Effect of Refined Spheroidizated Structure on Mechanical Properties of Spring Steel 51CrV4

Abstract

The steel 51CrV4 is widely used for the production of springs. Materials research into spring steels aims to meet the requirements of the industry, which mainly concern high yield and tensile strengths. Ductility has to be retained as the strength is increased. Also, the resistance against brittle fracture is important, measured as fracture toughness. Enhancement of the mentioned mechanical properties can be accomplished by structural refinement. One possible way to refine the final quenched and tempered structure is to refine the soft annealed structure before quenching. The article is devoted to Accelerated Carbide Spheroidization and Refinement (ASR) with a comparison to conventional soft annealing (SA) in the 51CrV4 spring steel. Both spheroidization treatments (ASR by induction heating, and SA by electric furnace heating) led to different carbide particle sizes. The carbide refinement alters the material's behavior during quenching. Finer carbides dissolve more rapidly during austenitization at the quenching temperature. It is possible to lower the quenching temperature thanks to carbide refinement. Mechanical properties after hardening with different quenching temperatures were positively affected too.