METHOD OF QUALITY CHECK FOR CASE-HARDENED LAYER OF FERROMAGNETIC ARTICLES Russian patent published in 2008 - IPC G01N27/80 

FIELD: research of physical properties.

SUBSTANCE: article is first magnetised in heterogeneous pulse magnetic field by a series of uneven number of pulses with constant amplitude H_ps which changes direction through each pulse. Then the article is magnetised by a second pulse series of the same direction as the last pulse of the first series. Pulse amplitude changes from zero to H_p=H_ps with a pitch of ΔH_P. During magnetising by the second series maximum gradient ▿H_gm of residual magnetisation field tension and gradient ▿H_ms after these series is measured. Further the article is magnetised by a third pulse series of the same direction. Pulse amplitude is reduced from H_ps to zero with the same pitch. Gradient ▿H_m0 after the third series is measured. In a fourth series magnetic field direction is changed to the opposite, and pulse amplitude is increased from zero to H_ppi = i·ΔH where i is the number of fourth series pulses. The fourth series includes fewer pulses than the second one. Gradient ▿H_mpi after the fourth series is measured. Magnetisation is continued with a fifth pulse series. Its amplitude is reduced from H_ppi to zero with the same pitch. Gradient ▿H_m0i after the fifth series is measured. In the sixth pulse series the magnetic field direction is changed to the original, and amplitude is increased from zero to H_ppi with a pitch of ΔH_P. Maximum gradient ▿H_mmj during the sixth series is measured. Case-hardened layer thickness and surface hardness HRC is calculated by multiple correlation equations determined in advance.

EFFECT: enables estimation of case-hardened layer quality in terms of thickness and surface hardness HRC.

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