Compound profiling forging method for large wind turbine main shaft

A compound profiling forging method for a large wind turbine main shaft, comprising the following steps:

• step S1, carrying out first heat-up upsetting on a billet to make the billet into a flat square billet, returning the billet into a furnace and holding a temperature at 1250° C.;
• step S2, preliminary stamping, comprising the following working steps:
• working step 1:
• upsetting and drawing out the billet twice, and carrying out punching and rolling on the billet;
• and
• working step 2:
• preparing a piercing punch and a punching block, putting the billet in the punching block, putting the piercing punch into a hole of the billet, and operating an oil press to press the piercing punch to be flush with the billet, so that the punching is completed, wherein the piercing punch comprises a forming part I and a forming part II, the forming part II is provided below the forming part I, a radius of the piercing punch gradually decreases along a center axis from top to bottom, and a curved surface transits from the first forming part I to the forming part II;
• step S3, spinning forming:
• heating the billet, holding a temperature at 850° C., putting the billet in the punching block, preparing a female die and the piercing punch, mounting the female die on the oil press, inserting the piercing punch into an inner hole of the billet to carry out flange upsetting, so that the spinning forming is completed gradually;
• and
• step S4, forging forming of a shaft body:
• inserting a special-shaped mandrel into the inner hole of the billet, pre-drawing a small end of the shaft body of the billet by using a v-shaped anvil, drawing out the shaft body of the billet in sequence, wherein a forging temperature range is 850-1250° C., the billet is drawn out in four sections which have respective dimensions of φ1170 mm×1110 mm, φ1090 mm×450 mm, φ990 mm×440 mm and φ900 mm×890 mm, and an overall forging ratio is ≥5.