JP2000061706A - Center - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the manufacturing process of a center and improve durable life due to high hardness and low coefficient of friction by coating the tip of a shank with diamond-like-carbon of high hardness, low coefficient of friction, and no adhesion of worn metal powder. SOLUTION: The tip part of a shank 1 made of high speed steel is coated with an intermediate layer 4 made of tungsten, and it is further coated with diamond-like-carbon 5 of high hardness and low coefficient of friction. The intermediate layer 4 improves adhesion strength between the base material of the shank 1 and the diamond-like-carbon. The material is not limited to be tungsten, and any material capable of improving adhesion can be used. The coefficient of friction of diamond-like-carbon against the other metal is under 0.2, and because it has an effect similar to solid lubricant, it decreases wear. This center has high hardness and low coefficient of friction, and adhesion of the metal powder is not generated to prolong the life.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a center for holding the center of rotation of a workpiece of a turning device, and more particularly to a center having a long service life.

[0002]

2. Description of the Related Art In a turning device for machining a workpiece while rotating the workpiece, a center of the workpiece is held to hold the center of rotation of the workpiece. This center has significant wear due to severe operating conditions such as high-speed rotation and high holding power, and has a short service life.

Most conventional centers use a high-speed steel material that is inexpensive and easy to manufacture. However, due to the large amount of wear, the durability life is short. Although it is expensive for this measure, it is also considered that a hard tip such as a cemented carbide or a diamond sintered body is brazed only at the tip portion.
These are disclosed in JP-A-8-31419 and JP-A-9-8550.
5 is known.

An example of the prior art will be described with reference to FIG.
A hard tip 2 such as a cemented carbide or a diamond sintered body is embedded in a shank 1 having a hole drilled at its tip and brazed with a metal brazing material 3.

When joining different kinds of materials after processing, the joining strength is low, the joining accuracy is low due to the thickness of the brazing material,
Since the brazing temperature is high, peeling and cracking due to thermal strain occur, and many product defects occur. This is because the thermal expansion coefficients of the respective materials differ greatly, and the high temperature during brazing is a major cause. The thermal expansion coefficient is shown in FIG. Two
There is a big difference of 10 times.

[0006] As a solution to this problem, the interposition of a material for relaxing the thermal strain, the fixing from the back surface with a screw, or the like is performed. However, the interposition of the material for relaxing the thermal strain lowers the joining accuracy similarly to the interposition of the brazing material, and requires refinishing after joining, which makes rehardening extremely difficult.
Fixing with screws, etc., also poses the problem of reduced accuracy and the difficulty of drilling holes throughout the shank. In either case, there are drawbacks that the number of manufacturing process steps is large and the process becomes complicated.

The high-speed steel has a Vickers hardness of 9
Although it is 00 Hv, the Vickers hardness is 1800 Hv even when a cemented carbide is used. To improve wear resistance,
Even if a hard tip is used, there is a large coefficient of friction with the work piece, and even a hard tip has a problem that wear progresses. Further, there is a problem that the work piece is worn, and the worn metal powder is adhered to the shank tip or the hard tip to increase the friction coefficient and shorten the life.

[0008]

In a conventional center that considers wear resistance, the problem of complexity of manufacturing process steps is not taken into consideration. Further, reduction of the friction coefficient, which is the root of wear, has not been solved.

The present invention simplifies the manufacturing process of the center,
It is to provide a center with a long life due to its high hardness and low friction coefficient.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has a high hardness, a low friction coefficient, and adhesion of wear metal powder without increasing the number of processing steps during manufacturing. Means were provided to coat the shank tip with no diamond-like carbon.

[0011]

By coating the diamond-like carbon after the final finishing process, the wear resistance can be improved and the durable life can be extended without lowering the shape accuracy.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a center according to the present invention will be described below with reference to FIGS. FIG. 1 shows a first embodiment, in which the tip of a shank 1 made of high speed steel is coated with an intermediate layer 4 made of tungsten and coated with diamond-like carbon 5 having a high hardness and a low friction coefficient. The intermediate layer 4 plays a role of improving the adhesion strength between the base material of the shank 1 and the diamond-like carbon.

