More specifically, the temperatures associated with diffusion flames using ambient air as an oxidizer are not capable of melting steel. As expressed, this requires modification to the process and chemical reactions to reach meting temperatures.

However, the melting of steel can occur, which can be produced by exposure to diffusion flames, in residential and commercial buildings. If AL is present, as can be the case with the installation of flashing, the AL can melt at diffusion flame temperatures and drip onto steel, such as standing seam roofs. Further exposure to flames can then allow the AL to diffuse into the steel creating a eutectic metal. In the simplest terms and in this example, the eutectic metal is a mixture of steel and AL. The melting temperature of the eutectic metal will be lowered commensurate with the composition of the metals in the mixture. It is difficult to find data associated with the specifics of the melting temperatures with composition. The evidence consists of physical examples and application of fundamental knowledge of metallurgy.

I will post a photo of a section of steel roofing that has discrete holes that are a result of flame exposure and localized melting where the AL dripped on the steel roof.

Douglas J. Carpenter, MScFPE, CFEI, PE, FSFPE
Vice President & Principal Engineer
Combustion Science & Engineering, Inc.
8940 Old Annapolis Road, Suite L
Columbia, MD 21045
(410) 884-3266
(410) 884-3267 (fax)
www.csefire.com