ASTM A799/A799M-10(2020),Standard Practice for Steel Castings, Stainless, Instrument Calibration, for Estimating Ferrite Content.
ASTM A799/A799M-10 covers the procedure for calibration of instruments to be used for estimating the ferrite content of the microstructure of cast stainless steels by magnetic response or measurement of permeability. This procedure covers both primary and secondary instruments.
Referenced Documents
E562 Test Method for Determining Volume Fraction by Systematic Manual Point Count
5. Apparatus
5. 1 One primary instrument that uses magnetic attraction consists of a spring-loaded balance arm from which a rod-shaped magnet is suspended. The opposite end of the balance arm from the magnet has counterweights that balance most but not all of the weight of the magnet.
5.1.1 When this instrument is used, the spring load is relaxed sufficiently to allow the magnet to make contact with the material being tested.
5.1.2 The spring is then wound until the force of the coiledspring overcomes the magnetic attraction of the magnet for the material being tested, causing the magnet to break contact andthe lever arm to rise.
5.1.3 The amount of force that the coiled spring has developed is determined from a marked dial securely attached to the shaft that is used to coil or uncoil the spring.
5.1.3. 1 A weighted No. 2 magnet (catalog number J5-0664W) is used with this instrument.