GMAW Metal Transfer Modes

Table of Contents > 1. What Is The Metal Transfer Mode In MIG Welding? 2. Four Primary MIG Welding Transfer Modes     2.1 Short Circuit MIG Transfer         2.1.1 Pros and Cons Of Short Circuit Transfer     2.2 Globular Transfer         2.2.1 Pros and Cons Of Globular Transfer     2.3 Spray MIG Transfer         2.3.1 Pros And Cons Of Spray Transfer     2.4 Pulsed-spray Metal Transfer         2.4.1 Pulsed MIG vs Other Metal Transfer Modes         2.4.2 Double Pulse (Pulse-on-pulse) Metal Transfer         2.4.3 Pros and Cons Of Pulsed MIG Metal Transfer: 3. Which MIG Metal Transfer Mode is The Best?     3.1 How Do I Know Which MIG Transfer Mode I am Using? 4. Conclusion 🧐GMAW Metal Transfer Modes FAQ

Gas Metal Arc Welding, or MIG Welding, is a versatile and widely used welding method, particularly favored by beginners and new welders. Its popularity extends to industries worldwide. 

At its core, MIG utilizes an automatically fed wire, which serves as both an electrode and a filler metal, offering a flexible and efficient welding solution. The arc is established once the circuit between the base metal and MIG wire is closed. The wire melts and is transferred across the arc into the welding joint, ergo the name metal transfer.

However, this process occurs in several ways, so we present the GMAW metal transfer modes to you today, including their basics, pros, and cons.

What Is The Metal Transfer Mode In MIG Welding?

MIG welding is a semi-automated process that joins two pieces using a constant-voltage power source, or MIG welder. A semi-automated process means the MIG wire is automatically fed into the joint.

The MIG welding wire simultaneously serves as an electrode, which is used to form an arc, and filler metal that fills the joint. The arc is established once the electrode closes the circuit with the base metal. The heat of the arc melts the base metal and filler wire. The metal wire is transferred across the arc and into the welding joint.

Molten metal wire transfers differently across the arc depending on the welding parameters, such as the amperage, voltage, shielding gas, and wire feed speed. As a result, there are several different metal transfer modes in MIG welding.

Four Primary MIG Welding Transfer Modes

There are four primary GMAW metal transfer modes:

• Short Circuit Transfer
• Globular Transfer
• Spray Transfer
• Pulsed Transfer

Source: https://www.aedmetals.com/news/mig-welding-transfer-methods

Each GMAW metal transfer mode has different characteristics, advantages, and drawbacks, so we'll pay more attention to each.

Short Circuit MIG Transfer

In short-circuit metal transfer, the MIG wire touches the base metal and short-circuits. This short circuit transfers the weld metal to the joint, roughly occurring 20 to 200 times in a second, and produces that "frying bacon" sound.

This low-energy metal transfer mode is commonly used among beginners and hobbyists. Low energy means lower current (wire feed speed) and voltage compared to other metal transfer modes, which has advantages and drawbacks. You can use the standard Ar/CO2 75%/25% (C25) gas mixture, but it also works with straight CO2.

The excellent part about the low current of short circuit transfer is the ability to work on thin metals without risk of burn-through or distortion. That's why short circuit is preferred when MIG welding metals up to 1/4 inch, with smaller diameter welding wires of 0.023, 0.030, or 0.035".

Additionally, short-circuit transfer creates a fast-freezing weld puddle, allowing you to weld in all positions. This is particularly beneficial when welding overhead or in a vertical position, where gravity can drag the molten puddle from the joint.

However, the short circuit also has its drawbacks. Low current and voltage means you cannot weld thicker pieces, and there is a risk of a weld defect known as cold lap. In addition, this method is slower than other metal transfer modes and can cause a spatter.

Pros and Cons Of Short Circuit Transfer

Pros: 

• Suitable for thin metals up to 1/4"
• Low amperage and voltage lower the risk of burn-through and distortion.
• Fast-freezing weld puddle is good for out-of-position welding
• It can be run with any popular MIG welding shielding gas mixture

Cons:

• Not suitable for thicker pieces
• Slower compared to other metal transfer modes
• Can create cold lap or undercutting issues 

 Source: https://www.semanticscholar.org/paper/Cold-lap-formation-in-Gas-Metal-Arc-Welding-of-%3A-An-Li/cc5967c673b25b789b6ba984dcb8c1f70f1b89ec

Globular Transfer

Globular MIG transfer occurs once you increase the wire feed speed and voltage of short-circuit transfer. The flow of electric current through the electrode generates a force on the wire tip. 

