JPS5896848A - High hardness sintered body for tool and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a high-hardness sintered body for a tool with superior wear and welding resistances by mixing a specified percentage of diamond particles having a specified particle size with a specified percentage of a binder composed of hyper-fine diamond particles, carbide or the like of a specified metal and an iron group metal. CONSTITUTION:A sintered body is manufactured using a powdered mixture consisting of 20-85vol% diamond particles having 3-10mum particle size and the balance binder. The binder is composed of 20-95vol% hyper-fine diamond particles having <=1mum average particle size, carbide, nitride or carbonitride of a IVa, Va or VIa group transition metal in the periodic table, a solid soln. or a crystal mixture thereof having <=1mum particle size, and an iron group metal. The powdered mixture is hot pressed at high temp. and pressure at which diamond is stable with a superhigh pressure and high temp. apparatus. The resulting signtered body shows superior wear and welding resistances.

Description

[Detailed Description of the Invention] Currently, diamond is used as a bonding material for cutting non-ferrous alloys, plastics, and ceramics in an amount exceeding 70% by volume.
There are commercially available tool materials in which a sintered body part made of metal as a main component is bonded onto a cemented carbide base material. Although this tool material is expensive, A1 contains a lot of Si.
It is popular as a cutting tool for some alloys and high hardness copper alloys.

The present inventors also conducted various investigations into the characteristics of this tool material. They realized that the material had much higher wear resistance than the conventionally used cemented carbide, and that the main component was diamond, and that the diamond crystals formed a skeleton structure in which they were adjacent to each other. Even such an excellent diamond sintered body has various drawbacks.

First, although it has the advantage of being highly abrasion resistant, it has the disadvantage of being expensive and, furthermore, being heavy and requiring very high re-grinding costs.

Since this tip itself is expensive, it is not possible to use the throw-away method, which is currently the mainstream for cemented carbide, and to discard it without re-grinding it when it wears out.

When we conducted a re-grinding test based on this idea, we found that the re-grinding efficiency was extremely low, as it was like dressing a diamond grinding wheel rather than grinding, and the wear of the grinding wheel was extremely high. Got it 0 The second drawback is that, for example, when observing the machined surface when cutting nonferrous alloys, the surface viscosity is rougher than that of natural diamond single stone tools, and a beautiful finished surface called a mirror surface cannot be obtained. When cutting small or thin workpieces such as watch parts, there are problems such as large cutting resistance, deformation of the workpiece, and inability to maintain dimensional accuracy. As mentioned above, the diamond crystals are bonded together to form a skeleton structure, and the diamond particle size is 5 to 8, with CO present as a binder between the particles. When observing the cutting edge of a nokuite using this sintered body, it is found that there are irregularities that are approximately the size of crystal grains, and the cutting edge is not as sharp as that of a natural diamond tool. This is considered to be one of the reasons why it is difficult to obtain a beautiful finished surface. Further, the metal CO binding phase existing between the diamond particles may cause adhesion with the metal to be stiffened, which becomes a problem when a mirror-like finished surface is required. In order to solve these problems, one of the present inventors developed a sintered body with a reduced content of diamond particles and a sintered body made of diamond particles of 1μ or less, and filed a patent application (Japanese Patent Application Laid-Open No. 136790, Japanese Unexamined Patent Publication No. 55-71671) It is true that these materials have improved grindability or excellent cutting edge sharpness, but depending on the workpiece material, wear resistance and welding resistance may be poor. The inventors of the present invention have conducted extensive research in order to develop a material that has good grindability or a sharp cutting edge, as well as excellent wear resistance and welding resistance. .

As a result, the capacity of diamond particles of 3 μm or more was 20
% or more and 85% or less, and the remaining binder is 20 to 95% by volume, ultrafine diamond particles with an average particle size of 1 μm or less,
Periodic Table 4a and 5a.

