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SOLUTIONS: Stainless Steel

2.06

Duplex Stainless Steel (Austenitic – Ferritic) The duplex stainless steel consist of a microstructure of about 50% ferrite and 50% austenite. They were developed to provide a higher strength, corrosion resistant alternative to the 300 series austenitic stainless steel. Compositions are modified to favour the high ferrite levels by increasing the chromium to 22-26%, increasing molybdenum to 2-5%, decreasing the nickel to 4-8% and adding copper up to 2%. These compositions provide excellent resistance to pitting, crevice

corrosion and stress corrosion cracking. Due to the high yield strength of duplex stainless steel the plate thickness can be reduced considerably in comparison to austenitic stainless steel. Weight savings can be up to 25%, however, the main reason for the increased use of duplex is that the resistance against pitting corrosion is superb compared to austenitic stainless steel. Duplex stainless steel is used for applications such as tanks, cargo loading pipes, heating coils, ladder material.

Duplex stainless steel has good weldability but great care must be taken to use the correct consumable and to follow the welding procedure. Composition (%)

Manufacturer Grade

Cr Ni Mo N Cu Other PREN 23% Cr Mo-free Duplex Stainless steel Duplex stainless steel grades. Avesta SAF 2304 23 4 – 0,1 – – 25 Creusot Ind. UR 35N 23 4 – 0,12 – – 25 Sandvik SAF 2304 23 4 – 0,1 – –

25

22% Cr Duplex Stainless steel Avesta

2205

22 5,5 3 0,16 – Mn 1.5 Böhler A 903 Creusot Ind. UR 45N 22 5,3 3 0,17 – –

35

Fabr. de Fer. 1,4462/PRE35 Krupp

Falc 223

Mannesmann A F22(1,4462) 22 5,5 3 0,14 – – 34/35 Nippon Kokan NK Cr22 Sandvik SAF 2205 Sumitomo SM 22Cr TEW Remanit 4462 Valourec VS 22

Product forms

May be welded with

all product forms plate, bars, forgings pipe

DUPLEX-325N Electrode product forms depending on manufacturer

IDUPLEX-222

TIG-rod

Duplex Stainless steel has the following characteristics: • High resistance to stress corrosion cracking. • Increased resistance to chloride ion attack. • Very weldable.

• Have higher tensile and yield strength than austenitic or ferritic stainless steel. • Grade: 2205.

• Unified numbering system UNS: S 31803. 70