ASTM A799/A799M-10(2020)

4.1 The amount of ferrite present in an austenitic stainless steel has been shown to influence the strength, toughness, and corrosion resistance of this type of cast alloy. The amount of ferrite present tends to correlate well with the magnetic permeability of the steel. The methods described in this standard cover calibration practice for estimating ferrite by the magnetic permeability of the steel. The practice is inexpensive to use over large areas of the cast part and is nondestructive.

4.2 This practice has been used for research, alloy development, quality control, and manufacturing control.

4.3 Since this practice measures magnetic attraction and not ferrite directly, it is subject to all of the variables that affect magnetic permeability, such as the shape, size, orientation, and composition of the ferrite phase. These in turn are affected by thermal history. Ferrite measurements by magnetic methods have also been found to be affected by the surface finish of the material being analyzed.

4.4 Magnetic methods should not be used for arbitration of conflicts on ferrite content except when agreed upon between manufacturer and purchaser.

1.1 This practice 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.

1.2 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in nonconformance with the standard.

1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.