- 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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