JPS62274044A - Diamond lump for tool and its production - Google Patents

Abstract

PURPOSE:To improve strength as well as heat resistance, by subjecting a powder mixture of a diamond powder and a powder of transition metals of group IVa, Va, or VIa of the periodic table and/or carbides of the above metals, etc., to sintering at and under the prescribed high temp. and high pressure. CONSTITUTION:The diamond powder and the powders of transition metals of group IVa, Va, or VIa of the periodic table and/or the carbides of the above metals and iron group metals are mixed. The resulting powder mixture is sintered under the conditions of a pressure of >=50kb, a temp. of >=1,300 deg.C, and a time of >=5min to be formed into a diamond lump. This lump is composed of 80-95vol% diamond and the balance binding phase consisting of the above mentioned carbides of the transition metals of group IVa, Va, and VIa of the periodic table and iron group metals which are mutually bound. Moreover, the content of the above-mentioned iron group metals and the grain size of the above diamond are regulated to 0.05-3vol% (in the form of the relative ratio to diamond) and 0.1-200mum, respectively.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Industrial Field of Application] The present invention provides a diamond block having high strength and heat resistance suitable for use as a cutting tool and a rock excavation tool. The present invention relates to a manufacturing method thereof.

C. Prior Art] Currently, sintered bodies with a diamond content of 70% by volume or more and diamond particles bonded to each other are sold, and are used for cutting nonferrous metals, plastics, and ceramics, dressers, drill bits, and wire drawing dies. is used.

In particular, when these diamond sintered bodies are used as dies for cutting non-ferrous metals or drawing relatively soft wire materials such as copper wire, their performance is extremely excellent.

For example, Japanese Patent Publication No. 52-12126 discloses a method for manufacturing this type of sintered body, in which diamond powder is arranged so as to be in contact with a compact or sintered body of WC-Co cemented carbide. However, sintering is carried out at a temperature higher than the temperature at which the liquid phase of the cemented carbide occurs and under ultra-high pressure. At this time, a part of 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 contains 10 to 15% by volume of Co.

[Problems to be Solved by the Invention] The above-mentioned 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;
At temperatures above 0°C, the sintered body will be destroyed.

Therefore, at present, no diamond sintered body with satisfactory performance has been obtained when used in drill bits and the like.

The present inventors have discovered that the reason why commercially available diamond sintered bodies do not exhibit sufficient performance when used as drill bits for drilling hard rocks such as andesite and granite is that iron group metals such as Co are used as binding materials. I found out that there is a point.

In other words, when excavating hard rocks, the drilling force becomes high and the sintered diamond becomes hot. descend.

(2) Coefficient of thermal expansion of iron group metal binders such as Co (for example, Co has a coefficient of linear expansion of 18 x 10''''') and coefficient of thermal expansion of diamond (coefficient of linear expansion is 4.5 x 107') Because of the large difference between the two, cracks occur due to the difference in thermal expansion when used at high temperatures, reducing the bonding strength between the particles.

It turned out that.

A method for improving the heat resistance of a diamond sintered body is to remove iron group metals such as Co, which promote graphitization of diamond at high temperatures, as described in JP-A-53-114589.

However, when iron group metals such as Co are eluted from the diamond sintered body, the strength of the diamond sintered body increases from 20 to 20.
30% decrease. In particular, when a diamond sintered body is used as a bit, strength, wear resistance, and heat resistance are required at the same time. The drill bit used had a short lifespan due to the cutting edge breaking due to the lack of strength of the diamond sintered body.

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

Furthermore, as another method to improve the above drawbacks (1) and (2), instead of using iron group metal binder such as Co, c
It is conceivable to use BN or SiC as the binding material. cBN and SiC have a small difference in thermal expansion from diamond, and have good thermal conductivity and thermal stability.

However, in a sintered body made only of diamond powder and cBN powder, the bond between diamond and cBN is weak, so when used as a tool, particles tend to fall off, resulting in reduced wear resistance.

For this reason, the sintered body containing diamond and cBN, which has been developed as a cutting tool material, is C.

It contains an iron group metal phase such as, and is bonded through this phase.

Therefore, this method cannot improve the above drawback (1).

On the other hand, attempts to use SiC as a binder have been made using a method in which diamond powder and molten Si are reacted, and a method in which diamond and S
Methods such as solid-phase sintering of iC are known, but in any of these methods, bonding between diamond particles is not observed, so when used as a tool, the wear resistance is poor.

