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Title

EVOLUTION OF SKIN PASS ROLLING

Authorship

Schneeweis, Roman; Berger, Karl; Mathweis, Dietrich

Schneeweis, Roman

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Berger, Karl

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Mathweis, Dietrich

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DOI

10.5151/9785-9785-32434

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Abstract

With increasing demands from customers to provide flat strip with tighter tolerances on material properties, particularly flatness of e.g. martensitic steel grades (M1500), it has become necessary to develop strategies to improve flatness without influencing the tensile properties for such hard steel grades. Usual skin pass mills are not capable to apply sufficient tension and roll force for these kinds of material to improve the flatness. Therefore alternatives have to be searched for. One option is to use Sendzimir rolling mills for skin pass operation (using small roll diameters), which are often not available in-house. A second option would be to invest in a major upgrade of the installed skin pass mill or even to install a new skin pass mill with increased roll force and tension capabilities (higher investment costs). On the other hand due to current production overcapacity tandem mills are not utilized to their full extent, which leads to additional outage times. Under such circumstances the idea was borne, why not to use a tandem mill during its additional outage time for skin pass operation of “high strength” steel grades. Through utilization of the tandem mill enough roll force and tension are available. Instead of applying a total reduction of up to 90% during normal rolling operation, the mill technological functions have to be modified for skin pass operation, where the total reduction is minimized down to 0.3% to 0.5%. Technological process and control strategies have to be adapted, like pass schedule generation and interstand tension control. This paper describes skin pass - / temper – rolling methods from the classical one to new alternatives in order to satisfy the demanding market of higher material properties and idle running mills in rolling plants.

Keywords

skin pass rolling, high strength steel grades (martensitic), Evolution