JP7298006B2 - Cemented carbide cutting blade - Google Patents

Description

The present disclosure relates to cemented carbide cutting blades. This application claims priority from Japanese Patent Application No. 2020-105952 filed on June 19, 2020. All the contents described in the Japanese patent application are incorporated herein by reference.

Conventionally, cutting blades, for example, JP-A-10-217181 (Patent Document 1), JP-A-2001-158016 (Patent Document 2), International Publication No. 2014/050883 (Patent Document 3), International Publication No. 2014 /050884 (Patent Document 4), JP-A-2017-42911 (Patent Document 5) and JP-A-2004-17444 (Patent Document 6).

JP-A-10-217181 Japanese Patent Application Laid-Open No. 2001-158016 WO2014/050883 WO2014/050884 JP 2017-42911 A JP-A-2004-17444

The cemented carbide cutting blade of the present disclosure includes a base and a cutting edge that is provided on the extension of the base and has a cutting edge that is the most advanced portion, has a Vickers hardness HV of 1250 or more and 2030 or less, and has a Vickers hardness HV of 1250 or more and 2030 or less In the perpendicular longitudinal section, the cutting edge is the coordinate origin, the direction from the cutting edge to the base is the Z-axis direction, the direction perpendicular to the Z-axis direction and the blade span direction is the Y-axis direction, and the outer surface of the blade is represented by the YZ plane. , where the coordinates of the first point on the outer surface are (Y1, Z1 (=1.00 μm)), the constant a defined by a=Z1/(Y1) ² and the coordinates of the second point on the outer surface are ( Y2, Z2 (= 5.00 μm)), b = Z2 / (Y2) The ratio b / a to the constant b defined by ² is 0.30 or more and 1.00 or less, and the Y axis of the blade at Z1 The direction thickness T1 is 0.60 μm or more and 1.50 μm or less. 0.30≦b/a≦1.52T1−0.61 when T1 is 0.60 μm or more and 0.91 μm or less, and 0.64T1−0.28≦b/a when T1 is 0.91 μm or more and 1.06 μm ≦1.52T1−0.61, and 0.64T1−0.28≦b/a≦1.00 when T1 is 1.06 μm or more and 1.50 μm.

FIG. 1 is a longitudinal sectional view of a cemented carbide cutting blade 1 according to Embodiment 1. FIG. FIG. 2 is a longitudinal sectional view of a cemented carbide cutting blade 1 according to Embodiment 2. As shown in FIG. FIG. 3 is a longitudinal sectional view of a cemented carbide cutting blade 1 according to Embodiment 3. As shown in FIG. FIG. 4 is a perspective view of an apparatus for explaining the cutting test. FIG. 5 is a cross-sectional view taken along line VV in FIG. 6 shows the thickness T1 and b It is a graph which shows the relationship with /a. FIG. 7 is a microscope observation photograph (microscope) observation image showing chipping of the cutting blade.

[Problems to be Solved by the Present Disclosure]
If the blade thickness is thin, there is a problem that the cutting edge cannot withstand the cutting impact and chipping occurs. If the thickness of the blade is thick, there is a problem that the cutting resistance is high, the quality of the cross section is deteriorated, and the cross section becomes rough.

[Description of Embodiments of the Present Disclosure]
First, the embodiments of the present disclosure are listed and described.

(Embodiment 1)
FIG. 1 is a longitudinal sectional view of a cemented carbide cutting blade 1 according to Embodiment 1. FIG. As shown in FIG. 1, the cemented carbide cutting blade 1 has a cutting edge 121t extending in the blade span direction. FIG. 1 is a longitudinal section in a direction perpendicular to the blade length direction. As shown in FIG. 1, the flat blade-shaped cemented carbide cutting blade 1 has a base portion 110 and a blade portion 120 as a cutting portion. A connecting portion may be provided between the base portion 110 and the blade portion 120 .

(Material)
The material used for the cemented carbide cutting blade 1 is a cemented carbide containing tungsten carbide and cobalt as main components. The content of cobalt used in cemented carbide is in the range of 3-25% by weight. The cobalt content is preferably in the range of 5-20%. The composition of the elements constituting the cemented carbide is specified by ICP emission spectroscopic analysis and Co titration. The cemented carbide in the present disclosure may contain elements such as chromium, vanadium, tantalum, niobium, etc. for adjusting properties such as grain size, in addition to the main components tungsten carbide and cobalt. Preferably, the size of the tungsten carbide crystals in the cemented carbide is between 0.1 μm and 4 μm. More preferably, the crystal size is 2 μm or less.

