JP5283016B2 - Diamond sintered body for cutting tools containing coarse diamond particles - Google Patents

Description

  The present invention relates to a diamond sintered body for manufacturing a cutting tool having diamond as a main component at a cutting edge.

  Conventionally, single crystal diamond tools have been used for ultra-precision machining of soft metals such as aluminum alloys. However, since a large size single crystal diamond is expensive, the single crystal diamond tool has a problem of high manufacturing cost. In addition, a polycrystalline diamond sintered body obtained by sintering diamond powder with a binding material such as Co is less expensive than a single crystal diamond tool, but because it is a polycrystalline body, Rz required for ultraprecision machining is 0. There is also a problem that a surface roughness of 0.5 μm or less cannot be obtained, and streaks are generated on the surface of the work material.

  Therefore, in view of the above problems, the present invention provides a diamond sintered body for a cutting tool that can be manufactured at low cost with a cutting tool that has excellent wear resistance and can improve the surface roughness of the work material. It is an issue to provide.

  When cutting a work material, as shown in FIG. 3, the work material is largely cut off at the lateral cutting edge boundary portion, and a finished surface is formed by the front cutting edge boundary portion. For this reason, the shape of the front cutting edge boundary portion is transferred to the surface of the work material. Therefore, if the wear of the front cutting edge boundary progresses and the surface roughness of the front cutting edge deteriorates, the surface of the work material also becomes rough and the finished state deteriorates. In addition, when the streak begins to occur on the surface of the work material, boundary wear further develops and grooves are formed at the front cutting edge boundary, and the above problem becomes more prominent, and the machining surface roughness deteriorates in a short time. . (See Figure 4)

If the wear of the front cutting edge boundary part of the tool edge can proceed as smoothly as possible, the present inventors can prevent the surface roughness of the work material from being deteriorated, and can perform high-precision machining with a long life. I found out. That is, it has been found that it is effective to make at least the front boundary portion at the time of cutting of the cutting edge a diamond single crystal, and the present invention has been completed. “Smoothly wear” refers to a state in which wear at the front cutting edge boundary portion is suppressed and formation of a step or a groove (streak) is suppressed to make it smooth.
As described above, the present inventors have intensively studied to improve the surface roughness of the work material in cutting with a diamond cutting tool, and as a result, different characteristics are required for each part of the cutting edge in cutting. I found out.

  However, the conventional diamond sintered bodies use sintered bodies having various diamond particle diameters. In these conventional sintered bodies, the diameters of the diamond particles are continuously distributed, and the sintered bodies are sintered. Since the particle size distribution of the diamond particles in the body is close to the diamond particle size distribution of the entire sintered body, the function of an arbitrary part of the cutting edge is equal when the cutting edge is manufactured. For this reason, in a sintered body having an equal function in any part of a conventional diamond sintered body, the material design is such that both functions can be exhibited with respect to the required characteristics that differ depending on the portion of the cutting edge as described above. However, it is not an optimum material design for the required characteristics of each part, and there is a limit in performance.

  The present inventors pay attention to the above points, and provide a cutting edge in which the required characteristics of each part are optimized by a diamond sintered body in which coarse diamond particles and fine diamond particles are appropriately mixed. The present invention has been completed by finding out what can be done. That is, the present invention has the following features.

(1) A diamond sintered body for a cutting tool according to the present invention comprises:
The diamond content is 70-98% by volume;
A first diamond particle group and a second diamond particle group;
The average particle size of the first diamond particle group is 50 μm or more, and is 5 times or more the average particle size of the second diamond particle group,
The average particle size of the second diamond particle group is 20 μm or less, and the content of the second diamond particle group is 50% by volume or more,
The binder phase has at least an iron group metal.
(2) The diamond sintered body according to (1), wherein the iron group metal includes any one of Fe, Co, and Ni.
(3) The diamond sintered body according to (1) or (2) above, wherein an average particle diameter (particle diameter) of the first diamond particle group is 100 μm or more, and an average of the second diamond particle group The particle size is 8 μm or less.

