WELDING & CUTTING
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WELDING CAST IRON
 
Cast iron is an alloy of iron with a carbon content of 2-5%, silicon content of 1-3% and upto 1 % manganese. The major types of cast iron are
  • Grey cast iron
  • Nodular cast iron
  • Malleable cast iron
  • White cast iron
Cast iron has very low ductility, low strength and is very brittle. It is generally alloyed or heat-treated for improving these properties.
 
The high carbon content adversely affects the weldability of cast iron. Out of the grades mentioned above, white cast iron is considered unweldable for all practical purposes. The other types can be welded successfully with the consumables available.
 
PREPARATION FOR WELDING
 
The following steps should be kept in mind before commencing the welding of cast iron
  • Joint angles should be wider than for mild steel
  • All sharp edges should be rounded off
  • Preferably use U-grooves
  • For repairing cracks, either gouge / grind the entire crack or drill small holes at each end of the crack
  • The welding should start from the centre of the crack and proceed in both directions
  • The absorbed oil and liquid should be removed before welding. If that is not possible, use an electrode giving a spray transfer for an anchoring buffer layer
  • In critical welds, buttering by a ductile layer helps in absorption of the contractional stresses, thus saving the crack-susceptible HAZ
 
 
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