We come immediately to the sodo, two are the main elements for choosing the coated electrode:
1) choice of the electrode
The choice of the electrode is determined by a series of factors that are of chemical, mechanical and operational order.
The chemical factors depend on the nature of the metal to be welded, ie from its composition and the mechanical characteristics that determine the importance of efforts that the piece can be subjected to operation, without a risk of breakage.
These factors define the nature of the metal to be used with welding and also the mechanical properties that must possess the metal deposited.
These two factors define the nature of the metal to be used with welding and also the mechanical properties that must possess the metal deposited.
The operating order factors include in particular:
• The type of welding machine used
• The vacuum voltage of the welding post
• The position of the joint and the thickness of the sheets to be welded
• The qualification of the staff
It is clear that the factors of chemical and mechanical order are decisive in the choice of the electrode, and it is to these criteria that are inspired by the subdivisions that appear in the following articles.
2) Type of coating
Electrodes with rutile coating.
Their name derives from the presence in the coating of a strong percentage of rutile which gives them an excellent weldability.
These electrodes are easy to use in all positions and can be used in alternating current even when the voltage of the welding machine is low enough, close to 50V.
Modern welders, almost all with inverter transformer to IGBT technology, exceed this voltage thoroughly, therefore their weldability is more facilitated.
The use of these electrodes must be avoided when the weld pieces are subject to a demanding stress operation. On the other hand they are particularly suitable for all current works of small and medium carpentry.
Electrodes with basic coating.
The metal deposited by these electrodes is characterized by a very low hydrogen content, for this reason they are called the LHE (Low Hydrogen Electrodes). The mechanical characteristics of the metal deposited are exceptionally good, especially with regard to the values of resilience and displacement towards the low temperatures of the transition curve; The low hydrogen content of the store allows you to create insensitive welds to cracks.
The basic nature of the slag produced by the fusion of the coating favors the refinement of the metal deposited, eliminating the most of the impurities from the fusion bath.
The basic electrodes are used for the construction of welds of the utmost importance and responsibility (naval constructions, boiler elements, pressure tanks) and above all are recommended for the execution of very constrained welds, for welding of common steels with carbon content Relatively high, of melted steels and mediocre weldability steels.
In the next articles we will talk about electrodes with rutil-cellulosic coating and cellulosic, high-yield, the maintenance modes of the electrodes and the calculation of consumption.
Ivan Merlo Gabriele