JPH07179980A - High strength tungsten carbide-based cemented carbide - Google Patents

Abstract

PURPOSE:To produce a WC-based cemented carbide having high strength by specifying the particle diameter of a multiple metal oxide when a bonding phase contg. the multiple metal oxide dispersed in the matrix of a Co-based alloy is blended with WC having a prescribed average particle diameter in a specified ratio to obtain a WC-based cemented carbide. CONSTITUTION:When a WC-based cemented carbide is composed of 4-25wt.% bonding phase having a structure contg. a multiple metal oxide dispersed and distributed in the matrix of an alloy based on Co or Co-Ni and the balance WC having <=0.7mum average particle diameter, the particle diameter of the multiple metal oxide is reduced to <=10mum. The objective WC-based cemented carbide having very high strength is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tungsten carbide (hereinafter referred to as WC) based cemented carbide having a high strength and exhibiting excellent performance especially when used as various cutting tools and wear resistant tools. It is about.

[0002]

2. Description of the Related Art Conventionally, as described in, for example, Japanese Patent Laid-Open No. 61-12847, a Co-based alloy or Co-Ni is used.
A WC-based superstructure consisting of WC containing 4 to 25% by weight of a binder phase having a structure in which a composite metal oxide is dispersed and distributed in the base alloy base, and the rest having an average particle size of 0.7 μm or less. Hard alloys are known. In addition, the conventional W
A C-based cemented carbide is used to form a green compact having a predetermined composition.
(A) In a vacuum, after being kept at a temperature above the liquid phase appearance temperature for a predetermined time, it is sintered under the conditions of furnace cooling (cooling rate: about 20 ° C / min), (b) and then the resulting sintered body is , Using Ar as a pressure medium, temperature: above the liquid phase appearance temperature, pressure: 15
It is also known to be produced by HIPing under conditions of 0 MPa or less.

[0003]

On the other hand, in recent years, for example, cutting and metal plastic working have been remarkably speeded up and labor-saving, and along with this, cutting tools such as drills and miniature drills, end mills and throwaway tips, Furthermore, even higher strength is required for wear-resistant tools such as guide rolls and mand mills of metal plastic working equipment, but the conventional WC-based cemented carbide described above has considerably high strength, but it is still not sufficient. Therefore, under the present circumstances, it is not always possible to satisfy these requirements.

[0004]

Therefore, the present inventors have
From the above viewpoints, the above-mentioned conventional WC-based cemented carbide was paid attention to, and as a result of research to further improve the strength of the WC-based cemented carbide, the above-mentioned conventional manufacturing conditions were applied to the production of the WC-based cemented carbide. On the other hand, first, in the sintering step, the cooling from the sintering temperature is accelerated, preferably at a cooling rate of 30 ° C./min or more, and in the HIP processing step, the temperature is relatively lowered to obtain a liquid phase. In addition to the appearance temperature or less, the pressure is increased to 200 MPa or more, and 2 in Ar of the pressure medium.
Under the condition of containing oxygen of about 0 to 40 ppm, in the above-mentioned conventional WC-based cemented carbide, the particle size of the composite metal oxide dispersed and distributed in the base material of the binder phase is 20 to 300 μm over a wide range. What was obtained was the result of research that the existing WC-based cemented carbides had a grain size of 10 μm or less, and the resulting WC-based cemented carbides exhibited even higher strength.

The present invention has been made on the basis of the above research results, and occupies the whole binder phase having a structure in which a composite metal oxide is dispersed and distributed in a base material of a Co-based alloy or a Co-Ni-based alloy. In a proportion of 4 to 25% by weight,
A WC-based cemented carbide consisting of WC having an average grain size of 0.7 μm or less, characterized by a high-strength WC-based cemented carbide obtained by refining the grain size of the composite metal oxide to 10 μm or less. Is.

In the WC-based cemented carbide of the present invention, the content ratio of the binder phase is set to 4 to 25% by weight. If the ratio is less than 4% by weight, sufficient sinterability cannot be secured. This is because the desired strength and toughness cannot be obtained, and if the proportion exceeds 25% by weight, the wear resistance will decrease. Further, the average particle size of WC of 0.7 μm or less is formed, for example, by solid solution containing Cr and / or V in the binder phase. In this case, when the average particle size exceeds 0.7 μm,
Even if the particle size of the composite metal oxide is reduced to 10 μm or less, the desired high strength cannot be ensured, so the average particle size is set to 0.7 μm or less. Furthermore, the largest diameter of the composite metal oxide of the binder phase is usually the starting point of fracture, and therefore the smaller the particle size, the higher the strength. Diameter is 1
When it exceeds 0 μm, the particle diameter suddenly decreases and it is impossible to secure a desired high strength. Therefore, the particle size of the composite metal oxide is set to 10 μm or less.

[0007]

EXAMPLES Next, the WC-based cemented carbide of the present invention will be specifically described by way of examples. As raw material powders, WC powders each having an average particle size in the range of 0.3 to 0.9 μm, Cr ₃ C ₂ powders, VC powders, Co which also have an average particle size in the range of 0.3 to 5 μm Powders and Ni powders were prepared, these raw material powders were blended to the blending composition shown in Table 1, mixed for 72 hours in a wet ball mill, dried under reduced pressure, and then pressed powders A to I at a pressure of 1 ton / cm ^2. Then, the WC-based cemented carbides 1 to 11 of the present invention and the conventional WC-based cemented carbides 1 to 11 were obtained by press-molding into a compact and then sintering and HIPing the green compact under the conditions shown in Tables 2 and 3. Each was manufactured.

Then, with respect to various WC-based cemented carbides obtained as a result, a bending test was carried out for the purpose of evaluating strength, and bending strength was measured. Further, the fracture surface after the bending test was observed with a scanning electron microscope, and the particle size of the composite metal oxide that was the starting point of the fracture on the fracture surface was measured. The results of these measurements are shown in Table 4. Table 4 also shows the average particle size of WC.

[0009]

[Table 1]

[0010]

[Table 2]

[0011]

[Table 3]

[0012]

[Table 4]

[0013]

From the results shown in Tables 1 to 4, the present invention W is obtained.
C-based cemented carbides 1 to 11 all have a composite metal oxide particle size of 10 μm or less, and thus exhibit extremely high strength, whereas conventional WC-based cemented carbides 1 to 11
It is clear that the particle size of the composite metal oxide is distributed over a wide range of 20 to 300 μm and exhibits relatively low strength. As described above, since the WC-based cemented carbide of the present invention has extremely high strength, when it is used as, for example, a cutting tool or a wear resistant tool, it has excellent performance even under application under severe conditions. It has an industrially useful effect such that it exerts a remarkable effect over a long period of time.

Claims (1)

[Claims] 1. A Co-based alloy or a Co-Ni-based alloy base contains 4 to 25% by weight of a binder phase having a structure in which a composite metal oxide is dispersed and distributed, and the rest is 0.7 μm. A high-strength tungsten carbide-based cemented carbide having the following average grain diameter, wherein the grain size of the above-mentioned composite metal oxide is refined to 10 μm or less.