JPS6411703B2 - - Google Patents

Description

[Detailed description of the invention]

Currently, wire drawing dies, non-ferrous metal plastics,
70% diamond by volume for cutting ceramics
Sintered bodies exceeding 100% are commercially available. Among these, sintered bodies with fine diamond grains have been well received, especially when used in dies for drawing relatively soft wire materials such as copper wire, as the wire surface after drawing is extremely smooth. However, at present, there is no diamond sintered body that has a satisfactory performance when drawing a wire with high hardness, such as a brass-plated high carbon steel wire. Furthermore, when these commercially available diamond sintered bodies are used as ceramic cutting or drilling tools, the sintered bodies made of fine diamond particles have a problem in wear resistance, and the sintered bodies made of coarse diamond particles have problems with wear resistance. The concretions are lost and cannot withstand these uses. The present invention relates to a diamond sintered body that can be used to draw high-strength wire rods by improving the above-mentioned drawbacks of the diamond sintered body, and can also be used as a ceramic cutting or drilling tool. First, in order to investigate the reason why high-strength wire rods are drawn using commercially available diamond sintered bodies, three types of diamond sintered bodies with particle sizes of 30 to 60 μm, 2 to 6 μm, and 1 μm or less were examined. A die was made using a dies, and the brass-plated steel wire was drawn. As a result of observing the wire surface and the inner surface of the die when the die reached the end of its life, it was found that all the dies had vertical scratches and were rough on the inner surface, and the surface of the drawn wire also showed
This scratch was transferred. The size of the scratch is 1-3μm
It was a very deep wound. The reason why such scratches occur on the inner surface of the die can be estimated as follows. The diamond sintered bodies used all have diamond particles firmly bonded to each other to form a diamond skeleton, but the grain size was 30.
The ~60 μm diamond sintered body is shown in Figure 1. At the reduction part 1 where the wire and die begin to come into contact, the diamond skeleton part and the edges of the diamond particles break and fall off, scratching and damaging the inner surface of the die. It seems that it was Also 2~
Rather than the diamond skeleton being damaged in the reduction part of the die, the 6μm diamond sintered body is thought to have been damaged by diamond particles of about 2μm falling off and damaging the inner surface. On the other hand, in the case of a sintered body made of diamond particles of 1 μm or less, at the same time as individual diamond particles fall off, several clusters of diamond particles fall off, causing large scratches as well as minute scratches on the inner surface of the die, and these scratches cause the wire surface to It is thought that it was attracted. As mentioned above, the reason why conventional diamond sintered bodies cannot be used is that the diamond skeleton part is damaged or the diamond particles fall off, causing scratches on the inner surface of the die, and these scratches are transferred to the wire surface. However, we will discuss the causes of defects in the diamond skeleton and the falling off of diamond particles. During wire drawing, vertical force and frictional force are applied to the inner surface of the die by the wire rod. Normally, shear force and principal stress occur when normal force and frictional force act between solid contact surfaces. For example, on the inner surface of the die 5 shown in FIG.
The maximum shearing force occurs near the intersection of the bearing part 2 and the back relief part 3, where . Note that 4 is an approach section. In particular, when a high-strength wire is drawn, the normal force and frictional force increase, and the maximum principal stress and maximum shearing force increase. The diamond skeleton portion of the diamond sintered body contains impurities such as catalytic metals, so it is the part with the lowest strength in the sintered body. When principal stress or shear stress is applied to this part, concentrated stress is applied to the parts of the skeleton part that contain impurities. In particular, it is thought that in the reduction part 1, repeated stress is applied due to fluctuations in the contact part with the wire, causing the crack to develop and break. In the case of a sintered body with large diamond particles of 30 to 60 μm, as mentioned above, the maximum principal stress occurs near the surface of the reduction part, so the skeleton part around the diamond particle is not completely destroyed, but the skeleton part near the surface layer Only the part is destroyed first and falls off. Large diamond particles themselves are difficult to fall off. On the other hand, diamond sintered bodies with a diameter of 2 to 6 μm and diamond sintered bodies with a diameter of 1 μm or less have small diamond particles, so the skeleton portion is also small, and even if the skeleton portion is broken and falls off, almost no scratches will occur on the inner surface of the die. However, since the entire skeleton around the diamond particles is destroyed, one or several diamond particles may fall off in groups, which is thought to have caused large scratches on the inner