JPH10237578A - Cemented carbide, its production, and cemented carbide tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a cemented carbide excellent in hardness and toughness, in which laminar WC crystalline grains are formed. SOLUTION: In the cemented carbide, at least one compound 3, composed of carbide, nitride, or carbonitride of at least one kind selected from the group IVa, Va, and VIa elements or solid solution thereof, is allowed to exist in the crystalline grains of at least a part of WC crystalline grains 1. This compound 3 is a compound consisting of carbide, nitride, or carbonitride of Ti, Zr, Hf, or W or solid solution thereof, and its average grain size is regulated to <0.3μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to tungsten carbide (hereinafter referred to as "WC") having an excellent balance between hardness and toughness used for impact-resistant tools such as cutting tools and bits, and plastic working tools such as rolls and can-making tools. ) -Based cemented carbide.

[0002]

2. Description of the Related Art Conventionally, crystal grains mainly composed of WC,
Cemented carbides composed of a binder phase mainly composed of an iron group metal such as Co or Ni have been used for various cutting tools and wear-resistant tools because of their excellent hardness, toughness, and rigidity. However, in recent years, as the uses of cemented carbides have expanded, the need for WC cemented carbides having even higher hardness and toughness has increased.

To meet such needs, Japanese Patent Laid-Open No. 2-4
In JP 7239, JP-A-2-138434, JP-A-2-27427, and JP-A-5-339659, the WC crystal grains have a plate-like shape, and have a higher hardness and hardness than the conventional cemented carbide. Proposals have been made to improve the toughness.

[0004] Japanese Patent Application Laid-Open No. Hei 5-33959 discloses that
15% or more of WC grains present in cemented carbide are 1-1
Plate-shaped W having a maximum dimension of 0 μm and twice or more the minimum dimension
One consisting of C crystal grains is disclosed. Also, JP-A-7-278719, or JP-A-8-19992
No. 85 discloses a ratio of a maximum dimension to a minimum dimension (hereinafter, referred to as an aspect ratio; that is, a cemented carbide composed of crystal grains mainly composed of WC and a binder phase mainly composed of an iron group metal is a plate-like WC crystal. In the case of containing a grain, when an arbitrary cross section of the cemented carbide is observed with a scanning electron microscope, the ratio of the maximum dimension of the individual plate-like WC crystal grains to the minimum dimension in the arbitrary cross section is referred to). And those containing plate-like WC crystal grains of 3 to 20 are disclosed.

[0005]

In the above proposal, the properties of the alloy could be improved to some extent.
Manufacturing costs have increased due to the use of special raw material powders and manufacturing methods. Further, the generation amount of the plate-like WC crystal grains was also unstable, and as a result, the alloy characteristics were unstable.

Although the toughness has been improved to some extent by the formation of these plate-like WC grains, the strength of some over-coarse plate-like WC grains is smaller than that of non-coarse WC grains. It was not necessarily high, and was a factor in increasing the variation in the strength of the cemented carbide itself. Further, when the WC crystal grains are coarsened, the alloy becomes low in hardness. Therefore, development of a WC cemented carbide having further excellent hardness and toughness has been desired.

The present invention has been made to solve the above problems. An object of the present invention is to provide a cemented carbide and a cemented carbide tool having small variations in strength and excellent in hardness and toughness.

[0008]

The cemented carbide according to the present invention comprises crystal grains mainly composed of WC and a binder phase mainly composed of iron group metal. Then, at least a part of carbides, nitrides, carbonitrides, or solid solutions thereof selected from the group IVa, Va, and VIa elements in at least a part of the WC crystal grains, which is a main component of the hard phase. There exists a compound composed of a compound other than a certain WC (hereinafter, simply referred to as “the compound” means the present compound).

The inventors of the present application have conducted various studies in order to achieve the above object, and have succeeded in producing a cemented carbide with small variation in strength and excellent hardness and toughness. Specifically, the present inventors have found that the above-mentioned compound is present in at least a part of the plate-like WC crystal grains,
It has been found that distortion occurs in the WC grains, and that this strain helps strengthen the WC grains.

Japanese Patent Application Laid-Open No. 5-850 discloses a composite hard ceramic particle in which a Ti compound is dispersed in a WC crystal grain to generate a compressive stress in the WC crystal grain.
However, although the powder produced by this method is suitable as a raw material for solid phase sintering, its effect cannot be sufficiently exhibited by liquid phase sintering as in the present invention. This is thought to be because the effect is reduced by half because the raw material is dissolved and reprecipitated during the liquid phase sintering. According to the present invention, WC crystal grains having the above-described structure can be produced at low cost during liquid phase sintering without preparing special raw materials in advance as in JP-A-5-850.
Moreover, in Japanese Patent Application Laid-Open No. 5-850, it is necessary to disperse a Ti compound having a volume ratio of 10% or more and 70% or less in order to strengthen WC crystal grains. However, strengthening of WC crystal grains became possible. Also,
The area ratio of WC crystal grains in which the compound is present in the crystal grains is preferably 10% or more of all WC crystal grain areas,
Particularly preferred is a case where it exceeds 30%.

