1. Circuit
Step-down Transformer
Converts high voltage AC to a lower voltage (220V to 80V-100V). This means the
output current is greater than the input current. This is due to the primary coil having
more windings than the secondary coil.
Smoothing Capacitor
Produces a more uniform direct current by smoothing the surges produced by the
rectifier.
Rectifier
- Allows current to flow in one direction only.
- Converts AC to DC.
- Consists of four diodes arranged so to allow current to flow in one direction only.
Circuit for Manual Metal Arc Welding
2. Safety
- Ensure equipment is well maintained.
- Wear protective clothing.
- Weld curtain/cubicle.
- Ventilation
3. Hazards
- Electric shock: Ensure conditions are dry, equipment is earthed and and insulated.
- UV Light radiation: Suitable weld shield/goggles. Use of welding curtain.
- Inhalation of fumes: Ventilation system.
4. Function of Electrode Coating
- Generates Carbon Dioxide shield to protect from oxidation by nitrogen and oxygen.
- Forms a slag.
- Facilitates striking of Arc.
5. Functions of Slag
- Fluxing action prevents contamination/oxidation of the weld by atmospheric gases.
- Allows the weld to cool slower, producing a better weld.
- Prevents cracks and brittleness in the weld.
Multi Run Welds
- Produces a finished weld that is more refined in structure than single run welds.
- Each run of welds has a post heating effect on the previous.