JP4854946B2 - End mill material and end mill - Google Patents

Description

The present invention relates to an end mill material and an end mill, which are tools used for machining a mold.

  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 of about 40 hours. If the end mill suddenly breaks during automatic operation, the die during processing cannot be reworked and becomes defective, resulting in a significant decrease in productivity. Is required.

  FIG. 4 shows a cross-sectional structure of an example of a small-diameter ball end mill using conventional cBN. A ball end mill 1 shown in FIG. 1 includes a tip 2 and a shank 3 connected to the tip 2, and includes a cutting edge portion 4, a neck portion 5, and a handle portion 6. The chip 2 is composed of a cBN layer 7 and a cemented carbide layer 8. The shank 3 is made of cemented carbide, and a mounting recess 11 is formed at the tip of the shank 3. The chip 2 is fitted into the recess 11, and the cemented carbide layer 8 of the chip 2 and the recess 11 of the shank 3 are joined by a brazing material 12. Moreover, the neck part 5 is made into the substantially same diameter as the outer diameter of the cutting blade part 4, and the processing depth which a ball end mill can process is determined by the length of the cutting blade part 4 and the neck part 5. FIG.

  5 (a) and 5 (b) show a chip material and a chip used in the conventional ball end mill. The chip 2 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 17 in which the cemented carbide layer 14 and the cBN layer 16 are integrally formed is obtained by heating to about 1300 ° C. with a high pressure of about 4 GPa applied. The chip 2 is obtained by cutting the chip material 17 into a cylinder by a discharge wire cut.

  By the way, in the ball end mill having the above configuration, in order to hold the tip 2 by the recess 11 of the shank 3, the inner diameter of the recess 11 at the tip of the shank 3 needs to be larger than the outer diameter of the tip 2, so The lengths of 4 and the neck portion 5 are determined by the length of the chip 2. Therefore, in the ball end mill configured as described above, in order to cope with various processing depths, it is necessary to manufacture the chip material 17 with a size corresponding to the processing depth. However, when the size of the chip material 17 increases. Since the number of chip materials 17 that can be loaded in the pressure space of the ultrahigh-pressure sintering apparatus is limited, there is a problem that the manufacturing cost increases.

As a method of joining the chip to the shank, a method of directly brazing the chip and the tip of the shank has been proposed (Patent Document 1). FIG. 6 shows a ball end mill joined in this manner. In the ball end mill 19 shown in this figure, a tip 22 composed of a cBN layer 20 and a cemented carbide layer 21 is joined to a tip portion of a shank 23 via a brazing material 25. Further, the ball end mill 19 has a cutting edge portion 26 and a neck portion 27.
According to this method, since the tip 22 is brazed directly to the shank 23, the diameter of the tip of the shank 23 can be made the same as that of the tip 22. Therefore, the length of the neck portion 27 can be adjusted by the shape of the shank 23.
JP 2002-144132 A

However, in the ball end mill described in Patent Document 1, the chip and the shank are joined by brazing. Brazing is a method in which a brazing material having a low melting point is interposed between the surfaces to be joined, and is melted and solidified to join, and its joining strength is low and it is weak against heat. Therefore, in the ball end mill having the above configuration, when a high load is applied to the tip portion, the tip may be detached from the shank. In particular, in a small-diameter end mill having a diameter of φ3 or less, the joining area becomes very small. Is more likely to come off. Further, in the end mill configured as described above, when the end mill is rotated at a high speed, there is a possibility that the brazing material is melted and chips are detached due to heat generated by the processing. Further, since brazing is a method of joining by once solidified brazing filler metal, voids called nest defects may be formed inside the solidified brazing filler metal due to volume shrinkage during solidification. In an end mill having a small diameter of φ3 or less, the joining area is very small, and when a nest defect is generated inside the brazing material, the joining strength is remarkably deteriorated. 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 an object of the present invention is to provide an end mill material and an end mill that can easily adjust the length of the neck portion with a stable lifetime without the tip being detached from the shank. And

