April 13, 2009
Development of ‘Ultra low torque back-up roll unit for Tension levelers,
[enabling torque reduction by 40% compared with NTN conventional unit]
NTN Corporation (hereafter NTN) has developed ‘An ultra low torque back-up roll unit’ for tension levelers of sheet rolling mill equipment, thereby reducing torque by 40% compared with NTN conventional product.
Tension levelers prevent plastic elongation distortion of the steel sheet formed when bending and tensile forces are present. The back-up roll rotates with the contact friction force with either a work roll unit or an intermediate roll unit. Hence, if the rotational torque is high, slippage occurs and affects the steel sheet quality (micro undulation). In recent years, the reduction of the rotational torque of the back-up roll unit is required to save energy for environmental impact reduction as well as for stable quality.
In response to the need, NTN optimized the internal specifications and lubricating condition of the bearing utilized in these levelers. These changes ensure low torque and reliability for longer period of time by use of NTN quality and analysis technologies. This action took robustness into account and adopted a new seal design that strengthens the labyrinth structure, thus enhancing sealing function reliability against grease leakage.
By these improvements, this ultra low torque back-up roll unit achieved the reduction of the rotational torque by 40% and temperature rising by 20%.
If feeding speed of steel sheet in the production line is the same as the conventional one, this new unit will contribute to reduction of environmental impact. Conversely, if line speed is increased, these improvements will contribute to enhanced productivity.
NTN launched sales of this new unit to plant makers, appealing to high-speed performance requirements, enabling drastic torque reduction for environmental conservation and energy savings. Additionally, productivity improved by increasing the line speed.
[ Features ] (in comparison with the NTN conventional unit)
a. Rotational torque: Reduced by 40%
b. Temperature rise: Reduced by 20%
[ Application ]
Tension leveler for steel sheet production equipment
* Basic dynamic load rating: Expresses a rolling bearing's capacity to support a dynamic load, and the load under which the basic rating life of the bearing is one million revolutions.
[ Product photo ]
[ Example of application: Tension leveler ]
Tension levelers are sheet production equipment that corrects distortion of the sheet with plastic elongation formed by applying bending and tensile forces. Tension leveler consists of three kinds of roll units i.e. a work roll unit in contact with the steel sheet, an intermediate roll unit (omitted in some cases) in contact with the work roll unit and a back-up roll unit in contact with the intermediate roll. They rotate with the contact friction force. In these roll units, only the back-up roll unit can support a radial load.