The explosive welding technique has found major use for cladding low cost plate (usually carbon steel) with more expensive corrosion resistant materials. This clad plate is typically used in the chemical and petrochemical industries as tube sheet for heat exchangers.
Explosive welding differs from other traditional joining processes as it does not depend on melting of two metals to be joined, or on plastic deformation of the surfaces in contact as occurs with cold or hot pressure welding. In simple terms an explosive weld is achieved by impelling the cladding plate against the substrate plate material using the considerable energy from an explosive discharge, resulting in a high energy rate impact. The high interfacial pressure at the point of contact (or collision front) between the cladding plate and the substrate plate must be greater than the yield strength of both materials, to permit plastic deformation within the surface layers to occur. A jet of highly softened metal is formed at the collision front and is projected in front of it as it progresses rapidly across the weld interface. As the jet progresses, it thoroughly cleans the surfaces, thus permitting solid phase bonding to occur between the two materials.
Because bonding occurs in the solid phase, it is possible to weld metals with different melting points and some of the common clad layers deposited onto steel plate are aluminium, copper, bronze, titanium, monel, nickel alloys and zirconium. Alternatively explosive welding can be used to repair or plug tubes in heat exchangers on-site, where conventional welding methods are difficult to use.
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