Welding

Welding

1. Oxy-acetylene welding

   • Temperature approx 3100 Intense heat melts the joint edges Melted metal flow into one another and fuse Filler metal can be fed in by hand into weld pool
   • Types of flames
     • Neutral flame Equal amounts of oxygen and acetylene Temp 2800 Used to weld mild steel, stainless steel and cast iron Oxidising flame 1.5 parts oxygen to 1 part acetylene Temp 3500 Weld brass Carburising flame 0.9 parts oxygen to 1 part acetylene Weld aluminium 

2. Manual metal archive welding

   • Electricity  passed through  electrode Jumps between electrode and work piece Cause arc, produce heat, melt electrode and work pieceElectrodeTwo coresInner core same metal as metal being joined and consumed in weldOuter core flux hardened chemical powderFluxGas shield around weld pool which prevents oxidisationFlux elements of coating helps weld to formallySlaggyford forming elements bring impurities to topSlag slows cooling rate of weld giving stronger join Used on constructional steel

3. Metal inert gas

   • Also called mag Electrode on a spool and is fed through welding gun Oxidisation prevented by gas argon Semi automatic process Can be operated by robot Used on heavy and light plates No slag forms Example car production

4. Tungsten inert gas

   • Also known as tag Tungsten electrode is non consumable electrode Only creates heat and does not melt Protected from oxidisation by argon gas Filler metal could be fed in by hand Dc power source -stainless steel or steel Acer power source- aluminium

5. Submerged arc welding

   • Bare wire electrode is used Flux is in powered form Poured over the weld pool using hopper Flux protects weld pool Flux can be chipped off Fully automatic process Used on bridge and ship building

6. Resistance welding

   • Resistance spot Ideal for joining light sheet metal Electrodes are copper Good conductors Pressure is applied to the electrodes and current turned  Resistance between joints fuses a nodule of metal together at the end interface of both apples Used in car industry Robots control the spot welding Resistance seam  Roller electrodes Continously weld is formed Used to join aerosol cans or tin cans where air tight seal is required

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