This report explains how significant savings can be achieved in annealing and hot levelling of alloy steel steel sheets.

Annealing involves heating the sheets to 950?C, soaking at this temperature for 30 minutes and air cooling to room temperature.

Hot levelling requires the sheets to be heated to 820?C, soaked at this temperature for 60 minutes and then levelling is continued up to room temperature.

During heating and cooling the sheets, surface oxidation takes place. This basic phenomenon incurs huge losses in terms of expensive material, labour and delayed delivery.

Problems in Annealing & Hot Levelling of Sheets

Sheet dimensions: 4300 x 1100 x 4.5 mm (if coating is not used). Surface pittings were observed after annealing and hot levelling. In the thickness of the cold rolled sheet, grinding allowance of 0.5 mm had to be maintained.

Annealing and hot levelling in the open atmosphere leads to:

• Loss of material which is highly expensive
• Unproductive work of grinding
• Considerable delays in delivery due to grinding

Solution

Oxidation of metal can be prevented by heating in vacuum furnace. Benefits of this technique can be lost during hot levelling which is done in open atmosphere. Vacuum furnace is highly capital intensive. In addition to special safety measures, need of skilled labour adds to the operational cost. Even then, use of vacuum furnace does not provide total solution to the problem of pitting and need for additional grinding. Steel Plant Specialities provides an innovative and cost effective solution.

Coat the cold rolled sheets with ESPON-KP anti-scale compound before charging them into the furnace for annealing. The coating prevents oxidation during annealing and also during subsequent hot levelling.

Benefits of ESPON-KP

Anti-Scale Protective Coating

• Ability to use the existing open atmosphere furnace. Need of vacuum furnace is eliminated, thus saving a fortune in capital investment
• Unproductive work of grinding after hot levelling is reduced by 50%
• Labour cost is reduced substantially
• Lead time is reduced
• Hence increased customer satisfaction