JP2012066336A - Cutting insert made of tungsten cemented carbide based super hard alloy, and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cutting insert made of WC based super hard alloy capable of obtaining a good finish surface, having a long lifetime and less likely to be abnormally damaged, and to provide a method of manufacturing the same.SOLUTION: In the cutting insert made of the WC based super hard alloy containing Co as a binder phase component, an hcp transformation rate of a binder layer Co is ≥0.3 and the surface roughness Ra is ≤0.2 μm or less, for a surface area of a chip breaker part in which wet blast treatment is applied to a sintered skin in a range from a crossing edge line between a flank surface and a honing part within at least 2 mm toward the inside of a rake surface, and the residual stress of a WC hard phase of an insert surface is ≥850 MPa in terms of compression. Accordingly, crack generation and development are prevented, and chipping resistance and finish surface accuracy of a material to be cut are improved even in cutting conditions such as wet cutting or intermittent cutting where thermal shock acts on a cutting blade.

Description

  The present invention relates to a tungsten carbide (hereinafter referred to as WC) -based cemented carbide cutting insert that is less likely to cause abnormal damage even in high-load cutting, and a method for manufacturing the same.

As is well known, a cutting insert made of a WC-based cemented carbide has a WC-based cemented carbide as a base material, and for example, a cutting edge is formed at the intersecting ridge line portion between a rake face and a flank face of a polygonal flat plate insert body. It is attached to an insert detachable tool body and is widely used for cutting metal work materials.
Various techniques have been proposed for improving the impact resistance, fracture resistance, etc. of such cutting inserts.
For example, as shown in Patent Documents 1 and 2, the surface of a WC-based cemented carbide cutting insert containing 2 to 12% by weight of Co as a binder phase component is subjected to shot peening treatment, and the WC hard phase on the surface of the insert is subjected to shot peening treatment. A compressive residual stress of 30 to 80 kg / mm ^{2 is applied} , and a Co phase (hereinafter referred to as “fcc”) of a face-centered cubic structure (hereinafter referred to as “fcc”) is used as the Co binder phase of the WC-base cemented carbide. ), The integrated strength ratio of the Co phase (hereinafter referred to as “hcpCo”) of the hexagonal crystal structure (hereinafter referred to as “hcpCo”) is 0.2 or more. It has been proposed to improve performance.

JP-A-6-108258 Japanese Patent Laid-Open No. 6-114641

In recent years, in the field of cutting work, there has been a demand for high-speed and high-load cutting for the purpose of higher efficiency. However, when conventional inserts are used for such high-load cutting, the progress of wear is increased. However, there is a drawback that abnormal damage such as chipping or chipping occurs before the tool life is reached due to normal wear, and the finished surface accuracy of the work material is deteriorated and the tool life is likely to be reached.
In particular, in each of the proposed conventional inserts, the chemical vapor deposition coated insert is subjected to shot peening treatment or sand blasting treatment from above the hard coating layer, thereby controlling the residual stress on the insert surface portion and hcp of the binder phase. By trying to improve the impact resistance and fracture resistance by causing transformation, these treatments use a relatively large spherical projection material having an average particle size of 0.1 mm to 1 mm (Patent Document 1). In this example, a steel ball having a diameter of 0.4 mm is used), and the processing energy becomes excessive, coarse cracks and chips are generated on the insert surface during manufacturing, and a relatively large spherical projection material is used. If used, since the polishing action is weak, the effect of improving the surface roughness is small, and the surface roughness of the insert has a cutoff value of 0.08. Become a rough surface remained above 0.2μm in arithmetic average roughness Ra of m, the roughness change inevitably reduced.

  In addition to the above, as a technique for improving the fracture resistance, blasting to the insert surface by dry blasting mainly for applying residual stress is also known. In dry blasting, it has been found that defects are likely to occur due to residual impurities due to the biting of the abrasive material into the insert surface.

  Therefore, in the cutting inserts manufactured by these conventional methods, abnormal defects or chipping, which may be caused by the above-mentioned defects, may occur during cutting, and the finished surface of the work material may become cloudy, murky, fluffed, etc. In particular, high-speed cutting and interrupted cutting with a high load on the cutting edge have a problem that there is no abnormal damage, long life, and excellent finish surface accuracy. Actually, the product is not fully satisfactory.

  It has also been known for a long time that when the WC-based cemented carbide insert is ground with a grindstone, the binding phase Co on the surface thereof is transformed from fcc to hcp (for example, “Cemented carbide and sintering”). "Hard material" P156, Atsushi Suzuki Maruzen Co., Ltd.) is trying to improve the fracture resistance by generating hcp transformation by grinding process. It can be applied to the flank face of inserts formed by machining, or chip breakers formed by grinding, etc., but it is currently the most frequently used mold on the rake face in the market. It is practically impossible to apply the prior art to the rake face of the insert on which the chip breaker having a three-dimensional shape is formed without damaging the shape of the breaker. .

  The present invention has been made in view of the circumstances as described above, and basically provides a WC-based cemented carbide cutting insert capable of exhibiting excellent cutting performance over a long period of use, and a method for manufacturing the same. WC-based cemented carbide cutting inserts that are less likely to cause abnormal damage even in intermittent cutting and milling, where high loads are applied to the cutting edges and heat cracks are likely to occur, and a method for manufacturing the same The issue is to provide.

As a result of intensive experiments and research on the solution to the above problems, the present inventors, in cutting with a high load, first, a minute thermal crack is generated during the cutting, it grows and progresses, One of the major causes of abnormal damage such as chipping and chipping, and the inability to obtain a good work surface finish when actually used for high-load cutting, is a micro thermal crack that has occurred on the cutting edge. I found out that
It is known that Co of the binder phase on the surface of the cutting insert made of a WC-based cemented carbide, particularly the surface of the sintered skin, has a crystal structure of usually fcc. As a result of further research on the means for improving the thermal shock resistance of cemented carbide cutting inserts, the surface of the insert, particularly the rake face, in the region including all or part of the chip breaker portion of the sintered skin, By performing wet blasting under a predetermined condition, at least the surface of the binder phase Co including the region (usually fcc crystal structure) is transformed into an hcp crystal structure having a higher thermal crack resistance, and at least the region is simultaneously formed. By smoothing the included surface so that it does not become the starting point of thermal cracks, thermal cracks are less likely to occur. It was found that it is possible to et.

Here, the region where the Co of the binder phase having the fcc crystal structure should be transformed into the hcp structure is a region of the rake face from the intersecting ridge line between the flank face and the honing part (cutting edge part) in the insert surface part. It is a region that constitutes a chip breaker part that forms a sintered skin within a range of at least 2 mm toward the inside, and a region to be smoothed is the same region.
The region where the binder phase Co is transformed into the hcp structure and the surface is smoothed is, as described above, "from the intersecting ridge line between the flank and the honing portion (cutting edge portion) of the insert surface portion. The reason why it is defined as “the area that constitutes the chip breaker part that forms the sintered skin within the range of at least 2 mm toward the inside of the rake face” is the scraping area of the chips discharged when the insert is used for cutting Is usually within a range of about 2 mm from the intersecting ridge line of the flank and the honing part (cutting edge part) to the inside of the rake face, and this range is the place where thermal cracks are most likely to occur, Moreover, normally, at least a part of the chip breaker portion of the sintered skin, which is a rough surface that is likely to be the starting point of thermal cracking, is located in that region.

  At the same time, the inventors of the present invention have at least a transformation ratio to the hcp structure effective for transforming Co in the binder phase on the surface in the region into the hcp structure and improving the thermal crack resistance in the region, that is, The lower limit of the hcp transformation rate defined by the equation (1) described later was found from the peak intensity of hcpCo and the peak intensity of fccCo at the surface of the region by X-ray diffraction.

  Furthermore, applying wet blasting as described above is effective not only for the transformation of Co and smoothing of the surface, but also for the application of a large compressive residual stress to the WC hard phase of the cemented carbide on the insert surface. It turned out to be. That is, by applying a compressive residual stress of 850 MPa or more to the region by wet blasting, it is possible to more reliably suppress the occurrence of thermal cracks and growth, and to further improve the fracture resistance against mechanical shock. Can do it.

