Development of Manufacturing Process 'HISTORY' for Producing Innovative High Frequency Welded Steel Tubes with Excellent Properties

摘要

Aiming at weight reduction, the improvement of collision safety and manufacturing cost reduction in the automobile industry, the amount of steel tubes used for automotive parts has been increasing in recent years. The increase of strength and formability of ERW steel tubes is essential for further weight reduction and wider application. However it was difficult to realize high strength and formability at the same time in a conventional ERW steel tube. The formability of ERW steel tubes is not sufficient because the sheet material is subjected to work-hardening in the cold roll forming and the welded portion is subjected to weld-hardening during the electric resistance welding. In order to overcome these technological difficulties, Kawasaki Steel has developed a new steel tube manufacturing method termed the HISTORY (high speed tube welding and optimum reducing technology), which consists of a newly developed thermo-mechanical control process based on new metallurgy by means of the worlds' first warm stretch reducing. The HISTORY tube with high strength and excellent formability has been successfully manufactured in a production line which was built in October 2000 at Chita Works.