JP2007268647A - End mill - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an end mill, preventing a tip from dislocating from a tool body, having a long life and stability and easily adjusting the length of the neck part to adjust the depth of working. <P>SOLUTION: This end mill 10 includes: the substantially cylindrical tip 14 constructed by integrally forming a cubic boron nitride sintered body layer 14A and a cemented carbide layer 14B; and a tool body 15 connected to the cemented carbide layer 14B on the rear end side of the tip 14 coaxially with the tip 14, wherein a cutting blade is formed at the tip of the tip 14. A fitting shaft part 16 is formed at least on the tip side of the tool body 15, the outside diameter of the tip face of the fitting shaft part 16 is the same as the outside diameter of the rear end face of the tip 14, and a joint part 20 is disposed between the rear end face of the tip 14 and the tip face of the fitting shaft part 16. The joint part 20 is a bonding layer including a diffusion layer where metal element is diffused to at leat one of the tip 14 and the tool body 15. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an end mill which is a cutting tool used for machining a die.

  In recent years, an end mill using a cubic boron nitride sintered body (hereinafter referred to as cBN) has been provided as a tool for processing a mold used for manufacturing a casing of a mobile phone or the like. cBN has the second most hardness after diamond and has low chemical reactivity with metals such as Fe, Co, and Ni, and is therefore the most suitable material for mold processing. End mills using cBN are attracting attention because they can cut hard hardened steel of HRC60 or higher, which could not be machined in the past, and can provide high-precision, long-life molds. In particular, in an end mill with a small diameter of φ3 or less, future demand is expected to increase with the complexity and miniaturization of the mold shape.

  Further, in current machining of molds, cutting is performed by automatic operation, and the end mill may be used continuously for a long time (for example, 40 hours). If the end mill suddenly breaks during automatic operation, the mold in the middle of machining cannot be reworked and becomes defective, resulting in a significant decrease in productivity. The end mill has a long and stable life. It is required to be.

As an end mill using conventional cBN, for example, those described in Patent Document 1 and Patent Document 2 have been proposed.
The end mill described in Patent Literature 1 is a small-diameter ball end mill, a cutting blade portion having a ball blade formed at the tip thereof, a neck portion having an outer diameter substantially equal to the outer diameter of the cutting blade portion, and a cutting blade And a shank portion having a diameter larger than that of the neck portion and the neck portion, and the processing depth at which the end mill can be processed is determined by the lengths of the cutting edge portion and the neck portion.

  The end mill is composed of a tip disposed at the tip and a tool body connected to the tip. The chip has a laminated structure of a cBN layer and a cemented carbide layer, and a ball blade is formed on the cBN layer. The tool body is made of a cemented carbide, and a tip mounting recess is formed at the tip. The rear end (the cemented carbide layer side) of the chip is fitted into the recess, and the cemented carbide layer of the chip and the recess of the tool body are joined by a brazing material.

  The chip is manufactured by the following procedure. Put powder mixed with cubic boron nitride particles and titanium nitride or titanium carbide particles as binder on top of the substrate made of cemented carbide, and load it into the pressure space of the ultra high pressure sintering machine. A chip material in which a cemented carbide layer and a cBN layer are integrally formed is obtained by heating to about 1300 ° C. with a high pressure of about 4 GPa applied. A chip can be obtained by cutting this chip material into a cylindrical shape by a discharge wire cut.

On the other hand, the end mill described in Patent Document 2 is a small-diameter ball end mill, and includes a cutting edge part, a neck part, and a shank part, and the processing depth that can be processed by the end mill depends on the length of the cutting edge part and the neck part. It is determined.
In this ball end mill, the tip is brazed directly to the tip surface of the tool body. That is, the tip composed of the cBN layer and the cemented carbide layer is joined to the tip of the tool body made of the cemented carbide via the brazing material.
JP 2004-268202 A JP 2002-144131 A

  By the way, in the end mill described in Patent Document 1, since the tip is inserted into the recess of the tool body and brazed, the brazing area is secured and the tip and the tool body can be firmly fixed. However, in order to hold the insert in the recess of the tool body, it is necessary to make the inner diameter of the recess at the tip of the tool body larger than the outer diameter of the insert, and the lengths of the cutting edge and neck are determined by the length of the insert. Will be. That is, in the ball end mill having the above-described configuration, in order to cope with various machining depths, it is necessary to manufacture a chip material with a size corresponding to the machining depth. As described above, when the chip material is enlarged, the number of chip materials that can be loaded in the pressure space of the ultra-high pressure sintering apparatus is limited.

