Abstract: A method for heat treating metallic strips inside a heat treatment chamber at a pressure greater than atmospheric pressure including passing the strips through at least one heating zone of the chamber and moving the strip through at least one cooling zone of the chamber. A first protective gas atmosphere containing nitrogen and hydrogen and/or helium is established in all but at least one cooling zone. The at least one cooling zone has a second protective atmosphere containing nitrogen and a second amount of hydrogen, the second amount of hydrogen is greater than the first amount. Nitrogen is introduced into the chamber, and a protective gas containing a third hydrogen content greater than the second hydrogen content is injected into the cooling zone, producing a gas exchange between one zone of the chamber having the first protective atmosphere and the cooling zone, and controlling the flow of introduction and injection.

Abstract: The invention concerns a method for metal strip heat treatment comprising: passing the strip inside a chamber through a heating zone, and a cooling zone, and establishing a first protective gas atmosphere containing nitrogen and a first hydrogen content in the chamber, except for the cooling zone, wherein is adjusted a second protective gas atmosphere containing nitrogen and a second hydrogen content higher than the first, introducing nitrogen into the chamber, injecting protective gas containing a third hydrogen content higher than said second content in said cooling zone, producing a gas exchange between one zone of the chamber having said first protective gas atmosphere and said cooling zone, and controlling the flow of said introduction and said injection.