JP3985947B2 - Coating brooch - Google Patents

Description

[0001]
[Technical field to which the invention belongs]
The present invention relates to a cutting edge treatment of a coating broach in which a large number of cutting edges are coated with a hard film.
[0002]
[Prior art]
The structure of a general single broach is equipped with a series of cutting edge groups consisting of a rough cutting edge group, an intermediate finishing edge group, and a finishing edge group with different cutting amounts on the cutting edge, and machining is completed in one drive process. It is suitable for the mass production process of molded products. The life of the broach is determined by the wear width of the flank face of the cutting edge. When the wear of the cutting edge becomes severe, the surface roughness of the finished surface is greatly deteriorated and the life is reached. In addition, since the resistance at the time of processing increases, there is a problem that heat generation at the time of cutting is accompanied and the target processing accuracy cannot be obtained. Therefore, it has been proposed to coat the cutting edge with a hard film for the purpose of improving cutting performance and life and increasing accuracy. This is because the wear of the cutting edge of the cutting edge is reduced by the hard coating, which leads to improvement in processing accuracy. For example, Japanese Patent Application Laid-Open No. 11-300518 discloses a broach in which a TiAlNC coating is coated on at least the flank face of a cutting edge. Japanese Patent Laid-Open No. 2001-157910 discloses a broach covered with a TiAlN-based multilayer coating.
[0003]
[Problems to be solved by the invention]
However, when a portion near the cutting edge is observed with a FE type scanning electron microscope after forming a hard film on the broach, it is transferred in accordance with the shape of the grinding stripe, and especially on the cutting edge ridge line, the grinding stripe from the rake face is transferred. Since the grinding striations from the flank intersect, the cutting edge ridge is uneven. Further, the hard coating applied to the broaching blade tip has a problem that the edge effect is obtained at the cutting edge ridge line portion composed of the rake face and the flank face, the coating tends to be thick, and the coating is liable to be peeled off. Furthermore, droplets or the like that are defects during film formation by vapor deposition are also generated. These cause unfavorable causes such as chipping and film peeling in the initial stage of cutting. Therefore, a method of performing a cutting edge treatment after forming a hard film is taken, but in the case of a broach, since there are a large number of cutting edges and the dimensions of each cutting edge are different, it is conventional to process the film In the cutting process using a CBN grindstone or a cutting edge processing method using a brush, buff, etc., the edge of the cutting edge becomes non-uniform, and if the film thickness after the cutting edge processing is not constant, the substrate part is exposed. There is a problem that said.
[0004]
[Means for Solving the Problems]
In the present invention has a number of cutting edges on the tool body, in the coating broach coated with hard coating, the rake face side of the該切Re blade vicinity are uncoated surface, flank side of該切Re blade vicinity, A coating broach in which defects such as droplets on the surface of a hard coating and irregularities due to transfer of grinding marks are removed by polishing.
[0005]
[Embodiment]
In the present invention, if the surface roughness of the cutting edge of the substrate by grinding is first improved and the film is formed on a mirror-like finished surface having no irregularities due to grinding marks, the state after film formation is It is improved to some extent. However, since droplets that are defects due to vapor deposition exist on the surface after film formation, and the surface roughness is deteriorated even if the mirror surface is finished, the present invention focuses on the cutting edge processing after film formation. did.
[0006]
1stly, the film formed in the cutting edge ridgeline part by the edge effect in the rake face side is removed by grinding, and it is set as a non-coating surface. Secondly, as a result of studying a method that can reduce the force and efficiently perform the coating polishing of the cutting edge flank, the method of polishing by shot blasting, the proper selection of the medium to be used, the medium discharge amount, the discharge pressure It was found that polishing can be performed in a short time with a very small force by adjusting, and even a large number of cutting edges can be polished uniformly. Therefore, in the present invention, after film formation, polishing by shot blasting is applied to the flank face coating of the broach.
[0007]
In the state after the removal of polishing, only a region having a slight uneven ridgeline is removed by polishing by shot blasting, and there is no grinding trace in the removed portion. Further, defects at the ridge line, particularly droplets that are defects generated during vapor deposition, are also removed by shot blasting. In the present invention, by applying an appropriate cutting edge treatment after coating the hard coating, the maximum surface roughness Ry of the flank surface is set to 1 μm or less, and a great effect is obtained for improving the cutting performance and extending the life of the broach.
[0008]
In the broach having a large number of cutting edges, Al2O3, TiAlN, TiN, TiCN, TiBN, CrSiN, Cr carbide are provided on the surface of the cutting edge flank for the purpose of improving the wear resistance and preventing the formation of the cutting edge. , CBN, diamond and other known coatings can be applied. The laminated structure at this time may be one in which one kind selected from the group of hard materials is coated, for example, a two-layer structure in which the first layer is coated with TiN as the second layer and CrSiN or the like, and further A three-layer structure in which both solid solution layers are provided between the first layer and the second layer to further improve the adhesion between them is effective as the present invention. By setting the surface roughness of the cutting edge flank to 1 μm or less at the maximum surface roughness Ry, it is effective to suppress the wear amount of the flank. More preferably, the wear amount can be reduced more stably by setting the thickness to 0.5 μm or less. However, when the maximum surface roughness Ry exceeds 1 μm, the amount of wear increases and there is a problem in wear resistance. When the total thickness of the coating layer is 0.2 μm or less, there is a problem that the effect on the wear resistance is small, and when the thickness is 10 μm or more, the coating layer is easily peeled off. In a spline broach or the like that requires high processing accuracy, the thickness of the coating layer is preferably 0.5 to 3.0 μm. Hereinafter, the present invention will be described based on examples thereof.
