[ Duplex ]
[ Duplex ]
Duplex is not … Duplex stainless steels do not rate highly in any list of superlatives . They score highly in terms of corrosion resistance and toughness , and only slightly less highly in terms of heat resistance ; but they are not absolutely at the top of either list . So , what is the most corrosion-resistant metal ? The prize goes to iridium , a dense , brittle transition metal of the platinum group . Followers-up would include certain grades of stainless steel , aluminium , copper alloys and nickel alloys . What is the most heat-resistant metal ? This used to be tantalum carbide ( melting point : 4,000 ° C ), but recently it was pipped at the post by a new alloy , hafnium carbonitride ( HfCN ), a ceramic that melts at just over 4,000 ° C . For comparison , titanium melts at 1,668 ° C , duplex grade 2205 melts at 1,385 – 1,445 ° C , and superduplex grades at around 1,410 – 1,460 ° C ( comparable to nickel , 1,455 ° C ). And the strongest materials ? Strength and toughness can be measured in various ways , but the strongest material of all is probably graphene ( fracture strength is more than 125 GPa ). The most impactresistant metal is tungsten , with chromium , iron , titanium , vanadium and lutetium ( a rare earth metal ) all runners-up .
Duplex is … Now , what is the material that combines all these properties ( at least up to a point ), is composed of widely available , affordable materials and is easy to fabricate ? The answer , across a broad range of industries , would have to be
A supplier ’ s view
duplex stainless steel . Taking all factors into consideration – resistance to heat , corrosion and erosion , strength , price , formability , recyclability and life-cycle costs – duplex grades combine all the necessary properties to an extent sufficient to make them competitive compared with other stainless grades , let alone carbon steel or other materials . This combination of properties can be illustrated by several examples .
Architecture : Fondation Louis Vuitton , Paris When applying stainless steel , architects tend to favour austenitics 304 and 316 , as this normally provides sufficient corrosion resistance . However , when weight savings or structural integrity are important , they will turn to duplex grades . This is what happened at the Fondation Louis Vuitton , Paris . Its bold , complex design , signed by Frank
The Fondation Louis Vuitton , Paris . The photo on the right shows painted steel beams with duplex fasteners in the foreground , and in the background , a glass “ sail ” supported by a duplex stainless-steel grid ; towards the right , duplex plate connecting a wooden beam to a steel column .
We asked Rodney Rice , director of Langley Alloys , to describe the market conditions of the last 12 months : “ We see continuing high demand for duplex , and specifically super duplex , with strong demand from oil & gas and a drive towards energy security . Although people may instantly think of upstream exploration and extraction , where these grades are widely used on account of their high performance at competitive cost , demand is also strong from downstream applications in the form of pump and valve components . Applications involving exposure to seawater ( e . g . offshore wind power ) have also been positive . Fasteners , across a broad range of markets , continue to be a strong application . Water scarcity will continue to create demand for desalination , which consumes duplex and super duplex piping . Plate applications include mining , but also hydrothermal power and fertilizer production , both applications with strong growth potential .”
Gehry , has been compared to a ghost ship . Its main structure is surmounted by billowing glass “ sails ” supported by a grid made of 2205 duplex stainless steel . The wooden and steel components of the sails are joined by 540 duplex stainless-steel plates inserted into the wooden beams . This results in a weight saving of 30 % compared with an equivalent structure in 316 . Type 2205 is also applied for gutters , connectors and fasteners , tension rods and rails .
Deepwater oil & gas Another example of corrosion resistance combined with mechanical strength can be found in deepwater oil & gas . Longitudinally-welded or seamless umbilicals , which bundle together the various lines ( flowlines , power , data , water , chemicals , fluids , etc .) between subsea wells and the platform , often need to span long distances in deep water , so a material that can both resist corrosion and withstand high pressures is called for , such as super-duplex type 2507 . Flexible pipes or risers , used to convey oil or gas from seabed to surface , also require high grades . Depending on the depth , super-austenitics , duplex in lean ( 2101 ), standard ( 2205 ) or superaustenitic ( 2507 ) grades are applied . Duplex is also finding use in valves that handle monoethylene glycol ( MEG ). This chemical is used to inhibit hydrate formation in pipelines , which can cause blockages . Recently Oliver Twinsafe supplied double block and bleed valves for the MEG injection pump systems of an offshore project , made of A182 F55 super-duplex stainless steel .
Marine installations Oil & gas or wind platforms or solar power systems , being exposed to
16 Stainless Steel World April 2024 www . stainless-steel-world . net