In addition, it preferably has a component TaC (tantalum carbide) for suppressing grain growth of tungsten carbide in the cemented carbide, and its content is preferably 0.1 to 2% by mass. Additives for suppressing grain growth may be V ₈ C ₇ (vanadium carbide), Cr ₃ C ₂ (chromium carbide). _{At least} one of TaC, _V8C7 , _Cr3C2 can be substituted and combined. In that case, the content of each is 0.1 to 2% by mass.

The cemented carbide has a Vickers hardness HV of 1250 or more and 2030 or less. Vickers hardness is measured with a Vickers hardness tester. If the Vickers hardness is less than 1250, the deformation resistance performance of the material is low, and it becomes difficult to satisfy the buckling resistance and vertical cutting properties that are considered important in cutting. If the Vickers hardness exceeds 2030, even if the structure and the edge line of the cutting edge are smooth, the hardness is high and chipping is likely to occur. Also, as a countermeasure against chipping, not only the material but also the tip shape of the cutting edge is important.

(shape)
The shape of the cemented carbide cutting blade 1 is basically a rectangular plate shape. The thickness is the shortest side of the board.

The cemented carbide cutting blade 1 includes a base portion 110 and a blade portion 120 which is provided on an extension line of the base portion 110 and has a shape whose thickness decreases toward a cutting edge 121t which is the most distal portion.

Preferably, the thickness of the base 110 is constant. The base portion 110 has a thickness of, for example, 50 to 1000 μm, and the required thickness varies depending on the size of the object to be cut. A blade portion 120 for cutting is formed on one side extending from the base portion 110 . The dimension of the blade portion 120 in the direction (Z-axis direction) from the blade portion 120 toward the base portion 110 is expressed as the length or height of the blade portion 120 . The dimension in the direction (Y-axis direction) perpendicular to the blade length direction and the length direction of the blade portion 120 is referred to as the thickness of the blade portion 120 .

In a longitudinal section perpendicular to the blade span direction, the outer shape of the blade part 120 has a portion of 120t that protrudes outward in a range of 5.00 μm from the blade edge, and the convex 120t portion is the blade edge 121t and the distance in the length direction from the blade edge 121t. is positioned outside the straight line S connecting the positions of Z2 (5.00 μm). The presence of the convex portion 120t makes it possible to increase the strength of the blade portion 120 compared to a straight cutting blade that does not have the convex portion 120t.

The outer surface 121s has a curved shape. The angle formed by the two outer surfaces 121s facing each other increases as the cutting edge 121t is approached. 121 s of outer surfaces are bilaterally symmetrical with respect to the centerline C in this embodiment. However, the outer surface 121s may be asymmetrical with respect to the centerline C. The inclination of the outer surface 121s differs between a point 1201 at a distance Z1 from the cutting edge 121t and a point 1203 at a distance Z2 from the cutting edge 121t.

The objects to be cut by the cemented carbide cutting blade 1 are, for example, unfired ceramic green sheets such as laminated capacitors or laminated inductors, metal foils, paper, fibers, or hard resins.

In the case of cutting by force cutting, the object to be cut is cut while being spread. In the case of the object to be cut, for example, a ceramic green sheet, if the material hardness is high, the load on the cutting blade increases, and chipping of the cutting blade is likely to occur.

As shown in FIG. 1, a large load is applied to the cutting edge of the cemented carbide cutting blade 1 that is lowered in the Z-axis direction for cutting. If the blade is thin and the angle formed by the two outer surfaces 121s is small, that is, if the angle is acute, chipping is likely to occur. When chipping occurs, the sharpness of the blade naturally deteriorates, and the cut cross section of the object to be cut is easily damaged, shortening the life of the blade. When the tip of the cutting edge 121t has an extremely sharp angle, cemented carbide, which has high hardness and low toughness compared to other materials, has excellent buckling resistance and wear resistance, but has a problem that it is particularly susceptible to chipping. .

