1. US20180209939 - Surface characteristics inspection method and surface characteristics inspection apparatus for steel product

To provide a surface characteristics inspection method of inspecting a heat treatment on a steel product subjected to a surface treatment in a nondestructive manner. A surface characteristics inspection apparatus is used which includes an alternating-current bridge circuit, an alternating-current power supply that supplies an alternating-current power to the alternating-current bridge circuit, and an evaluation device that evaluates the surface characteristics of a subject, which is a steel product subjected to a heat treatment, based on an output signal of the alternating-current bridge circuit. Coils of a reference detector and an inspection detector in the bridge circuit are energized to produce an alternating-current magnetism to induce an eddy current in a reference subject and the subject, respectively, and the electromagnetic characteristics of the subject obtained in the state where the reference detector detects a reference state is output as a first output signal.