The above-mentioned compounds are, in particular, Ti, Zr, Hf,
It is preferable to consist of a carbide, nitride, carbonitride or solid solution of W. Among them, Zr carbide, nitride or carbonitride has a great effect of improving toughness and strength.

This is a carbide of Ti, Zr, Hf, W,
Compounds composed of nitrides, carbonitrides, or solid solutions thereof are easily incorporated into WC crystal grains and easily exert the effects of the present invention. Further, the content of Ti, Zr, and Hf with respect to the entire cemented carbide is preferably 10% by weight or less. More preferably, the content is 5% by weight or less. This is because if the contents of Ti, Zr, and Hf are too large, the sinterability decreases, and the strength of the cemented carbide decreases.

The compound need not be present only in the WC crystal grains, but may be present both in the WC crystal grains and in the binder phase. The particle size of the above compound (the maximum length of a diagonal line in the case of a polygon, the maximum length of a side in the case of a triangle, and the same particle size of WC crystal grains) is 1 μm.
When it is less than m, WC crystal grains are easily strengthened, and toughness is greatly improved. Particularly preferred is a case where the particle size of the compound is 0.3 μm or less.

Further, Va, VIa in the above-mentioned cemented carbide are used.
At least one carbide or nitride selected from group III elements;
The weight percent of carbonitrides or their solid solutions is defined as Wa,
The weight percent of at least one carbide, nitride, carbonitride or solid solution thereof selected from the group IVa elements is Wb
When the value of Wa / Wb is 0 to 0.2, a particularly excellent balance between toughness and hardness is exhibited.

[0015] This is because the compounds of carbides, nitrides, carbonitrides or their solid solutions of IVa group elements such as Ti, Zr and Hf are easily incorporated into the WC crystal grains, whereas the compounds of Va, VIa group At least one kind of carbide, nitride, carbonitride or a solid solution thereof selected from the elements is hardly taken into WC crystal grains, and further has a function of suppressing WC crystal grain growth during sintering. Because. Therefore, when the value of Wa / Wb is set to 0 to 0.2, the effect of the present invention is easily exerted, so that the value is limited as described above.

For the above-mentioned reason, the content of at least one carbide, nitride, carbonitride or one solid solution selected from the group consisting of Va and VIa elements is 10% by weight based on the weight of the binder phase. %, The Va, VIa
At least one carbide or nitride selected from group III elements;
WC of compounds consisting of carbonitrides or their solid solutions
Incorporation into crystal grains is facilitated.

Next, in the cross-sectional structure of the cemented carbide, the area ratio of WC grains having a grain size of 1 μm or less is 10 to 40% of all WC grain areas, and
When the area ratio of the crystal grains is 60 to 90%, if the compound is mainly present in the WC crystal grains having a particle size exceeding 1 μm, a cemented carbide having particularly excellent hardness and toughness can be obtained.

Here, the area ratio of WC crystal grains having a particle size of 1 μm or less is limited to 10 to 40% of the area of all WC crystal grains.
%, The toughness is reduced. Also, the reason that the area ratio of WC crystal grains having a grain size exceeding 1 μm is defined as 60 to 90% is that if it is less than 60%, the toughness is reduced, and
If the content is more than 0%, the hardness is reduced.

When the compound is present in a WC crystal grain having an aspect ratio of 2 or more in the sectional structure, particularly excellent hardness and toughness are exhibited. This is because, when the WC crystal grains are coarsened into a plate shape, the decrease in hardness that normally occurs is alleviated by the presence of the compound in the WC crystal grains, the effect of improving the toughness by the coarsening, and the WC crystal. This is considered to be due to the fact that the grain strengthening became remarkable.

The toughness is particularly improved when 30% or more of the WC crystal grains having a cross-sectional structure having an aspect ratio of 2 or more among the WC crystal grains having a particle diameter of more than 1 μm are included. Normally, the hardness decreases as the aspect ratio increases to 2 or more, but when the compound is present in the grains, the decrease in hardness is suppressed. Therefore, a cemented carbide with particularly excellent toughness and hardness can be manufactured. Note that the effect of the presence of the above compound in the WC crystal grains is that the aspect ratio is 1 to 3.
We can expect even in the case of 2.

The method for manufacturing a cemented carbide according to the present invention includes the following steps. That is, the average particle size is 0.6 to 1 μm.
m of WC powder (raw material A), WC powder (raw material B) having an average particle size of at least twice that of raw material A, Co, Ni, Cr, F
e, a powder of at least one metal selected from Mo (raw material C) and at least one carbide, nitride, carbonitride or a solid solution thereof selected from IVa, Va, VIa group elements; Each having a mean particle size of 0.01 to 0.5 μm (raw material D) is used as a raw material powder, and is preferably sintered at a temperature of 1500 ° C. or higher. Thereby, the cemented carbide according to the present invention can be stably manufactured. In addition,
The average particle size of the raw materials A, B, and D may be the above value in the pulverizing and mixing steps.

