JP3303187B2 - Method for producing tungsten carbide based cemented carbide having high strength - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a tungsten carbide-based cemented carbide (hereinafter referred to as "ultra-hard"), in which Co as a binder phase forming component is distributed with good dispersibility over the entire structure, thereby providing high strength. Hard alloy).

[0002]

2. Description of the Related Art Conventionally, cemented carbide generally uses tungsten carbide (hereinafter referred to as WC) powder and Co powder having a predetermined particle size as a raw material powder, and further contains Cr and V if necessary. (Hereinafter referred to as Cr ₃ C ₂ and VC, respectively) powder and oxide (hereinafter referred to as Cr ₂ O ₃ and V ₂ O ₅ ) powder,
And carbides of Ti, Ta, Zr, and Nb as heat-resistant carbide powders (hereinafter, TiC, TaC, Zr, respectively)
C, and NbC), and these raw powders are blended in a predetermined composition, mixed, and then sintered by ordinary powder metallurgy to produce a cemented carbide. % By weight (hereinafter,% indicates% by weight), Co: 2 to 20%, and if necessary, (a) Cr and / or V: 0.1 to 2%, (b) Heat-resistant carbide composed of one or more of TiC, TaC, ZrC, and NbC: 0.1 to
2% or more of one or both of (a) and (b), the remainder having a composition consisting of WC as an indispensable phase-forming component and unavoidable impurities, and having a binder phase of C
o or Co containing Cr and / or V as a solid solution
A base alloy, a Co base alloy having a structure in which the heat resistant carbide is dispersed and distributed in a base of Co, or a structure in which the heat resistant carbide is dispersed and distributed in a base of a Co base alloy containing solid solution of Cr and / or V It is also well known that the cemented carbide is made of a Co-based alloy having the following formulas. Also, it is well known that these cemented carbides are practically used as cutting tools and wear-resistant tools.

[0003]

On the other hand, in recent years, high-speed and high-precision cutting and plastic working have been remarkable.
Along with this, it is presently required that the cutting tools and wear-resistant tools made of cemented carbide used for them have further improved strength.

[0004]

Means for Solving the Problems Accordingly, the present inventors have
In view of the above, in order to produce a cemented carbide having high strength, as a result of conducting research with particular attention to the production of the above-mentioned conventional cemented carbide, the WC in the production of the above-mentioned conventional cemented carbide was basically WC. A metal tungsten (hereinafter, referred to as W) powder having an average particle size of 1 to 5 μm, which has been previously blended in a predetermined ratio instead of a mixed powder composed of a powder and a Co powder; Although it has a particle size, cobalt oxide (hereinafter referred to as Co _x O _y ) powder and carbon (C) powder, which are relatively fine compared to the average particle size of the W powder, a) One of the above heat-resistant carbide powders
Seed or two or more, and (b) Cr ₃ C ₂ powder, VC
Powder, Cr ₂ O ₃ powder, and V ₂ O ₅ powder
WC / Co composite powder obtained by subjecting a mixed powder consisting of one or more of one or more of these (a) and (b), or both, to a reduction treatment in a reducing or inert gas atmosphere And a WC / Co-based alloy composite powder, ie, a WC powder, a Co layer or Co
Of a Co-based alloy layer having a structure in which the heat-resistant carbide is dispersed and distributed in the base material, a Co-based alloy layer containing Cr and / or V in a solid solution, or a Co-based alloy containing Cr and / or V in a solid solution. A WC / Co composite powder and a WC / Co-based alloy composite powder obtained by completely or partially fusing a Co-based alloy layer having a structure in which the heat-resistant carbide is dispersed and distributed on a base material are used as raw material powders. When sintering from powder by ordinary powder metallurgy to produce cemented carbide,
The cemented carbide produced has, in particular, C as a binder phase forming component.
Since o was distributed with good dispersibility over the entire structure, a research result was obtained that the steel had higher strength as compared with the cemented carbide manufactured by the above-mentioned conventional method. .

