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LC Engineering
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LC Engineering

MIG & TIG Welding – Engineering notes

MIG welding

  • Semi automatic process.
  • A consumable bare wire electrode fed continuously into the weld pool through torch by spool.
  • An inert gas, e.g. argon, has a fluxing action and creates a protective shield around the weld pool.
  • The feed and flow rate are set by the operator.
  • Does not produce slag.
  • Used on sheet metals.

TIG welding

  • Utilises a non-consumable tungsten electrode
  • An electric arc is formed between a non-consumable electrode and the metal being welded.
  • An inert gas such as argon creates a protective gas shield.
  • A filler metal is added manually.
  • No slag is produced.

MIG vs.... (More)

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Heat Treatment – Engineering Notes



  • The piece is heated to a cherry red colour and then cooled rapidly in water oils and brine.
  • At the cherry red colour the steel will have undergone structural changes (FCC to BCC, martensite) and the rapid cooling does not allow it to revert to its original condition.


  • Very hard and Brittle.



  • It is done by heating the article to a suitable temperature (500°C) below the reddening point of steel and then cooling it in oil or water.
  • The higher the temperature the greater the reduction in hardness and brittleness.
  • The temperature is gauged by... (More)
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A1 Leaving Cert Engineering Project Brief Example

A1 Leaving Cert Engineering Project Brief Example

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Submerged Arc & Resistance Seam Welding – Engineering

Submerged Arc Welding

  • Uses bare wire electrode.
  • Fed automatically from spool.
  • Generates electric arc to heat metal/
  • Flux in powder form.
  • Fed using a hopper.
  • Electric arc melts joint, flux and electrode.
  • Excess flux is collected and re-used.
  • Fully automated process.
  • Used on Low carbon steels.
  • E.g. Ship building and bridge construction.

Resistance Spot welding

  • Components to be joined are placed between two non consumable electrodes and pressed together.
  • The current is passed through the electrodes which generates the required heat.
  • A nugget weld (circular mark) is formed.
  • It is used on sheet metals.
  • The process is energy efficient and... (More)