| 摘要 |
PROBLEM TO BE SOLVED: To prevent the occurrence of cracks of steel.SOLUTION: Firstly, a step S101 includes heating a surface layer of a structure formed of steel with a depth up to 5 μm, to a temperature of a transformation point of the steel or higher with a high-frequency heating method (first step). A depth (thickness) of the surface layer to be heated may be set at a value which is approximately equal to intervals (1 to 5 μm) between stripes of striation seen on a fatigue fracture surface of austenitic steel. Next, a second step S102 includes annealing the surface layer of the heated structure, and forming the surface of the structure into sorbite (second step). For instance, the surface layer may be gradually cooled at a cooling speed of 60°C/hour or less by lowering the value (current value) of a high-frequency current. |
