Based on our industry experience, we'd like to share some information about the raw materials and heat treatment of locomotive crankshafts.
The main raw materials for diesel locomotive crankshafts are forged steel and ductile iron. Forged steel crankshafts, due to their high strength and toughness, are widely used in modern high-power diesel locomotives. 42CrMoA and 42CrMo4 are among the most widely used materials for diesel locomotive crankshafts due to their high strength and hardenability. Because crankshafts bear enormous alternating loads during actual operation, the raw materials must possess extremely high tensile and yield strength, elongation, reduction of area, and impact energy. Furthermore, the materials themselves must meet high purity (hydrogen content and non-metallic inclusions, etc.) and high precision (meeting railway industry standards such as TB/T3475.1-2017). The heat treatment processes (crankshaft rolling, surface nitriding, and medium-frequency induction hardening) also require high levels of wear resistance and fatigue resistance. Due to inherent limitations and defects, ductile iron crankshafts are no longer used in railway diesel locomotives.