PURPOSE: To make welding strain small and to improve bendability by linear heating by specifying the ratio of the yield stress at the temp. of a steel sheet and the yield stress at room temp and the plate thickness.
CONSTITUTION: The yield stress at ordinary temp. is essentially required to be small and the yield stress at the high temp. during welding heat history to be high in order to suppress the angular deformation by welding. The yield strength of ordinary steels decreases continuously and uniformly as temp. rises and, therefore, the difference between the yield stress at ordinary temp. and the yield stress at the high temp. during the welding heat history is required to be made small in order to satisfy such requirements. Namely, the angular deformation by welding is suppressed by controlling the yield stress of the steel sheet to a prescribed range according to the welding heat history. The ratio of the yield stress δyT at the temp. T of the steel sheet and the yield stress δy at room temp. is, thereupon, set to satisfy the equation over a temp. range from room temp. or above to ≤600°C and the sheet thickness is specified to ≥3 to ≤25mm, by which the weld strain is made small and the bending by linear heating is made easy.
KAWASHIMA YOKIKA
NAGAHARA MASAAKI
KASUYA TADASHI
KOJIMA KAZUHIRO
HORII YUKIHIKO
FUJITA TAKASHI
