[Lang]

Andrew

Just looked at hardening steel in a number of different engineering sites.

Quite apart from heat considerations the steel must be of high carbon content to be hardened. The tracks probably are not of this composition but the pins and steel rollers may well be (not the rubber carrier rollers). Unless it is high carbon, heating does little to the final product eg you can heat and bend the standard mild steel used in fabrication work without greatly altering its structure.

Having said that, placing the tracks in a wood fire is highly unlikely to alter the qualities of either the track plates or the pins. Wood burns at about 600 degrees but charcoal burns at about 1150 degrees but quite a bit higher if oxygen fed eg blacksmith's bellows - enough to harden high carbon steel.

Tempering and hardening are two different things. Hardening takes temperatures of 1350 to 1500 degrees - way beyond a normal wood fire. This leaves a high carbon steel hard but brittle.

Tempering high carbon stee is a much finer operation and involves temperatures between 250 and 500 degrees depending on what result you want (wood chisels or lathe tools). There are all sorts of charts giving the correct temperature for the job required and they all involve shock cooling in water, oil or moving air. Tempering gives a hard finish but much less brittle than just straight hardened carbon steel.

If they were my rusty tracks I would chuck them in the fire!

P.S. In the days before pollution laws we often used to put blitz and even thin jeep wheels complete with hard as a rock tyres on them in a wood fire. Come back in a few hours and you have beautiful rims with no rust, free bolt threads and a few rings of wire where the tyres were. There was never a hint of buckling or weakness from this common method. Probably have to do it at night now to avoid a life sentence!

Lang