surface. In order to overcome the above-mentioned drawbacks of conventional sintered bodies, it is necessary to prevent diamond particles from falling off and to suppress large defects in the diamond skeleton portion. In order to prevent the diamond particles from falling off, the particle size of the diamond particles should be set to several micrometers or more as mentioned above, but if a large diamond skeleton exists, the skeleton part will be damaged, so the material must not form a large diamond skeleton. Must be. As a binder, if the adhesion with diamond is poor, the diamond particles will fall off even if diamond particles of several micrometers or more are used, and if a binder with poor wear resistance is used, only the tip of the binder part will fall off. This causes the diamond particles to fall off during wire drawing.
Therefore, the properties required for the bonding material are good adhesion to diamond and excellent wear resistance. Also, it is preferable that the skeleton portion, which is relatively easy to fall off, has a small area. Taking the above into consideration, we made prototypes of various materials and examined them. As a result, we found that diamond particles with a particle size of 3 μm or more, preferably 10 μm or more, and diamond particles with a particle size of 1 μm or less, preferably
Diamond particles less than 0.5 μm and periodic table 4a,
It has been found that a sintered body using a binder consisting of carbides, nitrides, borides, solid solutions or mixture crystals of Groups 5a and 6a, and iron group metals exhibits excellent performance. The reason why the sintered body of the present invention has excellent performance is presumed as follows. In other words, since the binding material of the sintered body used in the present invention is made of fine particles of 1 μm or less, it does not form skeletons between large diamond particles, and the inner surface of the die is pulled due to chipping or falling off of the diamond skeletons, resulting in deep large particles. Will not cause any damage. In addition, diamond particles and diamond particles of 1 μm or less contained in the binder are bonded, and carbides of groups 4a, 5a, and 6a of the periodic table,
It is thought that diamond particles do not fall off because diamond has a good affinity with nitrides, borides, and iron group metals (Fe, Ni, Co). Furthermore, the binder contains diamond particles with a fine particle size of 1 μm or less, and the binder has excellent wear resistance, so the binder does not wear abnormally during wire drawing. When the sintered body of the present invention is processed into a die, the wear resistance of the joint is excellent, but it is inferior to coarse diamond particles of 10μ or more, so the joint is slightly depressed compared to coarse diamond particles. Become. If wire is drawn in this state, the load applied to the diamond part will increase, but
Since the load applied to the bonding material is reduced, the fine diamond particles at the bonding part do not fall off in groups, and are less likely to damage the inner surface of the die. In the present invention, diamond particles with a particle size of 3 μm or more account for 20 to 85% of the volume, and the remainder is ultrafine diamond particles with a particle size of 1 μm or less, which account for 20 to 95% of the volume. Diamond sintered bodies for tools made of a binder composed of carbides, nitrides, borides, solid solutions or mixture crystals of the elements and iron group metals, diamond powder of 3 μm or more, ultrafine diamond powder of 1 μm or less, A mixed powder of iron group metal powder and one or more of carbides, nitrides, borides of elements in groups 4a, 5a, and 6a of the periodic table of 1 μm or less in size and solid solution powders of these is prepared and processed in an ultra-high-pressure and high-temperature device. The present invention relates to a method for manufacturing a diamond sintered body for tools having the above structure, which comprises hot pressing under high temperature and high pressure where the diamond is stable. The particle size of the diamond in the sintered body of the present invention is 3 μm or more, but the upper limit is not particularly limited, but it is generally 1 mm or less, and such diamond particles account for 20 to 85%, particularly 50 to 70%, of the volume.
occupies Furthermore, the particle size of diamond particles in the binder is generally 1 μm or less, preferably 0.5 μm or less (the lower limit is about 0.1 μm), and such diamond particles account for 20 to 95% of the binder by volume.
In particular, it accounts for 50-80%. In particular, when the sintered body of the present invention is used for wire drawing dies, the particle size of the diamond particles is preferably 10 μm or more. If the diameter is less than 10 μm, diamond particles will fall off and damage the inner surface of the die.
The content of diamond particles larger than 10μm is 20-85% better in volume. If the content of diamond particles of 10 μm or more is less than 20% by volume, the amount of binder increases, the load applied by the binder increases, and the diamond particles in the binder become agglomerated and fall off. Damage to the inside of the die. Moreover, when the amount exceeds 85% by volume, diamond particles of 10 μm or more come into contact and form a large diamond skeleton, which breaks during wire drawing and falls off, causing deep scratches on the inner surface of the die. The particle size of fine diamond in the binder is
