Forming gas

Forming gas is a collective name for gas mixtures of nitrogen (N ₂ ) or argon (Ar) and hydrogen (H ₂ ) with a slightly reducing effect . Forming gas is used as a protective gas in the hot processing of metals , such as soldering , welding (for root protection ), rolling , pressing and annealing . An early application of such gas mixtures was the creation of a protective atmosphere for the "in-shape annealing" of coils made of tungsten wire, from which the name was derived.

The hydrogen it contains has a reducing effect on metal oxides and prevents oxidation . Forming gases are non-toxic, but flammable if they contain more than 5.5 percent hydrogen. Therefore, if the hydrogen content is greater than 10 percent, the forming gas outlet must be flared or diluted.

Forming gas is also used to locate leaks in the ground. The gas mixture rising through the soil on the surface is to be measured with sensors.

Another application, which has since lost much of its importance, is the hypersensitization of photographic materials for astrophotography .

Forming gas can be produced by splitting ammonia in a so-called ammonia splitter or ammonia cracker, also known as a forming gas generator. The NH ₃ molecule is thermally split and a mixture of 25% nitrogen and 75% hydrogen is created:

${\displaystyle \mathrm {2\ NH_{3}\longrightarrow N_{2}+3\ H_{2}} }$

Individual evidence

1. ↑ Technical information on training .
2. ↑ Crystec Technology Trading GmbH: Ammonia splitter for the generation of forming gas .