JP2000345206A - Method for heat treating cemented carbide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for heat treating a cemented carbide excellent in wear resistance and deflective strength. SOLUTION: A WC-Co cemented carbide or a cemented carbide in which at least a part of WC is substituted with the carbide of transition metals such as TiC, TaC, NbC and HfC or the double carbide thereof (incudig WC) and the average free path of the bonding phase is >=0.3 μ is cooled from the temp. within the range of 1,000 to 1,500 deg.C to <=200 deg.C at a cooling rate of >=30 deg.C/min in a reducing or inert atmosphere or in vacuum.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat treatment of a sintered alloy having improved performance by dissolving a carbide element in a binder phase in a non-equilibrium manner in a cemented carbide used for cutting tools, abrasive tools and the like. It is about the law.

[0002]

2. Description of the Related Art FIG. 1 shows an equilibrium diagram of a WC-Co-based cemented carbide, which is a typical example of cemented carbide. Now, for example, considering an alloy having a composition of WC-6 ^W / _O Co, at 1400 ° C., the composition indicated by C in the figure (52% Co-48
% WC) liquid

[0003]

(Equation 1)

And WC

[0005]

(Equation 2)

[0006] There is a ratio of: Under normal cooling (about 5-10 ° C / min) from this state, the solubility in the liquid phase will be
Decreases along G and WC precipitation occurs. When the eutectic point G is reached (1320 ° C.), the WC solidifies as a eutectic composed of Co containing approximately 20% WC and fine WC. When the temperature further decreases, WC is precipitated and equilibrium is cooled along DE.

[0007]

However, the cemented carbide obtained by the conventional technique has insufficient mechanical strength such as abrasion resistance and bending strength.

Accordingly, it is a primary object of the present invention to provide a heat treatment method capable of obtaining a cemented carbide having excellent wear resistance and bending strength.

[0009]

According to the present invention, quenching is carried out from the state of C in FIG. The purpose is to obtain an alloy having excellent mechanical strength.

As will be described in the following embodiments, this effect
Not all cemented carbides realize this, but the carbide grain size and the amount of binder phase, ie the mean free path of the binder phase (mean
free path) and 0.3
It was found to be effective in alloys having a mean free path of ~ 0.4μ or more.

The cooling rate is usually determined in sintering.
It has been found that a cooling rate of 30 ° C./min or more is effective against 5 to 10 ° C./min. This will also be described in Examples.

The present invention is applicable not only to a WC-Co simple alloy but also to an alloy in which part or all of WC is replaced with a carbide of a transition metal such as TiC, TaC, NbC, HfC or a double carbide thereof (including WC). It is valid.

The binder phase is also effective for iron group metals such as Ni and Fe besides Co. The advantage of these carbides being dissolved in supersaturation in the binder phase is that alloying is expected to improve wear resistance, corrosion resistance, oxidation resistance, heat resistance, etc. It can also be used for stable production of non-magnetic alloys due to the decrease of the Curie point due to the formation.

[0014]

Embodiments of the present invention will be described below. Tables 1 and 2 show the characteristic values and effects when alloys of various compositions were treated by the ordinary method and the present method. FIG. 2 is a graph summarizing the decrease in the saturation magnetization due to rapid cooling in relation to the mean free path.

[0015]

[Table 1]

[0016]

[Table 2]

When the mean free path is 0.3-0.4 μm or more, a clear decrease in the saturation magnetization is observed. The measurement results of the lattice constant of the binder phase also indicate that the mean free path is 0.3 to 0.4 μm or more, and the expansion of the interplanar distance is shown. It can be seen that the penetration of WC is effective at 0.3 to 0.4 μm or more. Some samples were treated at a cooling rate of 20 ° C / min, but no rapid cooling effect was observed.

[0018]

[Effects of the Invention] The effect of the present method is that the wear resistance is improved because WC is dissolved in a supersaturated solid solution, and in the high cobalt alloy, the bending strength is also increased due to the strengthening of the binder phase. . Also, it has been clarified that there is a negative correlation between the conventional alloy C value and the WC solid solution amount, and as shown in the TC value of Table 1, the C value of the present method is no different from the ordinary method. It is clear that this is due to the effect of the cooling rate. It is very difficult to lower the alloy C value on an industrial scale in order to dissolve a large amount of WC, and in this method, a cemented carbide with an enhanced binder phase is industrially stabilized by increasing the cooling rate in this method. It was a success. In the above embodiment, the cooling rate during sintering of the cemented carbide was controlled, but it can be achieved by controlling the cooling rate after re-heating after sintering.

[Brief description of the drawings]

FIG. 1 is a WC-Co-based parallel state diagram.

Fig. 2 Mean free route of saturated magnetic field and coupled phase (mean fr
ee path).

Claims (1)

[Claims] 1. A WC-Co based cemented carbide or a cemented carbide in which at least a part of WC is replaced by a transition metal carbide such as TiC, TaC, NbC, HfC or a double carbide thereof (including WC), A cemented carbide having a binder phase having an average free path of at least 0.3 μm is cooled at a cooling rate of at least 30 ° C./min from a temperature in the range of 1000 ° C. to 1500 ° C. in a reducing or inert atmosphere or vacuum. A heat treatment method for a cemented carbide, characterized by cooling to a temperature of not more than ℃.