If it exceeds 1μm, it may cause large deep scratches on the inner surface of the die if it falls off, or it will not be distributed uniformly in the binder, so it is better to set it below 1μm. Preferably, the average particle size is 0.5 μm or less. In addition, the content of these fine diamond particles is 20 to 95% in terms of capacity in the binder.
% is preferred. The content of fine diamond particles is
If it is less than 20% by volume, the wear resistance of the binder will be poor and it will wear out early, causing diamond particles to fall off. On the other hand, if the content of fine diamond particles exceeds 95% by volume in the binder, the binder becomes brittle or contains carbides, nitrides, borides, etc. of groups 4a, 5a, and 6a of the periodic table. As the amount decreases, diamond particles of 1 μm or less grow, making it impossible to achieve the targeted performance of the sintered body of the present invention. Grain growth of fine diamond occurs under high temperature and high pressure conditions where diamond is stable, and when there is a liquid phase of iron group metal that dissolves the diamond, and this is due to this melt precipitation phenomenon. The most effective means to suppress this grain growth is to mix in fine powders of carbides, nitrides, and borides belonging to groups 4a, 5a, and 6a of the periodic table, as previously proposed by the present inventors. good. In particular, among the carbides of groups 4a, 5a, and 6a of the periodic table, WC or (Mo, W)C having the same crystal system as WC
had the greatest grain growth inhibiting effect. Next, we investigated the reason why commercially available diamond sintered bodies cannot be used as ceramic cutting or drilling tools.
First, we created commercially available cutting tools for cutting sintered diamond bodies with different diamond particle sizes, and used them to cut granite. As a result, it was found that a sintered body made of fine diamond particles with a particle size of 1 μm or less had a problem in wear resistance because the cutting edge became rounded in the early cutting stage. On the other hand, when the particle size of the diamond particles becomes coarse (10 μm or more), although the wear resistance is excellent, the cutting edge breaks during cutting, making it unusable. The reason for this can be inferred as follows. The transverse rupture strength of a diamond sintered body decreases as the grain size increases. The fine-grained diamond sintered body has a high transverse rupture strength and excellent toughness, so the cutting edge will not break. However, since each particle is held by a small skeleton, the bonding force between the individual particles is weak. Therefore, individual particles tend to fall off during cutting, which is thought to result in poor wear resistance. On the other hand, coarse-grained diamond sintered bodies are held by a large skeleton, and the bonding force between individual diamond particles is strong, so they have excellent wear resistance, but because the skeleton is large, once a crack occurs, it will propagate. It is thought that the cutting edge is easily damaged and the cutting edge is damaged. A diamond sintered body that can be used for these purposes must have excellent wear resistance and high toughness. To achieve this, it would be possible to create a sintered body that has the same material as the diamond sintered body for dies, that is, a sintered body that has both the good wear resistance of a coarse-grained diamond sintered body and the high toughness of a fine-grained diamond. Considering this to be a good idea, we investigated the composition of the sintered body. As a result, 20-85% by volume of diamond particles of 10 μm or more are contained, and the remainder is 20-95% by volume of diamond particles of 1 μm or less.
It has been found that a sintered body using a binder consisting of group 6a carbides, nitrides, borides, solid solutions thereof, or mixture crystals and iron group metals exhibits excellent performance. Since the sintered body of the present invention contains diamond particles of 10 μm or more, it has extremely excellent wear resistance. Especially when abrasion resistance is required,
It is possible to increase the content of diamond particles of 10 μm or more, but if this content exceeds 85% by volume in the sintered body, the cutting edge is likely to break. If toughness is required, the content of diamond particles of 10 μm or more can be reduced, but if the content is less than 20% by volume, wear resistance becomes a problem. If the particle size of the coarse diamond particles is less than 10 μm, there will be a problem in wear resistance, so it is better to have a particle size of 10 μm or more. The particle size of the fine diamond particles is preferably 1 μm or less, preferably 0.5 μm or less. When the particle size of fine diamond particles exceeds 1 μm, toughness decreases. The content of fine diamond particles in the binder is preferably 20 to 95% by volume. If the content of fine diamond particles is less than 20%, the wear resistance of the binder phase decreases, the binder phase wears out early, and coarse diamond particles fall off. On the other hand, if the content of fine diamond particles exceeds 95%, the binder becomes brittle or
