What is explosive welding process?
Explosive welding is the type of solid-state welding in which two dissimilar metals are welded together by using a higher impact force generated by the explosion of explosive materials.
It is the type of solid-state welding in which the material is not melted for the welding and also it does not use any filler material.
The process is also known as the explosive cladding process as it is used to apply the cladding material layer onto the base material. The explosive welding can be used for protecting corrosive material like carbon steel by covering it with a layer of non-corrosive material like stainless steel.
Explosive welding working principle:
In explosion welding, the flyer plate is arranged at a certain distance from the base plate for getting momentum to the flyer plate.
The flyer plate is accelerated by the use of explosives, therefore it hits the base plate at a higher velocity and due to this highest impact, the plastic deformation and molecular diffusion are happened in between two plates. And hence it can create the weld joint between the two dissimilar metals.
Explosive welding diagram:
Components of explosive welding setup:
The explosion welding setup consists of the following components,
1) Target plate/ Base metal: It is the plate on which the cladding has to be done. The target plate is mounted onto the anvil.
2) Flyer plate: The flyer plate is made up of cladding material and it has less thickness in comparison with the target plate.
The flyer plate may be parallel to the base plate or kept at a certain angle with the base plate.
3) Buffer plate: It protects the flyer plate from erosion due to the explosion.
4) Explosive material: The explosive material used for explosive welding is maybe RDX or TNT or any other explosives. The selection of explosive material is based on the magnitude of impact to be generated for welding.
5) Stand-off distance: The stand-off distance is the distance between the base plate and flyer plate kept for the movement of the flyer plate over the base plate.
6) Stand-off angle: In the case of material that can not weld by using constant stand-off distance, therefore for this material the flyer plate is kept at a certain angle over the base plate. This angle is known as a stand of angle.
Construction of exposing welding setup:
1) The target plate/base plate is fixed over the anvil to support it during the explosion.
2) The surface of the target plate and flyer plate are made clean from all impurities to avoid the generation of oxides.
3) After that the flyer plate is kept over the base plate by keeping stand-off distance and stand-off angle between these two plates. the standoff distance is about 0.5 to 1 times the thickness of the flyer plate.
4) The buffer plate is placed over the flyer plate to protect it from erosion.
5) After that the layer of explosive material is placed over the buffer plate with the detonator arranged at one end.
Explosive welding working:
The detonator helps to ignite the explosive material. The flame is initiated at one end of the flyer plate and propagate over the surface of the plate.
Due to the explosion, the flat plate moves at a higher velocity toward the base plate/ target plate.
This creates a high impact between the base plate and flyer plate.
Therefore the plates undergo plastic deformation and molecular diffusion which results in weld joint between two plates.
The strength of the weld joint depends on the impact generated by the explosive material.
Explosive welding advantages:
The advantages of explosive welding are as follows:-
1) It is easy to weld dissimilar metals which can not weld by using other methods.
2) The welding takes place in a solid state of materials.
3) In this process, the parent properties of the material are not affected.
4) It is useful for welding large surfaces.
5) it is useful in the cladding of a protective layer over a base metal.
6) For explosive welding, highly skilled labor is not required.
7) It requires minimum fixtures.
8) The process of explosive welding is simple.
Explosive welding disadvantages:
The disadvantages of explosive welding are as follows:-
1) It is used only for a ductile material.
2) Fire safety precautions are required due to the use of explosives.
3) It is used only for simple geometric shapes.
4) The method is not useful for brittle material.
5) Licence is necessary for using explosives.
6) The explosion creates a high level of noise and ground vibration.
7) This method is not suitable for thick flyer plates.
Explosive welding applications:
Following are some of the applications of explosive welding:-
1) Welding of large flat plates
2) Cladding of plates for prevention against corrosion.
3) To join pipes and tubes of dissimilar metals
4) Joining of cooling fins.