JPH07498B2 - Diamond joining method for cutting tools - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for joining diamonds for cutting tools. More specifically, it relates to a method for joining a single crystal diamond at the cutting edge of a diamond cutting tool mainly used for precision cutting and a metal (including an alloy), particularly a method for firmly joining a large diamond to a metal without causing cracks. .

[Prior Art] As a method of fixing a single crystal diamond to a shank (base metal) in a diamond bite, a mechanical method and a brazing method are known. Of these methods,
Generally, mechanical fixing methods such as clamps and stakes are often used. On the other hand, the brazing method is, for example,
After chemically bonding diamond and another metal such as a plate, the metal part of this bonded body is fixed to the shank by a normal brazing method, etc. There is.

The amount of diamond gripping (pressing) required in the mechanical fixing method is not necessary in the brazing method, so that the diamond can be used over the entire surface, which is economical.

The degree of freedom in designing the cutting tool such as rake angle and clearance angle is increased. In addition, it becomes easy to set the crystal orientation on the shank.

Since diamond is chemically fixed, the obtained diamond cutting edge is excellent as a precision cutting tool without rattling or loosening even after long-term use as a tool.

However, only a few methods have been disclosed so far about the brazing method of a single crystal diamond and a metal for a diamond bite, and they have not yet been described in various ways such as the generation of a diamond crack at the time of joining. The current situation is that it has not yet been put to practical use, including the problem of solution. In particular, there is almost no proposal of a practical bonding method for a method of bonding a large diamond, which is likely to cause cracks.

In order to braze single crystal diamond to metal and use it as a diamond tool for cutting tools, of course, when brazing, the bonded body of diamond and metal is repeated on the shank for repolishing etc. It is necessary that cracks do not occur in the diamond even when it is detached and attached, and naturally, it is also necessary that the diamond has sufficient bonding strength to withstand cutting and polishing.

However, there have been several proposals as methods for increasing the strength by focusing only on the bonding strength, but all of these methods bond a relatively small diamond such as a few hundredths of a carat to a fewths of a carat. This is a method that can be used only when cracks hardly occur because the diamond is small. That is, as the size of the diamond increases, the internal strain of the diamond itself, the difference in the coefficient of thermal expansion between the diamond and the other metal, and other factors cause the cracking rate to increase rapidly. If such a crack occurs, even if the bonding itself is good, the obtained diamond cutting edge cannot be used at all, leading to a large economic loss, and the loss increases exponentially with respect to the size of the diamond.

For example, the method disclosed in Japanese Patent Publication No. 55-15860 (hereinafter referred to as the conventional method I) and the method disclosed in Japanese Patent Laid-Open No. 61-4603 are disclosed as a method for bonding single crystal diamond for a diamond bite to a metal. The method described in JP-A-62-148104 (hereinafter referred to as conventional method II) and the method described below in JP-A-62-148104 (hereinafter referred to as conventional method III) are exemplified.

In the conventional method I, a method is used in which the surface of diamond is coated with a sputtered film of Ti, W, Co or the like and a sputtered film of Cu, Ni, Ag or the like, and then brazed to a metal in the atmosphere. However, this method was developed as a method of manufacturing a scriber for semiconductors, not a cutting tool for general cutting tools, and is a technology for bonding diamonds having a size of a few hundredths of a carat. Since there is no possibility that cracks will occur due to bonding in such ultra-small diamonds at all, there is no proposal for preventing cracks from occurring, and this method cannot be applied to the bonding of large diamonds where cracks are likely to occur. Can not.

In conventional method II, Fe, Ni, and C were used to increase the bonding strength with the metal, which was previously insufficient for brazing diamond.
o Sintered alloy of Mo and W containing 0.5% by weight or more of Cu (2% Ni-
2% Fe-W, 2% Fe-2% Ni-1% Cu-Mo, etc.) are used as the partner metal. First joining method is 1100 in vacuum
Join the diamond and the Au-Ta alloy as the intermediate layer at ℃,
Then, two steps of brazing this joined body to the above-mentioned sintered alloy with silver brazing are required. It is known that this conventional method cannot obtain high bonding strength in the case of natural diamond.

