Development of cast steel back-up roll

The present study concerns the development of a novel casting process for a heavy cast steel back-up roll. Total weight of the roll was 50 000 kg and the mould was about 7 m tall. A 'naturally pressurised' gating system was employed to avoid air and inclusion entrainment and to ensure smooth filling. In this way, high quality liquid steel was introduced into the mould. The gating system included an offset stepped pouring basin with stopper, hyperbolic tapered down-sprue with 113 mm entrance diameter and 63 mm exit diameter, radiused transition between vertical down-sprue and horizontal runner, and tangential ingate. The thickness of the sand lining of the cast iron dies at the barrel and journals was optimised by computer simulation to guarantee that the casting solidified progressively towards the feeder. In addition, all shrinkage was arranged to be completely located in the feeder by use of insulating boards and exothermic powder. The potential for sound castings to be produced with zero defects was demonstrated, although other castings appeared to require a sliding seal to allow the mould to contract longitudinally to avoid cracks.