ance-free rails
is to grind or mill the rail at regular intervals. Previous track tests have shown that
the harder the rail steel, the slower the crack initiation and propogation rate. However, Frank says that Voestalpine found during development that even steels with a pearlitic microstructure, which forms following premium heat treatment, and a hardness of up to 440BHN, will still develop headchecks although they are proven to extend rail life significantly while offering increased maintenance intervals compared with previous steel grades such as non heat- treated R260. High strength pearlitic rail is now considered a standard in Europe following the recommendations of the InnoTrack project with rails of this type widely accepted by infrastructure managers during studies conducted between 2006 and 2009. While pearlitic steels are now the benchmark, Voestalpine says that a heat-treated bainitic steel, which was found in early studies to offer increased resistance against crack initiation and propagation due to its refined microstructure, was recognised as holding the greatest potential for producing a maintenance- free rail. As a result, Frank says that Voestalpine experimented with three different metallurgical steel types over a period
Left: Track testing of Dobain is currently underway in Germany (pictured) and Austria.
Below: Dobain is proven to be headcheck- free even after 500,000 passes on Voestalpine’s rolling load stand.
about further track testing and certification processes.
Frank says Dobain was developed to tackle the continuing problem of headchecks which are a typical sign of surface RCF and tend to appear in under-maintained medium to wide- curvature track. Headchecks result from fine cracks on the surface of the rail following prolonged use. While different types of pearlitic steel grades and anti- headcheck profiles are available, they all remain susceptible to headchecks at some stage of their life and at present the only way of countering this problem
IRJ December 2012 19
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