JP3249493B2 - Cutting tools - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cutting tool such as a hob and an end mill using a high-speed tool steel containing hard MC type carbide for a cutting edge.

[0002]

2. Description of the Related Art High-speed tool steels and cemented carbides are generally used as cutting tool materials such as hobbs and end mills. As high-speed tool steel for cutting tools, those containing V in an amount of 2% or more have been developed in order to impart high hardness, wear resistance and heat resistance. On the other hand, cemented carbide is very hard but brittle, so it has very good wear resistance and heat resistance compared to high speed tool steel, but has poor grindability and impact resistance. Since the processing cost is high, the actual range of use is limited in terms of quality reliability and economy. Therefore, most of the hobbs that perform intermittent cutting are made of high-speed tool steel, and only some of them are made of cemented carbide.

[0003]

For such cutting tools, high-speed tool steels usually contain 2% or more of V in order to enrich hard MC-type carbides mainly containing V.
However, when the V content is 3% or more, this MC type carbide is more likely to be coarsened and elongated square as the V content is larger in the conventional ingot-melted high-speed tool steel, and not only is the grindability deteriorated,
There has been a problem that the toughness is reduced and chipping and breakage of the cutting edge portion, which originates from MC type carbide, is likely to occur.

[0004] Further, in the powdered high-speed tool steel, there is a problem that the MC type carbide is too fine, wear resistance is insufficient, large wear of the cutting edge is liable to occur, and the tool life is short for the expensive material. there were.

In the case of a hob for wet processing, the entire cutting edge is initially coated with a titanium-based or titanium-alloy-based ceramic coating by PVD, but after re-grinding, the coating on the rake face is completely removed. Therefore, the high-speed tool steel itself is required to have heat resistance and wear resistance.

Further, in the hob for dry machining which does not require cutting oil, in order to prevent abrasion, chipping and breakage, a material which is hard, tough enough to withstand the impact of intermittent cutting, and excellent in heat resistance, and There is a need for a coating film having excellent heat resistance, heat resistance, oxidation resistance, and lubricity, and a material having good compatibility with the coating film is required.

SUMMARY OF THE INVENTION In view of the above problems, the object of the present invention is not limited to a wet type and a dry type, but also a cutting tool using a material with less wear of the cutting edge and less chipping, and further, has excellent heat resistance and good compatibility with a coating film. An object of the present invention is to provide a cutting tool using a material.

[0008]

The present inventors have conducted experiments on solid hobs and end mills using various high-speed tool steels. As a result, the grindability, toughness, chipping resistance, and chipping resistance of the cutting edge are improved. In order to obtain a cutting tool that also has wear properties, the area ratio of hard MC type carbide is limited to an appropriate range,
In addition, it has been found that it is important to limit the ratio of the major axis to the minor axis to a value as large as possible so that the shape of the MC type carbide approaches a spherical shape. That is, V is 2-4% and Co is 7-1.
0% or the maximum equivalent circular diameter of MC type carbide in high speed tool steel containing 4 to 6% V and 4 to 9% Co is 5 to 14%.
MC having an equivalent circular diameter of 5 to 14 μm
Area ratio of cross section parallel to forging and rolling axis of die carbide is 3
-8%, and the ratio of the major axis to the minor axis of the MC type carbide is 0.1%.
I learned that it is necessary to make it 3 or more. Also,
It has been found that this cutting tool steel has good compatibility with the composite film of the titanium-alloy-based ceramic coating by PVD, and exhibits more excellent performance in dry processing than in wet processing. The equivalent circular diameter of the MC type carbide refers to the diameter of the circle when the area of the cross section of the particle of the MC type carbide is replaced by the area of the circle. The maximum equivalent circular diameter of the MC type carbide refers to the equivalent circular diameter of the largest carbide among the MC type carbides.