As an improvement to this, JP-A-59-16126111 discloses a method of promoting bonding between diamond particles by using Ni and Si as binder raw materials. Materials are Ni1 nickel silicide, Sl,
It consists of SiC etc. However, Ni1 nickel silicide and Si are substances that are not desirable to contain from the viewpoint of heat resistance and wear resistance of the mass. Therefore, even with this method, a product with satisfactory performance has not been obtained.

Therefore, an object of the present invention is to provide a diamond ingot 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 invention have made the following invention as a result of extensive studies in order to obtain a diamond for tools that has even better heat resistance and strength. That is, the diamond mass for tools of the present invention has 80 diamonds bonded to each other.
~95% by volume, the remaining bonded phase is from the periodic table ■a -, V
It consists of a carbide of a transition metal of group a or group a and an iron group metal, and the km content of the iron group metal is 0.05 to 3.0 km relative to diamond. It is characterized by being 0% by volume.

Furthermore, as a method for manufacturing the above-mentioned diamond lump for tools, a mixed powder of diamond powder and a transition metal of group IVa, Va or VIa of the periodic table and/or a carbide of the transition metal and an iron group metal is prepared. , discloses a production method in which the mixed powder is placed inside a high-pressure generator, and the diamond is sintered by exposing it to a high temperature and pressure of 1300° C. or higher for 5 minutes or more in a stable diamond of 50 kb or more.

' [Function] The diamond mass of the present invention has greatly improved heat resistance compared to conventional sintered diamond, and has a heat resistance of about 1000°C.
It was found that it can withstand heating to a crystallinity of 1. The reason for the remarkable improvement in heat resistance is that the capacity of the iron group metal contained in the binder is 0.0 as a relative ratio to diamond.
5-3. 0.82%, so conventional Co
This is thought to be due to the fact that the reverse conversion from diamond to graphite is difficult to occur even in high-temperature conditions where a sintered body using carbon as a binder undergoes thermal deterioration.

Further, carbides of transition metals in groups IVa, Va, or VIa of the periodic table, which are one of the bonding phases, have a coefficient of thermal expansion similar to that of diamond, so that almost no cracking occurs at high temperatures. Furthermore, these carbides themselves have high wear resistance and have a high bonding strength with diamond, that is, a high retention force for diamond particles, so the diamond mass according to the present invention has higher wear resistance than conventional ones. We are prepared.

In carrying out the present invention, diamond powder, which is a starting material, may be either natural or synthetic, but diamond powder is heated to a temperature of 1300°C or higher in vacuum or in a non-oxidizing atmosphere, and part or all of it is converted into graphite. The converted one is most preferable.

Here, there are two reasons for using diamond particles whose surfaces are graphitized as a raw material.

Firstly, ■Diamond is difficult to deform plastically, so even under ultra-high pressure, voids remain between individual particles, which creates unstable pressure in some parts of the diamond and reduces sinterability. If this is done, the effective pressure will not drop because it fills the void. In addition, in the reaction process of (1) dissolving the carbon raw material in the binder and precipitating it as diamond, graphite has a lower chemical potential than diamond and has a higher ability to dissolve in the binder, so the reaction rate is faster.

In order for these effects to be noticeable, it is necessary to graphitize 0.5 to 80% by volume of the diamond particles.

Graphitization amount is 0. If the volume is less than 96%, the increase in packing density will be insufficient and the bond between diamond particles in the synthesized sintered body will be weak, and if it is more than 80%, graphite will remain and the sintering strength will be low. I can only get one body.

Note that graphitization of the surface of the diamond powder may be performed before or after mixing with transition metals, iron group metals, etc.

The above-mentioned diamond powder has 80 to 95% by volume of diamond in which the final mass is bonded to each other, and
The remaining binder phase consists of a carbide of a transition metal of group IVa, Va, or VIa of the periodic table and an iron group metal, and the content of the iron group metal is Oo 05 to 05 as a relative ratio to diamond.
It is uniformly mixed with a transition metal of group rVa, Va or VIa of the periodic table and/or a carbide of the transition metal and an iron group metal so that the amount is 3.0% by volume.

Here, the smaller the particle size of the binder raw material, the more preferable it is, and usually fine particles of about several μm or primary particles of several tens of micrometers are used.
Use ultrafine powder of A.

