JPH11207516A - Tip for throwaway ball end mill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prolong the service life of a tool by increasing wear resistance in the vicinity of the rotational center of a super hard alloy as a base body for a throwaway tip used for a ball end mill and the plastic deformation resistance of an outer peripheral part. SOLUTION: In a throwaway tip used for a throwaway ball end mill coated with hard film, a Co content in a super hard alloy is >=3 wt. % and <=10 wt.%, a WC average particle size is >=0.3 micron and <=1.2 micron, and a Co grating constant is >=3.565 Å and <=3.575 Å.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention exhibits excellent wear resistance in cutting at extremely high cutting temperatures, such as dry cutting, high-hardness steel cutting, and high-speed, high-precision cutting that does not require a polishing step after cutting. For a throw-away type ball end mill.

[0002]

2. Description of the Related Art In a throw-away type ball end mill, when used as a tool, the cutting speed is low near the center of rotation, and the cutting speed is high near the outer peripheral blade. However, when the blade diameter is small, it is made of one chip material. In this case, the material adapted to the low-speed portion has insufficient performance of the outer peripheral portion, and the material adapted to the outer peripheral portion is not satisfactory, such as causing a problem in chipping resistance at the low-speed portion. . This tendency has become a bigger problem as indexable ball end mills are applied to smaller diameters. For example, Japanese Patent Application Laid-Open No. 9-262714 discloses an example of a composite material of a ceramic and a hard metal.

[0003]

As described above, in the throw-away type ball end mill, the cutting temperature of the cutting edge on the outer peripheral portion is significantly higher than that in the low speed range, and micro plastic deformation occurs on the cutting edge. Wear is repeated by repeatedly inducing wear, leading to the tool life. Further, rubbing wear is mainly in the vicinity of the center of rotation, and peeling or falling off of the film occurs due to welding or the like, or wear progresses due to chipping or the like, leading to a tool life. Therefore, the indexable tip is 1
When it is formed of two materials, it is necessary to have both of these characteristics, and to combine a film according to the characteristics. First, using a fine-grained cemented carbide for the cemented carbide as the base and improving its plastic deformation resistance leads to achieving a satisfactory tool life in the outer peripheral part where the cutting edge becomes hot, In the vicinity of the center of rotation, the features that the fine-grain cemented carbide has high toughness and excellent chipping resistance can be utilized.

[0004]

Generally, a relatively large amount of Co is added to an ultrafine-grained cemented carbide in order to maintain chipping resistance. Usually, the Co content is about 10 to 14% by weight. As the amount of Co increases, the plastic deformation resistance naturally deteriorates. Therefore, in order to improve the plastic deformation resistance, naturally C
It is essential to reduce the o content. However, if the Co content is simply reduced, the chipping resistance is inevitably deteriorated. According to our research,
Co content is 10% by weight to improve plastic deformation resistance
The following is preferable. In this case, by adjusting the carbon content of the alloy to a lower side, deterioration of chipping resistance could be prevented. That is, the lattice constant of Co is 3.575 on the low carbon side just before the decarburized phase appears in the production of cemented carbide.
Å, 3.5 on the high carbon side just before free carbon appears
It changes continuously to 55 °, but it is 3.565
By controlling to the low carbon side where the temperature is within 3.575 °, deterioration of chipping resistance can be prevented.

[0005]

[Action] The reason is that cemented carbide is generally 1350 ° C to 14 ° C.
1250 ° C to 1330 ° C after 50 ° C liquid phase sintering step
In the cooling step until solidification of W, C and W, which were dissolved in the liquid phase, grow on the surface of the existing WC particles while crystallizing to form plate-like WC particles. Solidification temperature of 1 on low carbon side
As high as 330 ° C., the crystallization amount of WC is small and coalescence of WC particles due to grain growth hardly occurs, and the shape of the particles is relatively round. On the other hand, on the high carbon side, a relatively large amount of WC becomes crystallized and becomes angular particles during the cooling step, and the particles tend to unite during the grain growth. When the angular particles are united, stress is concentrated on the united portion due to the notch effect, cracks are generated, and chipping is easily induced as a result.

[0006] Further, by controlling to a low carbon side, Co
As is apparent from the increase in the lattice constant, the phase dissolves a large amount of W as compared with the high carbon side. As a result, the solid solution is strengthened and the Co phase itself is hardly plastically deformed. It is extremely effective in improving the tool life and gives a favorable result. Therefore, it is possible to cover with a single throw-away chip from a low-speed range to a high-speed range by using an ultrafine-grained cemented carbide that has reduced Co without deteriorating chipping resistance and has improved plastic deformation resistance at the same time. . further,
When providing a film on these, the film quality may be different at the outer peripheral portion and near the center of rotation, but according to the characteristics, the outer layer of the hard film is a film containing Al. As the inner layer, a film having high hardness provided with abrasion resistance near the rotation center or a film having a small coefficient of friction and low affinity for steel is suitable. As the former, a film exceeding HV3000 such as TiC or TiCN is optimal. The outer layer must have oxidation resistance particularly at the outer peripheral portion, but a film having excellent wear resistance is essential near the center of rotation. for that reason,
TiAl compound film as the outer layer, and further, Si, Y
By adding such a third component, it is possible to improve the oxidation resistance of the film and further improve the cutting characteristics. These third components segregate at the crystal grain boundaries of the TiAl-based coating and suppress the diffusion of oxygen at the grain boundaries, thereby improving the oxidation resistance of the coating. Si, Cr, Zr, Hf, Y, Nb, and Nd were confirmed as components having such an effect. Further, the thickness of the inner layer-the outer layer may be changed.
In particular, although it depends on the adhesiveness, it is possible to obtain a well-balanced film by making the film thick near the rotation center and thin near the outer periphery.

