JPH07138692A - Shaft or the like cutting tool and sintered hard alloy for the same - Google Patents

Abstract

PURPOSE:To obtain a sintered hard alloy for shaft or the like cutting tool, excellent in wear resistance and chipping resistance and having superior properties by mixing a metal carbide powder, a Co or Ni powder, and a WC powder of specific grain size in specific ratio and sintering the resulting powder mixture. CONSTITUTION:The sintered hard alloy composed essentially of WC is obtained by sintering a powder mixture of raw materials consisting of, by weight, 0.2-30% of powder of the carbides of the group IVa, Va, and VIa metals excluding W, 4-20% of Co and/or Ni powder to be binding phase, and the balance WC powder of 0.3-0.7mum average grain size with inevitable impurities. In this case, a part of the above carbide powder can be substituted for TC-TaC-WC powder, and further, it is preferable to use VC powder by the amount in the range of 0.2-0.5% and average grain size and the difference of average grain size are regulated, preferably, to 0.1-1.0mum and <=0.5mum, respectively. By joining the cutting part of this sintered hard alloy to a shank part of prescribed length, the wear resistance and chipping resistance can be improved and the occurrence of breakage, etc., can be prevented, thus the shaft or the like cutting tool improved in properties can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cemented carbide which is useful as a material for a shaft cutting tool such as a drill, an end mill and a reamer, and a shaft cutting tool such as this, and more particularly to wear resistance of a blade portion of the shaft cutting tool. And a technique for improving pitting resistance.

[0002]

2. Description of the Related Art Hard alloys such as WC-based cemented carbide and TiC-based cermet produced by powder metallurgy have been widely used as turning chips and the like due to their excellent wear resistance. It is generally said that the properties of these materials tend to become brittle as the hardness increases. Therefore, these hard materials are high-speed tool steels (hereinafter abbreviated as "high speed steel") that are generally widely used as cutting and wear resistant tools.
Compared to, it had a toughness problem.

However, in recent years, the invention of ultrafine particle cemented carbide and the hot hydrostatic pressure treatment (hereinafter referred to as "H", which can completely eliminate the generation of pores, which is a difficulty of the powder metallurgy method).
A hard material having a toughness close to that of high-speed steel is being developed due to the progress of manufacturing methods, such as the positive adoption of "IP treatment").

On the other hand, although high speed steel is mainly used as a material for shaft cutting tools such as drills and end mills, demand for high speed machining is increasing day by day due to recent needs for high efficiency machining. These shaft cutting tools have a more complicated cutting mechanism than turning chips, which are widely used in high-speed cutting and whose theoretical aspects have been elucidated, and the load on the tool is large due to the problem of chip discharge. However, problems such as breakage and chipping could not be solved easily, and the road to high-speed cutting of these tools was blocked. However, as the technologies related to cemented carbide have been improved as described above, WC-based cemented carbide materials have come into widespread use in shaft cutting tools as well, making use of their excellent hardness, heat resistance, and rigidity. It seems that high-speed cutting and high-precision machining have become possible.

However, it has been pointed out that sudden breakage or chipping may occur depending on the conditions of use. It is considered that this is due to poor thermal conductivity due to the cutting heat generated at the tip of the cutting edge during cutting and an increase in cutting resistance due to wear deterioration. Therefore, under the present circumstances, it is desired to develop a cemented carbide material that solves these problems and further improves reliability.

[0006]

Cutting by a drill, for example, shows a complicated mechanism in which cutting conditions are different in the circumferential direction unlike turning chips. That is, basically, the thrust increases as it approaches the center of the shaft, while the cutting speed and torque tend to decrease sharply. Therefore, the pressing force in the axial direction predominantly acts on the chisel portion at the center of the shaft, and the material surface requires strength to withstand this force. On the other hand, since the cutting speed is high in the outer peripheral portion, heat resistance, wear resistance and chipping resistance are required. However, most of the cemented carbide drills currently in use have a WC of 1.5-2.
The alloy composition is based on coarse particles of 5 μm and to which a heat-resistant element is added. That is, it is said that a cemented carbide drill used for drilling of general steel materials and cast iron greatly affects the drill life due to the heat generated during drilling, and as a countermeasure against that, improve heat resistance. Cemented carbide with many elements added is used. However, since the thermal conductivity of such drill materials deteriorates slightly due to the addition of heat-resistant elements, cemented carbides generally called P and M types are WC
Under the present circumstances, the thermal conductivity is improved by coarsening (about 1.5 to 2.5 μm) in consideration.

