Effect of spheroidization annealing on low cycle fatigue (LCF) characteristics of cold forged steel components

Abstract

Abstract Cold forging is extensively applied to produce components such as shafts, axles, gears, crankshafts and couplings for automobiles. EN 24 and EN 353 steels possess relatively lower carbon content and have great commercial importance, particularly in the automotive sector. While EN 24 is a preferred choice for shafts, EN 353 is largely used in manufacturing gears and pinions. Apart from improving the mechanical properties of steel, heat treatment makes the steel softer, which reduces excessive forming loads during the cold forging process. The objective of this work is to assess the effect of spheroidization annealing on the fatigue characteristics of both EN 24 and EN 353 steels. Specimens prepared from the chosen materials with and without heat treatment were subjected to low cycle fatigue tests and the fractography images were studied. The investigations revealed that (i) the extent of spheroidization was improved with extended holding time during the heating cycle, (ii) EN 24 steel became softer after spheroidization and had the fatigue life almost doubled, and (iii) For EN 353 steel, the spheroidization resulted in a 50% increase in the fatigue life.