Title

Tracing Cold Mill Finish Strip Variation to Deficient Hot Strip Mill Equipment Using Frequency Spectrum Analysis

Tracing Cold Mill Finish Strip Variation to Deficient Hot Strip Mill Equipment Using Frequency Spectrum Analysis

Authorship

F. ROYO, GABRIEL; E. SIMMONS, THOMAS; SCOTT SALTER, L.; N. OSGOOD, PETER

F. ROYO, GABRIEL

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E. SIMMONS, THOMAS

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SCOTT SALTER, L.

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N. OSGOOD, PETER

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DOI

10.5151/2594-5297-LA6281

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Abstract

As older Hot Strip Mills wear, the tolerances of mill components gradually increase until they are out of specification. An area of wear in older style oil film bearings is between the roll and sleeve in the area of the keyway. This area of the bearing is highly loaded. As wear occurs, roll force variation can increase. This condition, commonly referred to as keyway effect, was eliminated with the introduction of the KL bearing 20 years ago. Mills built before the KL design typically experience high roll force variation due to keyway effect and poor roll grinding practices. When Hot Mill strip is to be further processed by cold rolling, the excessive strip variation that was produced by the Hot Mill can then cause out-of-tolerance finish strip from the Cold Mill. This paper will show one of the causes of Hot Mill strip variation and then trace Hot Mill strip variation through a Tandem Cold Mill using Frequency Spectrum Analysis. It will then calculate the possible potential improvement by removing the entry strip variation and recalculating finish strip variation. An economical method of upgrading a Hot Mill to correct the problem is also presented.

As older Hot Strip Mills wear, the tolerances of mill components gradually increase until they are out of specification. An area of wear in older style oil film bearings is between the roll and sleeve in the area of the keyway. This area of the bearing is highly loaded. As wear occurs, roll force variation can increase. This condition, commonly referred to as keyway effect, was eliminated with the introduction of the KL bearing 20 years ago. Mills built before the KL design typically experience high roll force variation due to keyway effect and poor roll grinding practices. When Hot Mill strip is to be further processed by cold rolling, the excessive strip variation that was produced by the Hot Mill can then cause out-of-tolerance finish strip from the Cold Mill. This paper will show one of the causes of Hot Mill strip variation and then trace Hot Mill strip variation through a Tandem Cold Mill using Frequency Spectrum Analysis. It will then calculate the possible potential improvement by removing the entry strip variation and recalculating finish strip variation. An economical method of upgrading a Hot Mill to correct the problem is also presented.

Keywords

Gage Variation; Tandem Cold Mill; Hot Strip Mill; Frequency Spectrum Analysis

Gage Variation; Tandem Cold Mill; Hot Strip Mill; Frequency Spectrum Analysis