JP4122437B2 - Atmosphere controlled cutting method by oxygen enrichment - Google Patents

Description

  The present invention relates to an atmosphere-controlled cutting method using oxygen enrichment in cutting with a machine tool.

Recently, in the field of machining, there has been a demand for machining technology that addresses environmental issues such as high-efficiency machining, conservation of the natural environment, and improvement of the working environment. Currently, it is practical in the machining field such as small-diameter ball end mills. High-speed dry shape processing is also possible. In addition to dry processing, MQL (Minimal Quantity Lubricant) and cold air processing have been actively studied, and the results are gaining results, and are becoming the mainstream of future processing modes including dry processing. . Furthermore, reduction of processing costs is one of the major issues.

  And as for the conventional atmosphere control processing which is a kind of dry processing, those for low oxygen atmosphere including cold air processing (see Patent Document 1), nitrogen blow at room temperature (see Patent Document 2), etc. are known. However, all of them are in a low oxygen atmosphere intended for oxidation prevention.

  Among these, the former is characterized in that tool wear is minimized and the grinding surface temperature is minimized by processing the steel in an inert gas atmosphere by grinding and controlling the oxygen concentration to around 12%. In particular, this example is characterized in that the amount of heat generated by processing and the solid lubricating action of the oxidation product are harmonized to realize a cooling effect and a lubricating effect by gas. However, a cover container is required to secure the atmosphere, and the inert gas to be supplied uses a gas cylinder, and there are problems in terms of cost and workability in actual processing.

On the other hand, in patent document 2, the apparatus which isolate | separates nitrogen gas from air | atmosphere using a hollow fiber membrane is blown into the tool blade edge | tip, and the steel-type material is processed in a low-oxygen atmosphere. Is the method. This method is excellent in practical use and cost.
Japanese Patent No. 2904205 US Pat. No. 6,135,862

  However, both methods target a low oxygen atmosphere. On the other hand, a low-oxygen atmosphere is usually desirable for steel-based materials from the standpoint of preventing oxidative wear of tools, but some materials are heavily welded at low oxygen, such as titanium alloys. Some may reduce lifespan. In addition, in order to stably generate an oxide-based protective film or attach it to a tool even in a material in which an appropriate amount of non-metallic inclusions for the purpose of forming belag or other oxides is included in a tool or workpiece. Low oxygen or non-oxidizing atmospheres are not suitable.

  In addition, as a gas supply nozzle used when controlling the atmosphere of a cutting part, as shown in Patent Document 2, a nozzle provided with a gas supply hole penetrating the shaft center of a tool body (end mill) is known. Yes.

  The thing of the said structure has fixed effectiveness since gas is supplied also to the blade edge | tip of a tool when a groove | channel and a hole are formed in the workpiece surface. However, when performing flat cutting or stepped machining with no cutting material on one side, most of the atmospheric gas is dispersed on the outer periphery other than the cutting part of the cutting edge or on the side without the cutting material, which prevents the supply of gas to the cutting edge. It is enough.

  An object of the present invention is to provide a cutting method based on atmosphere control in order to eliminate or improve the above problems. Specifically, the periphery of the tool edge and the work piece during cutting are made in a high oxygen (oxygen-enriched) atmosphere to generate oxides and reduce tool damage due to welding separation of the work material to the tool.

  And in this invention, in order to stabilize the production | generation of an oxide type protective film at the time of cutting the material which added the trace amount of the nonmetallic inclusion, the oxygen production | generation is promoted using high oxygen atmosphere gas.

  Furthermore, in the present invention, the oxide generation of the coated tool utilizing the lubricity of the oxide is promoted, and the tool life is extended by reducing the welding due to the lubricating action.

  In order to obtain these effects, in the present invention, oxygen-enriched gas is taken out from the atmosphere, or an oxygen gas cylinder is used, and a tool internal supply method (center through method or side through method) or an external supply method using a nozzle is used alone. Or in combination, and is supplied to the periphery of the cutting tool edge and the periphery of the workpiece to achieve oxide generation in a high oxygen atmosphere.

The method of the present invention for solving the above problem is first coated with a coating material containing an element that imparts lubricity by forming an oxide-based protective film between a tool and a workpiece during cutting . When cutting metal workpieces using a cutting tool, oxygen enriched to a high concentration at least higher than the oxygen concentration in the atmosphere as an atmospheric gas in a cutting method in which gas is supplied to the working part atmosphere for cutting. It is characterized in that tool damage / wear is reduced by generating an oxide between the cutting edge of the cutting tool 4 and the work piece by supplying a gas containing gas to a high-concentration oxidizing atmosphere in the work part.

