JP4539049B2 - A surface-coated cemented carbide barbing tool with excellent wear resistance in high-speed gear cutting. - Google Patents

Description

  In particular, the present invention does not cause thermoplastic deformation in the tooth portion even when gear cutting of various steel gears is performed under high-speed gear cutting conditions with high heat generation. Therefore, the present invention relates to a surface-coated cemented carbide striping tool (hereinafter referred to as a coated cemented carbide cutting tool) that exhibits excellent wear resistance over a long period of time.

Conventionally, various gears are generally used as structural members for automobiles, aircrafts, and various drive devices, and coated carbide gear cutting tools (solid hobs) are used for gear cutting of gear teeth.
Further, as shown in the schematic perspective view of FIG. 2, for example, the coated cemented carbide cutting tool has a plurality of tooth grooves formed radially along the rotation axis and along the length direction. In addition, a tooth portion that is formed by a front and rear surface that faces the tooth gap and whose front surface is a rake face with respect to the rotation direction, and a top surface (tooth tip tooth surface) and both side surfaces (left and right tooth surfaces) that are flank surfaces. Is formed on the surface of a tungsten carbide based cemented carbide cutting tool body (hereinafter referred to as a cemented carbide cutting base) machined into a shape continuously formed along the length direction. A coated carbide gear cutting tool formed by physically vapor-depositing a hard coating layer composed of a layer (indicated by TiN) with an average layer thickness of 0.9 to 15 μm is known.
Japanese Patent Laid-Open No. 10-146720

  In recent years, the performance of gear cutting machines has been remarkably improved. On the other hand, there is a strong demand for labor saving and energy saving and further cost reduction for gear cutting, and with this, gear cutting has a tendency to increase in speed. In the above conventional coated carbide gear cutting tool, there is no problem when it is used under normal gear cutting conditions, but especially when gear cutting is performed under high speed conditions with high heat generation, the tooth Thermoplastic deformation occurs in the part, and this causes wear to take an uneven wear form. As a result, the progress of wear is remarkably accelerated, so that the service life is reached in a relatively short time.

In view of the above, the inventors of the present invention have developed the above-mentioned conventional coated carbide hobbing tool in order to develop a coated carbide hobbing tool that does not cause thermoplastic deformation in the tooth portion, particularly in high-speed gear cutting. As a result of conducting research with a focus on
(A) In the coated carbide gear cutting tool having the above structure, the work material slides into contact with the flank surface composed of the top surface (tooth tip tooth surface) and both side surfaces (left and right tooth surfaces) of the tooth part. In the state where the front rake face of the front and rear faces is a chip contact surface, gear cutting is performed with a cutting blade where the flank face and the rake face intersect. A large amount of frictional heat is generated between them, but the generated frictional heat once moves into the tooth part and is radiated from the front and rear surfaces including the rake face of the tooth part.
(B) In the gear cutting mode of (a) above, the faster the gear cutting, the greater the frictional heat generated between the flank face of the tooth and the work material, thereby the tooth The temperature rises further, and thermoplastic deformation occurs in the teeth.
(C) As a base layer of a hard coating layer made of a TiN layer on the tooth flank where heat generation is remarkable in high-speed gear cutting,
A composite nitride of Ti and Al satisfying the composition formula: (Ti _1-X Al _x ) N (wherein X is 0.40 to 0.65 in atomic ratio) [hereinafter referred to as (Ti, Al) N] layer,
When the Ti is interposed, the (Ti, Al) N layer has a lower thermal conductivity due to the solid solution of Al as compared with the TiN layer having a good thermal conductivity, and rather has a good heat insulating property. Therefore, heat transfer to the inside of the tooth portion of frictional heat generated between the flank face of the tooth portion and the work material is remarkably suppressed by the (Ti, Al) N layer.
(D) In the coated cemented carbide cutting tool in which the (Ti, Al) N layer is interposed as the underlying layer of the TiN layer on the tooth flank surface of (c) above, during high-speed gear cutting as described above, The frictional heat generated between the flank of the tooth part and the work material is suppressed from being transferred to the inside of the tooth part by the (Ti, Al) N layer as the underlayer, while the heat inside the tooth part is heat. Since only the TiN layer with good conductivity is radiated from the front and back surfaces including the rake face of the coated tooth, the temperature rise inside the tooth is prevented despite high-speed gear cutting with high heat generation. As a result, since there is no thermoplastic deformation of the tooth portion, uneven wear that causes wear promotion does not occur in the tooth portion, and it takes a normal wear form, so it has excellent wear resistance over a long period of time. To demonstrate.
(E) However, in (d) above, if the (Ti, Al) N layer having a high heat insulating effect is formed on both the front and back surfaces including the flank and rake face of the tooth portion as the underlying layer of the TiN layer, The heat of the teeth comes to the inside, and the internal heat of the teeth becomes high over time in high-speed machining, and the teeth are subjected to thermoplastic deformation that causes accelerated wear.
The research results shown in (a) to (e) above were obtained.

