ROLL

Pearlitic Spheroidal Graphite (SG) Cast Iron Rolls: Pearlitic spheroidal-graphite cast-iron rolls have a structure of nodular graphitic iron. These rolls are used in the roughing and intermediate finishing groups for hot rolling of sections and bars. All rolls are statically cast in a single pour. The softest grades have ferrite around the nodules in a pearlitic matrix. The medium-hardness group is fully pearlitic, while the hardest group has a pearlitic-bainitic matrix. Hard grades contain considerably more carbide than soft grades.

Chromium-Alloyed Pearlitic Nodular Rolls: Because the chromium carbides penetrate deeply, the drop in hardness is smaller. They show better wear resistance than standard nodular pearlitic iron rolls, especially in deep grooves of heavy sections. This improved wear resistance comes together with lower mechanical properties in the core and the necks. Wear resistance increases with hardness. Soft grades resist fire cracking better.

Steel-Based Adamite Rolls: They have a bainitic and martensitic structure. Their mechanical strength is higher than that of spheroidal-graphite rolls. They keep their hardness limit at every pass and can therefore be used down to the core. Pass limits are higher than for other roll types.

Acicular Spheroidal Graphite (SG) Cast Iron: Acicular nodular cast-iron rolls have a structure of nodular graphitic cast iron. They are used for rolling various types of billet, section and bar. Statically single-poured rolls of this structure contain spheroidal graphite and carbides inside an acicular matrix. Acicular roll materials contain a higher proportion of alloy than pearlitic ones. The acicular roll has a bainitic-martensitic matrix. Carbide content rises as hardness rises, and wear resistance rises with hardness. The wear resistance of acicular spheroidal-graphite rolls is higher than that of pearlitic spheroidal-graphite rolls of the same hardness. Pearlitic spheroidal-graphite cast-iron rolls, however, have higher resistance to fire cracks. Heat treatment increases resistance to fire cracks.

Chromium-Alloyed Acicular Cast Iron Rolls: Because the chromium carbides penetrate deeply, the drop in hardness is smaller. These grades lose less hardness and give better wear resistance than standard acicular cast-iron rolls, especially in deep grooves. The increase in wear resistance causes a decrease in the mechanical properties of the roll.