  Second, the atmospheric gas is oxygen-enriched air obtained by concentrating oxygen in the atmosphere.

  Thirdly, it is characterized in that the oxygen concentration of the atmospheric gas includes a range exceeding the oxygen concentration of the atmosphere and up to 40%.

  Fourth, the supply of the atmospheric gas to the processing part is made by an external supply method in which the nozzle is blown from the outside of the cutting device, an outer periphery supply method for supplying along the outer periphery of the cutting tool 4, and a cutting tool is provided inside. It is characterized in that it is performed by one type of internal supply type that supplies and discharges through a hole or in combination of two or more types.

According to the present invention configured as described above, an oxide- based protective film is applied to a workpiece or tool by supplying high-concentration oxygen as a cutting atmosphere gas and making the cutting portion an oxidizing atmosphere with high-concentration oxygen. In the case where the element that forms the element is included, the oxide- based protective film is stably formed between the tool blade edge and the cutting surface of the workpiece, or is attached to the surface of the tool edge to reduce tool wear. And cooling of a cutting part and a tool is realizable by concentrating and supplying the said high concentration oxygen to a cutting part.

  Further, the performance of the lubrication-imparting type coating tool by oxide generation can be sufficiently obtained, and processing with these effects can be realized easily and at low cost by a relatively simple apparatus.

Hereinafter, embodiments of the present invention will be described in detail.
In an embodiment of the present invention described below, high oxygen (oxygen-enriched) gas taken out from the atmosphere or using a gas cylinder is blown near the tool edge, and oxidized in the high oxygen atmosphere on the processed surface (new surface) of the material. In addition, the tool blade edge is made an oxidizing atmosphere with respect to the material for generating the bellage, and TiC in the tool, which is a condition for attaching the protective film, is oxidized on the tool surface to generate TiO ₂ .

Further, in the present invention, Fe contained in the work material promotes oxide formation in which FeO is formed, and an oxide formed by Si, Mn, Al, Mg, etc., which are constituent components of steel, cast iron, mold steel, and the like, is a main component. An oxide- based protective film is stably generated or adhered between the tool blade edge and the workpiece surface. This further ensures the effect of preventing direct contact between the tool and the workpiece and its chips and suppressing wear.
A high oxygen atmosphere or a high oxygen gas blow is performed in order to bring out the performance of the coating tool of the lubricity imparting type by oxide generation.

  The lubricity imparting type coating tool imparts lubricity by forming an oxide. For example, as in the case of TiBON, an element that increases the lubricity of the oxide (in this case, B = boron) is added. It is included in the material and is oxidized by cutting to reduce the wear coefficient and prevent welding and the like.

  For this purpose, an oxygen-enriched gas atmosphere is used to promote the formation of the oxide coating film, thereby reducing tool wear and extending the tool life.

  Next, an embodiment of the present invention will be described. A processing apparatus for carrying out the method of the present invention comprises a gas supply device 1 (or a gas cylinder), a machine tool 2, a tooling 3, and a tool 4 as shown in FIG. The gas supply device 1 includes an oxygen enrichment unit 6, a tank 7, a control unit 8, a solenoid valve, an oxygen concentration meter (all not shown), and the like, and supplies a gas having a predetermined oxygen concentration to the machine tool 2. The machine tool 2 can be applied to any of a milling machine, a machining center, a lathe, a drilling machine, a hobbing machine, a grinding machine, and the like. In this embodiment, the tool periphery and gas supply method will be described by taking end milling as an example. Further, as the gas supply device 1, an oxygen enrichment device shown in Japanese Patent Gazette, Japanese Patent Publication No. 5-23809, etc., and an oxygen enrichment film, for example, shown in Japanese Patent Gazette, Japanese Patent Publication No. 7-77602, etc. I used something. Since these oxygen enrichers concentrate oxygen by passing the atmosphere through an oxygen enriched film, it is possible to stably obtain a gas containing oxygen at a high concentration of at least about 32.5%. It is possible to obtain a gas with a concentration of 40%.

  A tooling 3 attached to a machine tool 2 such as a milling machine or a machining center is a special holder of a center through type or a side through type, and supplies gas from an internal supply hole formed in a tool. Or it can also spray on the periphery of the cutting edge of the tool (end mill) 4 using an external nozzle 9 as shown in FIG. In the case of the internal supply method, not only the supply hole but also the supply method of covering the periphery of the tool in the form of an air curtain is possible, and their combined use is also possible.

