Patent ID: 9056386
Filing Date: 2015-06-16
Classification: B24C,C21D,C23C

Abstract:
1. A method of shot-peening (hereafter, “SP”) a work to be treated, which work is a steel product that was subject to heat hardening, comprising: performing a first SP treatment that removes a compound layer that was produced by the heat hardening; determining whether the product of the first SP treatment is acceptable; performing a second SP treatment that gives compressive residual stress to a first-SP-treated surface that was treated by the first SP treatment; wherein the second SP treatment is carried out only on the products that have been proved to be acceptable by a non-destructive inspection and show that the compound layer has been removed from the first-SP-treated surface; wherein determining whether the products have been proved to be acceptable by a non-destructive inspection and show that the compound layers has been removed from the first-SP-treated surface is performed by the nondestructive inspection using an eddy current sensor; wherein the product is determined to be acceptable by the following: first to measure by the eddy current sensor both phase difference in time and amplitude difference in voltage of a current generated from a flux of alternating current at various points of a non-treated work or of the parts of the treated work where the compound layers have not been removed and to enter the results of measurements by the eddy current sensor into a display circuit that is connected to the eddy current sensor via a calculating circuit where the scopes of the phase difference and the amplitude difference are shown as a circle for the criterion for acceptance where a random variable in vector X is μ−nσ<X<μ+nσ, wherein μ is an average value, σ is a standard variation, and n is 2.5-3.5, and wherein the product is determined to be acceptable if all of a plurality of points are plotted outside the circle for criterion, wherein each point corresponds to the phase difference and amplitude difference of the part that was treated in the first SP treatment, and wherein the product that is not determined to be acceptable is rejected.