JPH08218145A - Cemented carbide for tool for working woody hard material - Google Patents

Abstract

PURPOSE: To develop a cemented carbide for cutting high hardness building material by mixing WC powder having specified particle size with a small amt. of Cr carbides and Co and Ni as bonding phases, compacting the same and thereafter executing sintering. CONSTITUTION: WC powder having 0.2 to 0.5μm average particle diameter and in which the ones of >=2μm are contained is added and mixed with, by weight, 0.5 to 1.5% Cr or Cr carbides and Co and Ni as bonding materials at the time of sintering in a powdery state by 1 to 2wt.% so as to regulate the ratio of Ni/(CO+Ni)<=0.3, which is compacted and is thereafter sintered at 1400 to 1450 deg.C. The cemented carbide for cutting building materials having a compsn. contg. WC with >2μm particle diameter by <=0.7% by area ratio, and the balance WC with 0.2 to 0.5μm average particle size, Cr carbides and Co and Ni as bonding phases and furthermore contg. at least one kind among hard carbon nitrides of TiCxN1-x <0.3%, TaCx N1-x +NbCx N1-x <0.5%. MoCx N1-x <0.3% and VCx N1-x <0.3% (x; 0.5 to 1) or the like and excellent in strength and wear resistance is produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cemented carbide for a tool for processing hard wood materials. More specifically, the present invention is a novel material that can be advantageously used as a material for a circular saw or the like used in cutting a hard wood-based material used for building materials, furniture, housings of home appliances, and the like. Regarding cemented carbide.

[0002]

2. Description of the Related Art Particle boats, MDFs, sizing boards and the like, which are casing materials for building materials, furniture, and home electric appliances, have been further hardened in accordance with the demand for higher quality and higher durability of final products. For this reason, conventionally used to cut or cut this kind of material,
Saw blades with brazed cemented carbide tips wear quickly and the problem is that tools are becoming shorter in service life.

Cemented carbides used for this type of application are described, for example, in Japanese Examined Patent Publication No. 63-4623.
There are materials containing 0.5-3 wt% Cr and 3-15 wt% Co.
In addition, the amount of the bound metallic phase is 5 to 8 including WC having a particle size of 1 to 3 μm.
Cemented carbide for wood cutting, which is mainly composed of wt%, is currently on the market.

However, for example, the material disclosed in Japanese Examined Patent Publication No. 63-4623 has insufficient hardness in the case of a material having a high Co content of 5 to 15 wt%, and has a wear resistance when processing high hardness wood. It is known to be significantly lower. On the other hand, a material having a low Co content of about 3 to 5 wt% has poor sinterability and low strength represented by transverse rupture strength. In addition, it has been known that commercially available cemented carbides for cutting wood have a low strength for materials having a bound metal phase content of 3 wt% or more, which can provide sufficient hardness.

[0005]

Therefore, the present invention solves the above-mentioned problems of the prior art and provides a new cemented carbide for cutting a high hardness building material capable of achieving both high strength and high wear resistance. Its purpose is to provide.

[0006]

That is, according to the present invention, Cr
And a WC grain having a grain size of 2 μm or more in a cemented carbide containing at least one of Cr carbide and WC and at least one of Co and Ni as a binding metal phase in a proportion of 1 wt% or more and 3 wt% or less. The content is 0.7% or less in the area ratio in the alloy cross-section structure, and the average grain size of WC is
There is provided a cemented carbide having a thickness of 0.2 μm or more and 0.5 μm or less.

[0007]

The main feature of the cemented carbide according to the present invention is that WC in the alloy is atomized to exhibit high toughness (flexural strength) with a very small amount of the binder metal phase.

That is, in ordinary cemented carbide, the toughness is remarkably lowered when the binder metal phase serving as a binder is reduced. Therefore, the cemented carbide with a reduced amount of the binder metal phase could not be used as a material for a practical working tool even if it was excellent in hardness. On the other hand, the cemented carbide according to the present invention has a high toughness (breaking strength) even with an extremely small amount of the binder metal phase of 3 wt% or less because the WC in the alloy is atomized to have a grain size of 0.2 to 0.5 μm. Exert. Where W
If the average particle size of C is smaller than 0.2 μm, the surface area of the WC particles is large and the thickness of the binding metal phase is insufficient, so that the transverse rupture strength is rather decreased, which is not preferable. Also, the particle size is 0.5 μ
If it is larger than m, the surface area of the WC particles is small and the thickness of the binder metal phase becomes thicker to lower the hardness, so that the original purpose of improving the wear resistance cannot be fulfilled.

