COLD-FINISHED SEAMLESS STEEL PIPE FOR INTEGRALLY MOLDED DRIVE SHAFT, DRIVE SHAFT USING THE PIPE, AND METHOD FOR MANUFACTURING THE COLD-FINISHED SEAMLESS STEEL PIPE

摘要

Provided is a cold-finished seamless steel tube for an integrally-formed type drive shaft that is obtained by cold-drawing a mother tube hot-rolled by the Mannesmann tube-making method, the production of the steel tube involves subjecting steel billets with a specific chemical composition to piercing rolling by the Mannesmann tube-making method, elongation rolling, adjustment of the groove profile in sizing rolling, and subsequently adjustment of its thickness reduction rate in cold drawing in order to secure a maximum depth of inner surface wrinkles of the seamless steel tube being 0.1 mm or less which allows subsequent required processing such that a maximum wrinkle depth of the inner surface is 0.20 mm or less at an inside diameter reduction rate of 30% or more in the diameter reduced portion. As a result, the seamless steel tube can secure torsional fatigue characteristics excellent as an integrally-formed type automotive drive shaft having diameter reduced portions disposed at opposite end portions, and can be used as a hollow member optimal in attaining lightness and quietness. Its use allows automotive drive shafts to be efficiently manufactured.