JP2006026870A - Super-abrasive grain sintered body throw-away tip - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a throw-away tip with less peeling off by residual stress and long life of a tool as a whole by integrally sintering a super-abrasive grain sintered body on both main surfaces of a tip base body by simultaneous sintering and providing apexes, i.e., each three or more of cutting blades on the respective surfaces. <P>SOLUTION: A sintering material in which super-abrasive grain power is arranged adjacent to upper and lower surfaces of a cemented carbide disc is filled in a high temperature/high pressure device and is exposed under the pressure/temperature condition that the super-abrasive grain substance becomes stable thermodynamically. The sintering material recovered after cooling and removing the pressure is polished after the pressure medium or the like is removed to expose a super-abrasive grain surface. Thereafter, it is cut out to multi-apex shape such as octahedral star shape by a wire cut. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a throw-away tip that has a long tool life and enables an efficient cutting operation, and particularly relates to a sintered diamond and a sintered c-BN tip.

  For various metal cutting operations, a chip made of cemented carbide as a whole, or a sintered body of diamond or c-BN as a cutting blade material integrated with a cemented carbide backing material (hereinafter referred to as PCD and PCBN, respectively) PCD cutting tools and PCBN cutting tools, which are cut into a cutting edge shape having only one cutting edge and are brazed to a steel holder (also called “shank”), are known and put into practical use.

  At this time, in the cutting tip, only the minute part of the tip is used for the actual cutting work, so the vertex of one side of the cemented carbide substrate formed in an equilateral triangle or square plate shape and the acute angle of the rhombus substrate A throw-away chip having a configuration in which PCD or PCBN is arranged at the apex is also known.

  Regarding the shape of the throw-away tip, a polygonal configuration having a circular shape or an obtuse angle vertex in addition to the above is also commercially available.

  These various throwaway tips are fixed by bolting or clamping so as to be indexable (indexable) mainly on a steel holder or shank. When the cutting blade is worn by the cutting operation and the cutting performance is deteriorated, the cutting operation is performed by switching to an unused tip. In principle, the blades are not re-sharpened.

As described above, in the throw-away tip, the cutting blade can be replaced only by indexing work, and the work stop time is short. However, in the configuration in which the cutting blade material is arranged at the apex of an acute angle, the number of cutting blades per chip is 2 to 4, and even when the cutting blade material is PCD or PCBN, there is room for improvement in the tool life as a whole chip. was there.
JP-A-1-51296

  On the other hand, in the PCD integrated with the cemented carbide backing material by simultaneous sintering, a large stress is left between the cemented carbide and the diamond layer based on the difference in thermal expansion coefficient between the two materials. This stress is applied to the PCD layer by the force that releases the stress when the chip is heated for brazing to the shank (subject to a high temperature of about 700 ° C. even with low temperature soldering) or when an impact load is applied. Peeling may occur.

  The present invention mainly provides a superabrasive sintered throw-away tip with a long overall tool life that requires less time for tip replacement and enables efficient cutting work, and an economical manufacturing method. With a purpose.

  Another object is to provide a PCD chip in which peeling of the PCD layer from the substrate hardly occurs.

  The cutting tip of the present invention has a cemented carbide plate having a pair of main surfaces parallel to each other, and a sintered superabrasive layer closely bonded to each main surface of the cemented carbide plate, and on the main surface. A parallel throw circular or polygonal throwaway type cutting tip having three or more cutting edge vertices, wherein the sintered superabrasive layer has a pressure temperature at which the superabrasive material is thermodynamically stable. The main feature is that the particles are sintered to each other under the conditions and are joined to the cemented carbide plate as a whole.

  In the present invention, particularly in the case of PCD, there is a difference of one digit or more in the thermal expansion coefficient from the cemented carbide of the base material, but since the PCD layers are arranged on both sides of the cemented carbide plate, As in the case of a chip in which a PCD layer is disposed only on one side, problems such as poor precision of the cutting edge dimensions due to deformation due to distortion and peeling of the diamond sintered layer due to strong impact have been solved.

  The shape (plan view) of the base body in the cutting tip of the present invention is, for example, an equilateral triangle or square, or two congruent equilateral triangles or squares that overlap each other around the central axis perpendicular to the center or main surface. It can be a shape rotated by ° or 45 °, a six-pointed star or an eight-pointed star. At this time, the angle of the vertex does not necessarily have to be 60 ° or 90 °, and can be changed within a designable range, for example, 80 ° or 70 °, respectively.

