To widen the applicable range in sizing by forming a caliver in each roll of the three-high rolling mill at least in a second pass as a shape arranging the arc having a diameter smaller than the diameter of a billet by a specified ratio and a clearance part and rolling into a round bar steel having different product diameter.
To the billet rolled to almost round cross section, the sizing rolling of the round bar steel is executed with 2 sets of the three-high rolling mill mutually shifting 60° angle in the rolling reduction direction. The caliver in each roll of the three-high rolling mill at least of the second pass, is formed as the shape having the arc of diameter smaller than the diameter of the billet by 1-21% and the suitable clearance part. In the case of setting the diameter (dC) of the arc 1-2 at the groove bottom part of the caliver in the second pass to be smaller than the diameter (dO) of the billet 2 by ≥1%, a product having the shape shown with the slanting line in the figure, in which three size free rangers exist, is obtd. Therefore, the necessary number of rolls is reduced and further, the roll change can be saved.
KURODA KOICHI
KAWAKAMI KOICHIRO
Next Patent: DEVICE FOR DRIVING PRESSURE SIDE OF SIDE ROLL