JPH09201703A - center - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to install a diamond sintered body to the tip of a shank by a soldering, and to obtain a center having an excellent jointing strength of the diamond sintered body, and an excellent anticorrosion property of the center. SOLUTION: In a center formed by installing a diamond sintered body 2 to the tip of a shank 1, a cylindrical metal member 3 with bottom for diamond sintered body jointing is provided between the shank 1 and the diamond sintered body 2, the diamond sintered body 2 and the metal member 3 are fixed by an active metal soldering method, and furthermore, the metal member 3 is fixed to the shank 1 by a soldering method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a center used for a lathe, a cylindrical grinder or the like and used as a centering jig for a work material.

[0002]

2. Description of the Related Art Especially in lathes and grinders capable of various processing such as grinding and cutting, it is important to accurately center a work piece. A metal center formed of a super hard metal such as is used. The tip of this center is easily worn because a strong force is intensively applied during cutting or grinding, and the wear of this center tip causes a shift in the center position of the rotating body.
This is also a major factor that reduces the processing accuracy. For example, in the case of a center in which a cemented carbide is attached to the tip of a shank, re-polishing is required about every 10 days in order to maintain good processing accuracy with a roundness of 3 μm or more.

As a measure against this, as described in 8.4.2 Machine Tools Abrasion-Resistant Tools (P646-647) in "New Machining Tool Encyclopedia" published by Encyclopedia Publishing Co., Ltd., A convex center in which a convex diamond sintered body (hereinafter referred to as PCD) is fitted at the tip of the shank, and a concave notch is provided at the tip of the shank, and a PCD is similarly provided at the peripheral edge of the notch. The attached concave center has been put to practical use.

[0004]

When attaching PCD to a shank made of such a steel material, diamond and silver solder, which are the main components of PCD, cannot be directly bonded.
The brazing method used to attach the grinding bit to the base metal cannot be applied. For this reason, conventionally, a mechanically fixed caulking method, a sintering method using a metal powder, and the like have been adopted.

However, in such a caulking method and a sintering method using a metal powder, since the PCD and the joining base material are not chemically joined, it is difficult to ensure sufficient joining strength in either case. There is a problem that the PCD easily comes off during use. Further, in the case of the caulking method, it is extremely difficult to accurately determine the center position of the PCD, which is a major impediment factor for popularizing the center using the PCD excellent in abrasion resistance.

The problem to be solved in the present invention is to provide a PCD at the center where the PCD is attached to the shank tip.
The purpose of this invention is to provide a highly reliable center by making it possible to apply a brazing technique excellent in joining strength as the joining method of No.

[0007]

In order to solve the above-mentioned problems, the present invention provides a bottomed cylindrical metal member for joining PCD between the shank and the PCD in the center where the PCD is attached to the tip of the shank. The PCD and the metal member were fixed by the active metal brazing method, and the metal member was fixed to the shank by the brazing method.

That is, the present invention is characterized in that a metal member for PCD bonding is interposed between the shank and the PCD, and the PCD and the metal member are bonded by the active metal brazing method.

By using a brazing material containing an active metal for brazing and joining the PCD and the metal member,
It becomes possible to join D and the shank through the intermediate member by a known silver brazing method. Further, by forming an alloy between the PCD and the brazing material, it becomes possible to chemically bond the PCD and the brazing material, and it becomes possible to join the PCD and the metal member by brazing, which has been difficult in the past.

PCD can be produced by a conventional method. For example, when it is used as an abrasion resistant tool, a diamond powder having a diameter of 25 to 50 μm is filled in a capsule together with a metal medium to produce diamond.
It can be obtained by sintering under the conditions of 500 ° C. and 50,000 atm. At that time, for the center, a cylindrical capsule is filled with diamond powder at the time of sintering to form a predetermined shape.

Further, as a metal member for PCD bonding,
Kovar, molybdenum, cemented carbide, etc. can be used, but especially from the viewpoint of workability, Kovar (kovo)
r) can be preferably used. This Kovar is an alloy of 53% iron, 28% nickel, and 18% cobalt, and has a coefficient of thermal expansion almost equal to that of PCD.
When the brazing material melts at a temperature of ℃ or more, the thermal expansion amount becomes almost equal to that of PCD. As a result, even if the temperature decreases and heat shrinks after joining, the shrinkage amount is the same, so that brazing stress rarely remains.

Further, the active metal (rea) in the silver solder is
As the active metal, titanium or tantalum can be preferably used. The content of active metal is
Although it varies depending on the type of brazing material and brazing conditions, when silver is used as the main material and titanium is used as the active metal, it is preferably 2 to 5% by weight of the silver brazing. If it is less than 2% by weight, the bonding area will be too small, and if it exceeds 5% by weight, the silver brazing strength will decrease.