In FIG. 2, carbide, carbonitride, nitride or solid solution or mixture crystals of group 6a transition metal,
2 is a tool material, 2 is a diamond particle, 3 is a binding material containing ultrafine diamond, 4 is a grindstone, and 5 is a diamond crystal in the grindstone.

They discovered that sintered bodies made of iron group metals such as iron, cobalt, and nickel achieve this goal.

First, the reason why the sintered body of the present invention has excellent grindability is considered to be as follows. FIG. 1 is a typical microscopic photograph of the structure of the sintered body of the present invention. There are carbides, nitrides, carbonitrides and iron group metals. When this sintered body is ground, as shown in Figure 2, a sharp diamond abrasive blade comes into contact with it, but there is a bonding material part that is easier to grind than the diamond crystal, and this part is ground, so it is 5 μm in diameter. Compared to the sintered body whose skeleton is composed of the above diamond crystals,
It is thought that the grindability is improved. Next, we will discuss the reasons why the blade has excellent sharpness. Commercially available sintered bodies are made of diamond particles of 3 to 8 μm in size, and the diamond particles do not have any skeleton structure with each other, and the binding material is CO. As mentioned above, the binding material, CO, is easily removed, so the crystals do not form. There are irregularities on the cutting edge that are approximately the same size as the particles. - Since the Shiki invention sintered body contains fine diamond particles in the binder, it is not removed like when CO is the binder, but forms part of the cutting edge. Therefore, the cutting edge has few irregularities and is considered to have excellent sharpness.

Furthermore, the strength of the diamond sintered body decreases as the grain size increases, as shown in FIG.

Fine-grained diamond sintered bodies have high transverse rupture strength and excellent toughness, so the cutting edge will not break, but since each particle is held by a small skeleton, the bonding force between individual particles is weak. It is thought that wear resistance is poor because individual particles tend to fall off during cutting. 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 is difficult to propagate. , the cutting edge is thought to be damaged. The sintered body of the present invention has a thickness of 3 μm.
Since the diamond particles of 10 μm or less are held in the ultrafine diamond sintered body, the diamond particles of 6 μm or more and 10 μm or less have good wear resistance.
It has the high toughness of an ultra-fine diamond sintered body. Furthermore, since the sintered body of the present invention contains ultrafine diamond particles as a binder and carbides, nitrides, and carbonitrides of groups 4a, 5a, and 6a of the periodic table, it has very high welding resistance. Are better.

The coarse diamond particles used in the sintered body of the present invention have a diameter of 5 μm.
The above is good. When the thickness is less than 3 μm, problems arise in wear resistance. In order to obtain a work surface equivalent to that of single crystal diamond, especially for cutting tools for non-ferrous metals, the diamond grain size is 5 to 1.
If the range of 0 μm exceeds 010 μmk, the roughness of the machined surface becomes poor and the grindability deteriorates. 5μm or more 10μm
It is preferable that the content of diamonds less than m is 20 to 85% by volume. In particular, if wear resistance is required, 5 μm or more 1
It is possible to increase the content of diamond particles with a diameter of 0 μm or less, but if this content exceeds 85 cm in terms of the capacity of the sintered body, the grindability deteriorates and the blade light may be damaged during cutting. In addition, it is possible to reduce the total content, but by 20% by volume.
If it is less than that, wear resistance becomes a problem. The particle size of the ultrafine diamond particles in the binder is 1 μm or less, preferably 0.
．． The thickness is preferably 5 μm or less. When the particle size of the fine diamond particles exceeds 1 μmk, the grindability and toughness decrease. 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 will decrease, and the binder phase will be removed during grinding, making it impossible to obtain a sharp cutting edge, or the binder phase will be removed prematurely during cutting. Worn, 3μm
More diamond particles fall off.

On the other hand, if the content of fine diamond particles exceeds 95%, the binder becomes brittle or
Since the content of carbides, nitrides, borides, etc. of groups A and VIA 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 exhibits its effect even when cutting non-ferrous metals having interrupted portions.

