JP4812255B2 - Cutting tool manufacturing method - Google Patents

Description

  The present invention relates to a method for manufacturing a cutting tool having a long life and a cutting tool having a long life. The cutting tool in the present invention includes a so-called disposable throw-away tip, a cutting tool in which a cutting tip for cutting a work material and a guide tip for guiding the tool main body are brazed to the tool main body with a silver brazing material or the like. included. Chips and guides, which are parts that come into contact with and rub against the work material, are made of cemented carbide. The tool body that supports the insert and guide is made of special steel. Even in the case of a tool with such a cutting blade brazed, it is no longer usable when it is worn and the cutting edge of the cutting edge becomes dulled while the workpiece is processed, and the life ends there. The throw-away tip is only disposable, but the cutting tool with a brazing blade or the like must be replaced with a new tool body.

  There are various definitions of the life of a cutting tool, but the life can be defined by how many objects of the same specific shape and the same material can be processed. It can be said that a cutting tool capable of machining 40 workpieces, which are objects, has a lifespan twice that of a cutting tool capable of machining 20 identical objects.

Japanese Patent Publication No.61-40485 "Solid cutting blade" Japanese Patent Publication No.61-40486 "Slowaway Chip" JP 2003-236713 “Throw-away tip for deep hole cutting and throw-away drill for deep hole cutting” Japanese Patent No. 2702661 “Drill Head” Japanese Patent No. 2559599 “Two-Flute Cutting Tool” No. 7-39523 “Drill Head for Deep Hole Cutting” No.7-12 “Carbide drill for deep hole machining”

  Patent documents 1 to 3 are documents of the throw-away tip that becomes the present applicant. This is a chip having a single cutting edge and is fixed to a rotating jig by a bolt. An example is shown in FIG. A parallelogram that has cutting edges on both sides and a bolt hole in the middle.

  Patent Documents 4 to 7 are cutting tools obtained by brazing a cutting blade or a guide to be the present applicant to a tool body. For example, a small piece of a cutting blade and a guide is embedded at the tip of a tool body composed of a hollow rotating shaft. An example is shown in FIG. The present invention can be applied to any of these cutting tools, and can also be applied to other general cutting tools. It is an invention with a wide range of applications.

The cutting blade part and the guide part of the cutting tool are made of cemented carbide such as WC, SiC, TiC. Cemented carbide cutting blades are mostly black amber. Although it is an extremely hard material, it is still easy to chip or wear with a cemented carbide alone, so a hard thin film is often coated on the surface of the cutting edge portion. These are Ti and alumina (Al ₂ O ₃ ), TiN, TiAlN, and the like. It may be applied by CVD (Chemical Vapor Deposition) or PVD (Physical Vapor Deposition).

  In CVD, a chemical substance that is a component of a coating is used as a raw material, and this is heated and evaporated to cause a chemical reaction in the gas phase and be deposited on a substrate. There are several CVD methods depending on the means for exciting the source gas. The thermal CVD method heats the substrate and the raw material by resistance heating with a heater, filament heating, or lamp heating. Depending on the composition of the raw material, this often requires a high temperature of 1000 ° C. or higher. If the temperature is too high, then the raw material is exposed to a high frequency and microwave to bring it into a plasma state and cause a chemical reaction. It is called microwave CVD.

  The PVD method evaporates the raw material without using a chemical reaction and deposits it directly on the substrate. Since this does not involve a chemical reaction, a film can be formed at a low temperature of about 500 ° C. to 700 ° C.

  Cemented carbide coating blades and guides coated with hard coatings by CVD and PVD methods have higher wear resistance and hardness than those of cemented carbide, and have a longer life. . However, a longer life cutting tool is desired. The present invention is a cutting tool that is more excellent in wear resistance and hardness than a tool in which a cemented carbide alloy is used as it is or a tool in which a cemented carbide base is coated with a hard coating, and can process a larger number of workpieces. The purpose is to provide.

Cutting tool of the present invention, the cemented carbide of the cutting edge and guide or cutting chips, once covered with hard coatings consisting of Ti compound, a portion of the coating thereby further lapping using diamond abrasive grains (lapping) machining This is an ultra-precision flat finish. Lapping, which is an example of abrasive processing, is a kind of polishing to reduce the thickness using an abrasive material such as diamond abrasive , but buffing (polishing) that includes diamond abrasive if the shape of the tool permits. Cloth, surface plate, abrasive grains, polishing liquid). Thereby, a part of the hard coating once formed is scraped off. As a result, the surface can be made smoother and flat, and wear due to processing can be prevented and the life can be extended.

