) of the cut workpieces can be suppressed.

FIG. 4 is a photograph showing the surfaces of the blade surfaces 201 and 202. In FIG. 4, the black part is tungsten carbide 21, and the white part is cobalt 22. In the present disclosure, by forming the cobalt 22 in a concave shape, it is possible to prevent the cut workpiece from adhering to the cobalt 22 again.

Kurtosis The blade surface according to the present disclosure has a step difference between the WC and Co that is 0.008 μm or more and 0.3 μm or less, and the kurtosis (histogram sharpness (Sku)) of the roughness curve on the front and back surfaces of the blade surface is more than 3. It is preferable. FIG. 5 shows a formula for determining kurtosis Sku.

Kurtosis (Sku) is determined according to JIS B0681-2 (2018) and is shown by the formula in FIG. 5. It refers to the kurtosis of the surface and is an index that expresses the sharpness of the height distribution. When SKu is 3, it indicates that the sharpness distribution of the convex portions or concave portions is close to a normal distribution. As Sku becomes larger than 3, the number of sharp, sharp protrusions or depressions increases with respect to the reference height Sq (root mean square height), and as Sku becomes smaller than 3, the number of steep, sharp protrusions increases. (or represents a decrease in the number of recesses). In other words, when the Sku of the blade surface exceeds 3, the contact area when cutting the green sheet becomes smaller and the cutting resistance becomes smaller.

Material The material used for the cutting blade is a cemented carbide whose main components are tungsten carbide and cobalt, and the size of the tungsten carbide crystal grains in the alloy is an average grain size of 0.1 μm or more and 4 μm or less, more preferably 2 μm or less. The average grain size is determined by measuring the surface of the cemented carbide in an SEM photograph at a magnification of 10,000 times, selecting 100 arbitrary crystals, and using the formula (major axis + minor axis)/2 for each crystal. The particle size was calculated based on , and the average value of 100 particle sizes was determined.

Furthermore, in order to control the crystal grains of tungsten carbide, it is also possible to add TaC (tantalum carbide), a component for suppressing crystal grain growth, of 0.1% by mass or more and 2% by mass or less. This additive can also be replaced and combined with V ₈ C ₇ (vanadium carbide), Cr ₃ C ₂ (chromium carbide). In that case, the amount of each added is 0.1% by mass or more and 2% by mass. Cobalt used in the cemented carbide ranges from 3% by mass to 25% by mass, preferably from 5% by mass to 20% by mass. TaC, V ₈ C ₇ and Cr ₃ C ₂ are obtained by dissolving these components from cemented carbide using nitric acid or hydrofluoric acid, and then converting the resulting liquid into a liquid using an ICP emission spectrometer (Issuance spectroscopy). can be measured. After Co is dissolved from a cemented carbide using nitric acid or hydrofluoric acid, the mass of the solution whose liquid properties are adjusted can be measured using a potentiometric titration device (potentiometric titration method).

The hardness of the cemented carbide preferably has a Vickers hardness Hv of 1300 or more and 2030 or less.
Thickness The base material thickness T of the cemented carbide cutting blade is preferably 0.1 mm or more and 0.6 mm or less. By setting it within this range, it can be used as a cutting blade (compatible with a cutting machine) for laminated ceramic green sheets. The cutter with a thickness of 0.1 mm is used for the thinnest chips of ceramic capacitors, and can reduce the grinding allowance and reduce the grinding resistance when producing sharp edges such as a 20° cutting edge angle by grinding, resulting in high precision. You can make a cutting edge. On the other hand, cutters with a base material thickness of 0.4 to 0.6 mm are suitable for cutting thick chips with a thickness of 1 mm or more because the rigidity (bending of the root of the cutting edge) can be improved by increasing the thickness of the cutter itself. There is. Another advantage is that the rigidity of the base of the blade is increased, making diagonal cuts less likely to occur.

The thickness of a carbide cutting blade can be measured using a micrometer or a laser measuring device.
The relationship between the length L (mm) and the height W (mm) (FIG. 2) of the cemented carbide cutting blade is preferably 1≦L/W≦20.

It is preferable that the cutting edge angle θ is 6°≦θ≦30° or less.
The smaller the cutting edge angle, the smaller the cutting resistance and the less likely diagonal cutting will occur. In other words, the volume that penetrates into the workpiece becomes smaller. For angles of 10 degrees or less, a single-stage blade may be used, but since the width dimension forming the blade surface becomes large, there are problems such as the blade tip being prone to collapse due to grinding resistance and making it difficult to process the blade edge into a highly accurate shape. It is known that chipping during cutting is extremely likely to occur when θ≦20°.