  As described above, by performing wet blasting on the surface portion including at least the region on the surface of the insert, occurrence of coarse cracks or the like that occurred during insert manufacturing in the case of the prior art is suppressed, and at least within the region. At the same time, the hcp transformation of Co and the addition of compressive residual stress are performed, thereby reducing the frequency of thermal cracking during cutting, and even if thermal cracking occurs, the progress As a result, we have newly discovered that it is possible to manufacture inserts that are less likely to cause abnormal defects (defects and chipping) and that can obtain good work surface finish accuracy. Invented the invention.

Therefore, the tungsten carbide-based cemented carbide cutting insert according to the basic form of the present invention (first form) is
The hard phase is made of a tungsten carbide-based cemented carbide containing WC as a main component and Co as a binder phase component in an amount of 4 to 15% by mass, and includes a flank, a honing portion, and a rake face, and at least one of the rake faces. In a tungsten carbide-based cemented carbide cutting insert having a chip breaker portion formed by a mold in the portion;
The peak intensity value obtained from the (101) plane of Co having a hexagonal structure (hereinafter referred to as “hcpCo”) when X-ray diffraction is performed on the binder phase Co on the insert surface portion is represented by hcp [101]. The peak intensity value of hcpCo relative to the total peak intensity of hcpCo and fccCo, where fcc [200] is the peak intensity value obtained from the (200) plane of Co (hereinafter referred to as “fccCo”) having a face-centered cubic structure. The ratio is defined by the following formula (1) as the hcp transformation rate,
Of the insert surface portion, a chip breaker portion is formed by subjecting the sintered skin to wet blasting within a range of at least 2 mm from the intersecting ridge line between the flank face and the honing portion toward the inside of the rake face. The hcp transformation rate in the region is 0.3 or more,
In addition, the surface roughness in the region is 0.2 μm or less in terms of arithmetic average roughness Ra at a cutoff value of 0.08 mm.
hcp transformation rate = hcp [101] / (hcp [101] + fcc [200]) (1)

  A tungsten carbide-based cemented carbide cutting insert according to the second aspect of the present invention is the tungsten carbide-based cemented carbide cutting insert according to the first aspect, wherein the hard phase in at least the region of the insert surface portion. The residual stress is 850 MPa or more in compression.

  Furthermore, the tungsten carbide-based cemented carbide cutting insert according to the third aspect of the present invention is the tungsten carbide-based cemented carbide cutting insert according to the first aspect, wherein the hcp transformation rate at the flank surface of the insert surface portion. Is 0.3 or more, and the surface roughness of the flank is 0.2 μm or less in terms of arithmetic average roughness Ra at a cutoff value of 0.08 mm.

  The tungsten carbide-based cemented carbide cutting insert according to the fourth aspect of the present invention is the tungsten carbide-based cemented carbide cutting insert according to the first aspect, wherein the hard phase on the flank surface of the insert surface portion is the hard phase. The residual stress is 850 MPa or more in compression.

  A tungsten carbide-based cemented carbide cutting insert according to a fifth aspect of the present invention is the tungsten carbide-based cemented carbide cutting insert according to any one of the first to fourth aspects, The honing part has a surface roughness of 0.1 μm or less in terms of arithmetic average roughness Ra at a cutoff value of 0.08 mm.

  Furthermore, a sixth aspect of the present invention relates to a surface-coated tungsten carbide-based cemented carbide cutting insert, and the surface-coated tungsten carbide-based cemented carbide cutting insert according to the sixth aspect includes On the surface of the tungsten carbide-based cemented carbide cutting insert of any one of the fifth forms, IVa group element, Va group element, VIa group element, Al, Si, Y, Mn, Ni in the periodic table And one or more hard coatings composed of a compound comprising at least one element selected from the group consisting of S and S, and at least one element selected from the group consisting of carbon, nitrogen, oxygen and boron, It is formed by a physical vapor deposition method (PVD method).

The seventh aspect of the present invention relates to a method for manufacturing a tungsten carbide-based cemented carbide cutting insert, and the method for manufacturing a tungsten carbide-based cemented carbide cutting insert according to the seventh aspect includes:
The hard phase is composed of a tungsten carbide-based cemented carbide containing WC as a main component and Co as a binder phase component in an amount of 4 to 15% by mass, and includes a flank, a cutting edge, and a rake face, and at least of the rake face. In producing a tungsten carbide-based cemented carbide cutting insert using a tungsten carbide-based cemented carbide cutting insert base part having a chip breaker portion formed of a sintered skin formed by a mold;
Of the surface portion of the tungsten carbide-based cemented carbide cutting insert substrate, a chip forming a sintered skin at least within a range of 2 mm or less from the intersecting ridge line between the flank and the honing portion toward the inside of the rake face. In the region constituting the breaker part, a wet blasting process for performing wet blasting,
A honing step of performing honing on the cutting edge portion of the surface of the tungsten carbide based cemented carbide cutting insert base;
It is obtained from the (101) plane of the hexagonal structure Co (hereinafter referred to as “hcpCo”) when X-ray diffraction is performed on the binding phase Co in the surface portion after the wet blasting process and the honing process are completed. The peak intensity value is hcp [101], and the peak intensity value obtained from the (200) plane of Co having a face-centered cubic structure (hereinafter referred to as “fccCo”) is fcc [200]. The ratio of the peak intensity of hcpCo to the total peak intensity is defined by the formula (1) as the hcp transformation rate,
The hcp transformation rate at least in the region of the insert surface portion is 0.3 or more,
Moreover, a tungsten carbide-based cemented carbide cutting insert having a surface roughness at least in the region of the insert surface portion, which is an arithmetic average roughness Ra at a cutoff value of 0.08 mm, is 0.2 μm or less. It is what.

  The tungsten carbide-based cemented carbide cutting insert manufacturing method according to the eighth aspect of the present invention is the tungsten carbide-based cemented carbide cutting insert manufacturing method according to the seventh aspect, wherein the wet blasting step includes: A wet blast treatment is performed by spraying a polishing liquid from at least one blast gun while rotating around the axis while sandwiching and holding the insert base by a pair of rotation shafts rotatable around the axis. It is characterized by.

  The tungsten carbide-based cemented carbide cutting insert manufacturing method according to the ninth aspect of the present invention is the tungsten carbide-based cemented carbide cutting insert manufacturing method according to the eighth aspect, wherein the wet blasting step is performed. A wet blast treatment is performed by injecting a polishing liquid from a blast gun at an injection angle of not less than 60 degrees and not more than 60 degrees with respect to an axial direction of the rotation shaft that rotatably inserts the insert base. is there.

  And the manufacturing method of the tungsten carbide based cemented carbide cutting insert according to the tenth aspect of the present invention is the method for manufacturing the tungsten carbide based cemented carbide cutting insert of the ninth aspect, in the wet blasting step, The injection angle is 40 degrees or more and 50 degrees or less.

  And the manufacturing method of the tungsten carbide-based cemented carbide cutting insert according to the eleventh aspect of the present invention is the tungsten carbide-based cemented carbide cutting insert according to any one of the seventh to tenth embodiments. In the manufacturing method, the honing step is performed after the wet blasting step.

  And the manufacturing method of the tungsten carbide-based cemented carbide cutting insert according to the twelfth aspect of the present invention is the tungsten carbide-based cemented carbide cutting insert according to any one of the seventh to eleventh aspects. In the manufacturing method, the honing process in the honing step is performed by wet brush honing.

  A thirteenth aspect of the present invention relates to a method for manufacturing a surface-coated tungsten carbide-based cemented carbide cutting insert, and the tungsten carbide group according to any one of the seventh to twelfth aspects. The surface of the tungsten carbide based cemented carbide cutting insert manufactured by the manufacturing method of the cemented carbide cutting insert is coated with a hard coating by a physical vapor deposition method (PVD method).

  According to the cutting insert made of a WC-based cemented carbide according to the present invention, basically, of the insert surface portion, at least 2 mm or less from the intersecting ridge line of the flank face and the honing portion toward the inside of the rake face. Within the range, the hcp transformation is generated for the region constituting the chip breaker part forming the sintered skin, and the ratio of hcpCo in the region is determined so that the hcp transformation rate in the region is 0.3 or more, At the same time, the surface roughness in the region on the insert surface is regulated to 0.2 μm or less by the arithmetic average roughness Ra at a cutoff value of 0.08 mm, so that the thermal crack resistance is excellent, and wet cutting or intermittent Even under high-load cutting conditions in which thermal shock or mechanical impact acts on the cutting edge, such as cutting, the occurrence and development of thermal cracks can be reliably and stably suppressed. Excellent deficient, also remarkable effect that is improved surface finish of the workpiece is achieved.

