JP2003105459A - Cemented carbide, and production method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain cemented carbide in which deposition and coagulation with a material to be machined on machining can be suppressed, and a satisfactory hard film can be formed. SOLUTION: In the cemented carbide having a composition containing 2 to 10 wt.% of bonding metals of cobalt (Co) and/or nickel (Ni), and 0 to 30 wt.% of the carbide, nitride and/or carbonitride of at least one kind selected from the groups consisting of the groups 4a, 5a and 6a metals in the Periodic Table, and containing 10 to 300 ppm iron (Fe), and 100 to 1,000 ppm chromium (Cr), and the balance tungsten carbide with inevitable impurities, the vicinity of the surface is provided with a surface region satisfying the condition of psuf <pin provided that the total content of the bonding metals at the inside of the cemented carbide is defined as w1in , the total content of iron (Fe) and chromium (Cr) at the inside of the cemented carbide is defined as w2in , the total content of the bonding metals in the surface region of the cemented carbide is defined as w1suf , and the total content of iron (Fe) and chromium (Cr) in the surface region of the cemented carbide is defined as w2suf , and pin =w2in /w1in , and psuf =w2suf /w1suf .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cemented carbide and a method for producing the same, and particularly to a cutting tool suitable for cutting general steel such as carbon steel, alloy steel and stainless steel, a sliding member, and a wear resistant member. Cemented carbide having a high strength and high toughness surface and a method for producing the same.

[0002]

Cemented carbide, which is widely used for metal cutting, sliding members, wear resistant members, etc., has a hard phase mainly composed of tungsten carbide (WC) as cobalt (Co) or nickel (Ni). In the bonding phase of WC-Co (N
i) An alloy or a system in which a hard phase of a carbide, nitride or carbonitride of a metal of Groups 4a, 5a and 6a of the Periodic Table is dispersed in the WC-Co (Ni) alloy is known. These cemented carbides are particularly used as cutting tools for general steel such as carbon steel, alloy steel, and stainless steel.

Generally, as a method for producing such a cemented carbide, the raw material powders constituting the cemented carbide as described above are crushed, mixed and shaped, and then at 1350 to 1600 ° C. for 1 to 3 hours. A method of firing to some extent is known.

[0004]

However, in the above conventional cemented carbide, when it is used as a cutting tool or the like, iron (Fe) contained as an impurity in the cemented carbide.
And chromium (Cr) combine with iron (Fe) and chromium (Cr), which are contained in large amounts in the work material that has become hot during cutting, and the work material is welded or adhered to the surface of the cutting tool and cut. Abnormal wear of action parts such as blades, cutting resistance increases and damage to the cutting tool surface is likely to occur, and roughness of the surface of the work piece deteriorates due to unevenness of weld deposits and adhesion There was a problem such as.

Iron (Fe) and chromium (Cr) in the cemented carbide are contained as unavoidable impurities in the primary raw material or are mixed in the manufacturing process.
It cannot be completely removed industrially, and the contents of iron (Fe) and chromium (Cr) mixed in the manufacturing process cannot be controlled because they change due to changes in the process and the surface condition of the crusher. It was a thing.

Further, since iron (Fe) has a high affinity for carbon, when the content of iron (Fe) on the surface of the cemented carbide is large, it is hard by a vapor phase synthesis method such as a CVD method or a PVD method. When coating a film, carbon and iron (Fe) are preferentially bonded, and an embrittlement phase such as η phase is easily generated at the interface between the cemented carbide and the hard film, and the adhesion strength of the hard film decreases. As a result, there has been a problem that the hard coating peels and breaks, and when it is used as a cutting tool or a sliding member, the life is shortened.

Therefore, the present invention has been made to solve the above problems, and its purpose is to prevent welding and adhesion to a work material during cutting, sliding, etc., and to obtain good hardness. It is an object to provide a cemented carbide capable of forming a coating.

[0008]

Means for Solving the Problems The present inventor has
In particular, as a result of studying a structure capable of suppressing the influence of iron (Fe) and chromium (Cr) in the cemented carbide on the work material, the content of iron (Fe) and chromium (Cr) in the cemented carbide is controlled. Cobalt (C
o) and / or nickel (Ni) to iron (F
By reducing the content ratio of e) and chromium (Cr) from the inside of the cemented carbide, it is possible to suppress welding and adhesion with the work material, and to form a good hard coating even when forming a hard coating. The present invention has been accomplished by finding that a cemented carbide that can be formed by deposition can be obtained.

