Mode of metal transfer in welding and the forc acting on the tip oe electode in welding ,also factoes w

1. MODE OF METAL
TRANSFER AND FORCE
ACTING ON IT
By-PAWAN KUMAR
PGWLF2150056
@PAWANKUMAR

3. Force acting on the droplets
1. Gravity( Fg )
2. Surface tension
3. Electromagnetic pinch force effect
4. Drag force
5. Kinetic forces
1. Gravity is a detaching force act on tip of electrode due
to gravity
Fg=mg
M=mass of the molten
droplet
g=gravity force

4. 4.drag frorce is due to the gas flow around the welding.

5. CLASSIFICATION OF MODES OF METAL
TRANSFER
basically there are four modes of
metal transfer
1. Short circuit
2. Globular
3. Spray
4. Slag enveloped

7. Dip Transfer:
This is also a short-circuit mode of metal transfer but in this case the electrode is fed into the
weld pool at a fast pace so that the wire dips into the pool before the droplet is detached. As in
the normal short-circuit transfer the current rises at the time of a short-circuit which results in
excessive heating and thus in breaking of the short-circuiting bridge with a transfer of metal
from the electrode to die weld pool. This type of transfer is associated with GMAW particularly
its CO2 variant
2. Globular Transfer:
*In globular mode of metal transfer the molten metal
droplet is detached from the electrode tip due to gravity
and other forces acting on it as in short-circuit transfer.
*The detached globule travels under the action of gravity
and hydrodynamic forces directly towards the weld pool
and is referred to as ‘drop transfer’.

8. 2.1Repelled Transfer
In globular mode of metal transfer if the droplet, after
detachment from the electrode does not travel
directly towards the weld pool and in fact is repelled
away from it under the action of certain forces, for
example, reverse plasma jet, then it is referred to as
repelled mode of transfer
* Thsi type of transfer of material is generally coming
in co2 and carbon welding

9. 3. Spray Transfer
• Spray mode of metal transfer is normally associated with high
current densities. The high current density leads to very high
temperature of the molten droplet with consequential lowering
of surface tension. As the current density is raised the droplet
growth rate increases proportionately to the increase in
temperature and electromagnetic forces in the form of pinch
effect become significant and outweigh surface tension.
• With high pinch forces the end of the electrode, is constricted
at all the times. Droplets are pinched off before they attain the
size permitted by the surface tension, and that results in what
is termed as spray mode of metal transfer.
• In the globular range of metal transfer the current is too
low to form the necessary jet and pinch forces for
detachment of the droplet

10. • Spray modes of metal transfer, described above, are
associated with GMAW with medium to long arc
lengths. There is no question of arc extinction at the
time of metal transfer in these modes of metal
transfer.
4. Slag-Protected Transfer:
• X-ray cinematography has revealed that the metal
transfer in submerged arc welding is similar to the one
observed with bare wire electrodes as in GMAW. The
droplet after detachment is either projected directly into
the weld pool or is flung sideways.

11. • In the latter case the droplet touches the wall of the flux
cavity that surrounds the arc and slides along it to the
weld poo, This results in slower rate of metal transfer. It is
known as ‘flux-wall guided transfer’ and, for the obvious
reasons, results in enhanced metal-slag reactions.
Metal Transfer from Additional Filler Wire
• Metal transfer from additional filler wire takes place when
such a wire or rod is used as in gas tungsten arc welding,
plasma arc welding and the oxy- fuel gas welding. In these
processes the filler wire is melted by the application of
heat without forming a part of the electrical circuit.

12. • The forces acting on the molten droplet are similar to those
in SMAW and GMAW however the electromagnetic pinch
effect does not play any part by being absent. The transfer,
therefore, cannot approach the spray mode. Most often
short-circuit (or bridging) mode of metal transfer is adopted
to make the maximum use of heat however, drop transfer
may also be used, if required. Globular or drop transfer, when
used, results in lower deposition efficiency due to delayed
detachment of the droplet from the filler wire

13. • Factor effect metal transfer
1. POWER SOURCES
2. ELECTRODE POLORATIY
3. SHIELDING GAS
4. EMISSIVE COATING
5. WELDING POSITION

14. Thanks