JPH0978158A - Production of superfine wc base cemented carbide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce superfine WC base cemented carbide excellent in deflective strength by mixing WC powder with Co powder and at least one kind of Cr3 C2 powder and VC powder, compacting the same and thereafter performing sintering. SOLUTION: A powdery mixture composed of 4 to 20wt.% Co powder obtd. by reducing Co2 O3 and having 0.3 to 0.8μm average particle size and in which the value of the ratio of the X-ray diffraction intensity [f.c.c (101)] in the (101) plane having a face centred rhombohedral structure to the X-ray diffraction intensity [h.c.p (200)] in the X-ray diffraction intensity in the (200) plane having a hexagonal close-packed structure, i.e., f.c.c. (101)/h.c.p (200) is regulated to the range of 0.2 to 0.35, one or two kinds of hard Cr3 C2 powder and VC powder having 0.1 to 1μm average particle size by 0.1 to 2.0wt.% in total, and the balance superhard WC powder having 0.3 to 1.0μm average particle size is subjected to wet mixing, which is thereafter dried. This powder is compacted to be formed into a green compact, which is thereafter sintered in a vacuum heating furnace and is successively subjected to hot hydrostatic pressing to produce the superfine WC base cemented carbide.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a fine-grained WC-based cemented carbide having excellent transverse rupture strength. The fine-grained WC-based cemented carbide produced by this method is particularly suitable for punching a printed circuit board. It can be applied to miniature drills and slitters for cutting tape.

[0002]

2. Description of the Related Art Conventionally, for a miniature drill for punching a printed circuit board, a slitter for cutting a tape, etc., Co powder, Cr ₃ C ₂ powder, VC powder, WC powder, Co powder: 4 ~ 20 wt%, Cr ₃ C
One or two of ₂ powders and VC powders: 0.1
2.0% by weight, with the balance being WC powder,
The fine WC-based cemented carbide is manufactured by mixing and compacting the green compact and sintering the obtained green compact, and the fine WC-based cemented carbide is ground into a predetermined shape and finished. Well known.

[0003]

However, in recent years, further cost reduction by high-efficiency cutting has been demanded, and miniature drills and tape slitters are no exception, and are used under more severe conditions than before. However, there is a demand for miniature drills and tape slitters that do not break even when used under such severe conditions.

[0004]

Therefore, the inventors of the present invention have excellent transverse rupture strength for providing a miniature drill and a tape slitter having a longer service life without breaking even when cutting under such severe conditions. In order to obtain a fine WC-based cemented carbide, the transverse rupture strength of the fine WC-based cemented carbide is significantly affected by the crystal structure and grain size of the Co powder, which is the raw material powder. Face-centered cubic structure (1
01) plane X-ray diffraction intensity [hereinafter, f. c. c (101)
X] X-ray diffraction intensity of the (200) plane of the dense hexagonal structure [h. c. p (200)] ratio: f.
c. c (101) / h. c. Although p (200) was 0.4 or more in the past, this ratio was set to be smaller than that in the conventional case.
When Co powder having a particle size of more than 2 and not more than 0.35 and having an average particle size of 0.3 to 0.8 μm is used, fine WC-based super fine particles having more excellent transverse rupture strength than conventional ones are used. We have found that a hard alloy can be obtained.

The present invention has been made on the basis of such knowledge, and Co powder: 4 to 20% by weight, Cr ₃ C
One or two of ₂ powders and VC powders: 0.1
By blending so as to have a blending composition containing 2.0% by weight and the rest being WC powder, mixing, press-molding to produce a green compact, and sintering the obtained green compact. Fine W
In the method for producing a C-based cemented carbide, the Co powder is 0.2 <f. c. c (101) / h. c. p (20
0) ≦ 0.35 and the average particle size: 0.3-0.
The method is characterized by a method for producing fine WC-based cemented carbide that is Co powder that satisfies the condition of 8 μm.

F of Co powder used in the method for producing fine WC-based cemented carbide of the present invention. c. c (101) / h. c.
The value of p (200) is set to more than 0.2 and not more than 0.35 because if it is not more than 0.2, the sinterability deteriorates and the strength of the fine WC-based cemented carbide becomes insufficient, which is not preferable. ,on the other hand,
If it is larger than 0.35, the grindability is poor. F. c. C of c structure
This is because undesirably, since the amount of o increases and the pulverizability decreases, the dispersion of Co deteriorates, and the strength and wear resistance are insufficient.