In addition, the inventors' earlier application (Japanese Patent Application No. 52-51881)
The periodic table of mixing pots and balls during ball milling as disclosed in IV a of the Periodic Table.

A sintered body of Va and VIa group carbides and iron group metals is prepared, and at the same time diamond powder is ground in a ball mill, the periodic table ■asVasV1a is prepared from the pot and ball.
A method may also be adopted in which fine powder of a sintered body of a group carbide and an iron group metal is mixed.

Furthermore, a method of coating the surface of the diamond powder with a binder raw material is also effective.

The mixed powder prepared by the above method serves as a raw material for sintering as it is, but if the mixed raw diamond powder has not been graphitized, it must be heated in a vacuum or in a non-oxidizing state after being mixed as described above. It may be heated to a temperature of 1300° C. or higher in an atmosphere.

The mixed powder of the above-mentioned sintered body raw material is exposed to high temperature and high pressure of 1300° C. or higher for 5 minutes or more using a known high-pressure generating device such as a belt-type device at a temperature of 50 kb or more, at which diamond is thermodynamically stable. Periodic table IVa, V as a binder raw material
When a transition metal of Group a or VIa is used, the transition metal undergoes a carbonization reaction with diamond under the above-mentioned high temperature and high pressure conditions, and carbides of the transition metal are formed on the surfaces of individual diamond particles. Since these carbides have good wettability with iron group metals in a molten state, their relative ratio to diamond is 0.05 to 3. The iron group metal mixed in a trace amount of 0% by volume permeates uniformly into the mixture. This molten iron group metal promotes bonding between diamond particles and the carbides, as well as bonding between the diamond and the carbides.

After sintering, only the heating is stopped while maintaining the pressure.
After the high temperature and high pressure generation chamber has cooled to around room temperature, the holding pressure is gradually released to return to normal pressure. The sintered bodies obtained according to the above method all have high hardness and
It can also withstand heating.

[Example] Example 1 Synthetic diamond powder with a particle size of 20 to 30 μm was prepared in a 5×10
Heat treatment was performed in a vacuum of −' torr at 1450° C. for 30 minutes to graphitize the surface of each particle by 10% by volume. This graphitized diamond powder has an average particle size of 1 μm.
The mixture was mixed with a WC powder of 500 mm and an ultrafine Co powder of a primary particle size of 500 A in a volume ratio of 85:13.5:1.5, and mixed for 12 hours using a mixer.

This mixed powder was filled into Mo capsules and sintered at 1400° C. for 30 minutes at 60 kb using a belt-type high pressure generator. The obtained sintered body has a black color, and its composition is such that diamond particles are bonded to each other and the remainder is W C-Co.
It was filled with alloy.

The Vickers hardness was 10000 kg/mm2.

This sintered body A (Example) was heated to 950° C. for 30 minutes in a vacuum. For comparison, a conventional sintered diamond B (comparative example) bonded with 9% by volume of CO and exhibiting the same hardness as the sintered body A was similarly heated to 950° C. for 30 minutes in a vacuum.

As a result, in the comparative example sintered diamond B, graphite was generated at the interface between diamond and CO, and the hardness was 2500 k.
g/mm2. On the other hand, in the sintered body A of Example according to the present invention, no graphite formation was observed, and no decrease in hardness was observed.

Example 2 Natural diamond powder having an average particle size of 10 μm was heat-treated in argon gas at 1500° C. for 15 minutes to graphitize the surface of the powder by 12% by volume. This graphitized diamond powder was mixed with Ti and Mo powder with an average particle size of 5 μm.
Ni ultrafine powder with a secondary particle size of 25 OA was blended in a volume ratio of 86:12:0.2:1.8. The powder that was dry mixed for 2 hours was filled into a Zr container and sintered at 55 kb and 1500° C. using a belt-type high pressure generator.

Analysis of the obtained sintered body by X-ray diffraction revealed that the binder was composed of a solid solution of TiC and Mo2C and Ni. This sintered body C (example) was combined with a commercially available sintered diamond D containing 10% by volume of Co as a binder (comparative example), and the Co binder was extracted by acid treatment, resulting in a residual CO of 2% by volume. A heating test was conducted under the following conditions together with heat-resistant sintered diamond E (comparative example) having 8% by volume of pores.

