High-strength spring steel with high heat resistance

Conclusions

• 1. For springs used at 400–425°C we recommend complex alloy steels 50Kh5SMF and 50Kh5SVMF, with 5% Cr.

• 2. Better mechanical properties of steels with 0.46–0.54% C and 5% Cr are obtained by additional alloying −0.55–0.85% Si to improve the hardenability and quench hardness, yield strength, and proportionality limit, and to slow down softening processes during tempering; 1–1.3% Mo and 0.5–0.8% W to reduce lowering of the strength and elastic characteristics during heating; 0.2–1.1% V to retain a fine-grained structure.

• 3. As the result of complex alloying, the steel can be quenched by cooling in air, which greatly reduces changes in volume and distortion of springs.

• 4. We recommend the following uses of these steels: 55KhGSFA (ÉP464) with 0.54–0.62% C, 0.9–1.2% Cr, 0.1–0.25% V, 060–0.90% Mn, and 0.65–0.95% Si for operation at 200–250°C after quenching from 860–870° and tempering at 390–410° to a hardness of HRC 48–50; for operation at 400–425° steel 50Kh5SVMF (0.46–0.54% C, 0.4–0.7% Mn, 0.55–0.85% Si, 4.5–5.3% Cr, 0.5–0.8% W, 0.6–1.0% Mo, 0.2–0.4% V) or50Kh·5SMF (0.46–0.54% C, 0.4–0.7% Mn, 0.55–0.85% Si, 4.5–5.3% Cr, 1.2–1.5% Mo, 0.2–0.4% V) quenched from 990–1000° in oil or in air and tempered at 575–625° to HRC 46–52.