Process for making thinwalled tubes, steel for making these tubes and so produced tubes for bicycle frames.

摘要

The steel employed for the manufacture of the tube contains at least 0.3 % of carbon and alloy elements such as chromium and molybdenum in sufficient quantity for the tube blank to have a bainitic structure after hot forming and natural cooling, as well as carbide-forming elements such as niobium and vanadium. The following are carried out in succession: heating of a solid steel rod section to a temperature for dissolving the carbide-forming elements, hot forming of a tubular blank, cooling in air, cold drawing of the blank and cold hammering or rolling of the tube obtained. The invention makes it possible to obtain lighter bicycle frames and forks of higher mechanical strength.