In the above-mentioned method, Japanese Patent Application Laid-Open No. 2-472
39, JP-A-2-138434 and JP-A-2
There is no need to use special raw material powder as in Japanese Patent No. 274827. Further, there is no need to grind the WC powder to 0.5 μm or less as disclosed in JP-A-5-339659. Thereby, W close to the commercially available WC raw material particle size is obtained.
C powder can be used without excessive pulverization, and extraneous substances from the pulverizing / mixing device (attritor) and W
The oxidation phenomenon of the C powder can be suppressed. As a result, a cemented carbide having excellent characteristics can be stably manufactured at low cost.

The reason why the above-mentioned method can stably produce a cemented carbide containing plate-like WC grains is due to the phenomenon of dissolution and re-precipitation of WC in the liquid phase (fine grain) as a mechanism for growing plate-like WC grains. WC dissolves in the liquid phase and reprecipitates on coarse WC). The average particle size of the raw material WC powder after pulverization and mixing (also referred to as a Fischer subsieve sizer, which is an average particle size measured by an apparatus according to JIS H 2116; the same applies hereinafter) is twice or more. It is considered that the use of two types of WC powders, preferably three times or more different from each other, can also contribute. By using such two types of WC powders having different average particle diameters as raw materials, the driving force for dissolving and reprecipitating WC is improved, and plate-like WC crystal grains are easily generated. In addition, the coarse WC added as the raw material B is uniformly present in the raw material powder and acts as a seed crystal for grain growth. Thereby, local growth of plate-like WC is suppressed, and plate-like WC crystal grains can be stably generated in the sintered body regardless of a difference between a powder lot, a sintering lot, and the like.

Even in the conventional production method, uniform grinding is not performed in the grinding step due to some problems, and as a result, the WC particle size distribution is increased, thereby promoting the formation of plate-like WC crystal grains.
It has been reported that unusually coarse WC grains, called WC grains, are generated. However, since the grain size of WC on the coarse side was not controlled, stable plate-like WC crystal grains could not be generated. On the other hand, in the method according to the present invention, by controlling the mixing ratio of the raw material A and the raw material B and the average particle size difference between the raw material A and the raw material B, it is possible to control the structure of the WC crystal grains, such as the particle size distribution. Become. Further, in the method of the present invention, when a coarse grain WC having few defects and excellent properties is used as the raw material B, the WC becomes a seed crystal and grows by a dissolution and reprecipitation phenomenon. As a result, a plate-like WC having few defects and excellent characteristics can be generated like the Bridgman method which is famous in semiconductor manufacturing. Further, by using two types of WC powders having different particle sizes as described above, the raw material D is easily taken into the WC particles.

As the WC powders of the raw materials A and B, commercially available WC raw materials can be used as they are. In addition, using a powder whose particle size has been adjusted by pre-grinding (raw material A has an average particle size of 0.6 to 1 μm and raw material B has twice or more the average particle size), the powder is lightly mixed by a ball mill or the like, or mixed and crushed. In this case, two or more types of commercially available WC powders having different average particle sizes such that the target particle size is obtained may be used.

The raw material D having an average particle diameter of 0.01 to 0.5 μm or an average particle diameter of 0.01 to 0.5 μm in the pulverizing and mixing steps.
By using the raw material D having a thickness of 0.5 μm as the raw material powder, the raw material D is easily taken into the WC crystal grains at the time of dissolving and reprecipitating WC. Thereby, the cemented carbide of the present invention can be produced stably. In order to prepare a raw material having such a small average particle size, a raw material powder produced by a liquid phase synthesis method such as a sol-gel method or a gas phase synthesis method such as PVD or CVD may be used in addition to a normal pulverization method. it can. The reason why the average particle diameter of the raw material D is set to 0.01 to 0.5 μm is that it is industrially difficult to make the average particle diameter smaller than 0.01 μm.
This is because it becomes difficult to take in the crystal grains.

The weight WA of the raw material A and the weight W of the raw material B
When the ratio WA / WB of B is 0.5 to 30, a cemented carbide having particularly excellent performance can be obtained. More preferably, WA / WB is 1-10. WA / WB is 0.5
If smaller, plate-like W with aspect ratio larger than 2
It becomes difficult to generate C crystal grains. WA / WB is 30
If it is larger than this, the generation of plate-like WC crystal grains becomes unstable, and locally large plate-like WC crystal grains are likely to be generated. In addition, it becomes difficult for the compound to be taken into the WC crystal grains.