In order to prevent chipping of the cutting edge 121t, the inventor focused on a quadratic function passing through a specific point of the cutting edge 120. FIG. Let the longitudinal section be the YZ plane, and let the cutting edge 121t be the coordinate origin (0, 0). A constant a of a quadratic curve Z= ^aY passing through the origin and the first point (Y1, Z1 (=1.00 μm)) is obtained. When the outer shape of the blade portion 120 is symmetrical with respect to the center line C (Z-axis passing through the origin of coordinates), Y1=T1/2. When the outer shape of the blade portion 120 is left-right asymmetric with respect to the center line C, the points on the outer shape of the blade portion 120 are (Y11, Z1) and (Y12, Z1). Y11 and Y12 are compared, and the larger absolute value is taken as Y1.

A constant b of a quadratic curve Z= ^bY passing through the origin and the second point (Y2, Z2 (=5.00 μm)) is obtained. When the outer shape of the blade portion 120 is symmetrical with respect to the center line C, Y2=T2/2. When the outer shape of the blade portion 120 is left-right asymmetric with respect to the center line C, the points on the outer shape of the blade portion 120 are (Y21, Z2) and (Y22, Z2). Y21 and Y22 are compared, and the larger absolute value is taken as Y2. Obtain a and b by a=Z1/(Y1) ² and b=Z2/(Y2) ² .

Here, the value of b/a is 0.30 or more and 1.00 or less. If it is less than 0.30, it indicates that the blade tip angle θ obtained from the two blade surfaces is large, the cutting resistance on the blade surface is large, the force to spread when cutting is large, and the cut object is cracked. there is a risk of causing If b/a exceeds 1.00, the tip of the cutting edge is relatively flat, indicating that the tip angle θ obtained from the two blade surfaces is small, and the sharpness of the tip of the cutting edge becomes dull. A large impact is applied to the tip, and there is a risk of it being easily chipped. A thickness T1 of the blade portion at Z1 is 0.60 μm or more and 1.50 μm or less. If T1 is less than 0.60 μm, there is a risk that the blade will be thin and easily chipped. If T1 exceeds 1.50 μm, the blade portion becomes too thick and the cutting resistance increases.

0.30≦b/a≦1.52T1−0.61 when T1 is 0.60 μm or more and 0.91 μm or less, and 0.64T1−0.28≦b/a when T1 is 0.91 μm or more and 1.06 μm ≦1.52T1−0.61, and 0.64T1−0.28≦b/a≦1.00 when T1 is 1.06 μm or more and 1.50 μm. If the cutting edge is out of this range, the strength of the cutting edge is reduced and chipping of the cutting edge is likely to occur, or the cutting resistance increases and the cut surface of the object to be cut becomes rough.

In the entire range of Y from 0 to Y2, the outer surface 121s of the blade portion 120 is positioned outside the straight line s connecting the coordinate origin and the point (Y2, Z2).

The present disclosure mainly relates to a flat cutting blade that press-cuts and cuts an object to be cut such as a ceramic green sheet (hereinafter also referred to as a green sheet) of a laminated ceramic capacitor. By setting b/a and T1 within the ranges described above, it is possible to realize highly accurate cutting, suppress damage to the object to be cut, and achieve a stable shape of the object to be cut. In addition, effects such as a long life of the cutting blade can be obtained.

Here, the cemented carbide cutting blade is shaped to have a cutting-contributing part, or cutting edge, and a base (also called a shank) with parallel surfaces for fixing the cutting blade to a cutting device. More specific properties required include good sharpness, wear resistance, adhesion resistance to the object to be cut, strength against buckling, and long life.

Regarding sharpness, the shape of the cutting edge is particularly important, and in consideration of damage to the object to be cut, a thin blade with a small angle (acute angle) at the tip of the cutting edge is preferable. However, it is inevitable that the thinner the blade, the worse the strength. Therefore, cutting blades that are currently used are devised such as increasing the edge angle of the cutting edge by providing a one-step or multiple-step angle from the blade edge to the base.

Hard materials such as cemented carbide are used for such thin blades, in addition to high carbon steel, for example. However, it is not easy to process. Especially when the material is a hard material, although it has rigidity, it is difficult to cut and has low toughness and is easily chipped. Moreover, it becomes easy to chip when using the product.

Conventionally, various cutting blades have been proposed in order to satisfy the above characteristics, but there has been no detailed knowledge about chipping-resistant materials and blade edge shapes.

In addition, it is preferable that the outer shape is curved so that the width of the cutting portion becomes narrower as it approaches the cutting edge in the longitudinal section. The curved shape may have a single radius of curvature, or a so-called compound R shape having multiple radii of curvature.

By forming the outer shape in a curved shape so that the width of the blade portion becomes narrower as it approaches the cutting edge in the vertical cross section, chipping at the stress concentrated portion can be most effectively suppressed.

