JPS60110838A - Sintered hard alloy and its production - Google Patents

Abstract

PURPOSE:To produce a sintered hard alloy having excellent wear resistance and toughness by compounding WC, TiC, TaC or TaNbC powder as a hard phase and a ferrous metal as a bond phase at a specific ratio and sintering the same then incorporating an adequate amt. of N therein. CONSTITUTION:55-75vol% WC powder, 15-35% TiC powder and 5-25% TaC or TaNbC powder are compounded as a hard phase and further 10-18% Fe group metallic powder as a bond metal is compounded therewith and after the mixture is molded under pressure, the molding is sintered in a vacuum. The sintered body after sintering is cooled in a nitrogen atmosphere. The sintered body is cooled at a rate of >=30 deg.C/min in the range from the sintering temp. up to 1,100 deg.C during the course of cooling. The sintered hard alloy which is constituted of the hard phase consisting of WC and BI type solid soln. and the bond phase consisting of the Fe group metal and contains N in the range of x+y<=1, 0.005<=y<=0.05 when the compsn. of the hard phase is expressed by (WTiTaNb) (CxNy) is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field The present invention relates to a cemented carbide for cutting tools having significantly degraded wear resistance and toughness.

(b) Background of the Invention In the field of J-cutting using cemented carbide tools, what is required to realize highly efficient cutting is that J: Copper wear 1 in the conventional sawing process. What is more important is to develop a tool that is capable of higher feed rates (1if) and is less likely to chip. Translating these into the physical properties of tools, we need to develop a cemented carbide that is harder and has higher toughness. However, it is generally said that if you try to improve one of these two physical properties, the other will decrease.
1” has contrary properties.

For example, when increasing the amount of Bl-type solid solution (hereinafter referred to as γ phase) containing carbides such as Tic to increase wear resistance, this γ41] is more brittle than W Toughness decreases because L is poor in wettability 1, and even if Ii of the binder metal phase such as Go is decreased in order to improve +r1+t φ wear f1:, toughness decreases.

As described above, it has been extremely difficult to achieve both wear resistance and toughness with the conventional 71fl hard alloy.

(c) 111 yen of the invention The present invention overcomes all such difficulties and achieves 1ijJ'
) The object of the present invention is to provide a cemented carbide whose wear resistance and VJ resistance are improved by 11-1.

The details of how the present inventors came to complete the present invention are as follows:
I'll tell you two. One way to improve wear resistance is to reduce the amount of binder metal phase such as Cod compared to conventional cemented carbide, but this alone will reduce toughness and cause wear resistance. It is not possible to achieve both toughness and toughness. Therefore, in order to improve wear resistance, we decided to increase the amount of γ phase, and we thought that the decrease in toughness caused by this could be overcome by finely dispersing the γ phase into the structure of the cemented carbide. Thought.

In addition, if it is possible to increase the wear resistance by increasing the amount of γ (11) without reducing the toughness, C.

We thought that even if the amount of the binder metal phase was increased compared to the conventional one, the toughness could be improved while maintaining the improvement in the wear resistance of the cemented carbide as a whole.

As a means for refining the γ phase, a method of adding nitrogen in the form of a cemented carbide +1 bow, for example, TiN, T1CN, (TiW) (CN), etc. is known. (Unexamined Japanese Patent Publication No. 55
-91953) On the other hand, when a nitrogen-containing cemented carbide is sintered in a vacuum,
The γ phase disappears near the surface of the sintered body due to the nitrogen decomposition reaction,
It is known that a WC-Co layer (hereinafter referred to as a γ-degraded phase) having a lower hardness than the inner layer is formed, and that this layer exhibits excellent performance when used as an IJ layer in a coating layer. (Special Publication No. 57-393.01) However, there is a big problem when using cemented carbide with a degamma layer as a cutting tool without coating it. In order to reduce manufacturing costs, the dimensional accuracy of the sintered body has been improved.
This is because products whose sides are not polished off are widely used, and the γ-removal layer on this surface significantly deteriorates their wear resistance.

Therefore, in the present invention, in order to develop a cemented carbide alloy in which the γ phase is made finer by adding nitrogen to the cemented carbide alloy, and the wear resistance does not deteriorate due to the formation of deγ1. Prototypes are made by changing the composition, manufacturing method, etc.
As a result of repeating the l'ilJ performance, the present invention has been completely contradicted.
0I'll tell you about it.

First, limitations on nitrogen-containing 4H, H and cooling conditions after sintering will be described. Deγ2 removal using cemented carbide with high nitrogen content
As a method to prevent 111 from becoming raw, there is a method of sintering it in a reduced pressure nitrogen atmosphere and a method of sintering it in a microwave plasma nitrogen atmosphere (Japanese Patent Application Laid-Open No. 58-25404).
However, these methods are difficult to control at the current stage, and it is difficult to mass-produce products with stable performance.

