Alleima® 254 SMO* (ESR) is a high-alloy austenitic stainless steel developed for use in seawater and other aggressive chloride-bearing media. The steel is electroslag remelted which gives a cleaner material free from segregations. The grade is characterized by:
- Excellent resistance to pitting and crevice corrosion
- High resistance to general corrosion
- High resistance to stress corrosion cracking
- Higher strength than conventional austenitic stainless steels
- Good weldability
Trademark information: Alleima® 254 SMO is a trademark owned by Outokumpu OY.
Standards
- UNS: S31254
- EN Number: 1.4547
- SS: 2378
Product standards
EN 10088-3
Suitable for production of flanges etc. according to ASTM A182 Grade F44.
Certificates
Status according to EN 10 204 3.1
Chemical composition
| C | Si | Mn | P | S | Cr | Ni | Mo | N | Cu |
|---|---|---|---|---|---|---|---|---|---|
| ≤0.020 | ≤0.80 | ≤1.00 | ≤0.030 | ≤0.010 | 20 | 18 | 6.1 | 0.20 | 0.7 |
Applications
Alleima® 254 SMO is used in the following applications:
- Equipment for handling seawater - for example, heat exchangers, cooling water systems, ballast water systems, firefighting systems etc.
- Equipment in pulp bleaching plants.
- Components in gas cleaning systems.
| Industrial categories | Typical applications |
|---|---|
| Chemical industry | Flanges |
| Petrochemical industry | Valves |
| Pulp and paper industry | Fittings |
| Oil and gas industry | Couplings |
| Rings | |
| Seals | |
| Bolts and nuts | |
| Shafts | |
| Forgings | |
| Discs |
Trademark information: 254 SMO is a trademark owned by Outokumpu OY.
Corrosion resistance
Stress corrosion cracking (SCC)
Ordinary austenitic steels of the AISI 304 and 316 types are prone to stress corrosion cracking in chloride-containing solutions at temperatures exceeding about 60°C (140°F). For austenitic steels, resistance to SCC increases with increasing nickel and molybdenum contents. The tables below give the results of two accelerated tests, showing that Alleima® 254 SMO has very good resistance to SCC.
Stress corrosion cracking tests in boiling 25% NaCL solution, pH=1.5. U-bend specimens.
| Steel |
Time to failure
|
Remark
|
|---|---|---|
| AISI 316 |
<150 h
|
Pitting
|
| 904L |
No failure (1000 h)
|
Crevice corrosion
|
| 254 SMO |
No failure (1000 h)
|
No attack
|
Intergranular corrosion
Alleima® 254 SMO/ESR has a very low carbon content. This means that there is very little risk of carbide precipitation during heating, for example, when welding. The steel passes the Strauss test (ASTM A262, practice E) even after sensitizing for one hour at 600-1000°C (1110-1830°F).
However, due to the high alloying content of the steel, intermetallic phases can precipitate at the grain boundaries in the temperature range at 600-1000°C (1110-1830°F). These precipitations do not involve any risk of intergranular corrosion in the environments in which the steel is intended to be used. Thus, welding can be carried out without any risk of intergranular corrosion.
Pitting corrosion
The high chromium content and particularly the molybdenum content give Alleima 254 SMO/ESR excellent resistance to pitting and crevice corrosion.
The high nitrogen content also improves pitting resistance. The results of laboratory determination of the critical pitting temperature (CPT) in 3 % NaCl shows that Alleima® 254 SMO/ESR has a far greater CPT than 904L and it possesses very good resistance in water containing chlorides. Alleima 254 SMO/ESR is, therefore, a suitable material for use in, for example, seawater.
Crevice corrosion
The weak point of conventional stainless steels is their limited resistance to crevice corrosion. In seawater, for example, there is a considerably greater risk of crevice corrosion under gaskets, deposits or fouling. Tests in natural seawater at 60°C (140°F) have shown that Alleima® 254 SMO/ESR can be exposed for prolonged periods, without suffering crevice corrosion.
For further information regarding corrosion resistance of Alleima® 254 SMO, please see the data sheet Seamless tube and pipe - Alleima® 254 SMO. 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.
Surface conditions
Square billets
Unground, spot ground or fully ground condition.
Round billets
Peel turned or black condition.
| Size | Tolerance | Length |
|---|---|---|
| mm | mm | m |
| 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.
| Size | Tolerance | Length |
|---|---|---|
| mm | mm | m |
| 75 - 200 (5 mm interval) | +/-1 | max 10 |
| >200 - 450 | +/-3 | 3 - 8 |
| Size | Tolerance | Length |
|---|---|---|
| mm | mm | m |
| 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 |
Other products
Mostly supplied in non-ESR condition
- Welded tube and pipe
- Seamless tube and pipe
- Fittings and flanges
Heat treatment
Billets are delivered in the hot worked condition. The following heat treatment is recommended.
Solution annealing
1150-1200°C (2100-2190°F), followed by quenching in water.
Mechanical properties
For billets testing is performed on separately solution annealed and quenched test pieces.
The following figures apply to material in the solution annealed condition.
At 20°C (68°F)
| Proof strength | Tensile strength | Elong | Hardness | |
|---|---|---|---|---|
| Rp0.2a | Rp1.0a | Rm | Ab | Brinell |
| MPa | MPa | MPa | % | |
| ≥310 | ≥340 | 675-850 | ≥35 | ≤260 |
| Proof strength | Tensile strength | Elong. | Hardness | |
|---|---|---|---|---|
| Rp0.2a | Rp1.0a | Rm | Ab | Brinell |
| ksi | ksi | ksi | % | |
| ≥45 | ≥49 | 98-123 | ≥35 | ≤260 |
1 MPa = 1 N/mm2
a) Rp0.2 and Rp1.0 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 S0 the original cross-section area.