In the conventional method III, single crystal diamond is first Mo, W, WC
u, W-Fe-Cu, W-5% (Ni-Cu) and other metal pieces are joined together. Diamond and the above-mentioned metals are used so that this joined body can be brazed to a shank with general-purpose silver braze or copper braze. The brazing filler metal between the pieces is limited to a special gold-based brazing filler metal (Au-Ta) having a high melting point (1000 ° C or higher), so that the joining temperature becomes high.

Further, the conventional method II and the conventional method III are both diamond joining techniques of about a fraction of a carat, and as described above, attention is not paid to crack generation prevention.

Thus, until now, no effective method has been known for firmly joining a single crystal diamond to a metal without causing a crack.

[Problems to be Solved by the Invention] The present invention has been made in view of the problems in the conventional diamond bonding method, and bonds single crystal diamond and a metal with practically sufficient strength without generating cracks. The purpose is to provide a method of doing.

[Means for Solving the Problems] The present invention provides 0.5 to 2.5% by weight of Ti and 97.5 to 99.5% by weight of Ag + Cu at 850 ° C. or less in a high vacuum of 5 × 10 ⁻⁴ Torr or less.
(Cu in Ag + Cu is 20 to 35% by weight) and a single crystal diamond and Ni coated plate-like metal such as Mo, W or an alloy of Mo, W (Mo and / or) W and one or more metals selected from the group consisting of Cu, Ni, Co, and Ag, and the total content of the one or more metals is 30% by weight or less). A method for joining diamonds for cutting tools.

The single crystal diamond for a cutting tool used for joining in the present invention may be natural or synthetic. The size of the diamond is not particularly limited, but a strong bond can be achieved without cracking even in a large diamond having a bonding surface area of 10 mm ² or more, which was easily cracked in the conventional method. Therefore, its effect is particularly large.

Further, the thickness of the diamond is not particularly limited, and the effect of the present invention can be obtained without cracking even if the size of the diamond exceeds 1.5 mm or even the size of 2.0 mm or more.

[Operation] It is known that a metal having a small coefficient of thermal expansion, such as Mo, W, or an alloy thereof, is suitable as a metal to be joined with diamond. However, Mo, W, and their alloys as they are have poor wettability with respect to the brazing filler metal, and moreover, uneven wetting occurs, so that cracks are likely to occur. As a result of intensive studies in view of these points, the present invention uses Mo, W or an alloy thereof coated with Ni as a metal of a joining partner of a single crystal diamond, and both of them.
5 to 2.5 wt% Ti and 97.5 to 99.5 wt% Ag + Cu (Ag + Cu
5 × through a bonding material consisting of 20 to 35% by weight of Cu)
By brazing at 850 ° C. or lower in a vacuum of 10 ⁻⁴ Torr or lower, these problems have been solved.

Example According to the method of the present invention, diamond and a Ni-coated metal such as a plate-like metal are bonded with a specific bonding material at a specific vacuum degree and a specific bonding temperature.

The bonding surface of diamond with the metal is not particularly limited, but (110) surface and (100) surface are usually used.

The metal joined to diamond is Mo, W, an alloy of Mo, an alloy of W or an alloy of Mo and W. The alloy is required to have a coefficient of thermal expansion that is not so large, and specifically, one or more metals selected from the group consisting of Mo and / or W and Cu, Ni, Co and Ag. And the total content of the one or more metals is 30% by weight or less. Particularly, the total content of the one or more metals is preferably 25% by weight or less. Above the range,
The coefficient of thermal expansion becomes large, and cracks easily occur in the bonded diamond.

The Ni coating method is not particularly limited, but, for example, electroplating, chemical plating, ion sputter coating, ion plating and the like can be used.

The thickness of the Ni coating layer is preferably 0.1 to 10 μm, particularly preferably 0.5 to 5 μm.