[0009] Based on this knowledge, in the first invention of the present invention, in a cutting tool having a cutting edge made of high-speed tool steel, the high-speed tool steel is C: 0.6 to 1.8 by weight%.
%, Si: 1.2% or less, Mn: 0.5% or less, Cr: 3.5 to 5.0%, M
o: 10% or less, W: 21% or less, and by weight%
V: 2 to 4%, Co: 7 to 10%, with the balance being Fe and unavoidable impurities, the area of the cross section of the largest carbide grain among the MC type carbide grains in the cutting edge steel is defined as the area of a circle. The maximum equivalent circular diameter of the equivalent circular diameter, which is the diameter of the circle in the case of replacement, is the maximum equivalent circular diameter of 5 to 14 μm, and the equivalent circular diameter of the MC type carbide particles of 5 to 14 μm. The above problem has been solved by providing a cutting tool characterized in that the ratio of the major axis to the minor axis of the particle cross section is 0.3 or more.

[0010] In a cutting tool having a cutting edge made of high-speed tool steel, the high-speed tool steel has a weight percentage of C: 0.6.
~ 1.8%, Si: 1.2% or less, Mn: 0.5% or less, Cr: 3.5 ~ 5.0
%, Mo: 10% or less, W: 21% or less, and further weight%
V: 4 to 6%, Co: 4 to 9%, with the balance being Fe and unavoidable impurities, the area of the cross section of the largest carbide grain among MC type carbide grains in the steel at the cutting edge is defined as a circle. The MC type carbide having a maximum equivalent circular diameter of 5 to 14 μm, which is the largest equivalent circular diameter among equivalent circular diameters which are the diameters of circles when replaced as an area, and an equivalent circular diameter of 5 to 14 μm. The ratio of the major axis to the minor axis of the particle cross section of the grains, that is, the ratio obtained by dividing the minor axis of the particle section of any one of the MC-type carbide grains by the major axis,
It is good also as a cutting tool characterized by being 0.3 or more.

Preferably, M having an equivalent circular diameter of 5 to 14 μm
The cutting tool may be characterized in that the area ratio of the C-type carbide grains in the cross section of the grains parallel to the forging and rolling axes is 3 to 8%. In addition, forging of MC type carbide grains, the grain cross section parallel to the rolling axis is, for example, a grain cross section cut along the axial direction of the round steel or square steel, that is, the longitudinal direction of a round steel or a square steel of high-speed tool steel. It is. In an actual optical image measurement microscope, the area ratio is the sum of the area of the particle cross section of each MC type carbide particle having an equivalent circular diameter of 5 to 14 μm, which appears on the screen of the microscope, and the area of the screen itself. It will be divided. Furthermore, by applying one or more composite films of titanium-based or titanium-alloy-based ceramic coating by PVD to at least the cutting edge surface of the cutting tool, wear resistance and chipping resistance are further improved. Such cutting tools are also more suitable for dry machining.

More preferably, the high-speed tool steel comprises:
The electroslag remelting method prevents gas components including O ₂ and N ₂ from entering the molten steel due to an inert atmosphere, and dissolution conditions: dissolution rate: 400 to 800 kg / h, and the outer diameter of the steel ingot is set outside the electrode. The ratio divided by the diameter is kept at 1.2 to 1.7, and the MC
It is manufactured by controlling the size of the type carbide grains.

(Action) The maximum equivalent circular diameter of the MC type carbide in the high-speed tool steel at the cutting edge of the cutting tool of the present invention, the area ratio and the major axis of the MC type carbide in a cross section parallel to the forging and rolling axes are described below. The reason for limiting the minor axis ratio to the above will be described.
In cutting tools using powdered high-speed tool steel with a maximum equivalent circular diameter of MC type carbide in the cutting edge steel of less than 5 μm, the MC type carbide is easily removed together with the base material by cohesive wear or oxidative wear. Short tool life.