  Furthermore, according to the WC-based cemented carbide cutting insert of the invention in which the residual stress of the hard phase in the region is adjusted to 850 MPa or more by compression, the generation of thermal cracks and the suppression of growth are ensured, and the thermal crack resistance Can be further improved, and the fracture resistance against mechanical impact can be further improved.

  Further, not only in the region of the rake face but also in the flank face, the insert of the invention in which the hcp transformation rate and the surface roughness were adjusted in the same manner as described above, or the residual stress of the hard phase of the flank face was adjusted in the same manner as described above. According to the insert of the invention, it is possible to suppress the thermal crack from growing along the flank, further improve the fracture resistance against mechanical impact, and further improve the finished surface of the work material Accuracy can be obtained.

  Further, according to the method for manufacturing a cutting insert made of a WC-based cemented carbide according to the present invention, by performing wet blasting on the insert surface, the hcp transformation rate in the region is 0.3 or more. The surface roughness in the region can be smoothed so that the arithmetic average roughness Ra at a cutoff value of 0.08 mm is 0.2 μm or less. Since the compressive residual stress of the hard phase can be increased, the thermal crack resistance is excellent as described above, and the thermal shock and mechanical impact such as wet cutting and intermittent cutting are applied to the cutting edge. Even under cutting conditions, it is possible to reliably and stably prevent the occurrence and development of thermal cracks. Furthermore, it has excellent fracture resistance and excellent surface finish accuracy of the work material. The alloy cutting insert can be produced reliably and stably.

It is a perspective view which shows an example of the cutting insert which is an application object of this invention. It is a figure for demonstrating the specific area | region in the rake surface prescribed | regulated by this invention, and is a typical expanded sectional view in the XX line of FIG. It is a schematic diagram for demonstrating an example of the wet blast process applied in the manufacturing method of this invention. (A), (b) shows an example of the abrasive | polishing material used for the wet blast process in the manufacturing method of this invention, respectively, (a) is a photograph of a polygonal alumina abrasive | polishing material, (b) is spherical alumina. Show photos of abrasives,

  Hereinafter, the present invention will be described in more detail.

In the present invention, the insert substrate is made of a WC-based cemented carbide containing WC as a main component as a hard phase and 4 to 15% by mass of Co as a binder phase component. Here, if the content of Co, which is a binder phase component in the cemented carbide, is less than 4% by mass, the toughness decreases and the fracture resistance deteriorates, while the Co content exceeds 15% by mass. For example, since the wear resistance is lowered, the content of Co as a binder component in the WC-based cemented carbide is determined to be 4 to 15% by mass. The elements other than WC and Co are not particularly limited. In short, the main component of the hard phase is WC, and the content of Co in the binder phase is within the above range. Contains one or more of TiC, TiN, TaC, NbC, Cr ₃ C ₂ , VC, ZrC, ZrN, etc., each of which is a conventionally known minor additive component in cemented carbide, within a total amount of 30% by mass or less. It is permissible to do. In other words, the present invention can be applied to all WC-based cemented carbides in which the hard phase is mainly composed of WC and contains 4 to 15% by mass of Co as a binder phase until the tiredness is satisfied, and other components may be the same as those in the prior art. That's fine. In addition, WC which is the main component of the hard phase may be the remainder of the above-mentioned Co and other small additive components, as in the case of conventionally known WC-based cemented carbide, and the range of this WC is particularly limited. is not.

Here, an example of the shape of the insert to which the present invention is applied is shown in FIGS.
The insert 1 to which the present invention is applied includes a flank 2, a honing part (cutting edge part) 3, and a rake face 4, as well as an insert that has been widely used conventionally. A chip breaker portion 5 formed by a mold is formed. Here, the chip breaker part 5 is mainly composed of sintered skin. This sintered skin means a surface skin that has been sintered in the manufacturing process of the insert substrate, that is, a rough surface skin that has not been ground with a diamond grindstone or the like.
Here, the present invention is mainly applied to an ISO class M-class insert whose flank is often used on sintered skin, but at least a part of the flank is ground. Even if it is a G-class insert whose flank face is ground, etc., it can be applied without particular limitation as long as it has a chip breaker portion with a sintered skin on the rake face. Moreover, even if the entire surface of the chip breaker portion is not a sintered skin, it can also be applied to an insert in which at least a part of the chip breaker portion (particularly a portion close to the cutting edge) is a sintered skin.

  The inserts used in the present invention include substantially flat plate inserts such as approximately square, triangle, rhombus, hexagon, and round shape, or dog bone type or triangular grooving or threading inserts, inserts for various types of end mills, Various types such as a thick vertical blade insert can be used, and the negative and positive shapes can be applied without any particular problem.

  Furthermore, in the present invention, wet blasting is performed on at least a specific region of the insert surface to define the hcp transformation rate and surface roughness (and residual stress) in that region. FIG. Indicates. As shown in FIG. 2, the region P is a land portion forming a sintered skin within a range of at least 2 mm from the intersecting ridge line 6 between the flank 2 and the honing portion 3 toward the inside of the rake face 4. 7 and a region constituting the chip breaker unit 5.

Here, even when the chip breaker portion 5 of the sintered skin is formed beyond the position of 2 mm from the intersecting ridge line 6 toward the inside of the rake face 4, it reaches a minimum of 2 mm (however, the sintered skin The portion) is the region P, and at least the region is subjected to wet blasting so that the hcp transformation rate and surface roughness (and residual stress) in the region are within a predetermined range.
On the contrary, when the chip breaker portion 5 of the sintered skin is formed only to a position less than 2 mm from the intersecting ridge line 6 toward the inside of the rake face 4, or the inside of the rake face 4 from the intersecting ridge line 6 If the chip breaker portion 5 exists to a position exceeding 2 mm toward the surface, but the sintered skin is only formed to a position less than 2 mm from the intersecting ridge line 6 toward the inside of the rake face 4, the sintering Only the part of the skin is equivalent to the region P. In addition, since the honing portion 3 corresponding to the cutting edge portion is not usually sintered skin, the honing portion 3 is excluded from the region P. Furthermore, the land part 7 (a part of the rake face 4) between the honing part 3 and the chip breaker part 5 may be a ground surface, and in that case, that part is also not a sintered skin. Therefore, it is excluded from the region P. However, the above-described exclusion portion described here is merely described in the sense that it is not the essential region P. That is, in the actual wet blasting process, the above-described excluded portion is usually subjected to the wet blasting process. Of the above-described excluded portion, the portion other than the honing unit 3 is subjected to the wet blasting process. Of course, the hcp transformation rate and the surface roughness (and also the residual stress) may be within the predetermined range defined in the present invention, and it is usually desirable.

  In the present invention, the surface of the insert substrate is subjected to wet blasting, and at least the region P of the insert surface has a Co phase Co hcp transformation rate of 0.3 or more and at the same time a cutoff value of 0.08 mm. By smoothing the arithmetic average roughness Ra to 0.2 μm or less and further applying compressive residual stress to the WC hard phase on the surface in the above region, thermal shock such as wet cutting and interrupted cutting can be achieved. The cutting performance of WC-based cemented carbide cutting inserts over long-term use can be improved by suppressing the occurrence and development of thermal cracks under cutting conditions that affect Each target element will be described in detail by itemization.

Wet blasting:
In conventional inserts, compressive residual stress is applied to the insert surface by performing shot peening or sandblasting. However, in these methods, a relatively large spherical projection material having a diameter of 0.1 mm or more is used. In this case, excessive processing energy causes coarse cracks and chipping during insert manufacturing, which has been a factor in reducing product quality and product yield. Furthermore, since these relatively large spherical projection materials have a weak polishing action, there is also a drawback that the effect of improving the surface condition of the insert more smoothly is hardly seen.
In addition, when dry blasting is used instead of the above, the residual phenomenon of impurities due to biting into the insert surface of the spray abrasive is likely to occur, and such residual material on the insert surface is the starting point for the occurrence of thermal cracks during cutting. As a result, the chipping resistance and chipping resistance are insufficient, and the finished surface accuracy of the work material is also reduced by residual substances, resulting in cloudiness, mussels, fluffing, etc. In addition to being difficult to suppress the occurrence of the above, there is a problem that the dry blasting using the two kinds of fluids of the powder flow and the air flow has a small effect of applying the compressive residual stress to the insert.

