The customers in the steel industry are demanding that the metal sheet should be
able to be bought tension-free and flat. SSAB is constantly working to produce
sheet with good flatness. To improve the flatness on the sheet, the sheet has to be
leveled in the leveler at the line of cut-to-length. The flatness gauge has been
improved after the rebuilding in the hot rolling mill, which improved the studies of
the strips flatness.
The purpose of this thesis is to calibrate the flatness gauge in the hot rolling mill to
“true” flatness and examine if there is any connection between the leveler settings
and the flatness of the sheet.
Two different production trials were performed during the work of this thesis and
both were fulfilled at SSAB´s production plant in Borlänge. All data from the hot
rolling mill and the 4th line of cut-to-length were compiled in the statistics
program Minitab and the results were interpreted with consideration to leveler
settings and flatness.
The result showed that strips which have a longer edge on the free side from the
hot rolling mill, have better flatness after the leveler compared to strips which have
been leveled and are longer in the middle or have longer edge on the drive side.
The strips from the hot rolling mill, which have longer edge on the free side, are
easier to level in the 4th cut-to-length line. It is because it has been possible to set
the leveler settings to the same values as the set point values. To level the strips as
good as possible the leveler settings need to be the same as the set point values.