  In addition, it may be a pentagram or a seven-pointed star having apexes arranged at equiangular intervals around the central axis, or other multi-pointed star shape.

  As another example, it is also possible to use a shape in which the acute angle vertices of two congruent rhombuses are shifted by 90 ° around the center and overlapped. Further, by reducing the vertex angle to, for example, 30 ° or 45 ° and shifting each by 30 °, a twelve-pronged substrate can be obtained. The number of vertices depends on the structure of the holder to be combined and the characteristics of the available cutting tool, but can be arbitrarily selected within the range.

  The term “superabrasive” typically refers to diamond and c-BN (cubic boron nitride). The technology to obtain these sintered superabrasive layers integrated with the backing material of cemented carbide (simultaneously sintered) by subjecting these materials that are metastable under normal pressure to a thermodynamically stable high temperature and ultrahigh pressure Has been established. At this time, the superabrasive grains and the superabrasive grain layer were bonded to the cemented carbide with a melt mainly composed of an iron group metal supplied from the cemented carbide or previously mixed with the superabrasive powder. A metal material acts as a binder.

  When the sintered superabrasive layer is c-BN, one kind or a combination of several kinds of carbides, nitrides and carbonitrides of metals such as titanium, zirconium, tantalum, molybdenum and niobium are contained in a smaller amount than c-BN. be able to.

  In the case of PCD, the thickness of the sintered superabrasive layer is desirably 0.1 mm or more in order to obtain a reliable sintered layer. On the other hand, only a small part of the tip contributes to actual cutting, and a thickness of 0.5 mm can be considered sufficient. On the other hand, in the case of PCBN, a thickness of 0.1 mm or more and 0.8 mm or less is desirable. Excessive thickness should only be avoided as it only results in a wasteful increase in product cost. The cemented carbide layer (typically WC-Co system) used as the base material is a sintered product that has been sintered in advance, so the thickness is optional if it is 1.5 mm or more. Is set according to

  In the present invention, based on this simultaneous sintering technique, diamond or c-BN particles sized on both sides of a sintered cemented carbide (circular) plate are used as a metal material or ceramic powder as a binder. By arranging the mixture and subjecting it to sintering conditions, it is possible to obtain a composite in which a sintered body of diamond or c-BN is firmly bonded to both surfaces of the cemented carbide plate. This composite is cut into a design shape by cutting the superabrasive surface by wire cutting, laser cutting, or the like, and then bladed.

  An octagonal PCD throw-away chip as shown as 1 in the plan view of FIG. 1 was produced. As schematically shown in the cross-sectional view including the central axis in FIG. 2, IMM class diamond powder (made by Tomei Diamond) 3 having a particle size of 8-16 μm is placed in a container 2 having an inner diameter of 85 mm and a depth of 2 mm made of a 0.1 mm thick Ta plate. Was placed flat, and a WC-8% Co cemented carbide disc 4 having a diameter of 85 mm and a thickness of 3.7 mm was placed thereon, and the upper edge of the Ta container 2 was caulked. Next, an equivalent amount of the same kind of diamond powder 6 was put in another similar Ta container 5, and the cemented carbide disc 4 was inverted and placed in the Ta container 5, and the Ta container was caulked to obtain a sintered material 7. By repeating these operations, four similar materials were prepared.

  As shown in the cross-sectional view including the central axis of FIG. 3, around the sintered material 7, refractory members 11 to 20 mainly for electrical insulation and heat insulation, NaCl molded ring 21 as a pressure transmission medium, electric heating The cylindrical carbon heater 22 and the metal members 23 to 25 and 26 to 28 for circuit configuration were respectively arranged above and below and loaded into a hydraulic uniaxial pressurization type high temperature and high pressure apparatus. It was subjected to a pressure of 5.5 GPa and a temperature of 1450 ° C. for 20 minutes.

  The sintered material recovered after cooling and depressurization was isolated by removing the pressure medium and the like, exposing the PCD surface, rough polishing and mirror polishing, and then cut into an octagonal shape by wire cutting. The diamond sintered body layer at each apex was ground and bladed to finish a throw-away tip having 16 cutting edges.

  The filling operation of Example 1 was repeated. However, this time, for the matrix in which SBN-F-G6 grade c-BN (made by Showa Denko) with a particle size of 4-8μm is added instead of the above diamond, and a small amount of Al powder is added to a 1: 1 mixed powder of TiC and TiN. The powder and the 55:45 ratio (weight) were blended to form a sintered material, and 20 g of this sintered material was used to form each layer of PCBN. A cemented carbide plate having the same composition and shape as that in the above example was used. By repeating these operations, four sintered materials for preparing a chip having a c-BN layer on each (main) surface of the cemented carbide disc were prepared.

