Sandvik SAF™ 2205 is a duplex (austenitic-ferritic) stainless steel characterized by:
- High resistance to stress corrosion cracking (SCC) in chloride-bearing environments and 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 steels
- Physical properties that offer design advantages
- Good weldability
Suitable for production of flanges etc. according to ASTM A-182 Grade F51
Analysis according to ASTM A-479, UNS S31803.
Status according to EN 10 204/3.1
Chemical composition (nominal) %
Due to its excellent corrosion properties, Sandvik SAF™ 2205 is a highly suitable material for service in environments containing chlorides and hydrogen sulphide. The material is suitable for use in refineries and in process solutions contaminated with chlorides. Sandvik SAF™ 2205 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 Sandvik SAF™ 2205 makes the material an attractive alternative to the austenitic steels in structures subjected to heavy loads.
The good mechanical and corrosion properties make Sandvik SAF™ 2205 an economical choice in many applications, by reducing the life cycle cost of equipment.
|Industrial categories||Typical applications|
|Oil & Gas industry||Couplings|
In most media, Sandvik SAF™ 2205 possesses better resistance to general corrosion than steel types ASTM 316L and 317L. This improved resistance of Sandvik SAF 2205™ 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 Sandvik SAF™ 2205 in hydrochloric acid.
Impurities that increase corrosivity are often present in acid process solutions. If there is a risk of active corrosion, higher alloyed stainless steels should be chosen, e.g. the austenitic grades Sandvik 2RK65™ and Sanicro® 28, or the super duplex grade Sandvik SAF™ 2507.
The pitting resistance of a steel is determined primarily by its chromium and molybdenum contents, but also by its nitrogen content, slag composition and slag content. 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 numbers for Sandvik SAF™ 2205 and other materials are given in the following table
|Alloy||% Cr||% Mo||%N||PRE|
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.
Laboratory determinations of critical temperatures for initiation of pitting (CPT) at different chloride contents are shown in figure 6. The chosen testing conditions have yielded results that agree well with practical experience. Thus, Sandvik SAF™ 2205 can be used at considerably higher temperatures and chloride contents than ASTM 304 and ASTM 316 without pitting occurring. Sandvik SAF™ 2205 is, therefore, far more serviceable in chloride-bearing environments than standard austenitic steels.
Stress corrosion cracking
The standard austenitic steels of the ASTM 304L and ASTM 316L types 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 have shown the good resistance to stress corrosion cracking of Sandvik SAF™ 2205. Results from these tests are presented in figure 7. The diagram indicates the temperature-chloride range within which Sandvik SAF™ 2205 and the standard steels ASTM 304L and ASTM 316L can be used without risk of 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 500h.
The diagram shows that Sandvik SAF™ 2205 has a much higher resistance to SCC than the standard austenitic steels ASTM 304L and ASTM 316L.
In aqueous solutions containing hydrogen sulphide and chlorides, stress corrosion cracking can also occur in stainless steels at temperatures below 60 oC (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 Sandvik SAF™ 2205 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 MR 0175, solution annealed and cold worked UNS S31803 (Sandvik SAF™ 2205) 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), the proof strength of the material is not greater than 160 ksi (Rp0.2 <1100 MPa), and its hardness is not greater than HRC 36.
Figure 9 shows the results of stress corrosion cracking tests at room temperature in a NACE solution with hydrogen sulphide. The high resistance of Sandvik SAF™ 2205 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.
Sandvik SAF™ 2205 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 (Srauss´ test) constitutes no problem for welded joints in Sandvik SAF™ 2205, which pass without reservation.
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. Sandvik SAF™ 2205 possesses better resistance to crevice corrosion than steels of the ASTM 316L type.
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. Its combination of high hardness and good corrosion resistance enables Sandvik SAF 2205™ to displays very good resistance under such conditions.
Sandvik SAF™ 2205 possesses higher strength and better corrosion resistance than ordinary austenitic stainless steels. It, therefore, also possesses 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 tabulated values indicate the stress required to bring about rupture after 2 * 107 cycles.
|Specimen without notch||Specimen with notch|
For further information regarding corrosion resistance of Sandvik SAF™ 2205 please refer to datasheet, Seamless tube and pipe - Sandvik SAF™ 2205. The data should be considered in the knowledge that it may not be applicable for thick sections such as forgings.
