1. Special Welding Processes

2. 1.) Submerged Arc

4. arc buried in granular flux
single pass butt welds up to 3” thick
electrodes up to 1/2” in diameter

5. multiple electrodes

6. automated carriage that follows track

7. manual

8. hopper feeds granular flux to joint just ahead of the arc
usually done in flat position
flux remaining over the completed weld acts as a heat insulator
unused slag can be reused
fast, no visible arc, no spatter, high quality welds, thick materials

9. 2.) Electroslag

10. developed to weld very thick sections or joints

11. eliminates the need for multiple passes or grooves

12. Vertical joint - arc started between electrode & bottom

13. flux is added - forms a layer of molten slag - arc not needed
resistance to current flow thru the flux creates heat necessary to melt electrode and base metal

14. water cooled copper shoes contain molten metal in joint

15. adv: fast, no edge prep, thick plates can be welded

16. 3.) Electrogas - use shielding gas - flux cored wire fed in joint
arc maintained between electrode and weld

17. 4.) Narrow Gap
less weld metal is required
used on thick sections

18. similar to electrogas except weld joint has a narrow gap

19. Electrode guide tube used to feed electrode to joint bottom
problem - getting the electrode to touch both sides of the joint
cure - bend electrode into wave form

21. 5.) Stud
no drilling or punching holes in structure

23. stud placed in chuck on gun
ceramic ferrule placed on end of stud
contains molten metal

24. pull trigger stud pulled away from work
arc formed between stud and work

25. Stud forced into molten metal and cools

26. ferrule is broken off

27. Aluminum can be welded using shielding gas

28. 6.) Plasma arc welding
plasma means ionizing gas (a gas which has lost or gained electrons)
orifice gas becomes plasma as it passes through the arc toward the work piece

29. Tungsten electrode surrounded by inert orifice gas
helium argon nitrogen

30. Separate shielding gas protects the welding or cutting process

31. square butt joint normally used

32. Transferred vs. Non Transferred Arc

33. fill metal is also added automatically

34. adv: concentrated current flow
arc stability with large changes in arc length
low heat input
high speed (30 ipm)
best results when operated automatically

35. disadv: noisy

36. 7.) Underwater SMAW
use well insulated electrode holder and special water proof covered electrodes
because of rapid cooling - use stringer beads not weaving
short arc length and DCEN
poor visibility - use #4 or #8 lens
communication system - person above starts and stops the current for the system
normally have 80% of the tensile strength and 50 of the ductility of normal welds

38. Solid state welding processes
do not use an arc
do not have a beam of energy
do not use a flame
do not use resistance to heat the metal
processes are done when the metal is cold, warm, or hot but temp does not exceed the melting point
no filler metal added

39. 1.) Cold welding
theory - pressure at the surface causes fusion only a few molecules deep
this fusion is sufficient to hold the material together and provide good strength
works best on soft ductile metals

40. Cold Welding (Cont.) no heat needed
enough pressure must be applied to reduce original thickness of metal by 1/4 of original thickness
oxides and contaminants must be completely removed

41. Tool can be hand, pneumatic, or hydraulic
dies must be designed to impose proper pressure for different metals

42. 2.) Explosion welding
metals placed at angle to each other
protective material is placed over the metal and the explosive material is placed around the metal
explosion forces the plates together at high velocity causing surface ripples in metal
ripples lock or weld the two metals together

44. 3.) Friction welding

45. pieces to be welded are mounted in a chuck
one piece stationary - one revolves
brought together under pressure -heating occurs
parts forced together under pressure - allowed to cool
weld is produced in about 15 seconds
process is similar to upset or flash welding - but friction is used to generate the heat

46. Adv.
well suited for joining dissimilar metals to mild steel in production
no protective atmosphere is required - saves time and materials

47. 4.) Ultrasonic Welding
welding equip contains transducer which convert high freq. Elect power into mechanical vibration at the same freq. (10 K to 75 K hertz)
metal clamped together under pressure and high frequency

48. UT Welding (Cont.)
vibrations are introduced into metals through a welding tip
vibrations break up surface films causing metals to bond
max thickness is .100" on al. and .040" on harder materials

49. UT spot welds

50. UT seam welds with lateral drive rollers

51. adv:
fast
happens without heat or melting - no heat distortion
cleaning is not necessary
low clamping pressure which reduces deformation
no fluxes
no filler metals

52. UT Adv (Cont.) thin sections can be welded to thick sections
pressures less and welding times shorter than used in resistance welding
many types of metals can be joined to themselves or other metals
minimal training - semiskilled personnel

53. High Density Welding Processes
involves concentrating a lot of energy on a small spot
produces deep narrow welds
two processes include:
Electron beam
Laser beam

54. 1.) Electron beam welding:
uses a concentrated beam of high velocity electrons to melt welded metal
current passed through a tungsten filament which emits electrons
parts are placed very close together - almost touching
edges must be very straight
part being welded is placed on a carriage that moves under the beam

55. Electron Beam Welding (Cont.)
can make complete penetration weld in 10 inch steel plate
fast - .25" plate welded at 200 ipm

56. usually done in vacuum chamber
no particles in air to interfere with beam
more vacuum, the narrower the beam is
can be done without a vacuum but the parts must be close to the beam source

59. 2.) Laser beam welding
Light Amplification by Stimulated Emission of Radiation
laser beam is just light
light beam has one wavelength
has one phase - [all the particles (waves) move together]
laser beam produced by CO2 for welding

60. Laser Beam Welding (Cont.)
beam is focused and aimed using lenses and mirrors
lasers are operated at atmospheric pressure
shielding gas is used to protect the metal from oxidation
parts to be welded must be close together with straight edges
travel speeds are fast