Thermit Welding
Crucible loaded with thermit mixture
- On ignition the iron oxide is reduced to iron and the aluminium oxidises
When reaction is complete the molten iron is tapped and cast into the mould
- The alumina floats on the iron which is allowed to overflow to remove the slag
- Risers allow free metal flow and must be cut off
- Heat from the molten iron partially melts the joint faces
Mould faces and parent metal are preheated with oxy-acetylene flames to ensure fusion and reduce thermal stress