  On the other hand, in the end mill described in Patent Document 2, since the tip is brazed to the tip surface of the tool body, the length of the neck can be adjusted by machining the tool body, and the machining depth can be adjusted. It is possible to provide a suitable end mill. However, since the rear end surface of the tip and the tip end surface of the tool body are brazed, the tip is not able to be firmly fixed because the brazing area is small, and the tip may come off due to cutting resistance during cutting. . In particular, in a small-diameter end mill having a diameter of 3 or less, it is difficult to construct an end mill because the brazing area is too small.

In the end mill described in Patent Document 2, a ceramic coating is applied to the portion where the cutting edge at the tip is formed, and depending on the coating processing conditions, the brazing material melts when coated in a brazed state. There was a risk of it. For this reason, the tip is brazed to the tool body after coating only the tip.
Moreover, in the end mill described in patent document 2, the brazing position is the rearmost end of the neck. However, the rearmost end of the neck is a portion where bending stress due to cutting resistance is most concentrated, and there is a possibility that the tip may come off due to cutting resistance.

  Since brazing is a method in which a once melted brazing material is solidified, a void called a nest defect may be generated inside the solidified brazing material due to volume shrinkage during solidification. In particular, in a small-diameter end mill having a diameter of φ3 or less, the bonding area is very small. Since the presence of nest defects inside the brazing material is indistinguishable in appearance, there is a possibility that a ball end mill having the above-described configuration will be on the market with a significantly short life.

  The present invention has been made in view of the above circumstances, and is an end mill that can adjust the processing depth by easily adjusting the length of the neck while maintaining the long life without the tip being detached from the tool body. The purpose is to provide.

  In order to solve the above-mentioned problems, the present invention provides a substantially cylindrical chip in which a cubic boron nitride sintered body layer and a cemented carbide layer are integrally molded, A tool body connected to the cemented carbide layer on the end side, and an end mill having a cutting edge formed at a tip portion of the tip, and an attachment shaft portion is formed at least on the tip side of the tool body. And the outer diameter of the front end surface of the mounting shaft portion is the same as the outer diameter of the rear end surface of the chip, and a joint portion is provided between the rear end surface of the chip and the front end surface of the mounting shaft portion. The bonding portion is arranged to be a bonding layer including a diffusion layer in which a metal element diffuses into at least one of the tip and the tool body.

In the end mill having this configuration, the attachment shaft portion is formed at the tip of the tool body, and the joint portion is formed between the tip surface of the attachment shaft portion and the rear end surface of the chip. There is no concentration of stress.
Further, since the joint portion is composed of a diffusion layer in which a metal element is diffused, the joint strength is remarkably higher than that of joining by conventional brazing, and the tip and the tool body can be firmly fixed. Furthermore, in the step of diffusing the metal element, since the diffusion phenomenon in the solid is used, the metal is not melted in the joining process, so that the joining layer of the end mill is likely to be generated inside the brazing material. There are no nest defects.

  Therefore, in the end mill having the above-described configuration, the stress and the tool main body can be firmly fixed without concentrating stress on the joint portion, so that the tip can be prevented from coming off during cutting. In particular, even if the joining area is small, such as a small-diameter end mill having a diameter of 3 or less, it is effective because the tip and the tool body can be securely fixed.

  In addition, since the cemented carbide layer of the tip and the tool body made of cemented carbide are integrally formed, it is possible to reduce the size of the cemented carbide layer of the tip, Since the size can be reduced, the manufacturing cost can be greatly reduced. Furthermore, since the neck length can be adjusted by the shape of the shank, an end mill corresponding to the processing depth can be easily provided.