WC powder obtained by recycling used cemented carbide by at least a part of the raw material A by a recycling method (such as a zinc treatment method or a high-temperature treatment method) can be used. Thereby, not only can the cemented carbide of the present invention be manufactured at low cost, but also the useless mining of the tungsten (W) mine can be suppressed from the viewpoint of global environmental protection. Conventionally, attempts have been made to use recycled powders of cemented carbides, but at present it has been used only for a very small portion and has not been fully adopted.

Recycling is generally carried out by a zinc treatment method. However, since the particle size of the recycled WC powder depends on the WC crystal particle size of the used cemented carbide to be recycled, a WC raw material having a specific particle size cannot be produced. Even in the high-temperature treatment method, the WC crystal grains partially grow during the treatment, so that the width of the particle size distribution of the WC powder becomes extremely large even if the WC crystal is subsequently pulverized. For this reason, when a cemented carbide is manufactured using these recycled powders, the WC crystal particle size distribution cannot be controlled, and there has been a problem that the dispersion of the performance becomes large.

On the other hand, in the manufacturing method according to the present invention,
A recycled powder having a particle size range of 0.6 to 1 μm, which is regenerated from a used cemented carbide as a recycled material, is dissolved in a liquid phase in a sintering process, and re-precipitated on a material B having a larger average particle size. Let me. Thereby, the particle size of the plate-like WC crystal of the manufactured sintered body is controlled by the WC powder particle size of the raw material B. Therefore, the particle size of the recycled powder does not determine the particle size of the final sintered body, and the above-described problem can be avoided. Moreover, in the present method, the fine-grained raw material A is, as described above,
After being dissolved in the liquid phase, it precipitates on the coarse-grained raw material B, so that the characteristics of the plate-like WC depend on the characteristics of the coarse-grained raw material B. Therefore, even when using recycled materials with unstable characteristics,
A sintered body having excellent characteristics can be produced.

The weight W of the WC powder generated from the recycled powder obtained by pulverizing the used cemented carbide as the recycled material
When the ratio WR / WA of R and the weight WA of the raw material A is 0.3 to 1 (preferably 0.5 to 1), the cemented carbide of the present invention can be produced particularly inexpensively, From the viewpoint of the above, a preferable cemented carbide is obtained.

On the surface of a product such as a tool made of a cemented carbide as described above, a group IVa, Va, VIa element, Al
At least one of carbides, nitrides, oxides, borides and solid solutions thereof, or a coating film composed of at least one layer selected from diamond, DLC, and CBN. When used as a wear-resistant tool, the alloy base material exhibits particularly excellent performance because it has an excellent balance between hardness and toughness.

In particular, a coating film having a thickness of 20 μm or more is
When coated on a base cemented carbide, it is considered that the coating film promotes the generation of cracks (preliminary cracking of Griffith). Therefore, a decrease in fracture resistance of the cemented carbide was observed. However, in the cemented carbide according to the present invention, it has been found that the above compound precipitates in the WC crystal grains and the WC crystal grains are strengthened, so that crack propagation hardly occurs and excellent fracture resistance can be obtained. .

[0034]

Embodiments of the present invention will be described below with reference to FIGS. 1 and 2 and Tables 1 to 14.

(Embodiment 1) An average particle diameter of 0.7 μm crushed as a raw material powder using an attritor with high crushing efficiency.
WC powder (raw material A) and an average particle size of 2
A μm WC powder (raw material B) was prepared. Also, a CO powder having an average particle size of 1.5 μm, a Ni powder having an average particle size of 1.3 μm, a ZrC powder having an average particle size of 0.3 μm, and an average particle size of 0.5
μm TiC powder, HfC powder having an average particle size of 0.5 μm,
NbC powder with average particle size 0.3 μm, average particle size 0.4 μm
TaC powder, Cr ₃ C ₂ powder having an average particle diameter of 0.3 μm,
ZrN powder with average particle size 0.5 μm, average particle size 0.5 μm
(W, Ti) (C, N) solid solution powder, average particle size 0.5
μm (W, Zr) C solid solution powder, average particle size 0.5 μm
(Ta, Nb) C solid solution powder was added and blended into the composition shown in Table 1.
Time mixing was performed. Thereafter, granulation was performed by a spray dryer.

[0036]

[Table 1]

In Table 1 above, the raw materials No. and Wa
The numbers other than the numbers in the column of / Wb indicate wt%. Also,
Table 1 shows that at least one type of carbide, nitride, carbonitride or solid solution thereof selected from the group consisting of Va and VIa elements is represented by Wa, and at least one type of carbide selected from group IVa elements; The values of Wa / Wb when the weight% of the nitride, carbonitride or solid solution thereof is Wb are shown.

