Conventionally, alloy iron rolls were being used in Stand 7 of Merchant Mill to ensure adequate pass life because alloy iron rolls exhibit better wear resistance. However, frequent breakage (four in a year) of these rolls was experienced essentially because these rolls have limited, resistance to thermal shock, fatigue loading and crack propagation. The situation was further aggravated by the introduction of 127 mm square billets as the input to the Mill -this made the pass grooves deeper and intrinsically more susceptible to fire-crack propagation.

To obviate this problem, the operation staff decided to use alloy steel rolls instead of the alloy iron rolls. Alloy steel rolls are inherently stronger though their wear characteristics are inferior. They have superior resistance to fatigue loading, fire-crack propagation and thermal shock. Alloy steel rolls were successfully introduced in Stand 7 in the Merchant Mill. Meticulous planning in pass changing schedule was carried out to counter the higher wear rate of these rolls.