What is Pulse MIG welding?

What is Pulse MIG Welding?

Pulse MIG offers fast, high quality, low spatter and consistently great looking welds, with better thermal control vs. conventional MIG welders.

Pulse MIG is best known as a great process for welding aluminium, however it is also an excellent process for welding with stainless-steel and bronze wires. In many cases, Pulse MIG can achieve results that are comparable to TIG welding, but with speed and productivity that is superior to TIG.

In technical terms, Pulse MIG is a highly-controlled spray-transfer MIG process. Unlike the traditional 'short-circuit' MIG process, the filler metal is transferred from the wire to the weld pool, without the wire contacting the weld pool. The current alternates, or pulses, between a high peak current and a low background current at a frequency of up to several hundred times per second. With each pulse, the peak current pinches off a droplet of wire and propels it to the weld joint, while the background current maintains the arc at a low enough power level so that short-circuit can’t occur.

Pulse MIG welding Aluminium

Aluminium is a high thermal conductor (which means that heat is quickly transferred away from the weld pool), with a relatively low melting temperature. Pulse MIG process allows the operator much greater thermal control to apply enough heat for a successful weld, whilst avoiding distortion or burn-through.

Pulse MIG welding with Bronze wires (MIG brazing)

Bronze wires are typically applied at a temperate that is lower than the melting point of the parent material - where the materials are essentially "stuck" rather than welded together - and are commonly used on thin materials (eg car body panels) where low temperature welding is essential to avoid distortion. Also commonly used on galvanised or zinc-coated steels (up to 2mm thickness) because the weld metal does not rust and the lower application temperature prevents disturbance (evaporation) of the zinc coating.  The ability to control and reduce heat makes pulse an ideal process for brazing wires.

Pulse MIG welding with Stainless-Steel

Because stainless-steel is a poor thermal conductor, heat is typically 'trapped' close to the weld zone. This can result in expansion/distortion and rust contamination due to concentrated carbon in the weld zone. The weld pool is comparatively sluggish with poor wetting/flow into parent metal. The pulse process allows stainless wires to be applied at lower temperatures to minimise distortion and imperfections. Pulse MIG is especially beneficial for welding thin stainless material where it is often extremely difficult, if not impossible, to avoid warpage/distortion with conventional MIG process.

Pulse Frequency/Pulse Hertz

The pulse frequency or pulse hertz are the same thing: the number of pulses per second. For example, the UNIMIG AC/DC machines have a pulse frequency range of 0.5-200Hz per second. That means that 1Hz equals one pulse per second, and 50Hz is 50 pulses per second.

One pulse per second is relatively slow and easy to follow with your eyes. 30 pulses or more is pretty fast, and it’s hard to see the individual pulses. Anything between the 5-30 pulse range is painful on the eyes. It’s kind of like staring at a strobe light, which is super unpleasant to look at and really hard to concentrate on timing a weld with.

When it comes to picking how many pulses a second you want, it really depends on the application. If you’re welding thin material, then a fast pulse is usually better, and it will leave a high profile bead. If you’re welding thick material, then a slow pulse is usually better, and it will leave a low profile bead.

Pulse Percentage (%)

The pulse percentage is the amount of time spent in the peak and base amps for each pulse. If you set the percentage to 50%, that means 50% of the pulse cycle will be the peak amps, and 50% of the pulse will be the base amps.

You can adjust this either way, where 90% is almost entirely peak amps and 20% is almost no peak amps. The more time spent on the peak amps part of the pulse, the more penetration you’re going to get and vice versa.

MIG Pulse

There are two kinds of pulse MIG welding:

Single Pulse – Single pulse MIG is a type of spray transfer that, like TIG, alternates between the peak current and the background current.

MIG pulsing is generally spatter free because the wire never actually touches the weld.  Droplets of metal are ‘sprayed’ into the weld on the peak part of the cycle.

The background current of the pulse cycle isn’t hot enough to transfer metal. It simply maintains the arc. It produces all the benefits of spray transfer (speed, no spatter, deep penetration) without all the excess heat.

Single pulse MIG welding sounds similar to an AC TIG weld, with a constant high pitched buzzing.

Double Pulse – Double pulse is two pulses that happen simultaneously.

The first pulse is your standard (see: single) pulse with a peak amp and a base amp.

The second pulse, which doesn’t transfer any wire, turns the first pulse on and off in its cycle. During this second pulse, the arc remains on, but the temperature is so low there is no welding happening.

When the second pulse is ‘on’, the first pulse takes over (turning on) and alternates between the peak amps and base amps, creating the weld the same way a single pulse does. When the second pulse is ‘off’, nothing is happening.

The ‘off’ part of the second pulse can be adjusted to be hotter or colder, but its purpose is to give the base material a moment to cool. In order to make the most out of a double pulse, leaving the base of this cycle low is recommended.

Top Gun 2000-3500

·       Press and hold RETURN button for 6 seconds to reset to default settings.

·      Press and hold function buttons to save and recall settings, up to 18 saveable settings.

·       Press and hold centre adjustment knob to turn on spool gun mode.

·      Dual pulse default settings are the recommended settings to use, only fine tuning recommended.

·      Start by setting the machine on Auto mode, then adjust in MIG mode.

·      Adjust BASE and PEAK feeding speeds to increase materials thickness.