On the other hand, when the maximum equivalent circular diameter of the MC type carbide in the cutting edge steel exceeds 14 μm, and the area ratio of the MC type carbide having the equivalent circular diameter of 5 to 14 μm in the cutting edge steel exceeds 8%. , And become very brittle, and easily cause chipping with the MC type carbide as a fracture starting point. In particular, when the MC type carbide has a coarse and long rectangular shape with a ratio of major axis to minor axis of less than 0.3, it is difficult to grind and chipping is more likely to occur, causing tool breakage. On the other hand, when the area ratio of the MC type carbide is less than 3%, the wear becomes extremely easy, and the tool life is shortened. Therefore, M in the steel at the cutting edge
The maximum equivalent circular diameter of the C-type carbide is set to 5 to 14 μm, and the area ratio of the MC type carbide having an equivalent circular diameter of 5 to 14 μm in a cross section parallel to the forging and rolling axis is limited to 3 to 8%, and the long diameter is set. The minor axis ratio was limited to 0.3 or more. This effect can be similarly obtained for all high-speed tool steels, regardless of whether they are smelted high-speed tool steel or powdered high-speed tool steel.

The reason that the Co weight ratio is limited to 4 to 10% is that the more Co is, the more the heat resistance of the steel is improved, and at least 4% of Co is required to have heat resistance as a cutting tool material. However, if it exceeds 10%, the toughness is reduced, and tool breakage such as chipping and cracking is likely to occur. When V is 2 to 4%, the effect on toughness is small.
The weight ratio was limited to 7-10%. Further, since the toughness decreases when V is 4 to 6%, the Co weight ratio is limited to 4 to 9%. C forms MC type carbides and improves abrasion resistance.
However, if the amount of C is too large, the toughness decreases. Therefore, the weight ratio of C is limited to 0.6 to 1.8%. Si and M
n is added as a deoxidizing agent, but if the amounts of Si and Mn are too large, the toughness decreases. Therefore, the weight ratio of Si and Mn was limited to Si: 1.2% or less and Mn: 0.5% or less. C
r is added at 3.5 to 5.0% to enhance hardenability.
If the Cr content is less than 3.5%, the above effect is not obtained, and if it exceeds 5.0%, the overall toughness is reduced. Mo: 10% or less, W
Although not more than 21%, Mo and W form M ₆ C-type carbides and improve wear resistance. However, if the amounts of Mo and W are too large, the toughness is reduced.

[0016]

Next, an embodiment of the present invention will be described. Table 1
Is the chemical composition of solid hob, roughing end mill, and MC manufactured from inventive steels 7 to 10 and comparative steels 1 to 6.
Equivalent circular diameter (μm), equivalent circular diameter of 5-type carbide
It shows an area ratio of 14 μm (area ratio% in a cross section parallel to the forging and rolling axes) and a minimum major axis to minor axis ratio of MC type carbide having an equivalent circular diameter of 5 to 14 μm. In an actual optical image measurement microscope, the maximum equivalent circular diameter (μm), the area ratio, and the minimum major axis / minor axis ratio of the MC type carbide were measured with a microscope image. Further, the high-speed tool steel of the present invention can be prepared by using an electro-slag remelting method in the presence of O ₂ and N _{2 in} an inert atmosphere.
To prevent the intrusion of gas components containing molten steel into the molten steel, and dissolution conditions: the dissolution rate: 400 to 800 kg / h, the ratio obtained by dividing the outer diameter of the steel ingot by the outer diameter of the electrode to 1.2 to 1.7, and maintaining the MC It was manufactured by controlling the size of the type carbide grains. Table 2 shows the cutting test results of the cutting tools using the materials of Table 1 in terms of the maximum wear amount. Example 1 shows the results of a wet hob cutting test, Example 2 shows the results of a dry hob cutting test, and Example 3 shows the results of a roughing end mill cutting test (dry).

