Page 113 of 561

SOLUTIONS: Aluminium

Metals and welding solutions:

Aluminium

Pure aluminium (Al) is a soft, easily shaped metal with low strength. It is characterized by low weight, excellent corrosion resistance and good electrical conductivity. The strength of aluminium can be considerably improved by the addition of small quantities of alloy elements. As an alloy, aluminium retains the same appearance as pure aluminium and approximately the same low weight, but strength can be compared to mild steel. Only a limited number of aluminium alloys are considered suitable for use on board ships.

2.09

AIMg 3 and AIMg 1 are seawater resistant aluminium alloys. When alloyed with copper and silicon, aluminium can be used for the manufacture of cast components (silumin).

When aluminium and its alloys come into contact with air, a refractory skin of oxide quickly forms on the surface. The melting point of aluminium oxide is over 2,000°C, considerably higher than that of aluminium, which melts at 660°C. Unless this layer of oxide is effectively removed during the welding operation, the difference in melting temperatures will make it difficult for the metal of the workpiece to bind with the filler.

112

Included oxides will also reduce the strength of the weld.

Thorough cleaning and the use of flux is therefore essential when gas welding aluminium.

Welding should be done immediately after cleaning, before a new oxide film has time to develop. Other characteristic properties of aluminium are a high coefficient of expansion, good electrical and heat conductivity, and the absence of colour change when heated to melting point. Filler materials for Aluminium in the

Unitor range are:

Coated electrode: ALUMlN-351N Gas and TIG welding rod: ALUMAG-235 Wire welding:

ALUMAG-W-235

For gas welding of aluminium it is required to use a flux that removes oxides. Use Unitor ALUFLUX-234F.