Solid State Welding

1. Explosion Welding
Presented By:-
Deepam Goyal
Nitesh Parmar
Department of Mechanical Engineering
NITTTR , CHANDIGARH

2. Introduction
History
Terminology
Principle of Explosion Welding
 Salient Features of Explosion Welding
 Explosives Materials
 Advantages & Disadvantages
 Applications
 References
Contents

3. Introduction
 Explosion welding is a solid-state process
that produces a high velocity interaction of
dissimilar metals by a controlled detonation.
 This eliminates the
problems of heat effects
& micro-structural
changes (as in fusion
welding).
Fig. Explosive Welding
 Oxides found on material surfaces must be removed by
effacement or dispersion.
 Surface atoms of two joining metals must come into
intimate contact to achieve metallic bond.

4. History
 Arnold Holtzman and a team at DuPont in Delaware
put a lot of research into developing the process.
 Holtzman filed for a US patent in 1962 for explosion
welding, received the patent in 1964 and began
commercial production of bi-metallic explosion
welded clad in 1965.
 Detaclad licensed the process and was bought by
Dynamic Materials Corporation (DMC).
 Other companies have merged with DMC and
acquired the current name DMC Groupe SNPE
making them a worldwide company.

5. Component Terminology
 Base component
• Joined to cladder
• Remains stationary
• Supported by anvil
 Cladding metal
• Thin plate in direct contact with explosives
• Can be shielded by flyer plate

6.  Flyer plate
Contd..
• Sacrificial plate placed between explosive material and
cladder plate
• Used to protect cladder metal
 Interlayer
• Thin metal layer
• Enhances joining of cladder to base plate
 Anvil
• Surface of which the backer rests during explosion

7.  Anvil
• Surface of which the backer rests during explosion
 Standoff
• Distance between cladder and base plate before explosion
 Bond Window
• A range of variable in process such as velocity, dynamic
bend, and standoff distance that result in successful weld
 Bonding Operation
• Detonation of explosives that result in a weld
Contd..

8. Principle of Explosion
 Cladder metal can be placed parallel or inclined to the
base plate.
 Explosive material is distributed over top of cladder
metal.
 Upon detonation, cladder plate collides with base
plate to form weld.
 Waves are generated so due to mechanical bonding
joining takes place.
 A single detonation cap can be used to ignite the
explosive.

9. Placement of Cladder metal-parallel
 Standoff distance predetermined
and unique to material combination
• Achieved by placing shims
between plates
• Shims designed to be consumed
by explosion wave and do not
affect weld
 Usually ranges between 0.5-2 times
the thickness of cladder plate
 Cladder must reach critical velocity
before impact

10. Cladder placement-Angled
Where:
Vc = collision velocity
VD = detonation velocity
Vp = plate Collision velocity
α = preset angle
β = dynamic bend angle
γ = collision angle

11. Salient Features
 The high velocities are promoted by carefully detonated
explosives.
 The process can be done in vacuum to reduce sound &
blast.
 Typical impact pressure are millions of psi.
 Well suited to metals that are prone to brittle joints
when heat welded such as,
• Al on steel
• Ti on steel

12. Contd..  This process doesn’t work well for,
• Brittle metals with < 5% tensile elongation
• Charpy V-notch value < 10 ft.lb.
 Important factors are critical Velocity, stand off distance
& critical angle.
 If two materials can be brought close enough together,
they will bond at a molecular level.
 High velocity explosives require smaller gaps b/w plates,
and buffers such as rubber and Plexiglas are used.

13. Contd..
 Angled interfaces are only used for high velocity
explosives.
 The detonation velocity should not exceed 120% of the
sonic velocity in the metal.
 There is a maximum velocity for welding, above this the
thermal effects weaken the joint.
 To efficiently use explosives the plate separation is ½ to 1
times the cladding plate thickness.