A second embodiment is shown in FIG. A cemented carbide tip 2 which is harder than the shank material is embedded in a shank 1 made of high speed steel with a hole drilled at the tip, and a metal brazing material 3 is used.
Brazing, final finishing, coating of the intermediate layer 4 made of tungsten, and coating of diamond-like carbon 5 having high hardness.

The material of the intermediate layer 4 is not limited to tungsten, but may be any material that can improve the adhesion. Further, the intermediate layer 4 may be formed by laminating a plurality of materials.

Diamond-like carbon is harder than other hard metals and ceramic materials, and wear is significantly reduced. The diamond-like carbon used in the present invention is obtained by coating solid carbon by evaporating it by vacuum arc discharge. CVD of hydrocarbon gas
Unlike diamond-like carbon containing hydrogen produced by the method, hard diamond-like carbon containing no hydrogen is produced. Diamond-like carbon containing no hydrogen has a Vickers hardness of 5000 Hv to 100
An altitude equivalent to 00 Hv is obtained, and the Vickers hardness of hydrogen-containing diamond-like carbon is from 3000 Hv to 500
Higher hardness than 0Hv. High hardness improves wear resistance.

When hard, high-adhesion diamond-like carbon is produced by the CVD method, a heating temperature of 350 ° C. or higher is required and the brazing material may be re-melted. Since there is no possibility of deformation of the base material and remelting of the brazing, since the coating can be carried out at.

The friction coefficient between the base material of the center and the metal work piece has a high value of 0.5 or more. However, since diamond-like carbon does not have crystallinity like diamond, sintered diamond or synthetic diamond, the surface is very smooth. The friction coefficient between diamond-like carbon and other metals has a low value of 0.2 or less, and has an effect similar to that of a solid lubricant and reduces wear. High hardness has a low coefficient of friction and prolongs life.

Further, in the friction between metals, the wear powder of the soft material of the work piece adheres to the hard center, which further increases the friction coefficient and accelerates wear deterioration. However, diamond-like carbon does not cause adhesion of metal powder and prolongs its service life.

Although diamond-like carbon is hard and has a low coefficient of friction, it wears a little, but in order to obtain a practical life, the thickness of diamond-like carbon is 0.5 to 5 μm. Thickness is desirable.

[0020]

As described above, in the center according to the present invention, by coating the base material of the center with diamond-like carbon having high hardness, the coefficient of friction can be lowered and the adhesion of abrasion powder is eliminated. , The wear due to the sliding of the center tip is significantly reduced. According to the present invention, a center having a long durable life can be provided.

Although diamond-like carbon is hard, it is a thin film, and the base material at the tip of the center is more effective when it has high hardness. When diamond-like carbon is coated on the center where the cemented carbide tip is attached for 1 micrometer, the life of the cemented carbide tip is about 5 times longer than that of the material.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a first embodiment of a center according to the present invention.

FIG. 2 is an explanatory diagram of a second embodiment of the center according to the present invention.

FIG. 3 is an explanatory diagram of a center according to a conventional technique.

FIG. 4 is a coefficient of thermal expansion of a material regarding a center.

[Explanation of symbols]

1 shank 2 hard tip 3 brazing material 4 Middle class 5 diamond-like carbon

Claims (4)

[Claims] 1. A center of a turning device, characterized in that a shank tip portion which comes into contact with a workpiece is coated with diamond-like carbon. 2. A center according to claim 1, wherein means for coating carbon with diamond-like carbon is means for vaporizing carbon by arc discharge in vacuum. 3. The center according to claim 1, wherein the diamond-like carbon has a Vickers hardness of 5000 Hv or more. 4. The center according to claim 1, wherein the thickness of the diamond-like carbon coating is 0.5 to 5 micrometers.