WELDING PROCESS AND

STANDARDS

Aluminium & its alloys are likely to increase as a body building material as it is one third of the weight of similar strength steel

It is less corrosive than ferrous materials

Non magnetic and recyclable Can be MIG/TIG & Spot welded,

Riveted or bonded Grades currently used are

BS:5000,6000 & 7000 Alloys

Aluminium alloys stretch easier than steels & there is a requirement that tools be kept separate for their exclusive use to avoid corrosion & contamination with steels

Where contact between dissimilar metals are to be made & to avoid Electrolysis barrier sealants or (Drachomet) coated fasteners must be used

As the electric arc creates a weld pool that is exposed to the atmosphere there is danger of attack from Oxygen, Nitrogen & Water vapour

These atmospheric conditions affect the depth of penetration, influence the character of the arc & also control weld Spatter

MIG (metal inert gas); inert gas is only suitable for high alloy steels & aluminium & not for thin sheet steel

MAG (metal active gas) ideal for most car body panels & low alloy steels

Argon-mixtures are the most common shielding gases offering the coldest arc, minimum spatter & greatest tolerances

As CO2 contents rises, so does spatter & the arc is therefore more unstable & difficult to control

MAG Welding: 90% Argon, 5% Oxygen, 5% CO2. MIG Brazing: 70% Argon, 2% Oxygen, 5% CO2. Stainless Steel: 93% Argon, 2% Oxygen, 5% CO2. Aluminium: requires 2% Oxygen added to

promote the required initial flow

ARGON: Reduces splashing in the weld pool

Carbon Dioxide: Allows the formation of large droplets and reduces porosity

Oxygen: Lowers surface tension & makes the weld pool more liquid

Hydrogen: Lessens oxidation Nitrogen dioxide: prevents ozone

formation

B.S. 1140: is the industry Standard for Resistance welding

B.S. 4872-1: is the Standard for M.I.G. MAG Welding (Steel)

B.S. 4872-2: is the Standard for T.I.G /M.I.G.Welding (Aluminium & Alloys)

Is the specification for the approval & testing of Body Repairers in Fusion welding

Welds must be of a neat appearance. The root must be fully fused along the entire length of the

weld. The profile of the cap should blend in smoothly with the

parent material The weld should be significantly free from imperfections.

HOW IS THE WELD TESTED ? Penetration defects and lack of fusion can often be easily

detected by sectioning the welded area. An application of ‘acid’ to the sectioned welded joint

followed by bending the material in a press can identify defective welds .

Welding personnel are tested using metals of;

1,0mm thickness 2,0mm thickness

HOW IS THE WELD TESTED Visual Inspection of weld Sheer/peel test