Kabushiki Kaisha Kobe Seiko Sho

Toyota Jidosha Kabushiki Kaisha

Sango Co., Ltd.

Yoshiki Tanaka

Yutaka Suzuki

Hiroki Nakajima

Tetsuo Soshiroda

Yoshinobu Omiya

Yoshirou Tomioka

Tomohiro Kase

Kouichi Makii

Shinji Sawaki

Shinichirou Nakamura

Hidenori Shirasawa

Disclosed are alloying elements and microstructures suited for realizing a marked increase in strength of low-carbon or ultra-low-carbon steel plate using a high-density energy source such as a laser. Steel blanks satisfying both high formability and high strength requirements are provided which show sufficient press formability and yet can be markedly increased in strength by laser treatment or which have been markedly increased in strength by laser treatment in areas not to be subjected to severe forming.

Process of Producing high-formability steel plate with a great potential

Herein described is a high strength steel pipe for reinforcing doors of a car, comprising a steel pipe made by seam-welding a steel sheet, wherein a ratio (Hv.sub.1 /Hv.sub.2) of a minimum hardness in a softened area of a weld affected zone to an average hardness in a base material satisfies the following formula,

High strength steel pipe for reinforcing door of car

Growing community of inventors

Akashi, Japan

Yoshiki Tanaka