51312-01504-UNS 82441 - A new duplex stainless steel grade for the process industries

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Product Number: 51312-01504-SG

ISBN: 01504 2012 CP

Author: Carolina Canderyd

Publication Date: 2012

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Process industries including pulp paper and biomass conversion are constantly in search of new cost-efficient materials solutions. Duplex stainless steels are attractive in this respect by virtue of their combination of high strength price stability and corrosion resistance compared to their austenitic counterparts. The range of duplex grades extends from the lean low-Mo grades and up to high-performance super- or hyperduplex. However a vast number of applications of stainless steels require neither of these two extremes but instead are focused around the well-established multi-purpose grade 316L/UNS S31603 (17.2Cr10Ni 2Mo). Up to the present the answer to finding a duplex alternative has often lead to use of the duplex grade S32205 (22Cr 5.7Ni 3.1Mo) but this may well be over-specified if the corrosion demands are in the 316L range. In this paper the property profile of the new duplex steel UNS S82441 (24Cr3.6Ni1.6Mo3Mn) is compared to 316L and S32205. This paper describes the results of localized corrosion testing according to ASTM G48 (pitting and crevice corrosion in ferric chloride) G150 (electrochemical testing in NaCl) G36 (stress corrosion cracking in MgCl2) and G123 (SCC in NaCl) for a variety of product forms. Corrosion in acid media is illustrated with the critical temperatures evaluated according to the MTI-1 (ASTM G157) method as the lowest temperature at which the extrapolated corrosion rate exceeds a 0.13 mm/year. Potential application areas for the new grade are foreseen within P&P processing in which there are advantages to be gained from the higher strength of the grade and its superior corrosion resistance in caustic environments such as white liquor.