Electrolysis: processes – compositions used therein – and methods – Electrolytic material treatment – Metal or metal alloy
Reexamination Certificate
1999-09-28
2003-03-11
Valentine, Donald R. (Department: 1741)
Electrolysis: processes, compositions used therein, and methods
Electrolytic material treatment
Metal or metal alloy
C204S274000
Reexamination Certificate
active
06531049
ABSTRACT:
TECHNICAL FIELD
This invention relates to a method and an apparatus for removing a Ti-derived film coated on the surface of a cutting tool or the like.
BACKGROUND ART
In recent years, cutting tools having a Ti-derived film, such as a titanium nitride film or a titanium carbide film, coated on the surface of high speed tool steels for improved wear resistance have been in frequent use. In such a cutting tool, the film on a cutting part wears earlier than the film at other sites during use of the cutting tool. After a predetermined period of use, therefore, the film is entirely removed, and the cutting part is cut for readjustment. Then, a Ti-derived film is coated on the cutting tool for recycling. If the coated film deviates from the standard values during the Ti-derived film coating process, all the film is removed, and then the cutting tool is coated again for recycling.
Such removal of a Ti-derived film for recycling is disclosed, for example, in Japanese Unexamined Patent Publication No. 5-112885. According to a method for removing a titanium coated film disclosed in this publication, a cutting tool having a Ti-derived film (TiN, TiC, TiCN or Ti) coated on a base material of high speed tool steel is immersed (12 hours) at a temperature of 10 to 40° C. in a mixed aqueous solution containing 1 to 20% by weight of a polymerized phosphoric acid alkali salt, 1 to 10% by weight of one or more of hydroxy carbonate-derived organic acid alkali salts, 2 to 15% by weight of an ethylenediamine-acetic acid alkali salt, 0.1 to 5% by weight of an alkali hydroxide, and 3 to 7% by weight of hydrogen peroxide. By so doing, the Ti-derived film is removed.
As noted above, with the method of titanium-coated film removal disclosed in the publication, the cutting tool coated with the Ti-derived film is immersed for a predetermined time (12 hours) in a predetermined mixed aqueous solution to remove the Ti-derived film. Removal of the Ti-derived film takes a long time (film removal rate: about 0.3 &mgr;m/h), meaning a poor efficiency of treatment. Particularly in removing a TiAlN film, it cannot be removed even when immersing the cutting tool for 60 hours in the aqueous solution. In this case, the film removal rate is less than 0.1 &mgr;m/h.
Under these circumstances, the present invention has as an object the provision of a method and an apparatus for removing a Ti-derived film, the method and apparatus being capable of efficiently removing the Ti-derived film coated on the surface of a member.
DISCLOSURE OF THE INVENTION
The present invention is a method for removing a Ti-derived film, which comprises immersing an electrode and a member coated with the Ti-derived film in a solution having an OH
−
ion concentration of 10
2
to 10
−4
mol/l, and applying a positive potential to the member, and a negative potential to the electrode.
Thus, the Ti-derived film coated on the surface of the member can be removed efficiently.
The present invention is also the method for removing a Ti-derived film, wherein the solution is an aqueous solution containing an alkali hydroxide and having a pH of 10 or greater. Thus, removal of the Ti-derived film coated on the surface of the member can be performed easily.
The present invention is also the method for removing a Ti-derived film, wherein the temperature of the aqueous solution is kept at room temperature to the boiling temperature of the aqueous solution. Thus, the Ti-derived film coated on the surface of the member can be removed in a short time.
The present invention is also the method for removing a Ti-derived film, wherein the aqueous solution is kept at a predetermined temperature by initially raising its temperature by heating, and then raising its temperature by the heat of reaction. Thus, removal of the Ti-derived film can be performed from the start of the operation, and the surface of the member deprived of the Ti-derived film can be finished to be smooth.
The present invention is also the method for removing a Ti-derived film, wherein the solution is a solution of an alkali hydroxide melted in a solvent consisting of a molten salt and an organic solvent.
The present invention is also the method for removing a Ti-derived film, wherein the Ti-derived film is a film of titanium-aluminum nitride (TiAlN). Thus, the film of titanium-aluminum nitride (TiAlN) as the Ti-derived film can be removed reliably in a short time.
The present invention is also the method for removing a Ti-derived film, wherein the solution is an aqueous solution containing an alkali hydroxide and hydrogen peroxide.
The present invention is also an apparatus for removing a Ti-derived film, which comprises a tank holding a solution having an OH
−
ion concentration of 10
2
to 10
−4
mol/l, an electrode immersed in the solution, and a power source for applying a positive potential to a member coated with the Ti-derived film, and applying a negative potential to the electrode.
Thus, the Ti-derived film coated on the surface of the member can be removed efficiently by a simple constitution.
The present invention is also the apparatus for removing a Ti-derived film, wherein the solution is an aqueous solution containing an alkali hydroxide and having a pH of 10 or greater, and the tank is provided with a heating means for heating the aqueous solution to a temperature in a range of from room temperature to the boiling temperature of the aqueous solution, and keeping the aqueous solution at this temperature. Thus, the operation of removing the Ti-derived film coated on the surface of the member can be performed easily and in a short time.
REFERENCES:
patent: 4886588 (1989-12-01), Curfman
patent: 5062941 (1991-11-01), Sue
patent: 5202003 (1993-04-01), Gordon
patent: 5507926 (1996-04-01), Keller et al.
Hamajima Takumi
Ishimaru Toshiaki
Kakutani Akihide
Kariya Akio
Morimoto Satoshi
Birch & Stewart Kolasch & Birch, LLP
Mitsubishi Heavy Industries Ltd.
Valentine Donald R.
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