The present invention has been made on the basis of the above research results, and as a raw material powder, W powder having an average particle diameter of 1 to 5 μm, and all of them have an average particle diameter of 0.1 to 1 μm. Is one of Co _x O _y powder and carbon powder and, if necessary, one of TiC powder, TaC powder, ZrC powder, and NbC powder which are relatively fine compared to the average particle diameter of the W powder. A heat-resistant carbide powder composed of one or more kinds, a Cr ₃ C ₂ powder, a Cr ₂ O ₃ powder,
Using one or more of VC powder and V ₂ O ₅ , these raw material powders are (a) Co _x O _y powder:
6-25%, carbon powder: 0.5-4%, W powder: remaining,
(B) Co _x O _y powder: 6 to 25
%, Carbon powder: 0.5 to 4%, heat-resistant carbide powder composed of one or more of TiC powder, TaC powder, ZrC powder, and NbC powder: 0.1 to 2%, W
Powder: the remaining composition, (c) Co _x O _y powder: 6 to 25%, carbon powder: 0.5 to 4%, Cr ₃ C ₂
Powder, Cr ₂ O ₃ powder, VC powder, and V ₂ O ₅ powder one or more of: 0.1 to 2.5%, W powder: rest, consisting of blending composition, (d) Co _x O _y powder: 6-25%, carbon powder: 0.5 to 4% TiC powder, TaC powder, ZrC powder, and NbC refractory carbide powder consisting of one or more of the powder: 0.
1 to 2%, Cr ₃ C ₂ powder, Cr ₂ O ₃ powder, VC powder, and V ₂ O ₅ powder one or more of:
0.1 to 2.5%, W powder: the remaining composition, consisting of
After blending into any one of the above compositions (a) to (d) and mixing, the mixture is reduced in a reducing or inert gas atmosphere to contain Co: 5 to 20%. Accordingly, (A) a heat-resistant carbide composed of one or more of TiC, TaC, ZrC, and NbC: 0.
1-2%, (B) Cr and / or V: 0.1-2
% Or more of (A) and / or (B), the remainder having a composition of WC and unavoidable impurities, and the heat-resistant carbide on a surface of WC powder on a Co layer or a base material of Co. A Co-based alloy layer having a structure distributed and distributed,
A Co-based alloy layer containing Cr and / or V in a solid solution or a Co-based alloy layer having a structure in which the heat-resistant carbide is dispersed and distributed on a Co-based alloy containing Cr and / or V in a solid solution Or partially or fused
A raw powder is formed from the WC / Co composite powder and the WC / Co-based alloy composite powder, and the WC / Co composite powder and the WC / Co-based alloy composite powder are formed by a usual powder metallurgy method.
Excellent Co dispersibility on the structure as a binder phase forming component,
The method is characterized by the method for producing a cemented carbide having high strength.

Next, the reason why the manufacturing conditions are limited as described above in the method of the present invention will be described. (A) Average particle diameter of raw material powder The average particle diameter of the W powder is set to 1 to 5 μm. If the average particle diameter is less than 1 μm, the creep deformation resistance of the manufactured cemented carbide decreases. On the other hand, the average particle size is 5μ.
When the value exceeds m, the strength of the manufactured cemented carbide rapidly decreases. Also, C
o _x O _y powder having an average particle diameter was a 0.1~1μm a is
Even if the average particle diameter is less than 0.1 μm, no effect on the reduction reaction is exhibited, and it is not economical in terms of pulverization. On the other hand, if the average particle diameter exceeds 1 μm, unreduced Co _x O _y becomes For this reason, cavities are generated in the cemented carbide, and the desired high strength cannot be secured. Further, the average particle size of the carbon powder is determined from the viewpoint of reducibility, and a carbon powder having a similar particle size is used for the reduction of Co _x O _y powder having an average particle size of 0.1 to 1 μm. If the average particle size is less than 0.1 μm, the reduction reaction is strong and the presence of residual carbon is unavoidable, while if the average particle size exceeds 1 μm, the reduction reaction becomes slow and Co _x O _y is because so remains. Similarly, the average particle size of the heat-resistant carbide powder is 0.1
When the average particle size is less than 0.1 μm, it is not economical in terms of pulverization. On the other hand, when the average particle size exceeds 1 μm, the strength of the cemented carbide decreases. It is because it becomes. In addition, Cr ₃ C
₂ powder, Cr ₂ O ₃ powder, VC powder, and V ₂ O ₅ powder are solid-dissolved in Co, which is a binder phase forming component, by reduction treatment to form a base material of a Co-based alloy, and the strength of the binder phase is obtained. And for the purpose of improving the heat resistance, it is blended as necessary, but the average particle size of this is 0.1 to 1 μm is that the average particle size is less than 0.1 μm It is not economical in terms of grain refinement. On the other hand, if the average grain size exceeds 1 μm, solid solution in Co may not be completely performed, in which case the strength of cemented carbide decreases. This is for the reason.