The present invention has been made on the basis of the above research results, and a plurality of tooth spaces are formed radially and along the length direction with respect to the rotation axis. The tooth part that consists of the front and rear faces that face the groove and the front face is a rake face with respect to the rotation direction, and the top face (tooth tip tooth face) and both side faces (left and right tooth faces) that are flank faces Coated carbide teeth formed by physically vapor-depositing a hard coating layer made of a TiN layer with an average layer thickness of 0.9 to 15 μm on the surface of a cemented carbide cutting base having a shape formed continuously along the direction In cutting tools,
The top surface (tooth tip tooth surface) and both side surfaces (left and right tooth surfaces) constituting the flank of the tooth part have an average layer thickness of 0.1 to 5 μm as an underlayer of the hard coating layer, and Physical vapor deposition of a heat insulating layer composed of a (Ti, Al) N layer satisfying the following composition formula: (Ti _1-X Al _x ) N (wherein X is 0.40 to 0.65 in atomic ratio) Thus, the present invention is characterized by a coated carbide gear cutting tool that exhibits excellent wear resistance in high-speed gear cutting.

Next, the reason why the composition and the average layer thickness of the hard coating layer and the base layer constituting the coated carbide gear cutting tool of the present invention are limited as described above will be described.
(A) Average layer thickness of hard coating layer (TiN layer) If the average layer thickness of the TiN layer constituting the hard coating layer is less than 0.9 μm, the desired wear resistance cannot be ensured, whereas the average layer If the thickness exceeds 15 μm, chipping is likely to occur at the cutting edge, so the average layer thickness was set to 0.9 to 15 μm.

(B) Composition of the underlayer and average layer thickness As described above, the (Ti, Al) N layer constituting the underlayer is composed of a part of TiN Ti substituted with Al, and was excellent by the inclusion of Al. It has heat insulation, but the X value indicating the Al content ratio is the ratio of the total amount with Ti (atomic ratio, the same shall apply hereinafter). Insufficient heat insulation to prevent heat transfer to the inside of the heated tooth part, on the other hand, if the X value indicating its content rate is also higher than 0.65, the high temperature strength is increased. As a result, the base layer itself is easily cracked. As a result, the crack propagates to the hard coating layer and causes chipping. Therefore, the X value is 0.40 to 0.65. Determined.
Also, if the average layer thickness is less than 0.1 μm, the heat insulating effect in high-speed gear cutting is insufficient, while if the average layer thickness exceeds 5 μm, the underlayer itself is liable to crack. Since cracks propagate to the hard coating layer and cause chipping, the average layer thickness was determined to be 0.1 to 5 μm.

  The coated carbide gear cutting tool of the present invention, in which a (Ti, Al) N layer is interposed only as a base layer of a TiN layer, which is a hard coating layer, only on the flank face of the tooth portion, is capable of gear cutting of steel gears with high heat. Even when performed under high-speed conditions with generation, the temperature of the inside of the tooth portion is prevented by the action of the base layer, and the tooth portion is prevented from undergoing thermoplastic deformation. As a result, excellent wear resistance is exhibited over a long period of time.