Impact strength
Due to its austenitic microstructure, Alleima® 254 SMO/ESR has very good impact strength both at room temperature and at cryogenic temperatures.
Tests have demonstrated that the steel fulfils the requirements (60 J (44 ft-lb) at -196 oC (-320 oF)) according to the European standards EN 13445-2 (UFPV-2) and EN 10216-5.
At high temperatures
Intermetallic phases are precipitated within the temperature range of 600-1000°C (1110-1830°F). The steel should therefore not be exposed to these temperatures for prolonged periods. Minimum proof strength properties at high temperatures are based on datasheets seamless tubes and pipe. Since the tubes have thin walls the values should only be used as indicative values for billets.
| Temperature |
Proof strength
|
|
|---|---|---|
| °C | Rp0.2 | Rp1.0 |
| MPa | MPa | |
| min. | min. | |
| 100 | 230 | 270 |
| 200 | 190 | 225 |
| 300 | 170 | 200 |
|
400
|
160
|
190
|
| Temperature |
Proof strength
|
|
|---|---|---|
| °F | Rp0.2 | Rp1.0 |
| ksi | ksi | |
| min. | min. | |
| 200 | 34 | 40 |
| 400 | 27 | 32 |
| 600 | 24 | 29 |
|
700
|
24
|
28
|
Physical properties
Density: 8.0 g/cm3, 0.29 lb/in3
| Temperature, oC | W/m oC | Temperature, oF | Btu/ft h oF |
|---|---|---|---|
| 20 | 10 | 68 | 6 |
| 100 | 12 | 200 | 7 |
| 200 | 14 | 400 | 8 |
| 300 | 16 | 600 | 9.5 |
| 400 | 18 | 800 | 10.5 |
| 500 | 20 | 1000 | 11.5 |
| 600 | 21 | 1200 | 12.5 |
| 700 | 23 | 1300 | 13 |
|
Temperature, °C
|
J/kg °C
|
Temperature, °F | Btu/ft h °F |
|---|---|---|---|
| 20 | 485 | 68 | 0.12 |
| 100 | 510 | 200 | 0.12 |
| 200 | 535 | 400 | 0.13 |
| 300 | 565 | 600 | 0.14 |
| 400 | 585 | 800 | 0.14 |
| 500 | 600 | 1000 | 0.14 |
| 600 | 615 | 1200 | 0.15 |
|
700
|
625
|
1400 | 0.15 |
| Temperature, °C |
Per °C
|
Temperature, °F | Per °F |
|---|---|---|---|
| 30-100 | 16 | 86-200 | 9 |
| 30-200 | 16 | 86-400 | 9 |
| 30-300 | 16.5 | 86-600 | 9 |
| 30-400 | 16.5 | 86-800 | 9.5 |
| 30-500 | 17 | 86-1000 | 9.5 |
| 30-600 | 17 | 86-1200 | 9.5 |
| 30-700 |
17.5
|
86-1300 | 10 |
1) mean values in temperature ranges (x106)
| Temperature, °C |
MPa
|
Temperature, °F | ksi |
|---|---|---|---|
| 20 | 195 | 68 | 28.3 |
| 100 | 190 | 200 | 27.6 |
| 200 | 182 | 400 | 27.5 |
| 300 | 174 | 600 | 25.1 |
| 400 | 166 | 800 | 23.8 |
| 500 |
158
|
1000 | 22.5 |
1) (x103)
Hot working
Hot working should be carried out at a material temperature of 950-1200°C (1740-2190°F). Hot working of Alleima® 254 SMO/ESR should be followed by rapid cooling in air or water. Subsequent heat treatment should be carried out in accordance with the recommendations given for heat treatment.
Welding
The weldability of Alleima® 254 SMO/ESR is good. Suitable methods of fusion welding are manual metal-arc welding (MMA/SMAW) and gas-shielded arc welding, with the TIG/GTAW method as first choice. Preheating and post-weld heat treatment are normally not recommended.
In common with all fully austenitic stainless steels, Alleima® 254 SMO/ESR has low thermal conductivity and high thermal expansion. Welding plans should therefore be carefully selected in advance, so that distortions of the welded joint are minimized. If residual stresses are a concern, solution annealing can be performed after welding.
For Alleima® 254 SMO/ESR, heat-input of <1.0 kJ/mm and interpass temperature of <100°C (210°F) are recommended. A string bead welding technique should be used.
Nickel alloys with high molybdenum and chromium must be used as filler metals to have good corrosion resistance in as welded condition.
Recommended filler metals
TIG/GTAW or MIG/GMAW welding
ISO 18274 S Ni 6625/AWS A5.14 ERNiCrMo-3 (e.g. Exaton Sanicro 60)
ISO 18274 S Ni 6059/AWS A5.14 ERNiCrMo-13 (e.g. Exaton Sanicro 59)
MMA/SMAW welding
ISO 14172 E Ni 6625/AWS A5.11 ENiCrMo-3 (e.g. Exaton Sanicro 60)
ISO 14172 E Ni 6059/AWS A5.11 ENiCrMo-13 (e.g. Exaton Sanicro 59)
Machining
Machining Alleima® 254 SMO/ESR, as with other stainless steels, requires an adjustment to tooling data and machining method, in order to achieve satisfactory results. Compared to Sanmac 316/316L, the cutting speed must be reduced by approximately 55-60% when turning 254 SMO/ESR 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 316/316L.
Disclaimer: Recommendations are for guidance only, and the suitability of a material for a specific application can be confirmed only when we know the actual service conditions. Continuous development may necessitate changes in technical data without notice. This datasheet is only valid for Alleima materials.