Effects of the metal temperature and the metal surface condition on the fire spread rate along mild steel and aluminum cylinders have been studied experimentally for wide variations of the oxygen pressure, up to 10 MPa, and the test piece temperature, up to the melting points. Based on the experimental results, the mechanisms by which fire spread is controlled, and the dependence of the fire spread rate on the metal temperature and the metal surface condition have been discussed.
The experimental results show that the fire spread rate does not always increase with the increase of the metal temperature, but the two cases, the increase or the decrease, exist corresponding to the ranges of the oxygen pressure and the metal temperature. The curious dependency of the spread rate on the metal temperature is attributable to the variation of the heat transfer rate from the molten mass to the unburned solid caused by the change of the contour of the boundary surface between the molten mass and the unburned solid metal. The effect of the surface condition on the fire spread rate is small. In this case, the variation of the fire spread rate is mainly attributable not to the variation of the surface reaction rate or the heat transfer rate at the solid metal just above the molten mass, but to the variation of the heat transfer rate from the molten mass to the unburned solid.