Super duplex stainless steels are grades with a combined austenitic-ferritic microstructure based on a chromium content of around 25%. Many grades meet this classification; the most widely used are set out below.
ASTM A182 F51 (S31803 / 1.4462)
F51 was the original caption for a 22% chromium duplex stainless steel. Manufacturers optimised the composition towards the top of the limits to improve pitting corrosion resistance, and this tighter specification is captioned F60, equating to UNS S32205. As a result, S32205 can be dual-certified as S31803 but not the other way round. It accounts for around 80% of overall duplex production. We stock S32205 from 5/8" (15.87mm) up to 450mm diameter solid bars, plus plate up to 3" (76.2mm) thick, pipes in scheduled sizes, hollow bars, flanges and fittings.
ASTM A182 F53 (S32750 / 1.4410)
F53 is the 25% chromium super duplex stainless steel originally developed by Alleima and marketed as SAF2507. Its higher chromium gives improved pitting corrosion resistance compared with F51, and its higher yield strength lets designers reduce section size in load-bearing applications. We stock S32750 solid bars from 5/8" to 20" (15.87-508mm) diameter, plate up to 3" (76.2mm) thick, plus pipes in scheduled sizes, fittings and flanges.
ASTM A182 F55 (S32760 / 1.4501)
F55 traces back to the development of Zeron 100 by Platt & Mather in Manchester, UK. It is a super duplex stainless steel based on a 25% chromium composition with an addition of tungsten. We stock S32760 solid bars from 5/8" to 20" (15.87-508mm) diameter, plate up to 3" (76.2mm) thick, plus pipes in scheduled sizes, fittings and flanges.
ASTM A182 F61 (S32550 / 1.4507)
F61 approximates Ferralium® 255, the original super duplex stainless steel invented by Langley Alloys. Launched in 1969, it has now provided more than 50 years of service in demanding applications. Compared with F53 and F55 it delivers increased strength and corrosion performance: its minimum yield strength exceeds 85ksi, where other grades are limited to 80ksi. It also contains up to 2.0% copper, which aids pitting corrosion resistance. We stock Ferralium® 255-SD50 from 5/8" to 14" (15.87-355.6mm) diameter solid bar, plus plate up to 3" (76.2mm) thickness, pipes, flanges and fittings.
| Grade | UNS | DIN | Max stocked bar diameter |
|---|---|---|---|
| S32205 (F60) | S32205 | 1.4462 | 450mm (17.7") |
| S32750 (F53) | S32750 | 1.4410 | 508mm (20") |
| S32760 (F55) | S32760 | 1.4501 | 508mm (20") |
| Ferralium® 255-SD50 (F61) | S32550 | 1.4507 | 355.6mm (14") |