  In the diamond sintered body according to the present invention, diamond particles having a particle diameter of a predetermined size or more are arranged, so that a diamond single crystal having a large particle diameter is used as a cutting edge or a part of a cutting edge. Sintered body tools can be produced. By using these large-diameter diamond single crystals at the front boundary of the cutting edge, an excellent surface roughness with an Rz (ten-point average roughness) of 0.5 μm or less can be obtained by ultra-precision machining of a soft metal. . Further, it is possible to provide a diamond sintered body that enables production of a tool that is cheaper than a conventional cutting tool made of single crystal diamond.

It is a figure which shows an example of the preferable cutting tool using a diamond sintered compact. It is a figure which shows an example which cuts out the blade edge | tip part of the diamond sintered compact concerning this invention from a sintered compact. It is a figure showing the outline of the favorable cutting state by the conventional cutting tool. It is a figure showing the outline of the cutting state where the blade edge | tip was worn by the conventional cutting tool.

  The diamond sintered body according to the present invention has a first diamond particle group and a second diamond particle group, the average particle diameter (particle diameter) of the first diamond particle group is 50 μm or more, and the first The average particle size of the diamond particle group is at least five times the average particle size of the second diamond particle group. By having coarse diamond particles (single crystal) having an average particle size of 50 μm or more and fine diamond particles having an average particle size of 1/5 or less of the coarse diamond particles, It is possible to give the desired function to an arbitrary part.

  For example, by arranging a coarse-grained diamond single crystal on the front cutting edge portion including the front cutting edge boundary portion, the wear of the front cutting edge is smoothly advanced, and the surface roughness of the work material is improved. be able to. From this viewpoint, the more preferable average particle diameter of the first diamond particle group is 100 μm or more.

  On the other hand, when chipping due to the cleavage property of the diamond single crystal is a problem, the cutting edge portion may be formed of a diamond polycrystal formed by a group of fine diamond particles. In addition, if the cutting edge portion other than the front cutting edge portion is formed of a polycrystalline diamond, there is an advantage that it can be provided at a lower cost compared to the case where a tool is produced from only a diamond single crystal. From these viewpoints, a more preferable average particle diameter of the second diamond particle group is 8 μm or less.

  The diamond sintered body has a diamond content of 70 to 98% by volume. When the content of diamond is within these ranges, it is possible to achieve both the strength and wear resistance of the sintered body. A more preferable range of the diamond content is 80 to 95% by volume.

  Furthermore, the binder phase of the sintered body has at least an iron group metal. The iron group metal preferably has at least one selected from Fe, Co, and Ni. With these binder components, the wear resistance and strength of the diamond sintered body can be improved. Of course, impurities other than these components may inevitably be contained.

With the diamond sintered body according to the present invention, for example, the following cutting tool can be manufactured.
<Preparation of a cutting tool whose front edge boundary is a single crystal>
As described above, in order to finish the surface of the work material smoothly, it is preferable that the edge wear near the front cutting edge boundary portion proceeds smoothly without unevenness. As shown in FIG. 3, since the finished surface is formed by the front cutting edge boundary portion, the shape of the front cutting edge boundary portion is transferred to the surface of the work material. “Smoothly wear” refers to a state in which wear at the front cutting edge boundary portion is suppressed and formation of a step or a groove (streak) is suppressed to make it smooth.

  Therefore, in order to improve the surface roughness of the work material, as shown in FIG. 1, the cutting edge in the feed direction is selected from the point where the cutting amount becomes maximum at the cutting edge portion in contact with the work material. It is preferable that the cutting edge in the direction opposite to the feed with x% (x ≧ 10) of the cutting amount is y% (y ≧ 10) of the cutting amount is formed of a diamond single crystal. Thereby, since the front cutting edge boundary part is also formed of the diamond single crystal, the front cutting edge is excellent in wear resistance. For this reason, the surface roughness of the work material surface, such as when cutting with a polycrystalline diamond, is suppressed, and at the same time, the front edge of the cutting edge wears smoothly and has a long service life. It becomes a cutting tool.

