Shielding gas

As an inert gas, a gas or gas mixture is called, which has the task to displace the air of the atmosphere, especially the oxygen of the air.

Food

Inert gas is often used in the packaging of food, so that they are protected from the air, from bacteria. The Schutzgasatmospäre is depending on to be packaged foods from natural, odorless and tasteless constituents of the air, such as carbon dioxide ( CO2) or nitrogen (N2 ) or as in the case of fresh meat from oxygen ( O2), varying their proportions depending on the product.

Inert gases are not additives within the meaning of the Food Act. They are food safe and need not be declared. Identification according to § 9 ( 7) of the additive approval required VO: " packaged in a protective atmosphere "

Metal Technology

Welding

In arc welding, the arc and the molten bath is protected by a protective gas prior to the ingress of atmospheric gases (N2, O2, H2). This prevents that the metal reacts with the oxygen in the air (corrosion, combustion ), or result in metallurgical or mechanical means pores melting. Especially important is a high quality gas protection for high-alloy steels but also for light metals such as aluminum, magnesium or titanium. Is the quality of the gas coverage inadequate may arise depending on the material and boundary conditions tarnish, carbon deposits, increased weld spatter, pore structure, or even impairments. In addition to the purely protective function can be influenced by the shielding gas selection but also the weld shape, the ability to bridge gaps, the ignition, the arc stability or droplet transfer.

A distinction is made according to DIN 1910-100 between gas metal arc welding ( MIG ) and tungsten inert gas welding ( WSG) and their sub- processes during arc welding. The gases used vary depending on the method, material, or special process requirements. Shielding gases for gas metal arc welding of unalloyed and low steels, eg CO2 or mixtures of argon and CO2. For high-alloy steels argon-rich mixed gases are generally used, which contain only a few percent O2 or CO2. Aluminum, magnesium or titanium to be welded typically argon or argon-helium mixtures. Are active components such as O2 or CO2 or H2 contained in the shielding gas is called according to DIN EN ISO 14175 and DIN 1910-100 of metal active gas welding. If only argon or helium or mixtures thereof used, it is called metal inert gas. The variety of standardized gas mixtures has become very large. As a mixture of the components argon, helium, carbon dioxide are also oxygen, hydrogen and nitrogen in question. A classification of shielding gases are the European standard DIN EN ISO 14175 " Gases and gas mixtures for arc welding and allied processes ".

A good shielding gas coverage depends crucially on the fluidic design of the welding torch and the correct choice of boundary conditions in the welding production. For the visualization and measurement of the gas flow and the resulting gas coverage on the workpiece both diagnostic and numerical methods of flow analysis are used in science and industry.

For diagnostic visualization of the gas flow, the methods of the Schlieren technique and the particle image velocimetry (PIV) are used. Due to the oxygen measurement, the quality of the inert gas shielding can be determined quantitatively in the light of the arc in the laboratory.

In addition to the methods of diagnostic flow analysis, the flow of shielding gas in the welding process can also be analyzed by means of numerical flow simulation. Advantages of numerical simulation are to visualize inside the welding torch and describe complex physical relationships temporally and spatially high resolved in the way currents in small, concealed areas. Cause-effect relationships can be very well recognized and attributed to their physical causes.

Härtetechnik

Also found in the protective gas hardening technology application, as in the hardening plant, nitrogen gas or hydrogen prevents oxygen changed to the hardening steel. Thus, the surface of the hardened workpiece stays shiny and bright at the same time are fewer residues that would have to be laboriously filtered out of the quench otherwise.

Electrical Engineering

In electrical shielding gas is used to reduce the conductivity in the vicinity of switch contacts. This is the spark suppression.