(Example 1)
The tip blade was formed using cemented carbide FM10K material manufactured by Allied Materials Co., Ltd. The flat cutting blade used in the test has a blade length direction L: 40 mm, a base thickness T: 0.1 mm, and a blade height W: 25.0 mm. The cutting edge angle θ of the cutting edge part 2 as the cutting part is 20° ± 5', the first stage blade width is 0.1 mm, and the second stage blade angle (the extended plane of the second stage blade surface intersects angle) was set to 4°±10'. For the cutting edge forming process, a surface grinder was used, and a diamond cylindrical grindstone was used to true the side of the grindstone, and the material was fixed on a special work rest with an adjustable angle. As a result, cemented carbide cutting blades 1 of sample numbers 1 to 55 shown in Tables 1 to 3 were manufactured.

<Co recess formation forming the blade surface>
The method for removing Co from the blade surfaces 201 and 202 that form the tip angle was to create a chemical solution in which nitric acid (HNO ₃ ) was diluted with 5 times as much water as CONC1 (concentrated nitric acid was diluted with 4 to 5 times as much water). . In addition, the cemented carbide cutting blade 1 is set in a jig that can immerse the cutting edge in nitric acid to a depth of 0.2 mm, and the cutting blade is immersed in the chemical solution for 10 seconds to 50 minutes. The depth of the Co depression was controlled by time management.

<Measurement of the ratio of the area of the Co depressions forming the blade surface>
Regarding the proportion of Co depressions forming the blade surface, we used image processing software: Planetron's Image Plus, imported a 10,000x SEM photograph image into the software, and processed Co and WC in an 8 μm x 8 μm area into binary values through image processing. (Figure 4) and measured. On the first stage blade surfaces 201 and 202, WC was highlighted as black and Co was highlighted as white, and the area of Co was calculated using this software to calculate the percentage.

<Measurement of step difference between WC and Co>
The average distance of the convex portions or concave portions, the average height of the convex portions, or the average depth of the concave portions were measured on the surface having the WC convex portions or the Co concave portions using an atomic force microscope (AFM: Dimension Icon) manufactured by Bruker. The maximum sample size that can be measured with this AFM is φ210, so it can be observed without destroying the cutting blade. The measurement conditions were a scan area of 5 μm×5 μm. The scanning speed of the cantilever was measured at 0.1 to 80 Hz, and the height of the WC convex portion and the maximum depth of the Co concave portion were determined from the 3D profile regarding the height of each point. This was measured at three locations each on the front and back blade surfaces randomly selected from the surface of the blade surface formed above, and the maximum height difference between WC and Co was determined.

<Measurement of surface roughness Sku (surface kurtosis)>
The Sku kurtosis of the blade surface was measured using a non-contact three-dimensional roughness measuring device (Nexview (registered trademark)) manufactured by Zygo Corporation, and the measurement range in the longitudinal section was 140 μm in the X direction and 30 μm in the Z direction. shall be. The measurement field of view was set to have an objective lens magnification of 50 times and a ZOOM magnification of 1 time.

<Measurement of blade edge width>
To measure the edge line width of the cutting edge, use a Schottky field emission scanning electron microscope JSM-7900F manufactured by JEOL Ltd. to take an image from a direction perpendicular to the edge of the cutting edge at 5,000 to 10,000 times magnification, and measure the machine coordinates and length measurement function. A cutter with a cutting edge edge of 0.5 μm or less was used as the test blade.

<Chip measurement>
The chipping of the cutting blade was measured using a tool measuring microscope STM-UM manufactured by Olympus Corporation at a magnification of 500 times. In all samples, it was confirmed that the chip depth was within 1.5 μm and the chip width was within 10 μm.

<Cutting test>
In order to confirm the effectiveness of the present cutting blade, we performed push-cutting on vinyl chloride plates and evaluated the cut surface based on the cutting resistance and the scratches the cutting blade made on the object being cut. The effectiveness of this application was confirmed by checking the incidence rate. As shown in FIG. 6, an object to be cut (work) 100 is cut with a cutting blade 1 made of cemented carbide. An acrylic base 102 is placed on the cutting dynamometer 103. A thermally releasable adhesive sheet 101 is interposed between the base and the object 100 to be cut. The object to be cut 100 is cut by moving the object to be cut 100 in the direction shown by the arrow 110 while reciprocating the cutting blade 1 made of cemented carbide in the direction shown by the arrow 111.

