JUSTIFICATION FOR EFFICIENT INITIAL ROUGHNESS OF THE TEMPER MILL WORK ROLLS

Abstract

To produce flat cold rolled products with regulated surface roughness, work rolls with a certain initial roughness are used. However, natural variations in the initial roughness of the rolls between their replacements cause instability in the strips surface roughness. The variability of the black plate surface roughness between work rolls replacements in a two-stand skin-pass mill was studied. Variations in the black plate surface roughness were investigated due to different initial roughness of the work rolls from the first and second stands. At rational initial roughness of work rolls during the period between replacement of rolls, metal surface roughness corresponds to the range of efficient values, and root-mean-square error relative to some reasonable value is minimal. In order to display the variability of the mean sampled and extreme black plate surface roughness values between roll replacement, statistically reliable regression equations in the form of degree relationships were obtained. These equations were used to determine the initial roughness of the work rolls in the first and the second stands, which provide an efficient black plate surface roughness with minimal variation between roll replacement. To ensure efficient microgeometry of black plate during its tempering at two-stand skin-pass mill 500/1350×1200 in the first stand it is expedient to use work rolls after notching with initial roughness Ra = 1.5–2.5 µm, and in the second stand – polished work rolls with initial roughness Ra = 0.5–0.8 µm.