JPH0266136A - Wc-co sintered hard alloy and its manufacture - Google Patents

Abstract

PURPOSE:To manufacture the title alloy having high strength and high toughness by sintering WC-Co sintered hard alloy powder, thereafter subjecting it to carburizing treatment and specifying the relationship between the amt. of solid solution W and the amt. of solid solution C in a bonding phase. CONSTITUTION:The powder of a WC-Co sintered hard alloy is charged to a mold, is heated in an inert atmosphere or in vacuum and is sintered. The sintered body is then subjected to carburizing treatment to regulate the relationship between the amt.(x)(atom%) of solid solution W and the amt.(y) of solid solution C in a bonding phase of the alloy in such a manner that the formulae of (x)+5(y)-18>0, 3<=(x)<=8 and (y)<=4 are satisfied. In this way, the amt. of solid solution W and the amt. of solid solution C are increased, so that the alloy having high hardness and high toughness can be manufactured by simple treatment. The alloy is applicable to a cutting tool, drawing die, die material, etc.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a cemented carbide that has high hardness and good wear resistance at room temperature and high temperature, and a method for manufacturing the same, such as cutting tools, wire drawing dies, Applied to mold material.

(Prior Art) In general, WC-Co cemented carbide has high hardness and good wear resistance and stockability even at room temperature to high temperature.

The hardness and toughness (transverse rupture strength) of WC-Co-based cemented carbide vary depending on the amount of the binder phase.For example, if the Co content of this cemented carbide is 5 at. )When,
Hardness 1600 (Hv), transverse rupture strength + 50 (kgf/
mm"), and when the Co content is 25%, the hardness is 950 () Iv) and the transverse rupture strength is 270 (kgf/mm")
If the amount of 1 in the binder phase is large, the hardness will be low and the transverse rupture strength will be high, whereas if the amount of the binder phase is small, the hardness will be high and the transverse rupture strength will be low.

Further, it is known that hardness, transverse rupture strength, etc. are influenced by the amount of solidly dissolved C in the binder phase of cemented carbide and the amount of solidly dissolved W poison. That is, as the solid solution Wi increases, the solid solution Cf amount decreases, and as a result, the hardness of the binder phase increases, so the hardness of the alloy increases and the transverse rupture strength decreases. On the contrary, as the solid solution Cm increases, the solid solution Wm decreases, and as a result, the hardness of the binder phase decreases, so the hardness of the alloy decreases and the transverse rupture strength increases.

It has been conventionally known that as the hardness of the binder phase increases, the transverse rupture strength of the cemented carbide decreases. this is,
This is thought to be because the hardness increases as the amount of solid solution of W increases.

(Problems to be Solved by the Invention) However, in cemented carbide made by the conventional sintering method, as shown in Fig. 1, the amount of solid solute C in the binder phase and the solid solute w
1 is controlled by the phase equilibrium during sintering, solute WN
Since increasing the amount of solid solute C decreases, it has been quite difficult to produce a cemented carbide with high hardness and high toughness in which both the solute W poison and the solid solute C1 content are increased.

The present inventors analyzed and investigated the relationship between the hardness and transverse rupture strength of WC-Co-based cemented carbide and the amount of solid solute CgL and solid solute W in the crystal phase, and as a result, the solid solute Wi was kept constant. It has been found that by increasing the solid solution C content, the alloy hardness increases and the transverse rupture strength improves.

An object of the present invention is to obtain a WC-Co cemented carbide having high hardness and high toughness and a method for producing the same.

(Means for Solving the Problems) The cemented carbide of the first aspect of the present invention has solid solution Wfflx (atomic %) and solid solution CNy (
It is characterized in that the relational expression of x+5y-18>0 3≦X≦8 y≦4.

A second aspect of the present invention is characterized in that the WC-Co based cemented carbide powder is sintered in an inert atmosphere or in a vacuum, and then the cemented carbide is produced by carburizing treatment.

The relational expression between the solid solution w1X (atomic %) and the solid solute Cf amount y (atomic %) in the binder phase of the cemented carbide in the present invention is 1! ; Reason 1 limited as stated above is as follows.

■ The reason for setting x+5y-18>0 is that by increasing both solid solution Cvl and solid r8 W IJ't compared to conventional W C-Co cemented carbide, C (interstitial type) with a different solid solution form is set. and W (replacement 4
;2) This is to promote solid solution hardening.

