Surface characteristics evaluation apparatus and surface characteristics evaluation method for steel material

Patent metadata

Field	Value
Publication number	US-10768144-B2
Application number	US-201615737948-A
Country	US
Kind code	B2
Filing date	Jun 7, 2016
Priority date	Jun 25, 2015
Publication date	Sep 8, 2020
Grant date	Sep 8, 2020

Abstract

To provide a surface characteristics evaluation apparatus and a surface characteristics evaluation method that evaluate the residual stress in a steel material subjected to a surface modification treatment by considering the distribution thereof in the depth direction. The surface characteristics evaluation apparatus includes an oscillator, a detector, and a measuring instrument. The steel material is placed to abut against or close to a coil in the detector. The oscillator applies an alternating current to the coil, and computation is performed based on a signal indicating an electric characteristic of the coil. The residual stress in the steel material is evaluated by performing this operation while successively changing the frequency of the alternating current. The coil is configured to have a self-resonant frequency higher than the operating frequency.

First claim

What is claimed is:

1. A surface characteristics evaluation apparatus that evaluates a residual stress in a subject made of a steel material subjected to a surface modification treatment, comprising:
an oscillator including an AC power supply and a frequency changing circuit capable of changing a frequency of an alternating current output from the AC power supply;
a detector connected to the oscillator and placed to abut against or close to the subject so that an eddy current occurs in the subject, the detector including a coil capable of inducing an alternating magnetic field when the alternating current is applied by the AC power supply; and
a measuring instrument connected to the frequency changing circuit and the detector;
wherein the measuring instrument is configured to evaluate the subject by performing a computation based on signals acquired with respect to each of a plurality of frequencies set by the frequency changing circuit, and the signals indicate an electric characteristic of the alternating current flowing through the coil,
wherein the plurality of frequencies set by the frequency changing circuit are lower than a predetermined frequency,
wherein the coil is configured to have a self-resonant frequency equal to or higher than the predetermined frequency, and
wherein the frequency band of the alternating current set by the frequency changing circuit falls within a range from 0.5×10 3 Hz to 20×10 6 Hz.

2. The surface characteristics evaluation apparatus according to claim 1 , wherein the coil is formed by winding a wire formed by a plurality of electric conductors bundled together.

3. The surface characteristics evaluation apparatus according to claim 1 , wherein the coil is configured to be capable of surrounding a lateral surface of the subject.

4. The surface characteristics evaluation apparatus according to claim 1 , wherein the measuring instrument includes an I/V conversion circuit that measures the current flowing through the coil.

5. The surface characteristics evaluation apparatus according to claim 4 , wherein the measuring instrument further includes a phase detection circuit that measures a phase difference between an AC voltage applied by the AC power supply and the current flowing through the coil.

6. The surface characteristics evaluation apparatus according to claim 1 , wherein the frequency changing circuit outputs a signal to the AC power supply so that the frequency of the AC voltage applied by the AC power supply is continuously changed.

Assignees

• Sintokogio Ltd

Inventors

• Makino Yoshiyasu

Classifications

• G01N27/9046 Primary

  by analysing electrical signals · CPC title

• G01N27/025

  a current being generated within the material by induction · CPC title

• C21D11/00 Primary

  Process control or regulation for heat treatments · CPC title

• C21D7/06

  by shot-peening or the like · CPC title

• G01N27/90 Primary

  using eddy currents · CPC title