However, when WC of coarse particles is used, the hardness is naturally lowered, the wear resistance is lowered, and the life of the cutting performance is shortened by the margin wear of the tip of the cutting edge. Further, in terms of chipping resistance due to the non-uniform structure of WC and binder phase, the conventional drills have not yet been completely solved, leaving a problem in terms of reliability.

By the way, it is considered that the cause of chipping or breaking in a shaft cutting tool such as a drill is influenced by both the material surface and the shape surface. Therefore, specific examples of drills in terms of shape include Miracle drill (trade name: Kobe Steel, Ltd.), New Point drill (trade name: Mitsubishi Materials Co., Ltd.), multi-drill (trade name: Sumitomo Metals Co., Ltd.). Various types of drills have been commercialized, such as Hosoi Drill (trade name), which is designed to solve the problem of chipping by devising the shape of the chisel part.
Also for the end mill, there has been proposed a tool having a positive rake angle to reduce the load applied to the blade, and a tool having a cutting edge with a pin angle for improving the finished surface. However, the present situation is that the variation in cutting life due to breakage such as chipping or breaking due to local wear or chipping of the cutting edge has not been completely eliminated.

On the other hand, tools that utilize functional characteristics from the viewpoint of materials have been developed, and it is generally effective to increase the transverse rupture force and improve the toughness in order to prevent chipping or breaking. It is said to be a means. However, wearability and toughness are contradictory properties, and even ultrafine particle alloys with excellent toughness are no exception. As a countermeasure, the blade edge is coated with a hard material with good wear resistance (film quality is TiC
However, there is also a problem that the coating is easily peeled off because the shape of the cutting edge is more complicated than that of the throwaway tip. Further, in cemented carbide end mills that use ultrafine particle alloys, tools coated to achieve a longer life have appeared, but there are still problems with variations in life and accuracy. The coating film is
It focuses on wear resistance and heat resistance, and is basically free from problems such as chipping and breaking.

In such a technical background, as means for simultaneously improving wear resistance and toughness and further improving machinability,
It is also effective to combine tools (for example, Japanese Patent Laid-Open No. 2-269).
No. 515). In such technology, compounding is generally achieved by brazing.For example, in a shaft cutting tool such as a tip muk drill, a cemented carbide chip is used for the blade part and a steel material is used for the shank part. However,
There are inherent problems of bond strength and breakage and peeling of joints due to thermal stress during brazing, and the problem of sudden breakage when using tools is still unsolved. Vacuum brazing technology has also been adopted, but the problems of thermal stress and joint strength described above still remain.

The present invention has been made under these circumstances, and an object thereof is to improve wear resistance and chipping resistance, prevent breakage and the like, and improve the performance of a shaft cutting tool. , And a cemented carbide useful for realizing such a shaft cutting tool.

[0012]

The cemented carbide for a shaft cutting tool of the present invention which has achieved the above object is a cemented carbide mainly composed of WC, and the periodic table 4A and 5A excluding W. , 6A
0.2 to 30% by weight of carbide powder of one or more metal elements selected from the group consisting of group elements, and 4 to 20% by weight of Co and / or Ni powder as a binder phase. And the balance is average particle size: 0.3 to 0.7 μm
The point is that the WC powder and the raw material mixed powder that is an unavoidable impurity are sintered.

The shaft cutting tool of the present invention which has achieved the above object uses the cemented carbide as described above as a material for the blade portion, and as the shank portion, periodic table 4 excluding W.
Proportion of 0.1 to 5% by weight of carbide powder of one or more metal elements selected from the group consisting of A, 5A and 6A group elements, and 4 to 8% by weight of Co and / or Ni powder as a binder phase. The essence is that a WC powder having an average particle diameter of 1 to 3 μm and the remaining raw material mixed powder which is an unavoidable impurity is mixed.

[0014]

The present invention basically defines the constitution of the starting raw material mixed powder.
Except the above, the compounding amount of carbide (hereinafter sometimes referred to as “heat resistant compound”) powder of one or more metal elements selected from the group consisting of elements of 4A, 5A, and 6A groups in the periodic table is 0.2 to 3
It should be 0% by weight. That is, this blending amount is 0.2
If it is less than 30% by weight, heat resistance improvement, which is a basic action of compounding these compounds, will not be exhibited. On the other hand, if it exceeds 30% by weight, a sharp decrease in toughness will occur. The above-mentioned heat-resistant compound basically assumes a metal element other than W among the elements of Groups 4A, 5A, and 6A of the Periodic Table, and it also includes a TiC-TaC-based carbide powder called so-called double carbide. However, if necessary, part of it may be Ti
A carbide powder containing W, such as C-TaC-WC (so-called triple carbide), may be used instead. WC contained in such a powder acts as a heat-resistant compound, unlike WC which forms a hard phase mainly as a cemented carbide.

