JP2012254486A - Extra-high pressure sintered rotary cutting tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shaft-like rotary cutting tool where the rigidity and wear resistance of a point tip are improved, chipping hardly occurs, and a tool service life can be improved by repolishing.SOLUTION: In rotary cutting tool, a point formed of a composite material having a sintered super abrasive grain layer sintered and integrated on a substrate of a hard metal under extra-high pressure/high temperature is brazed to a shank. A prescribed range from the tip in the shaft length direction of a tip, particularly 2.0-7.0 mm is solely configured by a single body of sintered super abrasive grains.

Description

  The present invention is a rotary cutting tool such as a drill or an end mill, in particular, a shaft cutting tool having a cutting edge made of a superabrasive sintered body (PCD or Pc-BN) with improved rigidity and wear resistance and tool life. It relates to a cutting tool.

  In grinding and cutting using rotary cutting tools such as drills and end mills, tools with a cutting edge made of hard metal such as cemented carbide or high speed steel are widely used at the tip of a relatively tough tool body. In general, it is generally practiced to reshape and recycle a material that has been worn or deformed by use.

  On the other hand, a PCD or PCBN cutting tool having a cutting edge made of a harder member such as a diamond sintered body (PCD) or a c-BN sintered body (PCBN) is also generally used. PCD and PCBN are composite materials in which these superabrasive grain layers themselves are sintered under superhigh pressure and high temperature, and are sintered and integrated with the cemented carbide of the support member. A structure in which the particle layer is bonded to the tip of the base (shank) material through a cemented carbide layer is widely used.

JP 2009-226539 A JP 2000-043006 A

  This type of rotary cutting tool is obtained by joining a high-hardness PCD or a small PCBN member to a relatively tough tool body, and can obtain excellent cutting performance with an economical configuration. In the tool disclosed in Japanese Patent Laid-Open No. 2000-043006, the cutting edge portion is made of a high-hardness sintered body, and the portion other than the cutting edge is made of a cemented carbide, such as a cemented carbide with relatively low hardness but high toughness. By using a hard alloy, brazing material, or the like, the loss of this portion is improved.

  However, in these tools, the high-hardness sintered body (ultra-high-pressure sintered body) is joined by the brazing material even if there is a difference in the joining area constituting the cutting edge, and the joining force of the cutting edge is not always satisfactory. .

On the other hand, a method for producing a material of a rotary cutting tool such as a drill, an end mill, or a reamer having a helical cutting edge formed of a superabrasive sintered body around the cemented carbide tool shaft is known. . In this method, a spiral groove is formed on the circumferential surface of a cylindrical cemented carbide substrate, the periphery is covered with a refractory metal plate, superabrasive powder is filled from one end of the groove, Then, the molten metal is poured from the end to flow between the superabrasive grains, thereby integrating the superabrasive grains and realizing the integration with the cemented carbide substrate. As the substrate material, the example describes the use of a 40 mm cylindrical cemented carbide material.
JP-A-8-197339

  Rotating cutting tools are prone to wear on the base material near the cutting edge other than the ultra-high pressure sintered body due to the discharge of chips, and as a result, the shape and discharge status of the chips may change, which may affect machining. is there. In particular, as in the rotary cutting tool described in Japanese Patent Application Laid-Open No. 2000-043006, when the brazed part is close to the tip of the blade edge, the brazed part may be worn during chip discharge and the rigidity may be lowered.

  Furthermore, the cemented carbide part used in the structure around the cutting edge is also worn by the chips, and the shape of the chips and the brazing material part are easily worn, and in addition the chipping and chipping are likely to occur. is expected.

  Since the ultra high pressure sintered compact rotary cutting tool is expensive, the possibility of re-polishing affects the cost reduction. However, with these conventional rotary cutting tools, the superabrasive layer is thin, and even if the tip of the blade is worn or chipped, or deformed due to reduced wear resistance, it cannot be re-polished. There is a problem that it is difficult to extend the tool life due to.

  Further, in application to a cutting tool having a large number of cutting edges, problems such as an increase in brazing points, difficulty in processing, an increase in cost, and a decrease in rigidity are expected.

  Accordingly, one of the main objects of the present invention is to improve the rigidity and wear resistance of the tip of the cutting edge and to prevent chipping in order to solve the problems associated with the conventional rotary cutting tool. An object of the present invention is to provide a shaft-like rotary cutting tool that can be repaired by regrinding even if it occurs. Another object is to provide a tool configuration that can be applied to a rotary cutting tool having a large number of cutting edges, which can be used for machining difficult-to-cut materials such as CFRP by improving the wear resistance of the cutting edge.

  The rotary cutting tool of the present invention is a cutting tool in which a cutting edge made of a composite material having a sintered superabrasive grain layer sintered and integrated at a superhigh pressure and high temperature on a cemented carbide substrate is brazed to a shank. A certain range from the tip in the axial length direction of the cutting edge portion is exclusively constituted by a single body of the sintered superabrasive grains.

