JP2007313569A - Coated drill with very small diameter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drill with an extremely small diameter used for machining nonferrous materials or steel materials whose service lifetime is improved by enhancing chip discharge performance while suppressing the wear of its tip cutting edge by coating it with a hard film. <P>SOLUTION: The drill with an extremely small diameter is used for machining the nonferrous materials or the steel materials and has a blade diameter of smaller than 0.2 mm. A coated drill with an extremely small diameter is configured such that a chip discharge groove of the drill has a length of more than three times of the blade diameter, a base body of the drill is formed of ultrafine-particle cemented carbide in which the average particle size of WC is smaller than 0.8 μm, and the drill is coated with the hard film of higher than HV 25 GPa. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a coated ultra-small diameter drill for machining a fine hole having a diameter of 0.2 mm or less, and more particularly to a coated ultra-small diameter drill used for machining non-ferrous metals such as aluminum alloys and titanium alloys, and steels such as stainless steel.

As a very small diameter drill for use in non-ferrous and steel processing, Patent Document 1 discloses a very small diameter drill having a drill diameter of 0.2 mm or less, a core thickness ratio of 0.2 to 0.4, and a core thickness. An example is described in which any one of carbon steel, alloy steel, and non-ferrous metal having a taper of 0.006 to 0.01 mm / mm and a hardness of HRB110 or less is described. Patent Document 2 discloses a small-diameter shaft tool, a Ti metal layer as a first layer, a second layer, Ti (NwC1-w) as a first layer, where 0.6 ≦ w ≦ 1.0, a third layer, AlzTi1. -Z where 0.05 ≦ z ≦ 0.75 metal layer, fourth layer, (AlxTi1-x) (NyC1-y), where 0.05 ≦ x ≦ 0.750.6 ≦ y ≦ 1 A coated small-diameter shaft tool is described. Patent Document 3 describes a drill core thickness of 35 to 50% D, a twist angle θ10 to 40 °, a diameter of 10 mm or less, Al2O3, TiN, TiAlN, or TiCN. A drill for machining small-diameter holes provided with any one of the hard films is described.
Japanese Patent Application Laid-Open No. 11-114713 JP 2002-103122 A JP 2001-225216 A

  The present invention relates to a very small diameter drill for use in non-ferrous or steel-based processing, which covers a hard coating, suppresses wear of the cutting edge of the tip, and improves chip discharge, thereby improving the service life. Provide a drill.

  In order to solve the above-mentioned problems, the present invention provides an extremely small-diameter drill having a blade diameter of 0.2 mm or less and used for processing a non-ferrous or steel-based work material. A coated ultra-small-diameter drill characterized in that it is provided with the above length, the base of the drill is made of an ultrafine particle cemented carbide having an average particle size of WC of 0.8 μm or less, and a hard coating of HV25 GPa or more is coated. . By applying the present invention, a long-life drilling tool used for non-ferrous or steel drilling can be achieved. Furthermore, the amount of Co in the ultrafine particle cemented carbide is 4 to 12 wt%, the coercive force is 25 to 50 KA / m, the hard coating is TiSiN, and is substantially the same as the blade diameter in the chip discharge groove. It is preferable that three square unit areas are taken at arbitrary positions in the chip discharge groove, and the average value of the number of droplets of about 0.5 μm to several μm is 5 or less.

  According to the present invention, it is possible to provide a very small diameter drill having a blade diameter of 0.2 mm or less that suppresses the wear of the tip cutting edge during processing of a non-ferrous or steel system and improves the life.

In the present invention, the reason why the ultra-small diameter drill having a blade diameter of 0.2 mm or less, the chip discharge groove of the drill has a length of three times or more the blade diameter, and the non-ferrous or steel-based work material is as described above. Such small-diameter hole machining is particularly dependent on the application used for drilling parts such as precision parts such as stainless steel, aluminum alloy, and titanium alloy.
Next, the base of the drill is made of an ultrafine particle cemented carbide with an average particle diameter of WC of 0.8 μm or less. By using ultrafine particle cemented carbide, the WC particles fall off and the tip cutting edge is damaged. Life is shortened. When the average particle diameter of WC is set to 0.8 μm or less, the strength of the cutting edge ridge line can be increased, and dropping of WC particles can be suppressed. Furthermore, the reason why the Co content of the ultrafine particle cemented carbide is 4 to 12 wt% is that if the Co content is less than 4%, the hardness of the superhard material is too hard and chipping occurs, so that the life is reduced. If it exceeds 50%, the hardness of the super hard material is soft and the edge of the cutting edge is worn away, resulting in a shortened life. When the coercive force is less than 25 KA / m, the thickness of low-strength Co increases between WC particles, the hardness of the superhard material decreases, wear resistance cannot be obtained, tool life is reduced, and 50 KA / If it is larger than m, the hardness of the superhard material is increased, so the range is set to 25 KA / m to 50 KA / m.

