Metal deforming – With use of control means energized in response to activator... – Metal deforming by use of roller or roller-like tool element
Reexamination Certificate
2000-06-22
2001-04-17
Tolan, Ed (Department: 3725)
Metal deforming
With use of control means energized in response to activator...
Metal deforming by use of roller or roller-like tool element
C072S009100, C072S241600, C072S366200
Reexamination Certificate
active
06216505
ABSTRACT:
This application claims priority under 35 U.S.C. § § 119 and/or 365 to Japan Patent Application No. 11-179442 filed in Japan on Jun. 25, 1999, the entire content of which is herein incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and apparatus for rolling a strip. More particularly, the present invention relates to a method and apparatus for rolling a strip, which method or apparatus enables reliable rolling of uniform quality for producing thin strips, including foils having good shape.
As used herein, the term “shape” refers to surface shape and the term “good shape” refers to the surface of a strip in which uneven stretching has been suppressed, such as so-called center buckling in which stretching of a central portion of a strip in the width direction is greater than that of the edges; a so-called wavy edge in which stretching of the strip edges is greater than that of a central portion; and so-called quarter buckling in which stretching of outer quarter portions in the width direction of the strip is greater than that of the center and edges.
2. Related Background Art
Typically, a 4-hi rolling mill which has left and right pressing-down balancers, roll benders, and roll coolants is widely used for rolling strips of various metals. When such a rolling mill is employed, the shape of the strip is regulated by approximating the strip shape in the width direction by use of a power function and matching the strip shape to a target shape based on the approximation by means of the pressing-down balancers disposed on both the left and the right sides, the roll benders, and the roll coolants.
Japanese Patent Publication (kokoku) No. 20171/1993 discloses a method for regulating the strip shape in which a variable crown roll having a single oil chamber serves as a back-up roll and a strip shape in the width direction detected by a shape detector is approximated by a function including terms of the first, second, and fourth (or sixth) powers of a distance measured from the center of the width, each term of the power function being controlled to match a corresponding target value. Specifically, the term of the first power is controlled by adjusting the amount of the left and right pressing down (hereinafter called “pressing-down amount”); the term of the second power by adjusting the roll crown of the variable crown roll having a single oil chamber; the term of the fourth power or the term of the sixth power by adjusting the bending force of a roll bender.
However, when a rolling apparatus employing a small-diameter work roll having a ratio of barrel length L to diameter D (L/D) is more than 4, such as a rolling apparatus employed for rolling thin strips such as aluminum foil, controlling the term of the fourth power is substantially difficult, because portions effectively controlled by a roll bender are limited to the ends of the roll.
In addition, when a thin strip having an exit-side-thickness as low as about 30 &mgr;m or less is rolled, ends of the upper and lower work rolls come into contact with each other at their end portions, due to the small thickness of strip. In such a situation, a work roll bender which controls the strip shape by utilizing the bending force of a work roll does not function effectively.
In this case, control by roll coolants is more important. However, roll coolants disadvantageously require a warm-up process prior to rolling, and in addition, the performance thereof is unsatisfactory and response during operation is poor.
Therefore, the conventional controlling schemes involve problems that sufficient control precision cannot be attained, particularly in the rolling of thin strips such as foil.
SUMMARY OF THE INVENTION
In view of the foregoing, an object of the present invention is to provide a method for rolling a strip, which method is easy to carry out, ensures good response, and enables shape control of high precision, even when a strip is rolled by means of a rolling apparatus employing a small-diameter work roll having a ratio of barrel length L to diameter D (L/D) is more than 4. Another object of the invention is to provide a rolling apparatus employed for attaining the above object.
Accordingly, the present invention provides a method for rolling a strip by means of a rolling mill having a pair of work rolls and a pair of back-up rolls for supporting the work rolls, wherein
one back-up roll of the pair of back-up rolls is a variable crown roll having a single oil chamber, and the other back-up roll is a variable crown roll having a plurality of oil chambers; the method comprising:
detecting a strip shape in the width direction;
approximating the detected strip shape by a power function which includes terms of second and fourth powers of a distance measured from the center of the width;
adjusting the term of second power by controlling the roll crown of the variable crown roll having a single oil chamber so as to match a target value; and
adjusting the term of the fourth power by controlling the roll crown of the variable crown roll having a plurality of oil chambers so as to match a target value.
The present invention also provides a method for rolling a strip by means of a rolling mill having a pair of work rolls; a pair of back-up rolls for supporting the work rolls; left and right pressing-down balancers; roll benders; and roll coolants, wherein
one back-up roll of the pair of back-up rolls is a variable crown roll having a single oil chamber, and the other back-up roll is a variable crown roll having a plurality of oil chambers; the method comprising:
detecting a strip shape in the width direction;
approximating the detected strip shape by a power function which includes terms of the first, second, fourth, and sixth powers of a distance measured from the center of the width;
adjusting the term of the first power by controlling the pressing-down amount of the left and right pressing-down balancers so as to match a target value;
adjusting the term of the second power by controlling the roll crown of the variable crown roll having a single oil chamber so as to match a target value;
adjusting the term of the fourth power by controlling the roll crown of the variable crown roll having a plurality of oil chambers so as to match a target value;
adjusting the term of the sixth power by controlling the roll bending force of the roll benders so as to match a target value; and
controlling the roll coolants so as to obtain an elongation corresponding to the difference between the detected strip shape and a target shape which is approximated by the power function.
In these methods for rolling a strip, as an example of a work roll, there is a work roll having a small diameter with a ratio of barrel length L to diameter D (L/D) of more than 4.
In these methods for rolling a strip, a variable crown roll having two oil chambers may serve as the variable crown roll having a plurality of oil chambers.
In another aspect of the present invention, there is an apparatus for rolling a strip, which apparatus comprises a rolling mill, a shape meter, and a calculation and control unit, wherein
the rolling mill comprises a pair of work rolls; a pair of back-up rolls for supporting the work rolls; left and right pressing-down balancers; roll benders; and roll coolants;
one back-up roll of the pair of back-up rolls is a variable crown roll having a single oil chamber and the other back-up roll is a variable crown roll having a plurality of oil chambers;
the shape meter is disposed at the entrance or exit of the rolling mill to detect a strip shape in the width direction;
the calculation and control unit approximates the strip shape detected by the shape meter by a power function which includes terms of the first, second, fourth, and sixth powers of a distance measured from the center of the width;
the calculation and control unit calculates the following control amounts:
the control amount of the pressing-down amount of the left and right pressing-down balancers so as to match a target value of the
Hamada Ryuji
Hiramatsu Shinichiro
Clark & Brody
Sumitomo Metal Industries Ltd.
Tolan Ed
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