ASTM A240 S31803 S32205 Stainless Steel Flat Plate Excellent Weldability

Product Specification

ASTM A240 S31803 S32205 duplex 2205 cold rolled stainless steel flat sheet

UNS S31803, S32205 (sheet)

UNS S31803, S32205 is a duplex stainless steel characterized by:

• High resistance to stress corrosion cracking (SCC) in chloride-bearing environments
• High resistance to stress corrosion cracking (SCC) in environments containing hydrogen sulphide
• High resistance to general corrosion, pitting, and crevice corrosion
• High resistance to erosion corrosion and corrosion fatigue
• High mechanical strength - roughly twice the proof strength of austenitic stainless steel
• Physical properties that offer design advantages
• Good weldability

Standards

• UNS S31803, S32205
• EN number 1.4462
• EN name X2CrNiMoN 22-5-3
• W.Nr. 1.4462
• DIN X2CrNiMoN 22 5 3
• SS 2377
• AFNOR Z2.CND22.05.03

Chemical composition (nominal) %

Forms of supply

Flat sheets or plates

Mechanical properties

The following values apply to material in the solution annealed condition. Tube and pipe with wall thicknesses above 20 mm (0.787 in.) may have slightly lower values. For seamless tubes with a wall thickness <4 mm we guarantee proof strength (Rp0.2) values that are 10% higher than those listed below at 20°C (68°F) and than those listed at higher temperatures. More detailed information can be supplied on request.

At 20 °C (68°F)

1 MPa = 1 N/mm²
a) R_p0.2 and R_p1.0 correspond to 0.2% offset and 1.0% offset yield strength, respectively.
b) Based on L₀ = 5.65 √S₀ where L₀ is the original gauge length and S₀the original cross-sectional area.

Sheets in the cold-worked condition

Intended for oil and gas production

Impact strength

UNS S31803, S32205 possesses good impact strength both at room temperature and at low temperatures, as is evident from Figure 1. The values apply for standard Charpy-V specimens (10 x 10 mm, 0.39 x 0.39 in.).

The impact strength of welded UNS S31803, S32205 is also good, despite the impact strength values in the as-welded condition being slightly lower than for weld-free material. Tests demonstrate that the impact strength of material, welded by means of gas-shielded arc welding, is good in both the weld metal and the heat-affected zone down to -50°C (-58°F). At this temperature, the impact strength is a minimum of 27 J (20 ft lb). If very high impact strength demands are made on the weld metal at low temperatures, solution annealing is recommended. This restores the impact strength of the weld metal to the same level as that of the parent metal.

Figure 1. Curve showing typical impact strength values (Charpy-V) for UNS S31803, S32205. Specimen size 10x10 mm (0.39 x 0.39 in.).

At high temperatures

If UNS S31803, S32205 is exposed to temperatures exceeding 280°C (540°F), for prolonged periods, the microstructure changes, which results in a reduction in impact strength. This does not necessarily affect the behavior of the material at the operating temperature. For example, heat exchanger tubes can be used at higher temperatures without any problems. Please contact Huahon for more information.For pressure vessel applications, 280°C (540°F) is required as a maximum according to VdTÜV-Wb 418 and NGS 1606.

According to ASME B31.3 the following design values are recommended for UNS S31803 (UNS S31803, S32205)

Physical properties

Density: 7.8 g/cm³, 0.28 lb/in³

Thermal conductivity

1) Mean values in temperature ranges (X10^-6)

UNS S31803, S32205 has a far lower coefficient of thermal expansion than austenitic stainless steels and can therefore offer certain design advantages.

1) ( x10³ )

Corrosion resistance

General corrosion

In most media, UNS S31803, S32205 possesses better resistance to general corrosion than steel of type ASTM TP316L and TP317L. The improved resistance of UNS S31803, S32205 is illustrated by the isocorrosion diagram for corrosion in sulphuric acid, Figure 3, and the diagram showing the corrosion rates in mixtures of acetic and formic acid, Figure 4. Figure 5 shows the isocorrosion diagram for UNS S31803, S32205 in hydrochloric acid.

Impurities that increase corrosivity are often present in process solutions of acids. If there is a risk of active corrosion, higher alloyed stainless steels should be chosen, e.g. the austenitic grades UNS N08904 or UNS N08028, or the super-duplex grade UNS S32750.

