We've been carrying out development trials on the heat treatment of rail steels.
Our rail rolling process and plant layout at Scunthorpe Rail and Section Mill (SRSM) currently delivers rails to the cooling bank with an equalised thermal profile at the ideal temperature to initiate an enhanced cooling heat treatment process.
Plant trials for accelerated cooling of the rail head with forced air and/or air mist cooling through a series of pipe and hole/nozzle arrangements have allowed a range of flows, pressures, moisture contents, stand-off distances and treatment times to be assessed using direct and interrupted cooling conditions.
The trials have shown that by design of treatment profiles, productivity can be matched to typical rolling throughputs for non-heat-treated products.
The work will also allow balanced cooling conditions for the foot and oscillation requirements of the rail to be determined to ensure optimum rail straightness and minimised residual stress levels in the product once roller straightened.
In several trials using our patented HP335 rail grade, the results have shown that a running surface and through head hardness in excess of 400BHN can be achieved by heat treatment through SRSM.