Since the cemented carbide according to the present invention as described above has a small amount of binder metal phase, the presence of coarse WC grains inside the alloy causes a remarkable decrease in strength as a structural defect.
Therefore, according to a preferred embodiment of the present invention, 2 μ in the alloy is
The content of WC grains of m or more in terms of the area ratio in the alloy cross-section structure
Control to 0.7% or less. That is, if the content of coarse particles of this type exceeds 0.7%, the transverse rupture strength decreases for the reasons described above. Since the Co phase is thick in the conventional cemented carbide having a large Co content as the bonding metal phase, even if coarse grains exceeding 2 μm are contained, the stress concentration is relaxed and the strength is not substantially reduced. However, since the cemented carbide according to the present invention has a small amount of the binder metal phase, the binder metal phase cannot be expected to have the above-mentioned functions, and the presence of coarse grains is not preferable. In addition, more preferably, the content of coarse grains having a grain size of 2 μm or more is 0.3% or less in terms of the area ratio in the alloy cross-sectional structure.

In order to manufacture the cemented carbide according to the present invention as described above, it is necessary to use, as the WC raw material powder, one having a uniform particle size distribution that does not include coarse particles. Further, it is important to use a sufficiently stable carbide of bonded carbon and further suppress grain growth during sintering.

Control of the Cr content is important for suppressing grain growth. That is, Cr has an effect of improving the corrosion resistance particularly required for processing a wood-based material, and at the same time suppressing grain growth during sintering. Here, the Cr content is 0.5 wt% or more, 1.5 wt%
The following is preferred. The reason is that the Cr content is
This is because if it is 0.5 wt% or less, the grain growth inhibitor effect and the corrosion resistance improving effect do not sufficiently appear, and the corrosion resistance deteriorates when the final product is used as a working tool for wood-based hard materials. On the other hand, when the Cr content is 1.5 wt% or more, the sinterability is deteriorated and the amount of the precipitated Cr carbides is increased, which finally causes the deterioration of the transverse rupture strength and the toughness. The amount of solid solution of Cr in the bonded metal phase at room temperature is about 10% of the amount of the bonded metal phase, but with this amount, grain growth of WC during sintering cannot be completely suppressed. Therefore, it is important to set the Cr content in the above range. Further, if the Cr content is in this range, sufficient sintering can be performed at a normal sintering temperature of about 1350 to 1450 ° C, but a preferable sintering temperature is about 1400 to 1450 ° C. Furthermore, by further performing the HIP treatment after or at the same time as the sintering, it is possible to further improve the strength.

In the cemented carbide according to the present invention, the ratio of Ni and Co contained is preferably controlled so that the value of [Ni / Co + Ni] is 0.3 or less. The reason is [Ni /
This is because if the value of Co + Ni] is larger than 0.3, the sinterability deteriorates, and voids are generated in the alloy during sintering, resulting in a decrease in strength. The nest can be crushed by HIP processing,
Even if the nest is crushed in this way, it eventually remains as a binder pool, resulting in a tissue defect. Therefore, the final strength of the cemented carbide is eventually reduced, which is not preferable. Also, W
Since the intrinsic strength of C as a bonded metal phase is inferior to that of Co, Ni has a great effect on alloys having a small amount of bonded metal phase such as the cemented carbide according to the present invention. Therefore, when the corrosion resistance of the cemented carbide is unnecessary, it is preferable not to contain Ni at all. If corrosion resistance is required, [Ni / Co + Ni]
It is preferable that the value of is about 0.1 to 0.2.

Further, since the cemented carbide according to the present invention has a small amount of binder metal phase, when the content of carbides, nitrides, carbonitrides such as Ti, Mo, Ta, Nb and V increases, these alloys It segregates into coarse particles having a grain size of 3 μm or more, and these coarse particles cause stress concentration inside the alloy. Therefore, for these carbides and nitrides, TiCN is 0.3
wt% or less, Mo ₂ CN 0.3 wt% or less, TaCN + NbCN
It is preferable that 0.5 wt% or less and VCN be 0.3 wt% or less.

In particular, the carbide of V also has the effect of significantly reducing the sinterability. Therefore, in the conventional general cemented carbide, V carbide may be used as the grain growth inhibitor, but in the cemented carbide according to the present invention, the decrease in sinterability is seriously considered, and the content thereof is reduced as much as possible. It is preferable.

Hereinafter, the present invention will be described in more detail with reference to specific examples, but the following disclosure is merely an example of the present invention and does not limit the technical scope of the present invention.

[0016]

Example In order to reduce the content of WC grains having a grain size of 2 μm or more to 0.7% or less in terms of the area ratio in the sectional structure, alloys were produced by the following production steps.

First, as the raw material powder, the amount of bound carbon is 98.5% or more of the theoretical value, the W ₂ C content is as small as possible, and the peak intensity of W ₂ C (lattice plane 101) and WC (lattice plane) by X-ray diffraction are as follows. 101) A raw material powder having a ratio [W ₂ C / WC] to the peak intensity of less than 0.04 was used. Such a raw material powder was pulverized for a sufficient processing time to prepare a raw material powder to be used. Further, the mixed material was separated and the tools and containers used were thoroughly washed so that coarse WC particles were not mixed in the process.