These powders are pressed using a mold at a pressure of 1 ton / cm ² , and are sintered in vacuum at 1550 ° C. for 1 hour. Thereby, the ISO model number CNMG1
A sintered body having a shape of 20408 (a diamond-shaped throw-away tip based on JIS G 4053) was produced. The sintered body is ground with a # 250 diamond grindstone, and subjected to lapping using a diamond paste.
After that, using a Vickers indenter made of diamond, 50
Fracture toughness value K _IC obtained by Indentation Fracture method obtained from hardness at kg load and crack length generated at the indentation corner of the indenter
(MPam ^1/2 ) was measured.

For comparison with the present invention, a WC powder having an average particle size of 6 μm, a Co powder having an average particle size of 1.5 μm, a Ni powder having an average particle size of 1.3 μm, and an average particle size of
μm ZrC powder, TiC powder having an average particle size of 1.5 μm,
HfC powder with an average particle size of 2 μm, NbC with an average particle size of 2 μm
Powder, TaC powder having an average particle size of 1.5 μm, average particle size of 2 μm
m, Cr ₃ C ₂ powder, ZrN powder with an average particle size of 1.5 μm, (W, Ti) (C, N) solid solution powder with an average particle size of 2 μm, (W, Zr) C solid solution with an average particle size of 1.5 μm Powder,
(Ta, Nb) C solid solution powder having an average particle size of 1.8 μm was mixed with an attritor for 7 hours, and a powder was similarly granulated. This powder was pressed using a mold at a pressure of 1 ton / cm ² , and sintered at 1400 ° C. for 1 hour in a vacuum. Then, the hardness and fracture toughness of the sintered body were measured by the same method.

Further, IVa, Va, VI
It was determined whether or not at least one compound selected from the group consisting of carbides, nitrides, carbonitrides, and solid solutions thereof was present. That is, a sample for a scanning electron microscope or a transmission electron microscope is prepared, and E
Elemental analysis was performed by DX (abbreviation of Energy dispersive X-ray Spectrometer, which is an energy dispersive X-ray fluorescence spectrometer in which a semiconductor detector is used for electrical spectroscopic selection). When Ti and C were detected, the substance was determined to be TiC. Table 2 shows the measurement results. In addition, in the sample number of Table 2, No. Nos. 1-1 to 10 show sintered bodies produced by the method according to the present invention. 2-1
Numerals 10 to 10 indicate a sintered body made of a conventional WC powder.

[0041]

[Table 2]

In Table 2, a circle indicates that the present invention is applicable. From the results shown in Table 2, the samples prepared by the method of the present invention have IVa, Va, V in the WC crystal grains.
There is at least one compound selected from the group consisting of carbides, nitrides, carbonitrides, and solid solutions thereof selected from Group Ia elements. The hardness and fracture toughness of these samples are lower than those of samples prepared by a conventional method. It turns out that it shows an excellent value.

The photograph shown in FIG. 1 is a scanning electron micrograph of Sample 1-1. In FIG. 1, the crystals that look gray and square are the WC crystal grains 1, the one that looks black is the Co phase that is the binder phase 2, and the precipitate (compound 3) that looks gray in the WC crystal grains is a carbide of Ti. is there. From this photograph, it can be seen that the particle size of the compound 3 present in the WC crystal grains 1 of the sample 1-1 is about 0.1 μm and is 0.3 μm or less. In addition, W having the above compound 3 therein
It can also be seen that the area of the compound 3 with respect to the area of the C crystal grains is 10% or less. In the present invention, the presence or absence of the compound in the WC crystal grains is determined using such a sectional structure.

Similarly, the samples of Tables 1-2 to 1-8 in Table 2 contain compounds consisting of carbides, nitrides, carbonitrides or solid solutions of Ti, Zr, Hf and W in WC crystal grains. Was confirmed to exist. 1-9, 1-10
The specimens include carbides, nitrides of Ti, Zr, Hf, W,
IVa, Va, other than carbonitrides or their solid solutions
It was confirmed that at least one kind of carbide, nitride, carbonitride or a solid solution thereof selected from Group VIa elements was present.

The characteristic values of the samples 1-1 to 1-8 are superior to those of the samples 2-1 to 2-8 according to the conventional method, and the improvement ratio is 1-9. It was also found that samples 1 to 10 of the present invention were larger than the improved values of the characteristic values of samples 2-9 to 2-10 according to the conventional method. That is, as the compound present in the WC crystal grains, a compound composed of carbides, nitrides, carbonitrides of Ti, Zr, Hf, and W or a solid solution thereof is preferable, and particularly, carbides and nitrides of Zr are WC crystal grains. It was also confirmed that Sample 1-2 existing in the sample exhibited extremely excellent alloy characteristics.

In particular, at least one carbide, nitride, carbonitride or a solid solution thereof selected from the group consisting of Va and VIa elements is defined as Wa, and at least one carbide selected from group IVa elements is used. When the weight% of the nitride, carbonitride or solid solution thereof is Wb, Wa /
It can also be confirmed that the samples 1-1 to 1-6 in which the value of Wb is in the range of 0 to 0.2 show particularly excellent characteristics as compared with the samples 2-1 to 2-6 according to the conventional method. Was.