  Around the four PCBN sintered materials, a refractory member, a NaCl molding ring, a cylindrical carbon heater, and metal members for circuit configuration were arranged, and similarly loaded into a hydraulic uniaxial pressurization type high temperature and high pressure device. . Subjected to a pressure of 5.5 GPa and a temperature of 1500 ° C. for 20 minutes.

  The sintered material recovered after cooling and depressurization was isolated by removing the pressure medium and the like, exposing the PCBN surface, rough polishing and mirror polishing, and then cutting into a hexagonal star shape with an apex angle of 50 ° by wire cutting.

  Further, the c-BN sintered body layer at each vertex was polished and bladed to finish a throw-away tip having 12 cutting edges.

  Since the throw-away tip of the present invention has cutting edges made of superabrasive grains on both chip surfaces, the machining amount per chip is greatly improved compared to conventional chips having cutting edges only on one side. As a result of the reduction in downtime associated with replacement, a significant increase in productivity can be achieved. In addition, especially when using PCD, the problem of peeling due to heat generation and stress release during grinding, as in the conventional throw-away tip, is solved, despite a large difference in thermal expansion coefficient of one digit or more. .

It is a plane explanatory view of the throw away tip according to the first embodiment of the present invention. It is sectional explanatory drawing of the throw away tip by this invention Example 1. FIG. It is explanatory drawing which shows the structure for using for the high temperature / high pressure used in this invention Example 1. FIG.

Explanation of symbols

1 PCD throwaway chip (all)
2 Ta thin plate container 3 Diamond powder 4 Cemented carbide disc 5 Ta Thin plate container 6 Diamond powder 7 Sintered material (whole)
11-20 Refractory member 21 NaCl molded ring 22 Heater 23-25 Metal member 26-28 Metal member

Claims (9)

  A cemented carbide plate having a pair of main surfaces parallel to each other and a sintered superabrasive grain layer closely bonded to each main surface of the cemented carbide plate, and the contour parallel to the main surface is circular or 3 A polygonal throw-away cutting tip having one or more cutting edge vertices, wherein the sintered superabrasive layer has particles that are mutually bonded under pressure and temperature conditions in which the superabrasive material is thermodynamically stable. Cutting tips that are sintered together and joined together with a cemented carbide plate as a whole.   The cutting tip according to claim 1, wherein the sintered superabrasive layer is a sintered diamond layer having a thickness of 0.1 to 0.5 mm including a direct bond between diamond particles.   The sintered superabrasive layer includes cubic boron nitride (c-BN) and a smaller amount of at least one selected from metal carbide, metal nitride, and metal carbonitride as a binder. The cutting tip according to claim 1, which is a 0.8 mm sintered cubic boron nitride layer.   The cutting tip according to claim 1, wherein the cemented carbide layer is based on WC-Co and has a thickness of 1.5 mm or more.   The cutting tip according to claim 1, wherein the polygon has a multi-comet shape having apexes arranged at equiangular intervals around a central axis perpendicular to the main surface.   The cutting tip according to claim 1, wherein the polygon has a hexagonal star shape having apexes having apex angles of 25 to 60 ° every 60 ° around a central axis perpendicular to the main surface.   2. The cutting tip according to claim 1, wherein the polygon has an octagonal shape having apexes having apex angles of 70 to 90 ° every 45 ° around a central axis perpendicular to the main surface.   The cutting tip according to claim 1, wherein the polygon is a regular triangle or a square. (1) In a first cylindrical capsule made of a refractory metal sheet, first weighed sized superabrasive powder, and then put a cemented carbide disk with a pair of parallel main surfaces and fixed. In addition, the weighed sized superabrasive powder is put in the same second capsule, and then the free main surface of the cemented carbide disc is put in the second capsule and fixed,
(2) Loaded into an ultra-high pressure and high-temperature apparatus and subjected to a pressure at which the superabrasive material becomes a stable phase in the presence of an iron group metal melt supplied from a cemented carbide plate,
(3) Collect the composite material of cemented carbide and superabrasive grains from the ultra-high pressure and high temperature equipment and polish the surface.
(4) Cut into a predetermined shape,
(5) The method for manufacturing a cutting tip according to claim 1, wherein the cutting edge portion is subjected to a cutting process.

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