  If the tool has many irregularities and cannot be flapped, abrasive particles are sprayed to scrape off part of the coating. Rather than scraping off the entire coating, a portion is removed.

It explains in order in more detail. The initial hard coating can be formed by CVD or PVD, but PVD is used in the present invention. According to the PVD method, a thin film of TiN, TiAlN or the like having a thickness of about 1 μm to 5 μm can be formed. For complex cutting tools brazing the cutting blade and guide in the tool body, since brazing is deviated when the 1000 ° C. as high as the CVD method, using the PVD method requires only 500 ° C. to 600 ° C. . Depending on the coating material, those with a hard coating exhibit a gold-colored appearance. The following titanium compound can be mentioned as an example of a hard film.

(Type of hard coating)
T iCNO
TiAlN
TiN

Conventionally, it was used as a cutting tool in such a form, but in the present invention, the coating is further partially removed by lapping using diamond abrasive grains . About 30% to 70% of the coating is removed by lapping. Such things are still colored with gold, etc., and the appearance does not change much, but the gloss seems to be slightly higher than the previous one (which does not wrap).

For example, a film with a 2 μm film is cut by 1 μm to a thickness of 1 μm. For example, a film with a film thickness of 5 μm is lapped to a thickness of 2 μm to 3 μm by lapping 2 μm to 3 μm .

The present invention is to provide a cutting tool life by coating removal by film formation + rapping grayed machining. Since initially the film formation is normally carried out in the usual cutting tools, the coating removal by subsequent rappin grayed machining is a novel twist.

I feel like it's a shame to remove a part of the hard coating. But the rapping grayed machining using diamond abrasive grains, cutting tool of the present invention by removing a part of the coating was found to have a cutting performance better than those that do not wrap (super-precision grinding).

  The present invention provides a cemented carbide cutting tool having a thinner coating by removing a portion of the hard coating once formed. As a result, the surface of the coating becomes smoother and a larger number of workpieces can be processed. This is an advantage of the present invention.

  That is, according to the present invention, it is possible to manufacture a cutting tool that has a much longer life than conventional cutting tools.

  For example, when drilling a hard steel sample of a certain size and composition using a tool with a TiAlN film of 2 μm formed by the PVD method, the blade edge becomes dull when 10 to 20 pieces are machined. lost. In other words, the life counted by the object to be processed is 10-20. When the same steel material sample was similarly drilled using the same cutting tool and a PVD-formed tool with a TiAlN film of 2 μm, 85 to 150 steel samples could be drilled. That is, the cutting tool of the present invention has a lifespan that is about 5 to 10 times longer than the conventional one.

  FIG. 1 shows a cutting tool 1a made of a so-called disposable throwaway tip, and FIG. 2 shows a cutting tool 1b in which a cutting tool 3 and a guide tip 4 are silver brazed on a cylindrical tool body 2, and these cutting tools are shown. A cutting tool obtained by PVD-coating TiAlN to a thickness of 2 μm over the entire la and la is designated as sample 1. Sample 2 was sprayed with diamond abrasive grains to remove a part of the coating at the tip (wrapping) to obtain an average thickness of 1 μm. When a long hole was drilled in the steel material to be processed using Sample 1 (without lapping), the blade edge was dulled and became unusable in about 10 to 20 pieces. When a long hole of the same size was drilled in the workpiece of the same steel material with Sample 2 (wrapped), 85 to 150 pieces could be processed.

In order to infer why there is such a significant lifetime difference, the surface roughness was examined.
The surface roughness was scanned with a surface roughness meter (Surlicet ST-400, manufactured by Mitoyo) using the length of 3 mm at the cutting edge of Samples 1 and 2 as the evaluation length. The results are shown in FIGS. The vertical axis is the coordinate in the length direction. One cm is 200 μm, and the total length is 15 cm. The horizontal axis is the height of the unevenness, and 1 cm is 1 μm.

  Sample 1 (not wrapped) has an average thickness of 2 μm, but it is only an average. As shown in the chart of FIG. 3, the thickness varies greatly. Therefore, the thickness is not 2 μm everywhere, but it may be 1 μm at a certain part and 3 μm at a certain part. In FIG. 3, the center vertical axis shows an average thickness of 2 μm, the left side shows a thickness thinner than 2 μm, and the left side 2 cm from the central vertical line is the base material (super high alloy background).