The average particle size of the heat-resistant compound powder is 0.
The thickness is preferably 5 to 1.0 μm, and the wear resistance of the cemented carbide can be further improved by using such fine particles. Among the heat resistant compounds, TiC
Compounds such as Ta and TaC are also effective as grain growth inhibitors, but VC is more effective as a grain growth inhibitor even with a small addition amount of about 0.2 to 0.5% by weight.
That is, if the added amount of VC is less than 0.2% by weight, its effect is small, and if it exceeds 0.5% by weight, the toughness tends to be deteriorated.

On the other hand, Co and / or N serving as a binding phase
The powder mixture amount of i must be 4 to 20% by weight,
If it is less than 4% by weight, the toughness tends to deteriorate, and if it exceeds 20% by weight, the abrasion resistance tends to deteriorate.

The raw material mixed powder used in the present invention is as described above.
In addition, the balance consists of WC powder and inevitable impurities.
However, the average particle size of WC powder exceeds 0.3-0.7 μm
It is necessary to use fine particles. That is, the average particle size of the WC powder
Is 0.7 μm, the hardness is H _RA: A value of 91.8 or higher
Not obtained, inferior in wear resistance, shortened life due to local wear
Occurs, and the object of the present invention is not achieved.

The difference in average particle size between the WC powder having an average particle size of 0.3 to 0.7 μm and the heat resistant compound powder is 0.1 to 0.
Wear resistance is improved by making the uniform structure within 5 μm.
The chipping resistance is further improved.

As the mixing and mixing treatment method for preparing the above-mentioned raw material powder, a usual mixing method carried out by a conventional powder metallurgy method may be adopted. For example, an appropriate amount of an organic solvent (acetone, ethanol, Hexane, etc.), compounded powder and a molding aid are added and stirred, and the slurry-like raw material mixed powder is dried and granulated. If necessary, the raw material mixed powder used in the present invention may be mixed with carbon / nitride of elements such as Hf, Zr, and B at a ratio of 0.1 to 5% by weight. ， Contributes to heat resistance.

The cemented carbide of the present invention is obtained by sintering the above raw material mixed powder, but the procedure and means thereof are not particularly limited, and the following method may be followed, for example. One of them is to fill a mold or a rubber mold and then pressurize or hydrostatically press to make a molded body, and the other is to mix dried powder with a molding aid or binder (thermoplastic A resin, a lubricant, etc.) are added to make a clay, and then an extrusion molded product is produced by an injection molding machine. The material of the present invention is applicable to both molding methods. In addition, after molding, the above-mentioned molding aids and binders are removed, and semi-sintering treatment (700 to 1000 ° C) is carried out in order to provide appropriate strength.
Then, it is sintered as it is (1250 to 1500 ° C.), or it is processed to finish it into a predetermined shape and sintered in the same manner as described above. The sintering at this time is performed in a vacuum (1 × 10 to 1 × 10 ⁵ Torr) within the above temperature range. The sintered product is 100 to 200 at a temperature of 1200 to 1400 ° C. using an inert gas (Ar, N ₂ etc.) as a pressure medium.
It is preferable to perform the HIP treatment at a pressure of 0 kg / cmm ² .

In the present invention, it is important that the structure after sintering and HIP treatment has a fine and uniform structure with WC and heat-resistant compounds (TiC, TaC, Cr ₃ C _2, etc.). That is, when coarse grains are used, a structure as shown in FIG. 2 is formed, a Co-rich phase is formed in the binder phase, damage due to chipping due to occurrence of local wear, wear resistance deterioration due to hardness decrease, and thermal conductivity decrease. Etc. are likely to occur.

Therefore, in the conventional coarse-grain type P and M type materials, the above-mentioned damage phenomenon is likely to occur, whereas the material of the present invention uses a raw material mixed powder using fine particles as a starting material, and Since it is produced by a treatment method that does not cause grain growth, a cemented carbide drill material (especially the material for the blade) that has a uniform structure as shown in Fig. 1 and that has superior wear resistance and chipping resistance is produced. You can

It is also within the technical scope of the present invention to construct a shaft cutting tool by using the above-described cemented carbide as a material for the blade portion and cemented carbides having different compositions as the shank portion and joining these. Although included, the composition of the cemented carbide used in the shank portion is as follows.

