The selection of roll material is closely related to the working characteristics and damage forms of roll.
The roller of the blooming mill and profile mill should have enough strength and impact load, and the hardness of the roller surface can be put in the second place. High strength cast or forged steel commonly used in blooming mill; Cast steel is often used in roughing mill. Cast steel roll containing Cr, Ni, Mo and other alloy elements is suitable for rolling alloy steel; The rollers containing Mn steel and high carbon cast steel are often used in the first rolling mill of plain carbon steel. In the shape of the finished steel mill stand, the finished product shape and tolerance requirements are strict, high surface hardness and wear resistance of the roll, general use of ordinary cast iron roll.
When the work rolls of hot strip mill are selected, the hardness of the roll surface is the main requirement. However, the supporting roller is mainly subject to bending and has a larger diameter in work. The strength and quenching of the roller should be taken into account.
The work roller of the strip cold rolling machine has high requirements on the hardness and strength of the roller surface. The working condition of supporting roller is similar to that of hot rolling mill.
For the purpose of rolling high carbon steel and other hard alloy steel, the combined cold rolling roller with carbide roll cover is also used in the cold rolling machine. The thermal expansion coefficient of the core material should be very close to that of the sleeve material to prevent the sleeve from being damaged when the roll gets hot.
It should be pointed out that although the hardness of the cold rolled work roller is very high, the cast iron roll is not used. This is because when the roll diameter is determined, the minimum thickness of the rolled piece may be inversely proportional to the elastic modulus E of the roll. That is, the larger the elastic modulus E of the roll material, the smaller the thickness of the rolled parts. The E value of cast iron is only half of that of steel, for this reason, the use of cast iron rolls is disadvantageous in cold rolled strip steel.