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Stainless steel in construction
Stainless steel has unique properties which can be taken advantage of in a wide variety of applications in the construction industry. This paper reviews how research activities over the last 20 years have impacted the use of stainless steel in construction. Significant technological advances in materials processing have led to the development of duplex stainless steel pipe with excellent mechanical properties; important progress has also been made in the improvement of surface finishes for architectural applications Structural research programmes across the world have laid the ground for the development of national and international specifications, codes and standards spanning both the design, fabrication and erection processes. Recommendations are made on research activities aimed at overcoming obstacles to the wider use of stainless steel in construction. New opportunities for stainless steel arising from the shift towards sustainable development are reviewed, including its use in nuclear containment structures, thin-walled cladding and composite floor systems.
This paper seeks to summarise the recent technological advances in the stainless steel sheet which have had an impact on usage of stainless steel in construction. New applications which have emerged over the last 20 years are described. Areas of research needed to respond to current market and procurement challenges are discussed. Finally, new opportunities arising from the shift towards sustainable development are described.
Perhaps the most significant recent advance impacting the construction sector has been the use of duplex grades for structural applications, which offer a combination of higher strength than the austenitics (and also the great majority of carbon steels) with similar or superior corrosion resistance. Table 1 compares the composition and mechanical properties of the two widely used austenitic stainless steel coil, 1.4301 and 1.4401, with those of three duplex stainless steels. (The ferritics in the table are discussed in Sections 3 Expansion of construction applications over the last 20 years, 4 Research in response to market and procurement challenges.) Duplexes have tremendous potential for expanding future structural design possibilities, enabling a reduction in section sizes leading to lighter structures. It is worth noting that although they have good ductility, their higher strength results in more restricted formability compared to the austenitics.
In recent years there has also been a dramatic increase in the use of stainless steel profiles in which a focused laser beam is used to melt material in a localised area. A co-axial gas jet is used to eject the molten material from the cut and leave a clean edge with a continuous cut produced by moving the laser beam or workpiece under CNC control. There is no tooling cost, prototyping is rapid and turn around quick. The improvements in accuracy, edge squareness and heat input control mean that other profiling techniques such as plasma cutting and oxy-fuel cutting are being replaced by laser cutting.
Between 1989 and 1992, SCI carried out a research project to develop European guidance in the areas of material selection, design, fabrication and maintenance to ensure the safe and proper application of steel in construction. The project included forming a properties database, materials tests, member and connections tests, analysis of results, design recommendations and worked examples. The resulting guidance was published by Euro Inox in 1994 as the Design Manual for Structural Stainless Steel. Subsequently the draft pre-standard Eurocode 3 Part 1.4, giving rules for the design of structural stainless steel pipe fittings, was published in 1996, closely based on the Design Manual.