Therefore, in the present invention, wet blasting is adopted as a means for simultaneously performing hcp transformation and surface smoothing of the binder phase Co on the insert surface and further imparting compressive residual stress without causing the above-described adverse effects.
By using the wet blasting process, a complicated shape (for example, a shape in which one surface is constituted by a set of a plurality of curved surfaces) is provided without giving the insert surface defects such as coarse cracks at the time of manufacturing that have occurred in the prior art. For insert inserts and chip breaker parts with a three-dimensional shape molded by a mold, the Co of the binder phase on the insert surface part is transformed into an hcp structure without impairing the shape, and at the same time the insert surface is smooth Made possible. Moreover, the performance of the cutting insert could be further improved dramatically by applying compressive residual stress.

  The wet blast treatment is a treatment in which a polishing liquid in which an abrasive such as alumina, zirconia, resin, glass, etc. having a particle size of about 10 to 100 μm is mixed with a liquid (usually water) is jetted onto the object by compressed air. As the wet blasting conditions in the present invention, for example, when alumina is used as the abrasive, the abrasive content in the polishing liquid is in the range of 15 to 60% by mass, and the injection pressure is 0.05. It is preferable to carry out at -0.3 MPa.

  The shape of the abrasive used is preferably polygonal abrasive grains. Here, as the alumina abrasive, the spherical alumina abrasive shown in FIG. 4B is generally used. However, the polygonal alumina abrasive shown in FIG. Compared to the shape of the alumina abrasive, the shape with an angular cutting edge formed by a cleaved surface has a large grinding force and a high smoothing effect, which is advantageous for improving the surface roughness of the insert surface. is there. On the other hand, when the abrasive is spherical, it is suitable for applying residual stress, but the grinding action is weak, and it takes a long time for wet blasting to finish the insert surface to the specified surface roughness. In addition to poor productivity, defects such as cracks due to excessive wet blasting may occur on the insert surface.

The outline of the wet blasting process in the present invention will be described with reference to FIG.
In FIG. 3 (a), the WC-based cemented carbide cutting insert base 10 is rotated while rotating around the axis while being sandwiched and held by a pair of rotating shafts 12 rotatable around the axis (O). With respect to the axial direction of the axis (O), for example, the polishing liquid G is sprayed onto the surface of the insert base 10 from two opposing blast guns 14 having an injection angle θ of 45 degrees, and wet blasting one by one. By performing the treatment, the entire surface of the insert base 10 can be treated uniformly.
On the other hand, with respect to the chip breaker surface of the insert substrate 10 (particularly, the region P: see FIG. 2) and the flank binder phase Co, the hcp crystal structure has a hcp transformation rate of 0.3 or more by wet blasting. Transformation is induced, and the surface is also smoothed.
When wet blasting is performed around the rake face including the region P, which is most important for improving thermal cracking resistance, the injection angle θ of the blast gun 14 with respect to the axial direction of the rotary shaft 12 is 0 degree or more and 45 degrees or less. Although set, the injection angle is adjusted by the chip breaker shape and the insert clearance angle. The number of blast guns 14 to be used is two in FIG. 3A, but one gun or a plurality of three or more guns may be used depending on the shape of the insert to be processed.
By using the apparatus having the above-described structure, it is possible to set individual injection conditions and perform an optimal wet blasting process on an insert base having various shapes and chip breakers.

Hcp transformation rate of the binder phase Co in the insert surface, particularly in the region P:
hcpCo suppresses the occurrence of thermal cracks from its crystal structure, and also suppresses the progress of thermal cracks even if they occur. And the tool life can be extended.
Here, in the present invention, the ratio of the peak intensity of hcpCo to the total peak intensity of hcpCo and fccCo is the diffraction peak intensity hcp [101 on the (101) plane of hcpCo on the insert surface measured by an X-ray diffraction apparatus. ] And the peak intensity fcc [200] on the (200) plane of fccCo,
hcp transformation rate = hcp [101] / (hcp [101] + fcc [200])
This formula defines the hcp transformation rate. And, by adjusting the wet blasting conditions so that the hcp transformation rate of the surface including at least the region P among the insert surfaces is 0.3 or more, the generation and propagation of thermal cracks can be reliably suppressed, and intermittent It has been found by detailed experiments by the present inventors that excellent thermal crack resistance can be exhibited in cutting and the like, the tool performance can be remarkably improved, and the life of the insert can be greatly extended. On the other hand, it was confirmed that when the hcp transformation rate in the region P is less than 0.3, these effects are not sufficiently exhibited.

Therefore, in the present invention, the hcp transformation rate at least on the insert surface in the region P is set to 0.3 or more. In the insert of the present invention, it is desirable that the hcp transformation rate is 0.3 or more not only for the region P included in the rake face but also for the flank face. Improvements can be made and the life of the inserts can be further extended.
The upper limit of the hcp transformation rate is not particularly defined, but in normal wet blasting, if the hcp transformation rate is increased to about 0.9 or more, the wet blasting process is overtreated and the surface roughness of the insert is deteriorated. Therefore, it is appropriate that the hcp transformation rate is about 0.9 or less in both the region P and the flank.

  In measuring the hcp transformation rate, etching was performed in advance using an aqueous NaOH solution, and the WC hard phase was electrolytically removed from the surface of the insert. This is because the peak of the (101) plane of WC, which is the WC hard phase, overlaps with the peak of the (101) plane of hcpCo, until the WC hard phase is removed from the insert outermost surface to a depth of about 20 μm. Then, after electrolytic etching using an aqueous NaOH solution, the peak intensity of Co in the binder phase on the insert surface portion can be measured with high accuracy by performing X-ray diffraction. Here, the etching depth is set to 20 μm from the outermost surface of the insert. Usually, the region that affects the thermal crack resistance of the insert is in the vicinity of the insert surface of about 20 μm from the outermost surface. It is an important part.

  In calculating the hcp transformation rate, the first peak hcp [101] that gives the strongest intensity was used for hcpCo, and the second peak fcc [200] was used for fccCo (JCPSD card No. 05-0727). And No. 15-0806). Here, the reason why fcc [111], which is the first peak of fccCo, is not used for the calculation of the hcp transformation rate is that hcp [002], which is the peak in the (2) plane of hcpCo, exists around the fcc [111] peak. This is because it is very difficult to completely separate both peaks.

Insert surface roughness:
In the present invention, by performing wet blasting on the insert surface, the Co in the binder phase in at least the region P of the insert surface portion is transformed into hcpCo, and at the same time, at least the surface in the region P is smoothed. Can do.
Thus, at the same time, the Co of the binder phase in at least the region P of the insert surface is hcp transformed to an hcp transformation rate of 0.3 or more, and at the same time, the arithmetic average roughness Ra is 0.2 μm or less at a cutoff value of 0.08 mm As described above, if the surface smoothness of the region P is increased, the surface defects that are the starting points of thermal cracks are reduced, and the effect of suppressing the occurrence of thermal cracks is obtained. In addition, if the surface roughness of the flank is also reduced at the same time, in addition to suppressing the growth of thermal cracks, the effect of improving the finished surface quality of the work material is also added, so it is included in the rake face It is preferable that the surface roughness is improved in both the region P and the flank. The flank surface roughness is preferably 0.2 μm or less in terms of arithmetic average roughness Ra at a cutoff value of 0.08 mm.

  Here, if the surface roughness of the region P or the flank included in the rake face exceeds 0.2 μm in terms of arithmetic average roughness Ra, improvement of the above-described heat cracking resistance, or finished surface quality is achieved. The effect of improvement will show a downward trend. Therefore, in the present invention, by performing wet blasting on the insert surface, at least the surface in the region P and further the flank surface are subjected to hcp transformation of the binder phase Co and at the same time smoothing the surface. The surface roughness of the surface was adjusted to be 0.2 μm or less in terms of arithmetic average roughness Ra at a cutoff value of 0.08 mm.

In addition, the same effect as described above can be obtained in the surface-coated WC-based cemented carbide cutting insert in which the insert is coated with a hard coating by physical vapor deposition (PVD), but depending on the state of the hard coating, The measured surface roughness may be larger than the substrate before coating.
In such a case, if the surface roughness of the insert measured from the top of the coating is 0.25 μm or less in arithmetic mean roughness Ra at a cutoff value of 0.08 mm, the cutting of the surface-coated WC-based cemented carbide cutting insert is performed. Even under conditions, it has been confirmed that there is an effect of improving heat cracking resistance.