  Here, by setting the length L from the tip of the chip to the joint portion so that L ≦ 4.0 × D with respect to the outer diameter D of the mounting shaft portion, Stress concentration can be reliably prevented. In order to secure the cutting edge length, it is more preferable to set the length L within a range of 0.8 × D ≦ L ≦ 4.0 × D.

  Furthermore, by forming the bonding layer formed between the tip and the tool body from a metal layer and the diffusion layer, a metal layer having ductility is provided in the bonding layer, The stress generated in the cBN layer or the cemented carbide layer can be absorbed by the metal layer, for example, thermal stress accompanying a temperature change, and the occurrence of cracks in the cBN layer and the cemented carbide layer of the chip can be prevented. Moreover, since the residual stress accompanying thermal stress can be reduced by the metal layer, the tip can be prevented from being deformed and damaged when the end mill is used.

  ADVANTAGE OF THE INVENTION According to this invention, the end mill which can adjust the length of a neck part easily while being long-lived and stable, without a chip | tip removing from a tool main body can be provided.

Embodiments of the present invention will be described with reference to the accompanying drawings. 1 and 2 are schematic views of an end mill that is an embodiment of the present invention. Moreover, the chip | tip arrange | positioned at FIG.3 and FIG.4 at the front-end | tip of an end mill is shown.
The end mill 10 is a ball end mill having a ball blade formed in an arc shape as shown in FIG. 1, and a cutting edge portion 11 having the ball blade is formed at the tip (left side in FIG. 1). In addition, a neck portion 12 having a slightly smaller diameter than the cutting blade portion 11 is provided on the rear end side of the cutting blade portion 11, and a shank portion 13 having a larger diameter on the further rear end side of the neck portion 12. Is formed. As described above, the end mill according to the present embodiment is a so-called neck-thin type end mill in which the outer diameter of the neck portion 12 is smaller than the outer diameter of the cutting edge portion 11.
The processing depth of the end mill 10 is determined by the lengths of the cutting edge portion 11 and the neck portion 12.

The end mill 10 includes a tip 14 and a tool body 15 connected to the tip 14.
As shown in FIG. 4, the chip 14 has a substantially cylindrical shape. A cBN layer 14A is formed at the tip (upper side in FIG. 4), and a cemented carbide layer 14B is formed so as to be laminated on the cBN layer 14A. Has been.
The chip 14 is manufactured as follows. First, a powder in which cubic boron nitride particles and titanium nitride or titanium carbide particles as a binder are mixed is placed on the upper part of a base material made of cemented carbide, and the pressure space of the ultrahigh pressure sintering apparatus is placed. The chip material 30 in which the cemented carbide layer 32 and the cBN layer 31 are integrally formed as shown in FIG. 3 is obtained by loading and heating to about 1300 ° C. under a high pressure of about 4 GPa. The chip 14 is obtained by cutting the chip material 30 into a cylindrical shape by a discharge wire cut.

  The tool body 15 is made of a general cemented carbide, for example, a tungsten carbide based cemented carbide using Co as a binder. Further, the tool body 15 has a substantially multi-stage columnar shape, and a cylindrical mounting shaft having a constant outer diameter substantially the same diameter as the rear end portion of the tip 14 on the tip side (left side in FIG. 1). A portion 16 is formed, and a diameter-expanded portion 17 and a large-diameter portion 18 whose diameter increases toward the rear end are formed on the rear end side of the mounting shaft portion 16.

And the junction part 20 is formed between the front end surface of the attachment shaft part 16 of the tool main body 15, and the rear-end surface of the chip | tip 14, and it is set as joining of cemented carbide. That is, in the present embodiment, the joint portion 20 between the tip 14 and the tool body 15 is disposed in the middle of the neck portion 12 of the end mill 10.
In the present embodiment, the length L from the tip of the tip 14 to the joint portion 20, that is, the length L of the tip 24 is L ≦ 4.0 × D with respect to the outer diameter D of the mounting shaft portion 16. Thus, it is further set to be in the range of 0.8 × D ≦ L ≦ 4.0 × D, and more specifically, L = 1.6 × D.
This joint portion 20 is a joint layer having a diffusion layer 21 in which Ni is diffused on the cemented carbide layer 14B side of the chip 14 and a diffusion layer 22 in which Ni is diffused on the attachment shaft portion 16 side of the tool body 15. It is configured.