[0017]

[Table 1]

(Example 1) In the first example, solid hobs were manufactured from the steels of the present invention shown in Tables 7 to 10 and the comparative steels shown in Tables 1 to 3, and a cutting test by wet machining was performed as follows. After performing under the conditions, the wear amount of the cutting edge was measured.・ Tool shape: Solid hob (outer diameter: φ70, number of strips: 1,
Coating: Titanium-based film (removal of rake face))-Work material: S45C (hardness: HB175)-Cutting speed: 115 m / min-Cutting depth: 6.75 mm-Feed: 3.14 mm / rev-Cutting Length: 25m ・ Wet

The results are shown in Example 1 in the left column of Table 2, FIGS. 1 and 2. FIG. 1 shows the maximum flank wear (A) and the maximum crater wear (B) of the cutting edge in wet machining of a solid hob using the area ratio (%) of MC type carbide having an equivalent circular diameter of 5 to 14 μm as a parameter. It is. FIG. 2 shows the maximum flank wear amount (A) and the maximum crater wear amount (B) of the cutting edge using the minimum major axis and minor axis ratio of MC type carbide having an equivalent circular diameter of 5 to 14 μm as a parameter.
The rake face of the hob for wet processing was removed from the beginning in order to make the rake face the same as that without coating after regrinding.

[0020]

[Table 2]

FIG. 1 (A) shows the relationship between the maximum flank wear amount and the area ratio of MC type carbide having an equivalent circular diameter of 5 to 14 μm in each steel. 6%
The bottom is a U-shape, and between 3 and 8%, the wear amount is almost stable and the amount of wear is small. Invention Steels 7, 8, 9 and 10
Is located at the bottom where the amount of wear is the least of 4.6 to 6.1%. For example, the steel 8 of the present invention is 2.7 times as large as the comparative steel 2 which is a conventional high speed tool steel of the same composition, It is 1.8 times superior to Comparative Steel 3 which is a powdered high-speed tool steel of the same composition, and 1.6 times superior to Comparative Steel 1 which is a conventional high-speed tool steel for hob. Most of the wear of the comparative steels 1 and 2 was caused by chipping.

FIG. 1B shows the relationship between the maximum crater wear and the area ratio of MC type carbide having an equivalent circular diameter of 5 to 14 μm in each steel. The relationship diagram is also shown in FIG. It has a U-shape with a bottom of 6%, and between 3 and 8%, the amount of wear is almost stable and the amount of wear is small. Inventive steels 7, 8, 9 and 10 are located at the bottom with the least amount of wear of 4.6 to 6.1%, for example, Inventive steel 8 is a comparative steel which is a smelted high speed tool steel of the same component. 2.2 times better than 2, 1.3 times better than comparative steel 3 which is a powdered high speed tool steel of the same composition, and 1.5 times better than comparative steel 1 which is a conventional high speed tool steel for hob. ing. The wear of Comparative Steels 1 and 2 was due to adhesive wear and chipping due to insufficient heat resistance.

FIG. 2A shows the relationship between the maximum flank wear amount and the minimum ratio of the major axis to the minor axis of the MC type carbide having an equivalent circular diameter of 5 to 14 μm in each steel. , 2
In contrast, the steels 7, 8, 9 and 10 of the present invention having a minimum major axis / minor axis ratio of 0.3 or more are stable and have a small wear amount.

FIG. 2B shows the relationship between the maximum crater wear and the minimum major axis / minor axis ratio of the MC type carbide having an equivalent circular diameter of 5 to 14 μm in each steel. As in the case of surface wear, comparative steels 1 and 2
Invention steels 7, 8, and 9 having a minimum major axis / minor axis ratio of 0.3 or more.
And 10 are stable and have low wear.

(Example 2) In the second example, after the inventive steels 7 to 10 and comparative steels 1, 2 and 5 shown in Table 1 were worked, heat-treated and ground, the titanium-alloy composite multilayer by PVD was used. A solid hob was manufactured by applying the film, and a cutting test by dry machining was performed under the following conditions, and then the wear amount of the cutting edge was measured.・ Tool shape: Solid hob (outer diameter: φ75, number of strips: 4,
Coating: Titanium-alloy composite multilayer film (removing rake face)) Work material: SCr420 (Hardness: HB180) Cutting speed: 200 m / min Cutting depth: 4.05 mm Feed: 2.5 mm / Rev ・ Cutting length: 250m ・ Dry type