Pitting corrosion

The pitting resistance of a steel is determined primarily by its chromium and molybdenum contents, but also by its nitrogen content and its slag composition and content. The manufacturing and fabrication practices, e.g. welding, are also of vital importance for actual performance in service.

A parameter for comparing the resistance of different steels to pitting, is the PRE number (Pitting Resistance Equivalent). The PRE is defined as, in weight-%: PRE = % Cr + 3.3 x % Mo + 16 x % N

The PRE number for UNS S31803, S32205 is compared with other materials in the following table:

* UNS S31803, S32205 has a chemical composition within UNS S32205, which is optimized within the UNS S31803 range in order to provide a high PRE value.

The ranking given by the PRE number has been confirmed in laboratory tests. This ranking can generally be used to predict the performance of an alloy in chloride containing environments. Because of the high Mo and N contents, the PRE number for UNS S31803, S32205 is significantly higher than what would be the case with lower Mo and N contents which are still within the limits of UNS S31803.

The results of laboratory tests, to determine the critical temperature for the initiation of pitting (CPT) at different chloride contents are shown in Figure 6. The chosen testing conditions have yielded results that match well with practical experience. Thus, UNS S31803, S32205 can be used at considerably higher temperatures and chloride contents than ASTM TP304 and ASTM TP316 without pitting. UNS S31803, S32205 is, therefore, far more serviceable in chloride-bearing environments than standard austenitic steels.

Figure 6. Critical pitting temperatures (CPT) for UNS S31803, S32205, ASTM TP304 and ASTM TP316 at varying concentrations of sodium chloride (potentiostatic determination at +300 mV SCE), pH6.0

Figure7.Resistance to stress corrosion cracking (SCC) in neutral chloride solutions with an oxygen content of about 8 ppm. Laboratory results for UNS S31803, S32205 of constant load specimens loaded to the proof strength at the test temperature.

Figure 8. Results of stress corrosion cracking (SCC) tests on UNS S31803, S32205, ASTM TP304L and ASTM TP316L in 40% CaCl₂, pH 6.5, at 100^oC (210^oF) with aerated test solution.

Stress corrosion cracking (SCC)

The standard austenitic steels ASTM TP304L and ASTM TP316L are prone to stress corrosion cracking (SCC) in chloride-bearing solutions at temperatures above 60°C (140°F).

Duplex stainless steels are far less prone to this type of corrosion. Laboratory tests reveal good resistance to stress corrosion cracking of UNS S31803, S32205. Results from the tests are presented in Figure 7. The diagram indicates the temperature-chloride range within which UNS S31803, S32205 and the standard steels ASTM TP304L and ASTM TP316L have low susceptibility to stress corrosion cracking.

Results of laboratory tests carried out in calcium chloride are shown in Figure 8. The tests have been continued to failure or a max. test time of 500 h.

The diagram shows that UNS S31803, S32205 has a much higher resistance to SCC than the standard austenitic steels ASTM TP304L and ASTM TP316L.

In aqueous solutions containing hydrogen sulphide and chlorides, stress corrosion cracking can also occur on stainless steels at temperatures below 60°C (140°F). The corrosivity of such solutions is affected by acidity and chloride content. In direct contrast to ordinary chloride-induced stress corrosion cracking, ferritic stainless steels are more sensitive to this type of stress corrosion cracking, than austenitic steels.

Laboratory tests have shown that UNS S31803, S32205 possesses good resistance to stress corrosion cracking in environments containing hydrogen sulphide. This has also been confirmed by available operating experience.

In accordance with NACE MR0175/ISO 15156 solution annealed and cold-worked UNS S31803, S32205 is acceptable for use at any temperature up to 450°F (232°C) in sour environments, if the partial pressure of hydrogen sulphide does not exceed 0.3 psi (0.02 bar) and its hardness is not greater than HRC 36. In the solution annealed and liquid quenched condition UNS S31803, S32205 is acceptable for use at any temperature up to 450°F (232°C) in sour environments, if the partial pressure of hydrogen sulphide does not exceed 1.5 psi (0.1 bar). According NACE MR0103 solution annealed and rapidly cooled UNS S31803, S32205, with hardness maximum HRC 28 is acceptable in sour petroleum refining.

