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涡流法的无损检测是建立在电磁感应基础上的,它利用在交变磁场作用下不同材料会有不同振幅和相位的涡流值来检测铁磁性和非铁磁性材料的物理性能、结构和冶金情况的差异性,其用途如下:1.能测量电导率、磁导率、晶粒大小、热处理状况、硬度和尺寸;2.能检出裂缝、折叠、气孔和夹杂等缺陷;3.分选金属材料,检查其成份、显微组织和其它性质的差异;4.测量金属材料上非金属涂层、铁磁材料上非铁磁材料涂层的厚度等等。由于涡流是由电磁感应产生的,在检测时并不要求与试样接触,所以涡流法具有很高的检测速度。同时它又是一种无损的检验方法,因此对产品可进行100%的检验。应当指出的是,涡流法是一种间接的测量方法,因此对仪器指示值与工件的结构特征之间关系必须加以仔细研究,以避免得出错误的判断。涡流法用途很广,只要符合上述情况,一般都能应用,但必须看到材料的许多性质和特征对涡流来说都有反映,一些变化并不影响材料的性能或工件的使用,而仪器指示中会有信号,甚至很大的信号值,这就限制了流法的应用.因此要正确地使用涡流的检验方法,必须对涡流法有一个全面的理解.
Eddy current method based on the non-destructive testing is based on the electromagnetic induction, which uses different materials under alternating magnetic field will have different amplitude and phase of eddy current values to detect the physical properties of ferromagnetic and non-ferromagnetic materials, structure and metallurgy Of the difference, its use is as follows: 1 can measure conductivity, permeability, grain size, heat treatment conditions, hardness and size; 2 can detect cracks, folding, porosity and inclusions and other defects; 3 sorting metal Material, check the composition, microstructure and other properties of the difference; 4. Measurement of metal materials on non-metallic coatings, ferromagnetic materials on the non-ferromagnetic coating thickness and so on. Due to the eddy current is generated by electromagnetic induction, the test does not require contact with the sample, so the eddy current method has a high detection speed. At the same time it is a non-destructive test method, so the product can be 100% of the test. It should be noted that the eddy current method is an indirect method of measurement and therefore the relationship between the instrument’s indication and the structural characteristics of the workpiece must be carefully studied to avoid erroneous judgments. Eddy current method is widely used, as long as the above conditions are generally applicable, but must be seen that many of the properties and characteristics of the material are reflected in the eddy current, some changes do not affect the performance of the material or the use of the workpiece, and instrumentation There will be a signal, even a large signal value, which limits the application of the flow method.Therefore, to correctly use the test method of eddy current, you must have a comprehensive understanding of the eddy current method.