Applying compressive residual stress to the WC hard phase on the insert surface:
In the present invention, the surface of the WC-base cemented carbide cutting insert substrate is wet-blasted to transform the binding phase Co of the insert surface portion (at least the surface in the region P) into hcpCo and smooth the surface. At the same time, it is desirable to apply a compressive residual stress of 850 MPa or more to the WC hard phase at least in the region P of the insert surface.
That is, when the value of the residual stress applied to the insert surface, particularly the WC hard phase on the surface in the region P is less than 850 MPa in compression, the improvement in fracture resistance including heat cracking resistance is not sufficient, but the compression residual If the stress value is 850 MPa or more, not only thermal shock such as interrupted cutting but also mechanical impact acts on the cutting edge, which shows excellent fracture resistance. The value of the residual stress applied to the WC hard phase in at least the surface portion in the region P included in the surface, more preferably in addition to the surface portion of the flank, was determined to be 850 MPa or more by compression.

  In addition, as described above, the same effect can be obtained in the case of an insert subjected to a surface coating treatment by physical vapor deposition, but in that case, since the hard coating itself generally has a compressive residual stress, The compressive residual stress of the substrate tends to decrease. However, when compressive residual stress of 850 MPa is applied to the insert before coating, if the residual stress of the WC hard phase of the substrate after coating is maintained at 450 MPa or more by compression, the surface-coated insert of the present invention can also be used. The effect is not impaired at all, and excellent fracture resistance against thermal shock and mechanical shock can be confirmed.

For the residual stress value applied to the WC hard phase on the insert surface, the X-ray evaluation of residual stress published by Yokendo Co., Ltd. (by Keisuke Tanaka, Kenji Suzuki, Yoshiaki Akiba), Chapter 6 Using a well-known sin ² ψ method described in (P99 to 105), measurement was performed with an X-ray diffraction apparatus.
That is, using the (211) plane of the WC hard phase having the hcp structure as the diffraction peak, the sin ² ψ method measurement range is equidistant in the range selected from 0 to 0.5 to 0 to 0.75. The measurement was performed by developing by 5 to 6 points and the parallel tilt method. The calculation was performed using 706 GPa as the Young's modulus of the WC hard phase and 0.190 as the Poisson's ratio.

Insert honing surface roughness:
The surface roughness of the honing part, which corresponds to the cutting edge part of a WC-base cemented carbide cutting insert, has a particularly large influence on the finished surface accuracy of the workpiece to be processed, and the insert cutting edge has a smooth surface. If so, it is possible to obtain even better finished surface accuracy.
Specifically, if the surface roughness of the cutting edge of the insert is 0.1 μm or less in terms of the arithmetic average roughness Ra at a cutoff value of 0.08 mm, a better work material finished surface can be formed.
Usually, the cutting edge portion of the insert is honed with an elastic grindstone, barrel, brush, etc. Especially, honing with a wet brush provides a high-quality processed surface and relatively various types of honing. It can be processed in a short time. However, if a wet blast process is performed after the honing process, the honing part is processed again by the wet blast process, and the shape and size of the honing part may change, and the original cutting performance may not be exhibited. In addition, in order to obtain an arithmetic average roughness Ra of 0.1 μm or less by wet blasting, it is necessary to change the particle size of the abrasive used and the injection conditions. In this case, the hcp transformation rate of the binder phase is Even if a sufficient value is not obtained or a sufficient value is obtained, there is a problem in productivity such as extension of processing time.

  Therefore, in the present invention, the hard phase is composed of a tungsten carbide-based cemented carbide containing WC as a main component and Co as a binder component and containing 4 to 15% by mass of Co, and includes a flank, a cutting edge, and a rake face, In addition, a wet blasting process as described above is performed as a wet blasting process on a tungsten carbide-based cemented carbide cutting insert base having a chip breaker portion formed of a sintered skin formed by a mold on at least a part of the rake face. After the treatment, it is desirable to perform a honing process on the cutting edge portion by honing (preferably brush honing, more preferably wet brush honing) as a honing process. By performing honing of the cutting edge portion after wet blasting in this way, an insert that maintains excellent finished surface accuracy of the work material for a long time can be obtained. In addition, if wet brush honing is performed after wet blasting, it is possible to take advantage of wet brush honing and obtain a honing surface with good surface roughness and precisely controlled to a predetermined shape with high productivity. It becomes possible.

  In addition, the measurement of arithmetic mean roughness Ra in an insert surface and a honing part surface follows JISB0601-1994 (2001). Here, the reason why the cut-off value is 0.08 mm is that the quality of the cutting surface is affected by the micro state of the surface of the cutting insert. This is to eliminate the influence of the undulation phenomenon (swell component) on the sintered skin of the insert base caused by the sintering deformation or the like that occurs during sintering.

Surface coating by physical vapor deposition:
The insert of the present invention has, on its surface, at least one element selected from the group consisting of group IVa element, group Va element, group VIa element, Al, Si, Y, Mn, Ni and S in the periodic table, and carbon. Surface-coated WC-based cemented carbide cutting insert formed by physical vapor deposition of a hard film composed of at least one layer or a compound of at least one element selected from the group consisting of nitrogen, oxygen and boron It can also be used.
Even when a hard coating is formed, the effect of the present invention is not impaired, and excellent cutting performance is demonstrated over a long period of use even under high-load cutting conditions in which thermal shock acts on the cutting edge. Thus, the tool life is extended.

  Examples of the present invention will be described below together with comparative examples. The following examples are for explaining specific embodiments of the present invention and effects thereof, and the configurations and conditions described in the examples do not limit the technical scope of the present invention. Of course.

[Example 1]
Using WC powder with an average particle size of 5μm, press molding a raw material powder blended so as to be 9% by mass of Co powder, 8% by mass of TiC powder, 8% by mass of TaC powder, 1% by mass of NbC powder, and the remaining WC After that, sintering was performed to produce an insert base body having a shape and dimensions specified in ISO standard / CNMG120408.
These insert bases were subjected to wet blasting with a spraying abrasive of polygonal alumina having a center particle diameter of 40 μm at spraying pressures of 0.3 MPa, 0.2 MPa and 0.1 MPa.
In the wet blast treatment, the jet abrasive liquid is prepared so that the alumina of the jet abrasive is mixed with water so that the content of the abrasive in the polishing liquid is 30% by mass, and the wet blast process shown in FIG. Using an apparatus, the spray angle was kept constant at 45 °, and wet blasting was performed so that the entire insert base was treated.
Then, for the cutting edge part, a nylon brush containing abrasive grains is used, and a waterfall type curved honing with a width measured from the rake face side of 0.05 mm and a width measured from the flank face side of 0.03 mm As a honing part, the inserts of Invention Examples 1 to 3 shown in Table 1 were produced.

About the produced insert, a sample for measurement was extracted for each manufacturing condition, and after etching under the above-described conditions, X-ray diffractometer was used as a X-ray diffractometer using PANaltical X 'Pert PRO MPD manufactured by Spectris Co., Ltd. A CuKα ray is used as the radiation source, and the peak intensity hcp [101] of the (101) plane of the hcpCo surface and the (200) of the fccCo at a substantially flat portion (portion corresponding to the region P) at the bottom of the rake face breaker. ) Surface peak intensity fcc [200] was measured, and the above-mentioned hcp transformation rate was calculated.
Table 1 shows the hcp transformation rate.
Next, in the rake face, the surface roughness of the bottom portion and the honing portion of the chip breaker portion corresponding to the region is JIS B0601-1994 (2001), with an arithmetic average roughness Ra at a cutoff value of 0.08 mm. It was measured.
Table 1 shows the measured values of the surface roughness Ra at each part.
In addition, about the hcp transformation rate and the surface roughness, although the value of the flank was also measured, it became a value almost the same as the measured value of the rake face (breaker bottom) (not shown). This is presumably because the wet blast treatment was performed so that the same action was applied to the flank and rake face because the injection angle during the wet blast treatment was 45 °.

Next, the compressive residual stress of the WC hard phase was measured at the flank face of the inserts of Examples 1 to 3 of the present invention.
For the measurement, Spectraly Co., Ltd. PANalytical X 'Pert PRO MPD was used as the X-ray diffraction apparatus, CuKα rays were used as the X-ray source, and the residual stress calculation software used for the measurement was X' Pert. Calculated with High Score Plus.
In the inserts of Examples 1 to 3 of the present invention, the rake face including the region P is a curved surface having a chip breaker, and thus the flat surface necessary for the X-ray diffraction measurement cannot be secured for the region P. Although the residual stress cannot be measured directly, in Example 1, the injection angle during wet blasting is set to 45 °, and processing is performed so that basically the same action is applied to the flank and rake face. Therefore, the rake face, in particular, the region P, that is, the land portion near the cutting edge that is positioned substantially perpendicular to the flank and the bottom of the breaker (if a chip is generated due to mechanical shock, the rake face has a land close to the cutting edge. The residual stress at the bottom of the deepest breaker that is curved in a partial or concave shape is important for improving fracture resistance.) The residual stress is considered to be roughly equivalent to the residual stress measured on the flank. Residual stress concert shall be possible to substitute the residual stresses measured for flank.
Table 1 shows the measured residual stress values.

