Thermit Welding and Its Applications

Thermit welding:

  • For welding of high thickness materials this technique can be preferred.
  • Thermit mixture is initially heated upon 1200 by using the magnesium ribbon or rods.
  • At this temperature, thermit reaction takes place and releases 3MJ/ mole
  • The heat release will be utilized to melt the material as this enters into the gap between the two work pieces, and the base material will also start melting.
  • This is then solidified to produce a permanent joint.
  • A will act as a slag to protect the molten liquid metal from the atmospheric gases.



Mainly this technique is used in the repair works of rails in railways.


  • This process is used for welding of damaged wobblers and large broken crankshafts
  • To restore the broken teeth on gears


  • It is not possible for low melting points
  • High skill operators are required
  • Reduces the risks to operate
  • Low deposition rate
  • High level of fume

Atomic Hydrogen welding

  • It is a combination of electric arc and gas welding technique
  • Arc is generated between the two non-consumable tungsten electrodes
  • While applying the hydrogen gas to the arc region, due to arc temperature the hydrogen molecules are disassociated into individual hydrogen atoms.
  • These are unstable, as the hydrogen atoms slightly move away from the arc due to reduced temperature. They will recombine as hydrogen molecules
  • During the process due to exothermic reaction more heat is released.
  • This is used to melt the base material to produce a fusion joint
  • Hydrogen gas acts as heating element, as well as it acts as shielded gas to protect the molten liquid metal from the atmospheric gases.


  • These are used in welding of tool steels which contains tungsten nickel and molybdenum
  • Hard surfacing and repairing of dies and tools.


  • Faster welding process
  • Work piece material does not form the electric circuit.
  • Maintaining the arc column and striking the arc must be estimated
  • During the process at the joints intense flame is obtained
  • There is no requirement of the shielding gas or flux


  • Compare to the other process the cost of welding is high
  • Welding process is limited to flat positions only.

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