Abstract
Effective application of partial preheating by high frequency induction to enlarge the partial diameter of middle carbon steel was experimentally investigated. The partial preheating was carried out by varying preheating times under the same electric power conditions. As all other conditions other than temperature remained constant during the diameter enlarging experiments, the partial preheating effects were clarified to be estimative using a parameter of the σ/σ_y, where σ_y was dependent on temperature. For preheating times of less than 50 sec, the preheating effect for promoting partial diameter-enlargement did not appear due to blue brittleness influences. For preheating times of less than 110 sec, the preheating temperature was greater than about 856K and was most effective for promoting the diameter enlargement to increase easily the D_f/D_0 to above 2 times without generating damage cracks from fatigue.