The results are shown in Example 2 in the middle column of Table 2, and in FIGS. 3 and 4. FIG. 3 shows the maximum flank wear amount (A) and the maximum crater wear amount (B) of the cutting edge portion in dry machining of a solid hob using the area ratio (%) of MC type carbide having an equivalent circular diameter of 5 to 14 μm as a parameter. It is. FIG. 4 shows the maximum flank wear amount (A) and the maximum crater wear amount (B) of the cutting edge using the minimum major axis and minor axis ratio of MC type carbide having an equivalent circular diameter of 5 to 14 μm as a parameter.
The rake face of the hob for wet processing was removed from the beginning in order to make the rake face the same as that without coating after regrinding.

FIG. 3 (A) shows the relationship between the maximum flank wear amount and the area ratio of MC type carbide having an equivalent circular diameter of 5 to 14 μm in each steel. 6
% Is a U-shape with a bottom, and between 3 and 8%, the wear amount is almost stable and the amount of wear is small. Invention Steels 7, 8, 9 and 1
0 is located at the bottom of 4.6 to 6.1% with the least amount of wear. For example, Steel 8 of the present invention is 2.8 times higher than Comparative Steel 2 which is a smelted high-speed tool steel of the same composition. It is 1.9 times better than the comparative steel 5 which is an alloy powder high speed tool steel, and 1.7 times better than the comparative steel 1 which is a conventional high speed tool steel for hob.
Furthermore, as compared with FIG. 1A of the first embodiment, the dry processing is more effective.

FIG. 3B shows the relationship between the maximum crater wear and the area ratio of MC type carbide having an equivalent circular diameter of 5 to 14 μm in each steel. % Is a U-shape with a bottom, and between 3 and 8%, the wear amount is almost stable and the amount of wear is small. Inventive steels 7, 8, 9 and 10 are located at the bottom with the least wear of 4.6 to 6.1%, for example, the developed steel 8 is a comparative high-speed tool steel of the same composition as a smelted high-speed tool steel. 6.1 times higher than No. 2, 3.1 times higher than comparative steel 5 which is a high alloy powder high speed tool steel, and 3.6 times better than comparative steel 1 which is a conventional high speed tool steel for hob. ing. Furthermore, compared to FIG. 1B of the first embodiment, the dry processing is more effective.

FIG. 4 (A) shows the relationship between the maximum flank wear amount and the ratio of the minimum major axis to the minor axis of the MC type carbide having an equivalent circular diameter of 5 to 14 μm in each steel. Invention steels 7, 8, 9 and 10 having a ratio of 0.3 or more are stable and have a small amount of wear.

FIG. 4 (B) shows the maximum crater abrasion amount and the maximum crater abrasion amount of MC type carbide having an equivalent circular diameter of 5 μm or more in each steel. It is shown as a relationship with the major axis / minor axis ratio, and the developed steel 7 having a minimum major axis / minor axis ratio of 0.3 or more,
8, 9 and 10 are stable and have low wear.

(Embodiment 3) In the third embodiment, end mills were manufactured from inventive steels 7 to 10 and comparative steels 1, 2, 3, 4 and 6 shown in Table 1, and cutting tests were performed by dry machining. Was performed under the following conditions, and the wear width of the cutting edge was measured.・ Tool shape: Roughing end mill (outer diameter: φ20, coating: titanium-based composite film) ・ Work material: S50C (hardness: HB180) ・ Cutting speed: 60m / min ・ Feed: 0.067mm / tooth ・ Cutting length ： 6m ・ Dry type

The results are shown in Example 3, FIGS. 5 and 6 in the right column of Table 2. FIG. 5 shows the maximum wear width of the cutting edge in dry machining of a roughing end mill, using the area ratio (%) of MC type carbide having an equivalent circular diameter of 5 to 14 μm as a parameter. FIG. 6 shows the maximum wear width of the cutting edge as a parameter with the minimum major axis / minor axis ratio of the MC type carbide having an equivalent circular diameter of 5 to 14 μm. In this example, a cutting test was performed in a state where the cutting edge portion was entirely coated.