That is, the cemented carbide according to claim 1 contains 2 to 20% by weight of a binding metal of cobalt (Co) and / or nickel (Ni), from the group of metals of Groups 4a, 5a and 6a of the periodic table. It contains 0 to 30% by weight of at least one kind of carbide, nitride and / or carbonitride selected, 10 to 300 ppm of iron (Fe), and chromium (Cr).
In a cemented carbide containing 100 to 1000 ppm of _Al , with the balance being tungsten carbide and unavoidable impurities, the total content of the binding metal inside the cemented carbide is w _{1 in} , near the surface of the cemented carbide. The total content of iron (Fe) and chromium (Cr) in the alloy is w _2in , the total content of the binding metal in this cemented carbide surface region is w _{1 suf} , and the iron (Fe) in this cemented carbide surface region is and the total content of chromium (Cr) and _{w 2 suf, p in = w} 2in / w 1in, p suf = w
When the _2suf / w _1suf, is characterized in that it has a surface area that satisfies the conditions of the p _suf <p _{i n.}

In the above cemented carbide, in the surface region
The p_sufAnd p_inRatio with (p_suf/ P _in) Has a maximum value of 0.
The thickness of the surface region is preferably 5 to 0.95.
It is desirable that the thickness is 1 to 20 μm.

Further, in the above-mentioned cemented carbide, the carbide, nitride, carbonitride, TiAlN, TiZrN, TiCrN of Group 4a, 5a, and 6a metals of the periodic table are formed on the surface of the cemented carbide.
It is desirable that at least one hard coating film made of at least one selected from the group consisting of DLC (diamond-like carbon), diamond and Al ₂ O ₃ is formed by deposition with a total thickness of 1 to 30 μm.

A method for producing a cemented carbide according to a fifth aspect of the present invention is a method of manufacturing a tungsten carbide powder and at least one kind of carbide, nitride and / or carbonitride selected from the group of metals of groups 4a, 5a and 6a of the periodic table. Powder and raw material powder consisting of cobalt (Co) and / or nickel (Ni) powder are pulverized and mixed, and then molded, and then 1350 in a non-oxidizing atmosphere.
The first baking temperature of ~ 1600 ° C is maintained for 0.3 to 2 hours, and the second baking temperature is 20 ~ 200 ° C lower than the first baking temperature.
It is characterized in that it is cooled to the firing temperature of, and then held at the second firing temperature in vacuum for 1 to 3 hours.

In the above method for producing a cemented carbide, the parts used in the crushing and mixing of the raw material powder and the parts of the crushing member that come into contact with the raw material powder are iron (Fe) and chromium (C).
It is desirable not to contain r).

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below. The cemented carbide of the present invention has a tungsten carbide phase and cobalt (Co) and / or nickel (Ni).
2 to 20% by weight, especially 6 to 15% by weight of the binding metal of
0 to 30% by weight, particularly 2 to 20% by weight, and further 5% by weight of a crystal phase comprising at least one kind of carbide, nitride and / or carbonitride selected from the group of metals of groups 4a, 5a and 6a of the periodic table. ˜15% by weight and inevitable impurities.

If the total content of the binding metals of cobalt (Co) and nickel (Ni) is less than 2% by weight, the amount of liquid phase generated during sintering becomes insufficient, resulting in poor sintering. If the strength of the hard metal is reduced and conversely the total content of the binder metal is more than 30% by weight, the amount of the binder metal phase occupying the cemented carbide is excessive, the hardness is lowered, and the metal working for cutting is performed. Large plastic deformation occurs when used.

Further, according to the present invention, the hardness of the cemented carbide is improved, and the metal concentrations of iron (Fe), chromium (Cr), cobalt (Co) and nickel (Ni) are set within a predetermined range. In terms of control, the periodic table 4a, 5a,
At least one carbide selected from the group of 6a group metals,
It is desirable to contain the nitride and / or carbonitride in a proportion of 30% by weight or less.

