welding of non-ferrous metals
Non-ferrous metals have a relatively broad application in the industry.
They are characterized by shine and good thermal conductivity; thus, they are frequently applied in production of hydraulic elements or car parts.
They may be divided into several groups, depending on their density, of light and heavy or, depending on the degree of fusibility, of easily and hard or very hard to melt.
Due to various properties of individual non-ferrous metals one must chose an adequate method and the right temperature in order to weld each of them.
Within this article we will attempt to briefly discuss methods of welding the three from amongst the most frequently applied non-ferrous metals or their alloys: copper, brass and titanium.
Pure copper is one of the harder melting metals which stems, among others, from a large thermal and electrical conductivity, ability to absorb hydrogen in liquid state and oxygen, fragility in temperature between 500 and 600˚C as well as low recrystallization of temperature.
Melting temperature amounts to 1083˚C whilst density – 8,96 g/cm³, which means that it belongs to heavy metals.
The most popular methods of welding copper include:
– manual method by means of covered electrode (for sheets with density above 3mm),
– TIG method, via alternating current for sheets with density below 1mm, direct current for thicker, in both cases with negative polarity on the electrode,
– MIG method, with direct current with positive polarity (used in sheets above 4mm),
– gas method by means of oxygen-acetylene flame.
Welding of brass
Brass is an alloy of two metals: hard melting copper and easy meting zinc, whilst the content of the later one amounts to between 10 and 45%.
It may also contain additions of other metals.
Melting temperature depends on the genre but it never exceeds 1000˚C. It has a relatively high density, amounting to between 8,44 and 8,75 g/cm³
For welding brass, the following is applied:
– gas method, oxygen-acetylene flame (for sheets above 4mm),
– TIG method via direct current with positive polarity or alternating current in case of the content in the aluminium alloy.
Welding of titanium
Titanium is a light metal with density of 4,5 g/cm³, whilst at the same time it is hard melting, with melting temperature of 1668˚C. Furthermore, contamination with other elements increases durability and hardness of titanium, whilst decreasing its plastic properties and weldability.
The content of hydrogen causes hydrogen embrittlement.
Prior to welding one must remove heat tints (blue, dark blue or brown), constituting nitriding or oxidation of welding joints.
The following methods are applied for welding titanium:
– electron welding (most efficient),
– submerged arc welding, applying direct current with negative polarity on the electrode (applied in case of sheets above 3mm),
– plasma welding.
TIG and MIG welding in case of titanium is sometimes applied, but it is not recommended due to arc wondering, coarse structure in the welded joint and broad HAZ zone.