aluminium in commercial vehicles - European Aluminium Association

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108 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VIII 1. Foreword Welding is the most common method of joining used in the manufacture of commercial vehicles and their bodies e.g. tanks, tippers, dumpers, chassis etc. The different physical, chemical and mechanical properties of aluminium compared with those of steel lead to the specific behaviour of aluminium during welding. In an atmosphere containing oxygen, a well anchored oxide layer builds up on aluminium. This layer has a melting point of some 2000°C against the melting interval of 630-660°C for the metal underneath. For quality welds this layer must be removed or at least broken up. Despite the fact that the melting interval of aluminium is by far lower than that of steel, the high thermal conductivity and the high melting energy make that, for arc welding, aluminium requires about the same amount of energy as steel. The thermal elongation of aluminium is twice that of steel and the loss in volume of the weld pool during solidification is important, causing distortion of the joint, if no remedial measures Welder (STAS) are taken. One method of minimizing distortion is to select a process with small energy input. TIG and MIG arc welding are the two processes most commonly used in the commercial vehicle industry. The technical progress made by other techniques such as plasma, laser, resistance or friction stir welding and the ever growing diversity of semi-finished products will encourage the application of such welding methods which have up to now been little used in the commercial vehicle industry.
EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VIII 109 2. TIG welding (Tungsten Inert Gas) In this process, an electric arc is struck between a refractory electrode made of tungsten and the workpiece, while a shroud of inert gas, usually argon, shields the electrode and protects the molten pool against oxidation. This process uses a high-frequen- cy stabilized AC power source. The oxide film is removed during the negative phase, while the positive phase ensures penetra- tion and cooling of the electrode. TIG welding is suitable for metal thicknesses between 1 and 6 mm. There is a TIG version where heli- um is used as the shielding gas. This helps achieving a high tem- perature in the arc but requires direct current with straight polarity. The effect of oxide film removal Contact (for current) Shielding Gas Shielding Gas Nozzle Filler Metal ‰ FIGURE VIII.1 PRINCIPLE OF TIG WELDING Arc ‰ ‰ ‰ is weaker but the welding power is higher and products 10 to 12 mm thick can be welded with a single pass. However this process is strictly for automatic welding only owing to the difficulty of keeping the arc at a constant controlled height within 0.5 mm. ‰ ‰ ‰ ‰ Tungsten Electrode Welding Power Source Weld Seam Work Piece
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ALUMINIUM IN COMMERCIAL VEHICLES
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Aluminium in Commercial Vehicles ha
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VII. FABRICATION . . . . . . . . .
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CHAPTER II ALUMINIUM IN TRANSPORT 1
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EUROPEAN ALUMINIUM ASSOCIATION ALUM
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CHAPTER III WHY USING ALUMINIUM 1.
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CHAPTER IV FREQUENTLY ASKED QUESTIO
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CHAPTER V ALUMINIUM ALLOYS FOR COMM
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Page 57 and 58: CHAPTER VI DESIGN AND CALCULATION 1
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Page 91 and 92: CHAPTER VII FABRICATION 1. INTRODUC
Page 107: CHAPTER VIII WELDING 1. FOREWORD .
Page 129 and 130: CHAPTER IX OTHER JOINING TECHNIQUES
Page 137 and 138: CHAPTER X DECORATION AND FINISHING
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Page 145 and 146: CHAPTER XI CORROSION RESISTANCE 1.
Page 153 and 154: CHAPTER XII CLEANING OF ALUMINIUM C
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aluminium in commercial vehicles - European Aluminium Association

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