The diamond raw powder used in the sintered body of the present invention is made of diamond particles with Ifi of 3 μm or more and micropowder with Ifi 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 such as Fe, C+), and Nl 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, as disclosed in the inventor's earlier patent application No. 52-51381, the pot and balls used in a ball mill are made of a sintered body of a compound such as a carbide and an iron group metal, and the diamond powder is ground at the same time as the ball mill. There is also a method in which a compound such as a carbide and fine powder of a sintered body of an iron group metal are mixed in from a pot and a ball.

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, TiC is used as a compound, and CO is used as an iron group metal.
When using , a liquid phase occurs at about 1280° 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, which serve as binding materials for diamond in the sintered body, cannot be unambiguously determined, it is necessary to have a small amount (at least enough material for the compound to exist as a solid during sintering). For example, when WC is used as a compound and used as a Co f binding metal, the quantitative ratio of we and CO must be 50% or more, with the former being a heavy burden.

The sintered body of the present invention can be used not only as a cutting tool but also as an excavating tool. 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 explained in detail below using examples.

Example 1 Particle size 0. ．． 5μ synthetic diamond powder and we and co powder fWc-C! o Pulverized and mixed using a cemented carbide pot and ball. The composition of the obtained mixed powder was 80% fine-grained diamond with an average particle size of 0.5 μm, WC
and Co 8 capacity. This mixed powder and diamond powder having a particle size of 3 to 6 μm were mixed in a volumetric ratio of 4:6.

After filling this finished powder into a Ta container with an inner diameter of 10fi and an outer diameter of 14=, WC! −+ A cemented carbide disk with a 0% CO composition was placed. Next, this container is placed in ultra-high pressure sintering,
First, a pressure of 55 Kbi was applied, followed by heating to 1450°C and holding for 20 minutes.

When we took out the 'ra container, removed the Ta f, and observed the structure of the sintered body, we found that diamonds of 3 to 6 μm were uniformly dispersed, and that there was a binder containing ultrafine diamond particles around them. Was. The grindability of this diamond sintered body and a commercially available diamond sintered body bonded with 3-6 μm diamond particles i0o was investigated. If the grindability of the commercially available diamond sintered body is 100, The grindability of the body was 15Ω.

Next, chips for cutting were created using these sintered bodies. Using this, a cutting test of CU alloy was conducted. The work material is a CTL alloy round bar with a diameter of 100fi.
Cutting speed 300 g/min, depth of cut 01, feed 0
．． For comparison, a natural diamond tool cut at o 2 m+/rev was also tested at the same time. The surface to be machined by the sintered body of the present invention was comparable to the surface to be machined by natural diamond, and could be finished to a nearly mirror-like finish, but the commercially available sintered body was far from mirror-like.

Example 2 A binder powder shown in Table 1 was prepared. The ultrafine diamond used was 0.5 μm.

Table 1 This binder and diamond particles with a particle size of 3 μm or more are shown in Table 1.
A finished powder was prepared by mixing in the proportions shown below.

Table 2 After sintering these finished powders in the same manner as in Example 1,
Table 2 shows the results of examining the characteristics to be ground. These results show the amount that can be processed under the same conditions, with the amount that can be processed in a certain amount of time and a certain amount of cut made in a commercially available diamond sintered body having a diamond grain size of 3 to 6 μm being taken as 100. Next, a cutting tip was created using these sintered bodies, and a cemented carbide (WC-15% co ) f U =
10 ml min, d = O12■, f =
Cutting was performed for 10 minutes at 0.2 wI/veu. Table 2 also shows the wear of the exposed surface at this time.

Example 5 The binder powder prepared in Example 1 and diamond powder with a particle size of 3μ were mixed at a total volume ratio of 60:40, and this powder eT
55 Kl in a container made by A).

