JP2002273614A - Diamond coating end mill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a diamond coating end mill capable of cutting even a material difficult to cut such as a high silicon aluminium alloy without damaging a edge part. SOLUTION: A rake face of the edge part is not less than -10 deg. and not more than -60 deg. at a rake angle E and rake face length F is characteristically at least 0.2 mm on the end mill for high silicon aluminium alloy cutting furnished with the edge part forming a diamond coating layer 2 on a base material surface. Cemented carbide a crystal grain diameter of a WC layer of which is not more than 4 μm, breaking resistanct force strength of which is not less than 100 kg/mm<2> and a thermal expansion coefficient of which is not more than 5.0×10<-6> deg.C is used for the base material, and it is favourable to have small cracks on the crystal grains of the WC layer. It is favourable that the diamond layer is fomed not more than 20 μm in thickness by a diamond of not more than 10 μm in average grain diameter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tool used for cutting nonferrous metal materials, electronic materials, and the like, and more particularly to an end mill having a blade portion coated with diamond by a vapor phase synthesis method.

[0002]

2. Description of the Related Art The demand for processing difficult-to-cut materials such as high silicon aluminum alloys with high precision and high efficiency has increased.
High-speed end mills and cemented carbide end mills with high high-temperature hardness, excellent wear resistance and rigidity have begun to be used more and more. An improved product in which a cemented carbide end mill is coated with TiN is also known. It has higher abrasion resistance and less welding of cuttings to the cutting edge, so it can be cut even with hard-to-cut materials such as stainless steel. Not usually, 200m /
It is cut at a cutting speed of about min or less.

A polycrystalline diamond material is known as a blade material having a higher hardness. This is highly accurate and can withstand continuous cutting, and exhibits excellent performance. However, it is difficult to apply to a complicated spiral-shaped drill and end mill, and there is a disadvantage that chipping easily occurs in the cutting edge in intermittent cutting.

[0004]

As a supplement to the disadvantages and costs of the above-mentioned polycrystalline diamond sintered body, there is known a diamond-coated cutting tool in which the surface of a substrate is coated with diamond by a vapor phase synthesis method.

[0005] One example is JP-A-64-51202. According to this proposal, the defect of diamond layer loss due to stress concentration at the cutting edge due to the positive brake at the cutting edge of the cutting tool has a dimension of 0.3 mm from the flank of the cutting edge.
Honing or chamfer honing is applied to a portion of not less than 01 mm and not more than 0.08 mm to solve the problem.

Although this proposal is excellent, it is not always satisfactory under more severe cutting conditions. Particularly in the end mill described above, at least 200 m / m
in or more, preferably exceeding 1000 m / min and 200
When cutting at a high speed of about 0 m / min or more,
With this honing or chamfer honing, it is not possible to sufficiently prevent the diamond coating layer from being damaged, and cutting by an end mill or a drill in a high-speed region exceeding this cannot be practically used.

[0007]

A first feature of the present invention is that a positive brake, which has been used as a common sense in a conventional diamond-coated rotary cutting tool, has been modified to provide an end mill for cutting high silicon aluminum alloy. To use as a negative brake,
The rake face has a rake angle of -10 ° to -60 °, and the rake face length is at least 0.2 mm or more. The rake face length is determined to be preferably 0.2 mm or more in view of the usual maximum cutting depth in the end milling of a difficult-to-cut material for forming a negative rake angle as described above.

The second characteristic is that the WC layer has a crystal grain size of 4 μm or less, a transverse rupture strength of 100 kg / mm ² or more, and a thermal expansion coefficient of 5.
That is, a cemented carbide of 0 × 10 ⁻⁶ / ° C. or less was used.

A third feature is that crystal grains of the WC layer of the base material have minute cracks.

A fourth feature is that the diamond coating layer is firmly bonded to a thickness of 20 μm or less with diamond having an average particle size of 10 μm or less.

The fifth feature is that the surface of the base material has an Rmax of 1 μm.
m or less, and the diamond layer is formed of diamond having an average particle diameter of 3 μm or less to a thickness of 5 μm or less.

A sixth feature is that the rake face length is specified to be at least one time, preferably at least two times the cut depth.