  The bonding layer is formed by the following procedure. An Ni plating layer having a thickness of about 20 microns is interposed between the cemented carbide layer 14B of the tip 14 and the mounting shaft portion 16 of the tool main body 15, and about 100 MPa is pressed at about 1050 ° C. while pressing about 100 MPa. By holding for 0.2 hours, the Ni element in the Ni plating layer and the Co element which is one component in the cemented carbide are diffused and transferred to each other, so that the diffusion layers 21 and 22 that are alloy layers of Ni and Co are formed. It is formed.

  In the end mill 10 having the above-described configuration, the joint portion 20 is formed between the front end surface of the mounting shaft portion 16 of the tool body 15 and the rear end surface of the tip 14, and the joint portion 20 is disposed in the middle of the neck portion 12. Therefore, the stress at the time of cutting does not concentrate on the joining part 20, and it can prevent that the chip | tip 14 remove | deviates at the time of cutting. Furthermore, the length L from the tip of the tip 14 to the joint portion 20 is such that L ≦ 4.0 × D with respect to the outer diameter D of the mounting shaft portion 16, and further 0.8 × D ≦ L ≦. More specifically, L = 1.6 × D is set so as to be within the range of 4.0 × D, so that stress concentration on the joint 20 can be surely prevented and the cutting edge length can be prevented. It is possible to provide the end mill 10 that ensures the thickness.

  In addition, the joining portion 20 is a joining layer having diffusion layers 21 and 22 and has a stronger joining strength and excellent heat resistance than the conventional end mill 10 joined by brazing. It is possible to prevent the chip 14 from coming off even when a load is applied to the chip 14 or when heat is generated by processing. Further, in the above-described end mill 10, since there is no nest defect generated in brazing, the end mill 10 having a certain bonding strength can be provided stably.

Furthermore, since the cemented carbide layer 14B and the tool body 15 are integrated, the size of the chip material 30 in the thickness direction can be reduced, and the chip material 30 is loaded into the pressure space of the ultra-high pressure sintering apparatus for forming the chip material 30. The number of chip materials 30 to be processed can be increased, and the manufacturing cost of the chip materials 30 can be greatly reduced.
Furthermore, in the end mill 10 having the above-described configuration, the length of the neck portion 12 that determines the processing depth of the end mill 10 can be easily handled by changing the length of the mounting shaft portion 16 of the tool body 15.

Next, the end mill 10 which is the 2nd Embodiment of this invention is demonstrated. 5 and 6 are schematic views of an end mill 10 according to the second embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the member similar to 1st Embodiment, and detailed description is abbreviate | omitted.
In this end mill 10, a joint 20 exists between the cemented carbide layer 14 </ b> B of the tip 14 and the mounting shaft portion 16 of the tool body 15, and the joint 20 is Ni on the cemented carbide layer 14 </ b> B side of the tip 14. The bonding layer includes a diffusion layer 21 in which Ni is diffused, a diffusion layer 22 in which Ni is diffused on the mounting shaft 16 side of the tool body 15, and a Ni layer 23. The cBN layer 14A of the chip 14 contains 30 to 70% by volume of cBN particles, and the remainder is composed of a binder such as titanium nitride or titanium carbide.

  The bonding layer is formed by the following procedure. An Ni foil having a thickness of about 50 microns is interposed between the cemented carbide layer 14B of the tip 14 and the mounting shaft portion 16 of the tool body 15, and about 0 at 950 ° C. while being pressed at about 100 MPa. By holding for 2 hours, the Ni element in the Ni foil and the Co element in the cemented carbide are diffused and transferred to each other to form diffusion layers 21 and 22 that are alloy layers of Ni and Co, and Ni that does not contribute to diffusion. Layer 23 is formed.

  In this way, the end mill 10 is configured by joining the tip 14 and the tool body 15 by diffusion bonding. The end mill 10 includes a cutting edge portion 11 having a cutting edge formed at the tip thereof, and a neck portion 12 having the same outer diameter as the cutting edge portion 11. In the present embodiment, the end mill 10 and a tip 14 are disposed in the middle of the neck portion 12. The joint 20 with the tool body 15 is arranged.