The present disclosure optimizes the combination of the above, the material and the tip shape, that is, the blade thickness, which are factors that affect chipping, and found that chipping is likely to occur by satisfying all of these. It is.

As for chipping resistance, sharpness of the cutting edge 121t provides good sharpness, but there is a risk of chipping. be. It is obvious that the cutting edge 121t wears as it continues to cut, and it is more desirable to satisfy the ranges of b/a and T1 described above and to have roundness.

The same effect can be obtained even if the blade portion 120, which is the cutting execution portion formed in the direction of the base portion 110, has one blade surface or a plurality of blade surfaces. In addition, when the outer shape of the vertical cross-section is straight, or has a curved line in part, the same effect can be obtained.

A method of processing the blade portion 120 to obtain the above shape is, for example, polishing with a whetstone as in the conventional method. A blasting method can be used as a method for forming a minute curved surface. Furthermore, a fine curved surface can be formed by cutting a material that is softer than the object to be cut, such as a material in which an abrasive is dispersed.

For example, by cutting a hard abrasive-containing solid material mixed with hard material powder with the cemented carbide cutting blade 1, the hard material in the hard abrasive-containing solid material is brought into contact with the blade portion 120 for processing. A blade 120 can be formed.

Here, examples of the hard abrasive-containing solid matter include clayey materials. Examples of hard materials include powders of diamond, W, Mo, WC, Al ₂ O ₃ , TiO ₂ , TiC, TiCN, SiC, Si ₃ N ₄ and BN.

As for the powder particle size of these hard materials, the average particle size of the secondary particles is preferably 1 μm or less in Fsss (Fisher Sub-Sieve Sizer) particle size. In particular, the finish can be obtained by adjusting the type and size of the hard material particles, the amount added to the solid matter, and the processing time. In addition, the manufacturing method of the cemented carbide cutting blade 1 is not limited to the one described above.

(Embodiment 2)
FIG. 2 is a longitudinal sectional view of a cemented carbide cutting blade 1 according to Embodiment 2. As shown in FIG. As shown in FIG. 2, in the cemented carbide cutting blade 1 according to Embodiment 2, the second portion 122 exists in a portion where the distance from the cutting edge 121t exceeds Z2 (5.00 μm).

(Embodiment 3)
FIG. 3 is a longitudinal sectional view of a cemented carbide cutting blade 1 according to Embodiment 3. As shown in FIG. As shown in FIG. 3, it differs from the cemented carbide cutting blade 1 according to Embodiment 1 in that there is a point where the inclination of the outer surface 121s changes discontinuously near the height Z1.

[Details of Embodiments of the Present Disclosure]
(Example 1)
FIG. 4 is a perspective view of an apparatus for explaining the cutting test. FIG. 5 is a cross-sectional view taken along line VV in FIG. The cemented carbide alloy cutting blade 1 (flat cutting blade) used in the test had a blade span direction (X-axis direction) of 40 mm, a base thickness (Y-axis direction) of 0.1 mm, and a blade height (Z-axis direction) of 22 mm. 0 mm, and the blade processing height of the cutting execution portion (the height of the blade portion 120 in the Z-axis direction) was 2.0 mm. The basic composition of the material is tungsten carbide and cobalt, and metal carbides such as chromium carbide, vanadium carbide, and tantalum carbide are used as additives to adjust the grain size of tungsten carbide. got the result. As an example, a cemented carbide material with a Vickers hardness of 1580 was used. The hardness was changed by adjusting the grain size of tungsten carbide and the amount of cobalt added.

<Grinding>
The produced sintered body was ground by a grinder using a diamond whetstone into a plate having a thickness of 100 μm, a blade height of 22 mm, and a length of 40 mm, and the plate was used as a material for processing the tip blade portion.

<Sharpening>
Subsequently, the cutting edge was formed using the above material. In the forming process, a dedicated grinder with a diamond cylindrical grindstone was used, and the material was fixed to a dedicated work rest with an adjustable angle. When the blade has two steps, the processing is performed by the first portion 121 having the tip angle that is the most tip with respect to one side in the direction of the material long side length of 40 mm, and the second portion 122 that is arranged contiguously with it and continues to the base portion 110. was formed.

<Flat outer surface molding>
In order to form the flat outer surface 122s as shown in FIG. 2, a cylindrical grindstone was used to process the leading end into a convex shape on both sides.