[0009]
【Example】
As an example of the present invention, an example applied to a spline broach made of high-speed tool steel for machining joint spline holes will be described. The specification includes a maximum diameter of 29.8 mm, the number of teeth of 15, a total length of 660 mm, 41 rough cutting edges, and 10 finishing edges. In the cutting blade, the cutting amount of one blade is 0.075 mm, and a TiAlN film having a thickness of 1 μm is applied to the cutting blade flank portion of the broach. Furthermore, in the example of the present invention, as shown in FIG. 1, the flank side of the cutting edge is blast-polished to remove the unevenness of the cutting edge due to the grinding streak and to remove droplets and the like that are defects due to vapor deposition. In particular, the edge line was made uniform by the blade edge treatment after film formation. For polishing by shot blasting, a medium containing diamond was used, and the surface roughness Ry of the TiAlN coating surface on the cutting edge flank side of the broach was 0.5 μm or less. On the rake face side, the film formed on the edge portion of the cutting edge due to the edge effect was removed by grinding to make an uncoated surface. On the other hand, the conventional example is a broach having the same shape as the example of the present invention, and the portion near the cutting edge is transferred according to the shape of the grinding mark as shown in FIG. Since the grinding streak and the grinding streak from the flank face intersect, the cutting edge ridge is uneven. FIG. 3 compares the cutting edge flank of the present invention example and the conventional example. Before polishing by shot blasting, the flank roughness was 1.73 μm in Ry, but improved to 0.40 μm in Ry after processing.
[0010]
Subsequently, the present invention example was compared with the conventional example by cutting evaluation. The cutting specifications are as follows. The work material was nickel chrome molybdenum steel (SNCM material), the cutting length was 24 mm, and the material was cut at a cutting speed of 5 m / min. The evaluation was performed by measuring the average wear amount of the flank portion by measuring the dimensional change. FIG. 4 shows a comparison of cutting edge wear between the example of the present invention and the conventional example. When the amount of wear of the cutting edge flank is compared at the time when a predetermined number of 5000 pieces are processed, the example of the present invention is the conventional example. Compared with the case where the surface roughness is rough, the wear amount is small and stable. This effect is obtained even when a TiN coating other than the TiAlN coating, a TiCN coating, a CrSiN coating, a TiBN coating, or the like is used.
[0011]
When machining can be performed with high precision by slight abrasion of the cutting edge as in the present invention example, the fitting accuracy between the hole and the shaft of the joint is improved, the noise of the teeth and vibration can be reduced, and the quality of the joint can be improved. Furthermore, since the effect of the coating can be superimposed in addition to the characteristics of the high alloy powder high speed steel, a high performance improvement can be obtained. In addition, the curl state of chips, chip removability, machined surface roughness, and tool edge wear state are taken up as evaluation items for broaches, and all of them show good results.
[0012]
By applying the present invention, a hard coating is used as the coating material, so the pressure resistance of the coating is large, and the TiAlN coating has excellent oxidation resistance and a lubricating effect that can be expected. This is a remarkable effect.
[0013]
【The invention's effect】
From the above results, it is possible to improve the quality of the surface to be cut and improve the cutting performance by reducing the unevenness of the cutting edge ridge line by polishing by shot blasting after film formation. In particular, polishing by shot blasting is applicable not only to a spline broach but also to a surface broach and the like, and since the ridge line is particularly uniform, it is extremely useful as a means for improving the surface to be cut. The same effect can be obtained when the material of the broach substrate is not limited to high-speed tool steel but is also made of cemented carbide. Further, the means for polishing by shot blasting is not limited to a method using a medium containing diamond, and a method such as magnetic polishing using a magnetic medium can also be applied. By applying the present invention, it is possible to obtain a broach suitable for mass production, which can be cut stably for a long time with few machining errors.
[Brief description of the drawings]
FIG. 1 is an enlarged view of a main part of an example of the present invention.
FIG. 2 is an enlarged view of a main part of a conventional example.
FIG. 3 is a comparative view of cutting edge flank surfaces of the present invention example and a conventional example.
FIG. 4 is a comparison diagram showing test results of the present invention example and a conventional example.
[Explanation of symbols]
1 Cutting edge rake face 2 Cutting edge ridgeline 3 Cutting edge flank

Claims (3)

Has a number of cutting edges on the tool body, in the coating broach coated with hard coating, the rake face side of the該切Re blade vicinity are uncoated surface, flank side of該切Re blade near, the hard coating surface A coating broach in which defects such as droplets and irregularities due to transfer of grinding marks are removed by polishing.   2. The coating broach according to claim 1, wherein the surface roughness of the surface to be polished is 1 [mu] m or less in terms of the maximum surface roughness Ry. The coating broach according to claim 1 or 2, wherein the hard coating is Al, Si, B, Periodic Table Group 4a, 5a, Group 6a transition metal carbide, carbonitride, nitride, oxide, boride, and One or two or more hard coatings selected from the group consisting of boron carbide, hard boron nitride, hard carbon, and solid solutions or mixtures thereof, and a thickness of 0.2 to 10 μm in one or more layers. Coating broach characterized by being coated with.

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