Explosion welding (EXW) is a metal-working process that is sometimes also called explosive bonding or explosive cladding. Considered a solid state process, EXW allows two different types of metals to be forced together with a clean vacuum-tight weld. This is done without heating either type of metal to its melting point or jeopardizing the original properties of either. This is achieved when the velocity from controlled detonations is used to produce an atomic bond that is often impossible if other welding processes were used. Historically, this process has not been among the most widely used, but is often considered a specialty.
EXW is a welding process that was introduced in the latter half of the 20th century. The idea of explosion welding is said to be inspired by events in World War I. The process is believed to have arisen from observations about the manner in which shrapnel managed to weld itself to soldiers’ armor.
Explosion welding is considered a solid state process because two different metals can be joined without either reaching its melting point. One of the major benefits of EXW is that it can be used to weld almost any pair of metals and most alloys. This possibility is significant because many pairs of metals or alloys are considered incompatible if welding is attempted using other processes.
The weld from the EXW process is achieved by using the energy generated from controlled explosions. The force from those explosions causes the outer layers of each metal surface to take a plasma-like form that allows for coalescence. Although neither item reaches its melting point, the surfaces may appear molten, and some amount of heat is commonly generated. The heat is produced partly due to the impact from the collision of the two surfaces.
There are several notable benefits to explosion welding. First, the metals do not lose their original individual properties. Second, the joint that results from this explosive process tends to be exceptionally clean and vacuum tight. Third, the process is carried out very quickly and can be used on large surfaces.
In the decades following its introduction, explosion welding has generally been considered more of a specialized process. The use of this method is considered to be minimal when compared to its potential. This may be attributed in part to the fact that the process requires an extensive knowledge of explosives, which many metal workers do not have.