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AssigneeL'Air Liquide, Societe Anonyme pour l'Etude et l'Exploitation des Procedes Georges Claude
InventorsYannick Rancon, Eric Duchateau
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Heat treating metals by continuous longitudinal passage of metallic pieces in an elongated treating zone under controlled atmosphere having a high temperature upstream end where the controlled atmosphere comprises nitrogen and reducing chemical substances, such as hydrogen, possibly carbon monoxide, and a downstream cooling end under an atmosphere essentially formed by introducing nitrogen. In the high temperature upstream end, the nitrogen which constitutes the atmosphere is supplied by introducing nitrogen with a residual oxygen content not exceeding 5%, the reducing chemical substances being present at any moment in amounts at least sufficient to eliminate oxygen introduced with nitrogen. The nitrogen introduced in the downstream cooling end is substantially free of oxygen. Application of the process to the annealing of metallic pieces.
A process for heat treating metal, comprising continuously conveying the metal through an elongated treatment chamber having a first upstream heating zone and a second downstream cooling zone, continuously introducing from outside said chamber into said first zone a gas consisting essentially of nitrogen containing between 0.5 to 5% of oxygen plus reducing gas in an amount at least sufficient to react with and eliminate said oxygen, and continuously introducing from outside said chamber into said second zone a gas consisting essentially of nitrogen which is substantially oxygen-free.
Dependencies are inferred from the claim text.