Explosive Welding

BY

S. PRANNOY

(06881A0329)

Explosive welding is a solid state welding process, which uses a controlled explosive detonation to force two metals together at high pressure. The resultant composite system is joined with a durable, metallurgical bond.

WHAT IS IT?

The fearsome destructive power of explosives can be harnessed to provide a unique joining method, known as Explosive Welding.

PROCESSThis is a solid state joining process.

When an explosive is detonated on the surface of a

metal, a high pressure pulse is generated.

This pulse propels the metal at a very high rate of

speed. If this piece of metal collides at an angle with

another piece of metal, welding may occur.

For welding to occur, a jetting action is required at the

collision interface. This jet is the product of the surfaces

of the two pieces of metals colliding.

This cleans the metals and allows to pure metallic surfaces

to join under extremely high pressure. The metals do not

commingle, they are atomically bonded.

Due to this fact, any metal may be welded to any metal

(i.e. - copper to steel; titanium to stainless).

COMMONLY USED EXPLOSIVEExplosive Detonation velocity , m/s

RDX (Cyclotrimethylene trinitramine) C6H6N6O6

8100

TNT (Trinitroluene, C7H5N3O6)

6600

Lead azide (N6Pb) 5010

Deta sheet 7020

Ammonium Nitrate (NH4NO3) 2655

HEAT EXCHANGER SERVICE Explosive welding provides tube plugging, tube

expansion, tube to tube sheet welding for heat exchanger users and manufacturers and debris removal from industrial plant by the use controlled explosive charges.

PROBLEM Over last 30 years heat exchangers have been subject to

increasingly stressful conditions operating under high temperature and pressures and consequently requiring tighter leak security such conditions have highlighted problems with fusion welding of tube to tube plate joints.

In high pressure applications tube joint leaks can be lead to the scrapping of the unit long before it estimated life span. Fusion welding determines the materials that can be used, materials, which are often not the most suitable for the operating conditions.

THE SOLUTIONExplosive welding produces a high velocity movement

from a controlled axial detonation. This ensures leak proof method of jointing which is able to with stand the high temperatures and greater working pressures of modern heat exchangers.

COMMONLY USED CLAD METALS

ADVANTAGES   Joining of pipes and tubes.

  Major areas of the use of this method are heat exchanger tube

sheets and pressure vessels.

  Remote joining in hazardous environments.

  Joining of dissimilar metals - Aluminum to steel, Titanium

alloys to Cr – Ni steel, Cu to stainless steel, Tungsten to Steel.

    Attaching cooling fins.

LIMITATIONSThe metals must have high enough impact

resistance, and ductility.

Noise and blast can require operator

protection, vacuum chambers, buried in

sand/water.

The geometries welded must be simple – flat,

cylindrical, conical.

CONCLUSIONThree-staging of formation of strong bonds between the

atoms of welded metals is established: activation of

contact surfaces; formation of physical contact; volume

impact and plastic deformation behind the contact point.

Thank Q