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MODE OF METAL TRANSFER
IN WELDING
 History
 Introduction
 Forces that affect the metal transfer
 Classification of mode of metal transfer
 Parameter that affect the metal transfer
 Defects
 General points
 After Bronze Age and the Iron Age Sir
Humphry Davy in 1800 discovered Short
pulsed electric arc welding.
 Around 1900, all automatic arc welding
worked on alternating current (A.C)
discovered.
 The transfer of molten metal from the tip of
electrode to base metal.
 Arc welding and Consumable electrode
 Gravity Force
 Surface Tension force
 Electromagnetic Pinch Effect
 Drag Force
 Detaching Force - electrode pointed
downward
 Retaining Force – electrode pointed upward
Fg = mg
= ρV g
where,
ρ = density of
electron material
V= volume of molten droplet
g=acc. Due to gravity (~9.81)
 Retain droplet on the tip of electrode.
Fs = 2πγ r f(r/c)
γ = surface tension
r = radius of electrode
C =(2γ)/ (mgб)
f(r/c)=complex function varies
from 0.6-1.0
c =constant of capillarity of
electrode material
 Only detachment of the molten droplet
 Repelling force
2R4)Fp= 100 I2 × µ × (2R2 –r2) ÷ (8ᴨ
where,
I=current in conductor
µ=magnetic permeability
R=conductor radius
r=small diameter where pinching
happens
 Due to the flow of gas around the drop
 Detaching the droplet from tip of electrode
All forces acting in metal transfer process
A) With Electrode
1. Short Circuit
a. Dip Transfer
2. Globular
a. Repelled Transfer
3. Spray
a. Explosive Transfer
4. Slag Enveloped
B) With Rod
1. Short Circuit
a. Dip Transfer
2. Globular
a. Repelled Transfer
 Periodic bridging of gap between the
electrode and work piece.
 Heavy current flow occurs
 Decrease - surface tension, viscosity.
 Increase - electro motive, hydro dynamic
force.
 Short circuit mode of metal transfer.
 Electrode is fed into weld pool
 Fast pace
 Molten metal droplets is detached in globular
form.
 Action of gravity
 Arc length is medium to long
 Mode of globular transfer
 After detachment droplet not travelled into
weld pool
 Force -reverse plasma jet,
 Cause poor weld transfer and Excessive
spatters.
 High current density that tends to high temp.
 Increase pinch effect
 Depending upon the current density spray
mode have three stages:-
1. Projected transfer (high)
2. Streaming transfer (medium)
3. Rotary transfer (low)
 Droplet spattered (on the tip after
detachment)
 Formation of gas bubbles
 It is used in some application or according to
job.
 wet welding, under water welding etc
 Not used generally.
PULSED METAL ARC TRANSFER
 Weld power source
 Electrode polarity
 Shielding gas
 Emissive flow rate
 Welding Position
 In spray metal transfer mode
1. Large Heat Affected Zone(HAZ).
2. Creaks appearance.
 In short circuit metal transfer mode
1. More spatters.
2. Low speed.
3. Solid particle inclusion.
4. Sometime porosity.
 In globular metal transfer mode
1. Rough weld bead.
2. Blow holes
3. Pin holes.
 In slag enveloped mode of metal
transfer
1. Slag inclusion causes creaks
2. Porosity
3. Under cuts photomicrograph
 Spray metal transfer – costly , high current
and voltage, skill required.
 Generally used globular and pulsed short
circuit metal transfer in industry.
 According to efficiency:-
Spray
transfer
Short
circuit
Globular
slag
enveloped
Unit i(mode of metaltransfer)

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Unit i(mode of metaltransfer)

  • 1. MODE OF METAL TRANSFER IN WELDING
  • 2.  History  Introduction  Forces that affect the metal transfer  Classification of mode of metal transfer  Parameter that affect the metal transfer  Defects  General points
  • 3.  After Bronze Age and the Iron Age Sir Humphry Davy in 1800 discovered Short pulsed electric arc welding.  Around 1900, all automatic arc welding worked on alternating current (A.C) discovered.
  • 4.  The transfer of molten metal from the tip of electrode to base metal.  Arc welding and Consumable electrode
  • 5.  Gravity Force  Surface Tension force  Electromagnetic Pinch Effect  Drag Force
  • 6.  Detaching Force - electrode pointed downward  Retaining Force – electrode pointed upward
  • 7. Fg = mg = ρV g where, ρ = density of electron material V= volume of molten droplet g=acc. Due to gravity (~9.81)
  • 8.  Retain droplet on the tip of electrode.
  • 9. Fs = 2πγ r f(r/c) γ = surface tension r = radius of electrode C =(2γ)/ (mgб) f(r/c)=complex function varies from 0.6-1.0 c =constant of capillarity of electrode material
  • 10.  Only detachment of the molten droplet  Repelling force
  • 11.
  • 12. 2R4)Fp= 100 I2 × µ × (2R2 –r2) ÷ (8ᴨ where, I=current in conductor µ=magnetic permeability R=conductor radius r=small diameter where pinching happens
  • 13.  Due to the flow of gas around the drop  Detaching the droplet from tip of electrode
  • 14. All forces acting in metal transfer process
  • 15.
  • 16. A) With Electrode 1. Short Circuit a. Dip Transfer 2. Globular a. Repelled Transfer 3. Spray a. Explosive Transfer 4. Slag Enveloped B) With Rod 1. Short Circuit a. Dip Transfer 2. Globular a. Repelled Transfer
  • 17.  Periodic bridging of gap between the electrode and work piece.  Heavy current flow occurs  Decrease - surface tension, viscosity.  Increase - electro motive, hydro dynamic force.
  • 18.
  • 19.  Short circuit mode of metal transfer.  Electrode is fed into weld pool  Fast pace
  • 20.
  • 21.  Molten metal droplets is detached in globular form.  Action of gravity  Arc length is medium to long
  • 22.  Mode of globular transfer  After detachment droplet not travelled into weld pool  Force -reverse plasma jet,  Cause poor weld transfer and Excessive spatters.
  • 23.
  • 24.  High current density that tends to high temp.  Increase pinch effect  Depending upon the current density spray mode have three stages:- 1. Projected transfer (high) 2. Streaming transfer (medium) 3. Rotary transfer (low)
  • 25.  Droplet spattered (on the tip after detachment)  Formation of gas bubbles
  • 26.
  • 27.  It is used in some application or according to job.  wet welding, under water welding etc  Not used generally.
  • 28. PULSED METAL ARC TRANSFER
  • 29.
  • 30.
  • 31.
  • 32.  Weld power source  Electrode polarity  Shielding gas  Emissive flow rate  Welding Position
  • 33.  In spray metal transfer mode 1. Large Heat Affected Zone(HAZ). 2. Creaks appearance.
  • 34.  In short circuit metal transfer mode 1. More spatters. 2. Low speed. 3. Solid particle inclusion. 4. Sometime porosity.
  • 35.  In globular metal transfer mode 1. Rough weld bead. 2. Blow holes 3. Pin holes.
  • 36.  In slag enveloped mode of metal transfer 1. Slag inclusion causes creaks 2. Porosity 3. Under cuts photomicrograph
  • 37.
  • 38.  Spray metal transfer – costly , high current and voltage, skill required.  Generally used globular and pulsed short circuit metal transfer in industry.  According to efficiency:- Spray transfer Short circuit Globular slag enveloped