Rolls

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Rolls

 

the working members (instruments) of a rolling mill. Rolls perform the basic rolling operation: the deformation (reduction) of the metal to give it the required dimensions and shape. The rolls consist of three elements: the barrel, two journals (trunnions), and the driving end (the “wobbler”). Rolls are divided into flattening and fluted types. Flattening rolls are used to roll sheets, plates and strips, and bars; the barrel of such a roll is cylindrical, slightly convex or concave. (Such rolls are also called smooth.) Fluted rolls are used to roll shaped (fluted) metal (circular or square cross sections, rails, I-beams, and so on); the grooves that correspond to the profile of the metal to be formed are made in the barrel surfaces of these rolls. The notches are called passes (the passes of two rolls form gauges), and the rolls are called grooved (gauging) rolls.

The basic dimensions of rolls (diameter and barrel length) depend on the gauge of the rolled product. The roll diameter for hot rolling is 250-300 mm (wire rolling) to 1,000-1,400 mm (bloom and slab rolling). For cold rolling, rolls are used with diameters from 5 mm (in 20-roll mills in foil rolling) to 600 mm (in quarto mills in the rolling of thin strips).

Cast-iron rolls with a Shore hardness of 35-45 (produced by casting in sand-clay molds) are the least expensive and are used in the hot rolling of soft strip steel; cast-iron rolls with a Shore hardness of 55-75 (produced by casting in metallic molds—chill molds) are used in sheet mills and in the finishing stands of section and wire mills; alloyed (with chromium, nickel, or molybdenum) cast-iron rolls with a Shore hardness of 40-70 are used in section rail and structural and thin-sheet hot-rolling mills; and steel rolls are used in blooming mills, slabbing mills, reduction stands of section mills and in cold-rolling mills. The working rolls of small multiple-roll mills, as well as flatting mills for the spreading of high-strength steel wire, are produced from ceramic hard tungsten-carbide alloys (with cobalt added); the wear resistance of such rolls is 30-50 times greater than that of steel alloyed rolls. Wear-resistant and strong rolls for section and sheet rolling are obtained by metal surfacing with hard and superhard alloys.

Worn rolls are restored by returning on roll-turning lathes or regrinding (for sheet-mill rolls) on roll-grinding lathes.

REFERENCES

Tselikov, A. I., and V. V. Smirnov. Prokatnye stany. Moscow, 1958.
Korolev, A. A. Mekhanicheskoe oborudovanie prokatnykh tsekhov, 2nd ed. Moscow, 1965.

P. I. POLUKHIN


Rolls

 

the operating members of crushing, flour-milling, punching, and other machines in the form of smooth or grooved rolls, cylinders, or cones (generally rotating in different directions) that process the material passing between them; they include forging rolls, crushing rolls, and others.