As the content of carbides, nitrides, borides, etc. of groups 4a, 5a, and 6a decreases, diamond grains of 1 μm or less grow and the toughness decreases. Further, since the sintered body of the present invention has high toughness, it is also effective in cutting non-ferrous metals having interrupted portions. In particular, if good surface roughness is required, the roughness of the diamond particles may be made finer, but if the roughness is less than 3 μm, problems may arise in wear resistance depending on the type of material being cut. Therefore, in the case of such uses, it is preferable that the diamond in the binder part has a particle size of 1 μm or less, and the diamond as the wear-resistant component has a particle size of 3 μm or more. The diamond raw material powder used in the sintered body of the present invention includes diamond particles of 3 μm or more and micron powder of 1 μm or less, preferably 0.5 μm or less. Either synthetic diamond or natural diamond may be used. This diamond powder, one or more of the above compound powders, and iron group metal powders of Fe, Co, and Ni are uniformly mixed using a means such as a ball mill. This iron group metal may be infiltrated during sintering without being mixed in advance. In addition, the inventors' earlier application (Japanese Patent Application No. 52-
No. 51381), the pots and balls in a ball mill are mixed with compounds such as carbides and sintered bodies of iron group metals, and at the same time as the diamond powder is ground in the ball mill, the compounds such as carbides and iron group metals are mixed into the pots and balls. There is also a method of mixing fine powder of sintered metal. The mixed powder is placed in an ultra-high-pressure device and sintered under conditions where the diamond is stable. At this time, it is necessary to sinter at a temperature higher than the temperature at which a eutectic liquid phase appears between the iron group metal and the compound such as carbide used. For example, when TiC is used as the compound and Co is used as the iron group metal, a liquid phase occurs at about 1260°C under normal pressure.
It is believed that this eutectic temperature increases by several tens of degrees Celsius under high pressure. Therefore, in this case, sintering is performed at a temperature of 1300°C or higher. Although the ratio of compounds such as carbides and iron group metals that serve as binding materials for diamond in the sintered body cannot be unambiguously determined, it is necessary that the amount is at least sufficient for the compound to exist as a solid during sintering. For example, when WC is used as a compound and Co is used as a binding metal, the quantitative ratio of WC and Co must include 50% or more of the former by weight. When the diamond sintered body of the present invention is used to draw a high-strength wire rod, high pressure is generated on the inner surface of the sintered diamond die, but when the diamond sintered body has a small outer diameter and a thin wall thickness, The diamond sintered body may crack in the vertical direction.
In such a case, it is possible to prevent vertical cracking during wire drawing by surrounding the outer periphery of the diamond sintered body with a support such as a cemented carbide and applying preload from the outer periphery of the diamond sintered body. The sintered body of the present invention can be used not only for dies but also for cutting tools and excavating tools. in this case,
In order to further improve the toughness of the diamond sintered body, it is also possible to bond it to a support such as cemented carbide during ultra-high pressure sintering. This will be specifically explained below using examples. Example 1 Synthetic diamond powder with particle size of 0.5 μ and WC and Co
The powders were pulverized and mixed using a pot and ball made of WC-Co cemented carbide. The composition of the obtained mixed powder was 80% by volume of fine diamond with an average particle size of 0.3 μm, 12% by volume of WC, and 8% by volume of Co. This mixed powder and diamond powder having a particle size of 40 μm were mixed in a volume ratio of 4:6. This finished powder is WC-10%Co
It is packed in a container, and the pressure is first applied using an ultra-high pressure device.
55 Kb was added, followed by heating to 1450°C and holding for 20 minutes. When the sintered body was taken out and the structure was observed, Figure 2-
As shown in a, the diamonds with a particle size of 40μ are not bonded to each other and do not form a large diamond skeleton, and there is a binding material around this.
0.5μm diamond particles and WC-Co binder were present. For comparison, commercially available 30~
Figure 2-b shows a photograph of the structure of a diamond sintered body in which diamond particles with a grain size of 60 μm are bonded with Co. This sintered body and commercially available diamond particles with a particle size of 30 to 60 μm were bonded with Co and a hole diameter of 0.175 mm was inserted into the sintered body.
Finished with a φ die. Using these dies, brass-plated steel wire was drawn in lubricating oil at a drawing speed of 800 m/min. A die made from a commercially available diamond sintered body had vertical scratches on the wire surface after 500 kg of wire was drawn, and the life of the die was reached. There were few injuries. Example 2 A binder powder shown in Table 1 was prepared. As the fine diamond, 0.3 μm was used.

