ASME SA789 / 790 S32205 Duplex Stainless Steel Tubes

ASME SA789/790 S32205 Duplex Stainless Steel Tubes

Duplex stainless steel has developed into the third generation since its birth in the United States in the 1940s. Its main feature is that its yield strength can reach 400-550 MPa, which is twice that of ordinary stainless steel, thus saving materials and reducing equipment manufacturing costs. In terms of corrosion resistance, especially under the condition of relatively poor medium environment (such as seawater, high chloride ion content), the dual phase stainless steel has significantly better resistance to pitting, Crevice corrosion, stress corrosion and Corrosion fatigue than ordinary austenitic stainless steel, and can be comparable to high alloy austenitic stainless steel. It has excellent mechanical properties and welding performance in the range of -50~280 ℃.

1.1 Composition characteristics
The second generation duplex stainless steel is generally referred to as standard duplex stainless steel, characterized by ultra-low carbon and nitrogen content, with a typical composition of 22% Cr+5% Ni+0.17% N. Compared with the first generation duplex stainless steel, S2205 further increases nitrogen content and enhances stress corrosion and pitting resistance in acidic media with high chloride ion concentration. Nitrogen is a strong austenite forming element that can be added to duplex stainless steel to improve its strength without significantly damaging its plasticity and toughness, while also inhibiting carbide precipitation and delaying its formation σ Phase formation.

1.2 Organizational characteristics
The austenite and ferrite in the Solid solution of the duplex stainless steel at room temperature account for about half respectively (the ferrite content of the duplex stainless steel 2205 should be 30%~55%, and the typical value is about 45%), which has both two-phase structure characteristics, as shown in Figure 1. From the figure, it can be observed that the volume of austenite (white) and ferrite structure (black) are similar, and the two phases are alternately distributed in bands along the rolling direction of the steel pipe.
Duplex stainless steel 2205 retains the characteristics of high thermal conductivity, low linear expansion coefficient, resistance to pitting corrosion, crevice and chloride stress corrosion of ferritic stainless steel; It also has the advantages of good toughness, low brittle transition temperature, resistance to intergranular corrosion, good mechanical properties, and welding performance of austenitic stainless steel.

Specification

ASTM A789/A789M-20 Standard Specification for Seamless and Welded Ferritic/Austenitic Stainless Steel Tubing for General Service.

Equivalent Grade

Chemical Composition

Mechanical Properties

Physical Properties

Applications

• 1. Chemical process vessels, piping and heat exchangers
• 2. Pulp mill digesters, bleach washers, chip pre-steaming vessels
• 3. Food processing equipment
• 4. Oil field piping and heat exchangers
• 5. Flue gas desulfurization equipment