■ The reason for setting X≦8 is that when x>8, a brittle phase appears, the transverse rupture strength becomes low, and embrittlement becomes severe.

■ The reason why we set 3≦x and y≦4 is that if :S > x, the toughness decreases significantly, and if y>4, the play i! l1lC precipitates, and then -LlI! J! This is because it is difficult to change.

In the range of the ratio of X and y mentioned above, the same solid solution W
By increasing the amount of solid solution C1;1 in [;t, a cemented carbide with high hardness and high transverse rupture strength can be obtained.

As the carburizing treatment in the second aspect of the present invention, it is preferable to use air carburizing or plasma carburizing for j'.

Plasma carburizing is particularly excellent in terms of processing time, Chl control accuracy, and the like.

As the carburizing treatment conditions, the treatment temperature is set to less than 1280°C. This is 5 when the processing temperature is 1280℃ or higher.
This is because depending on the composition, a liquid phase is generated and the solid volume wH also changes. Furthermore, if the carburizing temperature is too low, the solid solubility limit of C will decrease, so it is desirable that the carburizing temperature is about 1200° C. or higher.

The amount of carburization is preferably set to be below the solid solubility limit at the processing temperature, for example, about 3.5% at a processing temperature of 1200°C and about 4% at 1270°C. This is because C is generated and the transverse rupture strength is significantly reduced. Note that it is preferable to cool quickly after carburizing in order to prevent precipitation of C.

(Example) Examples of the present invention will be described.

The manufacturing method of cemented carbide is to mix C powder with highly pure W powder with a particle size of about 0.1 to 05 μm to create fine WC powder.
Add fine powder of CO to this powder. These powders are thoroughly mixed, put into a mold, pressed together at about 1,000 atmospheres, and then heated in a reducing atmosphere at 1,350 to 1,500°C or in a vacuum. Then, the Co is melted and the WC powder is sintered.

From this sintered cemented carbide, the length, width, and height are 4.4.50 mm.
A test piece was prepared. Test pieces of this cemented carbide were subjected to vacuum carburization (Example 2) and plasma carburization (Example 2) to produce test pieces.

Solid solution Cm and solid solution Wffl in the binder phase of these test pieces were measured using an X-ray microanalyzer.

The sintering conditions were 1370°C for 1 hour.

The test results were as shown in Table 1.

(Hereinafter, blank space) In Table 1, the vacuum carburizing conditions of Example 1 are 10-"
After reducing the pressure to Lorr, it was heated to 1270°C, held for 10 minutes, C3HIl gas was introduced, and the pressure in the heating furnace was reduced to 350°C.
Lorr and carburized for 30 minutes.

The plasma carburizing conditions of Example 2 were as follows: IO-”tor
After reducing the pressure to Apply a DC voltage of 5 minutes, perform glow discharge for 5 minutes, then exhaust the
, gas was introduced, the pressure was set at 2 torr, and glow discharge was performed for 15 minutes.

In Comparative Example 3, carburization was not performed after sintering.

As is clear from Table 1, Example 1 compared to Comparative Example 3.
and 2 are solid solution C1 while keeping solid solution Wffi the same
In Examples 1 and 2, both hardness and transverse rupture strength are higher than in Comparative Example 3, which is not carburized.
It was found that it had a high toughness value.

(Effects of the Invention) As explained above, according to the present invention, both the solid solution wH and the solid solution CH of the WC-Co cemented carbide are replaced by the conventional WC-
Since the amount is increased compared to the Co-based cemented carbide, there is an effect that a cemented carbide with high hardness and high toughness can be obtained.

Furthermore, according to the manufacturing method of the present invention, since the sintered body of WC-Co-based cemented carbide is carburized, the conventional WC
This has the effect that an alloy with higher hardness and toughness than -Co-based cemented carbide can be obtained through simple processing.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram for explaining the composition of the cemented carbide of the present invention.

Claims (2)

[Claims] (1) Solid solution W amount x (
The relational expression between solid solute C content y (atomic %) is x+5y-
18>0 3≦X≦8 y≦4 A WC-Co cemented carbide. (2) WC-Co-based super-hard alloy powder is sintered in an inert atmosphere or in vacuum, and then the cemented carbide according to claim 1 is produced by carburizing treatment. Hard metal manufacturing method.