TIG orbital welding: Residual oxygen under control

With the new ORBmax residual oxygen meter, the market leader for orbital welding technology, Orbitalum Tools GmbH of Singen, Germany, sets a milestone for fast, exact detection of residual oxygen, and with it complete documentation of these parameters. At the same time, the new measuring method results in greater efficiency and higher quality.

The "Optical oxygen measurement via fluorescence extinction" method for welding technology (patent pending) is far superior to the conventional methods, using zirconium sensors: It requires no warm-up time whatsoever; reliably, quickly and precisely detects the oxygen share in the gas; unchecked alleged increasing of the measured value due to the formation of ozone is eliminated; the measurement is possible in all gas mixtures without manual switch-over (even with forming gas with a variable percentage of hydrogen).

The exact, fast detection of the oxygen content reduces the otherwise long flooding time of the forming gas. The operator can start the safe welding process considerably earlier. As a result, precious working time is saved and the gas consumption reduced.

Only inert gases may be used for TIG welding, e.g. argon of the purity level 4.6 or ultrapure 4.8. A low hydrogen share in the protective gas is recommended in many cases, as hydrogen reduces the residual oxygen which may be present in the welded seam which is important, as even the smallest amount of oxygen results in blue discoloration (oxidation) of the tungsten electrode and causes a zone with annealing colors in the material. Oxygen has an active combustion effect and it increases the temperature in the welding bath and the heat input into the basic material; it diffuses into the surface of the seam, also making stainless steel susceptible to corrosion in the long term.

For welding pipes in plant and equipment construction for the food processing, beverage, cosmetics and pharmaceuticals industries, medical and bio-technology as well as fine chemicals, comprehensive quality assurance is required and a procedure qualification is specified for the welded seams. For quality certification, not only the values from the power source, but also the residual oxygen values can be documented with the ORBmax. The need for a more in-depth inspection, for example with x-rays, is therefore eliminated.