  The rotary cutting tool of the present invention is composed of super-abrasive grains that are exclusively sintered at the tip of the blade tip exceeding 2.0 mm, so it is possible to process difficult-to-cut materials such as CFRP by realizing a high hardness and high rigidity blade tip. , High-efficiency cutting work with less burrs is possible, and a remarkable tool life can be achieved due to high wear resistance and heat dissipation. Furthermore, because the polishing allowance is abundant, the tool life can be improved by re-polishing, and it can also be applied to multi-blade tools and the like, thereby achieving design flexibility.

FIG. 1 is an explanatory view showing an example of an ultrahigh pressure sintered compact rotary cutting tool according to the present invention (Example 1).

  In the present invention, the range composed exclusively of sintered superabrasive grains depends on the availability of materials and is currently 7.0 mm or less from the tip of the tool edge. Such a blade tip portion can be formed particularly in the axial length direction by electric discharge machining and mechanical grinding.

  The sintered superabrasive layer composed exclusively of superabrasive grains used in the present invention is preferably sintered diamond containing 85 to 95 vol% of diamond, but in addition to this, cubic boron nitride (c -BN) sintered bodies are also available.

Diamond powder having an average particle diameter of 3 μm and cobalt were blended in the compositions shown in Nos. 1 to 3 in Table 1. With these blends, the raw material powder is wet-mixed and dried, placed in a cylindrical Ta container with an inner diameter of 60.5 mm and a depth (height) of 35 mm, leveled to a height of 18 mm, and a surface of 60 mm in diameter. Put a cemented carbide block with a thickness of 15 mm, seal, fold the end and fix the whole, incorporate it in the cell of the ultra high pressure and high temperature device as shown in JP 2003-160803, and integrate it by sintering, Composite materials having sintered diamond layers of different thicknesses were obtained.

  One piece of each composite material, 6.1 mm diameter and 15 mm long blank material cut by wire cutting, the end of the cemented carbide side cut into a V shape, and brazed to the tool shank through this part did. Next, a flute process was applied to the base part including the diamond sintered body part and the base part of the cemented carbide by electric discharge machining and grinding process, and a double-edged twist drill having a total length of 130 mm as shown in FIG. The tip of the drill had a tip angle of 135 ° and a diameter of 6 mm, and the tip portion of the tip portion made of sintered diamond was made of sintered diamond and extended to the rear cemented carbide substrate 2 and the shank portion 3.

  The operation of the above example was repeated to produce a similar diamond sintered body tool. Put a mixed powder of 90% diamond and 10% cobalt in a similar tantalum container to a height of 7.5 mm, put a cemented carbide block of 15 mm thickness on it, seal it, fold the end and fold the whole Fixed. The whole was incorporated into a cell of an ultra-high pressure and high-temperature apparatus and similarly sintered and integrated under ultra-high pressure and high temperature to obtain a sintered diamond layer having a thickness of 3.0 mm.

A blank material having a diameter of 3.1 mm and a length of 15 mm was cut out from the obtained cylindrical composite material, and the end portion of the cemented carbide portion was cut into a V shape, and brazed to the shank of the tool through this end portion. Subsequently, the flute process was performed in the same process, and the double blade type twist drill was created. The blade part with an axial length of 20 mm was composed of a sintered diamond layer 3 mm from the tip, the tip angle was 135 °, the diameter was 3 mm, and the total length of the tool was 70 mm.

  In the rotary cutting tool of the present invention, the blade tip portion 2.0 mm to 6.0 mm is composed only of an ultra-high pressure sintered body, so that the tool life is improved due to high wear resistance and heat dissipation. Since the polishing allowance is abundant, it can be re-polished and can be said to be an environmentally conscious product. Further, it can be applied to multi-blade tool manufacturing, and in this respect, it can contribute to difficult-to-cut material processing such as CFRP and processing.

1 Sintered diamond layer part 2 Cemented carbide part 3 Shank

Claims (7)

  A rotary cutting tool in which a cutting edge made of a composite material having a sintered superabrasive grain layer sintered and integrated on a substrate of cemented carbide at a high pressure and high temperature is brazed to a shank, the axial length of the cutting edge portion A rotary cutting tool characterized in that a certain range from the tip in the direction is constituted by a single body of a sintered superabrasive layer.   The rotary cutting tool according to claim 1, wherein the range is 2.0 mm or more and 7.0 mm or less.   The rotary cutting tool according to claim 2, wherein the range is 4.5 mm or more.   The rotary cutting tool according to claim 1, wherein the cutting edge portion is created by electric discharge machining and mechanical grinding.   The rotary cutting tool according to claim 1, wherein the cutting edge portion is formed in an axial length direction.   The rotary cutting tool according to claim 1, wherein the superabrasive grains contain diamond, and the sintered superabrasive grain layer contains 85 to 95 vol% of diamond. The rotary cutting tool according to claim 1, wherein the superabrasive grains contain cubic boron nitride.

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