Conditions for this test Cutter specifications: Blade angle θ16° to 20°, second stage angle 4°, thickness T: 0.1mm, length L: 40mm
Work material: PVC board, thickness 0.5mm, length 290mm, width 30mm
Test equipment: A cutting dynamometer 103 manufactured by Kistler was set (hereinafter referred to as the cutting dynamometer) in a machining center V55 (hereinafter referred to as the cutting machine) manufactured by Makino Milling Co., Ltd. The work set was an acrylic plate with a thickness of 10 mm from the top of the dynamometer surface plate. A 1 mm foamed double-sided adhesive sheet and a workpiece (the above-mentioned PVC board) having a thickness of 0.5 mm±0.1 (these constitute the object to be cut 100) are used, and the cutter installation accuracy is set at the workpiece in the longitudinal direction and the blade angle ±0. 5°, and the cross-sectional angle between the workpiece and the blade was 90°±0.5°. The cutting conditions were a cutting speed of 300 mm/s, a cutting interval of 1 mm, and an indentation depth of 0.1 mm into the adhesive layer of the thermally releasable sheet. We evaluated the reattachment of The results obtained by repeating this result for each condition are shown in Tables 1 to 3.

The "cutting resistance" in Tables 1 to 3 is the average cutting resistance measured by the cutting dynamometer 103, and was defined as 160N or less: A, more than 160N and 169N or less: B, and more than 169N: C. "Reattachment" indicates the percentage of the number of reattachments to the cemented carbide cutting blade 1 at 1000 cutting locations, 0.5% or less: A, more than 0.5% and 2.0% or less: B, 2 More than .0%: Rated C.

Regarding the optimum ratio of recesses in the Co part constituting the blade surface, the area ratio of recessed Co to smooth WC grains is preferably 6% to 30%. If the area ratio of Co recesses exceeds 30%, the strength of the cutting edge will be extremely reduced, leading to chipping. On the other hand, if the area of the Co recess is less than 6%, the contact area increases, cutting resistance increases, and sharpness decreases. A more preferable range is 10% to 22%. The most preferable range is 10% to 15%.

Regarding the optimum step range between WC and Co, the depth of the recess in the Co portion needs to be 0.008 μm or more and 0.3 μm or less. If the depth of the concave portion of the step Co between WC and Co is smaller than 0.008 μm, it will become a worn surface and the contact area with the workpiece will increase, resulting in high cutting resistance. On the other hand, if the step is larger than 0.3 μm, chipping will be induced at the cutting edge. A more preferable range is 0.010 μm or more and 0.3 μm or less. Moreover, the most preferable range is 0.010 μm or more and 0.1 μm or less.

Regarding the optimum range of the three-dimensional roughness parameter Sku (kurtosis), the step difference between WC and Co is 0.008 μm to 0.3 μm.Kurtosis of the roughness curve on the front and back of the blade surface: Sku (the sharpness of the histogram exceeds 3) It is preferable, and more preferably 4 or more.

The embodiments and examples disclosed this time should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is indicated by the claims rather than the above description, and it is intended that equivalent meanings and all changes within the scope of the claims are included.

1 Cemented carbide cutting blade, 2 Blade tip, 3 Connection part, 4 Base, 5 Cutting blade fixing part, 100 Object to be cut, 201, 202, 203, 204 Blade surface, 210 Blade edge.

Claims (6)

1. It comprises a base, and a blade part that is provided on an extension line of the base and has a cutting edge that is the cutting edge, and the depth of the recess of the Co part that constitutes the left and right blade surfaces forming the cutting edge is 0.008 μm or more and 0.3 μm. The following is a cutting blade made of cemented carbide.
2. The cemented carbide cutting blade according to claim 1, wherein the ratio of the Co recess area of the left and right blade surfaces forming the cutting edge is 6% or more and 30% or less.
3. The cemented carbide cutting blade according to claim 1 or 2, wherein the depth of the Co recess on the left and right blade surfaces forming the cutting edge is at least 0.010 μm and not more than 0.3 μm.
4. The cemented carbide cutting blade according to any one of claims 1 to 3, wherein kurtosis (Sku), which is a parameter of surface roughness of the left and right blade surfaces forming the cutting edge, is Sku>3.
5. The cemented carbide cutting blade according to any one of claims 1 to 4, wherein the content of cobalt in the cemented carbide is in the range of 3% by mass or more and 25% by mass or less.
6. The cemented carbide cutting blade according to any one of claims 1 to 5, wherein the hardness of the cemented carbide is a Vickers hardness of Hv 1300 or more and Hv 2030 or less.

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