Heating test conditions> Heating temperature: room temperature - 1000°C (held for 5 minutes) Atmosphere: As a result of the heating test above the atmosphere, sintered body D (comparative example) expanded and cracked. Moreover, the sintered body E (comparative example) was in a powdered state. On the other hand, the shape of the sintered body C of Example according to the present invention remained unchanged, and no change in weight was observed before and after heating.

Example 3 After mixing diamond powder and Ti powder having the same particle size as in Example 2 at a volume ratio of 9:1, heat treatment was performed at 1500° C. for 30 minutes in vacuum.

As a result of X-ray diffraction, the obtained powder was found to contain diamond, Ti
It was found to consist of C and a trace amount of graphite. To this powder, 0.0% Mo powder and 0.0% Ni powder were added respectively. 2
ff196.1.8% by volume was added and mixed again. This mixed powder was sintered in the same manner as in Example 2, and the resulting sintered body F (Example) was subjected to a heating test. As a result, as in Example 2, the shape remained unchanged, and no change in weight was observed before and after heating.

Example 4 Diamond and binder raw materials were mixed in the proportions shown in Table 1, and the resulting mixed powder was 5111 kb, 1600 kb
Sintered at °C.

*) The value when all diamonds are graphitized is 1.
A cutting tip was prepared using the obtained sintered body with a capacity ratio of 0, and an alumina sintered body having a Vickers hardness of 2200 was cut, and the performance of each was evaluated.

The cutting test was conducted at a cutting speed of 50 m/min and a depth of cut of 0.
．． 2 mm, feed: 0.25 mm/rpm, and cutting time: 15 minutes under wet conditions.

The results of the cutting test are shown in Table 2.

As is clear from Table 2, the sintered body I of the comparative example has poor wear resistance due to the low diamond content, and the sintered body J of the comparative example has a Co content exceeding the range of the present invention. It is thought that this caused the deterioration of heat resistance. In addition, the sintered bodies of the comparative examples had the same composition as those using commercially available Co as a binder, but the sintered bodies G and H of the examples according to the present invention had the same composition.
It was found that both heat resistance and wear resistance were improved compared to this sintered body K.

[Effects of the Invention] As explained above, the diamond block for tools of the present invention is excellent in both heat resistance and strength, so it is effective as a material for various tools such as cutting tools, drilling tools, wire drawing dies, and dressers. It is used for. In particular, unlike conventional diamond sintered bodies, the heat resistance has been significantly improved without reducing strength, making it possible to dramatically expand the range of applications as a tool material.

(2 others)

Claims (6)

[Claims] (1) 80-95% by volume of mutually bonded diamonds
, and the remaining bonded phase is from the periodic table IVa, Va or VIa
The iron group metal is composed of a carbide of a group transition metal and an iron group metal, and the content of the iron group metal is 0.0% relative to the diamond.
A diamond ingot for tools, characterized in that the content is 0.05 to 3.0% by volume. (2) The diamond mass for a tool according to claim 1, wherein the diamond has a particle size of 0.1 to 200 μm. (3) Diamond powder and periodic table IVa, Va or
A mixed powder of a group VIa transition metal and/or a carbide of the transition metal and an iron group metal is prepared, and the mixed powder is placed inside a high-pressure generator.
By sintering it by exposing it to high temperature and high pressure of 1,300℃ or more for 5 minutes or more at a temperature of 1,300℃ or more, the diamonds bonded to each other account for 80 to 95% by volume, and the remaining bonding phase is a phase I of the periodic table.
Producing a diamond lump consisting of a carbide of a Va, Va or VIa group transition metal and an iron group metal, and in which the content of the iron group metal is 0.05 to 3.0% by volume relative to the diamond. A method for producing a diamond block for tools, characterized by: (4) As the diamond powder, use is made of diamond powder obtained by exposing diamond to high temperature under thermodynamically unstable conditions and converting part or all of it into graphite. The method for manufacturing the described diamond block for tools. (5) A patent characterized in that the mixed powder is exposed to high temperature under conditions in which diamond is thermodynamically unstable to convert some or all of the diamond in the mixed powder into graphite before use. A method for manufacturing a diamond block for tools according to claim 3. (6) The diamond powder has a particle size of 0.1
The method for producing a diamond block for tools according to claim 3, 4 or 5, characterized in that a diamond block having a diameter of 200 μm is used.