Welding thick metal sheets efficiently: Submerged arc-, electro gas- and electro-slag welding

Submerged arc welding

In submerged arc welding, the arc is burning under a protective layer of flux and slag which shields and insulates the weld puddle from the atmosphere. That way, it is possible to obtain a high heat input which leads to a very high deposition rate.

As a result, thick metal sheets can be welded efficiently and without shielding gas. During the process, a high quality of the weld is achieved, within the weld as well as on the weld seam surface.

Despite its strengths, submerged arc welding is not suitable for every kind of application. For high-strength steel, for example, the process has, so far, been rarely used. Our research partner ISF is currently testing a version of submerged-arc welding that allows an efficient use also for high-strength fine-grained structural steel.

Electro-gas welding

Electro-gas welding is a fully mechanised version of GMA-welding for vertical butt joints. In the process, the weld pool is restricted by water-cooled copper sliding shoes on the front and back of the metal sheet while the metal is welded in an upward motion from bottom to top.

The use of electro-gas welding allows to weld the entire weld cross-section in one position with almost no distortion. This process is fast and efficient and requires only simple weld preparation. However, comparatively high investments for the systems technology are necessary that can, on the other hand, be redeemed quickly by making use of the advantages of the process. The challenges lie in reducing cracks and embrittlement caused by the high energy input.  We face those challenges by using process versions with reduced energy input that were researched and developed by our research partner ISF.

Electro-slag welding

In electro-slag welding, an arc is used under flux only for the ignition and extinguishes again after a short time. Afterwards, the resistance of the slag pool serves as heat source for melting the material. Copper sliding shoes on the front and back restrict and support the molten pool. During the welding they are moving, along with the torch, from bottom to top.

Electro-slag welding is suitable for metal sheets that can be welded in one go with nearly no limit in thickness. It is a highly efficient welding process, not only because of its minimal requirements for weld preparation but mainly because of its high effective welding speed which is due to welding in one pass. It is, however, necessary to make high investments at first. The challenge is, again, to avoid cracks and embrittlement, depending on the material.

Selecting the right process for your application

These three processes have different strengths and weaknesses. The right process for thick metal sheets is selected depending on your individual requirements and the material that is to be welded. Due to many years of experience in research and use of those processes we are able to analyze your situation precisely and find the right process together with you. Depending on your task, alternatives such as laser- and electron beam welding are also taken into consideration.

Finding the appropriate welding parameters

By choosing the right process, the task is not completely solved yet. Reproducible and high quality results are only achieved with correct parameters. In the laboratory of our research partner ISF, we provide of all necessary equipment to set up your welding situation as realistic as possible.

We also have access to the equipment necessary for examining the weld seam on very thick sheets. This enables us to optimize the parameters systematically and directly in terms of efficiency and quality in small cycles and thus to eliminate process-typical weak points.