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Forge welding

Joining process where heat is generated by contact resistance between two rods burning away any impurities on the contact surface and welding the parts together.

Illustration of Forge welding

The process

Two bars [1] are connected to an external power source, with the result that the two workpieces act as electrodes. The ends are pressed together and transition resistance generated due to the current makes the temperature increase sharply at the contact point [2].

This increase in temperature leads to impurities in the contact point to burn away. The two rods are then separated and again combined to continue the combustion. This process is repeated until the material is free from contamination. In the end, the bars are melted together, the power is turned off and after the seam has been partially cooled it goes through a finished processing.

Finishing in the form of grinding can be applied in cases where a small weld is desired. Note that this is dependent on the thickness of the workpiece and thin material thicknesses can be difficult to grind.

Advantages and disadvantages
In comparison with alternative methods
Good welding quality
Intricate shapes can be welded
no filler is necessary
Only low carbon steel can be welded
High level of experience required of operators
Slow process
coke contamination possible