What is the difference between S32550 and S32760?

S32550 and S32750 are both super duplex stainless steels, based around a 25% chromium alloying addition. S32550 is supplied with a higher yield strength than S32760 in solid bar form and has a 2% copper addition that provides superior resistance to sulphuric acid.

Ferralium 255 was the very first commercially produced super duplex stainless steel. It was patented by Langley Alloys in 1967 and presented to the market under the Ferralium trademark from 1969. As such, it has more than 50 years of successful track record in the most demanding environments. The generic product composition was subsequently defined as UNS S32550 (DIN 1.4507).

The grade known as S32760 was originally developed by Mather & Platt and marketed as Zeron 100. Mather & Platt was a UK-based company, hailing from Manchester, focused on the manufacture of large-scale centrifugal pumps. The use of super duplex stainless steels for such applications was obvious, given the potentially aggressive solutions being handled, requiring significant corrosion resistance, strength and wear resistance. Hence, the team at Mather & Platt sought to optimise ease of casting and long-term performance of their pump bodies for more demanding applications.  The pump division of Mather & Platt was subsequently acquired by Weir Pumps, although the Manchester site and foundry closed. The Zeron 100 trademark is now held by Rolled Alloys Inc. Alloy 32760 (UNS S32760, 1.4501, F55) includes a deliberate addition of tungsten, claimed to selectively improve corrosion resistance.

The key differences between S32550 and S32760 are that S32550 contains up to 2% copper addition to support increased resistance to sulphuric acid. S32550 is also the only super duplex stainless steel to achieve a minimum yield strength of 85ksi (586N/mm2) as solid bar, where S32760 has a minimum of 80ksi (550N/mm2).

Ferralium 255 (S32550) is available only from Langley Alloys, as round bar from ½”-14” (12.7-355.6mm), plate up to 3” (76.2mm), pipe, flanges and fittings. We also stock S32760 as round bars from 5/8”-20” diameter (15.87-508mm), plate up to 3” (76.2mm) thickness, as well as pipes in scheduled sizes, flanges and fittings.

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For more information about our range of alloys, please contact Langley Alloys today.