Depth detection method for steel surface hardening layer

Abstract

The invention discloses a non-contact non-destructive detection method of the depth of a steel surface hardened layer, which is characterized by comprising the following steps: (1) a laser beam which is modulated is radiated on a sample to be measured, an infrared detector is used for receiving the thermal radiation of the sample, and a measured value which is changed along with the modulation frequency of the incident laser beam of a thermal radiation signal is obtained; (2) a profile curve of the thermal conductivity which is changed along with the depth is obtained by adopting the forward numerical fitting algorithm according to the obtained measured value of step (1); (3) and the depth of the hardened layer of the sample to be measured is determined according to the limit value of the change of the thermal conductivity. The non-contact non-destructive detection method of the invention adopts the thermal radiation technology and obtains the depth of the surface hardened layer of the steel sample by the reconstruction of the thermal physical property depth profile; the experiments verify that the obtained reconstructed curve of the thermal conductivity has great consistency with the microhardness curve.

Description

technical field [0001] The invention relates to a non-contact non-destructive testing method for materials, in particular to a non-destructive testing method for the surface hardened layer depth profile of hardened steel. Background technique [0002] Through various heat treatment or mechanical treatment methods, such as carburizing and quenching, carbonitriding, spraying, etc., a hardened layer can be formed on the surface of steel. A hardened steel sample can be considered as an inhomogeneous system consisting of an inhomogeneous layer (hardened layer) and a base layer (unhardened core layer). The physical property parameters of the inhomogeneous layer, such as microhardness, thermal conductivity, and thermal diffusivity, are all functions of depth and have different distributions along the depth direction. [0003] In order to detect the depth of the surface hardened layer, in the prior art, a microstructure measurement method or a microhardness measurement method is us...

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Problems solved by technology

The microstructure measurement method realizes the measurement by cutting the cross section of the sample and performing microscopic observation point by point along the depth direction. This method needs to be carried out by intercepting the sample, which is destructive and cannot be applied to occasions with non-destructive testing requirements, and is very consuming When microhardness measurement methods such as Vickers microhardness measurement are used to calculate the hardness by applying a small load and observing the indentation through a microscope, this method will also cause damage to the material surface, and it is not easy to obtain the exact data of the depth profile of the hardened layer

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