The higher current creates globs of molten metal wire, which are typically larger than the diameter of the wire, ergo the name globular transfer. These globs are directed into the welding joint, where they fuse the pieces.

Source: https://slideplayer.com/slide/15855044/

Although globular transfer can be achieved with an Ar/CO2 shielding gas mix, it is typically performed with 100% CO2. Higher current also means better productivity and welding speed but at the cost of weld appearance.

Globular transfer, paired with 100% CO2, produces significantly deeper penetration compared to a short circuit transfer, but the welds can get pretty messy, with a lot of spatter. Since globs are harder to control, the overall weld bead appearance is less appealing than other methods. 

In addition, higher amperage and larger globs make weld puddle fluid. Since molten metal can drip around and escape the weld joint, this transfer method is limited to horizontal and flat positions only.

Pros and Cons Of Globular Transfer

Pros:

• Higher amperage and voltage compared to short-circuit
• Works great with 100% CO2
• High deposition rate
• Produces deep penetration, which is suitable for thicker pieces

Source: https://www.youtube.com/watch?v=XkbgXQ7Wl-Y&t=14s

Cons:

• Produces lots of spatter
• Limited to horizontal and flat welding positions
• Less visual-appealing weld bead

Spray MIG Transfer

Once the amperage and voltage increase and the shielding gas changes to at least 80% argon, the globular transfer transitions to spray transfer. In spray transfer, as the name states, many tiny droplets with a diameter smaller than the welding wire are sprayed across the arc and into the welding joint.

When the current level is high enough, the electrode transfers to the work in tiny droplets that can form and detach at the rate of several hundred per second. If the arc voltage is high enough, these droplets are precisely directed into the weld joint rather than sprayed around the work, reducing the spatter to a minimum.

Generally, spray transfer looks like a needle spraying from the wire into the puddle, similar to a pressure washer hose. It also has a much smoother sound than a short circuit. Typically, spray transfer mode is used on material 1/8 inch and thicker carbon steel and aluminum.

Due to its high wire feed speed and deposition and low spatter, spray transfer is perfect for large-scale industrial applications. Companies can cut costs by improving the deposition and weld bead profile and reducing the time for post-weld cleaning.

However, spray transfer also has its drawbacks. First of all, it requires at least 80% Argon shielding gas, so it is only sometimes the most economical choice for hobby and DIY applications. Similar to globular transfer, high amperage creates a fluid weld pool, limiting spray metal transfer applications to horizontal and flat welding positions.

https://www.youtube.com/watch?v=hQiZ5c1SJe8&t=157s

Pros And Cons Of Spray Transfer

Pros:

• High wire feed speed and deposition rates
• Good weld bead appearance

 Source: https://www.youtube.com/watch?v=drCSLgfvY8I

• Less spatter compared to globular and short circuit transfers
• Great productivity for large-scale welding applications

Cons:

• Requires at least 80% argon shielding
• Very hot arc and fluid weld pool
• Limited to horizontal and flat welding positions
• Not suitable for thinner pieces

Pulsed-spray Metal Transfer

Technological improvements helped researchers incorporate the pulsed technique in MIG welding, representing a modified spray transfer. The original idea was to combine the advantages of all other transfer methods and reduce their drawbacks.

In pulsed MIG transfer, the current oscillates between the two values, base current, and background current, going back and forth at a rate known as frequency. When the current reaches the base amperage, it heats, melts the wire, pinches a single droplet from the electrode, and sprays it into the weld joint.

After that, the current goes to the background amps, which are high enough to maintain the arc but low enough so the wire transfer does not occur. During the background arc, the weld pool cools down, allowing welders to control the heat, which is crucial when welding thin or delicate metals. 

Limiting the heat input allows the welders to MIG weld delicate and thin metals without the risk of a burn-through or distortion. In addition, background amps cool down the puddle, allowing welders to use pulsed MIG transfer in all welding positions, including overhead and vertical up, without the risk of molten puddle escaping the joint or dripping onto the welder's head. This way of transfer also eliminates the spatter.