14. Contd..
 Typical explosive forms
• Plastic flexible sheer
• Cord
• Pressed shapes
• Cast shapes
• Powder/granular
 Detonation velocity is a function of
• Explosive type
• Composition of explosive
• Thickness of explosive layer

15. Contd..
 Sonic velocity of cladding material can calculated using:
Where:
K = Adiabatic bulk modulus
ρ = Cladding material density
E = Young’s Modulus of cladding material
ע = Poisson’s ratio of cladding material

16. Contd..
Types of Bond:
 Straight, direct metal-to-metal : Best type of bonding but
difficult to obtain when collision velocity less than critical
velocity.
 Wavy : Interface is strong and the interface has waves.
 Straight, but with a continuous layer : Weaker bond that
results when the collision velocity is too high and the alloy
bonds are strong.

17. Assuring a Good weld
 Three types of Detonation wave welds:
• Shock wave develops if sonic velocity is greater than
120% of material sonic velocity (type 1)
• Detached shock wave results when detonation velocity
is between 100% and 120% of material sonic velocity
(type 2)
• No shock wave is produced if detonation velocity is less
than material sonic velocity (type 3)

18. Contd..
 Type 1
• Material behind shock wave is compressed to
peak pressure and density
• Creates significant plastic deformation locally
and results in considerable ‘shock hardening’
 Type 2 & 3
• Pressure is generated ahead of collision point
of metals
• When subject to large pressures, metal ahead
of collision point flows into spaces between
plates and takes form of high-velocity jet
• Effaces material and removes unwanted
oxides and other unwanted surface films
• No bulk diffusion and only localized melting

19. Explosive material
 High velocity (4572-7620 m/s)
• Trinitrotoluene (TNT)
• Cyclotrimethylenetrinitramine (RDX)
• Pentaerythritol Tetranitrate (PETN)
• Datasheet
• Primacord
 Mid-low velocity (1524-4572 m/s)
• Ammonium nitrate
• Ammonium perchlorate
• Amatol
• Nitroguonidine
• Dynamites
• Diluted PETN

20. Advantages of Explosion Welding
• Very large work pieces can be welded.
• (Al + Steel) materials can be welded.
• Can bond many dissimilar, normally unweldable metals.
• Material melting temperatures and coefficients of thermal
expansion differences do not affect the final product.
• Process is compact, portable, and easy to maintain.

21. Contd..
• Welding can be achieved quickly over large areas.
• No need for surface penetration.
• Backer plate has no size limits.
• Inexpensive.
• The strength of the weld joint is equal to or greater than the
strength of the weaker of two metals joined.
• No heat-affected zone (HAZ).

22. Disadvantages of Explosion Welding
• Metals must have high enough impact resistance and
ductility
• The geometries welded must be simple-flat, cylindrical,
conical
• The cladding plate can’t be too large
• Noise & blast can require worker protection, vacuum
chambers, buried in sand/water.

23. Applications
• Cladding of base metals with thinner alloys e.g. cladding of Ti
with mild steel.
• Seam and lap welds.
• Reinforcing aerospace materials with dissimilar metal ribs.
• Heat exchangers.
• Tubular transition joints.
• Used as a repair tool for repairing leaking tube-to-tube sheet
joints.
• Spot welding.
• Flat plates.
• Joining of pipes in socket joints.

24. Contd..
• Any metal with sufficient strength and ductility can be joined

25. Common industries that use Explosion Welding
• Petroleum Refining
• Chemical Processing
• Hydrometallurgy
• Aluminum Smelting
• Shipbuilding
• Electrochemical
• Oil & Gas
• Power Generation
• Cryogenic Processing
• Pulp & Paper
• Air conditioning & Chillers
• Metal Production

26. Examples

27. Examples
3” Diameter AI/SS Ring Copper/Stainless 12” UHV Assembly

28. REFERENCES
• Parmar, R.S. "Explosion Welding."Welding Processes
and Technology. Third ed. New Delhi: Khanna, 2012.
389-403. Print.
• Kalpakjian Seope, Schmid Steven R.: “Manufacturing
Engineering & Technology” Pearson Education India,
2009, pp 832.
• Sharma, P.C. A textbook of production Technology. 7.
New Delhi: S.Chand & Company Ltd, 2011, 373-374.
Print.
• Moeed, K.M., Manufacturing Science, Umesh
Publications, New Delhi, New Delhi, 2006.

29. Email ID:-
bkdeepamgoyal@gmail.com
er.nitesh41@gmail.com