JPS61235533A - High heat resistant sintered hard alloy - Google Patents

Abstract

PURPOSE:To obtain an sintered hard alloy which has the high heat resistant and is excellent in the thermal shock resistance and the toughness and endures the severe use conditions by consituting a rigid phase and a joined metallic phase wherein the rigid dispersion particles having the specified particle size are dispersed uniformly and finely. CONSTITUTION:The high heat resistant sintered hard alloy consisting of the rigid phase and the joined metallic phase and the rigid dispersion particles having 0.01%n3mum particle size are dispersed uniformly and finely in the above- mentioned joined metallic phase endures enough the use in a severe use conditions such as a rapid thermal cycling and the elevation in the surface temp. of a tool. As the above-mentioned rigid dispersion particles, one or more kinds among ThO2, Al2O3. ZrO2, Y2O3, SiO2, Al4O3, WC, SiC, Si3N4, AlN, YN, TiB2 and ZrB2 are used. Also as the above-mentioned rigid phase, the phase consisting of WC is suitable and as the joined metallic phase, the phase consisting of one or more kinds among Ni, Co, Fe, Cr, Mo and W are preferable. Furthermore it is desirable that the amount of the joined metallic phase is regulated to 10-35wt.% total amount and the amount of the rigid dispersion particles is regulated to 10-40 vol.% joined metallic phase.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a highly heat-resistant cemented carbide used, for example, in tools for warm and hot forging.

Conventional Technology Conventionally, die steel (SKD61) has been mainly used as a material for molds and punches used for hot forging.

Die steel is prone to thermal cracking and deformation on its surface. Therefore, at present, the lifespan of molds and punches made of die steel is short, and the dimensional accuracy of the products is poor. Therefore, parts after hot forging require grinding.

However, as a recent trend, precise warm forging and precise hot forging are desired in order to omit the erosion process after forging.

Problems to be Solved by the Invention However, there are the following problems. In warm forging and hot R forging, the concentration of the workpiece is high. Moreover, heat generation occurs due to the deformation of the forged material. As a result, the temperature on the mold surface rises rapidly. On the other hand, after removing the workpiece from the mold, lubricant, cooling water, cooling oil, etc. are sprayed onto the mold surface.
The mold is rapidly cooled.

Thermal shock caused by such rapid changes in temperature causes damage to the mold surface. In addition, warm here means about 200-800 degrees Celsius, and hot means about 800-1100 degrees Celsius
It indicates the range of degrees Celsius.

Therefore, conventionally used die steel suffers from severe surface roughness, deformation, and thermal cracking, and because the steel has large thermal expansion, high precision cannot be achieved.

Even with 5K) l-51, which has a high hardness at high temperatures, there are problems such as thermal expansion, thermal cracks, and cracks, and a long life cannot be expected.

In comparison to the above-mentioned materials, a cemented carbide having a thermal expansion at high temperatures of 172 that of steel is preferred. However, the cemented carbide used in the current market has low thermal shock resistance and low toughness, so it cannot be used under severe usage conditions such as hot forging.

Therefore, an object of the present invention is to provide a highly heat-resistant cemented carbide that can be satisfactorily used even under severe usage conditions such as rapid thermal cycles and increases in tool surface temperature.

Note that, as a cemented carbide used in hot conditions, rolling rolls used for rolling steel wire are known.

However, this rolling roll is used under uniform load during rolling. In other words, the strong heat rIt as described above is not applied to the rolling roll. From this, it can be inferred how severe the above-mentioned usage conditions are.

Means for Solving the Problems, Actions and Effects of the Invention The highly heat-resistant cemented carbide according to the present invention consists of a hard phase and a binder metal phase. And the bonded metal phase grain size is 0.01 μ-
It is characterized in that hard dispersed particles of 3 μm or less are uniformly and finely dispersed.

To improve the toughness and thermal cracking properties of cemented carbide.

The amount of bound metal phase may be increased. However, if this is done, the hardness of the alloy will decrease and the conditions for a forging die will no longer be satisfied. Therefore, the aim of this invention is to
Not only hardness at room temperature, but also high hardness under warm or hot forging conditions! The object of the present invention is to obtain an alloy composition and structure that can maintain high hardness at temperatures (200 to 1100°C).

In order to achieve this, the hard dispersed particles dispersed in the bonded metal phase have a particle size of 0.01 μm or more and 3 μm or less. If the particle size is between 0.03 μm and 1 μm, the dispersion effect is greatly enhanced. There are various methods for dispersing hard dispersed particles into a bound metal phase. For example, conventional powder metallurgy methods may be used for dispersion. Further, if dispersed particles are dispersed in the metal powder serving as the bonding metal phase in advance or during mixing using the recently developed mechanical alloying method, a more homogeneous cemented carbide can be obtained. That is, in a vacuum atmosphere, an inert gas atmosphere, a nitrogen gas atmosphere, or an atmosphere with various oxygen partial pressures, dispersed particles are mixed into a bonded metal powder using a dry high-energy attritor or ball mill. A greater effect can be obtained by dispersing it during mixing.

The hard dispersed particles are preferably TtlOz,A(L20
3, Zr0z, Y2O5, St Ot, An<Cs,
WC, Si C, Si a N4% A garden N, YN,
T! One or more substances selected from the group consisting of B2NZrB2. If these substances are used as hard dispersed particles, the cemented carbide will exhibit high heat resistance. Further, the hard phase is made of, for example, tungsten carbide. Additionally, the bound metal phase can include, for example, Ni, Go, Fe, Or, MOL
It consists of one or more substances selected from the group consisting of W.

