Machining method of finished steel crankshaft

The invention discloses a finished steel crankshaft machining method which comprises the following machining steps: S1, blanking: selecting round steel made of 40Cr, cutting the round steel to meet the requirement of a crankshaft journal, and selecting a steel plate made of 40Cr to manufacture a crank arm; s2, splicing and welding, wherein friction welding is conducted in the mode that the main journal, the crank arm, the connecting rod journal and the crank arm serve as units; s3, primary inspection is conducted, specifically, the welding blank is inspected; s4, heat treatment is conducted, specifically, the crankshaft is subjected to normalizing treatment; s5, secondary inspection: inspecting the hardness and the mechanical property of the crankshaft; and S6, fatigue strength testing: performing fatigue strength testing on the crankshaft, and determining the actual use strength and service life of the crankshaft. According to the method, the semi-finished crankshaft part is welded, so that the blank can be