Metallurgical aspects related to contact fatigue phenomena in steels for back-up rolls

The need of even longer rolling sessions is driving the improvement of back up rolls in terms of wear resistance. This is also aimed to reduce costs. In this paper the effect of steel chemical composition on contact fatigue phenomena, bringing to the macroscopic damage named spalling is reported. Results show that the removal by grinding operations of damaged portion of rolls surface should be not sufficient to restore the initial performances of material. Experimental tests showed that a portion of material below the damaged one keeps memory of the last fatigue cycle, and has to be removed.