Frequently utilized roll materials

(1) Alloy forged steel: GB/T 13314-1991 lists steels for hot and cold rolling, while China's national standards specify alloy forged steel for rolls. Hot rolling roll steel contains, among other grades, 55Mn2, 55Cr, 60CrMnMo, and 60SiMnMo. Cold rolling rolls are made of steel that is 9Cr, 9Cr2, 9CrV, 9Cr2W, 9Cr2Mo, 60CrMoV, 80CrN13W, 8CrMoV, and so on.

(2) Alloy cast steel: Only a few types of alloy cast steel are utilized for rolls, and there is no standard alloy cast steel. Cast steel rolls will be widely used in the future as a result of the steady improvement in alloy cast steel quality brought about by the development of electro slag remelting technology.

(3) Cast iron: Alloy and normal cast iron are the two varieties. Rolls of cast iron with varying hardness can be produced by using different casts throughout the casting process. Consequently, there are three types of rolls: semi-cold, chill, and endless chill.

 -Semi-cold roll. There is no obvious white layer on the surface of the roll, and the surface hardness of the roll is HS≥50.

 -Chill roll. The surface has a distinct white layer, the core is a gray layer, the middle is a layer of hemp, and the surface hardness of the roll is HS≥60.

 -Infinite chill roll. The surface is a white mouth layer, but there is no obvious boundary between the white mouth layer and the gray mouth layer, and the roll surface hardness is HS ≥ 65.

Cast iron rolls have high hardness, smooth surface and wear resistance, and the manufacturing process is simple and inexpensive. The disadvantage is that the strength is lower than that of steel rolls. Only the strength of the ductile iron roll is good.

Roller material requirements:

(1) Abrasion resistance is the most common form of damage of the roll, which affects the surface precision and dimensional accuracy of the rolled piece. Since the wear mechanism of the rolled piece and the roll in the roll gap is complicated, there is still no wear resistance. The index can characterize the roll wear resistance, so the wear resistance of the roll can only be judged indirectly based on composition and hardness.

The basis for selecting the hardness of the rolls is the rolling stock, the rolling mill and the rolling conditions, as well as the cost, and sometimes importantly, the operating habits and experience with the rolls. The higher the hardness, the worse the toughness must be considered. The hardness of the rolls is generally measured in terms of Shore hardness because the Shore hardness machine is portable and can be used on rolls without leaving a small indentation on the rolls.

(2) Toughness index The toughness index will be selected according to the main damage of the roll surface. The toughness indexes that can be selected are yield strength, impact toughness, hot and cold fatigue, fracture toughness, and contact fatigue strength. According to the specific use conditions of the rolls and the main damage mechanism, it is generally only necessary to select one of them as the roll toughness index.

Rolls may have residual stresses due to uncoordinated deformation during casting, heat treatment, surfacing, and cutting. When used, the residual stress and the working stress are superimposed to jointly induce different damage phenomena.

(3) The strength requirements of the working layer and the core of the core strength roll are different. Generally speaking, the roll strength should be the core strength to resist bending and torsion stress and avoid breaking the roller.

The working layer of the roll sometimes requires strength directly, such as compressive strength, which can represent the ability of the roll surface to resist fracturing. Due to the high cost of testing the toughness index, the strength of the roll surface against various cracks is sometimes roughly indicated by the strength.