抄録
A high yield stress structural steel which has good notch toughness even for heavy sections, has beendeveloped by addition of a small amount of niobium to a semi-killed steel.
Selection of heating temperature before hot rolling and subsequently the control of the amount ofniobium-precipitates in the steel, were found to be very important to the manufacturing process.
The steel thus developed has a yield stress greater than 36kg/mm2, good notch toughness by V-Charpyimpact value of over 3.5kg-m/cm2 at 0°C and high fatigue strength over 30kg/mm2 by repeated bendingtests.
The steel has good weldability comparable to conventional manganese-silicon steels with equivalent tensilestrengths, and can be welded either by manual or automatic welding processes.