  A 3 μm thick part 1 μm thicker than the average is 4.8 cm from the top (960 μm from the measurement starting point). The portion has severe irregularities, and there is also a portion of 1 μm thickness 1 μm thinner than the average in the immediate vicinity. The fluctuation of the thickness in the vicinity thereof is large and shows a thickness variation of 1 μm to 3 μm. The height of the mountain is +1 μm and there are also +0.7 μm and +0.6 μm. There is also a portion of +0.5 μm. The valley (left from the center line) is the deepest part at -1 μm. There are four portions in the vicinity of −0.7 μm. There are more parts that exceed -0.5 μm. These parts form a steep mountain valley. Such a portion having a large local thickness fluctuation is also present at a portion of 4.1 cm from the top (820 μm from the measurement starting point).

Such local fluctuations suggest that the TiAlN coating is composed of a combination of fairly large polycrystalline particles.
In addition, the thickness of the upper portion of 7 to 8 cm (1400 to 1600 μm from the starting point) with little unevenness slowly changes in a wide range. The change in thickness is about 1 μm.

  On the other hand, FIG. 4 shows the result of the same inspection of film irregularities after lapping. Since the average thickness is 1 μm, the center vertical line indicates a height of 1 μm. 1 cm to the right corresponds to a thickness of 2 μm, and 1 cm to the left corresponds to a thickness of 0 μm. However, there is no portion having a thickness of 0 μm. The deepest valley is about -0.6 μm. Many are thicker than −0.5 μm. In addition to that, the locally uneven portion disappeared. The height of the mountain (the deviation from the center line to the right) is also about 0.5 μm at the maximum. The depth of the valley is also within −0.5 μm. Therefore, the unevenness is roughly included in the range of ± 0.5 μm on the left and right of the center line. Even in the case of 4.8 cm to 6 cm (960 to 1200 μm from the measurement starting point) having a relatively strong fluctuation, the peak is lower than +0.5 μm, and the valley does not exceed −0.5 μm. In this way, lapping has the effect of reducing not only the thickness but also the surface roughness.

  Although it is difficult to understand macroscopically, if you look closely, you can see the difference. Even if the unevenness is reduced, the unevenness is not uniform, and particularly the areas where the ridges and depressions are remarkable are corrected, and the portions with gentle unevenness from the beginning do not change much. Therefore, the number of surface irregularities is reduced as a whole, and the depth of the mountain valley is also reduced.

  Such reduction in surface irregularities may have caused the cutting tool after lapping to reduce friction with the metal surface of the workpiece and reduce the frequency of grain boundary separation. Even if a film having a thickness of 4 μm is first coated, the thickness does not continuously decrease from 4 μm → 3 μm → 2 μm → 1 μm by processing the workpiece. If there is a crystal grain boundary with a diameter of 4 μm to 3 μm and protrudes from the surface, it may be removed. In that case, the ground (fabric) is exposed at that portion. Since the base is a cemented carbide, the wear progresses quickly. In other words, if there is a large grain boundary projecting on the surface, it is easy to peel off when in contact with the object to be processed, and if it peels off, the life as a blade will end.

  In the present invention, since the surface is scraped off by lapping, the large grain boundaries are eliminated, the surface irregularities are reduced, and the possibility that the polycrystalline grain boundaries are peeled off due to contact with the workpiece is reduced. Therefore, it will be possible to process a larger number of workpieces than those that do not wrap even though the coating is thin.

  3 and 4 are compared, it can be seen that the above assumption is correct. Since it is difficult to express it numerically, the surface roughness of the tool cutting edge was measured and compared. The surface roughness has several definitions and uses an average value, so it does not necessarily represent the random structure of the micro surface. However, the only thing that can be calculated and defined directly is the surface roughness.

Before wrapping After wrapping (invention)
Arithmetic average roughness: Ra 0.14 μm 0.13 μm
Maximum height Ry 1.6μm 1.3μm
Ten-point average roughness: Rz 1.2 μm 1.0 μm
Root mean square height / Rq 0.18 μm 0.16 μm

  In addition to this, there is also Rmax, which is the difference between the maximum protrusion height and the minimum valley depth, and therefore does not express micro surface irregularities. So Rmax is not used. Ra is obtained by integrating the absolute value of the height with the average height as a reference and dividing the result by the number of points, and is an average of absolute values of deviation from the average value. Since this is averaged, it becomes the same regardless of whether there is local disturbance of the unevenness, so it is not necessarily suitable for expressing the smoothness of the cutting edge, but this was calculated. Since Ra is 0.14 μm before lapping and Ra is 0.13 μm after lapping, it can be seen that Ra is decreased by 0.01 μm and becomes smoother.

  Ry is the surface roughness that can reflect more local features. This determines the evaluation length (0.4 mm, 1.25 mm, 4 mm, 12.5 mm, 40 mm), and the reference length (0.08 mm, 0.25 mm, 0.8 mm, 2.5 mm, 8 mm), and the like, and the maximum peak height and the minimum valley depth are obtained among the reference lengths. The average of the sum of their height and depth is Ry.

