1、 Cast iron roll

The carbon content of cast iron roll is about 2.5% - 3.5%. According to the main materials, it can be divided into four categories: ordinary cast iron roll, high nickel chromium infinitely chilled composite cast iron roll, high chromium composite cast iron roll, and alloy ductile iron roll. The common structures in cast iron rollers can be divided into three categories: matrix, cementite, and graphite. The main matrix structures are bainite, ferrite, pearlite, bainite, and martensite. Graphite in cast iron generally has two forms: flake and spherical

1. Ordinary cast iron roller

Common cast iron rollers can be divided into chilled cast iron rollers, medium and low alloy infinitely chilled cast iron rollers, and medium and low alloy ductile iron rollers. Chilled cast iron is a type of cast iron obtained by using the supercooling degree of molten iron itself and the surface of the mold to generate a white layer by quenching the surface of the roller body, with high hardness and good wear resistance. According to the manufacturing process and core material, chilled cast iron rollers can be divided into three categories: non ductile iron, ductile composite, and spherical core. Infinite chilled cast iron roller is a material between chilled cast iron and gray cast iron. Graphite exists in the basic structure of the working layer of the roller body, and there is no obvious boundary between the working layer of the roller body and the core. Rubber roller is such a low-end roller. Common cast iron rollers are mainly used for laminated thin plate mills, three high Lauter type medium plate mills, wire mills, bar mills, and section steel mills.

2. High Ni Cr Infinite Cold Hardening Cast Composite Iron Roll

Infinite chilled cast iron is a material between chilled cast iron and gray cast iron. There is uniformly distributed graphite in the working layer of the infinite chilled cast iron roller body and the matrix structure. The content of graphite increases from the surface of the roller body to the inside as the depth increases, and the hardness decreases accordingly

Therefore, there is no obvious boundary between the working layer of the roll body and the core. It is also known as an unbounded chilled cast iron roller. When the infinite chilled cast iron roller material contains high chromium, nickel, and molybdenum alloy elements, it is a high nickel chromium infinite chilled cast iron roller, which is produced using a full flushing (overflow method) or centrifugal composite casting process.

There is a large amount of carbides in the base structure of the working layer of the high nickel chromium infinite chilled cast iron roller body, which has a high wear resistance. The presence of graphite in the base structure makes it have good heat resistance and is widely used as rollers for finishing rolling of wide, medium, and heavy plate mills and strip mills.

3. High chromium composite cast iron roller

High chromium composite cast iron roller is a high alloy composite cast iron roller produced by centrifugal composite casting process using high chromium white wear-resistant cast iron containing 12-22% chromium as the outer layer material of the roller body, and generally using ductile iron as the core and neck material of the roller. Due to the existence of strip like Cr7C3 eutectic carbide, daisy like Mo2C eutectic carbide and granular Cr23C6 secondary carbide in the matrix, high chromium cast iron rolls have excellent wear resistance and are widely used as work rolls for roughing and finishing of hot strip continuous mills, work rolls for roughing and finishing of wide and medium plate mills, and finish rolling of small section steel and plate mills

4. Alloy nodular cast iron roller

Alloy nodular cast iron rollers have high tensile strength, can withstand heavy loads, and excellent wear resistance due to the uniform distribution of graphite from the roller body to the core. The matrix structure is carbide, pearlite, or acicular. Alloy ductile iron rollers can be generally divided into two categories according to the matrix structure of the roller body: pearlite ductile iron rollers and acicular ductile iron rollers. Alloy ductile iron rollers are generally integrally cast, but acicular cast iron rollers can adopt a centrifugal composite casting process due to their high alloy content and high casting stress to achieve ideal comprehensive performance. Alloy nodular cast iron rollers have excellent thermal shock resistance and wear resistance, and are widely used as rollers for large blooming mills, section steel mills, bar rolling mills, and large seamless tube mills.

2、 Cast steel roll

Cast steel roller can be divided into two types: steel roller (carbon content 0.4-1.4%) and semi steel roller (carbon content 1.4-2.4). Steel roller has low carbon content, so its hardness is low. Its structure is generally composed of ferrite and pearlite. As the carbon content increases, the ferrite content decreases and the pearlite content increases. To improve hardness, alloy elements such as Cr, Ni, and Mo can be added, or special heat treatment can be performed. Due to the high tensile strength and toughness of steel rollers, they are suitable for blooming or blooming mills with high rolling temperatures and heavy rolling loads, and can also be used as support rollers. If special heat treatment is performed to obtain a high hardness above HS90, it can also be used as a cold rolling work roll.

