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1. Classification and Applications of Rolls

Rolls can be categorized by manufacturing process (cast rolls vs. forged rolls) and by material (cast iron rolls, cast steel rolls, alloy rolls, and composite rolls). Different rolls are suitable for different rolling processes:

• Roughing and Intermediate Stands: Typically use high-hardness, high-wear-resistant alloy cast iron or cast steel rolls, such as high-chromium iron (HSS) or high-speed steel rolls, to withstand heavy rolling forces and thermal shock.

• Finishing Stands: Require high-precision, high-surface-quality rolls, such as centrifugally cast composite rolls (hard outer layer, tough core) or tungsten carbide rolls, to ensure smooth surface finish on plates or profiles.

• Hot Rolling Rolls: Must have excellent thermal fatigue resistance, such as high-nickel-chromium indefinite chilled ductile iron (ICDP) or semi-steel rolls.

• Cold Rolling Rolls: Typically use high-carbon high-chromium steel or forged steel rolls to ensure high hardness and wear resistance.

2. Key Factors in Roll Selection

(1) Rolling Process Parameters

• Rolling Force: High-load rolling requires high-strength forged or composite rolls.

• Rolling Temperature: Hot rolling rolls must resist oxidation, while cold rolling rolls require high hardness.

• Rolling Speed: High-speed rolling (e.g., continuous mills) demands rolls with superior thermal crack resistance.

(2) Roll Material and Hardness Matching

• Hardness: Roughing rolls typically have a hardness of HS 60-80, while finishing rolls can exceed HS 85.

• Toughness: Roughing rolls must balance wear resistance and impact resistance to prevent breakage.

• Wear Resistance: High-chromium iron (HSS) and tungsten carbide rolls are suitable for high-wear conditions.

(3) Roll Cooling and Lubrication

• In hot rolling, efficient cooling systems are essential to prevent thermal fatigue cracks.

• In cold rolling, proper lubricants must be used to minimize wear and extend roll life.