1. Ferrite content measurement

1.1 Ferrite characteristics

The ferrite considered is the remaining δ-ferrite that has not regressed to austenite after the solidified molten metal has cooled.

This minority phase in the austenitic matrix is subject to variations in quantity, form, composition, distribution and orientation in the cross-section and length of the molten zone. Moreover, as it remains in a metastable state, it is susceptible to transformation.

• From a macroscopic point of view

  The ferrite content will vary locally if the dilution is modified, if gammagenic atmospheric nitrogen is introduced during welding (welder's skill, lack of protection) and if the thermal cycle is modified.

  Indeed,...