Next, the coated carbide gear cutting tool of the present invention will be specifically described with reference to examples.
As raw material powders, WC powder, VC powder, TaC powder, NbC powder, Cr ₃ C ₂ powder, TiN powder, (W, Ti) C [w / w, WC / TiC by mass ratio, all having an average particle diameter of 1 to 3 μm. = 50/50] powder and Co powder are prepared, and these raw material powders are blended in the blending composition shown in Table 1, wet mixed by a ball mill for 24 hours, dried, and then pressed into a compact at a pressure of 100 MPa. The green compact is pressed and sintered in a nitrogen atmosphere of 2 KPa at a temperature of 1400 ° C. for 1 hour to form a cemented carbide round bar material of diameter: 85 mm × length: 125 mm. The solid hob-type carbide gear cutting base body A shown in FIG. 1 having an overall size of outer diameter: 80 mm × length: 120 mm and having a shape of three right-hand twists × 17 grooves by machining from this material. ~ F were produced respectively.

  Next, each of the above-mentioned superhard gear cutting bases A to F is ultrasonically cleaned in acetone and dried, and is shown in a schematic plan view in FIG. 1A and a schematic front view in FIG. Installed on the rotary table in the arc ion plating apparatus at a predetermined distance in the radial direction from the rotation axis with a predetermined interval along the outer peripheral portion, and various component compositions as a cathode electrode (evaporation source) on one side Ti-Al alloy for underlayer formation, and cathode Ti (evaporation source) on the other side, metal Ti for hard coating layer formation and bombard cleaning, facing each other across the rotary table, first exhaust the inside of the device Then, while maintaining the vacuum at 0.5 Pa or less, the inside of the apparatus is heated to 500 ° C. by a heater, and then the DC bias voltage of −1000 V is applied to the carbide cutting base rotating while rotating on the rotary table. When applied, a current of 100 A is allowed to flow between the metal Ti of the cathode electrode and the anode electrode to generate an arc discharge, whereby the surface of the cemented carbide cutting substrate is cleaned by Ti bombardment, and then nitrogen as a reactive gas in the apparatus. A gas is introduced to make a reaction atmosphere of 10 Pa, a DC bias voltage of −100 V is applied to a carbide cutting base rotating while rotating on the rotary table, and the cathode electrode and anode electrode of the metal Ti A current of 100 A is passed between them to generate an arc discharge, so that the entire surface of the cemented carbide cutting base, that is, the front and rear surfaces whose front surfaces are raked with respect to the rotation direction, and the top surfaces (tooth tips) which are flank surfaces. (Ti, Al) N layer as a base layer having the target composition and target thickness shown in Table 2 is formed by vapor deposition on the entire surface including the tooth portion composed of the tooth surface) and both side surfaces (left and right tooth surfaces). Thus, in the state where the (Ti, Al) N layer as the base layer is formed on the entire surface of the cemented carbide cutting base, it is taken out from the apparatus, and is radially and over the entire length as shown in FIG. Grinding is performed using a disk-shaped rotating diamond grindstone along the tooth front surface and the tooth rear surface, which are rake faces facing each other with the formed tooth gap interposed therebetween, and the (Ti, Al ) After removing the N layer, it was charged in the apparatus again, and a current of 100 A was passed between the cathode electrode and the anode electrode of the hard coating layer forming metal Ti to generate an arc discharge. On the entire surface of the cemented carbide cutting substrate in which the (Ti, Al) N layer as the underlayer is formed only on the flank surface under the same conditions as the formation conditions of the (Ti, Al) N layer as the underlayer, It consists of TiN layer of the target layer thickness shown in 2. The coated carbide cutting tools 1 to 6 of the present invention were produced by vapor-depositing a hard coating layer, respectively.

  Moreover, for the purpose of comparison, each of the above-mentioned superhard gear cutting bases A to F is also ultrasonically cleaned in acetone and dried, and the same conditions are applied to the arc ion plating apparatus shown in FIG. It is inserted and only the metal Ti for hard coating layer formation and bombard cleaning is mounted as a cathode electrode (evaporation source). Ti bombard cleaning of the surface of the cemented carbide cutting base is performed by the above-described coated carbide cutting of the present invention described above. The same conditions as those applied in the manufacture of the tools 1 to 6 are performed, and the (Ti, Al) N layer as the underlayer is not formed, but TiN having the target layer thickness shown in Table 3 is also used under the same conditions. Conventionally coated cemented carbide cutting tools 1 to 6 were manufactured by vapor-depositing a hard coating layer composed of layers.

Next, using the above coated carbide cutting tool 1-6 of the present invention and the conventional coated carbide cutting tool 1-6, the material is made of low alloy steel of JIS / SCr420H, module: 2.0, pressure Machining of gears with dimensions and shapes of angle: 20 degrees, number of teeth: 29, twist angle: 25 degrees left twist, tooth length: 4.7 mm, tooth width: 20.0 mm,
Cutting speed (rotational speed): 500 m / min,
Feed: 1.2 mm / rev. ,
Processing form: climb, no shift, dry (air blow),
The high-speed gear cutting conditions (normal cutting speed was 350 m / min.) Were performed, and the number of gears processed until the flank wear width reached 0.1 mm was measured. The measurement results are shown in Tables 2 and 3, respectively.

When the composition of the foundation layer which comprises this invention coated cemented carbide cutting tool 1-6 obtained as a result of this was measured using the Auger spectroscopic analyzer, each showed the composition substantially the same as a target composition.
Moreover, the thickness of the hard coating layer and the ground layer of these coated carbide cutting tools 1 to 6 of the present invention, and the thickness of the hard coating layer of conventional coated carbide cutting tools 1 to 6 are respectively measured using a scanning electron microscope. As a result of cross-sectional measurement, all showed an average layer thickness (average value of five measurements) substantially the same as the target layer thickness.

  In the above-described coated carbide cutting tool according to the present invention, the service life is determined by the wear of the TiN layer, which is the hard coating layer of the tooth flank. The (Ti, Al) N layer is left and the tooth rake face remaining after use, or the front and rear surfaces including the tooth rake face, and the TiN layer on the flank face are removed by grinding and reused in this state. Therefore, the TiN layer may be formed by vapor deposition, so that it can be reused repeatedly.

From the results shown in Tables 2 and 3, the coated carbide cutting tools 1 to 6 of the present invention in which a (Ti, Al) N layer is interposed as an underlayer of a TiN layer that is a hard coating layer only on the flank face of the tooth portion. In both cases, even when gear cutting of a steel gear is performed under high-speed conditions accompanied by high heat generation, the temperature of the tooth portion is prevented from being increased by the action of the base layer, and the tooth portion is thermoplastically deformed. The tooth portion always takes a normal wear form, and as a result, it exhibits excellent wear resistance over a long period of time, whereas there is no formation of the base layer that exhibits excellent heat insulation. In conventional coated carbide gear cutting tools 1-6, high heat generated during high-speed gear cutting is transmitted to the tooth part, and as a result, the tooth part undergoes thermoplastic deformation and uneven wear occurs, so wear progresses rapidly. It is clear that the service life is reached in a relatively short time.
As described above, the coated carbide gear cutting tool of the present invention performs not only gear cutting under normal conditions, but also gear cutting of various steel gears, etc., under high speed conditions accompanied by high heat generation. In this case, since the thermoplastic deformation of the tooth portion is prevented and excellent wear resistance is exhibited over a long period of time, it is possible to satisfactorily cope with labor saving and energy saving of gear cutting and further cost reduction. Is.

The arc ion plating apparatus used for manufacturing a coated carbide gear cutting tool is shown, (a) is a schematic plan view, and (b) is a schematic front view.

It is a schematic perspective view of a coated carbide gear cutting tool.

Claims (1)

A plurality of tooth spaces are formed radially along the length direction with respect to the rotation axis, and face the tooth spaces between each tooth space, and the front and rear surfaces are rake faces with respect to the rotation direction. And a tungsten carbide base having a shape in which a plurality of tooth portions composed of a top surface (tooth tip surface) and both side surfaces (left and right tooth surfaces) serving as flank surfaces are continuously formed along the length direction. In the surface cutting cemented carbide cutting tool made by physical vapor deposition of a hard coating layer made of a titanium nitride layer with an average layer thickness of 0.9 to 15 μm on the surface of the hard alloy cutting tool body,
The top surface (tooth tip tooth surface) and both side surfaces (left and right tooth surfaces) constituting the flank of the tooth part have an average layer thickness of 0.1 to 5 μm as an underlayer of the hard coating layer, and And a physical insulating layer composed of a composite nitride layer of Ti and Al satisfying the composition formula: (Ti _1-X Al _X ) N (wherein X is 0.40 to 0.65 in atomic ratio). A surface-coated cemented carbide strip cutting tool that exhibits excellent wear resistance in high-speed gear cutting.

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