Abstract:
It is clear from the figures 8-14 that as the reduction ratio increases, the contact angle also increases. It can be also deduced from the tables 2-4. Therefore higher reduction ratio in the rolling makes larger contact angle. It can be achieved either by reducing roll diameter or by increasing friction between the roll and strip. This is the reason why grooved rolls are used in the rolling operations.
From the tables 1-4, it can be said that moving from the entrance to the exit in the second zone, the velocity increases gradually and direction of the velocity changes gradually.
From the figures 8-22 it is deduced that when contact angle is small, the material near the surface of the roll flows parallel to roll surface and defectless rolled product is obtained. But when the contact angle is larger than a certain critical value al (ai> aopt) , a dead metal zone forms, as shown in figure 37. The material adjacent to the roll adheres to it and is immobilized, forming a die like surface. If the contact angle increases further beyond a certain critical value a2 (a2 > al), a chip rolled product will be formed as shown in figure 38. The roll acts as a cutting tool in orthogonal cutting, shaving off the surface of the strip