Forms of supply
Sizes and tolerances
Round-cornered square, as well as round billets, are produced in a wide range of sizes according to the following tables. Larger sizes offered on request.
Unground, spot ground or fully ground condition.
Peel turned or black condition.
|80||+/-2||4 - 6.3|
|100, 114, 126, 140, 150||+/-3||4 - 6.3|
|160, 180, 195, 200||+/-4||4 - 6.3|
|>200 - 350||+/-5||3 - 5.3|
Sizes and tolerances apply to the rolled/forged condition.
|75 - 200 (5 mm interval)||+/-1||max 10|
|>200 - 450||+/-3||3 - 8|
|77 - 112 (5 mm interval)||+/-2||max 10|
|124, 134||+/-2||max 10|
|127, 147, 157||+/-2||max 10|
|142, 152, 163||+/-2||max 10|
|168, 178, 188||+/-2||max 10|
|183, 193||+/-2||max 10|
- Seamless tube and pipe
- Welded tube and pipe
- Fittings and flanges
- Strip electrodes and flux for surfacing
- Strip, annealed or cold-rolled to different degrees of hardness
- Plate, sheet and wide strip
- Forged products
- Cast products
Billets are supplied in the hot worked condition. The following heat treatment is recommended.
1020 - 1100 °C (1870-2010 °F), rapid cooling in water.
Testing is performed on separately solution annealed and quenched test piece.
At 20°C (68°F)
|Proof strength||Tensile strength||Elong.||Hardness Brinell|
|Proof strength||Tensile strength||Elong.||Hardness Brinell|
1 MPa = 1 N/mm 2
a) Rp0.2 and Rp1.0 correspond to 0.2% offset and 1.0% offset yield strengths respectively.
b) Based on L0 = 5.65ÖS0 , where L0 is the original gauge length and S0 the original cross-sectional area.
Sandvik SAF 2205™ 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 Sandvik SAF 2205™ is also good, although the impact strength values in the as-welded condition are slightly lower than for weld-free material. Tests have shown 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 27J (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 SAF 2205. Specimen size 10x10 mm (0.39 x 0.39 in.).
At high temperatures
If Sandvik SAF 2205™ is exposed to temperatures exceeding 280 °C (540 °F) for prolonged periods, the microstructure changes which results in a reduction in impact strength. This effect may alter the behavior of the material at the operating temperature. Contact Sandvik for advice. Testing is performed on separately solution annealed and quenched test piece.
Density: 7.8 g/cm3, 0.28 lb /in3
|Temperature, °C||J/(kg °C)||Temperature, °F||Btu/(lb °F)|
|Btu/(ft h °F)|
Thermal expansion, mean values in temperature ranges (X10-6)
Sandvik SAF 2205™ has a far lower coefficient of thermal expansion than austenitic stainless steels and can therefore offer certain design advantages.
|Temperature, °C||MPa||Temperature, °F||ksi|
1) (x103 )
The hot forming range for Sandvik SAF™ 2205 is 950-1200°C (1740-2190°F), followed by quenching in air or water. Subsequent heat treatment should be carried out in accordance with the recommendations given for heat treatment.
The weldability 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 of 0.5-2.5 kJ/mm. Maximum interpass temperature is 250 °C (480 oF). Preheating or post-weld heat treatment are normally not necessary.
Matching filler metals are recommended in order to obtain a weld metal with optimum corrosion resistance and mechanical properties. For gas shielded arc welding, Sandvik 22.8.3.L is recommended and for manual metal-arc welding, the covered electrode Sandvik 22.9.3.LR. These filler metals can also be used for welding Sandvik SAF 2205™ to carbon steels and stainless steels.
The machining of Sandvik SAF™ 2205, as with other stainless steels, requires an adjustment of tooling data and machining method in order to achieve satisfactory results. Compared to Sanmac® 2205, the cutting speed must be reduced by approximately 20-30% when turning Sandvik SAF™ 2205 with coated cemented carbide tools. Much the same applies to other operations. Feeds should only be reduced slightly and with care.
Detailed recommendations for the choice of tools and cutting data are provided in the data sheet for Sanmac® 2205.