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Rolls for steel and metal processing

Stainless steel, steel, aluminum and non-ferrous metal applications

For the processing of steels and metals, a wide variety of high requirements are placed on roll coatings. In addition to high mechanical requirements, resistance to aggressive media and temperatures can be decisive. Special coatings for particularly demanding positions allow significant process improvements and longer service lives.

Below are examples of a few industry challenges with suggested solutions. For more information or a non-binding recommendation from our technicians for your application, please contact us directly.

Poor squeezing result
5 Lösungsvorschläge
  • Unsuitable coating
  • Damage to the roll surface
  • Heavily worn roll surfaces
  • Attack by chemicals used
  • High process temperatures
  • High production speeds

Effects of a poor squeeze result

  • Carryover of media

  • Contamination of the process chemistry

  • Disturbance of the following process steps

  • Drastic reduction in service life

Squeeze rolls are designed to squeeze liquid media from a substrate and seal the baths in the area of the product inlet and outlet. Minor damage to the roll surface results in local spots of residual media remaining on the belt, which then lead to unwanted effects on the end product.

If the squeeze rolls have circumferential damage or are heavily shrunk, they no longer seal sufficiently. This causes process chemicals to be carried out of the bath, which has a negative effect on subsequent process steps.

The optimum coating of a squeeze roll depends on several parameters. These include the chemicals used and their concentration, the process temperature and the product speed.

High temperature load
5 Lösungsvorschläge
  • Heat transfer through hot products or media
  • High process temperatures required
  • Heat radiation from other plant components
  • Furnace outlet or IR emitter
  • Standard PUR coating melts and contaminates product
  • Hardening and cracking of the cover material (rubber)
  • Flattening and slippage of the cover
  • Marks due to cracks and chipping of the coating

In many places, rolls coated with elastomers are subjected to high temperatures. This means temperatures between 80°C and 250°C, depending on the elastomer.
If PU coatings become too hot, they melt, rubber smooths out and cracks. The superficially melted coating material sticks to the product, is carried away and can hardly be removed.

Lamination issues
5 Lösungsvorschläge
  • Adhesion of the product to the roll cover
  • High temperature load
  • Static charge
  • High contact pressure
  • High production speeds
  • Melting and cracks in the cover
  • Wrinkles in the product
  • Damaged products
  • Core detachment of the cover 
  • Impurities in the product

The lamination of films onto steel, stainless steel or non-ferrous metal takes place at high temperatures, whereby the lamination roll coatings are subjected to high stress.  Depending on the coating used, it melts, cracks or becomes slippery smooth.
High contact pressure and / or high circumferential speeds often result in damage to the lamination roll coating, for example, due to marks or detachment of the cover.

Slipping due to lack of web traction
4 Lösungsvorschläge
  • Coefficient of friction too low
  • Oil or other media wetting surface
  • Very high belt tension
  • Slipping of the belt
  • Differential speed from belt to roll
  • Rapid coating wear
  • Uncontrolled belt movement

S-rolls are used to control tension. This requires a very high coefficient of friction in order to be able to transfer large torques between the roller and the belt. S-rollers usually have a wrap angle >180°.

In contrast to the S-rolls, drive and brake rolls only have contact with the belt in a narrow nip.

Slipping of roll covers causes increased wear due to abrasion on the coatings. This can lead to slippage of the strip or also interfere with the control of the drives.

Damage due to pickling / degreasing
4 Lösungsvorschläge
  • Insufficient acid resistance of the roll cover
  • Solvent resistance of the roll cover too low
  • Change in coating properties due to aggressive media
  • Roll cover becomes cracked / brittle
  • Roll cover becomes soft / sticky
  • Washing out on the cover surface
  • Product contamination
  • Core loosening from cover fabric

Many products pass through degreasing baths, pickling and rinsing. There, dipping, deflecting, squeezing, and carrying rolls are used and guide the product through the plant segments. These rolls are in contact with the aggressive media used in these baths and become soft, sticky or cracked and the surfaces can be washed out.

Only coatings that are optimally matched to the process chemistry ensure a long service life and optimized squeezing results.

High mechanical load
4 Lösungsvorschläge
  • High line loads
  • Hysteresis 
  • Core binding overload
  • Rolling overheats roll coating
  • Chipping from coating
  • Bonding failure 
  • Coating sheared off
  • Plant shutdowns 

In the case of pressure, drive and brake rolls, premature damage to the cover often occurs in the form of chipped off parts of the roll coating. The reason for this is the high line pressure required for the roll position. In the case of the roll covers, the high line pressure leads to increased rolling and to a temperature buildup due to hysteresis. The roll cover melts or overheats or the core bond is extremely stressed.

For these applications, MITEX offers a range of heavy-duty special coatings with low abrasion, high cut resistance and very good bonding to the roll body, which are especially suitable for very high line pressures.