According to the present invention, iron (Fe) in cemented carbide
Content of 10 to 300ppm, chromium (Cr) content
Amount is controlled to 100-1000ppm, and super hard cement
The total content of bond metal in gold is w_{1 in}, Inside cemented carbide
The total content of iron (Fe) and chromium (Cr) is w_{2 in},
The total content of binding metals in the surface area of the cemented carbide is w_{1 suf}, Carbide
Total content of iron (Fe) and chromium (Cr) in the alloy surface area
The amount w_{2 suf}And p _in= W_{2 in}/ W_{1 in}, P_suf= W
_{2 suf}/ W_{1 suf}And p_suf<P_inSatisfy the condition of
Surface area. That is, on the surface of the cemented carbide
Iron (Fe) and chromium (Cr) for the binding metals
The content ratio of Al should be smaller than that inside the cemented carbide.
Is a major feature. This enables welding with the work material
And adhesion can be suppressed, and it is good even when forming a hard coating
It is possible to obtain a cemented carbide capable of forming a hard coating.

Here, the content of iron (Fe) in the cemented carbide cannot be industrially made lower than 10 ppm, and the content of iron (Fe) in the cemented carbide exceeds 300 ppm. As a result, welding or cohesion with the work material becomes remarkable, and the machinability deteriorates. On the other hand, the content of chromium (Cr) is 100p
If it is lower than pm, the grain growth of the tungsten carbide phase becomes remarkable, and the strength and toughness of the cemented carbide deteriorate. On the other hand, when the content of chromium (Cr) exceeds 1000 ppm, welding or adhesion with the work material becomes remarkable, and the machinability deteriorates.

In the present invention, in order to measure the contents of iron (Fe) and chromium (Cr) in the cemented carbide, the cemented carbide after sintering is ground using a cemented carbide mortar or the like. The prepared powder was dissolved by a known method to prepare an IC
It can be quantified by the method of measuring by P emission spectroscopy. In addition, these iron (Fe), chromium (Cr),
Laser ICP is used to measure the ratio of the local content of cobalt (Co) and nickel (Ni) on the surface and inside.
Mass spectrometry can be used. Further, the inside of the cemented carbide in the present invention means a region deeper than 1 mm from the surface of the cemented carbide.

Further, the maximum value of the ratio of the p _suf and p _in the surface region (p _suf / p _in), in order to improve the adhesion resistance and adhesion resistance of the cemented carbide surface, 0.5 ˜0.95, particularly 0.6 to 0.8 is desirable.

Further, the thickness of the surface region is preferably 1 to 20 μm from the viewpoints of suppressing welding and cohesion of the work material, maintaining the hardness of the surface region and preventing plastic deformation. .

The tungsten carbide phase in the cemented carbide is preferably hexagonal and has an average grain size of 0.5 to 3.0 μm. Here, the average grain size of the crystal phase such as the tungsten carbide phase in the present invention means a value obtained by the intercept method from the SEM photograph of the cemented carbide cross section.

Further, according to the present invention, carbides, nitrides, carbonitrides, TiAlN, TiZrN, TiCrN of metals of Groups 4a, 5a and 6a of the Periodic Table are formed on the surface of the cemented carbide.
It may be formed by depositing at least one hard coating film of at least one selected from the group consisting of DLC (diamond-like carbon), diamond and Al ₂ O ₃ , whereby a cemented carbide surface is formed. The hardness and wear resistance of can be remarkably improved.

Furthermore, according to the present invention, even when a hard coating is formed on the surface of the cemented carbide, the content ratio of iron (Fe) or chromium (Cr) on the surface of the cemented carbide is low, Since carbon does not decrease due to the formation of ferrite or chromium carbide, an embrittlement layer such as the η phase (W ₃ Co ₃ C, W ₆ Co ₆ C), which is a lower carbide of cobalt, is formed near the interface. A good hard coating can be formed without

The hard coating preferably has a total thickness of 1 to 30 μm in order to maintain both wear resistance and toughness, and the hard coating has a conventionally known PVD method or CV method.
It is deposited by a thin film forming method such as D method.

(Manufacturing Method) Next, a method for manufacturing the above-mentioned cemented carbide will be described. First, for example, 70 to 90% by weight of tungsten carbide powder having a content of iron (Fe) and chromium (Cr) of 0.005 to 0.1% by weight and an average particle size of 0.5 to 10 μm, and iron ( Fe) and chromium (Cr)
, Nitride and / or carbonitride powder or its solid solution powder selected from the group of metals of groups 4a, 5a and 6a of the Periodic Table, each having a content of 15 to 500 ppm and an average particle size of 0.5 to 10 μm. 0.1 to 30% by weight,
Chromium (Cr) with iron (Fe) content of 1 to 15 ppm
Content of 1 to 20 ppm and average particle size of 0.5 to 10 μ
m cobalt (Co) and / or nickel (Ni)
5 to 15% by weight, and if desired, metal tungsten (W) powder or carbon black (C) is weighed and mixed.