FIG. 5 shows the relationship between the maximum wear width and the area ratio of MC type carbide having an equivalent circular diameter of 5 to 14 μm in each steel. U-shaped, and between 3% and 8%, the amount of wear is almost stable and the amount of wear is small. Invention steels 7, 8, 9 and 10 have 4.6 to
Located at the bottom with the lowest wear of 6.1%, for example,
Invention steel 8 is comparative steel 2 which is a smelted high-speed tool steel of the same composition.
9.2 times better than that of Comparative Steel 6, which is a powdery high-speed tool steel of a high alloy.

FIG. 6 shows the relationship between the maximum wear width and the minimum major axis / minor axis ratio of MC type carbide having an equivalent circular diameter of 5 to 14 μm in each steel. Inventive steels 7, 8, 9 and 10, which are 3 or more, are stable and have a small wear width.

[0035]

As described above, in the present invention, the high-speed tool steel, which is a material, has a weight ratio of 2 to 4% of V, 7 to 10% of Co, or 4 to 6% of V, and The maximum equivalent circular diameter of MC type carbide in the steel at the cutting edge is 5 to 9%.
１４14 μm, and the cutting tool with a long diameter and short diameter ratio of MC type carbide of 0.3 or more, the high-speed cutting tool became very excellent against abrasion and chipping of the cutting edge. .

Preferably, the area ratio of the MC type carbide grains having an equivalent circular diameter of 5 to 14 μm in the cross section of the grains parallel to the forging and rolling axes is 3 to 8%. , Improved chipping. Furthermore, it has heat resistance enough to withstand dry processing, and has good compatibility with the titanium-alloy-based ceramic coating composite film by PVD, and one or two types of titanium-based or titanium-alloy-based ceramic coating by PVD on the cutting edge surface. By applying the above composite film, abrasion resistance and chipping resistance were further improved, and it became more suitable for dry processing.

Therefore, it is very effective in improving the service life and quality of the hobbing tools represented by the hob.
It is expected to exhibit excellent performance in dry processing, which is expected to increase the usage in the future.

[Brief description of the drawings]

FIG. 1 shows a cutting test result of a first embodiment of the present invention.
(A) shows the maximum flank wear of the cutting edge portion in the wet machining of solid hobbs made of inventive steels 7 to 10 and comparative steels 1 to 3 and MC type carbide having an equivalent circular diameter of 5 to 14 μm in each steel. (B) shows the maximum amount of crater wear at the cutting edge and the equivalent circular diameter in each steel of 5 to 5%.
It shows the relationship with the area ratio of MC-type carbide of 14 μm.

2A and 2B are cutting test results of the first embodiment of the present invention, as in FIG. 1. FIG. 2A shows the maximum flank wear of the cutting edge and the MC type having an equivalent circular diameter of 5 to 14 μm in each steel. (B) shows the maximum crater wear at the cutting edge and the equivalent circular diameter of each steel of 5 to 14 μm.
3 shows the relationship between m and the minimum major axis / minor axis ratio of MC type carbide.

FIG. 3 shows a cutting test result of a second embodiment of the present invention.
(A) shows inventive steels 7 to 10, comparative steels 1, 2, and 5.
It shows the relationship between the maximum flank wear of the cutting edge and the area ratio of MC type carbide having an equivalent circular diameter of 5 to 14 μm in each steel in dry machining of the solid hob manufactured in the above,
(B) shows the relationship between the maximum crater wear at the cutting edge and the area ratio of MC type carbide having an equivalent circular diameter of 5 to 14 μm in each steel.

4A and 4B are cutting test results of the second embodiment of the present invention, as in FIG. 2; FIG. 4A shows the maximum flank wear of the cutting edge and the MC type having an equivalent circular diameter of 5 to 14 μm in each steel; (B) shows the maximum crater wear at the cutting edge and the equivalent circular diameter of each steel of 5 to 14 μm.
3 shows the relationship between m and the minimum major axis / minor axis ratio of MC type carbide.

