Catalogo consumabili 2012

Metallurgy reminders
Welding of low alloyed construction steels
The notion of the welding ability of steel is very complex and depends on the function of the welded joint considered. However,
the main factor is the chemical composition of the steel, related to its elaboration mode.
General recommendations for the welding of construction steels
The main factors favouring the success of welding operations are characterised by:
• The cleanliness of the surfaces to assemble (suppress all traces of rust, grease, humidity…),
• The use of dry electrodes (furnace drying recommended at 300 °C or DRY version) for all security assemblies,
• Preheating is all the more necessary when the sizes of the parts to assemble are important and when the equivalent carbon
is important,
• The control of preheating temperatures (during the welding operation), in difficult cases, with thermal sensors or
temperature indicating pencils.
One should not forget that each welding problem could lead to different solutions and that the above table allows orienting
one’s choice without giving a unique solution. The aim of the table is that of defining, for a given grade, the most favourable
conditions for the success of the welding operation (the grades of steel are given in descending order of welding capability).
A distinction can be made between two types of welded joints:
• on the one hand, those that have a simple role of parts attachment, without having to answer to high mechanical
characteristics, this is true in most cases,
• on the other hand, those that will be particularly solicited during the service of the part and that will have to be treated
differently.
Generally, for “welding capacity” or “average welding capacity” steels, one should use basic coated electrodes non-or lightly
alloyed (according to the case). In the case of steels that are difficult to weld, one shall prefer to use austenitic electrodes
having a high ferritic ratio allowing the deposit of a ductile metal while affecting the base metal at a minimum. In all cases, the
coating should be perfectly dry.
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