For comparison, steel having an average diameter of 0.4 mm is used instead of wet blasting for Comparative Example 1 in which the cutting insert having the same composition, shape and dimensions as the inserts of Examples 1 to 3 of the present invention is not subjected to wet blasting. Comparative example 2 (corresponding to the shot peening treatment condition of Patent Document 2) in which shot peening was performed under the condition of projecting a sphere at a speed of 60 m / s, the same alumina as used in the wet blast treatment, and a projection pressure of 0 Comparative Example 3 in which dry blasting was performed at 3 MPa and Comparative Example 4 in which the wet blast injection pressure was lowered were produced. For these Comparative Examples 1 to 4, the hcp transformation rate in the region P of the rake face, the surface roughness of the region P (breaker bottom portion) of the rake face, and the honing portion in the same manner as the inventive examples 1 to 3 The surface roughness and residual stress on the flank were measured.
Finally, the appearance surface state was observed for all the inserts of Examples 1 to 3 and Comparative Examples 1 to 4 using an optical microscope. As for the area ratio of the deposit, when the deposit was observed, three 200 × 200 μm observation areas were measured by image analysis, and the average value was taken as the area ratio.
The results are shown in Table 1.

According to Table 1, all of the inventive examples 1 to 3 subjected to the wet blast treatment were performed while the hcp transformation rate of the region P included in the rake face exceeded 0.3. In Comparative Example 1, the hcp transformation rate is 0 (zero), and hcpCo does not exist. In the comparative example 2 by the shot peening process, the hcp transformation rate is 0.71, and the hcp transformation rate is equal to or higher than the inventive examples 1 to 3. Further, in Comparative Example 4 in which the injection pressure was lowered while performing the wet blast treatment, the hcp transformation rate was 0.25, which was less than the lower limit (0.3) defined in the present invention.
Inventive Examples 1 to 3 had a large hcp transformation rate as compared with Comparative Example 3 by dry blasting. This is because wet blasting using three kinds of fluids (powder flow, air flow, water flow) This is probably because the hcp transformation is further promoted by the mass of water contained in the jet polishing liquid as compared with the dry blast treatment of the seed fluid (powder flow, airflow).
Moreover, about the invention examples 1-3, if the injection pressure of wet blasting was raised, the tendency for an hcp transformation rate to become large was seen.
As for the surface roughness of the region P included in the rake face, Examples 1-3 of the present invention subjected to the wet blast treatment are compared with Comparative Example 1 where the treatment is not performed and Comparative Example 2 where the shot peening treatment is performed. In addition, the smoothness is greatly improved. In addition, regarding the surface roughness of the honing portion, Examples 1 to 3 of the present invention have smoother values than Comparative Examples 1 and 2. This is presumed to be because the surface roughness is further improved because the brush honing is further applied to the insert that has been previously obtained a smooth surface by wet blasting.

As for the residual stress, the present invention examples 1 to 3 subjected to the wet blast treatment and the comparative example 2 by the shot peening treatment are applied with a very large compressive residual stress as compared with the comparative example 1. Comparative Example 3 subjected to the dry blasting process and Comparative Example 4 having a low jet pressure of the wet blasting process are given compressive residual stress as compared with Comparative Example 1, but Examples 1-3 of the present invention. Compared to Comparative Example 2, the compressive residual stress value is small.
Further, regarding the surface state of the insert, Examples 1 to 3 of the present invention and Comparative Example 4 did not show defects such as deposits and cracks, but for Comparative Example 2, the surface of about 20% of the insert produced. Large cracks and cracks that were thought to have occurred during shot peening were observed. When these inserts are used for cutting, the possibility of breakage is extremely high, and the degree of chipping and cracking that occurred was a size that was judged as defective in normal production. It was decided not to use it. Regarding Comparative Example 3, a phenomenon was confirmed in which the alumina abrasive during dry blasting adhered to the insert surface and was present.

Next, this insert was subjected to a cutting test under the following conditions.
<< Cutting Test 1 >>
Work material: JIS-SNCM439 round bar,
Cutting speed: 160 m / min,
Feeding speed: 0.4mm / rev,
Cutting depth: 1.5mm
Wet continuous cutting was performed under the conditions described above, and the flank wear width after 8 minutes of actual machining time, the state of the cutting edge, and the finished surface accuracy of the work material were evaluated.
<< Cutting Test 2 >>
Work material: JIS-SNCM439 round bar with grooves (6 grooves in the longitudinal direction),
Cutting speed: 140 m / min,
Feed rate: 0.2 to 0.4 mm / rev,
Cutting depth: 3mm
Feed rate 0.2mm / rev
Under the above conditions, wet intermittent cutting was performed for 2 minutes at the upper limit, and the feed rate was increased by 0.02 mm / rev until the cutting edge was broken, and the same cutting was repeated. The upper limit of the feed rate was 0.4 mm / rev.

Table 2 shows the flank wear width, the state of the cutting edge, the finished surface accuracy in the cutting test 1, and the feed rate at which the cutting edge in the cutting test 2 is broken.

According to Table 2, in wet continuous cutting of the cutting test 1, the inventive examples 1 to 3 had a smaller flank wear width in any of the comparative examples 1 in which the wet blast treatment was not performed. In addition, compared with Examples 1 to 3 of the present invention, Comparative Examples 2 and 3 were also inferior in the flank wear width, but these were Examples 1-3 of the present invention were normal wear. On the other hand, all the comparative examples are caused by chipping (and minute chipping) on the cutting edge.
As for the finished surface accuracy, all of Examples 1 to 3 of the present invention obtained a glossy good finished surface, but none of the comparative examples obtained a good finished surface. Regarding Comparative Examples 1 and 2, since the surface roughness of the insert is rough, and Comparative Example 1 has an hcp transformation rate of 0 (zero), chipping occurs in the cutting edge to deteriorate the finished surface. It is considered that the residual material itself on the insert surface itself and chipping which is considered to be caused by this occurred, and the finished surface was deteriorated. Further, in Comparative Example 4 having a low hcp transformation rate, chipping occurred in the cutting edge, and a good finished surface could not be obtained.

In the wet intermittent cutting of the cutting test 2, Examples 1 to 3 of the present invention can maintain a good cutting state with no cutting edge seen even when the feed rate is increased to the upper limit of 0.4 mm / rev. did it.
On the other hand, in Comparative Example 1 in which wet blasting was not performed, a chipping occurred that appeared to be due to thermal cracks at the cutting edge at a feed rate of 0.2 mm / rev at the initial stage of cutting, and cutting was terminated. In Comparative Example 2 subjected to the shot peening treatment, a defect occurred at 0.3 mm / rev. This is probably because although the hcp transformation rate is high, the surface roughness of the rake face is rough, so that a minute thermal crack is generated in the cutting edge, leading to a defect.
Further, as described above, in Comparative Example 2, there are many solids that are chipped and cracked on the insert surface during the shot peening process, and if the same cutting is performed with these inserts, the chip is lost at the initial feed rate. Is expected to have occurred.
In Comparative Example 3 in which the dry blast treatment was performed, a defect occurred relatively early at a feed rate of 0.24 mm / rev. This is presumably because the hcp transformation rate was as low as 0.26, and thermal cracks occurred and progressed starting from the residual abrasive on the insert surface.
Further, in Comparative Example 4, the cutting was terminated due to a defect grown from a thermal crack at a feed rate of 0.26 mm / rev. In Comparative Example 4, the hcp transformation rate is as low as less than 0.3, and it is considered that the effect of suppressing the occurrence and growth of thermal cracks was not sufficient.

