Rolls are mainly divided into three categories: cast iron rolls, cast steel rolls, and forged steel rolls. The carbon content of the cast iron roll is about 2.50/0~3.5%. According to the main materials, it can be divided into four categories: chilled cast iron roll, infinite chilled cast iron roll, high chromium cast iron roll and nodular cast iron roll. The common structures in cast iron rolls can be divided into three types: matrix, cementite, and graphite. The matrix structure mainly includes austenite, iron, pearlite, bainite, and martensite. The shape of graphite in cast iron is generally Both flaky and spherical.
Cast steel rolls can be divided into two categories: steel rolls (carbon content of 0.4% to 114%) and semi-steel rolls (carbon content of 1.4% to 2.40/0). The steel rolls have low carbon content, so the hardness is low. Its structure is generally composed of ferrite and pearlite. As the carbon content increases, the number of ferrite decreases and the number of pearlite increases. In order to increase the hardness, alloying elements such as chromium, nickel, manganese, molybdenum, and vanadium may be added, or special heat treatment may be performed. Due to its high tensile strength and toughness, steel rolls are suitable for use in rolling mills or roughing mills with high rolling temperatures and high rolling loads. They can also be used as support roles. If special heat treatment is carried out, the high hardness of HS90 or higher can be obtained, and it can also be used as a cold rolling work roll.
The carbon content of the semi-steel roll is between the cast steel roll and the cast iron roll, and its hardness is higher than that of the conventional cast steel roll and lower than that of the cast iron roll. The main feature of the semi-steel roll is that the internal hardness drop is small, so it is especially suitable for the manufacture of deep-hole rolls. If the silicon content is increased in the semi-steel roll material, it has high thermal crack resistance and toughness through graphitization. It is used as the roughing roll for the rolling mill, the large-sized steel rough roll, the rolling mill, and the hot-rolled strip mill. Vertical rolls for good rolling results.
The forging steel roll passes the smelting, forging and heat treatment to make the working layer of the roll body have high hardness, high wear resistance, and excellent anti-accident ability, and at the same time ensure the strength and high toughness of the roll neck and the core of the roll body. This unique property of forged steel rolls gives them an irreplaceable advantage in casting rolls for cold rolling and colored rolling.
