Question

In three-high rolling mill, 0.4pt rotates by friction.

• A. Upper roll
• B. Middle roll
• C. Lower roll
• D. Middle roll and lower roll

Hint:

Remember the drive configuration for different mills:

• Two-high: Both rolls are driven.

• Three-high: Top and bottom rolls are driven; the middle roll is an idler (friction-driven).

• Four-high/Cluster: The small work rolls are friction-driven by the large, powered backup rolls.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
A three-high rolling mill is a type of rolling mill configuration used for metal forming. It consists of three rolls stacked vertically. This design allows for reversing the direction of rolling without having to reverse the direction of the powerful driving motors.

Step 2: Detailed Explanation:
The operation of a three-high mill is as follows:

• The top and bottom rolls are directly driven by a motor and rotate in the same direction (e.g., top roll clockwise, bottom roll clockwise).

• The middle roll is an "idler" roll, meaning it is not connected to the motor drive.

• The workpiece is first passed between the bottom and middle rolls. The bottom roll is driven clockwise, pulling the workpiece to the right. The workpiece, in turn, exerts a frictional force on the middle roll, causing it to rotate counter-clockwise.

• The workpiece is then lifted and passed back between the middle and top rolls. The top roll is driven clockwise, pushing the workpiece to the left. The workpiece now exerts a frictional force on the other side of the middle roll, continuing its counter-clockwise rotation.
In both passes, the middle roll is not actively driven by the motor; its rotation is solely due to the friction between it and the workpiece being processed.

Step 3: Final Answer:
In a three-high rolling mill, the middle roll is an idler that rotates by friction.