  The end mill 10 configured as described above has the same effect as that of the first embodiment, and the bonding layer includes the Ni layer 23 having ductility. Further, it is possible to prevent the thermal stress generated in the cemented carbide layer 14B from being absorbed by the Ni layer 23 and causing cracks and the like in the cBN layer 14A.

  Further, in the end mill 10 having the above configuration, the stress accumulated in the cBN layer 14A and the cemented carbide layer 14B is absorbed by the Ni layer 23, so that the residual stress in the cBN layer 14A and the cemented carbide layer 14B is reduced. Further, deformation and breakage of the chip 14 can be prevented. In particular, in the cBN layer 14A containing 30 to 70% by volume of cBN particles, the difference in thermal expansion coefficient from the cemented carbide is large, and the thermal stress generated in the process of returning to room temperature after the diffusion treatment becomes large. The Ni layer 23 that can be absorbed is effective in preventing the occurrence of cracks and the like and the deformation and breakage of the chip 14 due to residual stress.

As mentioned above, although embodiment of this invention was described, this invention is not limited to this, In the range which does not deviate from the technical idea of the invention, it can change suitably.
For example, Ni has been described as the metal to be diffused, but the present invention is not limited to this, and Fe, Ni, Co, Ta, Cu, Cr, Mo, Ti, Zr, W, V, Nb, Pd, Si, and One or two or more metals selected from Hf may be used. However, since Ni completely dissolves with Co and can be easily diffused, Ni is suitable as a metal to be diffused.

  In addition, the ball end mill having a ball blade having a tip formed in an arc shape has been described. However, the shape of the end mill is not limited, and a square end mill formed so that the tip blade is substantially perpendicular to the axis and an R on the outer periphery of the tip. Other end mills such as a radius end mill in which blades are formed may be used. Furthermore, the outer diameter of the end mill is not limited, and may be, for example, a corner radius end mill having an outer diameter of 10 mm and a corner R of 1 mm.

Furthermore, the outer diameter of the neck has been smaller than the outer diameter of the cutting edge, but has been described as a so-called neck-thin end mill, but the present invention is not limited to this, and the outer diameter of the cutting edge and the outer diameter of the neck And may be the same.
Moreover, although demonstrated as what the outer diameter of the neck part was made constant, it is not limited to this, The neck part may be formed in the taper shape.

It is a schematic explanatory drawing of the end mill which is the 1st Embodiment of this invention. It is an expansion explanatory view of the joined part of the end mill shown in FIG. It is explanatory drawing of the chip | tip raw material for forming the chip | tip used for the end mill shown in FIG. It is a perspective view of the chip | tip used for the end mill shown in FIG. It is a schematic explanatory drawing of the end mill which is the 2nd Embodiment of this invention. FIG. 6 is an enlarged explanatory view of a joint portion of the end mill shown in FIG. 5.

Explanation of symbols

10 End mill 11 Cutting edge portion 12 Neck portion 14 Tip 14A cBN layer (cubic boron nitride sintered body layer)
14B Cemented carbide layer 15 Tool body 16 Mounting shaft portion 20 Joint portions 21, 22 Diffusion layer 23 Ni layer (metal layer)

Claims (3)

A substantially cylindrical chip in which a cubic boron nitride sintered body layer and a cemented carbide layer are integrally molded, and the chip and the same axis as the chip are connected to the cemented carbide layer on the rear end side of the chip. A tool body, and an end mill having a cutting edge formed at a tip portion of the tip,
An attachment shaft portion is formed at least on the front end side of the tool body, and the outer diameter of the front end surface of the attachment shaft portion is the same as the outer diameter of the rear end surface of the chip, and the rear end surface of the chip A joint portion is disposed between the front end surface of the mounting shaft portion,
The end mill is characterized in that the joining portion is a joining layer including a diffusion layer in which a metal element diffuses into at least one of the tip and the tool body.   2. The length L from the tip of the chip to the joint portion is set to L ≦ 4.0 × D with respect to the outer diameter D of the mounting shaft portion. End mill.   The end mill according to claim 1, wherein the bonding layer includes a metal layer and the diffusion layer.

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