​​​​​​​The classification of roll materials

The classification of roll materials

There are mainly three categories of roll materials: cast iron, cast steel and forged steel.

1) The carbon content of cast iron roll is about 2.5% ~3.5%.It can be further divided into four categories by materials: chilled cast iron roll, infinite chilled cast iron roll, high chromium cast iron roll and nodular cast iron roll. The common structure in cast iron rolls can be divided into three categories: base, cementite and graphite. The base structure mainly includes austenite, ferrochorite, pearlite, bainite and martensite. The forms of graphite in cast iron generally include flake and ball.

2) Cast steel rolls can be further divided into two types: steel rolls (carbon content 0.4%-1.4%) and semi-steel rolls (carbon content 1.4%-2.4%). Steel rolls have low carbon content, so their hardness is low. Their structure is generally composed of ferrite and pearlite. In order to increase the hardness, chromium, nickel, manganese, molybdenum, vanadium and other alloy elements can be added, or special heat treatment is needed. Because the steel roll has high tensile strength and toughness, it is suitable for the billet mill or bloom mill with high rolling temperature and heavy rolling load, and can also be used as support roll. In case of special heat treatment, high hardness of HS90 or above is obtained, it can also be used as cold rolling work roll. The carbon content of semi-steel roll is between cast steel roll and cast iron roll, and its hardness is higher than ordinary cast steel roll, but lower than cast iron roll. The main feature of semi-steel roll is that the internal hardness drop is very small, so it is especially suitable for making deep pass hole rolls. If the content of silicon is increased, the semi-steel roll has high thermal cracking resistance and strong toughness through graphitization. It can be used as the billet roll of blooming mill, large section steel rough roll, billet continuous rolling roll and hot strip continuous rolling roll to obtain good rolling effect.

3) The forged steel roll is smelted, forged and heat treated to make the working layer of the roll body have high hardness, high wear resistance and excellent accident resistance, and ensure that the neck and core of the roll body have certain strength and high toughness. Because of this unique property, forged steel roll has irreplaceable advantages over cast roll in cold rolling and non-ferrous rolling.

Key words: roll materials, cast iron roll, cast steel roll, forged steel roll