In order to form the diamond coating layer, it is preferable that the cemented carbide substrate is previously heat-treated at about 900 ° C. for about one hour in a reducing atmosphere containing a carbon element.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention will be described in the section of Examples. (Embodiment 1) FIGS. 1 (a), 1 (b) and 1 (c) are front views, side views and an enlarged detailed view of a portion D of an embodiment of an end mill in which the whole tool is made of an integral cemented carbide 1. FIG. The tool length A is 85 mm, the blade diameter B is 30 mm, and the blade length C of 6 blades is 4
3 mm.

As the cemented carbide 1, WC-6% Co is used.
The crystal grain size of the WC layer is 2 μm or less and the transverse rupture strength is 150
kg / mm ² or more, coefficient of thermal expansion 5.0 × 10 ⁻⁶ / ° C
The following were used. The entire surface of the portion of the blade length C is covered with a thin film of the diamond coating layer 2 as shown by hatching by the following method. This thin film is the cutting edge part 3.
Although it may be provided only on the (cutting edge), it is often advantageous to provide the entire blade length C in terms of production and use, and therefore, the embodiment is based on that.

The substrate of the cemented carbide 1 was machined to produce an end mill substrate without the diamond layer 2 in FIG. In this production, a large number of trial production examples having different rake angles E shown in Table 1 were produced, and thereafter, heat treatment, diamond coating and cutting tests were also performed on all of the majority. Example 1 has a rake angle of -30 ° in Table 1. The rake face length F was 0.4 mm.

[0017]

[Table 1]

The above-mentioned end mill substrate is heated with a hot filament CV.
D device₂-1% CH ₄Substrate temperature in the atmosphere
The temperature was maintained at about 900 ° C. for 1 hour to perform a heat treatment. Heat treatment
Precipitates on the surface of the substrate, especially on the surface on which the cutting edge is formed
Scrub the soot and soot or remove the atmosphere inside the CVD equipment.
H₂And remove by heating.

On the surface of the substrate subjected to the above treatment, the amount of the bonding metal is reduced, the interval between the hard phase particles is small, and fine cracks are formed. The adhesive strength with the adhesive is extremely strong. In addition, prior to diamond coating, seeding of ultrafine diamond on the surface of the substrate, or, if the surface of the substrate is less than about Rmax1μm,
Since this tendency is stronger, the average diamond particle size is 3
This method is preferable for applying a fine, thin diamond coat having a thickness of 5 μm or less and a thickness of 5 μm or less.

In the diamond coating, the end mill substrate treated as described above is inserted into the hot filament CVD apparatus so as to stand upright with the cutting edge side up, and the diamond coating layer is formed over the entire length of the cutting edge under the following conditions. Was formed.

[0021]

The thickness of the formed diamond coating layer was about 10 μm, and the adhesion to the end mill substrate surface was strong. A trial production using seeds of the ultrafine diamond was also performed. In this case, since the film formation time was reduced to 5 hours, the diamond crystal grains were 1 μm.
The growth was suppressed to about m and the growth was suppressed to about 5 μm, and a uniform diamond coating layer having a thickness of 5 μm was obtained. As a result, it was confirmed that the average diameter of the diamond crystal could be reduced to 3 μm or less and the thickness of the diamond coating layer could be uniformly reduced to 5 μm or less, if necessary.

The cutting test was performed on the diamond coating layer having a thickness of about 10 μm under the following conditions. The results are shown in Table 1. As for the positive rake angles of 10 ° and 0 °, those having been subjected to a rounding treatment of about 5 μm in advance to prevent chipping and chipping of the cutting edge were used.

[0024]

As can be understood from Table 1, even with a negative rake angle, at this cutting speed, the cutting force hardly increased, and in particular, -20 ° to -4 °.
In the case of 0 °, the value is reduced. And the surface roughness of the machined surface is also excellent. The chipping of the cutting edge of the positive one is lower than that of the negative one because the edge strength is low.
The chipping at 60 ° and −70 ° seems to be caused by the increase in cutting force. The number of chips in Table 1 is 10
The number of occurrences of chipping of the cutting edge during the 00m cutting process is shown.

In the above description, the edge portion 3 has a WC layer having a crystal grain size of 4 μm or less and a transverse rupture strength of 100 kg / m 2.
m ² or more, since it is intended to thermal expansion coefficient is formed by providing a diamond coating layer 2 to 5.0 × 10 -6 ^/ ℃ or less of the cemented carbide 1 surface, in what rake angle is negative is , Without having to make the cutting edge round,
It is considered that the strength of the cemented carbide 1 was maintained as it was to the cutting edge, and chipping of the cutting edge due to chipping or the like was prevented.