(Embodiment 2) The raw material no. 8 and IVa, Va, TiC is carbides VIa group elements, TaC, Cr ₃ raw material amount of C ₂ differs N
o. 11 to 15 were prepared (Table 3), sintered bodies were produced in the same manner as in Embodiment 1, and the hardness and fracture toughness were measured. Table 4 shows the results. Further, the presence or absence of the compound in the WC crystal grains was examined in the same manner as in Embodiment 1, and it was confirmed that the compound was present in the WC crystal grains in all samples.

[0048]

[Table 3]

The percentages (%) in Table 3 are the percentages (%) of the contents of the carbides, nitrides, carbonitrides or solid solutions thereof (excluding WC) of the Va and VIa group elements with respect to the weight of the binder phase. is there. In addition, raw material No., ratio, and Wa / Wb
The numbers other than the numbers in the column indicate wt%.

[0050]

[Table 4]

From the results shown in Table 4, it was found that the total amount of TaC and Cr ₃ C ₂ was 10 wt% or less based on the amount of the binder phase. The alloy properties of 1-12-1-15 are excellent,
Above all, it was confirmed that Samples 1-14 and 1-15 in which the amounts of TaC and Cr ₃ C ₂ added were smaller than the amounts capable of forming a solid solution in the binder phase exhibited particularly excellent alloy properties.

(Embodiment 3) In the same manner as in Embodiment 1, raw material Nos. 16 ~
No. 23 was prepared with the composition shown in Table 5. 1 t of these powders
Pressing was performed using a mold at a pressure of on / cm ² , and sintering was performed at 1500 ° C. for 1 hour in a vacuum. Thus, a sintered body having a shape of ISO model number CNMG120408 was produced.

[0053]

[Table 5]

The raw material Nos. And numbers other than the numbers in the columns of WA / WB indicate wt%. Next, the hardness and fracture toughness of these samples were measured in the same manner as in the first embodiment. Table 6 shows the measurement results. Further, these samples were photographed at 5000 times with a scanning electron microscope after surface grinding and mirror polishing. This photograph was taken by using an image processing apparatus and the WC crystal grains having a particle size exceeding 1 μm and the
Table 6 also shows the results of classifying WC crystal grains of m or less and measuring the area ratio of each. Further, among these WC crystal grains, the area ratio of WC crystal grains having a particle diameter exceeding 1 μm and having an aspect ratio of 2 or more was measured in the same manner, and the results are also shown in Table 6. The presence or absence of ZrC, ZrN, and TiC compounds in the WC crystal grains was examined in the same manner as in the first embodiment. As a result, it was confirmed that the above compounds were present in the WC crystal grains for all samples other than 3-16 and 3-23.

[0055]

[Table 6]

From the results shown in Table 6, the samples 3-18 to 3-21 having a ratio WA / WB of the weight WA of the raw material A to the weight WB of the raw material B in the range of 0.5 to 30 have a particle diameter of 1 μm. The following W
The area ratio of C crystal grains is in the range of 10 to 40%, and has an excellent balance between hardness and fracture toughness. Among them, Samples 3-20 and 3-21 having an area ratio of 30% or more of WC crystal grains having an aspect ratio of 2 or more among WC crystal grains having a particle diameter of more than 1 μm exhibit particularly excellent alloy characteristics. It shows that it shows.

(Embodiment 4) C of Samples 1-1 to 1-10 and Samples 2-1 to 2-10 manufactured in Embodiment 1
After performing a honing treatment of 0.05R on the chip having the shape of NMG120408, a coating film shown in Table 7 was formed. Then, a cutting test was performed on the work material 4 made of SCM435 having the shape shown in FIG. 2 in which four grooves were provided in the circumferential direction of the round bar material under the following conditions, and the time until the chip was broken was measured. Table 7 shows the results. DLC in the coating film in Table 7 indicates diamond-like carbon, CVD indicates a chemical vapor deposition method, and PVD indicates a physical vapor deposition method.

[0058]

[0059]

[Table 7]

From the result of measuring the time until the loss in Table 7, the sample No. of the present invention was obtained. The tool having the coating film formed on the 1-1 to 1-5 is a sample No. of the conventional method. 2-1 to 2-5
It can be seen that the performance is superior to that of the tool having the coating film formed thereon. It should be noted that similar results could be obtained when cubic boron nitride (CBN) was used as the diamond in Table 7.
As described above, it is understood that the sample in which the coating film is formed on the cemented carbide of the present invention can exhibit excellent characteristics.

(Embodiment 5) The raw material No. 1 has the same composition as the raw material powder of No. 1 and uses a recycled WC powder obtained by treating a used cemented carbide in a part of the raw material A by a zinc treatment method or a high temperature treatment method. 24-28
(Table 8) was produced. These were sintered in the same manner as in the first embodiment, and the hardness, fracture toughness, and the presence or absence of the compound in the WC crystal grains were measured in the same manner as in the first embodiment. Table 9 shows the results.