  FIG. 2 is an overall side view of the tool (end mill) 4 used in this embodiment. In this example, a two-spindle blade type is used, and the gas supply hole 4b is formed at the center of the tool body from the base end side. Is drilled up to the inside of the tip of the tool body. Then, in the inside of the tip, the opening (gas jet) 4c extends to the outer peripheral side at an inclination angle θ in the branch hole 4e so as to open into each groove 4d of the tool 4 toward each cutting edge 4a. The gas branched and supplied from the base end side is structured to be intensively ejected toward the cutting edge 4a (that is, the cutting portion) of the tool 4 being cut.

  FIG. 3 shows a schematic diagram of a side-thru type special holder 11 and a gas ejection state when the tool is mounted. A tool 12 is attached to the peripheral wall of the holder 11 and a plug 12 for connection to the gas supply pipe 5 is mounted. A gas supply hole 13 communicating with the inside is formed at the base end of each of the four gas supply holes 4b (see FIG. 2).

  Further, the lower end portion of the gas supply hole 13 in the holder 11 is provided with an opening 16 that is opened in a ring shape at the outer peripheral position of the tool in the collet nut 14 on the holder 11 side, and is normally supplied with oxygen. The enriched gas is jetted and supplied to the tool tip side along the outer periphery of the tool 4 from the nozzle 4 c at the tip of the tool 4 and the ring-shaped opening 16. If the tool 4 without the gas supply hole 4b is used, the gas is supplied only to the outer peripheral side of the tool.

  However, the ring-shaped opening 16 has a structure in which an O-ring (not shown) can be removably mounted so as to close the opening 16. The gas supply from the opening 16 is stopped, and the gas supply from only the ejection port 4c of the tool 4 is performed. As far as the oxygen concentration measurement result of the cutting atmosphere is concerned, it is desirable to use both the above gas supply methods in combination.

  FIG. 4 is a schematic view showing a state in which the tool 4 on the workpiece 17 is ejected from the plurality of gas supply nozzles 9 toward the tip (machined portion). In this example, a stepped portion 17a is formed at a cross-sectional corner of the workpiece 17. To do. In this state, the gas is surely supplied to the processing portion by being ejected from the ejection port 4c opening toward the tool cutting edge 4a.

FIG. 5 shows the same conditions for the titanium alloy by changing the oxygen concentration of the supply gas (cutting speed V = 50 m / min, radial cut dr = 0.5 mm, axial cut da = 3 mm, feed speed f = 0. .015 mm / tooth) is a graph showing the progress of flank wear of the end mill side cutting edge. As is clear from this figure, it is shown that the initial wear is large in the low-oxygen nitrogen gas blow, and the wear is the largest compared with the other. On the other hand, it can be seen that the wear decreases as the oxygen concentration in the cutting atmosphere increases from the air to a high oxygen concentration (32.5% O ₂ ).

  FIGS. 6A, 6B, and 6C show the periphery of the end mill corner (blade edge) when nitrogen, air, and a high oxygen concentration gas are respectively supplied as the atmosphere gas and the cutting length L = 30 m is cut. (A), (b), and (c) in each figure show the tip surface, groove side inner surface, and outer peripheral surface of the tool cutting edge, respectively.

  According to FIG. 6 (A), the flank wear near the corner portion is larger in the nitrogen blow compared to the others. This is probably because the machined surface (new surface) was not oxidized in a low oxygen state, and highly active titanium adhered to the tool surface and increased due to the welding delamination phenomenon. On the other hand, although not much wear is observed in the atmosphere shown in FIG. 6B, chip welding is observed on the cutting edge.

  On the other hand, as shown in FIG. 5C, when the oxygen concentration is further increased, chip welding to the cutting blade is not observed, and wear is hardly observed. This is thought to be due to a decrease in the adhesion peeling phenomenon due to the fact that highly active titanium does not directly contact the tool surface as a result of the formation of oxide on the new surface by oxidation.

  If the above result is a difference in the degree of oxidation (difference in the degree of oxide formation), the difference will be more noticeable under conditions where the tool tip temperature is more likely to oxidize, that is, under conditions where the cutting speed is high. Can be estimated.

  FIGS. 7 (A) and 7 (B) show the results of testing the effect of cutting atmosphere on tool wear under the same conditions as in the above example at a cutting speed of 200 m / min. It is a graph shown about abrasion of a blade part. Although there is no difference in the wear of the corner portion (blade edge portion) due to the difference in atmosphere, the wear of the side cutting blades becomes incapable of cutting at a stage where the cutting speed is shorter as the oxygen content is lower. At this time, the wear near the boundary portion becomes large, and the tool cutting edge deteriorates the sharpness of the material. From the above, it can be seen that the processing using the reduction of welding due to oxide generation in a high oxygen (oxygen-enriched) atmosphere is effective for a material such as a titanium alloy.

