JP2003034808A - Method of improving life of cemented carbide tool for cutting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of improving the life of a cemented-carbide tool which is made by means of dispersing particles of a hard material such as WC or TiC into a metal matrix of Co or the like. SOLUTION: This improving method is characterized by cryogenic treatment onto the cemented carbide tool, which means immersing the tool into liquid nitrogen for 1-10 hours to keep it at -196 deg.C of the boiling point of liquid nitrogen, and then bringing it back to a room temperature atmosphere. The low temperature tempering, which usually accompanies the cryogenic treatment, is not performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for improving the cutting life of a cemented carbide tool by subjecting the cemented carbide tool to a cryo treatment. Here, the "cryo treatment" refers to a low temperature treatment called "ultra-subzero treatment", which usually uses the refrigeration of liquid nitrogen.

[0002]

2. Description of the Related Art After quenching an iron-based alloy, it is exposed to a low temperature of 0.degree. C. or less to perform "subzero treatment" or "super-subzero treatment" for increasing hardness. The increase in hardness is caused by a mechanism of cooling the retained austenite that has not become martensite during quenching to a low temperature and converting it to martensite. By applying this principle to the side of cutting tools (mainly HSS), it has been attempted to extend the life of the tools by increasing the hardness of the tools.
Some results have been recognized.

The inventor wondered whether the ultra-subzero treatment would be useful for extending the life of the cemented carbide tool, and as a result of experiments, he found that the expected improvement was obtained. Cemented carbide tools mainly consist of particles of hard substances such as carbides and nitrides of refractory metals, which are mixed with matrix metals such as cobalt and sintered, so the above mechanism for iron-based alloys is expected. It's impossible, and it's a surprising and unexpected fact.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for improving the life of a cemented carbide tool by utilizing the facts found by the above-mentioned inventors.

[0005]

A method for improving the cutting life of a cemented carbide tool of the present invention that achieves the above object comprises subjecting a cemented carbide tool to a cryo treatment. In this cryo treatment, specifically, a cemented carbide tool is immersed in liquid nitrogen for 1 to 10 hours and placed at a low temperature of −196 ° C., which is its boiling point,
Then, the temperature is returned to room temperature.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the ordinary cryogenic treatment of iron-based alloys, when the iron-based alloy is placed at a low temperature and then returned to room temperature, low-temperature tempering is performed by immersing it in boiling water for several tens of minutes. , It was found that this low temperature tempering was either pointless or at times rather detrimental and could diminish the effectiveness of the cryotreatment. In addition, cemented carbide tools are often coated with a hard substance such as TiN, but the effect of cryo treatment is
It was also found to be independent of the presence or absence of this type of coating.

[0007]

[Example] As a cemented carbide tool, a powder of WC or the like is integrated in a matrix of Co, which is a P10 grade,
Cryogenic treatment was performed by immersing in a liquid nitrogen for 4 hours, with and without a TiN coating layer on the surface. Some tools were cryo-treated (abbreviated as "CT") followed by low temperature tempering (abbreviated as "LT"), which was immersed in boiling water for 40 minutes.

A normalizing material of S45C steel was selected as a material to be cut, and was turned under the following conditions. In normal turning, tool life often ends up due to lateral flank wear of the tool. Therefore, when the lateral flank wear reached 100 μm, the life was considered to have expired, and the distance cut up to that point was recorded. The tool life is indicated by a relative value when the cutting distance of the untreated carbide tool used for comparison is 100.

[0009]

[0010]

By subjecting the cemented carbide tool to the cryo treatment according to the present invention, the cutting life thereof is improved by about 20%. Needless to say, tool life is a major factor in determining the cost of machining. Extending the tool life not only directly reduces the cost of the tool but also improves the work efficiency by reducing the labor and time required for the tool change, which is a doubly effective cost reduction measure.

The reason why this effect is exhibited has not yet been clarified by the inventor, but while the cemented carbide tool is kept at a low temperature, particles of a hard substance such as WC and TiC are formed into a matrix. A possible mechanism is that metal (mostly Co) is additionally deposited while maintaining a strong bond.

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) C22F 1/00 692 C22F 1/00 692B

Claims (2)

[Claims] 1. A method for improving the cutting life of a cemented carbide tool, which comprises subjecting the cemented carbide tool to a cryo treatment. 2. Cryogenic treatment in liquid nitrogen for 1 to 10
The cutting life improving method according to claim 1, which is carried out by immersing for a time.