Welding Technology of Aircraft Box [Aluminum Box]
(1) Choosing welding wire is usually 301 pure aluminium wire and 311 aluminium-silicon wire.
(2) Selection of welding methods and parameters
Left welding is usually used. Torch and workpiece are at 60 degree angle. When the welding thickness is more than 15mm, the torch and workpiece are welded at 90 degrees by right welding method.
(3) Pre-welding preparation
The surface oxide film on both sides of weld groove is cleaned strictly by chemical or mechanical method.
Mechanical cleaning can use pneumatic or electric milling cutter, scraper, file and other tools, for the thinner oxide film can also be used 0.25mm copper wire brush grinding to remove oxide film.
Welding should be done immediately after cleaning. If the time is longer than 4 hours, it should be cleaned again.
(4) Characteristics of Aluminum and Aluminum Alloy Materials in Aluminum Box
Aluminum is a silver-white light metal with good plasticity, high conductivity and thermal conductivity, as well as anti-oxidation and corrosion resistance. Aluminum is very easy to oxidize to produce aluminium oxide film, which is easy to produce inclusions in the weld, thus destroying the continuity and uniformity of the metal, and reducing its mechanical properties and corrosion resistance.
(5) Welding Difficulties of Aluminum and Aluminum Alloy Material in Aluminum Box
It is very easy to oxidize. In air, aluminium is easily oxidized to form dense aluminium oxide film (thickness is about 0.1-0.2 um), with a high melting point (about 2050 C), far exceeding the melting point of aluminium and aluminium alloy (about 600 C). The density of alumina is 3.95-4.10g/cm3, which is about 1.4 times that of aluminium. The surface of alumina film is easy to absorb moisture. When welding, it hinders the fusion of basic metals and easily forms defects such as pore, slag inclusion and non-fusion, which results in the degradation of weld performance.