The reason why the occurrence of cracks is suppressed by applying Ni coating on Mo, W or their alloys is that the wettability of the bonding material to Mo, W or their alloys is improved and more uniform bonding can be achieved. As a result, it is considered that the bias of the strain in the bonding layer is reduced.

Besides wettability, another important factor for preventing the occurrence of cracks is temperature. It is easily inferred that the lower the brazing temperature, the more the generation of cracks is suppressed. In the present invention, 0.5 to 2.5 wt% Ti and 97.5 to 99.5 wt% Ag + Cu
(Ag + Cu in Cu in 20 to 35 wt%) is used. These melt sufficiently even at 850 ° C. or lower, and even within a large range, cracks do not occur even with large diamonds.

The bonding material contains 0.5 to 2.5% by weight of Ti. This Ti
By reacting with diamond under the conditions of the present invention to form carbide, a strong bond between diamond and metal is achieved. Therefore, by using the specific bonding material, a relatively low bonding temperature and an amount of active ingredient necessary for bonding can be obtained.

When the amount of Ti in the joining material is less than the above range, it is considered that the amount of Ti sufficient for forming TiC to be the joining layer cannot be obtained and the joining strength is weak. On the other hand, if the Ti content exceeds the above range, the joining material is insufficiently melted, the wettability with respect to the metal is poor, and the joining layer is thick or nonuniform, so that the joining strength is lowered. Further, the Ti content is 0.5
It is preferable that the content is not less than 2.0% by weight and not more than 2.0% by weight from the viewpoint that a low joining temperature and good wettability can be maintained and a sufficient amount can be provided for joining.

Further, when the amount of Cu in Ag + Cu used as the bonding material is less than the above range or exceeds the above range, the melting of the bonding material becomes insufficient at a temperature of about 850 ° C. or less at which the alteration of diamond is not caused. However, the bonding does not occur or even if it does occur, the bonding strength is extremely low.

Regarding the bonding temperature, it is 10 for conventional diamond bonding.
In contrast to the use of temperatures above 00 ° C, the present invention
850 ° C. or lower is sufficient, and since brazing is performed in a vacuum of 5 × 10 ⁻⁴ Torr or lower, it is possible to prevent oxidation and deterioration of diamond in addition to the occurrence of cracks.

Needless to say, the joining temperature must be equal to or higher than the melting temperature of the joining material. Ti and Ag + Cu used in the present invention
The melting temperature of the above-mentioned joining material consisting of and is about 770 to 830 ° C., although it depends on the composition. Therefore, the bonding temperature is about 770 to 850 ° C.

Examples of the present invention will be described below. However, these do not limit the content of the present invention.

Examples 1 to 7 and Comparative Examples 1 to 9 As shown in Table 1, various samples were prepared.

Natural diamond was polished so that the upper and lower parallel planes were (110) planes. The measured values of the area of the bonding surface and the thickness of diamond are as shown in Table 1. As the synthetic diamond, the bonded surface of 4 mm x 1 mm and the thickness of 0.7 mm was used as it was.

Mo plate (10mmφ) with Ni coating of specified thickness shown in Table 1
× 2mm) or W plate (10mm ^□ × 2mm) with a thickness of 0.1 to 0.2
mm thin plate-like bonding materials were stacked, and the diamond was placed thereon. Specifically, the bonding materials used in Examples 1 and 3 to 7 were produced by adding Ti to Ag + Cu containing a predetermined amount of Cu in a predetermined amount, melting and alloying, and then rolling. is there. The thickness of Example 2 is 0.1 mm.
Of Ag-Cu alloy (28% by weight of Cu) was laid on a metal plate, and a Ti foil having a thickness of 5 μm was laid on the metal plate so that Ti was 1.5% by weight, and a diamond was placed thereon. These were placed in a vacuum furnace, heated for 1 hour, kept at 850 ° C. in 5 × 10 ⁻⁴ Torr for 5 minutes, and then cooled for 2 hours.

