1987 Volume 73 Issue 6 Pages 691-698
Spalling phenomena of backup roll of a hot strip mill and their prevention are discussed.Most of spalling phenomena are attributable to either of the following two causes.
1) Excessive fatigue, which occurs mainly at barrel edges due to an increased contact stress resulting from uneven local wear of a roll barrel.
2) A surface crack which is caused by a thermal shock resulting from a mill accident or roll-slip and by propagation of still remaining cracks after dressing.
Accordingly, prevention of spalling should be achieved by both of improved roll property and proper maintenance.The results of the experiments in laboratory and the actual mill operation showed that wear resistance and fatigue property were improved by increasing C and Cr contents and hardness of roll.And it was revealed that reduction of undissolved carbide was effective to improve thermal shock resistance, KIC and fatigue property.Backup roll specifications, however, should be made with consideration of the mill conditions such as operating condition, material and hardness of work roll.Roll maintenance also is important.Detection and perfect removal of a surface crack is essential, in addition to proper dressing depending on the mill conditions.