Figure 9 shows the results of stress corrosion cracking tests at room temperature in NACE TM 01777 test solution A with hydrogen sulphide. The high resistance of UNS S31803, S32205 is shown in the figure by the fact that very high stresses, about 1.1 times the 0.2% proof strength, are required to induce stress corrosion cracking. The resistance of welded joints is slightly lower. The ferritic chromium steel ASTM 410 fails at considerably lower stress.

Results of tests according to NACE TM 0177 test solution A of UNS S31803, S32205 in welded and unwelded condition.

Intergranular corrosion

UNS S31803, S32205 is a member of the family of modern duplex stainless steels whose chemical composition is balanced in such a way that the reformation of austenite in the heat-affected zone, adjacent to the weld, takes place quickly. This results in a microstructure that gives corrosion properties and toughness roughly equal to that of the parent metal. Testing according to ASTM A262 Pre (Strauss´ test) presents no problems for welded joints in UNS S31803, S32205, which pass without reservations.

Crevice corrosion

In the same way as the resistance to pitting can be related to the chromium, molybdenum and nitrogen contents of the steel, so can the resistance to crevice corrosion. UNS S31803, S32205 possesses better resistance to crevice corrosion than steels of the ASTM 316L type.

Erosion corrosion

Steels of the ASTM 316 type are attacked by erosion corrosion if exposed to flowing media containing highly abrasive solid particles, e.g. sand, or to media with very high flow velocities. Under such conditions UNS S31803, S32205 displays very good resistance because of its combination of high hardness and good corrosion resistance.

Corrosion fatigue

UNS S31803, S32205 possesses higher strength and better corrosion resistance than ordinary austenitic stainless steels. Consequently, UNS S31803, S32205, has considerably better fatigue strength under corrosive conditions than such steels.

In rotary bending, fatigue tests in a 3% NaCl solution (pH = 7; 40°C (104°F); 6000 rpm), the following results were obtained. The values shown indicate the stress required to bring about rupture after 2 * 10⁷ cycles.

Heat treatment

Tubes are normally delivered in the heat-treated condition. If additional heat treatment is needed due to further processing, the following is recommended.

Solution annealing

1020 - 1100°C (1870-2010°F), rapid cooling in air or water.

Welding

The weldability of UNS S31803, S32205 is good. Suitable welding methods are manual metal-arc welding with covered electrodes or gas shielded arc welding. Welding should be undertaken within the heat input range 0.5-2.5 kJ/mm. Max. interpass temperature is 250°C (482^oF). Preheating or post-weld heat treatment is normally not necessary.

Bending

The starting force needed for bending is slightly higher for UNS S31803, S32205 than for standard austenitic grades (ASTM TP304L and TP316L). UNS S31803, S32205 can be cold-bent to 25% deformation without requiring subsequent heat treatment. For pressure vessel applications in Germany and the Nordic countries, heat treatment may be required after cold deformation in accordance with VdTÜV-Wb 418 and NGS 1606.

Under service conditions where the risk of stress corrosion crackingstarts to increase, heat treatment is recommended even after moderate cold bending, for example, where the material temperature is nearly 150°C (300°F) in an oxygen-bearing, environment with around 100 ppm Cl^-.

Heat treatment is carried out in the form of solution annealing (see under Heat treatment) or resistance annealing. Hot bending is carried out at 1100-950°C (2010-1740°F) and should be followed by solution annealing.

Expanding

Compared with austenitic stainless steels, UNS S31803, S32205 has higher proof and a tensile strengths. This must be borne in mind when expanding tubes into tube-sheets. Normal expanding methods can be used, but the expansion requires higher initial force and should be undertaken in one operation.

Applications

Due to its excellent corrosion properties, UNS S31803, S32205 is a highly suitable material for service in environments containing chlorides and hydrogen sulphide. The material is suitable for use in production tubing and flowlines for the extraction of oil and gas from sour wells, in refineries and in process solutions contaminated with chlorides. UNS S31803, S32205 is particularly suitable for heat exchangers where chloride-bearing water or brackish water is used as a cooling medium. The steel is also suitable for use in dilute sulphuric acid solutions and for handling, organic acids, e.g. acetic acid and mixtures.

The high strength of UNS S31803, S32205 makes the material an attractive alternative to the austenitic steels in structures subjected to heavy loads.

The good mechanical and corrosion properties make UNS S31803, S32205 an economical choice in many applications by reducing the life cycle cost of equipment.

Production process