Method for heat treatment of material to be worked on, especially of aluminium or magnesium alloys

In a method for heat treating metal pieces comprising aluminum or magnesium alloys in the form of ingots, rods, tubes, strips or billets, the heat treatment being of the type wherein the metal piece is subjected to a preheat cycle in a preheat apparatus followed by a heat treatment cycle in a heat treatment apparatus separate from and independent of said preheat apparatus, and subsequent cooling,

• the steps comprising:
• preheating said metal piece in said preheat apparatus during the preheat cycle, by direct flame impingement, whereby a rapid preheating of the metal piece may be accomplished;
• and thereafter
• transferring it to said heat treatment apparatus, and subsequently
• maintaining said preheated metal piece at a desired heat treatment temperature in said heat treatment apparatus, during the heat treatment cycle,
• the speed of the metal piece, if any, through each apparatus being independently adjustable, and adjusting the speed through each apparatus.