{"id":3623,"date":"2026-09-16T11:08:24","date_gmt":"2026-09-16T08:08:24","guid":{"rendered":"https:\/\/www.defencemetal.com\/index.php\/en\/aisi-f255\/"},"modified":"2026-09-25T21:14:52","modified_gmt":"2026-09-25T18:14:52","slug":"aisi-f255","status":"publish","type":"page","link":"https:\/\/www.defencemetal.com\/index.php\/en\/aisi-f255\/","title":{"rendered":"AISI F255 \/ (1.4507)"},"content":{"rendered":"

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AISI F255 \/ (1.4507) \/ UNS S32520<\/h1>\n
DEFENCE METAL<\/span><\/p>\n
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F255 (Ferralium 255)<\/div>\n
UNS S32550 \u00b7 W.Nr. 1.4507 \u00b7 in ASTM A240: 24.0-27.0% Cr \u2013 4.5-6.5% Ni \u2013 2.90-3.90% Mo \u2013 0.10-0.25% N \u2013 1.50-2.50% Cu \u2013 C \u2264 0.04% \u2013 balance Fe. THIS IS THE ONLY ONE OF THE FIVE WHOSE COPPER IS BOUND BY THE SPECIFICATION (1.50-2.50%); copper does not appear in the PREN formula and does not raise PREN, its effect being on behaviour in reducing media. It is a ferritic-austenitic (super duplex) stainless steel; it is NOT PRECIPITATION HARDENABLE, NOT AGED, and its only heat treatment is solution annealing followed by a quench. ‘Ferralium 255’ is a TRADE NAME; ‘F255’ is NOT an ASTM class code \u2014 see ‘standart_notu’ for the detail.<\/p>\n
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Not to be confused with<\/div>\n

AISI F55<\/a><\/div>\n<\/div>\n<\/div>\n

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For what<\/div>\n
It is bought for mixed service where a reducing acid is present alongside chlorides: sour production equipment, pump and valve bodies, equipment seeing both seawater and process streams. The copper addition is what separates it from the other super duplex grades.<\/div>\n<\/div>\n
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Forms<\/div>\n
Round bar \u00b7 Flat bar \u00b7 Plate \u00b7 Sheet \u00b7 Pipe and tube \u00b7 Forgings. All forms are supplied to order.<\/div>\n<\/div>\n
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Standards<\/div>\n
THERE IS NO AMS. ASTM: A182 \/ SA-182 \u2014 GRADE F61 (forged flanges and fittings) \u00b7 A240 \/ SA-240 (plate, sheet and strip) \u00b7 A276 \/ SA-276 (bar and shapes, Condition A) \u00b7 A479 \/ SA-479 (bar and shapes) \u00b7 A789 \/ SA-789 (tube) \u00b7 A790 \/ SA-790 (pipe) \u00b7 A815 \/ SA-815 (wrought fittings). EN: 1.4507 \u00b7 10088-3. NORSOK MDS D54 and MDS D57 \u00b7 NACE MR0175 \/ ISO 15156 \u00b7 API 6A \u00b7 ASME Code Case 1883 (Langley Alloys). ASME Section IX welding group P-No 10H (Langley Alloys: ‘ASME IX: Group P10H’).
THE NAMING TRAP \u2014 THE MOST IMPORTANT ITEM: ‘F255’ IS NOT AN ASTM A182 CLASS CODE. The complete duplex class list of ASTM A182 is: F50 = S31200, F51 = S31803, F52 = S32950, F53 = S32750, F54 = S39274, F55 = S32760, F57 = S39277, F59 = S32520, F60 = S32205, F61\u2026<\/span><\/div>\n<\/div>\n
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Advantage<\/div>\n
Its minimum tensile strength in ASTM A240 is 760 MPa, above the 750 MPa of S32760 in the same table; its yield minimum of 550 MPa equals that of the other two super duplex grades.<\/div>\n<\/div>\n
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Welding<\/div>\n
FILLER METAL: AWS A5.4 E2553 (Langley Alloys gives ‘AWS 5.4 E2553-XX W39553’ for Ferralium 255 SD50 weld wire). The same source states why the filler is over-alloyed: ‘over-alloyed in nickel to ensure correct phase balance is maintained when welding with standard shielding and backing gases.’\u2026<\/div>\n<\/div>\n
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Limits<\/div>\n
THE TEMPERATURE CEILING is about 270-300 \u00b0C; the reason is 475 \u00b0C embrittlement. Industeel gives ‘-50 \u00b0C \/ +270 \u00b0C’ for super duplex; IMOA’s duplex family ceilings sit in the 250-315 \u00b0C band. NO SINGLE FIGURE IS GIVEN.<\/div>\n<\/div>\n
REQUEST A QUOTE<\/a>All stainless steels →<\/a>TECHNICAL DETAILS ↓<\/span><\/div>\n
Compiled from manufacturer data sheets \u00b7 confirm against the current specification before ordering<\/div>\n<\/div>\n<\/div>\n

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