表層強化熱延鋼板の引張予加工後疲労限度比の向上

抄録

A study has been made of the plane bending fatigue strength of the surface layer strengthened hot rolled steel sheets produced by austenite range rolling of cast composite ingot which in the surface layers, about 0.1%C-0.5 %Mn are added on the 0.08 %C-0.8%Mn base composition and also of the stainless clad hot rolled steel sheets. Following results are obtained.
(1) The ratio of fatigue limit to tensile strength (RFT) in the 8 % tensile prestrained surface layer strengthened hot rolled steel sheet is about 0.65 at 10 % surface fraction. In this case, dislocation hardening due to high work hardening properties in the surface and inner layers, and compression residual stress in the inner layer have increased fatigue limit of composite steel sheet.
(2) Fatigue crack initiates from inner layer in the stainless clad hot rolled steel sheets. The calculated RFT of inner layer becomes about 0.62. This value is higher than that of inner layer only, namely 0.44.
(3) It is thought that in the surface layer strengthened hot rolled steel sheet, the surface fraction at which RFT is highest becomes smaller by the tensile prestrain.