I. Cast iron rolls

Cast iron rolls in the carbon content of 2.5% -3.5% or so, according to the main material can be divided into ordinary cast iron rolls, high nickel-chromium infinite cold hardened composite cast iron rolls, high chromium composite cast iron rolls and alloy ductile iron rolls of four categories. Cast iron rolls in the common organization can be divided into matrix, carburite, graphite three categories, the matrix organization of the main clathrate, ferrite, pearlite, bainite and martensite, graphite in the cast iron in the form of general flake and spherical two kinds of

1, ordinary cast iron rolls

Ordinary cast iron rolls can be divided into cold hard cast iron rolls, medium and low alloy unlimited cold hard cast iron rolls, medium and low alloy ductile iron rolls, cold hard cast iron is the use of the iron itself subcooling and mold surface cooling method to obtain a kind of cast iron roll body surface cooling and generate white layer, high hardness, good wear resistance. Cold hard cast iron roll according to the manufacturing process and core material can be divided into non-ductile iron, ductile composite, and ball core three categories. Infinite cold hard cast iron roll is between cold hard cast iron and grey cast iron between a material, the working layer of its roll body matrix organization in the presence of graphite, and the working layer of the roll body and the core has no obvious demarcation line, rubber roll is this low-end roll. Ordinary cast iron rolls are mainly used for stacked thin plate mill, three-roll Lauter-type plate mill, wire rod mill, bar mill and section steel mill rolls.

2, high nickel-chromium infinite cold hard cast composite iron rolls

Infinite chilled cast iron is bounded in the chilled cast iron and gray cast iron between a material, infinite chilled cast iron roll body working layer of the roll body set matrix organization there is a uniform distribution of graphite, graphite content from the surface of the roll body inward with the depth of the increase and improve the hardness is reduced.

Therefore, the working layer of the roll body and the core has no obvious demarcation line, also known as the boundless chilled cast iron roll unlimited chilled cast iron roll material contains high chromium, nickel, molybdenum alloying elements for the high nickel chromium unlimited chilled cast iron roll, the use of the full flush (overflow method) or centrifugal composite casting process production.

High nickel-chromium infinite cold hard cast iron roll body working layer of the matrix organization of the presence of a large number of carbides, so there is a high degree of wear resistance, the presence of graphite in the matrix organization, so that it has a good resistance to warmth, is widely used to do wide, medium and thick plate mill and strip mill finishing rolls.

3、 High-chromium composite cast iron rolls

High-chromium composite cast iron roll is 12-22% chromium-containing high-chromium wear-resistant cast iron for the roll body outer material, generally ductile iron for the roll core and roll neck material, using centrifugal composite casting process and the production of high-alloy composite cast iron roll. Due to the presence of slate-like Cr7C3 eutectic carbides, chrysanthemum-like Mo2C eutectic carbides and granular Cr23C6-type secondary carbides in the matrix, high-chromium cast iron rolls have excellent wear resistance, is widely used as a hot strip mill roughing and finishing mill before the work rolls, wide plate mill roughing and finishing work rolls and small section and plate mill finishing rolls.

4、Alloy ductile iron rolls

Alloy ductile iron rolls due to the graphite from the roll body to the core was spherical uniform distribution, so the tensile strength, can withstand heavy loads, wear resistance is very good. Matrix organization for carbide and pearlitic or acicular body, alloy ductile iron roll according to the roll body matrix organization can be divided into two categories: pearlitic ductile iron roll and acicular body ductile iron roll, alloy ductile iron roll is generally used as a whole casting, but acicular body cast iron roll due to the high content of alloy, casting stress, can be used in the centrifugal composite casting process, to get the ideal comprehensive performance. Alloy ductile iron rolls have good thermal shock and wear resistance, is widely used as a large-scale primary mill, section steel mill, bar mill and large seamless pipe mill roll.

Second, cast steel rolls

Cast steel rolls can be divided into two categories: steel rolls (carbon content of 0.4-1.4%) and semi-steel rolls (carbon content of 1.4-2.4) steel rolls with low carbon content, so the hardness is low, its organization is generally composed of ferrite and pearlite, with the increase in carbon content, the amount of ferrite decreases, the amount of pearlite increases. In order to improve the hardness, Cr, Ni, Mo and other alloying elements can be added, or special heat treatment, due to the high tensile strength and toughness of the steel rolls, suitable for high rolling temperatures, high rolling loads of open billet mill or primary mill, can also be used as a support roll. Such as special heat treatment, to get HS90 above the high hardness, can also be used as cold rolling work roll.

Semi-steel rolls in the carbon content of cast steel rolls and cast iron rolls, its organization is mainly composed of pearlite, and contains a certain carbide, therefore, its strength is slightly higher than the cast steel rolls, lower than the cast iron rolls, its hardness is higher than the general cast steel rolls Semi-steel rolls, the most important feature of the internal hardness of the rolls landing is very small, so it is particularly suitable for the manufacture of deep-hole rolls, and is also widely used in