(B) Blending composition and component composition_xO_yIf the mixing ratio of the powder is less than 6%,
Generated WC / Co composite powder and WC / Co alloy composite
The Co content in the composite powder is less than 5%
When using this to produce cemented carbide, the desired strength
Can not be secured, while the compounding ratio is 25%
If it exceeds, the Co content of the similarly manufactured cemented carbide is 2
It will increase more than 0%, and the wear resistance will decrease
In addition to humming, the dispersibility of Co in cemented carbide is low.
Lowering the strength is inevitable,_xO_ypowder
The mixing ratio of the powder is 6-25%, the WC / Co composite powder and
The Co content ratio in the WC / Co alloy composite powder is 5 to 2
It was set at 0%. Also, the mixing ratio of the carbon powder:
0.5-4% is Co_xO_yMixing ratio of powder: 6 to 25
%, And Cr added if necessary_TwoO_ThreePowder and
And / or V_TwoO _FiveDetermined according to the mixing ratio of powder
Therefore, the desired blending ratio of Co_xO_ypowder
End or Co_xO_yPowder and Cr_TwoO_ThreePowder and / or
Or V_TwoO_FivePowders with no residual carbon, Co or
Is the compounding ratio of carbon powder required for reduction to Co-based alloy
Is set to 0.5 to 4%. Furthermore, heat resistance
Mixing ratio of carbide powder and WC / C of heat-resistant carbide
o The content ratio in the alloy composite powder was set to 0.1 to 2%.
If the ratio is less than 0.1%, the desired heat resistance is secured
Can not be performed, while if the ratio exceeds 2%, carbide
Due to the fact that the strength of the alloy will decrease
It is. In addition, Cr_ThreeC_TwoPowder, Cr_TwoO_ThreePowder, VC
Powder, and V_TwoO_FiveRegarding the mixing ratio of powder,
If the mixing ratio is less than 0.1%, the Cr in the Co-based alloy
And / or the content of V is 0.1% of the whole.
And the strength and resistance of the binder phase
No improvement effect is obtained in the heat property, while the compounding ratio is 2.5
%, The Cr and / or Co in the Co-based alloy base material
The content of V is also higher than 2% in the whole.
Become too hard and reduce the strength of cemented carbide
From 0.1 to 2.5% of the Co-based alloy
0.1 to 2% Cr and / or V content in the ground
It was decided. The reduction in the method of the present invention
Processing is employed in the reduction of normal metal oxide powder
Conditions, that is, in a reducing atmosphere such as a hydrogen stream, or
Is in an inert gas atmosphere such as a nitrogen stream or an Ar stream,
Performed at 800-1100 ° C for 1-5 hours
You.

