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BS EN ISO 3506 replaces BS 6105. Part 1 covers bolts, screw and studs, part 2 nuts and part 4 tapping screws. The chemical compositions are common to the various parts. Austenitic grades, A1, A2, and A4 are shown and compared to bar grades, 303, 304, 349S17, 316, and 394S17. Mechanical properties for property class, 50, 70, and 80 austenitic bolts and studs and property class, 20H, 25H, 30H, and 40H tapping screws are tabulated and the fastener designations, such as, A2-70, and, A4-25H, described. Duplex FA, (ferritic-austenitic similar to 1.4462, (2205), of EN 10088-1), is a likely future grade for inclusion in the standard. Fastener grade selection is covered in annexes to the standards. The standards lists grades 1.4439, 1.4539, (904L), 1.4529, (6% molybdenum austenitic), and 1.4462, (2205,) as suitable for reducing the risk of chloride induced stress corrosion cracking failures in applications such as indoor swimming pools.
Note a new version of BS EN ISO 3506 was issued in 2022, and as expected this now includes both duplex and higher strength grades.
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This paper was originally published in The Structural Engineer, (Volume 82 Issue 9 4th May 2004), and reviews structural failures in swimming pool buildings, attributed to stress corrosion cracking of stainless steel and the progress made since it was identified where the risks of failure can occur. Pool building environments are reviewed in terms of water temperature, disinfection systems, (chlorine), humidity and condensation. Prevention of SCC, (stress corrosion cracking), failure is the joint responsibility of the designer, structural engineer and pool operator. Grade selection to avoid SCC involves considering grades such as 1.4547, 1.4529, 1.4565, or 1.4507, rather than the 1.4301, (304), and 1.4401 / 1.4404, (316) types, which are more suited to non stressed, non safety critical or load bearing applications.
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This paper was originally published in Stainless Steel Industry in December 2001 and reviews a range of building and construction projects, featuring stainless steels in both aesthetic and structural applications. Projects mentioned include the Bilbao Abandoibarra Bridge, Lloyds Building, (London), Petronas Towers, (Kuala Lumpur), the Court of Human Rights(Strasbourg) and Waterloo Eurostar Terminal, (London), where the stainless steel had to meet a design life of 125 years. Applications for both austenitic and duplex types are discussed in structural, architectural, tunnel and road applications. Swimming pool, plumbing (water) and chimney lining applications are also mentioned.
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Guidelines for the grade selection, design, fabrication, maintenance, cleaning and inspection of stainless steels items for use in swimming pool buildings. Avoidance of stress corrosion cracking, (SCC), of safety-critical, load-bearing components. (57)
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This Health and Safety Executive Sector Information Minute SIM 5/2002/18 outlines the background to stress corrosion cracking failure hazards to stainless steel items used in indoor swimming poll buildings. This follows on from roof failures in Switzerland in 1985 and more recently in the Netherlands and notes that the atmospheres of indoor swimming pool buildings are amongst the most aggressive ones found in building interiors, where stainless steels are used. The minute discusses the background, noting the effects of chlorine based water disinfection systems and the chloramines generated by body fluid excretions on stainless steel components under applied or residual tensile stress. The stress corrosion process is outlined and the susceptibility of grades, 1.4301, (304), and, 1.4401, (316), to SCC in swimming pool environments noted. Preventative measures, inspection procedures and recommended actions for HSE inspectors are also covered.