It is important that the material used for the shank portion has a composition that easily absorbs the cutting heat generated at the blade portion. Therefore, by adopting a composition having good thermal conductivity, the cutting life can be extended. To do. In order to improve the thermal conductivity, it is preferable to reduce Co and coarsen carbide particles such as WC. From this point of view, as the WC powder, coarse particles having an average particle diameter of 1 to 3 μm are used, and Co and / or N serving as a binder phase.
If i is less than 3% by weight, the toughness is insufficient, and 9% by weight
If it exceeds, the composition is inferior in terms of thermal conductivity, so a composition in the range of 4 to 8% is most effective.

In the shaft cutting tool, the blade portion and the shank portion are constituted by the above-mentioned composition, and the length ratio thereof is blade portion: shank portion = 2 to 3 × d (outer peripheral diameter): total length− (2 to 3). × d
(Peripheral diameter)) is optimal. This is based on the thickness of the work material and is selected to have a length that does not directly affect the cutting performance. That is, if the length of the blade is less than 2d, the joint interface becomes a region in direct contact with the work, causing damage such as boundary wear, and if the length of the blade exceeds 3d, the cutting heat generated at the blade is transferred. Will not be exhibited,
Therefore, the ratio range of the cutting edge and the shank portion of the joined body is defined as described above.

The joint interface between the blade portion and the shank portion is not flat, but it is effective to form a plurality of recessed grooves and ridges that fit with each other, and the pitch interval is 0.1 to 0.3 mm. Most preferably. If this pitch is less than 0.1 mm, the effect in terms of heat conductivity is small, and if it exceeds 0.3 mm, the bonding strength decreases. That is, according to the present invention, the cutting heat generated in the blade portion is easily released to the shank portion side, and the pitch interval is defined so that the function can be exerted. The specific shapes of the plurality of concave grooves and the convex stripes are not particularly limited, and the shape in the plane perpendicular to the direction in which the concave grooves and the convex stripes extend includes both a wavy shape and a sawtooth shape. It is the purpose.

As described above, by adopting an ultrafine particle alloy composition material for the blade portion, excellent performance in abrasion resistance and chipping resistance is exhibited, and cutting heat generated in the blade portion is transferred to the shank portion. The cutting performance can be further improved by transmitting to the shank portion made of a cemented carbide material that is easily absorbed on the side, that is, has good thermal conductivity.

The present invention will be described in more detail with reference to the following examples, but the following examples are not intended to limit the present invention, and any modification of the design of the present invention can be made without departing from the spirit of the preceding and following paragraphs. It is included in the technical scope.

[0029]

【Example】

Example 1 WC powder with an average particle size of 0.5 μm, average particle size of 1.5 μm
m Co powder and / or Ni powder, TiC, Ta
Periodic table 4 excluding W such as C, VC, Cr ₃ C ₂ and NbC
Carbide (heat resistant compound) of Group A, 5A, 6A metal, or powder of triple carbide (TiC-TaC-WC) or double carbide (TiC-TaC) having an average particle size of 0.7 μm, or a vibration mill or Particle size crushed by attritor is less than 1.0μm and average particle size is 0.8
Using the starting materials such as μm heat-resistant compound powder, the compounding compositions shown in Table 1 and Table 2 were prepared.

Each of these blended powders was placed in an attritor, the organic solvent (acetone or hexane) and the molding aid were simultaneously stirred, and after 5 hours, they were collected and dried and granulated. Then, 1000 kg / cm ^{2 with} a predetermined mold
The molded body is molded under the above pressure and subjected to semi-sintering treatment (450 ° C ×
4 hours + 850 ° C. × 2 hours). After that, it is processed into a drill shape, and 1380 ° C in a vacuum of 1 × 10 ⁴ Torr
× After 0.5 hour sintering treatment, add 135
HIP treatment was performed at 0 ° C. in an inert gas (Ar) at 1500 atm. The material properties (hardness, transverse rupture strength) after sintering and HIP treatment are also shown in Table 1 and Table 2.