  In other words, it is the average value of the height difference between the highest peak and the lowest valley at the reference length. The difference from Rmax that represents the difference between the maximum value and the minimum value as a whole is that Ry calculates the difference between the maximum value and the minimum value within the reference length. This surface roughness Ry naturally reflects local irregularities and irregularities more directly than Ra, by definition. Since the Ry value varies depending on the reference length and the evaluation length, the evaluation length and the reference length are determined by the Ry value. Here, since the evaluation length is 3 mm, the reference length is 0.6 mm. In the conventional example (without wrapping), Ry is 1.6 μm, but in the present invention (after wrapping), Ry is 1.3 μm.

  In other words, the sum of the depths of the ridges and grooves was reduced by lapping. That means that the difference in unevenness in a narrow area is reduced. Since abrasive grains are sprayed on the surface of the hard coating (TiAlN) or are buffed with abrasive grains, the peaks and valleys are similarly cut. Because it is narrow, the mountain is sharpened more significantly. It means that the height difference of Yamatani has decreased. Although it is a decrease of 0.3 μm, it can be seen that the average value has decreased so much that it is a considerably large decrease. Ry is a parameter that can express the local irregularity more strongly than Ra, but it can be seen that the reduction smoothness of unevenness due to wrapping is also enhanced.

  Another surface roughness Rz is that the evaluation length (0.4 mm, 1.25 mm, 4 mm, 12.5 mm, 40 mm) is determined and the reference length is (0.08 mm, 0.25mm, 0.8mm, 2.5mm, 8mm), and so on, focus on the highest mountain within the standard length and focus on the highest mountain from the highest mountain to the fifth. The sum of (the deviation from the average value) and the sum of the deepest valley and the sum of the depths up to the fifth (the absolute value of the deviation from the average value) counted from the deepest valley divided by 5 It is. This is not the difference in height (Ry) between the highest peak and the lowest valley in the reference length, but also the height difference between the four peaks and valleys adjacent to it. Similar to Ry, it is a parameter that easily reflects local fluctuations.

  When compared with the surface roughness Rz, Rz is 1.2 μm in the conventional example (without lapping), Rz is 1.0 μm in the present invention (after lapping), and there is a difference of 0.2 μm. It looks like a slight difference because it is only 0.2 μm, but there is a significant difference because it is a difference in average value. This result also means that the difference in the adjacent concavities and convexities is reduced because the mountain is sharpened by lapping and the valley is not cut so much.

The perspective view which shows the cutting tool which consists of a throwaway tip. The perspective view which shows the cutting tool which brazed the cutting blade and the guide tip to the tool main body. A graph showing the surface height distribution in a linear region with a reference length of 3 mm taken on a coating of a hard coating of TiAlN formed on a cutting tool made of cemented carbide with an average thickness of 2 μm by the PVD method (conventional example) . The vertical axis indicates the position on the reference length (50 times: 200 μm / cm), and the horizontal axis indicates the deviation from the average surface height (10000 times: 1 μm / cm) in the right direction. Ra was 0.14 μm, Ry 1.6 μm, and Rz 1.2 μm. On a coating of a hard coating of TiAlN formed on a cemented carbide cutting tool to a thickness of 2 μm on average by the PVD method and with a lapping treatment by spraying diamond abrasive grains to reduce the average thickness to 1 μm (Example) The graph which shows the surface height distribution in the linear area | region of 3 mm of reference length taken in. The vertical axis indicates the position on the reference length (50 times: 200 μm / cm), and the horizontal axis indicates the deviation from the average surface height (10000 times: 1 μm / cm) in the right direction. Ra was 0.13 μm, Ry 1.3 μm, and Rz 1.0 μm.

Claims (2)

The surface of the cutting tool prepared in cemented carbide, by physical vapor-phase synthesis method, coated TiAlN, TiCNO, thickness consisting of either Ti compound of TiN is a hard coating of 1 m to 5 m, the cutting thereafter By scraping the hard coating of the tool by lapping using diamond abrasive grains, the thickness of the hard coating is reduced by 30 to 70% , and the arithmetic average roughness Ra, maximum height Ry, and 10 % of the surface of the hard coating are reduced. A method for manufacturing a cutting tool, characterized in that the value of each surface roughness index of the point average roughness Rz and the root mean square roughness Rq is reduced as compared with that before lapping .   The method for manufacturing a cutting tool according to claim 1, wherein the hard coating is made of TiAlN.

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