In order to solve the above problems, the present invention provides the following means.
The end mill material according to claim 1 is a cylindrical tip in which a layer composed of a cubic boron nitride sintered body and a cemented carbide layer are integrally formed at a predetermined temperature and a predetermined pressure , and the tip and the axis line. A metal layer interposed between the tip and the shank, and a bonding layer formed between the tip and the shank. A diffusion layer disposed on each of the chip side and the shank side of the metal layer, the diffusion layer having a Ni layer interposed between the chip and the shank, and lower than a temperature at which the chip is molded, The Ni element of the Ni layer and the Co element in the chip and the shank are maintained by applying a predetermined pressing force to the chip and the shank for a predetermined time in a predetermined atmosphere at a temperature capable of diffusion and movement of metal. Is formed of an alloy layer of Ni and Co formed by mutual diffusion and movement, and the metal layer is formed of the Ni layer having a thickness of 50 μm or less that does not contribute to diffusion.
The above-mentioned end mill material is used as an end mill by cutting the tip portion with a blade.
In the end mill material having the above-described configuration, the bonding layer between the tip and the shank includes a metal layer interposed between the tip and the shank, and a tip side and a shank side of the metal layer, respectively. The diffusion layer includes a Ni layer interposed between the chip and the shank, and holds the chip and the shank for a predetermined time by applying a predetermined pressing force in a predetermined atmosphere. Thus, the Ni element of the Ni layer and the Co element in the chip and the shank are formed by an alloy layer of Ni and Co formed by mutual diffusion and movement, and the bonding strength thereof is the conventional brazing. It is remarkably high compared to the joining by. Further, 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, and thus the joining layer of the end mill material is generated inside the brazing material. There is no such nest defect. Further, in the above-mentioned end mill material, the cemented carbide layer of the tip and the shank made of cemented carbide are integrally formed, so that the size of the cemented carbide layer of the tip can be reduced. It becomes possible.

The end mill according to claim 2 is obtained by subjecting the end mill material according to claim 1 to blade processing.
In the end mill of the above configuration, the bonding layer between the chip and the shank, the metal element is constituted by a diffusion layer diffused high that the bonding strength, Ru prevents falling off of the chip.

  According to the first aspect of the invention, since the bonding layer between the chip and the shank is composed of a diffusion layer in which a metal element is diffused, the bonding strength is high, so even in a small-diameter end mill having a diameter of 3 or less, It is possible to prevent the chip from coming off. Further, since a brazing material having a low melting point is not interposed on the joining surface, the heat resistance is excellent, and it is possible to prevent the chip from being detached due to heat generated when the end mill is rotated at a high speed. Further, since the cemented carbide layer of the chip and the shank made of cemented carbide are integrated, the size of the cemented carbide layer of the chip can be reduced, and the size of the chip material can be reduced. 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 material corresponding to the processing depth can be easily provided.

In addition , since the metal layer is provided in the bonding layer between the chip and the shank, and the ductility of the metal layer can absorb the thermal stress accompanying the temperature change, the crack in the cBN layer and the cemented carbide layer of the chip. Can be prevented. Moreover, since the residual stress accompanying a 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.

Further, according to the invention of claim 2, chips without departing during processing, Ru can provide stable end mill life.

A first embodiment of the present invention will be described.
The end mill raw material which is 1st embodiment of this invention is shown to Fig.1 (a), (b). (A) is the cross-sectional schematic of an end mill raw material, (b) is an enlarged view of a joining layer vicinity. The end mill material 31 includes a substantially cylindrical tip 32 and a shank 33 connected to the tip 32. The tip 32 includes a cBN layer 35 and a cemented carbide layer 36. The shank 33 includes a small-diameter portion 37 having substantially the same diameter as the tip 32, an enlarged-diameter portion 38 whose diameter increases toward the rear portion, and a shank. And a main body 39. The shank 33 is made of a general cemented carbide, for example, a tungsten carbide based cemented carbide using Co as a binder. A bonding layer 42 exists between the cemented carbide layer 36 of the chip 32 and the small diameter portion 37 of the shank 33, and the bonding layer 42 is a diffusion layer 43 in which Ni is diffused on the cemented carbide layer 36 side of the chip 32. And a diffusion layer 44 in which Ni is diffused on the small-diameter portion 37 side of the shank 33. Further, the end mill material 31 includes a cutting edge portion 4 where a cutting edge is formed, a neck portion 5 having a diameter substantially the same as that of the cutting edge portion 4, and a handle portion 6.

  The bonding layer 42 is formed by the following procedure. An Ni plating layer having a thickness of about 20 microns is interposed between the cemented carbide layer 36 of the chip 32 and the small diameter portion 37 of the shank 33, and about 0.1 MPa at 1050 ° C. while being pressed at about 100 MPa. By holding for 2 hours, the Ni element in the Ni plating layer and the Co element, which is one component in the cemented carbide, diffuse to each other to form diffusion layers 43 and 44 that are alloy layers of Ni and Co. The

  2 (a) and 2 (b) show a chip material and a chip used for the end mill material of the present invention. In the end mill material having the above-described configuration, the cemented carbide layer 36 of the tip 32 and the shank 33 composed of the cemented carbide are integrated, and the thickness of the cemented carbide layer 36 of the tip 32 is reduced. Therefore, compared with the conventional chip material, the thickness of the cemented carbide layer 48 is reduced, and the total thickness of the chip material 46 can be reduced.

