AUTOMATED NON-DESTRUCTIVE TESTING OF STEEL ALLOYS MICROSTRUCTURE BASED ON MULTIFREQUENCY EDDY CURRENT METHOD.

The traditional and most common methods for controlling the results of heat treatment of steel alloys are determination of hardness by measuring the parameters of indentation and quantitative and stereometric metallography. These methods are time-consuming in terms of control operations, which are performed according to a special methodology consisting of a visual comparison of the study results with the standard scales, followed by statistical extrapolation to the entire batch or plane of the product. The quality of such operations largely depends on the qualifications of the operators performing them. Presented in this article is the application of an automated open-circuit system of program control of multifrequency eddy current nondestructive testing as an alternative to traditional methods of control of the results of steel alloys heat treatment. It is shown that at certain parameters of programming the measurement operations there is a correspondence between the phase characteristics of the response signal of the 5th harmonic and the type of heat treatment, hardness, and microstructure arrangement in grade 40X steel samples. 28 Ref., 1 Tabl. 1, 5 Fig. [ABSTRACT FROM AUTHOR]