Langley Alloys presented a technical paper at Stainless Steel World 2019, sharing our comparison of Ferralium® 255 with other super duplex stainless steels during the Duplex/Super Duplex session.
Stainless Steel World is the leading exhibition and conference for the stainless steel industry, with nearly 300 exhibitors and three days of technical presentations. As the originator of super duplex stainless steels and a leading supplier of high-performance austenitic, duplex and super duplex stainless steels, it was right for us to hold a prominent position at the event.
Rodney Rice, Business Development Director, commented:
"I was pleased to share our latest work during the Duplex/Super Duplex session, alongside fellow speakers from Butting, Nippon Steel, Kobelco Steel Tube and Outokumpu. It's an incredibly knowledgeable audience, drawn from the largest producers and end-users of stainless steel across the world.
"It was good to receive a positive level of interest and questions about our comparison of Ferralium® 255 and other super duplex stainless steels."
Ferralium® 255 was the very first super duplex stainless steel, invented by Langley Alloys in 1967. Several competing alloys have since come to market, based on subtle changes to composition to avoid our original patent. We are working with the University of Swansea to shed new light on the corrosion performance of these alloys.
The three alloys compared
- Ferralium® 255 (S32550, 1.4507, F61) contains approximately 2% copper, understood to significantly improve resistance to acids such as sulphuric, phosphoric and nitric acid.
- Alloy 32760 (S32760, 1.4501, F55, Zeron 100®) contains up to 1% copper and 1% tungsten. Tungsten is claimed to improve immunity to crevice corrosion.
- Alloy 32750 (S32750, 1.4410, F53, SAF2507) contains no more than 0.5% copper and no deliberate additions of tungsten.
Investigations with the University of Swansea
The technical paper explores the history of these super duplex stainless steels, the differences in their composition, a review of the prior art and literature on the influence of copper and tungsten, and the results of recent investigations with the University of Swansea and their leading analytical techniques.
Ferralium® 255 has been shown to provide superior performance in acids, as demonstrated by commercially available data from several sources. Potentiodynamic polarisation experiments indicate differences in performance between the three alloys, as well as features worth further investigation. Ferralium® 255 and S32750 were observed to re-passivate more quickly than S32760 at lower temperatures.
| Grade | UNS | Copper | Tungsten |
|---|---|---|---|
| Ferralium® 255 | S32550 | ~2% | None |
| Alloy 32760 (Zeron 100) | S32760 | Up to 1% | Up to 1% |
| Alloy 32750 (SAF2507) | S32750 | <=0.5% | None |