JPS6141865B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an ultra-high pressure sintered material that has excellent toughness and heat and wear resistance, and is particularly suitable for use as a material for cutting tools. Generally used for cutting tools used to cut ferrous metal materials such as cast iron, non-ferrous metal materials such as aluminum, aluminum alloys, copper, and copper alloys, and non-metallic materials such as plastics, rubber, graphite, and ceramics. are required to have properties such as high hardness, excellent wear resistance, toughness, and thermal and chemical stability. In recent years, in order to satisfy such demands, ultra-high pressure sintered materials whose main component is diamond have been proposed, and the ultra-high pressure sintered materials have high hardness not only at room temperature but also at relatively high temperatures, and have excellent properties. Because it exhibits wear resistance, it is used as a material for finishing cutting tools under harsh conditions such as impact. It is true that the above-mentioned cutting tool made of ultra-high pressure sintered material enables high-speed cutting when cutting the above-mentioned ferrous metal materials and non-ferrous metal materials, making it difficult for built-up edges to stick and providing an excellent finished surface. This provides the advantage of being able to In this way, the conventional ultra-high pressure sintered materials mentioned above are mainly composed of diamond which has extremely high hardness, so they can be used as cutting tools for cutting the above-mentioned ferrous metal materials, non-ferrous metal materials, and non-metal materials. Although it shows excellent wear resistance when used,
Because it does not have sufficient toughness, chipping wear is likely to occur during cutting due to this lack of toughness, and as a result, the excellent wear resistance that it originally has cannot be fully demonstrated, and the Currently, it cannot be used for cutting that involves a rise in temperature because it does not have high-temperature oxidation resistance. From the above-mentioned viewpoint, the present inventors have determined that toughness,
In order to obtain a material for cutting tools that has resistance to reactions with ferrous metal materials, high-temperature oxidation resistance (heat resistance), and wear resistance, we conducted research focusing on diamond. Silicon (hereinafter referred to as SiC) and silicon nitride (hereinafter referred to as Si ₃ N ₄
) (hereinafter collectively referred to as Si carbon/nitride);
When a mixture of cubic boron nitride (hereinafter referred to as CBN) powder is used as a raw material powder and ultra-high pressure sintering is performed, diamond particles, Si carbon/nitride particles, and CBN particles are formed. There is no mutual contact between the particles, and the diamond particles, the Si carbon/nitride particles, and the CBN particles are adjacent to each other, and at the grain boundaries, the components that make up each particle diffuse, forming strong particles. A sintered material with a dense structure in which inter-bonds are formed is obtained, and the resulting sintered material has excellent wear resistance provided by diamond particles and Si carbon/nitride particles and They found that it combines the excellent shine and high-temperature oxidation resistance (heat resistance) provided by CBN particles. This invention was made based on the above knowledge, and has a composition consisting of diamond: 50 to 85%, Si carbon/nitride: 5 to 40%, and CBN: 10 to 45% in terms of volume percentage. The ultra-high-pressure sintered material for cutting tools is characterized by having excellent toughness, heat resistance, and wear resistance. Next, in the ultra-high pressure sintered material of this invention,
The reason why the component composition range is limited as described above will be explained. (a) Diamond As is well known, diamond itself has a Mohs hardness of 10 and a Knoop hardness of 8000 kg/mm2 or ^more (load of 100 kg/mm2).
g), which has the highest hardness among existing materials, but if the content is less than 50% by volume, the desired wear resistance cannot be secured; If the content exceeds the amount, the degree of contact between diamond particles increases,
The strong interparticle bonds between diamond particles and Si carbon/nitride particles, which have particularly high toughness, and CBN particles, which have particularly excellent high-temperature oxidation resistance (heat resistance), are insufficient, resulting in a decrease in toughness. Since chipping wear tends to occur during cutting, the content was set at 50 to 85% by volume. In addition, in the production of the ultra-high pressure sintered material of this invention, the diamond powder used as the raw material powder has an average particle size of 50 μm or less, generally 10 μm or less, in order to ensure excellent sinterability. It is preferable to use diamond powder with a metal coating, and commercially available metal-coated diamond powder may also be used as the raw material powder. (b) Si carbon/nitride For example, SiC has a melting point of 2827°C and a minute Knoop hardness of 3000 Kg/mm (load 100 g). All of these Si carbons and nitrides have high melting points and high hardness. In addition, it is a material with superior oxidation resistance at high temperatures compared to diamond, and it also contains Si.
As mentioned above, diamond particles, Si carbon/nitride particles, and CBN are added to the carbon/nitride particles during sintering in the production of the ultra-high pressure sintered material of the present invention.
In addition to contributing to the diffusion of components at the mutual grain boundaries of the particles and forming strong interparticle bonds, diamond itself has excellent sintering properties, so it can coexist with CBN particles between diamond particles. It has the effect of forming a dense tissue filled with
If the content is less than 5% by volume, the desired effect cannot be obtained, resulting in a decrease in toughness, while if the content exceeds 40% by volume, the diamond content will be relatively low. If the amount becomes too small, the high hardness of diamond cannot be fully reflected in the sintered material, resulting in a decrease in wear resistance. Therefore, the content is set at 5 to 40% by volume. Ta. Furthermore, in producing the ultra-high pressure sintered material of the present invention, the Si carbon/nitride powder used as the raw material powder is preferably fine powder, with an average particle size of 10 μm.
It is desirable to use fine powder of less than m. (c) CBN CBN has a temperature of 1200℃ or more, a pressure of 40Kb or more,
It is preferably synthesized at a temperature of 1,800℃ or higher and a pressure of 60Kb or higher, and has a hardness second only to diamond, i.e., 6,000 to 7,000 on the Vickers hardness.
Kg/mm ² and has properties that are more stable at higher temperatures than diamond and less reactive to iron group metals. Oxidation resistance and reaction resistance to iron-based metals cannot be ensured, and on the other hand, if the diamond content exceeds 45% by volume, the diamond content becomes relatively too small and the high hardness of diamond is lost. The content was determined to be 10 to 45% by volume because it could not be sufficiently reflected in the sintered material, resulting in a decrease in wear resistance. Further, in producing the ultra-high pressure sintered material of the present invention, the CBN powder used as the raw material powder is preferably fine, and it is desirable to use fine powder with an average particle size of 10 μm or less. Further, the ultra-high pressure sintered material of the present invention can be manufactured by a conventional powder metallurgy method using a known ultra-high pressure and ultra-high temperature generator. That is, diamond powder, Si carbon/nitride powder, and CBN powder as raw material powders are blended in a predetermined ratio, and this blended powder is mixed for a long time in a mixer such as an iron ball mill to form a homogeneous mixed powder. This mixed powder, for example,
It is sealed in a container made of steel or high melting point metal in an ultra-high pressure and high temperature generator as described in Publication No. 23463, and the pressure and temperature are raised to achieve the maximum pressure:
54-70Kb, maximum temperature: 1400-1800℃ Produced by a basic process consisting of holding at a pressure and temperature in the range of several minutes to several tens of minutes, cooling, and finally releasing the pressure. be able to. Next, the ultra-high pressure sintered material of the present invention will be explained using examples. As raw material powder, each commercially available average particle size: 3
Diamond powder with μm, SiC with same 3μm
powder, 2μm Si ₃ N ₄ powder, and 6μm Si 3 N 4 powder.
Prepare CBN powder, blend these raw powders into the composition shown in Table 1, add acetone as a solvent, mix for 4 hours in a ball mill made of tungsten carbide-based cemented carbide, and then dry. , filled in a stainless steel (JIS/SUS304) tube with dimensions of diameter: 10 mm x height: 10 mm, and while vacuuming, cover both ends of the tube with covers such as JIS/P20 tungsten carbide-based cemented carbide. Welded and sealed, then attached to a known ultra-high pressure and high temperature generator, maximum applied pressure: 60Kb, maximum heating temperature:
The ultra-high pressure sintered materials 1 to 9 of the present invention, which have substantially the same composition as the blended composition, can be obtained by holding and sintering at 1450°C for 10 minutes, cooling, and releasing the pressure. and comparative ultra-high pressure sintered materials 1 to 6 were produced, respectively. The ultra-high pressure sintered materials 1 to 9 of the present invention obtained as a result
All had a dense structure in which diamond, Si carbon/nitride, and CBN were uniformly dispersed. Comparative ultra-high pressure sintered materials 1 to 6 all have compositions in which the content of at least one of the constituent components (marked with * in Table 1) is outside the scope of the present invention. It is something. Next, the above-mentioned ultra-high pressure sintered materials 1 to 9 of the present invention,
Cutting blades were cut by cutting and polishing from Comparative Ultra High Pressure Sintered Materials 1 to 6 and commercially available ultra high pressure sintered materials having the compositions shown in Table 1 whose main component is diamond. , this cutting edge is brazed to a tungsten carbide-based cemented carbide chip using a silver solder,

