JPS61111964A - Sintered diamond for tool and manufacture - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a sintered diamond used in tools such as cutting tools, drilling tools, and wire drawing dies, and a method for producing the same.

[Prior Art] Diamond sintered bodies made by sintering fine diamond powder under ultra-high pressure are already widely used in tools for cutting non-ferrous metals, drill bits, wire drawing dies, and the like.

For example, Japanese Patent Publication No. 52-12126 discloses a method for manufacturing this type of sintered body, in which diamond powder is placed in contact with a compact or sintered body of WC-Co 81 hard alloy. Sintering is carried out at a temperature above the temperature at which the liquid phase of the cemented carbide occurs and under ultra-high pressure. At this time, a part of the CO in the cemented carbide penetrates into the diamond powder layer and acts as a bonding metal. The diamond sintered body made by the method disclosed in this prior art has approximately 10
Contains ~15% CO by volume.

[Problems to be Solved by the Invention] The above-described sintered body has sufficient practical performance as a cutting tool for non-ferrous metals and the like. However, it had the drawback of being inferior in heat resistance.

For example, when this sintered body is heated to a temperature of 750°C or higher, a decrease in wear resistance and strength is observed, and a further
At temperatures above 'C, the sintered body will be destroyed. This is thought to be due to graphitization of the diamond occurring at the interface between the diamond particles and the binder Co, and thermal stress due to the difference in coefficient of thermal expansion when the two are heated.

Furthermore, it is known that when a sintered body using CO as a binder is treated with an acid to remove most of the binding metal phase, the heat resistance of the sintered body is improved.

For example, JP-A-53-114589 discloses a method for manufacturing a diamond sintered body with improved heat resistance. However, in this prior art, the removed portions of the bonded metal phase become pores, so although the heat resistance is improved, there is a problem in that the strength is reduced.

On the other hand, attempts have been made to sinter only diamond powder under ultra-high pressure, but since the diamond particles themselves are difficult to deform, pressure is not transmitted to the gaps between the particles, resulting in graphitization and diamond powder. Only graphite composites have been obtained.

Therefore, an object of the present invention is to provide a sintered diamond for tools that is excellent in both heat resistance and strength, and a method for manufacturing the same.

[Means for Solving the Problems] The inventors of the present application have made the following invention as a result of intensive studies in order to obtain a diamond sintered body that is even more excellent in heat resistance and strength.

That is, the sintered diamond for tools of this invention has diamond Ii! %r60.0-99.9%, the remainder being formula (Fax, cr 1-8), C.

The sintered diamond for tools having the above composition contains 59.9 to 9 carbon-containing substances,
A mixture containing 8% by weight and the balance consisting of lee and Cr is used as a raw material and exposed to ultra-high pressure and high temperature where diamond is thermodynamically stable, to promote the formation and sintering of diamond, and to form carbides of the metal. This is a method for producing sintered diamond for tools, characterized by forming a sintered diamond.

[Function] The sintered diamond for tools according to the present invention has greatly improved heat resistance compared to conventional sintered diamond,
It was found that it could withstand heating to a temperature of about 1000°C. The reason for the remarkable improvement in heat resistance is that first, the binder phase is composed of a carbide represented by the formula (Fe x , Cr t-x )7C3 (where x = 0°05 to 0.95). This is thought to be because the reverse conversion from diamond to graphite does not occur even in high-temperature conditions where conventional sintered bodies using C0 as a binder undergo thermal deterioration.

The second reason is that these carbides have a smaller difference in coefficient of thermal expansion with diamond than metals such as CO that act as catalysts during diamond formation or alloys of these metals, so the sintered body does not hold up when heated. It is surmised that the thermal stress generated inside is reduced.

In carrying out this invention, carbon-containing materials used as starting materials include diamond, graphite, pyrolytic graphite, glassy carbon, and diamond, which are exposed to high temperatures under thermodynamically unstable conditions, and some or all of them are converted into graphite. and mixtures thereof can be used.

Diamonds can be either natural or synthetic.

Among the above-mentioned carbon-containing materials, the most preferred is one obtained by heating diamond powder to a temperature of 1400'C or higher in vacuum or in a non-oxidizing atmosphere to convert part or all of it into graphite.

The above carbon-containing substance is 59.9 to 99.8 in the starting material.
Adjust to account for weight %. The fifth rank of carbon-containing substances is 5.
If it is less than 9.9% by weight, the wear resistance of the sintered body will decrease, while if it exceeds 99.8% by weight, sintering will be difficult and graphite will remain partially, resulting in a sintered body with low strength. This is because all you can get is the body.

After mixing the above-mentioned carbon-containing substances with Fe and Cr, they are placed at high pressure in an ultra-high pressure generating device such as a belt-type device, and sintered under ultra-high pressure and high displacement at a temperature of 5Qkb11300°C or higher, where diamond is stable. be done. Under these conditions, due to the action of Fe and Cr, diamond formation and
Sintering progresses.

At the same time, these diamond-forming catalyst metals are calculated according to the formula (Fax) according to the l"e and Cr blending ratio of the raw materials.

C'r + -x) 70s (in the formula, will be done.

The molar ratio of the above 1"e and Cr is 0.
05 to 0.95 is because if it is less than 0.05, the proportion of bonds between diamond particles will decrease and a sintered body with high strength cannot be obtained.On the other hand, if it exceeds 0.95, the formed carbide will be This is because it easily decomposes into metal and graphite at temperatures of 700° C. or higher.

