JPH11300516A - Cemented carbide end mill with excellent wear resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an end mill which exhibits an excellent wear resistance over the long run and to elongate its service life without the occurrence of a defect in a peripheral cutting edge, by endowing the entire peripheral cutting edge with toughness as high as that of cemented carbide used for inside part. SOLUTION: An end mill is formed of cemented carbide which comprises 6-15% of Co as a binding phase forming component; 0.1-2% of V and/or Cr as another binding phase forming component; and the remainder substantially of WC (tungsten carbide) as a dispersion phase forming component, an average particle diameter of WC particles being 1 μm or less. In addition, in a relief surface of a cutting edge at a peripheral cutting edge, a hard diffused boric layer is formed in a depth of 0.3-5 μm from the relief surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cemented carbide end mill which significantly improves wear resistance without impairing the excellent toughness of cemented carbide, thereby extending service life. It is.

[0002]

2. Description of the Related Art Conventionally, an end mill is generally used as shown in FIG.
As shown in the schematic front view in FIG. 2 and the cutting edge in FIG. 2B as a schematic longitudinal sectional view, the cutting edge comprises a shank portion and a cutting edge portion formed with an outer peripheral edge, and the outer peripheral edge has a rake face and a flank face. It is also well known that this has a shape composed of a cemented carbide.

[0003]

On the other hand, in recent years, there has been a strong demand for labor saving and energy saving in cutting, and with this demand, end mills are required to have a longer service life. When made of cemented carbide,
Wear progress is suppressed, but insufficient toughness is inevitable,
As a result, chips such as chipping and chipping (small chipping) are likely to occur in the outer cutting edge of the cutting edge. On the other hand, if the cutting edge is made of a cemented carbide with high toughness for the purpose of suppressing chipping, the wear progresses quickly, and it is used in any case. At present, the life cannot be extended.

[0004]

Means for Solving the Problems Accordingly, the present inventors have
From the above-mentioned viewpoints, as a result of researching to develop a cemented carbide end mill in which wear progresses slowly, and in particular, hardly causes chipping on the outer peripheral edge of the cutting edge portion, the end mill was reduced by weight% (hereinafter simply referred to as % Indicates weight%), Co: 6 to 15% as a binder phase-forming component, and V as a binder phase-forming component.
And / or Cr: 0.1 to 2%, the balance being substantially composed of tungsten carbide (hereinafter referred to as WC) as a dispersed phase forming component, and the average particle diameter of WC grains Is made of a cemented carbide having a diameter of 1 μm or less,
The flank of the outer peripheral edge of the cutting edge portion is 0.3 to 5 from the surface.
When a diffusion boride layer in which boron (B) element is diffused is formed over a depth of μm, in the resulting end mill, excellent toughness is secured by the cemented carbide having the above composition and WC grain size. And, since the diffusion boride layer is extremely hard, this contributes to the improvement of wear resistance.However, since the hard diffusion boride layer is formed only on the flank of the outer peripheral edge, there is no decrease in toughness of the outer peripheral edge itself, Since the entire outer peripheral edge retains the high toughness equivalent to the high toughness of the cemented carbide inside, there is no occurrence of fracture in the outer peripheral edge, and it exhibits excellent wear resistance over a long period as an end mill. The research results show that the service life can be extended.

The present invention has been made based on the results of the above-mentioned research, wherein Co: 6 to
15%, also containing V and / or Cr: 0.1 to 2% as a binder phase-forming component, with the balance substantially consisting of WC as a dispersed phase-forming component, and the average grain size of WC grains It is made of cemented carbide having a diameter of 1 μm or less,
The flank of the outer peripheral edge of the cutting edge portion is 0.3 to 5 from the surface.
forming a hard diffusion boride layer over a depth of μm,
It is characterized by a cemented carbide end mill with excellent wear resistance.

Next, in the end mill of the present invention,
The reason for limiting the composition of the cemented carbide and the average particle size of the WC grains, and the depth of the hard diffusion boride layer as described above will be described. (A) Composition of cemented carbide (a) Co The Co component improves the sinterability and forms a binder phase to improve the toughness, and thus, combined with fine WC grains, causes a defect in the outer cutting edge of the cutting edge. Has the effect of suppressing the occurrence of
If the content is less than 6%, sufficient toughness required for an end mill cannot be secured. On the other hand, if the content exceeds 15%, the abrasion resistance rapidly decreases. Was determined to be 6 to 15%, preferably 8 to 13%. (B) V and Cr These components form a binder phase to form WC during sintering.
It has the effect of suppressing grain growth, but its content is 0.1
%, The average particle size of the WC powder as the raw material powder is 1 μm.
m or less, the particles grow during sintering and have an average particle size exceeding 1 μm, so that the desired toughness cannot be secured, and the outer peripheral edge of the cutting edge portion is broken, On the other hand, if the content exceeds 2%, the toughness of the binder phase itself decreases, which causes the occurrence of defects.
1-2%, desirably 0.5-1.5%.

(B) Average particle size of WC particles The average particle size of WC particles is as described above.
The average particle diameter and the V and Cr contents are adjusted depending on the powder. If the average particle diameter exceeds 1 μm, the toughness is significantly reduced due to the coarsening of the WC grains, and the outer edge of the cutting edge is liable to be chipped. Therefore, the average particle size was set to 1 μm or less.

