A Review of Warm Forming for Steels: History, Methodology and Emerging Trends

Many manufacturing techniques and processes have been implemented over the years to improve the formability of sheet metals. Warm forming of sheet metals is one such established method. However, it is more commonly and successfully applied to aluminum grades. The re-evaluation of less-used metal forming technologies, such as warm forming and sheet hydroforming for steel are responses to the challenges posed by competitive processes like large castings and the geometry requirements of new BEV parts. By understanding the effects of elevated temperatures (above or below recrystallization temperatures) on different steel grades and the impact of various heating methodologies, the industry can adapt and optimize these proven techniques for modern applications. This paper is a thorough summary of the effect of elevated temperatures on various grades of steel. Different heating techniques, their cycle times and effects on final forming feasibility are contrasted. The effect of chemistry variation on the mechanical behavior of the material for the same grade of steel is also compared. Furthermore, some emerging industrial trends are discussed.