  In addition, as described above, there is a type of coating that includes an element in which the oxide exhibits high lubricity in a recent coating material, oxidizes it by cutting heat, and imparts lubricity to the coating film. It has been developed (for example, TiBON). It is effective to utilize a high oxygen atmosphere to facilitate the oxide formation of such coating materials and to bring out the performance of the coating tool.

  For example, FIGS. 8A and 8B show tool edges (corner portions) and side surfaces when a titanium alloy is cut with a conventional TiAIN coating tool and a lubrication-provided TiBON coating tool by oxide formation in a high oxygen atmosphere. The result of comparing the wear progress in the cutting edge is shown. Each cutting condition is as shown in each graph. According to this result, it can be seen that the conventional coating shows a certain degree of cutting performance, but the lubricious coating hardly progresses after the initial wear. When the cutting distance is 30 m, the wear amount is about ½ of TiAIN. However, if it changes in this form, it is expected that the life difference will be a considerable difference (at least several times to several tens times). Titanium alloys have a high weldability, so it is considered that the effect appears remarkably.

In addition, although the said Example demonstrated the case where an end mill was used as a tool, the method and cutting tool of this invention use a milling tool, a drill, a cemented carbide tool, and other cutting tools, as long as the material of a workpiece and a tool is suitable. It can also be applied to cases. Further, as long as the oxide- based protective film is formed during cutting, the higher the oxygen concentration of the supply gas, the better the efficiency. However, it is not necessary to be 32.5% as shown in the examples, and at least the atmosphere It is necessary that oxygen enrichment is performed more than the oxygen concentration therein to form an atmosphere of high concentration oxygen, and it is possible to use a gas having an oxygen concentration of about 40% obtained by oxygen enrichment.

  The present invention can be applied to general metal cutting with a machine tool.

It is a schematic diagram of a processing device for carrying out the present invention. It is a side view which shows one example of the cutting tool of this invention. It is a front view which shows an example of the tool holder used for implementation of this invention. It is a perspective view which shows the other Example of the gas supply method of this invention. It is a graph which shows the wear progress state of a side blade at the time of cutting a titanium alloy. (A), (B), (C) are enlarged photographs showing the tool wear state when a titanium alloy is cut in each atmosphere of nitrogen gas, air, and high-concentration oxygen. (A), (B) is a graph which shows the abrasion state of the tool corner part and side cutting edge part at the time of cutting titanium alloy in each atmosphere of nitrogen gas, air | atmosphere, and high concentration oxygen. (A) and (B) compared the progress of wear at the tool edge corner and side cutting edge when a titanium alloy was cut with a conventional TiAIN coated tool and a lubricated TiBON coated tool by oxide formation. It is a graph which shows a result.

Explanation of symbols

4 Tool 4a Cutting edge 4b Gas supply hole 4c Spout

Claims (4)

During cutting of metal workpieces using a cutting tool coated with a coating material containing an element that imparts lubricity by forming an oxide-based protective film between the tool and the workpiece during cutting, the working part atmosphere In a cutting method in which gas is supplied to the cutting process, a gas containing oxygen enriched at a high concentration higher than the oxygen concentration in the atmosphere is supplied as an atmosphere gas to make the processing part a high concentration oxidizing atmosphere. An atmosphere-enhanced cutting method by oxygen enrichment that reduces oxide damage between the cutting edge of the cutting tool (4) and the workpiece, thereby reducing tool damage and wear.   2. The atmosphere-controlled cutting method by oxygen enrichment according to claim 1, wherein the atmosphere gas is oxygen-enriched air obtained by concentrating oxygen in the atmosphere.   The atmosphere control cutting method by oxygen enrichment according to claim 1 or 2, wherein the oxygen concentration of the atmospheric gas includes a range exceeding the oxygen concentration of the atmosphere and up to 40%.   An external supply type in which the atmosphere gas is supplied to the processing portion by using a nozzle from the outside of the cutting apparatus, an outer periphery supply type in which the cutting gas is supplied along the outer periphery of the cutting tool (4), and a hole drilled in the cutting tool. The atmosphere control cutting method by oxygen enrichment according to claim 1, 2 or 3, which is carried out by one kind of an internal supply type which is discharged and supplied through a combination of two or more kinds.

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