[Table] Workpiece material: FC30, Cutting speed: 400m/min, Depth of cut: 0.2mm, Cutting oil: Use of water-soluble oil, Cast iron finishing surface machining cutting test under the following conditions, Workpiece material: Al-Si alloy (Contains 30% Si by weight), Cutting speed: 200m/min, Feed: 0.1mm/rev., Depth of cut: 0.2mm, Cutting oil: None. In the cutting test, the cutting time until the flank wear width of the cutting edge reached 0.2 mm was measured. The results of these measurements are shown in Table 1. From the results shown in Table 1, the ultra-high pressure sintered materials 1 to 9 of the present invention all have significantly superior toughness and heat resistance compared to commercially available ultra-high pressure sintered materials, and are equivalent to these. commercially available ultra-high pressure sintered materials lack toughness and heat resistance, and exhibit extremely long cutting times due to their excellent toughness and heat resistance and equally good wear resistance. It is clear that due to this, only a relatively short cutting time is exhibited. Furthermore, as seen in Comparative Ultra-High Pressure Sintered Materials 1 to 6, if the content of at least one of the constituent components falls outside the scope of the present invention, the toughness, heat resistance, and wear resistance may deteriorate. Since at least one of the properties is inferior, it does not exhibit the desired cutting performance and exhibits only a relatively short cutting time. As mentioned above, the ultra-transparent high-pressure sintered material of the present invention has excellent toughness, heat resistance (high-temperature oxidation resistance), and wear resistance, so it is particularly suitable for use as a material for cutting tools. This results in excellent cutting performance.

Claims (1)

[Claims] 1 Diamond: 50-85%, One or both of silicon carbide and silicon nitride: 5-40%, Cubic boron nitride and inevitable impurities: 10-45
%, an ultra-high pressure sintered material for cutting tools having excellent toughness and heat and wear resistance, characterized by having a composition (volume %) consisting of: