Rolls must match specific rolling process requirements. Variations in temperature, pressure, deformation degree, and precision across processes lead to distinct differences in roll material, dimensions, and performance. This paper analyzes roll characteristic differences focusing on three core processes: blooming/rough rolling, intermediate rolling, and finish rolling.

1. Blooming/Rough Rolling Rolls: Core Components with High Load-Bearing and Impact Resistance

Blooming/rough rolling is the initial rolling stage, core task being rolling bulk raw materials into preliminary blanks. Characterized by high temperature (>1000℃), large reduction ratio, and intense impact loads, it demands high roll load-bearing capacity and impact resistance.

Common materials: high-strength alloy cast steel, graphite steel, low-hardness ductile iron. For example, nickel-chromium-molybdenum alloy cast steel rolls are used for large-section steel rough rolling; Baoshan Iron & Steel’s blooming mill work rolls (1350mm diameter, 3100mm barrel length) adopt large dimensions for raw material rolling.

Performance requirements: high bending/torsion resistance and toughness to prevent breakage, plus thermal crack and spalling resistance. Surface roughness Ra 1.6-6.3μm, with deep grooves machined for initial shaping.

2. Intermediate Rolling Rolls: Transitional Components with Balanced Performance

Intermediate rolling transitions between rough and finish rolling, core task being reducing blank cross-section, correcting shape, and providing uniform intermediate blanks. Moderate pressure and deformation require rolls to balance toughness, wear resistance, and dimensional accuracy.

Materials: medium-hardness ductile iron, medium-alloy steel; advanced units use semi-high-speed steel rolls (twice the wear resistance of conventional ones). Dimensions fall between rough and finish rolls; for hot-rolled strips, intermediate roll diameter is 30%-50% smaller than rough rolls.

Performance: balanced impact toughness and wear resistance to reduce roll change frequency. Shallow surface grooves, roughness Ra 1.0-3.2μm, mitigating defect transfer.

3. Finish Rolling Rolls: Key Components with High Precision and Wear Resistance

Finish rolling is the final stage, aiming to produce high-precision finished products. Characterized by low temperature (500-800℃ for hot rolling, room temperature for cold rolling), small deformation, and strict precision, finish rolls require high hardness, wear resistance, and dimensional stability.

Materials selected by operating conditions: bainitic ductile iron for hot rolling front section (e.g., F1-F3 stands); high-alloy chilled iron or high-speed steel (75-90HSD) for rear section; alloy tool steel (≥HRC55) for cold rolling. Finish rolls feature small diameter and high precision; hot-rolled strip finish rolling rear section work rolls are ~500mm in diameter.

Key performance: high wear resistance and dimensional stability; cold rolling rolls require corrosion resistance for emulsion environment. Precision-ground surfaces, Ra 0.4-1.6μm for hot rolling, Ra 0.05-0.1μm for cold rolling.

In summary, roll differences stem from process adaptability: materials evolve from high-strength-tough to high-hardness-wear-resistant, dimensions transition from large-low-precision to small-high-precision, and surface quality improves gradually, ensuring stable efficient rolling and high-quality finished products.