[Example 2]
Mitsubishi Materials uses a WC powder with an average particle size of 1 μm, press-molds the raw material powder blended so that the mass composition is 10% by mass of Co powder, 1% by mass of Cr ₃ C ₂ powder, and the remaining WC. An insert base body having a shape and dimensions prescribed for an insert (Mitsubishi Material insert model number: SEMT13T3AGSN-JM) used for a front face cutting cutter (Mitsubishi Materials tool model number: ASX445R12506E) manufactured by the company was manufactured.
Next, wet blasting was performed under the conditions shown in Table 3.
In the wet blasting process, polygonal alumina having a center particle diameter of 40 μm of the spray abrasive is mixed with water to prepare a spray polishing liquid so that the content of the abrasive in the polishing liquid is 30% by mass, and wet blasting. The spray angle was set to 15 °, and only the blast gun on the insert rake face side was used, and wet blast treatment was performed so that at least the insert rake face including the region P was treated.
Thereafter, a nylon brush containing abrasive grains was used, and waterfall type curved honing with a width measured from the rake face side of 0.06 mm and a width measured from the flank face side of 0.03 mm was applied by wet treatment. .
For comparison, a conventional insert (Comparative Example 5) without wet blasting and an insert (Comparative Example 6) with a reduced wet blast injection pressure were prepared.

Using the same X-ray diffractometer as that used in Example 1, the predetermined peak intensity on the surface of the region P of the insert was measured, and the hcp transformation rate was calculated. Further, the residual stress of the WC hard phase was measured at a flat portion in the region P of the rake face. Furthermore, according to JIS B0601-1994 (2001), the surface roughness of the said area | region P of a rake face, and the honing part was measured by arithmetic mean roughness Ra in the cut-off value of 0.08 mm.
Table 3 shows the measured hcp transformation rate, surface roughness value, and residual stress value.

According to Table 3, Examples 4 to 6 of the present invention subjected to the wet blast treatment were subjected to the wet blast treatment while the hcp transformation rate of the region P on the rake face was 0.3 or more. No Comparative Example 5 is 0, and Comparative Example 6 with the wet blast injection pressure lowered is 0.19, both of which are less than 0.3.
Moreover, although it turns out that the surface roughness of insert is improving by wet blasting, this invention example 4-6 which performed the brush honing after wet blasting is comparative example 5 which has not performed wet blasting. In comparison, it can be seen that the surface roughness of the honing portion is also improved. This is presumed that a smoother surface was obtained than when brush honing was directly applied to the normal sintered skin because the brush honing was performed in a place where the insert surface roughness was previously improved by wet blasting. The
Further, regarding the residual stress on the rake face, Examples 4 to 6 of the present invention all have compressive residual stress values exceeding 1000 MPa. In Comparative Example 5 in which the wet blast treatment was not performed, only a slight amount of compressive stress remained, and in Comparative Example 6 in which the spray pressure of the wet blast was lowered, a residual stress of 417 MPa was applied by compression. Compared with Invention Examples 4-6, the value is small.

Next, a cutting test was performed under the following conditions to evaluate the insert performance.
<< Cutting Test 3 >>
Work material: JIS-SNCM439,
Cutting speed: 150 m / min,
Feed rate per blade: 0.2 mm / tooth,
Cutting depth: 2mm
Wet face milling was performed under the conditions described above, and the wear width of the flank face on the main cutting edge after 2.5 m cutting, the number of generated thermal cracks and the state thereof were evaluated.
Table 4 shows the flank wear width of the main cutting edge, the number of thermal cracks and their states.

If the number of the thermal cracks which generate | occur | produced in the main cutting edge after cutting in Table 4 is seen, while the comparative example 5 is seven, this invention example 4-6 is four or less and is about 1/2. is there. In particular, in Invention Examples 4 and 5 in which the hcp transformation rate exceeded 0.5, the number of thermal cracks was 3, and the thermal crack resistance was greatly improved.
Further, in any of the inventive examples 4 to 6, the generated thermal crack was shallow and the opening was mild, and the comparative example 5 was wide open, and compared with the occurrence of the deep thermal crack, It can be seen that the growth of cracks is also suppressed.
In Comparative Example 6 in which the spray pressure of the wet blast treatment was lowered, the number of thermal cracks was 5, and the form was deep thermal cracks with a wide open mouth, and the hcp transformation rate was small, resulting in thermal crack resistance. Can be said to be insufficient.
The flank wear width of the main cutting edge is smaller in Comparative Examples 5 to 6 in which the wet blasting treatment is not applied and Comparative Example 6 in which the injection pressure is small, and the invention examples 4 to 6 have a smaller width and an improvement in tool life is seen. . This is due to the number, width, and depth of thermal cracks generated in the aforementioned cutting edge.

  [Example 3]

The raw material powder having the same composition as that of Example 2 was press-molded and then sintered to produce an insert substrate having a shape and dimensions specified in ISO standard: CNMG120408. Next, honing and wet blasting were performed in the order and conditions shown in Table 5.
For the honing process, a nylon brush containing abrasive grains was used, and round honing with a width of 0.05 mm was performed by a wet treatment. In the wet blast treatment, the entire surface of the insert was treated with a polishing liquid using a polygonal alumina having a center particle diameter of 50 μm as an abrasive at an injection angle of 45 °.
For comparison, a conventional insert (Comparative Example 7) without wet blasting was also produced.
Regarding these inserts, the surface roughness (rake face and honing part) and the residual stress (flank face) of the WC hard phase in the surface part were measured.
Further, after performing the etching process under the above-mentioned conditions to remove the WC hard phase of the substrate, the above-mentioned peak intensity is measured by an X-ray diffraction apparatus at an almost flat portion of the chip breaker portion of the rake face, and the hcp transformation is performed. The rate was calculated.
Table 5 shows the measurement results.

Next, a hard coating of TiAlN having an average film thickness of 3 μm was formed on the insert surface by arc ion plating among physical vapor deposition methods. Regarding these inserts, the surface roughness and the residual stress of the WC hard phase in the insert base part under the coating were measured again.
Next, after removing the hard coating and the WC hard phase of the substrate by etching, the peak intensity is re-measured by an X-ray diffraction apparatus at the substantially flat portion of the bottom of the chip breaker on the rake face, and the hcp transformation rate is determined. Calculated.
Table 5 shows the measured surface roughness, residual stress value, and hcp transformation rate.

According to Table 5, the present invention examples 7 to 10 subjected to the wet blasting treatment each have an hcp transformation rate of 0.3 or more. Moreover, the hcp transformation rate is substantially the same before and after the coating treatment, and it can be seen that the coating treatment by physical vapor deposition does not affect the hcp transformation rate.
As for the insert surface roughness, the smoothness of the insert substrate was improved by wet blasting, but the surface roughness of any insert deteriorated after the hard coating was applied. However, when Examples 7 to 10 of the present invention were compared with Comparative Example 7 which was not subjected to wet blasting, it was found that the effect of wet blasting was maintained even after coating.
Inventive Examples 9 and 10 in which brush honing is performed after wet blasting, the surface roughness of the honing part is further improved and the smooth cutting edge is compared with Inventive Examples 7 and 8 in which wet blasting is performed after brush honing. The same tendency was observed after coating.
As for the residual stress of the WC hard phase, Examples 7 to 10 of the present invention are given a larger compressive residual stress than Comparative Example 7, but after the coating, the compressive residual stress value itself is higher than before the hard coating is coated. Is getting smaller. This is presumably because a hard coating by a physical vapor deposition method having compressive residual stress generally exerted a tensile action on the insert substrate.

Next, a cutting test was performed under the following conditions to evaluate the insert performance.
<< Cutting Test 4 >>
Work material: JIS-SNCM439 grooved round bar (6 grooves in the longitudinal direction),
Cutting speed: 200 m / min,
Feed rate: 0.15 mm / rev,
Cutting depth: 2mm
Wet intermittent cutting was performed according to the above conditions, and the actual cutting time until cutting edge replacement was evaluated. The time until the cutting edge was replaced was the time until chipping or chipping occurred on the used cutting edge and actual cutting could not be continued. Moreover, when normal cutting was performed, it was set as the time to reach the flank wear width of 0.2 mm.
<< Cutting Test 5 >>
Work material: JIS-SUS304 round bar,
Cutting speed: 200 m / min,
Feed rate: 0.3 mm / rev,
Cutting depth: 1,5mm
Wet continuous cutting was performed under the conditions described above, and the flank wear width and work surface finish accuracy after 10 minutes of actual machining time were evaluated.
Table 6 shows the actual cutting time until the cutting edge replacement in the cutting test 4 and the reason for the cutting edge replacement, and the flank wear width and the work surface finish accuracy in the cutting test 5.

