Coating processes – Immersion or partial immersion – Running lengths
Reexamination Certificate
1999-04-27
2001-12-25
Talbot, Brian K. (Department: 1762)
Coating processes
Immersion or partial immersion
Running lengths
C427S348000, C427S443000
Reexamination Certificate
active
06333075
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of forming a film by continuously applying a film-forming treatment to a wire or strip material (hereinafter a material to be treated or being treated is referred to as “strip material”) and an apparatus thereof. In particular, it relates to a method of simply and inexpensively forming a film having a desired thickness by immersing the strip material in a solution bath containing a film-forming component and then drying it, and an apparatus thereof.
2. Description of the Related Art
In a treatment of continuously drawing a steel wire with the use of a lubricant for dry drawing, generally, a borax (borax:Na
2
B
4
O
7
) film is previously formed on a steel wire supplied from a pay off unit, and thereafter a drawing process is carried out through a series of drawing dies with the use of the lubricant for dry drawing.
The role of the borax film in drawing process is to carry the lubricant and also to prevent the die and the steel wire from directly touching each other. The thickness of the borax film is decreased with progression of the drawing process by falling off from the steel wire or elongation during drawing. In the case of continuous drawing process with a series of drawing dies, a certain thickness of the borax film on the steel wire is required even at the final die to prevent the die and the steel wire from directly touching each other. Therefore, it is necessary to form a borax film having a predetermined thickness prior to drawing, considering the reduction in film thickness during the drawing process. That is, in the case of drawing with a series of drawing dies, a thicker borax film is required when the total drawing amount is increased with a larger reduction in the section area of strip material per die and/or larger number of dies.
In such a film-forming treatment, first, strip material is immersed in a solution bath containing a film-forming component and taken out of the solution bath, and thereafter the solution remained on the strip material is drained by blowing or suction of a gas. In this case, the remaining solution should be finally drained to an extent that the remaining solution does not adhere to a jig such as a guide and the like which touches the wire before drying (hereinafter draining to this extent is referred to as “completion of draining”).
The control of thickness of the film is mainly carried out by control of concentration of the film-forming component and the temperature of the solution bath. The concentration of the film-forming component in the solution bath cannot exceed the saturation limit, and also the temperature cannot exceed the boiling point, so that the amount of borax adhered on strip material, e.g. a wire material being continuously supplied and running, is limited. That is, the obtainable amount of drawing is limited because the film thickness cannot be made thicker than a limited value.
As a measure for solving such a problem that drawability is degraded due to the reduction in thickness of the borax film by progression of drawing, JP,7-195116A discloses a method of re-forming a borax film at an intermediate position of a series of drawing dies.
However, this method disclosed in the above publication has such a problem that additional units for heating and film-forming are required to be equipped at an intermediate position of a series of drawing dies. In any case, there has been a limit in thickness of a film on strip material formed by one continuous film-forming treatment without adding extra units such as a heating unit or a film-forming unit.
SUMMARY OF THE INVENTION
A purpose of the present invention is to provide a method and an apparatus for continuously forming a film on strip material by immersing the strip material in a solution bath containing a film-forming component and drying it, by which the desired thickness of the film can be obtained in a simple and inexpensive way even if the immersion time in the bath is short.
In order to achieve the above purpose, a method for forming a film on a strip material according to the invention comprises steps of immersing the strip material in a solution bath containing a film-forming component, taking the strip material out of the solution bath and draining, and is characterized in that the time from taking the strip material out of the solution bath to completion of draining is not less than 4 times the immersion time in the solution bath.
In the method according to the invention, the time from taking the strip material out of the solution bath to completion of draining is preferably 4-12 times, more preferably 4-8 times the immersion time in the solution bath. Moreover, the ambient temperature of atmosphere surrounding the strip material from taking the strip material out of the solution bath to completion of draining is preferably lower than that of the strip material itself, and furthermore, in a preferable draining step after the strip material is taken out of the solution bath, the strip material is blown on its peripheral surface by a gas flowing to the direction opposite to the running direction of the strip material. In this case, the flow rate of the gas is preferably not less than 30 m/sec, more preferably 40-55 m/sec.
In the method according to the invention, if the strip material is a steel wire or strip and the film-forming component is borax, temperature of the steel wire or strip from taking out of the solution bath containing borax to completion of draining is preferably 85-125° C., more preferably 95-115° C. In this case, the steel wire or steel strip can be heated before it is immersed in the solution bath containing borax. Further, it is preferable that the concentration of Na
2
B
4
O
7
—10H
2
O in the solution bath containing borax is not less than 300 g/l, temperature of the solution is not less than 70° C., and the steel wire or steel strip is immersed in the solution bath for not more than 0.1 sec.
An apparatus for forming a film on strip material according to the invention comprises a heating unit for heating strip material being supplied from a pay off unit and run, a film-forming bath for immersion of the heated strip material therein, and a blowing unit for draining having a nozzle for blowing a gas on the peripheral surface of the strip material to a direction substantially parallel and opposite to the running direction of the strip material.
REFERENCES:
patent: 3681118 (1972-08-01), Omaha et al.
patent: 3932683 (1976-01-01), Robins et al.
patent: 4304822 (1981-12-01), Heyl
patent: 5614266 (1997-03-01), Cox et al.
patent: 7-195116 (1995-08-01), None
Bridgestone Corporation
Sughrue & Mion, PLLC
Talbot Brian K.
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