<Convex outer surface molding>
In order to form the outer surface 121s, which is a convex curved surface as shown in FIG. A convex shape was formed by continuously pressing the cutting edge against the block at high speed. The pressing speed, angle, and depth were used to adjust the size of the protrusions. Since the formation of the convex shape is a very precise process, it is very important to set fine grinding conditions such as tungsten carbide particles as cutting media, pressing speed and depth.

The arithmetic mean roughness Sa (arithmetic mean height ISO25178) of the outer surfaces 121s and 122s was set to 0.02 μm or less. The arithmetic average roughness Sa of the outer surfaces 121s and 122s is measured using a non-contact surface roughness measuring device using a white light interferometer. Specifically, using a non-contact three-dimensional roughness measuring device (Nexview (registered trademark)) manufactured by Zygo Corporation, the measurement range in the longitudinal section is 0.15 mm in the X direction and 0.05 mm in the Z direction. . The field of view for measurement was a zoom lens with a magnification of 2× and an objective lens with a magnification of 50×.

<Confirmation of cross section>
The cross-section was confirmed by using a Schottky field emission scanning electron microscope JSM-7900F manufactured by JEOL Ltd. at a magnification of 10,000. The blade thickness (thickness of the blade portion 120) at the 00 μm portion was measured. The Vickers conversion hardness was measured using PICODENTOR HM500 manufactured by Fisher Instruments. The results are shown in Tables 1-3.

"Hardness HV" in Tables 1 to 3 refers to the Vickers hardness of the cemented carbide cutting blade 1.
“T1 (μm)” refers to the thickness of the cutting edge 120 in the Y-axis direction at a position 1.00 μm from the cutting edge 121t in the Z-axis direction (Z=Z1). “T2 (μm)” refers to the thickness of the cutting edge 120 in the Y-axis direction at a position 5.00 μm from the cutting edge 121t in the Z-axis direction (Z=Z2).

"Constant a" is a constant defined by a=Z1/(Y1) ² where the coordinates of the first point on the outer surface are (Y1, Z1 (=1.00 μm)). "Constant b" is a constant defined by b=Z2/(Y2) ² where the coordinates of the second point on the outer surface are (Y2, Z2 (=5.00 μm)). "b/a" refers to the value obtained by dividing the constant b by the constant a. "Figure" indicates a drawing corresponding to the shape of each sample. It was confirmed that there is a protrusion 120t positioned outside the straight line S between the coordinate origin and the point 1203 in all the samples. Furthermore, it was confirmed that all the outer surfaces 121s were located outside the straight line S between the coordinate origin and the point 1203 .

6 shows the thickness T1 and b It is a graph which shows the relationship with /a. "Coordinate position" in each table indicates the coordinate position of each sample in FIG.

In the cutting evaluation test, a generally available vinyl chloride plate was used as a cutting object, focusing on uniform composition and hardness. It was fixed using an adhesive sheet having a thickness of 0.1 mm or more and 3.0 mm or less. In addition, the adhesive sheet has the function of preventing the leading edge of the cutting edge from chipping due to contact with the table that supports the object to be cut during press cutting. The object to be cut has a width of 30 mm in the X-axis direction and a thickness of 0.5 mm in the Z-axis direction. The cutting speed was 300 mm/s in the Z-axis direction.

Test conditions (Figures 4 and 5)
Work material: PVC plate 100, thickness 0.5 mm, width 290 mm, length 30 mm, Vickers equivalent hardness HV of 15
Test equipment: Machining center V55 (stage 2004) manufactured by Makino Milling Machine Co., Ltd. and Kistler's cutting dynamometer 9255 (cutting dynamometer 2003) set. A vinyl chloride plate 100 as a work was laminated.

Cutting conditions: cutting speed 300mm/sec, push amount 0.55mm, longitudinal workpiece and blade angle ±0.5°, workpiece and blade cross section angle 90°±0.5°, number of cuts 100 times (2.5mm interval )
In the apparatus shown in FIGS. 4 and 5, the cemented carbide cutting blade 1 was held by chucks 3001 and 3002 . The cemented carbide cutting blade 1 was lowered at a speed of 30 mm/sec and cut continuously. In order to continuously cut, the cutting position is moved each time the cemented carbide cutting blade 1 rises so as not to cut the vinyl chloride plate 100 at the same position.