Next, among the mixed materials, particularly Cr ₃ C ₂ and V
Precisely control the mixing amount with C, and after wet mixing for 6 hours with an attritor, after applying an appropriate sintering temperature of 1400 to 1450 ℃ and approx.
The sintering process was performed at an appropriate sintering temperature for a time. Further, the temperature in the sintering furnace was precisely controlled so that an extreme temperature distribution would not occur during the sintering process.

A plurality of samples were prepared by preparing powders having the compositions shown in Tables 1 and 2 by the above-mentioned steps, further pressing at a pressure of 1 t / cm ² and molding and then sintering. . For comparison, raw material powders under conditions outside the scope of the present invention were prepared, and comparative samples were prepared in the same process. The composition of the raw material powder of the comparative sample is also shown in Table 1 and Table 2.

[0020]

[Table 1]

[0021]

[Table 2]

The quality of the cemented carbide prepared as described above was evaluated as follows.

First, the prepared sample was used as a diamond grindstone,
After mirror-finishing with abrasive grains, etc., followed by etching with Murakami's reagent (alkali red blood salt solution), the tissue is observed with an optical microscope. Here, for example, 10 field-of-view photographs are randomly taken at a magnification of 1500, and the area A of the WC of 2 μm or more is calculated. Specifically, the WC grains having a grain size of 2 μm or more were considered to be circular, and the area of a circle having the maximum length as the diameter was obtained and approximated. On the other hand, the area of the visual field of the above-mentioned structure photograph was set as the total area B, and the area ratio C of the coarse WC grains was obtained according to the following formula 1.

[0024]

[Equation 1] C = [A / B] × 100 However, the area A is [A = π (d /
2) ² ].

Each sample of which quality was examined as described above was brazed to a cutter having an outer diameter of 180 mm, and then the side cutting edge was processed to form a saw blade having an outer diameter of 180 mm, a blade thickness of 2.4 mm, and a blade number of 1. The performance was evaluated as. The evaluation is made by using a particle board with a thickness of 25 mm as a work material, the rotation speed is 3000 rpm, and the feed rate is 0.25 m /
The processing conditions were minutes. Table 2 shows the evaluation results. The same test was also performed on the comparative sample. The evaluation results are shown in Table 3.

[0026]

[Table 3]

[0027]

[Table 4]

As shown in the tables, the samples according to the invention are
It has a high strength of HRA of 94.0 or more with a small amount of the binder metal phase of 1 to 3 wt%. Further, as can be seen from the test results, it has both strength and hardness, and achieves both high performance as a tool and long life. On the other hand, in each comparative sample, large chipping due to insufficient toughness, rapid wear due to chipping, large wear due to insufficient hardness,
This resulted in early corrosion and the like due to lack of corrosion resistance.

[0029]

As described above in detail, the cemented carbide according to the present invention has extremely excellent wear resistance and toughness.
Therefore, it can be suitably used as a material for a machining tool of wood-based hard material, which has been increasing in recent years. That is, the cemented carbide according to the present invention achieves a long life due to its high wear resistance and the occurrence of breakage due to its high toughness in such applications. Therefore, the cutting cost is significantly reduced. Furthermore, by utilizing this characteristic, it can be advantageously used for cutting and cutting of aluminum, titanium, stainless steel, Inconel, carbon and the like.

Claims (4)

[Claims] 1. At least one of Cr and Cr carbide and WC
And a cemented carbide containing 1% by weight or more and 3% by weight or less of Co and Ni as a binding metal phase, wherein the content of WC grains having a grain size of 2 μm or more is within the cross-sectional structure of the alloy. Area ratio is 0.7% or less, and the average particle size of WC is
Cemented carbide having a thickness of 0.2 μm or more and 0.5 μm or less. 2. The cemented carbide according to claim 1, wherein
A cemented carbide, wherein the binder metal phase contains Co and Ni, and the content ratio of Co and Ni is represented by the formula: [Ni / (Co + Ni) ≦ 0.3]. 3. The cemented carbide according to claim 1 or 2, wherein the Cr content is 0.5 wt% or more and 1.5 wt% or less. 4. The cemented carbide according to claim 1, wherein the content of TiC _x N is 0.3 wt% or less.
_1-X , 0.5 wt% or less TaC _x N _1-X + NbC _x N _1-X ,
Mo ₂ C _X N _1-X less than 0.3 wt% and V less than 0.3 wt%
C _x N _1-X (where, X is 0.5 or more, 1 less is) cemented carbide, characterized in that it comprises at least one as a hard phase.