Original Article

Multi-functional simulation system for continuous hot bar rolling: development and industrial application

¹ State Key Laboratory of Crane Technology, Yanshan University, Qinhuangdao 066004, PR China
² Department of Mechanical Engineering, Politecnico di Milano, Milano 20156, Italy
³ National Engineering Research Center for Equipment and Technology of Cold Strip Rolling, Yanshan University, Qinhuangdao 066004, PR China
⁴ Jiangsu Yonggang Group Co. Ltd, Zhangjiagang 215600, PR China
⁵ Department of Design and Production Engineering, Ain Shams University, Cairo 11566, Egypt
⁶ Department of Metallurgical and Materials Engineering, Federal University of Rio de Janeiro, Rio de Janeiro 21941-901, Brazil

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Received: 28 August 2025
Accepted: 7 May 2026

Abstract

Multi-pass hot caliber rolling technology has significant advantages in producing continuous bars, which can be used as structural and connecting parts with essential applications. Simulation is an important tool for reproducing production processes. The simulation model must show the thermal state, microstructure, and hot workability during the bar’s high-temperature deformation process. However, such a multifunctional simulation model has not yet been reported. Here, a finite element simulation system for hot bar rolling is presented. It is based on the DEFORM-3D software and has been further developed. The most distinctive feature of the proposed simulation system is the integration of a material model that combines constitutive prediction with hot workability prediction. The constitutive model is formulated within an internal state variable framework, enabling the coupled prediction of microstructural evolution and stress response during multi-pass hot deformation. The hot workability prediction model is established based on a backpropagation neural network. By incorporating the microstructural state and deformation conditions as input variables, the model enables dynamic evaluation of hot workability throughout the deformation process. Based on the embedding of the material model, the simulation model can realize the coupled simulation of temperature, deformation, microstructure, and hot workability. Subsequently, the model is validated and applied based on an actual hot bar rolling production line. The simulation successfully predicts the surface cracks in rolled bars and provides insights into the underlying mechanisms of crack formation. The analysis indicates that the primary cause of cracking is the mismatch between the groove geometry and the workpiece geometry, which leads to localized deformation of the corner metal and a sharp temperature drop. Based on this understanding, a matching relationship between the groove geometry and the workpiece geometry is proposed, and the groove structure is optimized accordingly. After optimization, the surface quality pass rate of the rolled bars improved significantly, increasing from approximately 50.7% to about 95.3%. The simulation system can be applied to the hot bar rolling process and other multi-pass hot forming technologies. This is important for optimizing the production process and improving product quality.