The carbon content of semi steel roller is between cast steel roller and cast iron roller. Its structure is mainly composed of pearlite and contains a certain amount of carbide. Therefore, its strength is slightly higher than that of cast steel roller, but lower than that of cast iron roller. Its hardness is higher than that of ordinary cast steel roller. The main characteristic of semi steel roller is that its internal hardness drops very little. Therefore, it is particularly suitable for manufacturing deep hole type roller, and is widely used in roughing and finishing stands of profile steel rolling mills Front working rolls for roughing and finishing of hot strip mills. If silicon content is increased in the material of semi steel rollers, graphitization treatment can provide high resistance to thermal cracking and strong toughness. As blooming rollers, large section steel rough rollers, blooming and continuous rolling mill rollers, and vertical rollers for hot strip continuous rolling mills, good rolling effects can be achieved.

1. According to its chemical composition and heat treatment process, the metal cast steel roller can make the outer layer of the roller body have a matrix structure of pearlite and bainite. Pearlite can be in the form of flakes or balls, or in the form of sorbite. Tempered sorbite not only has high strength and toughness, but also has excellent thermal cracking resistance. Especially, tempered sorbite with phase also has excellent wear resistance. Therefore, when used in a blooming mill, the rolling effect is good.

Alloy cast steel rollers have high tensile strength and toughness, as well as a certain degree of wear resistance and thermal cracking resistance, and are mainly used for blooming rolls and section steel mill rough rolls.

2. Cast high chromium steel roller

High chromium steel rollers are produced using high chromium steel (C: 0.5-1.5%, Cr: 8-15%) as the outer layer material of the roller body, and nodular cast iron as the core material, using a centrifugal composite casting process. Due to the fact that the outer layer of the roller body has a more chromium rich matrix structure than the high chromium composite cast iron material, it has excellent wear resistance. In addition, due to the low content of carbides in the matrix structure of the working layer of the high chromium steel roller body, it has excellent heat crack resistance. Based on this, High chromium steel roll is the development trend of rough roll material selection for hot strip mills.

3. Centrifugal composite high-speed steel roller

High speed steel rollers not only have high resistance to thermal cracking, but also have high wear resistance and red hardness, which can greatly extend the roll life and improve the quality of the rolled material. They can be used for the work rolls in the front section of the finishing mill of the hot strip continuous rolling mill.

4. Semisteel roller

Semi-steel rollers usually have a carbon content of 1.4-2.4%, and their mechanical properties lie between cast steel and cast iron. They have the characteristics of small hardness drop and high wear resistance. They are widely used in the roughing and intermediate rolling stands of section steel mills, as well as in the front work rolls of hot strip mills. When the carbon content of semi-steel is greater than 1.9%, they are called high-carbon semi-steel. Due to their high carbon content, eutectic carbide and pseudoeutectic carbide exist in the matrix structure of high-carbon semi-steel, It is used for the roll of the continuous blooming mill stand, the intermediate stand of the section steel mill, and the roll of the finishing mill stand.

When semi steel rollers are used as hot rolling rollers, in order to improve crack resistance, the silicon content in the composition is increased, and they become graphite cast steel rollers. They combine the advantages of both cast steel and cast iron, and are widely used for continuous billet hot rolling mill rollers and section steel rolling mill rollers.

3、 Forged steel roll

Through smelting, forging, and heat treatment, forged steel rollers ensure that the working layer of the roller body has uniform, high hardness, high wear resistance, and excellent accident resistance, while ensuring that the roller neck and core of the roller body have a certain strength and high toughness. This unique performance of forged steel rollers gives them irreplaceable advantages in cold rolling and nonferrous rolling, which cannot be replaced by cast rollers.

According to the conditions of use, forged steel rollers can be divided into forged steel hot rollers and forged steel cold rollers. Forged steel hot rollers are mainly used for hot rolling billets and section steel rough rollers, while forged steel cold rollers are widely used for cold rollers. The use of forged steel cold roll requires high requirements, and the surface of the roll body must have high and uniform hardness to ensure the dimensional accuracy and good surface quality of cold rolled strip or steel plate. The roll body has a certain depth of hardening layer, and has high accident resistance. Therefore, the original structure of the roll is strictly required, including pure metallurgical quality and organizational uniformity. At present, China mainly uses cold roll materials containing about 2% chromium, with a working layer of about 10mm above HS90, while the newly developed Cr5 series cold roll containing 5% chromium has a working layer of over 30mm above HS90. The excellent performance of the Cr 5 series cold rolling work roll in various aspects will inevitably replace the traditional Cr 2 series cold roll step by step and become the development direction of the cold rolling work roll.