Rollers are an indispensable core component of steel mill equipment and one of the most consumed components. Whether it is used for steel rolling in the metallurgical industry or other material processing in the non-metallurgical field, rolls play a key role. With my country’s annual steel output exceeding 800 million tons, especially in the context of the continuous improvement of steel quality requirements in industries such as automobiles and machinery, steel mills have put forward higher requirements for the dimensional accuracy, surface quality and mechanical properties of rolled materials, which directly promotes the urgent need for high-performance roll manufacturing and processing technology.
At present, the important indicator for measuring roll quality is the roll consumption per unit of steel. The average consumption of metallurgical rolls produced independently in my country is 2.46kg/t, while that in developed countries is controlled at around 1kg/t. Precisely because of the obvious gap, large domestic steel mills still need to rely on imported high-end rolls. For example, a large steel company spends up to 200 million yuan each year on the purchase of rolls, of which about 70% is purchased from abroad and only 30% is from China. This not only increases the cost burden, but also exposes the problem of relatively backward roll manufacturing technology in my country.
Therefore, improving the manufacturing process of rolls and optimizing the processing flow are crucial to reducing costs and improving product competitiveness. When selecting rolls, steel mills pay more and more attention to their service life, thermal cracking resistance, wear resistance and overall processing performance.
Conventional manufacturing process of rolls
From a structural point of view, rolls are divided into integral rolls and composite rolls. The integral rolls commonly used in steel mills are mainly manufactured by two processes: casting and forging.
The casting process includes the following three:
- One-piece casting: suitable for ordinary material rolls, with low cost, but relatively poor organizational uniformity and performance stability.
- Overflow casting: It has obvious effects in improving roll quality and is suitable for occasions with higher requirements.
- Centrifugal casting: It is currently widely used in the production of composite rolls, especially suitable for the production of high-alloy wear-resistant layers to improve surface strength and heat resistance.
With the development of technology, steel mills have also begun to introduce more advanced manufacturing technologies, such as static/dynamic centrifugal composite casting, CNC heat treatment, surface spray strengthening, etc., to meet the use requirements under different rolling conditions.
Common Roller Manufacturing Processes
1. One-piece Casting
One-piece cast rolls are also called integral cast rolls. The model consists of three parts: riser, upper roll neck and lower roll neck. Generally, round sand box and dry sand mold processes are used, and bottom pouring is used for casting. In order to quickly cool the middle part, a metal core is used in this area and painted. This process has a simple structure and low cost, but the toughness of the core of the casting is poor, and it is not suitable for high-speed or heavy-load rolling mills.
2. Overflow Casting
In order to improve the toughness of the core of the roll, steel mills often use overflow casting. This method is cast in stages: first pour the working layer molten metal, and then pour the core molten metal later. The unsolidified center molten metal is discharged through the overflow trough to ensure that the metal structure of the core is denser. This process improves the internal performance of the roll, but the operation process is complicated.
3. Centrifugal Casting
Centrifugal casting can be cast vertically or horizontally. Compared with integral casting and overflow casting, this process has obvious advantages:
High utilization rate of alloy materials.
Good surface quality.
Higher strength.
Long service life.
At the same time, centrifugal casting is easy to operate, easy to control, and has high production efficiency. At present, most domestic roller mills use centrifugal casting technology, which is particularly suitable for the production of composite rollers.
4. Forging
The main processes of the forging method include:
Pouring small billets.
Electroslag remelting.
Forging forming.
Rough processing before heat treatment.
Heat treatment.
Finishing.
Forged rollers are integral structures, without bonding layer problems, and stable performance. However, the manufacturing process is complex and the cost is high. It is mainly used in key parts of high-end heavy-duty rolling mills.
New roller manufacturing technology
In order to improve the wear resistance and toughness of rollers, steel mills are gradually adopting advanced composite manufacturing technology. For example:
Static composite casting.
Dynamic centrifugal composite casting.
Surface strengthening technology.
Intelligent heat treatment process.
These technologies, combined with the advantages of traditional processes, can greatly improve the comprehensive performance of rollers, reduce operating costs, and extend service life, and are becoming the development direction of roller manufacturing.
Continuous Casting Composite Technology (CPC)
The continuous casting composite method (CPC) uses a forged steel mandrel with a flux applied to the mandrel surface. The induction coil preheats the mandrel surface and pours the molten metal between the mandrel and the induction coil. The molten metal controls the temperature through induction heating and forms a metallurgical bonding layer with the mandrel surface. To ensure the bonding quality, the melting amount of the mandrel surface needs to be controlled to prevent contamination of the working layer. This method has good bonding quality, but low production efficiency.
Electroslag Remelting and Surfacing Technology (ESR)
The electroslag remelting method (ESR) melts the metal through slag resistance heating. This technology does not require mandrel pretreatment, and the mandrel surface is preheated and cleaned by electroslag, and then the composite metal is welded on it. Its bonding layer is dense and reliable, but the process is complicated and inefficient. The smelting process needs to be strictly controlled to prevent impurities from entering the working layer.
Powder Metallurgy and Hot Isostatic Pressing (HIP) Technology
This method fills metal powder into a steel container wrapped around a mandrel, and then performs a high-temperature and high-pressure hot isostatic pressing (HIP) treatment. The pressed powder forms a high-strength composite layer with good bonding and stable performance. Due to the large equipment requirements and high cost, it is not suitable for the manufacture of large-sized rollers.
Spray Forming Technology
Spray forming technology uses inert gas to atomize molten metal to form fine metal droplets. These droplets are sprayed onto the surface of the receiver and quickly solidify to form a dense deposition layer. According to the state of the droplets, it can be divided into particle precipitation and non-particle precipitation. This method has fine grains, dense structure, and better performance than traditional casting, but the equipment is complex.
Liquid Metal Electroslag Composite Technology (ESSLM)
ESSLM technology operates in a water-cooled copper mold. The roll mandrel is placed in the copper mold, and the molten metal is injected between the mandrel and the mold wall to form a bonding layer. The copper mold not only cools the metal, but also acts as an electrode to maintain the heating of the slag pool. This method is highly efficient, dozens of times more efficient than the traditional ESR method. It can be used for a variety of materials, such as high-speed steel, stainless steel, etc., and is an ideal solution for manufacturing composite rolls.
Combined Roll Manufacturing Technology (CIC)
The combined roll uses a casting method to fuse carbide and ductile iron to form a metallurgical bonding layer. Its structure consists of a roll ring and a roll body. This method can effectively transmit torque and reduce roll ring stress. Compared with traditional mechanical fixing, CIC rolls have a firm bond, strong wear resistance, and a long service life, and have been widely used in mass production.
Conclusion: Choose the Right Rolls, Boost Your Mill’s Performance
With the continuous advancement of rolling technology and the increasing demand for high-performance rolls, choosing the right manufacturing process and roll type is more critical than ever. Whether you need cast rolls for general applications or forged rolls for high-load conditions, or you’re exploring advanced composite roll technologies like CPC, ESR, or HIP, CYKC GROUP is your reliable partner.
At CYKC Group, we offer a full range of high-quality rolling mill rolls, including centrifugal cast rolls, forged steel rolls, and composite rolls using cutting-edge technologies. Our rolls are engineered for longer service life, better wear resistance, and optimized performance under your specific rolling conditions.
Contact us today to find the best roll solution for your mill. Let us help you reduce costs, increase productivity, and stay ahead in the competitive steel industry.
E-mail: cykc@cykcgroup.com.cn