Magnetic particle test pieces will help you maintain your mag particle process by verifying magnetic particle performance. Use to check for mag particle deterioration, to compare different magnetic powders, to verify sensitivity or visibility or to assure field direction and strength. In this blog we look at the primary use of Quantitative Quality Indicators (QQIs) and Magnetic Flux Indicators which are to verify field direction and strength.
Field strength and orientation are key factors in a successful magnetic particle examination. Sufficient magnetic field must be present to form indications on the surface being examined. And because magnetism is directional in nature, only discontinuities that cross the lines of flux will produce leakage fields to form those indications.
Unfortunately, the magnetic field within the part cannot be measured directly. So many practitioners use artificial flaws or test pieces to confirm magnetic field strength. At the same time, artificial flaws can confirm direction since only those orthogonal to the lines of flux will form indications. The most common artificial flaws in use are QQIs and Flux Indicator Strips. Each has its own advantages and disadvantages to consider when choosing the right tool for your inspection.