WaLLy863,
Steel wheels are not heat treated subsequent to fabrication. Current practice is to use a microalloy steel (HSLA-- high strength low alloy), which obtains its strength through a combination of small alloy additions (usually Nb, V, Ti and maybe Cu, Mo, & Cr, as well as N) and controlled thermomechanical processing (time, temperature, strain, etc. used during the sheet rolling process).
I am also including the reply that I originally posted in the Metal and Metallurgy forum:
Aluminum alloy wheels used in the automotive industry are generally castings produced in permanent molds. The alloy used is 356 or A356 (Aluminum Association designation). They are usually given a T6 heat treatment, which means that they are solution heat treated, then quenched, then artificially aged. A typical heat treatment schedule would look like this:
Solution heat treat at 540 C for 4-12 hours
Quench into hot water: ~ 65-100 C
Artificial aging treatment is usually 155 C for 3-5 hours
) the heat treatment process of aluminum or steel wheels (preferably both 
