Magnetic Determination of Ferrite Content in Steels

In this paper three different magnetic ferrite determination methods were compared.The tested measuring techniques were AC magnetometer, DC magnetometer and a commercial ferritscope device.A model sample set was prepared from 2507 type super-duplex stainless steel by cold rolling and heat treatment.The above-mentioned methods were used to determine the δ-ferrite content of these samples.The results of the different electromagnetic methods were compared with each other.The ferrite phase ratio values determined by AC and DC magnetometers were close to each other in case of all deformation extents and heat treatments.In contrast, the ferritscope device gave significantly lower ferrite contents in case of plastic deformed samples.The stronger the cold rolling reduction was the lower the measured ferrite content was.This phenomenon was explained by the change of the shapes of magnetization curves due to plastic deformation.The limits, disadvantages, and advantages of the applied methods were analyzed.