Ferrite Measurement in Dulex St. Steel

Specifications:

Manufactured by	FISCHER Germany
Measurement	Ferrite measurement is very critical in duplex stainless steels.
Calibration	Ferrite measurement is calibrated with 3 standards varying from 14.1% to 86.2% ferrite

Role of Ferrite in Duplex Stainless Steel

Duplex stainless steel clad metals contain delta ferrite, which is in terms of ferrite no. (FN). The amount of ferrite presents in the deposits a function of chemical composition of the filler and base metals, welding process, type of shielding gas, welding procedure, and heat input during cladding. Excessive ferrite in duplex stainless steel claddings can result in poor ductility, toughness and corrosion resistance. Likewise insufficient ferrite can also produce inferior mechanical and corrosion resistance insufficient ferrite can also produce inferior mechanical and corrosion resistance properties. However, control of ferrite in duplex stainless steel cladding is essential to obtain the required mechanical and corrosion-resistant properties.

Problems with Duplex S.S

The main problem with duplex is that it very easily forms brittle intermetalic phases such as sigma, Chi and Alpha Prime. These phases can form rapidly, typically 100 seconds at 900 ºC. However shorter exposure has been known to cause a drop in toughness, this has been attributed to the information of sigma on a microscopic scale. Prolonged heating in the range 350-550 ºC can cause 475-ºC temper embrittlement. For this reason the maximum recommended service temperature for duplex is about 280ºC.