Processes for the production of a controlled atmosphere for heat treatment of metals
AssigneeL'Air Liquide, Societe Anonyme pour l'Etude et l'Exploitation des Procedes Geroges Claude
InventorsPierre Claverie, Eric Duchateau, Pierre Karinthi, Philippe Queille
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Abstract
Substantially all residual oxidizing gas in a treating atmosphere which is inert or reducing, is eliminated by injecting into the atmosphere a gaseous silicon hydride at a temperature between 50 and 1,600.degree. C. and in amount such that the ratio R of the content of hydride to the content of oxidizing gas to be eliminated is within the range of 1.5 to 20. The rapid action of the trace amounts of hydride injected enables one to control with precision heat treatment processes by maintaining the residual oxidizing gas contents below predetermined very low thresholds.
Claims12
A process for the production of a controlled atmosphere substantially free of residual oxidizing gases for the heat treatment of metals in at least one treatment vessel, said atmosphere consisting essentially of inert or reducing gases which are pure or in a mixture, comprising injecting a silicon hydride in the gaseous state into said vessel in an amount such that the ratio R of the content of silicon hydride injected, to the content of oxidizing gases to be eliminated, is within the range of 1.5 to 20.
A process for the production of a controlled atmosphere substantially free of residual oxidizing gases for the treatment of metal powders in an oven including a heating zone at a temperature above 1,000.degree. C. and a cooling zone, comprising injecting a silane in an area of the oven upstream of the cooling zone at a temperature above 500.degree. C., in an amount such that the ratio R of the content of silane injected, to the content of oxidizing gases to be eliminated, is above 15 and less than or equal to 20.
A process for the production of a controlled atmosphere substantially free of residual oxidizing gases for annealing steel with a low carbon content in a bell oven, comprising effecting a first injection of silane during a temperature rise, at a temperature below 630.degree. C., in an amount such as to provide a first ratio R of the content of silane injected, to the content of oxidizing gases to be eliminated, above 5 and less than or equal to 20, and then effecting at least a second injection of silane during cooling with the silane being injected in an amount such as to provide a reduced second ratio R.
Dependencies are inferred from the claim text.