Stainless steel welding
In the production of outdoor showers, the combination of design and functionality requires a meticulous approach, and welding emerges as the fundamental protagonist for obtaining uncompromising quality results.
Through a thorough understanding of metallurgical principles and material properties, it is possible to create outdoor showers that not only grace outdoor spaces, but stand up to the elements and everyday use.
In this article, we explore the centrality of welding in the construction of superior level outdoor showers, we analyze the phenomenon of passivation and we go into detail about TIG welding.
Welding of stainless steel: the importance of passivation
To deal with a topic such as welding, a fundamental step for steel processing, it is necessary to know its definition well.
By welding we mean a process by which a joint is made between two or more metal pieces which remains permanent, with or without the addition of material, so as to obtain the continuity of the welded pieces in the connecting sections.
Welding of stainless steel must always take into account a very important aspect such as mechanical resistance since the mechanical properties of the weld joint must be suitable for the service conditions.
In the case of welding on stainless steel, various phenomena take place which must be taken into account in order to perform a correct joining process. The main property of a stainless steel is passivation, i.e. the formation of an invisible and compact layer of chromium oxides and hydroxides which protects the metal from further oxidation and makes the steel stainless.
When welding is carried out, the passivation property is lost due to the high temperatures and this brings the percentage of chromium below the fateful 10.5% by weight, defined by the EN 10088-1 standard, as the minimum limit necessary to include a steel among the stainless.
However, practice and experience teach that already below 12% it is in some cases difficult to have correct passivation, therefore in stainless steel the process called sensitization must be categorically avoided.
Austenitic steel (high performance alloys) is welded more easily because it has lower thermal conductivity and a high coefficient of expansion. However, it requires heat treatment or a type of welding rod with low carbon content or with titanium.
We remind you that in the specific case of stainless steel, a welded joint made in a workmanlike manner and installed without any post-welding pickling and passivation treatment will be of much lower quality in terms of quality, safety and durability compared to a correctly welded joint. passivated and pickled. Pickling is that chemical intervention that allows us to remove oxides and surface residues (such as traces of welding).
What are the advantages of TIG welding?
All Inoxstyle showers are a single body completely welded through the TIG process. TIG is an abbreviation that stands for Tungsten Inert Gas, a name that indicates an arc welding technique with an infusible electrode (tungsten), under the protection of inert gas, which can be performed with or without filler metal.
This procedure offers significant advantages such as:
- speed of execution;
- adaptability to any working position;
- ease of control of the arc with consequent regularity of the deposit;
- regulation of current intensity within wide limits;
- powerful and concentrated thermal source.
This last characteristic means that very small thicknesses (up to 0.5 mm) can be welded with discrete welding speeds.
This welding technique was initially developed for the aeronautical industry during the Second World War to replace rivets on aircraft with much lighter welds with the same strength.
TIG welding has application limits due to the impossibility of using high currents: it is not possible to use TIG in direct current and direct polarization because the electrons arriving at the anode (piece to be welded) are unable to break the oxide .
As a result, alternating current TIG is the most used; it consists of a half-period of the wave in which the electrode is positive and the oxide breaks, then there is a half-period in which the electrode is negative in which the electrode rests thus limiting its overheating.
TIG realizations can then undergo a manual polishing and finishing treatment to alleviate the main visual characteristic, which can be described as a sort of visible cord.
You will be able to document these and other processes in the next Technologies & Materials articles!