Messer Griesheim Gmbh

Messer Greiesheim Gmbh

Peter Zylla

Gerhard Gross

Method of annealing nonferrous metal parts without stickers

When cold strip is annealed, diffusion welds, so-called stickers, frequently form on the strip surface. In order to avoid these, the cold strip, above 600.degree. C. (holding time) is coated by oxidation with a thin surface film which prevents the sticking together. Below 600.degree. C., during the cooling phase, this surface film is removed again by reduction. In the case of a protective gas comprising a hydrogen content greater than 5%, remainder nitrogen, carbon dioxide is preferably added as oxidizing agent. The process is controlled via a defined oxygen partial pressure. The reduction is performed via the hydrogen.

Process for avoiding stickers in the annealing of cold strip

A process to anneal a steel strip in an annealing furnace in an inert-gas atmosphere containing hydrogen, with reduced formation of carbon black and encompassing the phases of heating, retention and cooling, wherein on the surface of the steel strip are impurities containing carbon components, and wherein during the annealing, there is a reaction between the H.sub.2 and the carbon components of the impurities on the surface of the steel strip, whereby said reaction changes the composition of the inert gas atmosphere in the annealing furnace from an inert gas containing H.sub.2 into a gas mixture containing H.sub.2 and CH.sub.4, which forms an H.sub.2 --CH.sub.4 system, and wherein the annealing furnace is flushed during the phase of retention, the phase of cooling, or during both the phases of retention and cooling, as a function of at least one of the thermodynamic limit values of the H.sub.2 --C.sub.4 system.

Process to anneal steel strips in an annealing furnace without

A process to prevent the formation of adhesives when annealing a steel band having a low carbon content uses an inert gas consisting of nitrogen and hydrogen and includes the phases of heating up, holding time and cooling. The process is characterized in that during the holding time, the steel band is coated by oxidation with a thin coating which is then completely removed by reduction during the cooling phase.

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Krefeld, Germany

Peter Zylla