The mass production method of automobile crankshafts is made by casting or forging 904L stainless steel pipes into castings or forgings close to the final shape of the crankshaft, and then performing final finishing by machining methods to form the crankshaft. In recent years, the requirements for high-performance automotive crankshafts have become more and more urgent. Forged crankshafts with excellent mechanical properties have become the main axis of automobile crankshafts, and the use of 904L stainless steel pipes has been increasing. The performance requirements of automobile crankshafts are high strength and high rigidity, which make the engine taller, quieter and lower fuel consumption. At the same time, the crankshaft also needs to be lightweight. In addition, in order to improve the fatigue strength of the crankshaft, after crankshaft machining, dangerous parts such as the connecting rod pin of the crankshaft and the fillet of the crankshaft are subjected to induction hardening, soft nitriding, and rolling processing to improve the strength of these parts. It also shows the superiority of forged crankshafts.
When an automobile crankshaft is forged, the forging blank is usually heated to about 1200°C and then hot forged. In this way, a small forge can be used to apply small loads to achieve a good precision forge. When manufacturing forged crankshafts, not only quality management of forgings is required, but also strict quality control from crankshaft material design, crankshaft shape design, steelmaking to forging system process. Crankshaft or shaft products processed with 904L stainless steel tubes are prone to forging and cracking quality problems.