Various Approaches to Accelerated Carbide Spheroidization of 54SiCr Steel

Abstract:

Changing the lamellar morphology of pearlite to a globular morphology significantly enhances the formability of pearlite-ferrite steels. This change is conventionally achieved by soft annealing. Annealed structures possess low yield strength and excellent ductility and this ensures their good cold formability. The problems of these technologies lie not only in long processing times, but also in high energy consumption which makes the final product quite expensive. The time necessary for cementite spheroidization can be shortened by unconventional heat treatment around A_c1 temperature combined with deformation applied at various processing stages. Several processing methods were utilized for spring steel 54SiCr with ferrite-pearlite original microstructure and lamellar pearlite morphology. The hardness of this structure reached 290 HV10. Three main strategies were tested in this work, using either tensile and compression deformation with following hold applied at heating temperature, temperature cycling around A_C1 temperature, or deformation cycles applied at heating temperature. First of all, various heating temperatures in the region of 680-740°C were tested to determine the most suitable heating temperature for this steel. Subsequently, the influence of the character and intensity of applied deformations on cementite spheroidization and ferrite grain refinement were investigated. Carbide morphology and distribution were determined by the means of light and scanning electron microscopy and mechanical properties were determined by hardness measurement. Spheroidized carbides evenly distributed in fine ferrite matrix were obtained after the optimization of processing parameters.

• Periodical: Key Engineering Materials (Volume 647)
• Pages: 3-8
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.647.3
• Online since: May 2015
• Authors: Ludmila Kučerová*, Hana Jirková, Bohuslav Mašek
• Keywords: 54SiCr Steel, Accelerated Carbide Spheroidization, ASR, Thermo-Mechanical Processing

References

[1] E. Kardeniz, Influence of different intitial microstructure on the process of spheroidization in cold forging. Materials and Design, 29 (2008) 251-256.

DOI: 10.1016/j.matdes.2006.11.015

[2] C. Chen-Chia et al., Accelerated spheroidization of hypoeutectoid steel by the decomposition of supercooled austenite. Journal of Materials Science, 21 (1986) 3339 – 3344.

DOI: 10.1007/bf00553377

[3] L. Kučerová et al. B. Combined effect of deformation and diffusion hold applied close to A1 temperature on carbide distribution in RSt37-2 steel, Proceedings of the 22nd DAAAM, (2011).

[4] B. Mašek, H. Jirková, L. Kučerová, Rapid Spheroidization and Grain Refinement Caused by Thermomechanical Treatment for Plain Structural Steel. Materials Science Forum, 706-709 (2012) 2770-2775.

DOI: 10.4028/www.scientific.net/msf.706-709.2770

[5] H. Jirková et al., Energy and Time Saving Low Temperature Thermomechanical Treatment of Low Carbon Plain Steel, Materiali in Tehnologije / Materials and Technology. 47 (2013) 335-339.