Piet van der Horst

Piet van der Horst

In 1970 Piet made welding his trade en since then he never stopped learning about that trade. By now he is well past his retirement age, but not welding is still not an option for him. It is not just work, it is a passion.

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Gases for welding processes

Inert and active gases

Classification according to the standard In NEN-EN-ISO 14175 standard, gases are divided into main and subgroups. In this article we discuss four main groups of

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Introduction TIG welding

Important founders

The history of TIG welding starts in 1890 when C.J. Coffin receives a patent for welding in a non-oxidizing gas. He used a carbon rod as an electrode. Tungsten electrodes did not yet exist.

In 1926 this process was further developed by H.M. Hobart. He used helium for his tests. In the same year P.K. Devers also researched the TIG process but he used argon for his tests. And so it was that two names emerged for basically the same process, Heliarc and Argonarc.

It would take until 1941 before a patent was granted to Russel Meredith for the welding of aluminium and magnesium. Russel Meredith was employed by Northrop Aircraft. During World War II, pressure on the war industry to produce more and above all faster was high. At Northrop Aircraft the first aluminum and magnesium parts for aircraft were welded. The process then became known as Heliarc Welding.

At the beginning of 1950 Northrop Aircraft sold the process and the name Heliarc to the Linde division of Union Carbide. Linde had much more capacity to develop the process and the torches. Until then, only rooms filled with inert gas were used for welding.

The first torches

The first torches were very difficult to use; large, heavy and air-cooled. Gradually the torch as we use it today was developed. In 1960 Gene Gorman van Linde was granted a patent for a gas lens. He used a kind of sintered bronze. The gas lens made the gas outflow very stable and no longer swirled. This was particularly important for the use of helium. Helium is much lighter than argon and therefore more of it is needed. This causes swirls and oxygen can mix with the gas. This mixing has a negative influence on the welding result. The sintered bronze gas lens is still the best gas lens, but because of its price it is only used in very special applications.

In 1961, when the process was renamed GTAW, Gas Tungsten Arc Welding, another employee of Linde, Cliff Hill, was granted a patent for a gas lens based on very fine meshes piled up on top of each other. Cliff Hill was very important in the further development of the TIG process. He was the first to develop water-cooled torches.

However, it is not Linde, but two other American companies that market the Linde-style torches worldwide; CL and Weldcraft. Both companies were very closely involved in the aircraft industry.

The equipment

The equipment that was used were large and heavy transformers with rectifiers. It was far from easy to achieve a good welding result with them. It got a lot better when Miller came up with the Square Wave Form. It became even better when the circuit boards entered the equipment. The number of parameters that could be set became larger and larger. And since the introduction of the inverter, the parameters to be set are almost infinite.

The process numbers

The IIW, International Institute of Welding, renamed the process, TIG. This stands for Tungsten Inert Gas. The various possibilities of the TIG process were also given numbers, according to EN ISO 4063: 2009. These are the descriptions:

  • 141: TIG welding with tungsten electrode under inert gas with a solid wire or rod
  • 142: TIG welding without filler material / with consumable insert
  • 143: TIG welding with cored wire or rod
  • 145: TIG welding with a solid wire and a reducing gas(share)
  • 146: TIG welding with a wire and a reducing gas(share)
  • 147: TAG welding with tungsten electrode under protection of active gas
  • 147 is TAG welding. So that’s TIG welding with an active gas!? I’m not sure that the tungsten electrode will like this.

Sometimes you see the name “WIG” welding. This name is mainly found in the German-speaking countries. In German, tungsten is “Wolfram” and the process is called Wolfram Inert Gas or WIG. In recent years, however, more and more TIG has been used as the name for the process. In the Netherlands, welders who have been working for a long time often speak of Argon or Argon-Arc welding.

Properties of the process

Whatever you call the process, it has a few specific characteristics.

  1. It is a process with a very high purity of the weld metal.
  2. The process is applicable to all metals, ferrous and non-ferrous metals.
  3. The process can be very well automated and robotised
    1. With and without filler material
    2. In all welding positions

Other characteristics that can be experienced as limiting are:

  1. It is a very slow process
  2. It is a very hot process with a high heat input.
  3. Major deformation may occur, especially in stainless steel.
  4. The process is sensitive to draughts and can only be used in indoor areas.

Due to the slowness and the heat input, the TIG process can cause a problem with some materials. Especially with stainless steel. With the same heat input, this material deforms five times more than steel. This means that when welding stainless steel, it is necessary to look closely at how to weld and whether there are tensioning possibilities. The use of a copper support strip can, where possible, remove a lot of heat and thus prevent excessive deformation. This saves a lot of post-processing.

TIG welding without filler material

The TIG welding process can be carried out with or without filler material. When no filler material is used, and the welding is done manually, the welding is mostly cosmetic and does not have to meet high requirements. Above all, it has to look good.

In automated TIG welding, very high welding qualities can be achieved without filler material.

TIG welding with filler material

In the case of manual welding, the rod-shaped filler material is added by the welder. The length of these rods is usually one meter and the diameter depends on the chosen amperage. Nowadays there are also torches where the wire is fed automatically from a coil, cold or hot. This can significantly improve the efficiency of the process. The application of these torches has its limitations. The accessibility of the part to be welded is not always optimal or even not feasible at all.

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