After observing the crack generation state and the diamond surface state of the obtained bonded body, the shear strength of the bonded body was measured.

Table 1 shows the experimental conditions and the experimental results.

Examples 8 to 10 and Comparative Examples 10 to 13 Instead of the Mo plate or the W plate, a plate of an alloy of Mo and W (10 mm ^□
X 2 mm), various samples were prepared in the same manner as in Example 1 except that they were bonded under the conditions shown in Table 2, and then the surface condition was observed and the shear strength was measured.

Table 2 shows the experimental conditions and the experimental results.

Examples 11 to 14 and Comparative Examples 14 to 17 Next, a large diamond having a bonding area of 10 mm ² or more was bonded. That is, after bonding diamond by the same method as in Example 1 except for the conditions shown in Table 3, the surface state was observed and the shear strength was measured.

Table 3 shows the experimental conditions and the experimental results.

From Tables 1 to 3, high bonding strength can be obtained by bonding diamond according to the method of the present invention.
Moreover, it can be seen that the generation of cracks is also prevented.

When the diamond breaks in the shear test of the bonded body, the bonded surface has higher strength than the diamond itself, which indicates that there is no problem in practical use.

On the other hand, different bonding materials (Comparative Examples 6 to 9),
Those having different degrees of vacuum (Comparative Example 5), those having different joining temperatures (Comparative Examples 1 and 2), those having different mating metals (Comparative Example 12)
13 to 17), and those in which the metal is not coated with Ni (Comparative Examples 3 to 4, 10 to 11 and 14 to 16), cracks may occur or insufficient bonding may be obtained. hand,
None of them could solve practical problems.

As described above, if any one of the bonding material, the degree of vacuum, the bonding temperature, the mating metal and the Ni coating on the metal surface deviates from the scope of the method of the present invention, the above-described effects can be obtained. Absent.

[Effects of the Invention] The present invention provides a practical diamond bonding method for a cutting tool, which makes it possible to bond a single crystal diamond to a metal relatively easily and has the following effects.

The generation of cracks, which has been a problem in the past, is almost completely prevented. This minimizes the loss of expensive material called diamond.

Sufficient bonding strength can be obtained. That is, the bonding surface has a strength equal to or higher than the shear strength of diamond itself, and does not cause rattling or loosening as seen in the mechanical fixing method.
Moreover, the detachment of diamond from the bonded body, which is observed in the conventional brazing method, does not occur at all. Therefore, the diamond bite produced by the present invention has excellent characteristics as a precision cutting tool.

Since the brazing method is used, the area of diamond that can be used as a cutting edge is increased as compared with the mechanical fixing method, which is economically advantageous. In addition, it is possible to design cutting edges of various shapes and expand the range of use of diamond tools.

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Claims (3)

[Claims] 1. 0.5 to 2.5% by weight Ti and 97.5 to 99.5% by weight Ag + at 850 ° C. or less in a high vacuum of 5 × 10 ⁻⁴ Torr or less.
A method for joining diamond for a cutting tool, which comprises joining a single crystal diamond and a metal Mo or W coated with Ni using a joining material composed of Cu (20 to 35% by weight of Cu in Ag + Cu) . 2. 0.5 to 2.5% by weight Ti and 97.5 to 99.5% by weight Ag + at 850 ° C. or less in a high vacuum of 5 × 10 ⁻⁴ Torr or less.
An alloy of Mo and / or W (Mo and / or W, Cu and N, coated with single crystal diamond and Ni, using a bonding material composed of Cu (20 to 35% by weight of Cu in Ag + Cu).
It is composed of one or more metals selected from the group consisting of i, Co and Ag, and the total content of the one or more metals is 30% by weight.
The following) and the joining method of diamond for a cutting tool characterized by joining. 3. The method for joining diamond for a cutting tool according to claim 1 or 2, wherein the size of the single crystal diamond is such that the area of the joint surface with the metal is 10 mm ² or more.