Method for rolling metal strips, particularly steel strips
A method of rolling metal strip, and in particular steel strip, in which the metal strip passes through the roll gap of at least one roll stand, allows the work rolls of the roll stand which define the roll gap to be able to be shifted along their axes of rotation if differences occur in the shape of the roll gap from its desired shape. The method provides for flat products to be rolled which meet very stringent requirements in respect of their dimensional accuracy. For this purpose, the work rolls are shifted in the same direction in accordance with the invention, following a given shift strategy which is characterized by a regular change in the direction of shift (R−, R+) as a function of the reaching of given maximum shifted positions (V 2 , V 4 , V 6 , . . . , V 28 , V 28 , V 30 , V 32 . . . , V 53 ).
1. Method of rolling a metal strip, in which the metal strip passes through the a roll gap of at least one roll stand, the work rolls of the roll stand which define the roll gap being able to be shifted along their axes of rotation if differences occur in the shape of the roll gap from a desired shape, the method comprising
a) shifting each of the work rolls in the same direction wherein a center of the work rolls moves relatives to a center axis of the metal strip,
b) starting from a starting position (V 1 ), maintaining a given direction of shift (R+, R−) until a respective maximum shifted position (V 2 , V 4 , V 6 . . . , V 26 ) is reached at which a first change takes place in the direction of shift (R−, R+),
c) maintaining the direction of shift (R+, R−) which has commenced in a given case until a maximum shifted position (V 2 , V 4 , V 6 . . . , V 26 ) is reached which, relative to the starting position (V 1 ), is larger in size than, or equal in size to, the maximum shifted position (V 2 , V 4 , V 6 . . . , V 26 ) which was reached previously in the opposite direction of shift (R−, R+),
d) on the given maximum shifted position (V 2 , V 4 , V 6 . . . , V 26 ) being reached, reversing the direction of shift (R+, R−),
e) repeating steps c) and d) until the size of the given maximum shifted position (V 2 , V 4 , V 6 . . . , V 26 ) has reached a maximum value (V 26 ),
f) starting from the maximum shifted position corresponding to the maximum value (V 26 ), maintaining the given direction of shift (R−, R+) until a respective maximum shifted position (V 28 , V 30 , V 32 . . . , V 52 ) is reached which, relative to the starting position (V 1 ), is smaller in size than, or equal in size to, the maximum shifted position (V 28 , V 30 , V 32 . . . , V 52 ) which was reached previously in the opposite direction of shift (R−, R+),
g) on the given maximum shifted position (V 28 , V 30 , V 32 . . . , V 52 ) being reached, reversing the direction of shift (R+, R−),
h) repeating steps f) and g) until the given maximum shifted position (V 28 , V 30 , V 32 . . . , V 52 ) of the work rolls (A 1 / 1 , A 1 / 2 ; A 2 / 1 , A 2 / 2 ) corresponds to a minimum value (V 53 ),
i) repeating a sequence of steps b) to h) if a worn state of the work rolls is within a permitted range, or the work rolls are replaced if at least one of them has reached a state which is outside the permitted range.
2. Method according to claim 1 , wherein at least six changes of the direction of shift (R+, R−) are made between the starting position (V 1 ) and the point at which the shifted position reaches its maximum value (V 28 ).
3. Method according to claim 1 , wherein there is performed, between two rolling operations in which the work rolls are at shifted positions of a maximum size (V 2 , V 4 , V 6 , . . . , V 28 , V 28 , V 30 , V 32 . . . , V 52 ), at least one rolling operation in which the work rolls occupy a shifted position (V 3 , V 5 , V 7 , . . . , V 25 ) which is located between the maximum shifted positions (V 2 , V 4 , V 6 , . . . , V 28 , V 28 , V 30 , V 32 . . . , V 52 ).
4. Method according to claim 1 , wherein, to allow a given roll-gap contour to be set, the work rolls are shifted in opposite directions along their axes of rotation.
5. Method according to claim 1 , wherein, to allow a given roll-gap contour to be set, one of the work rolls is shifted along its axis of rotation while another work roll remains stationary.
6. Method according to claim 1 , wherein at least one metal strip is rolled for its entire length when the work rolls are located in one shifted position (V 1 -V 53 ) and in that a shift of the work rolls is performed on completion of the rolling of the at least one metal strip.
7. Method according to claim 1 , wherein, during the rolling, the work rolls are loaded in bending to correct for deformation of the work rolls which occurs as a result of the rolling forces.
8. Method according to claim 1 , wherein the work rolls are pivoted to allow a given roll-gap contour to be set.