F44 / S31254 / 1.4547

6% Molybdenum

Super Austenitic Stainless Steel

PREN = 42 to 45

Corresponding Standards:
EN/DIN 1.4547 EN10088-3
AFNOR Z1 CNDU 20.18.06 AZ
UNS S31254
AISI F44 (A182 / A276 / A479)
SS 2378
M650 Qualification of Manufacturer
Similar to:
NAS 254 NM
NAS 255 NM
UNS N08367
UNS N08926 (Formerly N08925)
254SMO® / 6Mo® / 6MOLY
Other Standards / Specifications:
NACE MR01-03
NACE MR01-75
ASTM G48 METH.A(50°/24H)
ASTM A262 Practice E
PED 97/23/EC
F44 / S31254 Round Bar - Size Range (Ex-Stock):
Forged/Rolled, Solution-annealed, Machined bars cut to length if required. Full mill Certs with goods.
dia. Metric dia. Imperial Tol.
10.00 0.394 BG h9
12.70 0.500 BG h9
16.00 0.630 BG h9
19.05 0.750 BG h9
22.23 0.875 BG h9
25.40 1.000 PLD k12
28.58 1.125 PLD k12
31.75 1.250 PLD k12
34.93 1.375 PLD k12
38.10 1.500 PLD k12
41.28 1.625 PLD k12
44.45 1.750 PLD k12
47.63 1.875 PLD k12
50.80 2.000 PLD k12
57.15 2.250 PLD k12
63.50 2.500 PLD k12
69.85 2.750 PLD k12
76.20 3.000 PLD k12
82.55 3.250 PLD k12
88.90 3.500 PLD k12
95.25 3.750 PLD k12
101.60 4.000 PLD k12
114.30 4.500 PLD k12
127.00 5.000 PLD k12
130.00 5.118 -0/+1mm
139.70 5.500 PLD k12
152.40 6.000 PLD k12
160.00 6.299 -0/+1mm
165.10 6.500 PLD k12
177.80 7.000 PLD k12
190.50 7.500 PLD k12
203.20 8.000 PLD k12
210.0 8.268 k12
230.60 9.079 -0/+1mm
256.00 10.079 -0/+1mm
281.40 11.079 -0/+1mm
306.80 12.079 -0/+1mm
332.20 13.079 -0/+1mm
357.60 14.079 -0/+1mm
408.40 16.079 -0/+1mm
457.2 18.000 k12
508.0 20.000 k12
Note: Non stock items are available ex-mill, in short lead times. Please contact us with your enquiry.
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Intoco, a UK based manufacturing & special steels stockholding company, specialise in no-compromise manufacture using state of the art CNC equipment, and the finest steels available. We are also a large stockholder of hot work tool steels, stainless steels (440c / 1.4125 / 4125 / X105CrMo17), duplex stainless steel (ASTM A182 A276 / AISI / F51 EN / DIN (Werkstoff) 1.4462 and X2CrNiMoN22-5-3, UNS 31803 / S31803 / S32205, Afnor Z2CND22-5Az, BS318S13, SS2377, BS332C15, EN (10283) 1.4770, branded steel SAF2205, URANUS 45N, FALC223) and Super Duplex stainless steel conforming to ASTM / AISI / F55 / UNS S32760 / 1.4501 and F53 / UNS S32750 / 1.4410 in round bar and plate / sheet form.

We are now stocking ASTM A182 / A276 / A479 ASME SA182 / SA276 / SA479 Grade F44 / UNS S31254 / 1.4547 EN 10088-3 / 6Mo / 6 Mo / 6% Mo certified to Norsok MDS R17 M630 / M650 / Nace MR 01 03 / MR 01 75 / ANSI ISO 15156 / ASTM G48 method A / EN ISO 3651 – 2A / ASTM A262 Practice E / PED 97/23/EC / ASTM A388 / API 6A PSL3 PSL4. This super austenitic material is NACE and NORSOK approved and has a PREN (pitting resistance equivalent number - an empirical relationship to predict the pitting resistance of austenitic and duplex stainless steels) of 42 to 45. "Super austenitic” grades have enhanced pitting and crevice corrosion resistance compared with the ordinary austenitic or duplex types. This is due to the further additions of chromium 20%, molybdenum 6 to 6.5%, and nickel 18% and is enhanced with the addition of Nitrogen 0.2%. It also conforms, or is similar to, ASTM A182 / A276 / A479 ASME SA182 / SA276 / SA479 Grade F44 / UNS S31254 / 1.4547 EN 10088-3 / 6Mo / 6 Mo / 6% Mo certified to Norsok MDS R17 M630 / M650 / Nace MR 01 03 / MR 01 75 / ANSI ISO 15156 / ASTM G48 method A / EN ISO 3651 – 2A / ASTM A262 Practice E / PED 97/23/EC / ASTM A388 / API 6A PSL3 PSL4. X1CrNiMoN20-18-7 / X1CrNiMoCuN20-18-7 / Afnor Z1 CNDU 20.18.06 AZ / SS2378 / SS 2378 / Brands 254SMO / 6Mo / 6MOLY / Norsok M630-MDS R17 BAR / M630-MDS R14 FORGINGS / M630-MDS R15 PLATE / 1.4529 / AL6XN / AL6XN PLUS / ALLOY 926 / ALLOY SSC-6MO / INCOLOY 25-6 HN / INCOLOY 25-6 MO / NAS 254 NM / NAS 255 NM / UNS N08367 / UNS N08926 (Formerly N08925) / URANUS B25