FIG. 5 shows a cutting test result of a third embodiment of the present invention.
The relationship between the maximum wear width of the cutting edge portion and the area ratio of MC type carbide having an equivalent circular diameter of 5 to 14 μm of each steel type in dry machining of roughing end mills manufactured using inventive steels 7 to 10 and comparative steels 1 to 4 and 6 It shows the relationship.

FIG. 6 is a cutting test result of the third embodiment of the present invention, similarly to FIG. 5, showing the maximum wear width of the cutting edge portion and the ratio of the minimum major axis to the minor axis of MC type carbide having an equivalent circular diameter of 5 to 14 μm in each steel. It shows the relationship with.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Shunichi Asakura 1-1-1 Fujikoshi Honcho, Toyama City, Toyama Prefecture Fujikoshi, Inc. (56) References JP-A-6-256915 (JP, A) JP-A-2 -15845 (JP, A) JP-A-4-180540 (JP, A) JP-A-4-358046 (JP, A) JP-A-6-145888 (JP, A) JP-A-6-322482 (JP, A) JP-A-9-296256 (JP, A) JP-A-5-33102 (JP, A) JP-A-10-25546 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23B 27/14 C22C 38/00 302 C22C 38/12

Claims (6)

(57) [Claims] 1. A cutting tool having a cutting edge made of high-speed tool steel, wherein the high-speed tool steel has a weight percentage of C: 0.6 to 1.
8%, Si: 1.2% or less, Mn: 0.5% or less, Cr: 3.5-5.0%,
Mo: less than 10%, W: less than 21%, and by weight,
V: 2 to 4%, Co: 7 to 10%, with the balance being Fe and unavoidable impurities, the area of the cross section of the largest carbide grain among the MC type carbide grains in the cutting edge steel is defined as the area of a circle. The maximum equivalent circular diameter of the equivalent circular diameter, which is the diameter of the circle in the case of replacement, is the maximum equivalent circular diameter of 5 to 14 μm, and the equivalent circular diameter of the MC type carbide particles of 5 to 14 μm. A cutting tool, wherein the ratio of the major axis to the minor axis of the particle cross section is 0.3 or more. 2. A cutting tool having a cutting edge made of high-speed tool steel, wherein the high-speed tool steel has a weight percentage of C: 0.6 to 1.
8%, Si: 1.2% or less, Mn: 0.5% or less, Cr: 3.5-5.0%,
Mo: less than 10%, W: less than 21%, and by weight,
V: 4 to 6%, Co: 4 to 9%, the balance is Fe and unavoidable impurities, and the area of the cross section of the largest carbide grain among MC type carbide grains in the steel at the cutting edge is the area of a circle. The maximum equivalent circular diameter which is the largest equivalent circular diameter of the equivalent circular diameter which is the diameter of the circle when replaced as
And, the equivalent circular diameter is 5 to 14 μm the ratio of the major axis to the minor axis of the particle cross section of the MC-type carbide grains, that is, the ratio of the minor axis of any one of the particle cross sections of the MC-type carbide grains divided by the major axis is 0.3
A cutting tool characterized by the above. 3. The method according to claim 1, wherein the MC type carbide grains having an equivalent circular diameter of 5 to 14 μm have an area ratio of 3 to 8% in a grain cross section parallel to a forging and rolling axis. The described cutting tool. 4. At least on the cutting edge surface of the cutting tool,
The cutting tool according to any one of claims 1 to 3, wherein one or two or more composite films of titanium-based or titanium-alloy-based ceramic coating by PVD are applied. 5. The high-speed tool steel according to claim 1, wherein a gas component containing O ₂ and N ₂ is prevented from entering the molten steel due to an inert atmosphere by an electroslag remelting method, and melting conditions: melting speed; 4. The method according to claim 1, wherein the ratio of the outer diameter of the steel ingot divided by the outer diameter of the electrode is maintained at 1.2 to 1.7, and the size of the MC type carbide grains is controlled.
The cutting tool according to any one of the above. 6. The cutting tool according to claim 1, wherein the cutting tool is used for dry machining.