Welding Transfer Modes: Spray, Global & Short Circuiting

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In MIG welding (GMAW), filler metal can be transferred from the electrode to the workpiece in two ways:

  1. Short-circuiting – This is when the electrode contacts the molten weld pool, thereby establishing a short circuit, which is known as short-circuiting transfer (short-circuiting arc welding);
  2. Drop transfer (Global or Spray transfer) – This is when discrete drops are moved across the arc gap under the influence of gravity or electromagnetic forces.

Shape, size, the direction of drops (axial or non-axial), and type of transfer are determined by a number of factors.

transfer modes mig welding

The factors having the most influence are:

  1. Magnitude and type of welding current
  2. Current density
  3. Electrode composition
  4. Electrode extension
  5. Shielding gas
  6. Power supply characteristics

Axially directed transfer refers to the movement of drops along a line that is a continuation of the longitudinal axis of the electrode.

Nonaxially directed transfer refers to movement in any other direction.

Short Circuiting Transfer

short circuit transfer mode

Short-circuiting transfer uses the lowest range of welding currents and electrode diameters associated with MIG welding.

This type of transfer produces a small, fast-freezing weld pool that is generally suited for the joining of thin sections, out-of-position welding, and filling of large root openings.

When weld heat input is extremely low, plate distortion is small. Metal is transferred from the electrode to the workpiece only during a period when the electrode is in contact with the weld pool. There is no metal transfer across the arc gap.

The electrode contacts the molten weld pool at a steady rate in a range of 20 to over 200 times each second. As the wire touches the weld metal, the current increases. It would continue to increase if an arc did not form.

The rate of current increase must be high enough to maintain a molten electrode tip until filler metal is transferred. It should not occur so fast that it causes spatter by the disintegration of the transferring drop of filler metal.

The rate of current increase is controlled by adjustment of the inductance in the power source. The value of inductance required depends on both the electrical resistance of the welding circuit and the temperature range of electrode melting.

The open-circuit voltage of the power source must be low enough so that an arc cannot continue under the existing welding conditions. A portion of the energy for arc maintenance is provided by the inductive storage of energy during the period of short-circuiting.

As metal transfer only occurs during short-circuiting, shielding gas has very little effect on this type of transfer. Spatter can occur, and it is usually caused either by gas evolution or electromagnetic forces on the molten tip of the electrode.

Pros of Short Circuiting Transfer

  • Low amperages
  • Works on thin materials
  • Can be used out of position

Cons of Short Circuiting Transfer

  • Can cause spatter
  • Can cause cold lap
  • Can cause undercut
  • Can’t short arc all materials

Globular Transfer

globular transfer mode

With a positive electrode (DCRP), the globular transfer takes place when the current density is relatively low, regardless of the type of shielding gas. However, carbon dioxide (CO2) shielding yields this type of transfer at all usable welding currents.

The globular transfer method is characterized by a drop size of greater diameter than that of the electrode.

Globular, axially directed transfer can be achieved in a substantially inert gas shield without spatter. The arc length must be long enough to ensure detachment of the drop before it contacts the molten metal. However, the resulting weld is likely to be unacceptable because of lack of fusion, insufficient penetration, and excessive reinforcement.

Carbon dioxide shielding always yields non-axially directed globular transfer. This is due to an electromagnetic repulsive force acting upon the bottom of the molten drops.

The flow of electric current through the electrode generates several forces that act on the molten tip.

The most important of these are pinch force and anode reaction force. The magnitude of the pinch force is a direct function of welding current and wire diameter and is usually responsible for drop detachment.

With CO2 shielding, the wire electrode is melted by the arc heat conducted through the molten drop. The electrode tip is not enveloped by the arc plasma. The molten drop grows until it detaches by short-circuiting or gravity.

Pros of Globular Transfer

  • Has a higher deposition rate
  • Larger wire

Cons of Globular Transfer

  • Can cause spatter
  • Can only be used in the flat or horizontal position

Spray Transfer

spray transfer mode

In a gas shield of at least 80 percent argon or helium, filler metal transfer changes from globular to spray type as welding current increases for a given size electrode. For all metals, the change takes place at a current value called the globular-to-spray transition current.

The spray-type transfer has a typical fine arc column and pointed wire tip associated with it. Molten filler metal transfers across the arc as fine droplets. The droplet diameter is equal to or less than the electrode diameter. The metal spray is axially directed.

fig10 47

The reduction in droplet size is also accompanied by an increase in the rate of droplet detachment, as illustrated in figure 10-47.

Metal transfer rate may range from less than 100 to several hundred droplets per second as the electrode feed rate increases from approximately 100 to 800 in./min (42 to 339 mm/s).

Pros of Spray Transfer

  • No spatter
  • Good wash
  • Good deposition rate
  • Good bead appearance

Cons of Spray Transfer

  • Has a very hot arc
  • Can only be used in the flat or horizontal position
  • Has limited penetration
  • Can not weld thin materials

Related Reads

Settings of MIG welding with chart

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About Jeff Grill

Jeff Grill hails from Long Island, a 118 mile stretch of land that starts just off the coast of Manhattan and stretches deep into the Atlantic ocean. He has always been interested in welding from an early age and has the cuts and bruises to prove it as he set out to work with a variety of metals.

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