Removal of sticky scale from hot billet surface

Challenge Details

During the process of rolling angle sections and other rolled products, scale forms on the hot billet’s surface (1,100 Deg C). A water descaler operating at 150 bar is used to remove the scale before the billet proceeds to the rolling stand for size reduction. However, the scale does not get removed completely, resulting in a defect known as “Rolled in Scale” during the rolling process. This problem is commonly seen appearing in the production of angle sections. The defect appears randomly along the length of the angle with a depth of approximately 1 mm. The suspected cause is the presence of a sticky scale that the current descaler system cannot fully remove.

In the past attempts were made to reduce / remove sticky scale which are mentioned below:

• Maintaining the reheating furnace temperature at a maximum of 1,250±30°C. 
• Flipping the billet sides to alternate side facing the burner, thus avoiding direct top and bottom contact.
• Increasing the water descaler pressure from 100 to 150 bar.

Manually grinding the product surface if scale presence is detected. These actions helped remove the defect partially, but complete removal of sticky scale was not achieved.

A solution is sought to completely remove sticky scale from the hot billet surface, to mitigate the rolled in scale defect formation.