[0031]

[Table 1]

[0032]

[Table 2]

In order to evaluate the cutting performance of the obtained cemented carbide, it was processed into a cemented carbide drill having a diameter of 10 mm and punched under the following conditions. Work Material: S50C Cutting Speed: 120mm / min Feed: 0.25mm / rev Cutting Oil: Emulsion Drill Diameter: 10.0mm Plate Thickness: 1.6 × D (Drill Diameter) Cutting life is different from the shape change of cutting chips. The final life was judged from the generation of cutting noise and abnormal wear of the cutting edge. As a result, as shown in Table 3, the material of the present invention has a life of about 2 to 3 times that of the conventional material, and as shown in FIGS. 3 and 4, the relationship between the WC grain size and the cutting life and the hardness. It was clarified that and cutting life are clearly related.

[0034]

[Table 3]

Example 2 Table 4 shows the composition and characteristics of the raw material mixed powder when manufacturing the shaft cutting tool of the present invention composed of the blade portion and the shank portion. In addition, Table 5 shows the composition and characteristics of the conventionally used raw material mixed powder. The composition of the blade is based on ultrafine powder as a starting material, WC is 0.5 μm as a base, and carbides of 4A, 5A, and 6A groups in the periodic table excluding W having a particle size of 1.0 μm or less are 0.2 Add 30% by weight to form a binder phase C
O and / or Ni is in the range of 4 to 20% by weight. Further, VC is also added as an element for suppressing grain growth, and as a result of the above, it can be seen that the value of hardness, which is closely related to wear resistance, is higher than that of conventional materials. On the other hand, the composition applied to the shank has a WC particle size of 1 to 3 μm.
Coarse particles are used, and 0.1 to 5% by weight of carbides of Groups 4A, 5A, and 6A of the periodic table excluding W is added or not added, and Co and / or Ni serving as a binder phase has 4 to 8%. It is in the range of% by weight. As a result, the thermal conductivity is good, and the cutting heat generated by the blade, which is the aim of the present invention, is easily transmitted to the shank side.

[0036]

[Table 4]

[0037]

[Table 5]

The raw material powders shown in Tables 4 and 5 were weighed and blended, mixed and dispersed in an organic solvent with an attritor, and then dried and granulated. When molding the obtained granulated powder, first insert the granulated powder used for the blade portion accumulated in the hopper into a predetermined molding die, and then vibrate the predetermined amount of granulated powder used in the shank portion. While throwing in, 1000kg /
The molding process was performed at a pressure of cm ² or more. In this case, the length of the cutting edge portion is 2 to 3 x d (outer peripheral diameter), that is, the cutting edge: shank = (2 to 3 x d (outer peripheral diameter)): total length- (2
Granulated powders were individually added so as to have a diameter of ˜3 × d (outer peripheral diameter), and a desired molded body was manufactured. After dewaxing and half-baking this molded body, finish it into the target material shape by half-baking, and sinter at a temperature of 1280 to 1500 ° C under a vacuum of 1 x 10 to 1 x 10 ^-5 Torr. Was done. After that, an inert gas such as Ar is used as a pressure medium for 100
1200 to 1400 ° C at a pressure of up to 2000 kg / cm ^2.
A hot isostatic pressing process (HIP process) for high-temperature treatment was performed to obtain a material of the alloy of the present invention.

A cutting test was conducted using the material of the present invention and the comparative material. The cutting test was performed using a drill (10 mmφ) and an end mill (diameter: 10 mm, 2 blades) under the following conditions. Further, in order to compare under the same conditions, the same coating (Al, Ti) N was used for the material of the present invention and the comparative material.
Cutting was evaluated by the processed one. (Drill cutting conditions) Cutting speed: 120 mm / min Feed: 0.25 mm / rev Plate thickness: 16 mm Work material: S50C, 50C Cutting oil: Emulsion oil (End mill cutting conditions) Rotation speed: 1910 rpm Work material: SKD11 Feed: 306 mm / m (0.08 mm / blade) Depth of cut: 1.0 mm (R) x 15 mm (L) Cutting method: Down cut, air blow Cutting length: 6 m

The results are collectively shown in Table 6. In the cutting test by the drill, the material of the present invention shows a long life of 2000 holes or more, but the conventional coarse grain type drill has a long life of 300. Only a life of 400 holes is obtained. This is because the wear resistance of the cemented carbide base material has an effect on the cutting performance even under the same film coating, the material of the present invention has a composition with excellent wear resistance of the blade portion, and the shank portion has a cutting heat generated at the blade portion. It seems that the effect is due to the action to reduce the. Further, also in the end mill, the material of the present invention has a value of 1/2 of the comparative material in terms of the amount of wear due to reduced diameter, and it can be seen that excellent cutting performance is exhibited by the same effect as above.

