In the metallurgical industry, rolling mills are the core equipment for production. Metallurgical rolls, on the other hand, are the direct tools on the rolling mill that cause plastic deformation in metals. Without rolls, steel cannot be shaped.
What is a metallurgical roller?
A metallurgical roller is a tool used in metal rolling. It generates tremendous pressure through rotation, causing plastic deformation of metal materials such as steel billets and ingots, and ultimately turning them into plates, sections or pipes
A complete roll is composed of several parts:
- Roll body: The part directly involved in the rolling process.
- Roll neck: Used for installing bearings.
- Shaft head: Connects the drive mechanism.
In addition, there are specialized terms such as the shoulder, drive side, operating side, working layer, and core. These parts collectively determine the function and service life of the rolls.
Classification by manufacturing process
Rolls manufactured by different processes show significant performance differences.
Casting rolls is the most traditional method. Molten metal is poured into a mold to form the shape. Among them, the centrifugal casting composite rolls are closely combined by the centrifugal force between the outer layer and the core, which is suitable for manufacturing highly wear-resistant work rolls.
Forged rolls are formed by repeatedly forging steel ingots. Their structure is more compact and their strength is higher. They are often used as support rolls that bear huge loads.
Composite rolls metallurgically bond two or more materials. For instance, composite cast steel backup rolls and composite tool steel rolls. The working layer of the roll body is wear-resistant, while the core has good toughness.
Powder metallurgy rolls are made from powders such as tungsten carbide. Hard alloy rolls and roll rings have extremely high wear resistance and are suitable for high-speed wire rod rolling mills.
Other advanced processes include: surfacing rolled rolls, electroplating rolled rolls, electroslag composite rolled rolls, laser cladding rolled rolls, and spray deposition rolled rolls. These technologies are all continuously enhancing the surface performance and service life of rolled rolls.
Classification by material
The material of the rolls directly determines the applicable rolling conditions.
The carbon content of cast steel rolls ranges from 0.4% to 2.1%. Common types include alloy cast steel rolls, cast semi-steel rolls and graphite steel rolls.
High-chromium steel rolls have a chromium content greater than 8%. Their wear resistance is significantly enhanced.
The alloy content of high-speed steel rolls exceeds 10%. There are a large number of carbides in the structure and it has the effect of secondary hardening after high-temperature tempering. This is the preferred material for modern hot continuous rolling finishing stands.
The carbon content of cast iron rolls is greater than 2.1%. The surface of chilled cast iron rolls forms a white layer with high hardness. Chilled cast iron rolls and pearlitic ductile iron rolls are also widely used in section steel and bar and wire rod rolling mills.
Forged steel rolls include forged alloy steel rolls, forged high-speed steel rolls and forged semi-high-speed steel rolls. They have higher strength and toughness and are suitable for large support rolls and roughing rolls.
Classification by Rolling Process and Configuration
On a complete rolling production line, rolls are classified into multiple roles according to the process.
Hot-rolled strip steel rolls are used to roll steel billets into hot-rolled plates. Among them, roughing rolls withstand large reductions, while finishing rolls ensure plate shape and surface quality.
The work rolls are in direct contact with the rolled piece. The support rolls support the work rolls to reduce their bending deformation. The intermediate rolls are located between the two.
Primary rolling rolls and billet rolling rolls are used to roll steel ingots into billets. Hot-rolled section steel rolls are used to produce I-beams, angle steel, and H-beams.
In the production of steel pipes, the piercing mill rolls, the mandrel mill rolls (MPM), the three-roll cross-rolling mill rolls (PQF), sizing mill rolls and tension reducing mill rolls form a complete tool chain for seamless steel pipe rolling.
Cold-formed steel section rolls and welded steel pipe rolls are used for the production of straight seam welded pipes and cold-formed steel sections.
Roll quality inspection
To ensure the precision of rolled products, rolls need to be inspected regularly.
Ultrasonic testing of rolls using surface wave probes can detect cracks and inclusions on and near the surface of the rolls.
Roller eddy current testing utilizes the electromagnetic induction effect to assess the surface quality of rollers. It is mainly used for monitoring the surface of the roller body during the use and maintenance of rollers.
Conclusion
Metallurgical rolls are indispensable core tools in the steel industry. Understanding their basic terms, manufacturing processes, material classifications, and process configurations is a prerequisite for the correct selection and use of rolls. From casting to forging, from cast steel to high-speed steel, from hot-rolled strip to seamless steel pipe, each type of roll is designed for specific rolling tasks. Mastering these terms means mastering the language of metallurgical rolling.
E-mail：cykc@cykcgroup.com.cn