According to Table 6, in the wet intermittent test of the cutting test 4, Examples 7 to 10 of the present invention subjected to the wet blasting process maintain a good cutting state over a long period without causing a defect in the cutting edge. The blade was replaced due to normal wear. On the other hand, in Comparative Example 7 in which the wet blasting treatment was not performed, the cutting edge was deficient due to the thermal crack, and the cutting was finished early.
Further, also in the wet continuous cutting of the cutting test 5, the flank wear amount 10 minutes after the start of cutting is compared with Comparative Example 6 where the wet blast treatment is not performed, and the inventive examples 7 to 10 have a flank wear width. As a result, the tool life could be extended.
Inventive Examples 9 and 10 in which brush honing was performed after wet blasting, compared to Inventive Examples 7 and 8 in which the order of these steps was changed, even if the same wet blast injection pressures were compared, the flank wear width was There is a small tendency. This is considered to be caused by maintaining a proper shape / size and good surface roughness for the honing part having a large influence on the cutting performance because brush honing is used as a post-process.

In addition, regarding the finished surface of the work material after the end of cutting, the inventive examples 7 to 10 which were subjected to the wet blasting treatment were able to obtain a good finished surface without white turbidity. Among them, brush honing was performed after the wet blasting. Inventive Examples 9 and 10 were able to obtain a glossy and better finished surface as compared with Inventive Examples 7 and 8. This is also assumed to be because the honing shape is appropriate and the smoothness thereof is further improved.
On the other hand, in Comparative Example 7 where the wet blast treatment was not performed, a finished surface free of cloudiness was obtained at the initial stage of cutting, but the surface of the work material began to become clouded 2 minutes after the start of cutting. This is because, in Comparative Example 7 where the wet blasting treatment is not performed, when the tool wear progresses, the insert surface portion having inferior smoothness becomes a cutting edge, so that welding of the work material is likely to occur. it is conceivable that.

  According to the present invention, even under cutting conditions in which thermal shock acts on the cutting edge, such as wet cutting, intermittent cutting, or milling, crack generation and progress are prevented, and fracture resistance is improved. WC-based cemented carbide cutting inserts that enable the formation of high-quality cutting surfaces with excellent surface finish accuracy of the cutting materials can be obtained, so that the energy saving and cost reduction of cutting operations can be fully satisfied. can do.

DESCRIPTION OF SYMBOLS 1 Cutting insert made from a tungsten carbide base cemented carbide 2 Flank 3 Honing part 4 Rake face 5 Chip breaker part 6 Cross ridge line 7 Land part 10 Insert base 12 Rotating shaft 14 Blast gun G Polishing fluid P Area | theta (theta) Inclination angle

Claims (13)

The hard phase is made of a tungsten carbide-based cemented carbide containing WC as a main component and Co as a binder phase component in an amount of 4 to 15% by mass, and includes a flank, a honing portion, and a rake face, and at least one of the rake faces. In a tungsten carbide-based cemented carbide cutting insert having a chip breaker portion formed by a mold in the portion;
The peak intensity value obtained from the (101) plane of Co having a hexagonal structure (hereinafter referred to as “hcpCo”) when X-ray diffraction is performed on the binder phase Co on the insert surface portion is represented by hcp [101]. The peak intensity value of hcpCo relative to the total peak intensity of hcpCo and fccCo, where fcc [200] is the peak intensity value obtained from the (200) plane of Co (hereinafter referred to as “fccCo”) having a face-centered cubic structure. The ratio is defined by the following formula (1) as the hcp transformation rate,
Of the insert surface portion, a chip breaker portion is formed by subjecting the sintered skin to wet blasting within a range of at least 2 mm from the intersecting ridge line between the flank face and the honing portion toward the inside of the rake face. The hcp transformation rate in the region is 0.3 or more,
In addition, the tungsten carbide based cemented carbide cutting insert is characterized in that the surface roughness in the region is 0.2 μm or less in arithmetic mean roughness Ra at a cutoff value of 0.08 mm.
hcp transformation rate = hcp [101] / (hcp [101] + fcc [200]) (1)   2. The tungsten carbide-based cemented carbide cutting insert according to claim 1, wherein the residual stress of the hard phase in at least the region of the insert surface portion is 850 MPa or more in compression.   Of the insert surface portion, the hcp transformation rate at the flank is 0.3 or more, and the surface roughness of the flank is 0.2 μm or less in arithmetic mean roughness Ra at a cutoff value of 0.08 mm. The tungsten carbide-based cemented carbide cutting insert according to claim 1, wherein the cutting insert is made of tungsten carbide.   The tungsten carbide-based cemented carbide cutting insert according to claim 2, wherein the residual stress of the hard phase on the flank surface of the insert surface portion is 850 MPa or more in compression.   The surface roughness of the honing part of the insert is not more than 0.1 μm in terms of arithmetic average roughness Ra at a cutoff value of 0.08 mm. A tungsten carbide-based cemented carbide cutting insert as described in the paragraph.   In the surface of the tungsten carbide-based cemented carbide cutting insert according to any one of claims 1 to 5, a group IVa element, a group Va element, a group VIa element, Al, Si, One or more layers composed of a compound comprising at least one element selected from the group consisting of Y, Mn, Ni and S and at least one element selected from the group consisting of carbon, nitrogen, oxygen and boron A surface-coated tungsten carbide based cemented carbide cutting insert, characterized in that the hard coating is formed by physical vapor deposition (PVD method). The hard phase is composed of a tungsten carbide-based cemented carbide containing WC as a main component and Co as a binder phase component in an amount of 4 to 15% by mass, and includes a flank, a cutting edge, and a rake face, and at least of the rake face. In producing a tungsten carbide-based cemented carbide cutting insert using a tungsten carbide-based cemented carbide cutting insert base part having a chip breaker portion formed of a sintered skin formed by a mold;
Of the surface portion of the tungsten carbide-based cemented carbide cutting insert substrate, a chip forming a sintered skin at least within a range of 2 mm or less from the intersecting ridge line between the flank and the honing portion toward the inside of the rake face. In the region constituting the breaker part, a wet blasting process for performing wet blasting,
A honing step of performing honing on the cutting edge portion of the surface of the tungsten carbide based cemented carbide cutting insert base;
It is obtained from the (101) plane of the hexagonal structure Co (hereinafter referred to as “hcpCo”) when X-ray diffraction is performed on the binding phase Co in the surface portion after the wet blasting process and the honing process are completed. The peak intensity value is hcp [101], and the peak intensity value obtained from the (200) plane of Co having a face-centered cubic structure (hereinafter referred to as “fccCo”) is fcc [200]. The ratio of the peak intensity of hcpCo to the total peak intensity is defined by the formula (1) as the hcp transformation rate,
The hcp transformation rate at least in the region of the insert surface portion is 0.3 or more,
Moreover, a tungsten carbide-based cemented carbide cutting insert having a surface roughness at least in the region of the insert surface portion, which is an arithmetic average roughness Ra at a cutoff value of 0.08 mm, is 0.2 μm or less. A method for manufacturing a tungsten carbide-based cemented carbide cutting insert.   In the wet blasting process, a polishing liquid is sprayed from at least one blast gun while rotating around the axis while holding the insert base between a pair of rotating shafts rotatable around the axis. The method for producing a tungsten carbide-based cemented carbide cutting insert according to claim 7, wherein wet blasting is performed.   In the wet blasting step, a wet blasting process is performed by injecting a polishing liquid from a blast gun at an injection angle of 0 degrees or more and 60 degrees or less with respect to an axial direction of the rotating shaft that rotatably inserts the insert base. A method for producing a tungsten carbide-based cemented carbide cutting insert according to claim 8.   10. The method for manufacturing a tungsten carbide-based cemented carbide cutting insert according to claim 9, wherein in the wet blasting step, the injection angle is 40 degrees or more and 50 degrees or less.   The method for manufacturing a tungsten carbide-based cemented carbide cutting insert according to any one of claims 7 to 10, wherein the honing step is performed after the wet blasting step.   The method for manufacturing a tungsten carbide-based cemented carbide cutting insert according to any one of claims 7 to 11, wherein the honing process in the honing step is performed by wet brush honing.   A hard coating is coated on the surface of a tungsten carbide-based cemented carbide cutting insert manufactured by the manufacturing method according to any one of claims 7 to 12 by a physical vapor deposition method (PVD method). A method for producing a surface-coated tungsten carbide-based cemented carbide cutting insert.

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