Further, as a condition for brazing the PCD and the metal member, in order to prevent the active metal from being alloyed by the melting temperature of the silver solder, the atmosphere is argon inert gas or 5 × 10 5. ^It is desirable to have a vacuum state of ^-5 Torr or more.

[0014]

1 is a front view of a center showing an embodiment of the present invention, and FIG. 2 is an enlarged sectional view of a portion A in FIG.
FIG. 3 is also an exploded perspective view of the main part.

Reference numeral 1 is a tapered shank made of carbon tool steel, 2 is a PCD having a diamond grain size of 25 μm provided at the tip of the shank 1, and is formed in a cylindrical shape of φ10 × 15 ^L and the tip angle θ is 60 to 90 °. Has been done. As clearly shown in FIGS. 2 and 3, a cylindrical recess 1a is cut out at the tip of the shank 1, and a metal member 3 for mounting the PCD 2 is provided in the recess 1a.

The metal member 3 is made of Kovar and has an outer diameter smaller than the inner diameter of the recess 1a of the shank 1 by 0.2 mm, and has a bottomed cylindrical shape with a recess 3a for accommodating the PCD 2 formed in the upper portion. Is.

Between the PCD 2 and the recess 3a of the metal member 3,
It is joined to the silver solder by an active metal solder 5 containing 2% by weight of titanium, and the metal member 3 and the recess 1 of the shank 1 are joined together.
The area a is joined by a conventionally known silver solder 6.
In these joining procedures, the PCD 2 is first joined to the metal member 3, and then the metal member 3 is joined to the recess 1 a of the shank 1. As a result, it becomes possible to join the PCD 2 and the metal member 3 in a narrow space.

The brazing temperature is 700 to 800 ° C. for PCD brazing and 600 to 7 for metal member brazing.
The temperature is set to 00 ° C., the PCD brazing is performed in an argon inert gas atmosphere or in a vacuum state of 5 × 10 ⁻⁵ Torr or more, and the metal member brazing is performed in the atmosphere.

In order to confirm the effect of the present invention, the convex center manufactured by the above method and the center in which the PCD of the same shape is fixed to the shank by the conventional caulking method and the metal powder sintering method are actually made of chromium. Used for grinding a compressor rotor, which is a hardened material of molybdenum steel.

As shown in Table 1, in the center of the present invention,
When a center with a PCD runout of 0.005 mm or less and a PCD roundness of 0.003 mm or less is used, it is possible to maintain a high processing accuracy of 2400 hours or more and a compressor rotor roundness of 0.003 mm or less. did it. On the other hand, in the center manufactured by the caulking method,
The processing accuracy was 0.003 mm or more in time, and the processing accuracy of the center manufactured by the metal powder sintering method was 0.003 mm or more in 50 hours, and it was difficult to maintain the processing accuracy.

[0021]

[Table 1]

In the above description, a so-called convex center is described, but it is of course applicable to a concave center.

[0023]

According to the present invention, the following effects can be obtained.

(1) It is possible to attach the diamond sintered body to the shank tip portion by brazing, and it is possible to obtain a center with excellent bonding strength and wear resistance of the diamond sintered body.

(2) By using Kovar as the metal member for joining the diamond sintered body, the diamond sintered body assembly and the shank can be joined by the conventional silver brazing method.

(3) By using an active metal brazing material containing 2 to 5% by weight of titanium as an active metal, it becomes possible to chemically bond the diamond sintered body and the metal member.

[Brief description of drawings]

FIG. 1 is a front view of a center showing an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a portion A in FIG.

FIG. 3 is an exploded perspective view of a main part of the center.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 shank 1a recess 2 PCD (diamond sintered body) 3 metal member 3a recess 5 active metal wax 6 silver solder

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuro Aiura 210 Takeno, Tanamaru-cho, Ukiha-gun, Fukuoka Noritake Diamond Co., Ltd. Within

Claims (4)

[Claims] 1. A diamond sintered body is attached to the tip of a shank, and a metal member for joining the diamond sintered body is interposed between the shank and the diamond sintered body. A member is fixed to the shank by an active metal brazing method, and the metal member is fixed to the shank by a brazing method. 2. The metal member is any one of kovar, molybdenum, and cemented carbide.
Center listed. 3. The center according to claim 1, wherein the active metal is titanium or tantalum. 4. The center according to claim 1, wherein the metal member has a bottomed cylindrical shape capable of accommodating the diamond sintered body.