These mixed powders are put into a crusher having a liner made of a material not containing iron (Fe) and chromium (Cr), for example, a cemented carbide having a purity of 99.9% or more, a medium, a stirring arm, etc., After adding a dispersion medium such as alcohol, acetone or hydrocarbon and wet pulverizing for 5 to 30 hours,
Granulate to a desired particle size by a known granulation method such as spray drying. If the crushing time is shorter than 5 hours, the raw material powder cannot be sufficiently crushed and mixed, and a desired uniform surface area cannot be formed. Conversely, the grinding time is 3
If the time is longer than 0 hours, a large amount of tungsten carbide component and other impurities are mixed from the crusher to cause compositional deviation of the mixed powder.

Next, the obtained mixed powder is molded into a predetermined shape by a known molding method such as press molding, cast molding, extrusion molding, cold isostatic press molding, and then 20P.
1350 at 1 to 20 ° C / min in a non-oxidizing atmosphere of a or above
The temperature is raised to a first firing temperature of ˜1600 ° C., and then kept at the first firing temperature for 0.3 to 2 hours, especially 0.5 to 1 hour. The non-oxidizing atmosphere is, in particular, nitrogen gas (N ₂ ), helium gas (He), argon gas (A
r), a state in which an inert gas such as xenon gas (Xe) is filled or flowed.

By holding the first firing temperature for a short time in such a non-oxidizing atmosphere, a part of the binding metal composed of cobalt (Co) and / or nickel (Ni) becomes a metal liquid phase. At this time, iron (Fe) and chromium (C
r) is melted and diffused along with cobalt (Co) and nickel (Ni).

Then, 20 to 20 from the first firing temperature.
A second firing temperature lower than 0 Pa, preferably a second firing temperature lower than 10 Pa, preferably at a temperature lowering rate of 5 to 50 ° C./hour in order to optimize the distribution state of each metal in the cemented carbide. In vacuum, especially at 1200-1380 ° C for 1-3
Hold for a period of time, Co (cobalt) and / or nickel (Ni) selectively evaporates from the surface in a vacuum atmosphere, and Co (cobalt) and / or nickel (Ni) present inside selectively moves to the surface. As a result of spreading
A predetermined metal concentration gradient can be provided in the sintered body. After that, the cemented carbide of the present invention can be manufactured by cooling to room temperature.

Here, if the first firing temperature is lower than 1350 ° C., the temperature is low and an appropriate amount of liquid phase cannot be generated, and the sintered body cannot be sufficiently densified. When the first firing temperature is higher than 1600 ° C., the sintering proceeds excessively and hard particles such as tungsten carbide particles grow to reduce the toughness and strength, and at the same time cobalt (Co) in the metal liquid phase and / Or nickel (Ni) selectively evaporates from the surface in a large amount, and the metal concentration distribution on the surface cannot be within a predetermined range, and the surface becomes brittle.

The holding time at the first firing temperature is 0.
If it is shorter than 1 hour, an appropriate amount of liquid phase cannot be generated, the sintered body cannot be sufficiently densified, and conversely, the holding time at the first firing temperature is longer than 2 hours. As a result, sintering proceeds excessively to lower toughness and strength, and iron (Fe) and chromium (Cr) exceed a predetermined amount to precipitate on the surface or the surface becomes brittle.

Further, when the difference between the second firing temperature and the first firing temperature is less than 20 ° C., cobalt (Co) and nickel (Ni) with iron (Fe) and chromium (Cr).
Since there is no difference in the moving speed (diffusion speed) between and, the desired concentration distribution cannot be provided in the cemented carbide, and conversely the second
If the difference between the calcination temperature and the first calcination temperature is larger than 200 ° C., the diffusion rate of each metal is lowered as a whole, and a predetermined metal concentration gradient cannot be provided.

[0034]

EXAMPLES Iron (Fe) and chromium (C) in the amounts shown in Table 1
An inner wall made of a cemented carbide having a purity of 99.99% or more by weighing tungsten carbide (WC) powder having an average particle diameter of 9 μm, metal cobalt (Co) powder, and compound powder containing r) at a ratio shown in Table 1. , Media and an attritor mill having a stirring arm, 2-propanol was added thereto, wet pulverized for 18 hours, granulated by spray drying, and then formed into a cutting tool shape (SDK1203) by press molding.

