In steel rolling production, the rolls are the core components that achieve plastic deformation of metals, and their performance directly determines the efficiency, cost, and product quality of the production line. With the development of rolling mills towards high speed and automation, unprecedentedly high requirements have been put forward for the strength, toughness, wear resistance, and accident resistance of rolls. Against this backdrop, cast iron series rolls, with their outstanding comprehensive performance and continuous technological innovation, have always played an irreplaceable role.
Performance Challenges and Process Innovations
Traditional common centrifugal composite casting rolls once faced severe challenges: the bonding strength between the outer layer and the roll core was low, and alloy elements could easily penetrate the roll core, leading to a decrease in its toughness and plasticity, and eventually causing serious accidents such as spalling, cracking, and even roll breakage. To overcome these challenges, roll workers have developed advanced processes such as electroslag remelting, spray forming and centrifugal composite casting, which have greatly enhanced the bonding strength and overall performance of composite rolls, laying a solid foundation for the manufacturing of high-performance rolls.
The Four Main Forces of Cast Iron Rolls
The microstructure of cast iron rolls (with a carbon content of 2.5%-3.5%) is composed of a matrix (such as martensite, bainite, etc.), carbides and graphite. According to the differences in materials and processes, it is mainly divided into the following four categories:
Common cast iron rolls: A solid guarantee for basic applications
The core of the process: By using the supercooling of molten iron and the rapid cooling of the mold, a surface white cast iron layer is formed to achieve high hardness and wear resistance.
The main types include non-ductile iron, ductile iron composite and ductile core chilled cast iron rolls, as well as infinite chilled cast iron rolls with no clear boundary between the roll body and the core.
Application fields: Mainly serve traditional fields such as stacked thin plate rolling mills, three-high Lauter medium plate rolling mills, wire rod, bar and section steel rolling mills, etc.
High-nickel-chromium infinitely cold-hardened composite cast iron rolls
Experts in resisting hot cracking during the finishing rolling stage:
Performance features: In the working layer structure of the roller body, the graphite content gradually increases from the surface to the inside, and the hardness transitions smoothly. The high content of nickel, chromium and molybdenum alloys endows it with a large amount of carbides, thus combining high wear resistance with excellent resistance to hot cracking.
Manufacturing process: Full flushing (overflow method) or centrifugal composite casting is adopted.
Application fields: It is an ideal choice for the finishing section of modern wide, medium and thick plate rolling mills and strip steel rolling mills.
High-chromium composite cast iron rolls: The pinnacle of wear resistance
Material properties: With high-chromium white cast iron containing 12%-22% chromium as the outer layer, the plate-like Cr7C3, chrysanthemum-like Mo2C and granular Cr23C6 carbides in the matrix form an extremely hard and wear-resistant framework.
Manufacturing process: Centrifugal composite casting, with the core usually made of strong ductile iron.
Application fields: Due to its outstanding wear resistance, it is widely used in the front end of rough and finishing rolling of continuous rolling mills for hot-rolled strip steel, wide and thick plate rolling mills, as well as small section steel/plate finishing rolling mills.
Alloy ductile iron rolls: The strength bearer under heavy-load working conditions
Core advantage: The spherical graphite is evenly distributed, endowing the material with extremely high tensile strength and enabling it to withstand heavy loads.
Organizational classification: It is divided into pearlitic ductile iron rolls and acicular ductile iron rolls. High-alloy needle-like materials often adopt centrifugal composite processes to release casting stress and optimize performance.
Application fields: Due to its excellent thermal shock resistance and wear resistance, it has become the preferred choice for large-scale primary rolling mills, section steel rolling mills, bar continuous rolling mills and large-scale seamless tube rolling mills.
Summary and Outlook
As a technological pioneer in China’s roller industry, the research and practice of CYKC GROUP have demonstrated that the development of roller technology is an innovative history of constantly responding to challenges and precisely matching demands. From ordinary chilled cast iron to high-performance composite rolls, every material upgrade and technological breakthrough aims to address the core contradiction under specific working conditions – whether it is the balance between wear resistance and thermal crack resistance, or the consideration of strength and toughness.
In the future, with the continuous emergence of new materials and new processes, cast iron rolls will continue to support the vigorous development of China’s and even the global steel industry with their reliable performance and constantly evolving capabilities, and will truly become the “backbone of steel”.
Contact：cykc@cykcgroup.com.cn