Next, the reason for limiting the numerical values will be described. Co
If the content is less than 3% by weight, the fracture toughness value of the cemented carbide is low and chipping is liable to occur. If the content exceeds 10% by weight, the plastic deformation resistance is deteriorated, so that the content is 3% by weight or more. % By weight or less. The WC average particle size is 0.1.
If it is less than 3 microns, the hardness of the cemented carbide becomes extremely high and the toughness deteriorates. If it exceeds 1.2 microns, the wear resistance deteriorates. The lattice constant of Co is 3.565 ° as described above.
On the high carbon side of less than 3.565% or more, the chipping resistance deteriorates and the solid solution strengthening of Co itself is insufficient, and if it exceeds 3.575 °, a fragile decarburized phase appears.
3.575 ° or less. Hereinafter, the present invention will be described in detail based on examples.

[0008]

EXAMPLE A commercially available WC powder having an average particle size of 0.2 to 1.5 microns and a Co powder of the same 1 micron were mixed in an alcohol for 6 hours using an attritor. A chip having a side of was manufactured. These chips were converted from TiN and TiCN to T
Using an i (50) Al (50) target by an arc ion plating method, a bias voltage of 70 V, a pressure of 4 × 10 ⁻² mbar, and a coating film thickness of 0.2-1.0.
-1.0 micron, TiN under the condition of total 2.5 micron
-TiCN-TiAlN was coated to produce a chip of the present invention and a comparative chip shown in Table 1.

[0009]

[Table 1]

[0010] These throw-a-tips have a diameter of 12 m.
m with a ball end mill having a diameter of 100 mm and a depth of 5 mm under the following cutting conditions.
(Hardness HRC50). The processing was contour processing, and the amount of wear with respect to the number of processing pockets was measured.
Table 2 shows the results. Cutting conditions Rotation speed 10000 rpm (Cutting speed = 314 m / min) Table feed 2000 mm / min (0.1 mm / tooth) Cutting depth x Pitch 5 x 0.5 mm Cutting oil None Overhang 30 mm

[0011]

[Table 2]

In Table 2, the amount of wear was measured by the amount of retreat of the cutting edge at the tip of the ball end mill, and the amount of wear was measured by the maximum amount of flank wear near the outer periphery. The unit is mm. The life was defined as the number of drilled holes until the amount of retreat of the cutting edge was 0.03 or more or chipping occurred. As is clear from Table 2,
In the present invention example in which the carbon amount of the cemented carbide of the tip is controlled to the low carbon side, the amount of wear progression due to micro plastic deformation is small, stable cutting and finished surfaces are obtained, and in the low speed range, TiC is obtained.
The wear resistance and low coefficient of friction of the N layer are exhibited, and a high-quality cut surface is obtained. In addition, the result showed the same tendency also in the radius end mill with the corner R which can process similarly to a ball end mill.

The cemented carbide manufactured in the above example was coated with various ternary coatings shown in Table 3 by 1 μm instead of the TiAlN film, and the same evaluation was performed by the same cutting as in the example. The results are also shown in Table 3. The alloy numbers shown in Table 3 are those shown in Table 1.

[0014]

[Table 3]

As is apparent from Table 3, it is clear that the ball end mill using the ternary chip of the present invention exhibits more excellent performance. This is considered to be due to the improvement in wear resistance of the film itself accompanying the improvement in oxidation resistance as described above. When the substitution amount is less than 1%, the effect of addition is not recognized, and it is also confirmed that the result is almost the same as that of Example 1 of the invention. Further, when the addition amount exceeds 30%, the film becomes brittle and chipping occurs at the initial stage, the film hardness is deteriorated, and the result that the wear resistance is significantly impaired is also confirmed.

[0016]

As described above, the coated end mill according to the present invention significantly improves tool characteristics in dry cutting or the like in which the cutting edge is particularly high in temperature. Needless to say, the effect is the same not only in the ball end mill but also in a general end mill.

Claims (2)

[Claims] 1. In a tip of a throw-away type ball end mill coated with a hard film, the Co content of a cemented carbide is in the range of 3 to 10% by weight, and the average particle size of WC is 0.3 μm or more. In the range of 2 microns or less,
A tip for a throw-away type ball end mill, comprising a cemented carbide having a lattice constant of Co of 3.565 to 3.575 °. 2. The tip for a throw-away type ball end mill according to claim 1, wherein the outer layer of the hard film is made of A.
1. A tip for a throw-away type ball end mill, comprising a coating containing l.