Next, the obtained molded body was set in a vacuum sintering furnace, heated at a rate of 12 ° C./min, and held at the first firing temperature shown in Table 1 for a predetermined time, and subsequently, Table 1 After the temperature was decreased to the second baking temperature at the temperature decrease rate shown in, the temperature was maintained at the second baking temperature for a predetermined time and then cooled to room temperature. The vacuum atmosphere in the table is controlled to a degree of vacuum of 8 Pa or less, and the atmosphere of various gases (Ar, N ₂ , He) in the table is 25 P.
Controlled to state a.

The obtained cemented carbide was crushed in a mortar made of cemented carbide, and I was added to a solution prepared by dissolving this powder.
CP emission spectroscopic analysis was performed to measure the contents of iron (Fe) and chromium (Cr). In addition, the iron content of the surface of the cemented carbide and the surface ground by 1 mm or more is measured by laser ICP.
-Measured by MS. The measurement area of the laser ICP-MS was set to 10 μmφ.

[0037]

[Table 1]

Then, using the obtained cemented carbide, stainless steel was cut for 15 minutes under the following conditions (Test 1), and the flank wear amount and boundary damage amount of the cutting tool were measured. During the cutting test, the flank wear amount was 0.
When 2 mm or the boundary damage amount reached 0.5 mm, the cutting time was measured. Furthermore, the cutting edge of the tool after the cutting test was observed to confirm the presence or absence of deformation or damage. The results are shown in Table 2.

Test 1 Work Material: Stainless Steel (SUS304) Tool shape: SDKN1203AUTN Cutting speed: 200m / min Feed rate: 0.2 mm / blade Notch: 2 mm Other: Dry cutting

[0040]

[Table 2]

From the results of Table 1 and Table 2, iron (F
e) with a high content of sample No. 1 and sample No. 1 using grinding media and stainless steel as a stirring arm. Two
Then, the content of iron (Fe) in the whole cemented carbide is 300p
After exceeding pm, the hard coating was abraded during the cutting process to expose the cemented carbide, and then the wear rapidly progressed to reach the tool life. In addition, the sample No. which was baked only in the first baking temperature (single-step baking) was baked. Three
And the difference between the first firing temperature and the second firing temperature is 200
Sample No. In No. 4, the content ratio of iron (Fe) and chromium (Cr) relative to cobalt (Co) and / or nickel (Ni) on the surface was equal to or higher than the above values, and welding and adhesion of the work material were remarkable and cutting performance was improved. Fell. Further, the sample No. 1 was held in vacuum at the first firing temperature and the second firing temperature. 5 in P
_{The suf} / P _{in was} approximately 1.0, and there was no difference in the abundance ratio of (iron + chromium) and (cobalt + nickel) on the surface and inside. That is, since the amount of the embrittlement phase generated on the surface was larger than that of the invention product, the adhesion of the hard coating was reduced, and the coating peeled off during cutting. As a result, the amount of wear increased and a large amount of deposits adhered to the cutting edge of the cutting tool.

On the other hand, the sample No. 6
In all of Nos. 13 to 13, the flank wear amount was 0.2 mm (processing time / 15 min) or less and had excellent wear resistance.

(Example 2) Further, the sample No. 2, 12,
For No. 13, a hard coating having the material and thickness shown in Table 3 was formed on the surface by the PVD method, and a cutting test was performed under the same conditions as above.

[0044]

[Table 3]

As is apparent from Table 3, sample No. 2 having the base material of sample 2 having a high iron content was used. In No. 2-1, the hard coating peeled off and a large amount of the work piece was welded to the surface of the tool, whereas in the sample No. 2 according to the present invention. Sample 12 with 12 as the base material
-1, 2, 3, and sample No. In the sample 13-1 using 13 as the base material, the hard coating was not peeled off, and the work material was less welded.

The product of the present invention can be generally used as a turning tool used in a lathe, a face milling machine used in a milling machine or a machining center, an end mill, a ball end mill, a tool material for a drill and the like.