After 100 cuts, the state of the cutting edge was evaluated by the number of chippings along the entire length of the cutting edge. As for the definition of chipping to be counted, chips having a width of 10 μm or more or a chip having a depth exceeding 3 μm were counted as chips (FIG. 7).

FIG. 7 is a microscope observation photograph (microscope) observation image showing chipping of the cutting blade. In the method of measuring chipping, the entire surface of the 40 mm blade after 100 times of press cutting was observed with a measuring microscope at a magnification of 1000 times. Specifically, an Olympus measuring microscope (STM6-LM) was equipped with a 50-fold eyepiece lens and a 20-fold objective lens, and the cutting blade (XZ plane) was placed on a plane. Care is taken so that the cutting edge 121t of the cutting blade in FIG. 7 and the measuring stage are parallel. The blade edge 121t is focused, the blade edges 121t located at both ends of the chip 121k are aligned with the reference line in the X-axis direction of the measuring instrument, and the Y measurement value is set to "0" as a reference. The width of the chip 121k is defined as the distance between two points where the reference line in the X-axis direction in FIG. 7 intersects with the edge of the chip 121k. The lowest point in the Y direction of the chip 121k measured from the X axis is the depth of the chip 121k. At this time, it was defined that chipping 121k occurred at the cutting edge when either one of width 10 μm or more and depth 3 μm or more was satisfied.

An evaluation of "A" was given when the cutting edge 121t had 5 or fewer chips, a "B" rating was given when there were 6 to 20 chips, and a "C" rating was given when there were more than 20 chips.

Regarding the state of the cut surface, the cut surface was evaluated by photographing the 100th cut product at a magnification of 50 times and counting the number of scratches with a length of 30 μm or more in the cutting direction. Evaluation was made into three grades, "A" for 10 or less, "B" for 11 to 20, and "C" for more than 20.

The results of cutting evaluation are shown in FIG. The horizontal axis indicates T1 in Tables 1 to 3, and the vertical axis indicates b/a. The range surrounded by the solid line of the pentagon, specifically, when T1 is 0.60 μm or more and 0.91 μm or less, 0.30≦b/a≦1.52T1−0.61, and T1 is 0.91 μm or more 1 0.64T1−0.28≦b/a≦1.52T1−0.61 at .06 μm, and 0.64T1−0.28≦b/a≦1.00 at T1 of 1.06 μm or more and 1.50 μm is the effective range. It can be seen that in this range, the results of "A" were obtained for "cutting edge state" and "cut surface quality" in Tables 1 to 3.

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

1 cemented carbide cutting blade, 100 vinyl chloride plate, 110 base, 120 blade, 120t convex, 121 first part, 121k chipping, 121s, 122s outer surface, 121t cutting edge, 122 second part, 2001 double-sided adhesive sheet, 2002 Acrylic plate, 2003, Cutting dynamometer, 2004 Stage, 3001, 3002 Chuck.

Claims (2)

a base;
A blade portion provided on an extension line of the base portion and having a cutting edge that is the most distal portion,
Vickers hardness HV is 1250 or more and 2030 or less,
In a longitudinal section perpendicular to the blade length direction, the blade edge is the coordinate origin, the direction from the blade edge to the base is the Z-axis direction, and the direction perpendicular to the Z-axis direction and the blade length direction is the Y-axis direction. The outer surface is represented by the YZ plane, the coordinates of the first point on the outer surface are (Y1, Z1 (= 1.00 μm)), and the constant a defined by a=Z1/(Y1) ² , and the outer surface Let the coordinates of the second point be (Y2, Z2 (= 5.00 μm)), and the ratio b/a to the constant b defined by b=Z2/(Y2) ² is 0.30 or more and 1.00 or less can be,
Y-axis direction thickness T1 of the blade portion at Z1 is 0.60 μm or more and 1.50 μm or less,
T1 is 0.30 ≤ b/a ≤ 1.52T1-0.61 when T1 is 0.60 μm or more and 0.91 μm or less,
0.64T1−0.28≦b/a≦1.52T1−0.61 when T1 is 0.91 μm or more and 1.06 μm,
A cutting blade made of cemented carbide, which satisfies 0.64T1-0.28≤b/a≤1.00 when T1 is 1.06 μm or more and 1.50 μm. 2. Cemented carbide cutting according to claim 1, wherein the outer surface of said blade portion is located outside the straight line connecting said coordinate origin and point (Y2, Z2) in all ranges of Y from 0 to Y2. blade.

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