[0062]

[Table 8]

[0063]

[Table 9]

From the results shown in Table 9, the alloy characteristics of Samples 24 to 28 using the powder recycled by the zinc treatment method and the high-temperature treatment method show the same excellent properties as Sample 1 without using the recycled powder. I understand. As described above, in the method of the present invention, a recycled powder, which was conventionally used only in a small amount due to poor alloy characteristics, can be used as a main component of the WC powder. As a result, a cemented carbide suitable for protecting the global environment can be obtained at low cost as compared with the conventional method for producing cemented carbide.

(Embodiment 6) WC powder having an average particle diameter of 0.9 μm as raw material A, WC powder having an average particle diameter of 4 μm as raw material B, Co powder having an average particle diameter of 1.5 μm as raw material C, and 1.8 μm average Using Cr powder of No. and ZrCN powder having an average particle size of 0.1 μm, 0.5 μm and 0.9 μm as the raw material D, the raw materials No. 29-32
Was prepared.

[0066]

[Table 10]

The numbers other than the numbers in the column of the raw material No. in Table 10 indicate wt%. Raw material No. Pressing and sintering were performed in the same manner as in Embodiment 1 using the powders of Nos. 29 to 32 to produce a sintered body having the shape of ISO model number CNMG120408. Next, a cutting test was performed on these samples in the same manner as in Embodiment 4 to measure the time until the samples were broken. The measurement results are shown in Table 11. In addition, these samples were photographed at 5000 times with a scanning electron microscope after surface grinding and mirror polishing, and it was confirmed that the above compound was present in WC crystal grains. Further, the composition of this compound was confirmed by EDX analysis to be a carbonitride of Zr. Further, using this photograph, an image processing apparatus was used to measure the total area of the WC crystal grains in the photograph and the area of the crystal grains in which the presence of the compound was found in the crystal grains. WC in which the above compound exists
The area ratio of the crystal grains was calculated. Table 11 shows the results.

[0068]

[Table 11]

From the results shown in Table 11, when the ZrCN powder used was a fine raw material, the area ratio of WC crystal grains in which ZrCN was incorporated into the crystal grains was increased, and the WC crystal in which the above compound was present in the crystal grains was used. It can be seen that as the area ratio of the grains increases, the fracture resistance improves. Above all, it was confirmed that when the area ratio of the WC crystal grains in which the above compound was present in the crystal grains exceeded 10%, the chipping resistance was rapidly improved.

(Embodiment 7) Powders having the composition shown in Table 12 were mixed for 2 hours in an acetone solvent by a ball mill. Thereafter, the powder is dried, and
Pressing using a mold at a pressure of n / cm ² ,
Sintering was performed at a temperature of 500 ° C. for 1 hour. Accordingly, the same sintered body No. CNMG120408 as in the first embodiment. 3-4 to 3-6 were produced. It should be noted that the presence of the compounds shown in Table 13 in the WC crystal grains of these sintered bodies was confirmed by transmission electron microscopy with EDX or XDX.
It was confirmed by performing a line qualitative analysis. Next, the hardness and fracture toughness of these samples were measured in the same manner as in the first embodiment. Table 14 shows the results.

[0071]

[Table 12]

[0072]

[Table 13]

[0073]

[Table 14]

From the results shown in Table 14, it can be seen that Sample No. in which the Zr compound was precipitated in the WC crystal grains. The sample of 3-4 to 3-6 is T
Sample No. i in which compound i precipitated in the WC crystal grains. 3-1
It was confirmed that the sample had a better balance between hardness and fracture toughness than the sample of 3-3. Further, the sintered body is subjected to surface grinding and outer periphery grinding, and further subjected to a honing process of 0.05R, and then 0.5 μm TiN and 5 μm T
iCN, 3 μm TiC, 2 μm alumina, 0.5 μm T
An iN coating film was coated by a CVD method. Using these samples, the work material used in Embodiment 4 was cut under the following conditions, and the time until breakage was measured. Table 14 shows the results.

[0075] From the results described in Table 14, Sample No. in which the Zr compound was precipitated in the WC crystal grains. Sample Nos. 3-4 to 3-6 are Sample Nos. In which the Ti compound precipitated in the WC crystal grains. 3-1 to 3-
It was confirmed that the sample of Example 3 exhibited more excellent fracture resistance.

[0076]

As described above, according to the present invention,
At least one selected from the group consisting of IVa, Va, and VIa elements
By forming a compound consisting of a kind of carbide, nitride, carbonitride or a solid solution thereof in the WC crystal grains, a WC crystal having excellent strength is obtained.
This is remarkable when the crystal grains are plate-like. As a result, a cemented carbide having excellent strength and toughness can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram (copy) showing a scanning electron micrograph of a cemented carbide.