Preferably, the content of the binding metal phase is within the range of 10% to 35% by weight of the total, and in the case of hard dispersed particles,
The content of the binder metal phase is within a range of 10% by volume or more and 40% by volume or less. If the amount of binding metal phase is less than 10% by weight, toughness is insufficient. On the other hand, m of this bonded metal phase is 3
If it exceeds 5% by weight, the hardness will be insufficient and therefore it will not be able to withstand use as a forging die. If the amount of hard dispersed particles is within the range of 10% by volume or more and 40% by volume or less of the bound metal phase, the dispersion effect is high, the strength and hardness are high, and heat resistance is exhibited. The amount of hard dispersed particles is 1
If it is less than 0% by volume, the amount of hard dispersed particles dispersed within the bonded metal phase will be insufficient, and therefore the desired effect will hardly be obtained. On the other hand, if the amount of hard dispersed particles exceeds 40% by volume of the bonded metal phase, the toughness within the bonded metal phase will decrease, which will have the opposite effect.

FIG. 1 is a diagram showing changes in ^Il hardness of various alloys. In the figure, 1 is a heat-resistant cemented carbide according to the present invention.

2 is normal WC-Go, 3 is 5KH9, and 4 is 5KD61. As is clear from this figure, the cemented carbide according to the present invention can maintain high hardness, especially at high temperatures.

The cemented carbide obtained according to the present invention can be advantageously used as a plastic working tool for hot or warm forging, such as a die, punch, knockout, ejector pin, shear blade, roll, etc. However, it is not necessary that the entire tool be made of cemented carbide according to the invention. For example, the cemented carbide according to the present invention may be used only in the part of the tool that comes into contact with the workpiece, and the other parts may be made of steel. In this case, the cemented carbide part and the steel part are joined together, for example, by welding, such as electron beam welding or laser beam welding. Further, on the surface of the cemented carbide according to the present invention, Ti c, -r+ ON, Ti
Co, Tt CNO, A fLt Oh, An N
N SI s N 4 , S j CB N , C
It may be coated with one or more layers such as.

Examples Example 1 The following tests were conducted by changing the mixing ratio of the raw material for the bonded metal phase and the raw material for the hard dispersed particles, and by roughly changing the type of the hard dispersed particles.

First, the raw materials for the bonded metal phase of 1 to 2μ and the raw materials for the hard dispersed particles of 0.5 to 1μ are charged into an attritor, and in an Ar gas atmosphere, a dry process is carried out at a rotational speed of 20 or IllI.
1111 mechanical alloying treatment was performed. To simulate this, 3 to 5 micron tungsten carbide powder was charged, and acetone was added to the top of the container and mixed in a wet manner for 10 hours. The obtained mixed powder was molded into bales of required dimensions, sintered under vacuum, and then subjected to HIP treatment. The sintered body thus obtained was polished and its high temperature strength and hardness were measured. The results are summarized in Table 1 below.

As comparative examples, samples were prepared in which the amount of the bonded metal phase was less than 1011 m% of the total weight, a sample in which the amount of the bonded metal phase exceeded 35% by weight of the total weight, and a sample in which no hard dispersed particles were charged, and their high temperature strength and hardness were evaluated. It was measured.

As is clear from Table 1, the cemented carbide obtained according to the present invention exhibits excellent properties, particularly in hardness and transverse rupture strength at high temperatures.

(The following is a blank space) Example 2 Using the alloy obtained in Example 1, a bunching die for hot forging was made. This bunching die has a diameter of 35II.
A workpiece obtained by heating No. 11 steel bar to 1150° C. and cutting it is used for punching.

The performance of the bunching die obtained in this way was evaluated by the following second method.
It is summarized in the table.

As is clear from Table 2, it is recognized that the performance of the bunching die made of cemented carbide having a bonding metal phase and having hard dispersed particles dispersed in the bonding metal phase is good.

In this embodiment, the case where the HIP process is performed is taken as an example, but the same effect can be obtained even when the HIP process is not performed.

(Margin below) Table 2 Example 3 Alloys were made in the same manner as in Example 1 by varying the grain size of sample number 3 in Example 1, and the same evaluation as in Example 2 was carried out. The results obtained are summarized in Table 3.

As is clear from Table 3, 0.01μll~3μ+m
It is recognized that the following hard dispersion particle diameters have good performance.

Table 3

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the high temperature hardness changes of a conventional alloy and an alloy according to the present invention. In the figure, 1 is an alloy according to the present invention, 2 is a conventional WC
-Co alloy, 3 is worker steel 5KI-19, 4 is tool J11
It is SKD61. (2 others)

Claims (5)

[Claims] (1) A highly heat-resistant cemented carbide consisting of a hard phase and a bonded metal phase, characterized in that hard dispersed particles with a particle size of 0.01 μm or more and 3 μm or less are uniformly and finely dispersed in the bonded metal phase. . (2) The hard dispersed particles include ThO_2, Al_2O_
3, ZrO_2, Y_2O_3, SiO_2, Al_4
C_3, WC, SiC, Si_3N_4, AlN, YN
, TiB_2, ZrB_2
The highly heat-resistant cemented carbide according to claim 1, characterized in that it is a species or two or more kinds of substances. (3) The highly heat-resistant cemented carbide according to claim 1 or 2, wherein the hard phase is made of tungsten carbide. (4) The binding metal phase is Ni, Co, Fe, Cr, M
The highly heat-resistant cemented carbide according to any one of claims 1 to 3, characterized in that it is made of one or more substances selected from the group consisting of O, W, and W. (5) The amount of the binding metal phase is 10% or more by weight of the total3
5% by weight or less, and the amount of the hard dispersed particles is in the range of 10% by volume or more and 40% by volume or less of the binding metal phase. High heat-resistant cemented carbide according to any one of Item 4.