Method for manufacturing hollow shafts

摘要

The present invention describes a method of manufacturing a near-net shaped hollow shaft useful for high power applications such as gearboxes for wind energy industry. The method involves providing a concast bloom (of a round or rectangular or of any polygonal cross section) or an as-cast round ingot from which a hollow perform is prepared using hollow die punching, followed by process of heat treatment, proof-machining and stress relieving.

主权项

1. A method for manufacturing hollow shafts from an input object for use in the gearboxes of wind-energy applications characterised in that said method comprises the steps of optimisation of the near net shape through forging followed by proof machining and stress relieving, said input object is a concast bloom or an ingot which is round or polygonal in cross section, wherein said step of optimising the near net shape comprises the steps of:
a. heating said bloom or ingot in a furnace; b. using flat dies, first drawing the bloom or ingot to an intermediate diameter; c. using flat dies, first upsetting said first drawn bloom or ingot to an intermediate height; d. providing booster heating to the first upsetted bloom or ingot; e. using flat dies, second drawing the first upset bloom or ingot to an required diameter; f. providing booster heating to the second drawn bloom or ingot if required; g. second upsetting the booster-heated bloom or ingot in a hollow die to the final height of the preform; h. punching the second upset bloom or ingot in a hollow die; and i. providing heat treatment to the punched bloom or ingot to carry out normalising, hardening and double tempering so as to produce a near net shaped hollow shaft.