Furthermore, the hard coating has a hardness of HV25 GPa and improves the wear resistance of the tip cutting edge. If it is less than HV25 GPa, the wear resistance is lowered, the work material is welded, the hard coating is peeled off, the base material is exposed, and further welding is caused in a vicious circle. The hard coating is preferably composed of one or more solid solutions or mixtures of nitrides, oxides, borides, sulfides, and carbides containing at least Ti and Si as metal components. As a result, Si and the workpiece easily form a lubricating layer, and the lubricating layer is extremely dense and difficult to peel off. As a result, the wear resistance effect is improved against non-ferrous metals and steel. A preferable component system of the hard coating includes TiSiN, TiSiCN, TiSiNO, and TiSiBN, and the optimum Si content is 5% by atom or more and less than 30% by atom with only the metal element. As the metal component other than TiSi, Al, Cr, Nb, Mo, and wt are raised, and the atomic percentage of the metallic element alone is added to 10 atomic% or less. Furthermore, an unbalanced magnetron sputtering method is preferable as a method for extremely reducing the number of droplets.
Take the number of droplets in the chip discharge groove, set the unit area of a substantially square shape that is substantially the same as the blade diameter in the chip discharge groove, and take three locations at arbitrary positions in the chip discharge groove. The reason why the average value of the number of droplets of about 5 μm to several μm is set to 5 or less is that the chips generated by the tip cutting edge smoothly flow in the chip discharge grooves, so that the chips are generated in the chip discharge grooves. There is no clogging and the chip discharge performance is demonstrated from the beginning of use. When the average value exceeds 5, the droplets have various sizes of protrusions ranging from 0.5 μm to several μm in the initial stage of use, and the probability that the chips get caught in the droplets and inhibit the discharge of the chips. Increases, causing chip jamming. In severe cases, sudden breakage may occur.

Example 1
As Example 1 of the present invention, the average particle size of WC is 0.6 μm or less, the amount of Co is 13 wt%, and the coercive force is 19.5 KA / m. A groove length of 1.0 mm, a twist angle of 30 °, and a TiSiN film (HV35GPa) as a hard coating on the cutting edge of the tip is coated with a thickness of 1.5 μm by an unbalanced magnetron sputtering method, and is substantially square with the same diameter as the blade. the unit area 0.2 mm ² droplet observed at 1000-fold with a scanning electron microscope, 0.2 mm from the cutting edge to the drill rotational center axis, 0.4 mm, position of 0.6 mm, that is to edge diameter 10 times, 2 times, and 3 times were taken, the number in each unit area was measured, and 10 were confirmed to have an average value in the range of 4-5. As Comparative Example 2, 10 samples having the same specifications as in Example 1 of the present invention and not coated with a hard coating were prepared.

The cutting specifications are SUS304 as the work material, and at a vertical machining center, the cutting speed is 15 m / min, the feed amount per rotation is 0.002 mm / rev, the step amount is 0.02 mm, and the drilling depth is A 1 mm through hole was machined. The coolant was externally supplied with water-soluble cutting oil. The target number of holes is set to 400, and the cutting edge of the cutting edge is observed at a magnification of 1000 times with a scanning electron microscope for every 20 processed holes. For those in which no defects were observed, the maximum flank wear width was measured, and when it exceeded 20 μm, it was judged as a life, and the processing was stopped. The maximum number of processed holes in 10 samples was recorded as the number of processed holes, and the maximum wear width in 10 was recorded when the life was reached due to wear.
In Example 1 of the present invention, it was possible to machine up to the target number of holes, and all 10 holes could be machined beyond the target number of holes. Therefore, when further machining was performed, it was possible to machine up to 500 holes, and the maximum flank wear width was 18 μm. And a stable long life. In Comparative Example 2, defects occurred at the initial stage of processing, and only 60 holes could be processed at maximum. When the cutting edge was observed, the stainless steel was welded, and the WC particles at the cutting edge repeatedly dropped off, and the life was reached early.