[0008]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
Explain physically. As raw material powders,
W powder with the average particle size shown, Co _xO_yPowder, charcoal
Element (C) powder, TiC powder, TaC powder, ZrC powder,
NbC powder, Cr_ThreeC_TwoPowder, Cr_TwoO_ThreePowder, VC powder
End, and V_TwoO_FivePrepare powders and mix them
Finally, a ball mill was added to the composition shown in Tables 1-4.
After wet-mixing for 72 hours and drying, shown in Tables 4-6
Components under the same conditions as shown in Tables 5 to 7
WC / Co composite powder with composition and WC / Co matrix
Forming a gold composite powder, followed by these WC / Co composite powders
Powder and WC / Co-based alloy composite powder,
n / cm^Two Pressing into a green compact with the pressure of
The body is placed in a vacuum atmosphere at a temperature in the range of 1350-1450 ° C.
Sintering is carried out at a predetermined temperature for 1 hour, and then the temperature is:
1320 ° C, pressure: 900 kgf / cm^Two , Retention time:
The method of the present invention by performing the HIP treatment under the condition of 1 hour
1 to 42, 8 mm x 4
Cemented carbide with a bending strength test specimen shape of mm × 25mm
Each was manufactured.

For the purpose of comparison, WC powder, Co powder, TiC powder, TaC powder, ZrC powder, NbC powder, and Cr ₃ C ₂ powder having the average particle diameters shown in Tables 8 to 10 are used as raw material powders. , And VC powder, and these raw material powders are blended in the same composition as shown in Tables 8 to 10 (corresponding to the compositions of the cemented carbides manufactured by the present invention methods 1 to 42, respectively), and then subjected to a ball mill for 72 hours. After wet-mixing and drying, the mixed powder is pressed into a green compact under the same conditions as in the methods 1 to 42 of the present invention, sintered, and further subjected to a HIP treatment to obtain a conventional method. 1 to 42 were performed to produce cemented carbides having the same component composition as the compounding composition. With respect to various types of cemented carbides obtained as a result, bending strength was measured, and the measurement results are shown in Tables 4 to 9, respectively.

[0010]

[Table 1]

[0011]

[Table 2]

[0012]

[Table 3]

[0013]

[Table 4]

[0014]

[Table 5]

[0015]

[Table 6]

[0016]

[Table 7]

[0017]

[Table 8]

[0018]

[Table 9]

[0019]

[Table 10]

[0020]

According to the results shown in Tables 5 to 10, in the methods 1 to 42 of the present invention, the structure in which the heat-resistant carbide is dispersed and distributed on the surface of the WC powder as the raw material powder or on the Co layer or on the base material of Co. Having a structure in which heat-resistant carbides are dispersed and distributed in a Co-based alloy layer having a solid solution containing Cr and / or V or a Co-based alloy layer having a solid solution containing Cr and / or V. By using a WC / Co composite powder and a WC / Co-based alloy composite powder having a structure in which a Co-based alloy layer is entirely or partially fused, conventional methods 1-42 using a mixed powder of element powders are used.
In this case, a cemented carbide in which the dispersibility of Co as a binder phase forming component is further improved as compared with the cemented carbide produced by the method described above, and the improvement in the dispersibility of Co makes each bending strength It is clear from the relative comparison that the strength is remarkably improved. As described above, according to the method of the present invention, a cemented carbide having high strength can be manufactured, and therefore, the requirements for cutting tools and various types of wear tools to which the cemented carbide is applied can be sufficiently satisfied. You can do it.

Continued on the front page (72) Inventor Shinichi Sekiya 1511 Furamagi, Ishishita-cho, Yuki-gun, Ibaraki Pref. Mitsubishi Materials Corporation Tsukuba Works (58) Field surveyed (Int. Cl. ⁷ , DB name) B22F 1/00 B22F 1/02 C22C 1/05

Claims (4)