【table】

[Table] Finished powders were prepared by mixing this binder and diamond particles with a particle size of 10 μm or more in the proportions shown in Table 2.

[Table] These complete powders were sintered in the same manner as in Example 1, and then finished into a die with a hole diameter of 0.250 mmφ.
Using these dies, brass-plated steel wire was drawn in lubricating oil at a drawing speed of 800 m/min. The results are shown in Table 2. For comparison, a commercially available diamond sintered body and a cemented carbide die were made by bonding diamond particles with a particle size of 30 to 60 μm with Co, and when tested in the same manner, wire drawings of 1300 kg and 300 kg were achieved, respectively. Example 3 Binder powders shown in Table 3 were prepared.

[Table] A finished powder was prepared by mixing this binder powder and diamond particles with a particle size of 10 μm or more in the ratio shown in Table 4. After sintering in the same manner as in Example 1,
Dies with hole diameters of 1.185 mm and 1.2 mm were made. Using these dies, the die with a hole diameter of 1.185 mmφ was used to cut copper-plated steel wire in lubricating oil at a wire speed of 400 m/min.
The die with a hole diameter of 1.2 mmφ was made by drawing stainless steel wire. For comparison, similar experiments were also conducted using a commercially available sintered body in which diamond particles with a grain size of 30 to 60 μm were bonded with Co. The results are also shown in Table 4.

[Table] Example 4 The binder powder prepared in Example 1 and diamond powder having a particle size of 100 μm were mixed in a volume ratio of 35:65.
This completed powder was packed into a container made of Ta and sintered at 55Kb at 1450°C for 20 minutes using an ultra-high pressure device. A cutting tool was created using this sintered body to cut granite at a speed of 30 m/min, depth of cut of 1 mm, and feed rate of 0.5 mm/rev.
A cutting test was conducted using water as the cutting fluid. For comparison, commercially available diamond grain size is approximately 100 μm.
Co-bonded diamond sintered bodies for drilling tools were also tested. As a result, the cutting edge of the sintered body of the present invention was hardly damaged even after cutting for 60 minutes, whereas the cutting edge of the commercially available sintered body was broken after cutting for 10 minutes. Example 5 The binder powder prepared in Example 1 and diamond powder with a particle size of 3μ were mixed in a volume ratio of 60:40, and this powder was packed in a Ta container and ultra-high pressure sintered at 53Kb at 1400℃ for 10 minutes. did. A cutting tool was created using this sintered body, and Al-25%Si was cut at a speed of 300 m/min.
Cutting was performed for 60 minutes at a depth of cut of 0.5 mm and a feed rate of 0.2 mm/rev.
For comparison, diamond particles of 3 to 8 μm were coated with Co
A commercially available diamond sintered body bonded with was also tested. As a result, the work surface cut with the sintered body of the present invention is extremely smooth, and the flank wear width is small.
On the other hand, the surface of the commercially available sintered body was rough, and the flank wear width was 0.05 mm. Example 6 Using the binder powders B, C, D, E, and F prepared in Example 2, finished powders shown in Table 5 were prepared. next

