Approach to Magnetic Property Determination of Powder Particles for Flaw Detection

The paper describes an approach to magnetic property determination, namely, magnetic susceptibility of χ particles of a powder used for flaw detection. It is proposed to use the original method of a sparse dispersed sample tested on a number of dispersed samples (in particular, magnetite). The results of data comparison obtained for finely dispersed magnetite by different methods: previously applied ponderomotive method and the proposed ballistic method, are given. Magnetic susceptibility of magnetite samples is determined by ballistic method at field strength H = 120 kA/m and different values of volume fraction γ of magnetite in a sample. Here, the results of determination for samples of the same magnetite, but obtained by the ponderomotive method, with a field strength H = 140 kA/m, are given for comparison. It is shown that the compared data are quite consistent with each other; the desired, close to linear section is limited to the same γ value, i.e. the “inflection” of γ-dependence of in both cases practically falls on the γ ≈ 0.2. This makes it possible to find (when obtaining data for the corresponding sparse samples) the values of magnetic susceptibility χ of individual particles. For the powder used in flaw detection, studies were carried out on a ballistic installation in the field strength range H = 22.5-135 kA/m at different values of the volume fraction γ of magnetoactive particles in the powder. It was found that within the present H range, χ values fall within the range of χ = 3-1.2. For this H range, a phenomenological dependence of χ and H was obtained, which turned out to be close to exponential decreasing.