2. Experimental procedure
The spring steel used in this work had a chemical composition of 0.60%C-0.75%Mn-1.69%Si-0.14%Cr-
0.011%P-0.008%S (in wt%). Two-step heat treatments given in Table 1 were carried out to produce a systematic
variation in microstructure. Here specimens were austenitized at 950 °C for 30 min to permit full austenitization.
After austenitizing, the specimens were quenched into a salt pot for isothermal transformation of the austenite