| 摘要 |
<p>Steel sections with high bend strengths and high resistance to brittle fracture are made of a fine-grained steel contg. 0.28-0.4%C, 0.15-0.45% Si, 0.65-1.0% Mn, =0.3% (Cr + Ni), =0.08% P and =0.05% S. The sections are heated by continuous circulation in a furnace to above the Ac3 temp. They are then passed at a constant rate in front of cooling nozzles (12-18) situated immediately outside the furnace. The steel sections are cooled to an upper bainite transformation region. They are then cooled by contacting with air until transformation is complete. After which cooling by spraying with water or by immersion is carried out. The properties of the steel are maintained within narrow limits. Tensile strengths, yield, stress and elongation are constant and the notch strength is 15-20 kg m/cm2.</p> |