[0041]

[Table 6]

Table 7 shows the results of examining the bending strength of the material of the present invention (No. 25). In addition, as a comparative material, the results obtained by investigating the transverse rupture strength of the one obtained by joining the sintered bodies of the end mill material (blade portion: 4A) (FIG. 5B) are also shown. Further, the A portion (bonding strength) and the B portion are values measured at the positions shown in FIG. No defects such as pores and cracks were observed at the joining interface in the material of the present invention, and almost the same values as those of the blade base material or the shank base material were obtained, which means that there is no strength reduction due to bonding. Had proved.

[0043]

[Table 7]

[0044]

The present invention is constituted as described above, and is useful for realizing a shaft cutting tool which has a longer life such as perforation processing than the conventional one, and a shaft cutting tool such as this. Cemented carbide was realized.

[Brief description of drawings]

FIG. 1 is an explanatory view schematically showing the structure of a cemented carbide of the present invention.

FIG. 2 is an explanatory view schematically showing the structure of a conventional cemented carbide.

FIG. 3 is a graph showing the relationship between hardness and cutting life of each cemented carbide.

FIG. 4 is a graph showing the relationship between WC powder average particle diameter and cutting life of each cemented carbide.

FIG. 5 is an explanatory view showing a bending test piece.

Continued Front Page (72) Minoru Fukunaga 179-1 Kanegasaki Nishi-Oike, Uozumi-cho, Akashi-shi, Hyogo Kobe Steel Works Akashi Plant

Claims (8)

[Claims] 1. A cemented carbide mainly composed of WC, comprising:
0.2 to 3 of carbide powder of one or more kinds of metal elements selected from the group consisting of elements of 4A, 5A and 6A groups in the periodic table excluding
In addition to 0% by weight, Co and / or Ni powder serving as a binder phase was mixed in a ratio of 4 to 20% by weight, and the balance was WC powder having an average particle size of 0.3 to 0.7 μm and unavoidable impurities. A cemented carbide for a shaft cutting tool, which is obtained by sintering a raw material mixed powder. 2. A raw material mixed powder in which a part of the carbide powder of one or more metal elements selected from the group consisting of elements of groups 4A, 5A and 6A of the periodic table is replaced with TiC-TaC-WC powder is used. A cemented carbide for a shaft cutting tool according to claim 1. 3. A raw material mixed powder containing 0.2 to 0.5% by weight of VC powder as a carbide powder of at least one metal element selected from the group consisting of elements of groups 4A, 5A and 6A of the periodic table. The cemented carbide for a shaft cutting tool according to claim 1 or 2, wherein the cemented carbide is used. 4. A raw material mixed powder having an average particle size of 0.5 to 1.0 μm of a carbide powder of one or more metal elements selected from the group consisting of elements of Groups 4A, 5A and 6A of the periodic table is used. A cemented carbide for a shaft cutting tool according to any one of claims 1 to 3. 5. The average particle size of the main WC powder and 1 selected from the group consisting of elements of Groups 4A, 5A and 6A of the periodic table.
Difference in average particle size of carbide powders of at least one kind of metal element is 0.5
The cemented carbide for a shaft cutting tool according to any one of claims 1 to 4, wherein a raw material mixed powder having a particle size of not more than μm is used. 6. A shaft cutting tool configured by joining a blade portion and a shank portion, wherein the cemented carbide according to any one of claims 1 to 5 is used as the blade portion, and W is used as the shank portion. Excludes 0.1 to 5% by weight of carbide powder of one or more metal elements selected from the group consisting of elements of groups 4A, 5A and 6A of periodic table, and 4 to 8 powder of Co and / or Ni as a binder phase. A shaft cutting tool characterized by using a mixture of WC powder having an average particle diameter of 1 to 3 μm and a raw material mixed powder which is an unavoidable impurity, which is blended at a ratio of wt%. 7. The shaft cutting tool according to claim 6, wherein the length ratio of the blade portion and the shank portion satisfies the following expression (1). Blade part: Shank part = (2-3d): (Overall length-Length of blade part) (1) where d: Outer diameter 8. The joint groove between the blade portion and the shank portion is formed with a plurality of recessed grooves and ridges to be fitted with each other, and the pitch interval thereof is 0.1 to 0.3 mm. A shaft cutting tool according to item 7.