  On the other hand, the horizontal cutting edge boundary portion is a portion where the work material is largely cut, and does not particularly affect the surface roughness of the finished surface. For this reason, the cutting edge in the feed direction has x% (x ≧ 10) of the cutting amount and the cutting edge in the direction opposite to the feeding has y% (y ≧ 10) of the cutting amount from the point where the cutting amount becomes maximum. If the exceeding portion is formed of a diamond polycrystal, it can be provided at a lower cost than when a tool is produced only from a diamond single crystal. Moreover, since x and y each exceed 80 and the grinding | polishing cost of a blade edge will become high, it is preferable that it is 80 or less.

  In order to produce such a cutting tool, it suffices to cut from the diamond sintered body according to the present invention so that the front cutting edge portion is constituted by a diamond single crystal and the side cutting edge portion is constituted by a diamond polycrystal. (See FIG. 2). At this time, among cutting edges that come into contact with the work material at the time of cutting, the cutting edge in the feed direction is up to x% (x ≧ 10) of the cutting amount from the point where the cutting amount is maximum, and the cutting edge in the direction opposite to the feeding direction Is preferably constituted by diamond particles having a particle diameter of 50 μm or more, up to y% (y ≧ 10) of the cutting depth. More preferably, the diamond single crystal has a particle diameter of 100 μm or more.

  When the work material is an aluminum alloy, oxygen-free copper or the like, in order to perform ultra-precise cutting, in general, the cut amount is 0.01 to 0.15 mm, and the feed amount is 0.001 to 0.2 mm. This is performed under the condition of / rev. In such a case, since the cutting edge moves backward due to the progress of wear, the cutting edge in the feed direction from the nose tip of the diamond sintered body tool has x% of the cutting amount, and the cutting edge in the direction opposite to the feeding has the cutting amount. It is desirable that y% is formed of a diamond single crystal, and x and y are 10 or more. As a result, the front cutting edge boundary portion is composed of a diamond single crystal, and the lateral cutting edge boundary portion is composed of a diamond polycrystal.

  Using cemented carbide pots and balls, diamond particles and binder materials such as Co and WC are mixed and then heat-treated, and this powder is filled into a Mo container together with a Co plate, with a pressure of 5.5 GPa, Sintering was performed at a temperature of 1,410 ° C. for 22 minutes, and diamond sintered bodies shown in Table 1 were obtained. This sintered body was cut and joined to a base metal made of cemented carbide using a brazing material as a base material, and then subjected to polishing to produce a cutting tool (TPGN110308). At this time, a coarse diamond single crystal body is arranged at the front cutting edge boundary portion of the tool, and the cutting edge in the feed direction has a cutting amount from the point where the cutting becomes the maximum at the cutting edge portion in contact with the work material. 30% of the cutting edge in the direction opposite to the feed is sintered so that 40% of the cutting depth is formed of a diamond single crystal, and the other cutting edge portion in contact with the work material is formed of a polycrystalline diamond. After confirming the position of the coarse diamond single crystal particles in the body, cutting, joining and polishing were performed.

  Using this cutting tool, oxygen-free copper was used as a work material, and a cutting test was performed under the conditions shown in Table 2. As a result, the tool life shown in Table 2 was obtained by setting the life criterion as 0.4 μm in Rz.

Claims (3)

The diamond content is 70-98% by volume;
A first diamond particle group and a second diamond particle group;
The average particle size of the first diamond particle group is 50 μm or more, and is 5 times or more the average particle size of the second diamond particle group,
The average particle size of the second diamond particle group is 20 μm or less, and the content of the second diamond particle group is 50% by volume or more,
A diamond sintered body for a cutting tool, wherein the binder phase has at least an iron group metal. The diamond sintered body for a cutting tool according to claim 1, wherein the iron group metal includes any one of Fe, Co, and Ni. 3. The cutting tool according to claim 1, wherein the first diamond particle group has an average particle diameter (particle diameter) of 100 μm or more, and the second diamond particle group has an average particle diameter of 8 μm or less. Diamond sintered body.

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