(57) [Claims] 1. As a raw material powder, a metal tungsten powder having an average particle size of 1 to 5 μm, each of which is 0.1 to 1 μm.
m, but using a cobalt oxide powder and a carbon powder which are relatively finer than the metal tungsten powder.
In this case, cobalt oxide powder: 6 to 25%, carbon powder: 0.5 to 4%, metal tungsten powder: remaining, are blended into a blended composition, mixed, and then reduced in a reducing or inert gas atmosphere. Co: 5 to 20%, tungsten carbide and unavoidable impurities: remaining, having a composition consisting of:
The tungsten carbide / Co composite powder is formed by completely or partially fusing the layers to form a tungsten carbide / Co composite powder.
o A method for producing a tungsten carbide-based cemented carbide having high strength, comprising producing a tungsten carbide-based cemented carbide from a composite powder by an ordinary powder metallurgy method. 2. As a raw material powder, a metal tungsten powder having an average particle size of 1 to 5 μm,
one or more of cobalt oxide powder, Cr and V carbide powder and oxide powder having an average particle size of m, but relatively finer than the metal tungsten powder.
Or more, and using carbon powder, these raw material powders are each represented by weight%, cobalt oxide powder: 6 to 25%, one of Cr and V carbide powder and oxide powder.
Species or two or more: 0.1 to 2.5%, Carbon powder: 0.5 to 4%, Metal tungsten powder: Remaining, blended into a blended composition, mixed, and then reduced or inert gas atmosphere In a reduction treatment, Co: 5 to 20%, Cr and / or V: 0.1 to 2%, tungsten carbide and unavoidable impurities: remaining, having a composition consisting of: Cr
And / or a Co-based alloy layer containing V as a solid solution is entirely or partially fused to form a tungsten carbide / Co-based alloy composite powder. A method for producing a tungsten carbide-based cemented carbide having high strength, characterized by producing a tungsten carbide-based cemented carbide by metallurgy. 3. As a raw material powder, a metal tungsten powder having an average particle diameter of 1 to 5 μm, each of which is 0.1 to 1 μm.
m, but relatively fine particles of cobalt oxide powder, Ti, T
one or two of carbide powders of a, Zr and Nb
Using a heat-resistant carbide powder composed of at least one or more kinds of carbon powders, and using these raw material powders in the following weight%, cobalt oxide powder: 6 to 25%, one of carbide powders of Ti, Ta, Zr and Nb. Heat-resistant carbide powder consisting of one or more species: 0.1 to 2
%, Carbon powder: 0.5 to 4%, metal tungsten powder: remaining, blended into a composition consisting of, mixed and then reduced in a reducing or inert gas atmosphere, Co: 5 to 20% , Ti, Ta, Zr and Nb, having a composition consisting of one or more of heat-resistant carbides of 0.1 to 2%, tungsten carbide and unavoidable impurities: remaining, and tungsten carbide Co on the surface of the powder
Forming a tungsten carbide / Co-based alloy composite powder obtained by completely or partially fusing a Co-based alloy layer having a structure in which the heat-resistant carbide is dispersed and distributed on the base material; A method for producing a tungsten carbide-based cemented carbide having high strength, comprising producing a tungsten carbide-based cemented carbide from a composite powder by an ordinary powder metallurgy method. 4. As a raw material powder, a metal tungsten powder having an average particle size of 1 to 5 μm,
m, but relatively finer than the tungsten carbide powder, such as cobalt oxide powder, Ti, T
one or two of carbide powders of a, Zr and Nb
One or more of heat-resistant carbide powder, carbide powder and oxide powder of Cr and V,
And carbon powder. These raw material powders are each expressed by weight%. Cobalt oxide powder: 6 to 25%, heat resistance comprising one or more of carbide powders of Ti, Ta, Zr and Nb Carbide powder: 0.1-2
%, One of Cr and V carbide powder and oxide powder
Species or two or more: 0.1 to 2.5%, Carbon powder: 0.5 to 4%, Metal tungsten powder: Remaining, blended into a blended composition, mixed, and then reduced or inert gas atmosphere Co: 5 to 20%, heat-resistant carbide composed of one or more of Ti, Ta, Zr and Nb carbides: 0.1 to 2%, Cr and / or V : 0.1 to 2%, tungsten carbide and inevitable impurities: remaining, and having a composition of:
And / or a tungsten carbide / Co-based alloy composite in which a Co-based alloy layer having a structure in which the heat-resistant carbide is dispersed and distributed is completely or partially fused to a Co-based alloy base containing V as a solid solution. A method for producing a tungsten carbide-based cemented carbide having high strength, comprising forming a powder and producing a tungsten carbide-based cemented carbide from the tungsten carbide / Co-based alloy composite powder by ordinary powder metallurgy.