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Revision for college students who are studying on an Automotive Body Repair course. Welding standards applicable for those in the body repair trade.
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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