Using dynamic materials modelling approach to establish critical parameters for hot coiling of spring steels

Abstract

This study investigated deformation-induced defects in 55Cr3, 54SiCr6, and 52CrMoV4 spring steels through isothermal compression testing using Gleeble 3500 thermomechanical simulator. The tests were conducted at deformation temperatures of 760, 820, 860, and 920°C, strain rates of 0.1, 1, 5, and 10 s-1, and a total strain of 0.5. Critical parameters leading to defects were established using power dissipation and instability maps. Microstructural examinations were performed on the deformed samples to validate predictions from power dissipation and instability maps. The results indicated that 55Cr3 spring steel exhibited instability at 850-870°C and 0.3-0.6 s-1, resulting in rounded cracks and pores in the microstructure. To avoid these defects, this temperature and strain rate range should be avoided during the coiling of 55Cr3 with a ferritic-pearlitic initial microstructure. Both 54SiCr6 and 52CrMoV4 were identified as potential alternatives to 55Cr3, with both alloys primarily undergoing dynamic recovery similar to 55Cr3. However, 54SiCr6 was recommended as the preferred alternative due to its higher power dissipation efficiency of 33% and an optimum deformation region similar to that of 55Cr3.