Using Invention Example 1 and Comparative Example 2, the work material was changed to S50C, Al—Cu alloy, and the target machining hole number was changed to 500 holes in the same cutting test as in Example 1 for machining. And evaluated.
In Example 1 of the present invention, even when S50C and Al—Cu alloy were processed, 10 holes could be processed up to 500 holes in the same manner as when SUS304 was processed, and the maximum flank wear width was 18 μm and 15 μm, respectively, which was a stable length. It was a lifetime. In Comparative Example 2, in the processing of S50C, the life was reached due to wear at 80 holes, and the target number of holes could not be processed. In the processing of the Al—Cu alloy, it was possible to process up to 500 holes, but the maximum flank wear width was 23 μm, which exceeded the limit.

(Example 2)
Using a commercially available WC powder having an average particle size of 0.2 to 1.2 μm, 1.2 μm Co powder, 1.2 μm Cr3C2 powder, 1.5 μm VC powder and 1.2 μm TaC powder as a grain inhibitor. , Mixed in each composition shown in Table 1, mixed in an alcohol attritor containing molding binder for 12 hours, granulated and dried with a spray dryer, and then the resulting granulated powder was extruded and molded into a green compact and did. Next, these green compacts were sintered at 1400 to 1450 ° C. in a vacuum atmosphere, and then subjected to HIP treatment. In each of the cemented carbides of the samples as Invention Examples 3 to 15 and Comparative Examples 16 to 22, Ten ultra-small drills were manufactured. Other specifications were made in the same manner as in Example 1 of the present invention. The test was conducted with SUS304 as in Example 1. Table 1 shows the specifications and results of Invention Examples 3 to 20, Invention Example 1 and Comparative Examples 21 to 22.

From Table 1, Examples 3 to 20 of the present invention were able to machine the target number of machining holes, so the machining was further extended to 500 holes. Invention Examples 3 to 16 are examples having a WC average particle diameter of 0.6 μm, and Invention Examples 3 to 13, Invention Example 1 and Invention Example 16 were able to process up to 500 holes. The damaged state was normal wear, there was little welding on the blade edge after processing, and there was no peeling of the hard coating. In Invention Example 1 and Invention Example 16, the wear width exceeded 15 μm, and the progress of wear was fast. In the inventive example 13 having a coercive force of less than 25 KA / m, the wear progressed quickly. Inventive Example 17 had a slightly coarse WC average particle diameter, but good results were obtained due to the action and effect of reducing the particle suppression material compared to Inventive Example 8. Examples 18 to 20 of the present invention showed good cutting conditions with a WC average particle size of 0.2 to 0.4 μm, high coercive force, and a wear width of less than 10 μm.
In Comparative Examples 21 to 22, chipping was observed at the blade edge, and there was no one that could be processed to the target number of holes of 500, and the life was reached early.

(Example 3)
As Examples 23-28 of the present invention, those having the same specifications as Example 1 of the present invention and having an average value of the number of droplets in three regions of the chip discharge groove of 0-6 are prepared. In the SUS304 cutting test, the target number of holes was changed to 500 holes, and the same evaluation as in Example 1 was performed. Table 2 shows the specifications and results of Examples 23 to 28 of the present invention.

From Table 2, all of the ten inventive examples 23 to 27 can be processed stably up to 500 holes, the damaged state of the cutting edge is normal wear with a wear width of 15 μm or less, and there is little welding on the cutting edge after processing. It was good with no peeling of the hard film.

Claims (4)

In a very small diameter drill having a blade diameter of 0.2 mm or less and used for processing a non-ferrous or steel work material, the chip discharge groove of the drill is provided with a length three times or more of the blade diameter, and the base of the drill A coated ultra-small-diameter drill characterized in that is made of an ultrafine particle cemented carbide with an average WC particle size of 0.8 μm or less and coated with a hard coating of HV25 GPa or more. The coated very small diameter drill according to claim 1, wherein the amount of Co in the ultrafine cemented carbide is 4 to 12 wt% and the coercive force is 25 to 50 KA / m. 3. The coated minimum diameter drill according to claim 1 or 2, wherein the hard coating is a TiSiN-based drill. 4. The coated very small diameter drill according to claim 1, wherein the hard coating has a substantially square unit area substantially the same as the blade diameter in the chip discharge groove at an arbitrary position in the chip discharge groove. A coated very small diameter drill characterized in that the average value of the number of droplets of about 0.5 μm to several μm is set to 5 or less in three places.