Rohdetherm

Bright annealing

Bright annealing is the heat treatment of non-alloyed or low-alloyed steels and non-ferrous metals under a nitrogen-hydrogen atmosphere. The proportion of hydrogen varies here depending on the material and process temperature and ultimately naturally also due to the desired process results.

If the atmosphere consists predominantly of nitrogen (i.e. <= 5 % hydrogen) then no noteworthy reactions occur in the atmosphere of the annealing product. The protective gas (here for example forming gas 95/5) serves principally to eliminate oxidising gases from the process chamber, for example oxygen (air) or water vapour. With an increasing hydrogen content in the furnace atmosphere the effect of the reduction in surface oxidation increases in significance. At the same time the conductivity of the protective gas rises with an increase in the proportion of hydrogen. This also has a positive effect on the heating and cooling speeds of the annealing product. With certain material groups the treatment must be carried out with noble gases, e.g. with a hydrogen-argon mixture. Heat treatments under a pure hydrogen atmosphere take place in specially equipped furnace systems. Such furnace systems of various sizes are naturally included in our product range. The nitrogen-hydrogen mixtures can be provided here as readied protective gases (e.g. tank or bottle) or generated in our gas control units from the individual gases and delivered directly at the furnace.