Research on the optimal frequency for tube production.
High frequency contact and induction welding processes have been used in welded tube production for more than 50 years with little attention paid to welding frequency. Traditional vacuum-tube type welders operated at frequencies between 300 and 400 kilohertz (kHz). First-generation solid-state welders, which were introduced in the early 1990s, generally had frequencies that were much lower, the average being around 200kHz. The lower frequency range resulted from early circuit designs used by some manufacturers and component limitations of the time.