The sintered diamonds obtained by the above methods all have high hardness and can withstand heating to 100°C.

Note that the bonding layer in the sintered diamond of this invention is
CFex, Cr+-X)? It is a carbide represented by CO, but some of this Cr is replaced by W and MO.

It is also possible to substitute with Mn or the like.

Also, when producing a sintered body, carbon-containing substances and Fe are used.

Instead of pre-mixing Cr powder, carbon-containing material and F
It is also possible to laminate e, Cr, or an alloy thereof and sinter it under ultra-high pressure. In this case, the melted l
'-e-Cr alloy penetrates into the layer of carbon-containing material, resulting in the formation of a bonded phase of (Fax, Cr+-X)7C-.

[Explanation of Examples] Hereinafter, the present invention will be described in detail based on Examples.

Example 1 Synthetic diamond with an average particle size of 101.1Ill was
It was mixed with metal powder at the ratio shown in the table and filled into a metal reaction container. Furthermore, among those shown in Table 1, sintered body F
For comparison, Co was used as well as commercially available sintered diamond.
It contains as a binding material.

Using each of the samples A to F shown in Table 1, 70 kb and 1600°C were used in a belt-type ultra-high pressure generator.
Sintering was performed for 0 minutes. All recovered sintered bodies were strong.

For each of the above sintered bodies A to G, 1000°C in vacuum.
A heating test was conducted at a temperature of . As a result, no change was observed in the appearance or specific gravity of any of the sintered bodies A to E. On the other hand, cracks appeared in the sintered body F, which was equivalent to the commercially available sintered body, and the sintered body G, in which only Fe was used as a binder raw material. After this heating test, it was confirmed by X-ray diffraction that graphite was generated in the cracked sintered bodies F and G.

It was found that the binder of the sintered body G before heating was 1"e7ca, but it was decomposed into Fe and graphite after heating.

Example 2 Sintered bodies A to D shown in Table 2 and commercially available sintered diamond made by bonding 801ffi% diamond with WC-Co were processed to create a cutting tip, and an alumina sintered body of Vickers code 2000 was produced. were cut and the performance of each was evaluated.

The cutting test was conducted under dry conditions: cutting speed: 50 m/min, depth of cut: 0.5111 m1, feed: 0.05 m+/rpm, and cutting time: 15 minutes.

The results of the cutting tests are shown in Table 3, and it was found that the sintered bodies had a high binder phase content and were inferior in wear resistance, but the sintered bodies A to C all showed high wear resistance. Ta.

(Left below) Example 3 A mixed powder having the composition shown in Table 4 was filled into a Ta[ container.

The diamond used had an average particle size of 10 μm, and had been heated in advance to a temperature of 1500° C. for 30 minutes under a vacuum of 10-' Tor to graphitize a portion. Sintered diamond was obtained in the same manner as in Example 1 with respect to other conditions. The binder phase of the sintered body obtained in this way is
According to X-ray diffraction, in the sintered body P (Fe, Or, W
)tCa, and in the sintered body Q (Fe, Cr, M
It was confirmed that they were O)t Ch, and all were strong sintered bodies.

Example 4 A thin plate made of 75Fe-25Cr alloy was placed in contact with a layer of diamond powder subjected to the same graphitization treatment as used in Example 3, and this was heated to 60 kb and 1600 kb using a belt-type ultra-high pressure generator. ℃ temperature for 10 minutes. The obtained sintered body had a diameter of (1”e.

It had a binder phase of Cr)tca and did not crack even when heated to a temperature of 1000°C.

[Effect of the invention 1 (a) As mentioned above, according to this invention, diamond accounts for 60.0 to 99.9% by weight, and the remainder is of the formula (Fe
x, Crl-X)? Sintered diamond for tools made of carbide represented by Cs (in the formula, x is in the range of 0.05 to 0.95) can be used for cutting tools, drilling tools, wire drawing dies, and dressers. Sintered diamond for tools with excellent heat resistance and wear resistance can be obtained as a material for various tools such as. In particular, unlike conventional diamond sintered bodies, the heat resistance is significantly improved without reducing strength, so the range of application as tool materials can be dramatically expanded.

Claims (3)

[Claims] (1) Diamond accounts for 60.0 to 99.9% by weight, and the remainder is of the formula (Fe_x, Cr_1_-_x)_7C
Carbide represented by _3 (where x is 0.05 to 0.9
A sintered diamond for tools, characterized in that the number is in the range of 5). (2) A mixture containing 59.9 to 99.8% by weight of a carbon-containing substance, with the balance consisting of Fe and Cr, is exposed to ultra-high pressure and high temperature at which diamond is thermodynamically stable. 60% by weight of diamond, which is characterized by promoting coalescence and carbonizing the metal.
．． It accounts for 0 to 999%, and the remainder is represented by the formula (Fe_x, Cr_1
A method for manufacturing a sintered diamond for tools made of a carbide represented by ____x)_7C_3 (in the formula, x is a number in the range of 0.05 to 095). (3) Sintering for tools according to claim 2, which uses a raw material obtained by exposing diamond to high temperature under thermodynamically stable conditions and converting part or all of it into graphite as the carbon-containing substance. How diamonds are made.