[Table] A disc of WC-10% Co cemented carbide was placed in a Mo container, then filled with these finished powders, and ultra-high pressure sintered in the same manner as in Example 1. All diamond sintered bodies were bonded to WC-Co cemented carbide. In order to explore the potential of using these diamond sintered bodies as drilling tools, we created cutting tools and tested their compressive strength.
A wet cutting test was conducted on 1400 kg/cm ² andesite at a speed of 45 m/min, depth of cut of 0.5 mm, and feed rate of 0.2 mm/rev for 30 minutes. For comparison, a similar experiment was conducted using a commercially available diamond sintered body in which diamond particles with a grain size of 100 μm were bonded with Co. The results are also shown in Table 5.

[Brief explanation of the drawing]

Figure 1 is a conceptual diagram showing the contact state between the wire and the die during wire drawing, and Figures 2 a and b are microscopic photographs showing the structures of the sintered body of the present invention and the commercially available sintered body with a diamond grain size of 30-60 μm, respectively. It is.

Claims (1)

[Claims] 1. Diamond particles with a particle size of 3 μm or more in a capacity of 20
~85% of the diamond particles, and the remainder is 20~95% by volume of ultrafine diamond particles of 1 μm or less, and carbides, nitrides, borides of groups 4a, 5a, and 6a of the periodic table of 1 μm or less, or solid solutions thereof. A diamond sintered body for tools made of a binder made of mixed crystals and iron group metals. 2. Diamond particles with a particle size of 10μm or more have a capacity
The average particle size of ultrafine diamond particles and carbides, nitrides, borides of Groups 4a, 5a, and 6a of the periodic table, or solid solutions or mixtures thereof, is 0.5 μm or less, accounting for 20 to 85% of the total A diamond sintered body for a tool according to claim 1. 3. Periodic table No. 1 used as part of the binding material in the sintered body according to claim 1 or 2
A diamond sintered body for tools, characterized in that the ratio of carbides of groups 4a, 5a, and 6a to iron group metals is higher than that corresponding to its eutectic composition. 4 The carbide used as part of the binder is WC or (Mo, W)C having the same crystal structure as WC.
Claims 1 and 2 are characterized in that:
Or the diamond sintered body for tools according to item 3. 5 Diamond powder of 3μm or more, ultrafine diamond powder of 1μm or less, periodic table diamond powder of 1μm or less
A mixed powder of iron group metal powder and one or more of group 4a, 5a, and 6a carbides, nitrides, borides, and solid solution powders of these is prepared, and then heated to a high temperature where diamond is stable using an ultra-high pressure and high temperature equipment. Characterized by hot pressing under high pressure, diamonds of 3 μm or more account for 20-85% by volume, and the remainder is 20-95% by volume of diamonds of 1 μm or less, which are diamonds 4a and 5a of the periodic table of 1 μm or less. A method for producing a diamond sintered body for tools, which is made of a binder made of group 6a carbides, nitrides, borides, solid solutions or mixture crystals thereof, and iron group metals. 6 Diamond powder of 10μm or more, average particle size
0.5μm ultra-fine diamond powder and periodic table number
It uses one or more raw materials of carbides, nitrides, borides, and solid solutions of metals in Groups 4a, 5a, and 6a, and diamond particles with a particle size of 10 μm or more account for 20 to 85% of the volume, and are used as a binder. The tool according to claim 5, wherein the average particle diameter of the ultrafine diamond particles and carbides, nitrides, borides of groups 4a, 5a, and 6a of the periodic table, or solid solutions or mixtures thereof is 0.5 μm or less. A method for producing a diamond sintered body for use. 7. In the manufacturing method according to claim 5 or 6, the ratio of carbides of Groups 4a, 5a, and 6a of the periodic table and iron group metals used as part of the binder-forming powder is determined by the eutectic composition. Diamond sintering for tools is characterized by using a mixed powder with a larger amount of carbide than comparable products, and sintering at a temperature higher than the eutectic formation temperature of carbide and iron group metal while suppressing the grain growth of ultrafine diamond. Method for producing solids. 8. A diamond sintered body for tools according to claim 5, 6 or 7, characterized in that the carbide used as the binder is WC or (Mo, W)C having the same crystal structure as WC. Production method.