Furthermore, the diamond coating layer 2 is uniform without providing a rounded edge, and the end mill edge shape manufactured by machining the base material of the cemented carbide 1 is accurately maintained, and is shown in Examples. The effect is greater in the region of the minute cut as shown in FIG. Therefore, it is considered that the cutting resistance did not increase unexpectedly and the roughness of the machined surface was improved. In general, it is said that the thicker the coating layer, the better the adhesion to the substrate, but if it is thicker, diamond grains grow and the uniformity of the coating surface,
Since the surface roughness is reduced, it is preferable to reduce the thickness as long as the wear resistance can be maintained.

Cut amount (Rd = radial depth)
Is smaller than the length of the negative rake face, cutting always starts between the line segments GH on the rake face and ends at the point G. It is also conceivable that this may have an effect different from that of the conventional positive brake even in chip discharge.

(Example 2) Example 2 (rake angle was -30 °) and Comparative Example 2 (rake), except that the blade diameter B was changed to 32 mm, were used. Corner 10
°) created. This is set at 20,000 rpm
FIG. 2 shows the results of tests performed under the same conditions as the cutting test conditions described in the section of Example 1 except that the m and the cutting speed were set to 2010 m / min.

As can be understood from FIG. 2, the working example 2 has a Rmax of 0.75 μm
Improved and 4N lower in back force.

(Embodiment 3) An embodiment 3 (rake angle-) similar to that described in the embodiment 1 except that the tool length A was 175 mm, the blade diameter B was 40 mm, and the blade length C was 60 mm.
30 °) and Comparative Example 3, and a cutting test was performed under the following conditions.

[0032]

The results of the cutting test are shown in FIG. 3, and Example 3 is different from Comparative Example 3 in terms of Rmax in machining surface roughness.
It improves by 0.4 μm and the back force is reduced by 4N.

Although the above embodiments are all based on the end mill, the same effect can be expected in a drill having an outer peripheral edge and a tip end similarly to the end mill.

[0035]

As described in the above, according to the present invention, it is possible to provide an end mill capable of performing cutting with improved cutting surface roughness without increasing cutting resistance. In addition, by using the above-mentioned tool, it is possible to cut a difficult-to-cut material such as a high silicon aluminum alloy at a high speed of at least 200 m / min or more, and if necessary, at least 2000 m / min, which has been conventionally difficult in practice. Made it possible.

[Brief description of the drawings]

FIGS. 1 (a), 1 (b) and 1 (c) are an enlarged detail view of a part D in a front view, a side view and a front view of an end mill according to an embodiment.

FIG. 2 is a chart showing cutting test results of Example 2.

FIG. 3 is a table showing cutting test results of Example 3.

[Explanation of symbols]

 1 Integrated cemented carbide 2 Diamond coating layer 3 Edge part A Tool length B Edge diameter C Edge length D Enlarged area E Rake angle F Rake surface length G Rake surface outer peripheral end H Rake surface axial center end

Claims (6)

[Claims] 1. A rake face having a diamond coating layer formed on a surface of a base material, the rake face of the rake face has a rake angle of −10 ° to −60 ° and a rake face length of at least 0.1 mm. A diamond-coated end mill for cutting high silicon aluminum alloys having a diameter of 2 mm or more. 2. A WC layer having a crystal grain size of 4 μm as a base material.
The diamond coated end mill according to claim 1, wherein a hard metal having a transverse rupture strength of 100 kg / mm ² or more and a thermal expansion coefficient of 5.0 ^10-6 ° C or less is used. 3. The diamond coating end mill according to claim 1, wherein crystal grains of the WC layer of the base material have minute cracks. 4. The diamond coating end mill according to claim 1, wherein the diamond layer is formed of diamond having an average particle diameter of 10 μm or less to a thickness of 20 μm or less. 5. The method according to claim 1, wherein the surface of the substrate has a Rmax of 1 μm or less, and the diamond layer is formed of diamond having an average particle diameter of 3 μm or less to a thickness of 5 μm or less. The described diamond coated end mill. 6. The diamond-coated end mill according to claim 1, wherein the rake face length is at least one time the depth of cut.