Crystal grain size ultrasonic non-destructive evaluation method without thickness measurement

Abstract

The invention discloses a crystal grain size ultrasonic non-destructive evaluation method without thickness measurement. The method comprises the following steps: carrying out data acquisition on a reference test block and carrying out pretreatment by adopting a signal averaging technology; constructing and calculating a decaying speed coefficient and an average decaying speed coefficient; establishing crystal grain size ultrasonic evaluation models with different thickness measured values; and carrying out crystal grain size evaluation on the test block with unknown crystal grain size. According to the method, the thickness does not need to be measured so that inconvenience on the thickness measurement of a tested object and the influence on the subsequent average crystal grain size, caused by inaccurate measurement, are avoided; the anti-interference capability of the method is effectively improved by a pretreatment means; the evaluation results of two tested test blocks with the average crystal grain sizes being 87.7 microns and 103.5 microns respectively, measured by a metallographic method, are 84.9 microns and 98.9 microns respectively; and errors can be controlled to be +/-5%. Visibly, the method disclosed by the invention provides a means that is not influenced by the thickness and can be used for effectively evaluating the crystal grain size of metal materials.

Description

technical field [0001] The invention relates to the technical field of grain size measurement, and more specifically relates to an ultrasonic non-destructive evaluation method for grain size without thickness measurement. Background technique [0002] Grain size is an important microstructure parameter that affects the mechanical properties of various metal materials. The Hall-Petch formula points out that the mechanical properties of metal materials can be improved by refining the grains. If the austenitic stainless steel weldment has too large grains in the welding heat-affected zone before service, it will lead to insufficient strength and poor corrosion fatigue resistance after service, and it is prone to crack nucleation and propagation along the welding edge, resulting in fracture accidents. It can be seen that the effective detection of the grain size of key materials before service is of great significance for their safe application. The grain size can be measured i...

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Problems solved by technology

It can be seen that the measurement error of thickness will directly affect the accuracy of grain size evaluation

On the industrial assembly line, it is difficult to ensure that the thickness of each measured object is exactly the same. If the thickne

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