The average particle size of the Co powder used in the method for producing the fine WC-based cemented carbide of the present invention is 0.3 to 0.8.
The value of μm is not preferable if it is less than 0.3 because the particle size is too small and the dispersion of Co deteriorates, resulting in insufficient strength and wear resistance of the fine WC-based cemented carbide. 8μ
If it is larger than m, the particle size is large and the pulverizability is poor, so that the dispersion of Co is poor and the strength and wear resistance are insufficient, which is unfavorable.

0.2 <f. c. c (101) / h.
c. p (200) ≦ 0.35 and particle size: 0.
The Co powder satisfying the condition of 3 to 0.8 μm can be produced by heating cobalt oxide at 350 to 450 ° C. for 5 to 20 minutes to reduce it.

Thus obtained 0.2 <f. c.
c (101) / h. c. When using a Co powder having p (200) ≦ 0.35 and an average particle size of 0.3 to 0.8 μm, one or two of Cr ₃ C ₂ powder and VC powder mixed with the Co powder are used. The average particle size of the seeds is preferably 0.1 to 1 μm, and the average particle size of the WC powder is 0.3 to
It is preferably 1.0 μm.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Cobalt oxide is reduced under the conditions shown in Table 1 and pulverized to obtain the average particle size shown in Table 1 and f. c. c (101) / h. c. Co powders aj having a ratio of p (200) were produced. This f. c. c
(101) / h. c. The ratio of p (200) was determined by X-ray diffraction measured using Cu as a target.

[0011]

[Table 1] * Is a value outside the present invention

To the Co powders a to j shown in Table 1, WC powder, Cr ₃ C ₂ powder and VC powder having the average particle size shown in Table 2 were added so as to have the composition shown in Table 2. Were blended together, wet mixed with a ball mill for 72 hours, and dried. After that, the green compact is press-molded at a pressure of 1 t / cm ² , and the green compact is charged into a vacuum heating furnace, and 1350 to 1
Sintering is performed at a predetermined temperature within the range of 500 ° C., and the obtained sintered body is pressure: 900 kg / cm ² , temperature: 1320 ° C.
By applying HIP treatment in accordance with the present invention, the method for producing the fine WC-based cemented carbide of the present invention (hereinafter referred to as the method of the present invention) 1 to 9 and the conventional method of producing the fine WC-based cemented carbide (hereinafter referred to as the conventional method). 1 to 3 were carried out to prepare a round bar bending test piece having a diameter of 3 mm. After measuring the bending strength using these round bar bending test pieces, the Rockwell hardness (HRA) was measured,
Table 2 shows the measurement results.

[0013]

[Table 2]

[0014]

From the results shown in Table 2, the method of the present invention 1 to
The fine WC-based cemented carbide round bar bending test pieces obtained in No. 9 had a Rockwell hardness (compared to the fine WC-based cemented carbide round bar bending test pieces obtained by the conventional methods 1 to 3). HRA)
Are almost the same, but have excellent transverse rupture strength, and miniature drills, tape slitters, etc. made by using the fine WC-based cemented carbide produced by the production method of the present invention are cut under more severe conditions. Also, the cutting life can be maintained for a long time without breaking, which is an industrially excellent effect.

Claims (2)

[Claims] 1. Co powder: 4 to 20% by weight, Cr ₃ C ₂
One or two of powder and VC powder: 0.1
It is mixed with a composition containing 2.0% by weight and the rest is WC powder, mixed and press-molded to produce a green compact, and the obtained green compact is sintered to obtain a fine WC-based powder. In the method for producing a hard alloy, the Co powder is an X-ray diffraction intensity [hereinafter referred to as f. c. c) (101)] and the X-ray diffraction intensity of the (200) plane of the dense hexagonal structure [h.
c. p (200)] is 0.2 <f. c. c
(101) / h. c. A method for producing a fine-grained WC-based cemented carbide, which is a Co powder satisfying the condition of p (200) ≦ 0.35 and having an average particle diameter of 0.3 to 0.8 μm. 2. The average particle diameter of one or two of the Cr ₃ C ₂ powder and the VC powder is 0.1 to 1 μm,
The method for producing fine WC-based cemented carbide according to claim 1, wherein the WC powder has an average particle size of 0.3 to 1.0 µm.