FIG. 2 is a diagram showing a cross-sectional shape of a work material used in a cutting test.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 WC crystal grain 2 Bound phase 3 Compound 4 Work material

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI C22C 29/08 C22C 29/08 // B22F 1/00 B22F 1/00 Q C23C 14/00 C23C 14/00 Z

Claims (16)

[Claims] 1. A cemented carbide comprising a crystal grain mainly composed of tungsten carbide (WC) and a binder phase mainly composed of an iron group metal, wherein at least a part of the tungsten carbide crystal grains contains a group IVa, Va, VIa. A cemented carbide comprising at least one kind of carbide, nitride, carbonitride or a solid solution thereof other than tungsten carbide selected from elements. 2. The cross-sectional structure of the cemented carbide according to claim 1, wherein the area of the compound is 10% or less of the area of the tungsten carbide crystal grains having the compound therein. Cemented carbide. 3. A sectional structure of the cemented carbide, wherein an area ratio of the tungsten carbide crystal grains in which the compound is present in crystal grains is 10% or more of an area of all the tungsten carbide crystal grains. The cemented carbide according to claim 1 or 2, characterized in that: 4. The compound according to claim 1, wherein the compound is at least one of titanium (Ti), zirconium (Zr), hafnium (Hf), and tungsten (W) carbides, nitrides, carbonitrides, and solid solutions thereof. The cemented carbide according to any one of claims 1 to 3, wherein the cemented carbide is made of a material other than tungsten. 5. The cemented carbide according to claim 1, wherein the compound comprises at least one of carbide, nitride and carbonitride of zirconium (Zr). 6. The super-compound according to claim 1, wherein the presence of the compound is recognized in the tungsten carbide crystal grains having a cross-sectional structure having an aspect ratio of 2 or more. Hard alloy. 7. The cemented carbide according to claim 1, wherein the compound has an average particle size of less than 0.3 μm. 8. The weight percent of a compound consisting of at least one carbide, nitride, carbonitride or a solid solution thereof other than tungsten carbide selected from the group consisting of Va and VIa elements is defined as Wa and IVa. At least one carbide, nitride, carbonitride or a solid solution thereof selected from the group consisting of group-element elements and tungsten (W), and a solid solution thereof other than the above-mentioned tungsten carbide, where Wb is represented by Wb, The cemented carbide according to any one of claims 1 to 6, wherein the value of / Wb is 0 to 0.2. 9. The content of at least one kind of carbide, nitride, carbonitride or solid solution thereof selected from the group consisting of Va and VIa group elements other than the tungsten carbide is selected from the group consisting of: 10% by weight
The cemented carbide according to any one of claims 1 to 6, characterized in that: 10. In the sectional structure of the cemented carbide, the area ratio of the tungsten carbide crystal grains having a grain size of 1 μm or less is 10 to 10% of the area of all the tungsten carbide crystal grains.
8. The method according to claim 1, wherein an area ratio of the tungsten carbide crystal grains having a grain size of more than 1 μm at 40% is 60 to 90% of all the tungsten carbide crystal grain areas. 9. The cemented carbide described. 11. A tungsten carbide crystal grain having a grain size of more than 1 μm containing at least 30% of grains having an aspect ratio of 2 or more in a sectional structure.
The cemented carbide according to claim 10. 12. A tungsten carbide (WC) powder (raw material A) having an average particle diameter of 0.6 to 1 μm, and a tungsten carbide powder (raw material B) having an average particle diameter twice or more that of the raw material A.
And cobalt (Co), nickel (Ni), chromium (C
r), a powder of at least one metal selected from iron (Fe) and molybdenum (Mo) (raw material C), and an average particle size of 0.01 to 0.5 μm, which is selected from the group IVa, Va and VIa elements. A method for producing a cemented carbide, comprising using, as a raw material powder, at least one selected carbide, nitride, carbonitride or a solid solution thereof and a raw material D other than the tungsten carbide. . 13. The weight WA of the raw material A and the raw material B
The method for manufacturing a cemented carbide according to claim 12, wherein the ratio WA / WB of the weight WB of the cemented carbide is 0.5 to 30. 14. The method for producing a cemented carbide according to claim 12, wherein a recycled powder of a cemented carbide is used as at least a part of the raw material A. 15. The method according to claim 14, wherein a ratio WR / WA of a weight WR of the tungsten carbide powder generated by grinding the recycled powder to a weight WA of the raw material A is 0.3 to 1. A method for producing the cemented carbide described in the above. 16. A tool made of the cemented carbide according to claim 1, wherein the tool surface is made of IVa, Va, VI.
at least one carbide selected from group a elements and Al;
Nitrides, oxides, borides, their solid solutions, or diamond, diamond-like carbon (DL
C) A carbide tool provided with a coating film comprising at least one layer of cubic boron nitride (CBN).