Super-Austenitic 1.4547 / 31254 / F44 Stainless steel Acier, inoxydable, Rostfreier, Stahl, Acciaio, Inossidabile, Aco, Inoxidável, Acero, Inox, Inoxidables, Rostfrei, Roestvrij material. The nickel and chromium contents of this alloy make it resistant to a wide range of corrosive environments. The alloy is especially resistant to non-oxidizing acids such as sulphuric and phosphoric. The high molybdenum content and nitrogen provide resistance to pitting and crevice corrosion, while copper enhances resistance to sulphuric acid. Alloy 254SMO / 6Mo / F44 is a fully austenitic alloy containing 6% molybdenum and offering excellent corrosion resistance in a wide variety of aggressive, aqueous environments. It replaces the conventional, austenitic stainless steels (AISI 316 and 317), where their capabilities are pushed to their performance limits. The alloy, therefore, falls into a “super austenitic stainless steel” category. It can also represent a cost-effective alternative to the higher nickel alloys in some marine and chemical processing environments. One of the outstanding attributes of S31254 / 1.4547 alloy is its resistance to environments containing chlorides or other halides. This alloy is especially suited to handle high-chloride environments such as brackish water, sea water, caustic chlorides and pulp mill bleach systems. Applications include chemical and food processing, pulp and paper bleaching plants, marine and offshore platform equipment, salt plant evaporators, air pollution control systems, and condenser tubing, service water piping, and feed-water heaters for the power industry.

EN 1.4547 – 254SMO® is an austenitic stainless steel which due to its high molybdenum content possesses very high resistance to pitting and crevice corrosion. The steel grade was developed for use in halide-containing environments such as seawater. EN 1.4547 also shows good resistance to uniform corrosion and, especially in acids containing halides, this steel grade is superior to conventional stainless steel. Due to its high nitrogen content EN 1.4547 has higher mechanical strength than most other austenitic stainless steels. It is non-magnetic in the annealed condition but may become slightly magnetic as a result of cold-working or welding. Corrosion resistance - Uniform corrosion: The high content of alloy materials gives the steel exceptionally good resistance to uniform corrosion. Acids and acid solutions containing halide ions are very aggressive and EN 1.4547 is preferable to use. Examples of such acids are hydrochloric acid, hydrofluoric acid, chloride contaminated sulphuric acid, phosphoric acid and pickling acids based on nitric acid and hydrofluoric acid solutions. Intercrystalline corrosion: EN 1.4547 has a very low carbon content. This means that there is very little risk of carbide precipitation in connection with heating. On the other hand there is a risk of precipitation of intermetallic phases in the temperature range 600-1000° C. These precipitations do not involve a risk of intercrystalline corrosion in the corrosive media where this steel is used. Thus welding can be carried out without risk of intercrystalline corrosion. Stress corrosion cracking: Conventional steels of the 1.4301 and 1.4401 type are sensitive to stress corrosion cracking (SCC) under certain conditions, i.e. a special environment in combination with tensile stress in the material and often also an elevated temperature. Resistance to SCC increases with the increased content of nickel and molybdenum. This implies that the high-alloyed EN 1.4547 has very good resistance to SCC. Pitting and crevice corrosion: Resistance to pitting corrosion and crevice corrosion is determined mainly by the content of chromium, molybdenum and nitrogen in the material. This is often illustrated by using the pitting resistance equivalent (PRE) for the material, which can be calculated using the formula PRE = %Cr + 3.3 x %Mo + 16 x %N.

The above text is given as an overview of Super Austenitic Stainless Steel and is not to be relied upon for a specification.