Ultra-high pressure sintering was performed at 1400°C for 10 minutes. This sintered body was used to create a cutting tool, At-251sil speed 300 mlmin, depth of cut 0.51 WI s feed 0
．． Cutting was performed for 60 minutes at 2 w#/rev. 5 for comparison
A commercially available diamond sintered body bonded with ~8 μm diamond particles 'fr:CO was also tested. As a result, the work surface cut with the sintered body of the present invention was very smooth, with a wear rate of 0.051111 on the reversed surface, whereas with the commercially available sintered body, the cut surface was crumbly and the flank surface was 0.051111. During wear it was 0.05 wm.

[Brief explanation of the drawing]

FIG. 1 is a microscopic photograph of the structure of the sintered body of the present invention. FIG. 2 is an explanatory diagram of the mechanism when the tool material of the present invention is ground with a diamond grindstone. FIG. 5 is a diagram showing the relationship between transverse rupture strength and grain size of a diamond sintered body. i, r
%-7l11a47i+X/1tpo +4 q'
h′)j. Agents 1) Akira’s agent Ryo Hagiwara −

Claims (8)

[Claims] (1) Diamond particles of 3 to 10 μm in a volume of 20
Ultrafine diamond particles having an average particle size of 1 μm or less, containing ~85% binder, and the remaining binder being 20~95% by volume, Nos. 4a and 5a of the periodic table. A high-hardness sintered body for tools comprising carbides, nitrides, carbonitrides, solid solutions or mixture crystals of group 6a transition metals, and iron group metals. (2) The binder is ultrafine diamond particles with an average particle size of 1 μm or less, 20 to 95 volume ratio, periodic table 4a, 5a, 6a
A high-hardness sintered body for a tool according to claim (1), comprising a group transition metal carbide and a ferrous metal. (3) The binder is ultrafine diamond particles with an average particle size of 1 μm or less, 20 to 95 volumes, WC! The high-hardness sintered body for tools according to claim (1) or (2), which is made of (Mo, W)C and a ferrous metal having the same crystal structure as that of (Mo, W)C. (4) Periodic Table 4a used as part of the binding material. High hardness for tools according to any one of claims (1) to (3), wherein the ratio of carbides of group 5a and 6a transition metals to iron group metals is higher than that of the eutectic composition. Sintered body. (5) Diamond powder of 3 to 10 μm, ultrafine diamond powder of 1 μm or less, periodic table 4a of 1 μm or less
, 5a, 6a group transition metal carbide, nitride, carbonitride or solid solution or mixture crystal powder of these, and a mixed powder of iron group metal powder is prepared.
It is characterized by hot pressing under high temperature and high pressure using an ultra-high pressure and high temperature equipment.It contains 20 to 85 parts of diamond particles of 3 to 10 μm in volume, and the remainder is 20 parts of ultrafine diamond particles of 1 μm or less. A tool made of a binder composed of carbides, nitrides, carbonitrides of transition metals of Groups 4a, 5a, and 6a of the periodic table, or solid solution or mixture crystals of these, and iron group metals with a capacity of 1 μm or less A method for producing a high hardness sintered body for use. (6) Diamond powder of 5 to 10 μm, ultrafine diamond powder of 1 μm or less, periodic table 4a of 1 μm or less
, a carbide of group 5a, group 6a transition metals, and a mixed powder of iron group metal. (7) The carbide used as the binder forming powder is WC.
Alternatively, the method for producing a high-hardness sintered body for tools according to claim (5) or (6), using (Mo, W)0 having the same crystal structure. (8) No. 4 of the periodic table used as part of binder-forming powder
Using a mixed powder in which the ratio of carbides of group a, 5a, and 6a transition metals to iron group metal is larger than that corresponding to the eutectic composition, A method for producing a high-hardness sintered body for a tool according to any one of claims (5) to (7), in which sintering is performed while suppressing grain growth of fine-grained diamond.