Therefore, the present inventors searched for a method that would prevent the entire degamma phase from occurring without relying on complex and delicate atmosphere control during the sintering process, as described in the article, and obtained the following knowledge. be.

In other words, the amount of nitrogen is limited to a low amount that makes it difficult for nitrogen decomposition to occur, and nitrogen gas is applied before and after the cooling process of the sintered body to suppress nitrogen decomposition from the surface of the sintered body. It was discovered that it was possible to obtain cemented carbide that had undergone nitrogen decomposition.

According to the ω1 study conducted by the present inventors, when the y value described in claim 1 is less than 0005, the amount of nitrogen becomes γ
1" is not effective in refining the γ phase, and if the y value is 0.05 or more, the effect in refining the γ phase is sufficient. However, when vacuum sintering is performed, nitrogen decomposition reactions occur on the surface of the sintered body. When used as a cutting tool without polishing the surface, the wear resistance i11: is significantly reduced. (I11j%11
In order to further enhance the effect of quantity, it is desirable that the y value is 0.03 or less.

As for the cooling conditions, AJ+, which is cooling in a nitrogen atmosphere as mentioned above, is desirable, but especially from the sintering temperature
Rapid cooling at a rate of 30°C/min or higher from down to 0°C makes it possible to suppress grain growth of crystals, and if the grain size of the raw material WC is coarsened, the tough WC becomes coarser and the brittle γ phase becomes finer. The toughness of the cemented carbide increases significantly.

Next, regarding the reason for limiting the hard phase composition, first of all, WC is 55
Body ("s") If the volume is less than 15%, the toughness is poor, and if the volume is more than 75%, the wear resistance is poor.
Body 4i'? If it is less than 351%, the wear resistance will be poor, and if it is less than 351%, the toughness will be poor. TaC Saitaba 1
- If aN I) C is less than 5 volume percent, the toughness is poor, and if it is 25 volume percent or more, the wear resistance is poor. In order to further enhance the effects of the present invention, the hard phase composition should preferably be 11% (%, 55<WC<68 20<'l"ic <337 (TaC or TaNbC (20%).

Next, when the bonding metal 4'll hk is less than 10 volume percent, the toughness is inferior, and when it is 18 volume percent or more, the abrasion resistance is inferior.

Demonstrates excellent performance. − Examples of the present invention will be described below.

Example All raw material powders were weighed to have the carbide composition shown in Figure 1 and the composition shown in Table 1, wet-pulverized with alcohol in an attrike, and then dried. Paraffin I M Fi percentage was added to the mixed powder. 2000Kg by adding
Hat-shaped at a pressure of /c++I. This was done in a vacuum for 140 minutes.
After simultaneous sintering at 0°C, cooling by the method shown in Table 1,
A series of cemented carbides were obtained.

1st table umbrella 1) LQ cut rN+'1 (near rice Ll+ cut)
Nami Iu5Ch1435 ll5-88 100W×3
0OLB II Force, 7ter 1r160φ, AR=8°
, RR-0', CA=+5゜70-1 way tip blade No. 1 5PU422 single blade test L cutting speed 111
20III/g, Depth of cut, 7JA5, Feed 02/blade, Cutting time: 30 minutes 2) Cutting strips The results are shown in Table 1, and it is clear that the alloy A of the present invention is extremely superior. In addition, it is possible to simultaneously improve the wear resistance and toughness of conventional cemented carbide, which were two older sisters, and when used as a cutting tool, the J adhesive and chipping of the tool are drastically reduced, resulting in a long tool life and high performance. This will earn you trust.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the hard phase composition range of the present invention alloy and the hard phase composition of the example alloy. Agent Patent Attorney: Tetsuji II

Claims (1)

[Claims] (Hard phase consisting of W C and B I 2a solid solution and Fe
In a cemented carbide composed of a bonding phase of the group metal, hard r'! phase set) ak (W 7ri Ta Nb
) (Cx Ny) 11j", wc is 55% or more in volume%, near 5% or less, 1"ic 15% or more"
2. 35% or less, TaC or TaNbC is 5% or more, 25% or less, x -1-y≦1.0.0056y
≦+1.05, and the 1.1 characteristic is that the bonding metal contains 10% by volume or more and 18% by volume or less of nitrogen. (2) WC, TiC, l'aC or TaNbC
powder with a WC of 55% or more by volume as a hard phase 75
% or less, TiC from 15% to 35%, TaC or TaNbC from 5% to 25%, and Fe group metal powder as a binding metal of 10% by volume or more.
2 1818 volumes, blended, molded, sintered, and after sintered, nitrogen ',! The hardness of the final alloy (W
TiTaNb)(CxNy) is a method for producing a cemented carbide containing nitrogen in the range of tx+y≦10.005≦y≦0.05.