Heat treatment of magnesium cast iron crankshafts

Conclusion

• 1. The following composition (%) of magnesium nodular iron can be recommended for automobile engine crankshafts: 3.40–3.60 C (initial), 1.15–1.30 Mn, 2.0–2.20 Si., 0.005S (max), 0.120 P (max), 0.15–0.25 Cr, 0.03–0.06 Mg.

• 2. Cast crankshafts must be spheroidized according to the following schedule: 1) air hardening (normalizing): heating at 950 (±10)°C; holding for 8 hours; cooling at a rate of 60–30°C/minute down to 600°C; 2) tempering, i.e. heating at 725 (±15)°C, holding for 8 hours; air cooling.

• 3. Service experience with such crankshafts having a spheroidite structure confirmed their suitability fully to replace forged crankshafts.