| 摘要 |
PROBLEM TO BE SOLVED: To reduce noise in inspection and to eliminate erroneous detection by adopting either heat treatment of making thin the thickness of decarburized layer on the surface of a steel product or reducing solid solution carbon concentration. SOLUTION: By polishing the surface of a steel product with peeling or the like for eliminating as a non-destructive inspection method with less noise and making thin and uniform the decarburized layer on the surface of the steel product, the generation of noise is relatively reduced and made uniform and the output of a scratched part becomes prominent. Also, by performing heat treatment after rolling, the amount of solid solution carbon in steel can be reduced. When the method is applied to the surface process of a round steel, a surface- polishing process 50 is provided between a soaking process 10 and a heating process 20 and the carbon layer thickness on the surface of the steel product is made thin, thus suppressing noise and preventing erroneous detection. Also, by providing a spheroidizing annealing process 60 between a rolling process 30 and an inspection process 40 and performing heat treatment under a non-oxidation atmosphere, the boundary between the decarburized layer and a non-decarburized layer on the surface of the steel product becomes broad. Then, a permeability change rate decreases and a magnetic flaw detection noise decreases, thus accurately inspecting a surface detect.
|
