The RenewRolls European project consortium will develop repairable bimetallic rolls using laser deposition technologies to reduce raw material consumption, waste generation, and downtime at steel plants.
Work rolls used in hot rolling of steel are subjected to high thermomechanical loads and intense wear. After successive rolling campaigns, their surfaces must be reprofiled by machining, an operation that is repeated until the rolls reach a minimum diameter beyond which they can no longer be used. In addition, due to dimensional requirements and geometric compatibility among the rolls in a rolling mill, reprofiling a particular roll may require adjusting the remaining rolls in the mill to maintain appropriate reduction conditions across the different rolling passes.
The RenewRolls (RENEWable Hot Rolling ROLLs through DED-LB/P Technology) project, involving Tekniker, RINA Consulting, Acciaierie d’Italia, and AZTERLAN, proposes an alternative approach: the development of a new generation of repairable bimetallic rolls using laser-based directed energy deposition (DED-LB/P).
As explained by AZTERLAN researcher Dr. Jon Arruabarrena, specializing in Forming Technologies, work rolls used in the hot rolling of long products are generally either “bimetallic, manufactured by centrifugal casting by combining a steel or cast iron core with an outer shell made of a high-chromium alloy, or monolithic, manufactured from high-speed steel (HSS).” Current practices for recovering these rolls face two main challenges. On the one hand, “the recovery of deteriorated rolls is primarily based on machining, which results in a progressive loss of material. On the other hand, in the case of HSS rolls, their removal also means discarding a high-alloy, high-cost material containing elements considered critical raw materials by the EU, such as tungsten, cobalt, and vanadium.”
RenewRolls proposes a shift in this approach, prioritizing repair over machining by adding new material only to the working surface of the rolls. “Additive manufacturing makes it possible to restore the roll geometry without progressively reducing its dimensions with each reprofiling cycle,” Arruabarrena explains. To make this possible, the project addresses the **entire roll life cycle**, from the metallurgical design of both the feedstock material and the roll body through manufacturing, repair, and reuse.
Bimetallic rolls through laser deposition
The research team will develop new materials and processes based on DED-LB/P technologies, including laser cladding and extreme high-speed laser material deposition (EHLA). These technologies will make it possible to produce ultra-high-hardness layers on the roll surface while maintaining a high degree of control over heat input and geometry.
“One of the main metallurgical challenges we face is the application of laser technologies to cast iron substrates, due to the limited weldability of this material, its thermal conductivity, and its susceptibility to defects and cracking.” To address this challenge, RenewRolls will work on the design of new ductile iron compositions for the substrate or main body of the roll and HSS metal powders for the working surface, optimized to facilitate the successive repair of the rolls, as well as on in situ monitoring and adaptive control strategies to ensure the quality and repeatability of the deposition process.
The developments will be validated through microstructural, chemical, and mechanical characterization of the materials and coatings, including their tribological behavior. The performance of the prototypes will also be evaluated after successive reconditioning cycles.
“The goal is to demonstrate that a worn roll can be repeatedly reconditioned and returned to service, reducing the need to manufacture and replace complete components. This strategy will help reduce raw material consumption, waste generation, and downtime associated with the current replacement and readjustment of rolls.”
[+] More information about RenewRolls project
[+] RenewRolls project main contact in AZTERLAN: Dr. Jon Arruabarrena
RenewRolls is funded by the European Union through the Research Fund for Coal and Steel (RFCS), under Grant Agreement No. 101296123.