[0047]

As described in detail above, according to the cemented carbide according to claim 1, the contents of iron (Fe) and chromium (Cr) in the cemented carbide are controlled, and at the surface of the cemented carbide. By reducing the content ratio of iron (Fe) and chromium (Cr) with respect to cobalt (Co) and / or nickel (Ni) as compared with the inside of the cemented carbide, it is possible to suppress welding and adhesion with the work material, and hard coating It is possible to obtain a cemented carbide capable of depositing a good hard coating even when depositing.

According to the method for producing a cemented carbide according to claim 5, the tungsten carbide powder and the periodic table 4a,
At least one kind of carbide, nitride and / or carbonitride powder selected from the group of 5a and 6a metals and raw material powder consisting of cobalt (Co) and / or nickel (Ni) powder are pulverized and mixed to be molded. Then, in a non-oxidizing atmosphere, at a first firing temperature of 1350 to 1600 ° C., 0.3 to
Hold for 2 hours, then 20 ~
The content of iron (Fe) and chromium (Cr) in the cemented carbide is controlled because the material is cooled to a second baking temperature lower by 200 ° C. and held in a vacuum of the second baking temperature for 1 to 3 hours. In addition, the content ratio of iron (Fe) and chromium (Cr) to cobalt (Co) and / or nickel (Ni) on the surface of the cemented carbide becomes smaller than that inside the cemented carbide, resulting in a work material. Can suppress welding and adhesion with
A good hard coating can be deposited even when the hard coating is deposited.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C23C 30/00 C23C 30/00 C // B23B 27/14 B23B 27/14 BF term (reference) 3C046 FF03 FF10 FF12 FF13 FF25 FF32 FF39 FF53 FF55 4K018 AB02 AB03 AC01 AD01 BA04 DA21 DA33 KA02 KA05 KA15 4K044 AA09 AB10 BA13 BA18 BB01 BB02 BC01 CA13 CA14

Claims (6)

[Claims] 1. Cobalt (Co) and / or nickel
2 to 20% by weight of the binding metal of Ni (Ni), the 4th periodic table
at least one selected from the group of a, 5a, and 6a metals
Carbide, nitride and / or carbonitride of
10% to 300 pp of iron (Fe) in addition to the content of
m, containing 100 to 1000 ppm of chromium (Cr),
Carbide bond with the balance consisting of tungsten carbide and unavoidable impurities
In gold, near the surface of this cemented carbide,
The total content of the above-mentioned binding metals inside is w _{1 in}, This cemented carbide
The total content of iron (Fe) and chromium (Cr) inside is w
_{2 in}, The total content of said binding metal in this cemented carbide surface region
W_{1 suf}, Iron (Fe) and chromium in the surface area of this cemented carbide
The total content of ROM (Cr) is w_{2 suf}And p_in= W_{2 in}/
w_{1 in}, P_suf= W_{2 suf}/ W_{1 suf}And p_suf<P
_inCharacterized by having a surface region that satisfies the condition of
Cemented carbide. 2. The p _suf and p _{in in the} surface region
The cemented carbide according to claim 1, wherein the maximum value of the ratio (p _suf / p _in ) is _{0.5 to 0.95} . 3. The cemented carbide according to claim 1, wherein the surface region has a thickness of 1 to 20 μm. 4. The fourth periodic table on the surface of the cemented carbide.
Carbides, nitrides, carbonitrides, and Ts of a, 5a, and 6a group metals
iAlN, TiZrN, TiCrN, DLC (diamond-like carbon), at least one layer of a hard coating composed of at least one selected from the group consisting of diamond and Al ₂ O ₃ is formed to a total thickness of 1 to 30 μm. The cemented carbide according to any one of claims 1 to 3, which is characterized. 5. Tungsten carbide powder and Periodic Table No. 4
a raw material powder consisting of at least one kind of carbide, nitride and / or carbonitride powder selected from the group of a, 5a and 6a metal and cobalt (Co) and / or nickel (Ni) powder is pulverized and mixed. And then molded at a first firing temperature of 1350 to 1600 ° C. in a non-oxidizing atmosphere at 0.
Hold for 3 to 2 hours, 20 to 2 above this first firing temperature
A method for producing a cemented carbide, which comprises cooling to a second firing temperature lower by 00 ° C., and then maintaining the second firing temperature in vacuum for 1 to 3 hours. 6. A container used for pulverizing and mixing the raw material powder and a portion of the pulverizing member that comes into contact with the raw material powder are substantially free of iron (Fe) and chromium (Cr). 5. The method for producing a cemented carbide according to 5.