Explosive Welding – Principle , Working, Application

Explosive Welding:

It is a solid state welding process wherein welds are produced by the high velocity impact of the workpiece as a result of the controlled detonation. The explosion accelerates the metal to a speed at which the metallic bond gets formed between them, when they collide against each other. The weld is produced within a fraction of a second, without the addition of a filler metal.

Principles:

There are typically three components in explosion welding: Base Metal, Prime or cladding metal and explosives. The material at base is kept stationary as the prime component is welded to it.

The base component may be supported by a backer or an anvil, particularly when it is relatively thin. The base unit involving backer should be sufficiently rigid in order to minimize the distortions during the welding operation.
The prime component is usually positioned parallel to the base component or at an angle, in special applications. A stand-off distance is kept in case of parallel arrangements. The explosion locally bends and accelerates the prime component across the stand-off distance at a high velocity so that it collides at an angle and welds to the base component. This angular collision and welding front progresses across the joint as the explosion takes place.

The explosive, almost always in granular form, is distributed uniformly over the top surface of the prime component. The force which the explosion exerts on the prime component depends upon the detonation characteristic of the explosive used.

Explosive Welding Diagram  (EXW):

explosive welding diagram
explosive welding diagram

Explosive Welding  Working (EXW):

Explosive welding is used primarily for bonding sheets of corrosion- resistant metal to heavier plates of base metal (a cladding operation), particularly when large area are involved. The principles of explosive welding have been schematically illustrated in Fig . The bottom sheet or plate is positioned on a rigid base or anvil and the top sheet is inclined to it with a small open angle between the surfaces to be joined. An explosive material, usually in the form of a sheet, is placed on top of the two layers of metals and detonated in a progressive fashion, beginning from the mating surfaces. Compressive stress waves, of the order of thousands of
Mega Pascal’s, sweep across the surface of the plates. Surface films are liquefied or scared off the metals and are jetted out of the interface. The clean metal surfaces are then thrust together under high contact pressure. The result is a low temperature weld with an interface configuration consisting of a series of interlocking ripples. The bond strength is quite high and explosive clad plates can be subjected to a wide variety of subsequent processing, including further reduction in
thickness by rolling. In this solid state welding process, numerous combinations of dissimilar metals can be joined.

Application:

  1. Used to weld large structure sheets of aluminum to stainless steel.
  2. It is used to weld cylindrical component like pipe, concentric cylinder, tube etc.
  3. Weld clad sheet with steel in a heat exchanger.
  4. Join dissimilar metals which cannot be weld by other welding process.
  5. For joining cooling fan etc.
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