Based on the experience achieved in many years of activity BSA recommends to select the correct grade of the steels and the relative surface hardness of rolls depending on the thermal working conditions of the levelers. This is very important because the entire heat treatment cycle of the work rolls depends on the requested final working conditions of the machines.

BSA can guarantee sets of work rolls with mechanical characteristics and surface hardness stability at all the difference working temperature – for cold, warm and hot working condition. All the rolls are 100% checked during all the production’s steps and the accuracy during the final operations guarantees to achieve the top quality for the full set of rolls to ensure optimum flatness results under levelling.

BSA supplies not only rolls but also components assembled with bearing housing and full cassette assembly.

For cold application the material of the work rolls must be very highly wear resistant and though.
This is necessary because of the high thickness of the material rolled and due to the presence of scale on the plate surfaces which is very aggressive.
For this reason to avoid an early wear of the rolling surface the induction heating process must guarantee the highest reachable hardness, without allowing any brittleness of the work roll body and surface.

After the plate rolling mill the temperature of the plates is usually more than 860°C.
This means that the hot leveler receives the material at high temperature and will be subjected both to mechanical and thermal stresses.
For this reason the choice of the steel grades for the rolls must merge the characteristics of:

• Wear resistance
• Thermal shock resistance
• Hardness stability at high temperature
• Excellent mechanical properties and high capacity of heat propagation

One relevant characteristic of these rolls is based on the heat propagation: capacity in the cross section of the roll body to obtain quick cooling of the working surface; overheating can cause cracks or reduction of the hardness.

The backup rolls must join the characteristics of wear resistance, journal toughness and great surface compressive strength. The main grades used for the production of these rolls are Chromium Molybdenum Vanadium steels, with addition of Nickel to improve the mechanical characteristics, in particular toughness and shock resistance.

In order to have the best mechanical properties it is necessary to use forged steel, with high ingot reduction, high purity of the steels and forged blanks free from any kind of internal defect.