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Duplex stainless wire solves spring cracking problem
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Sandvik Coromant UK
: 08 October, 2004 (Company News) |
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Sandvik Materials Technology's duplex stainless steel grade, Sandvik SAF 2205 is being used for wire springs in electrical contact systems on railway locomotives.
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An electrical rail contact system was designed for a passenger railway in South East Asia using standard stainless steel grade 316L wire springs to hold contact points in place between the locomotive and the rail. After some time in operation, cracking was found in the springs. The problem was due to stress corrosion cracking (SCC), emanating from the ambient humidity, and the materials mechanical strength. The combination of the two factors led to eventual spring breakage.
Although breakage is not considered a major problem, there is the potential for arcing with the broken springs contacting the suspended rail. As a result, a review of possible alternative materials by the railway's owners and operators led to the selection of Sandvik's SAF 2205 duplex stainless steel.
Sandvik SAF 2205 duplex grade spring wire is characterised by high resistance to stress corrosion cracking and has much higher resistance than AISI 316L, particularly in chloride bearing and hydrogen sulphide environments. It also has superior mechanical strength. In addition, the grade demonstrates extremely good resistance to general corrosion, pitting and crevice corrosion, erosion corrosion and corrosion fatigue. It is suitable for service temperatures from minus 100° up to 300°C.
To date and over a year in operation, the Sandvik SAF 2205 springs have not shown any signs of cracking and the grade has been specified to replace 3I6L stainless in all repair and new contact spring applications.
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