Pulsed MIG vs Other Metal Transfer Modes

Compared to other metal transfer modes, pulsed MIG transfer runs hotter than short circuits, so there is no risk of cold lap or incomplete fusion, but it still provides the ability to weld thin materials. Compared to globular, pulsed-spray transfer significantly cuts the spatter while still producing good depositions and high penetration. Finally, compared to spray transfer, pulsed transfer cools down the puddle, so you can use it in any welding position.

However, since the pulse is a variant of spray transfer, it also requires at least 80% Argon in a shielding gas mixture. Most welders prefer a 92%/8% mix of Argon and CO2, providing enough heat and arc control to pulse. 

Even though pulsed MIG welding has very few drawbacks, it is still a developing technology that requires a specialized MIG welder. 

Double Pulse (Pulse-on-pulse) Metal Transfer

If you think pulsed MIG transfer is fantastic, you should hear about double pulse or pulse-on-pulse MIG welding. This metal transfer mode combines the primary pulsing, which we explained above, with one additional pulse, which turns the primary pulsing on and off.

Adding one more pulse provides even better heat control, but what makes it unique is the ability to produce "dimes." In the past, stacked dimes were exclusive to TIG welding, and that's the appearance many welders strive for.

However, using the double pulse allows MIG welders to produce stacked dimes that look especially impressive on aluminum. Remember that this metal transfer mode requires highly specialized equipment that can be expensive and requires proper training.

Pros and Cons Of Pulsed MIG Metal Transfer:

Pros:

• Excellent heat control suitable for thick and thin pieces
• High deposition speeds boost productivity
• Little to no spatter during the process 
• Good weld bead appearance and weld aesthetics
• It can be used in any welding position

Cons: 

• Requires specialized equipment that can be expensive
• MIG welders without synergic pulse require lots of fine-tuning to get the best results
• It can be challenging for beginners and new welders to get the best out of this technology

Which MIG Metal Transfer Mode is The Best?

There is no simple answer to the question of which metal transfer mode is the best. As you can deduce from our article, each transfer has its ups and downs and requires a set of parameters to achieve and perform. So, there is no clear winner.

For example, short-circuit is an excellent option when MIG welding thin materials due to its low heat. If you don't have a pulsing option on your MIG welder, this is a go-to transfer method, even though there are risks from cold lap or undercutting.

Globular transfer mod is typically related to 100% CO2 mixtures, which welders use to get the job done quickly on carbon steel. Deep penetration is excellent for thicker metals, but this process sacrifices the weld appearance. Globs might create ugly welds with a lot of spatter.

Welders choose spray transfer in large-scale applications that require high deposition rates and speeds. Lots of small drops of molten metal are sprayed precisely into the weld joint, resulting in a good weld profile with little to no spatter. However, spray transfer is hot, and so is the weld pool it produces. So, it can burn through thin pieces and drip out in out-of-position welding.

Finally, pulsed-spray MIG transfer combines the best of all methods. It provides high speeds and high depositions but with limited heat input, which is excellent for delicate metals. Spatter levels are low, and appearance is great, but this is not a widespread technology, so it can be costly and take time to master.

How Do I Know Which MIG Transfer Mode I am Using?

From short circuit to spray and pulsed-spray transfer, things get hotter, penetration increases, and spatter lowers. However, there are no precise parameters (specific wire feed speed or voltage) that will tell you which metal transfer mode you are currently using.

You will have to observe the weld puddle and listen to the sound your weld is producing to determine what transfer mode you are currently using. However, you can easily aim for the desired results once you understand what makes one or other transfer methods.

Conclusion

MIG welding transfer modes explain how the molten wire is transferred into the welding joint. Transfer modes go progressively hotter, from short circuit and globular to spray and pulsed spray transfer and each has its ups and downs.

Understanding how each transfer impacts the wire deposition, penetration, spatter, and overall weld results is crucial to making informed results for your next MIG welding. Although things might initially sound complicated, you'll pick up things quickly.

 

1. What are the primary GMAW metal transfer modes?

There are four primary GMAW metal transfer modes: Short Circuit Transfer, Globular Transfer, Spray Transfer, and Pulsed Transfer.

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