In the end mill material 31 having the above-described configuration, the tip 32 and the shank 33 are joined by the joining layer 42 having the diffusion layers 43 and 44, and the joining strength is stronger than that of the conventional end mill joined by brazing. Since it is excellent in heat resistance, it is possible to prevent the chip 32 from coming off even when a load is applied to the chip 32 by using it as an end mill or when heat is generated by processing. Further, in the end mill material 31 described above, since there is no nest defect generated in brazing, the end mill material 31 having a certain bonding strength can be provided stably.
Further, in the end mill material 31 having the above-described configuration, the size of the chip material 46 in the thickness direction can be reduced. Therefore, the number of the chip materials 46 loaded in the pressure space of the ultra-high pressure sintering apparatus for forming the chip material 46. The manufacturing cost of the chip material 46 can be greatly reduced.
Furthermore, in the end mill material 31 having the above configuration, the length of the neck portion 5 that determines the processing depth of the end mill can be easily handled by changing the length of the small diameter portion 37 of the shank 33.

  3A and 3B show an end mill material according to a second embodiment of the present invention. (A) is the cross-sectional schematic of an end mill raw material, (b) is an enlarged view of a joining layer vicinity. In the end mill material 51 shown in this figure, the bonding layer 52 exists between the cemented carbide layer 36 of the chip 32 and the small diameter portion 37 of the shank 33, and the bonding layer 52 is the cemented carbide layer 36 of the chip 32. A diffusion layer 53 in which Ni is diffused on the side, a diffusion layer 54 in which Ni is diffused on the small diameter portion 37 side of the shank 33, and a Ni layer 55 are configured. The cBN layer 57 of the chip 32 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 52 is formed by the following procedure. A Ni foil having a thickness of about 50 microns is interposed between the cemented carbide layer 36 of the chip 32 and the small diameter portion 37 of the shank 33, and about 0.2 MPa at 950 ° C. while being pressed at about 100 MPa. By maintaining the time, 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 53 and 54 that are alloy layers of Ni and Co, and a Ni layer 55 that does not contribute to diffusion. Is formed.

  The end mill material 51 having the above-described configuration has the same effect as that of the first embodiment, and further includes a ductile Ni layer 55 provided in the bonding layer 52, so that the temperature is returned to room temperature after the diffusion treatment. The thermal stress generated in the cBN layer 57 and the cemented carbide layer 36 is absorbed by the Ni layer 55, and cracks and the like can be prevented from occurring in the cBN layer 57. Further, in the end mill material 51 having the above configuration, the stress accumulated in the cBN layer 57 and the cemented carbide layer 36 is absorbed by the Ni layer 55, so that the residual stress in the cBN layer 57 and the cemented carbide layer 36 is reduced. Thus, deformation and breakage of the chip 32 can be prevented. In particular, in the cBN layer 57 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 55 that can be absorbed is effective in preventing the occurrence of cracks and the like and the deformation and breakage of the chip 32 due to residual stress.

  In the above embodiment, Ni has been described as the metal to be diffused, but the metals to be diffused are Fe, Ni, Co, Ta, Cu, Cr, Mo, Ti, Zr, W, V, Nb, and the like. One or two or more metals selected from Hf may be used. Ni is a solid solution with Co, and can be easily diffused. Therefore, Ni is suitable as a metal to be diffused.

It is explanatory drawing of the end mill raw material which is 1st embodiment of this invention. It is explanatory drawing of the chip | tip raw material used for the end mill raw material which is 1st embodiment of this invention, and a chip | tip. It is explanatory drawing of the end mill raw material which is 2nd embodiment of this invention. It is explanatory drawing of the conventional end mill. It is explanatory drawing of the chip | tip raw material and chip | tip used for the conventional end mill. It is explanatory drawing of the ball end mill shown by patent document 1. FIG.

Explanation of symbols

2, 22, 32 Chip 3, 23, 33 Shank 4, 26 Cutting edge 5, 27 Neck 12, 25 Brazing material 17, 46 Chip material 31, 51 End mill material 7, 20, 35, 57 cBN layer 8, 21 , 36 Cemented carbide layer 42, 52 Bonding layer 43, 44, 53, 54 Diffusion layer 55 Ni layer (metal layer)

Claims (2)

A cylindrical chip in which a layer composed of a cubic boron nitride sintered body and a cemented carbide layer are integrally molded at a predetermined temperature and a predetermined pressure, and a cemented carbide alloy connected to the chip in the same axis. With a shank consisting of
The bonding layer formed between the chip and the shank includes a metal layer interposed between the chip and the shank, and diffusion layers disposed on the chip side and the shank side of the metal layer, respectively. Configured,
In the diffusion layer , a Ni layer is interposed between the chip and the shank to form the chip.
The Ni element of the Ni layer, the chip, and the chip and by holding a predetermined pressing force on the chip and the shank for a predetermined time in a predetermined atmosphere at a temperature that allows the diffusion and movement of metal It is composed of an alloy layer of Ni and Co formed by the diffusion and movement of Co elements in the shank to each other,
An end mill material, wherein the metal layer is composed of the Ni layer having a thickness of 50 μm or less that does not contribute to diffusion.   An end mill obtained by subjecting the end mill material according to claim 1 to a cutting process.

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