Standard Practice for Steel Castings, Stainless, Instrument Calibration, for Estimating Ferrite Content

Importancia y uso:

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.

4.2.1 Many instruments are available having different designs and different principles of operation. When the probe is placed on the material being investigated, a closed magnetic circuit is formed allowing measurement of the magnetic permeability. When calibrated with standards having known ferrite content, this permeability indicates the ferrite content of the material being analyzed. The estimated ferrite content is read from a calibrated dial or from a digital readout dial. Follow the manufacturer's instructions for proper calibration of the instrument.

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.

Subcomité:

A01.18

Referida por:

A0800_A0800M-20

Volúmen:

01.02

Número ICS:

77.140.80 (Iron and steel castings)

Palabras clave:

calibration; ferrite; stainless steel castings;