Method for reducing carbon deposits during box annealing

In the box annealing of ferrous metal sheets, the occurrence of carbon deposits and staining is materially reduced by initially heating the sheet in a protective atmosphere which is essentially a mixture of N2 and H2 and then modifying the atmosphere so that during the soak period it contains at lea...

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Bibliographische Detailangaben
Hauptverfasser:	PODGURSKI, HARRY H
Format:	Patent
Sprache:	eng
Schlagworte:	CHEMISTRY GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUSMETALS OR ALLOYS MAKING METAL MALLEABLE BY DECARBURISATION, TEMPERING OR OTHERTREATMENTS METALLURGY METALLURGY OF IRON MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS
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Beschreibung
Zusammenfassung:	In the box annealing of ferrous metal sheets, the occurrence of carbon deposits and staining is materially reduced by initially heating the sheet in a protective atmosphere which is essentially a mixture of N2 and H2 and then modifying the atmosphere so that during the soak period it contains at least about 3% CO2, 3% CO, 4% H2 and 0.5% H2O, balance N2. Atmosphere modification is effected only after the sheet portions, which are exposed to the protective atmosphere, reach a predetermined, minimum replacement temperature within the range 1000 DEG - 1400 DEG F.