WELDING. Q 5. INTRODUCTION. Welding is the joining of parts by FUSING them together Fusion involves HEAT and PRESSURE between the parts being joined Some techniques require pressure Other techniques just require very high temperatures and no pressure. IDEAL CONDITIONS FOR WELDING.
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YOU CAN TELL DIFFERENCE BETWEEN THEM BY:
IMPORTANT TYPES OF WELDING
Heat from the flame is capable of melting the joint edges until the metal melts and starts to flow
CARBURISING OXIDISING NEUTRAL
• Regulators cannot be interchanged with colour coding
• Acetylene has left handed thread fittings
• Flashback arrestors are placed on gas lines
• Hoses are colour-coded
• Regulators are fitted to cylinders with an over-ride valve
• Adequate ventilation systems
All work on the same principal of electric arc.
material to fill the gap between the two parts being joined. A slag is formed which protects the weld area from oxidation and minimises cracking of the weld as it allows the joint cool slowly.
APPLICATIONSUse to weld overlapped sheet metal, commonly used in the motor industry or where small scale spot welds are needed ie orthodontics- re-sizing molar brands
Energy efficient, limited work deformation, high production, easy automation, no filler metal requirements.
• To form a coating which protects the weld from oxidation
• It ensures a slow cooling rate for the weld
• It prevents cracking and brittleness
• It minimises impurities in the weld.
In manual metal arc welding (MMA), the flux electrode coating melts and gives off a gas to protect the weld from the surrounding air, protective slag coating forms on top of the weld.In oxy-acetylene welding the flame protects the weld area.
MIG and TIG welding use a gaseous shield to protect the weld area.SAW covers the weld area with a powdered flux.
• The welding station should be shielded to protect others in the workshop from the intense light produced by welding.
• The hazards of the area must be highlighted by signs.
and use well maintained machinery, where cables are properly secured, insulated and earthed.
Use a welding curtain to protect fellow colleagues/classmates from exposure to UV light