(C) Depth of Hard Diffusion Boron Layer If the depth is less than 0.3 μm, the desired effect of improving wear resistance cannot be obtained, while if the depth exceeds 5 μm, the toughness of the outer peripheral edge decreases. However, since chipping and chipping occur frequently, the depth is set to 0.3 to 5 μm, preferably 0.1 to 5 μm.
It was determined to be 5 to 3 μm.

The hard diffusion boride layer in the end mill according to the present invention is formed by suspending, for example, fine powder of aluminum oxide (hereinafter referred to as Al ₂ O ₃ ) on the surface other than the flank of the peripheral edge of the end mill. Using an alcohol solution, perform masking and charge it into a boring furnace,
For example, a mixed gas obtained by mixing boron chloride with hydrogen at a ratio of 1 to 5% by volume is introduced into the furnace, and the atmospheric pressure in the furnace is set to 2
A boring process is performed at a temperature of 650 to 900 [deg.] C. for 5 to 30 minutes under a condition of 10 to 10 Torr to form a predetermined depth on the flank of the outer peripheral blade which is not masked. Can be.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a cemented carbide end mill according to the present invention will be specifically described with reference to examples. As raw material powders, WC powder having an average particle diameter of 0.8 μm, VC powder of 1.5 μm, Cr ₃ C ₂ powder of 2.3 μm, and Co powder of 1.2 μm were prepared. Are mixed in a predetermined ratio, mixed in a wet ball mill for 72 hours, dried under reduced pressure, and then at a pressure of 1 ton / cm ² , having a predetermined diameter in the range of 7 to 30 mm, and 5
It is press-molded into long shaped bodies having a predetermined length in the range of 0 to 135 mm, and these long shaped bodies are placed in a vacuum,
Sintering is performed at a predetermined temperature in the range of 1380 to 1480 ° C. for 1 hour to obtain a binder phase forming component content shown in Table 1, and substantially the remaining WC grains are also shown in Table 1. A long-sintered sintered material having an average particle size, and a four-blade having the outer diameter and length shown in Table 1 by grinding from the long-sintered material and having a shape shown in FIG. End mill bodies A to H are formed, and these end mill bodies A to H
After applying an alcohol solution of an Al ₂ O ₃ powder having an average particle diameter of 1.0 μm to all surfaces except the flank of the outer peripheral edge of the cutting edge portion, the surface is masked by applying 5 To.
rr in a mixed gas of H ₂ + 3% by volume BCl ₃ , temperature: 7
Boriding treatment is performed at 50 ° C. for a predetermined time within a range of 5 to 30 minutes to diffuse boron (B) element into the flank of the outer peripheral edge. The end mills 1 to 8 of the present invention were manufactured by forming a diffusion boride layer and finally removing the masking.

The resulting end mills 1 to 5 of the present invention
8, and for the purpose of comparison, the above-mentioned end mill bodies A to H were used as comparative end mills 1 to 8, respectively. (A) Work material: S50C (hardness: HB 240), Cutting speed: 60 m / min, Feed: 0 0.015 mm / rev, axial cut: 4.5 mm, radial cut: 0.3 mm, (b) work material: S50C (hardness: HB 240), cutting speed: 60 m / min, feed: 0.025 mm / rev, axial cut: 7.5 mm, radial cut: 0.5 mm, (c) work material: S50C (hardness: HB 240), cutting speed: 60 m / min, feed: 0.04 mm / rev, shaft Cut in direction: 12 mm, Cut in radial direction: 0.8 mm, (d) Work material: S50C (hardness: HB240), Cutting speed: 60 m / min, Feed: 0.05 mm / rev, Directional cut: 15 mm, radial cut: 1 mm, (e) Work material: S50C (hardness: HB240), cutting speed: 60 m / min, feed: 0.1 mm / rev, axial cut: 24 mm, radial Cutting depth: 1.6 mm, (f) Work material: S50C (hardness: HB 240), Cutting speed: 60 m / min, Feeding: 0.16 mm / rev, Axial cutting: 37,5 mm, Radial cutting: 2 0.5 mm, any one of the above conditions (a) to (f) (Table 3
), A wet cutting test of carbon steel was performed, and the cutting length until the flank wear width reached 0.3 mm was measured. Table 3 shows the results of these measurements.

[0012]

[Table 1]

[0013]

[Table 2]

[0014]

[Table 3]

[0015]

From the results shown in Table 3, all of the end mills 1 to 8 of the present invention have the hard diffusion boride layer formed only on the flank of the outer peripheral edge, and the hard diffusion boride layer has the toughness of the outer peripheral edge. It is evident that the outer edge does not suffer from chipping, chipping, etc., and exhibits a much higher abrasion resistance than the comparative end mills 1 to 8 which do not have the same. As described above, the end mill according to the present invention exhibits excellent wear resistance over a long period of time without chipping or chipping of the outer peripheral edge, and can extend the service life.

[Brief description of the drawings]

FIG. 1 is a schematic front view of an end mill (a) and a schematic longitudinal sectional view of the cutting blade portion (b).

Claims (1)

[Claims] 1% by weight, Co: 6 to 15% as a binder phase-forming component, and V and / or Cr:
0.1 to 2%, the balance being substantially composed of tungsten carbide as a dispersed phase forming component, and comprising a cemented carbide having an average particle size of tungsten carbide particles of 1 μm or less. At the same time, on the flank of the outer peripheral edge of the cutting edge, 0.3 to 5
An end mill made of a hard metal having excellent wear resistance, wherein a hard diffusion boride layer is formed over a depth of μm.