Flux-Core vs. MIG

From a performance standpoint, MIG welding offers a cleaner weld than flux-core, which means less grinding in the finishing stage and less chipping/brushing to remove flux before re-welding a joint.  But the added advantage of shielding gas comes with a cost both in terms of complexity and dollars.

The welders listed here come in three variants: flux-core only, MIG conversion capable, and MIG ready.  MIG-ready units come with the co-axial torch cable, regulator, and other materials necessary to hook up your gas bottle to the unit, while “conversion capable” units require an additionally-sold kit to convert to MIG use.

Most of the MIG units in our comparison are sold as “ready to weld” with flux-core wire.  To MIG weld, you’ll need to add solid-core wire (not a big deal as it’s even cheaper than flux-core) and a gas bottle (which is a big deal as it’ll likely cost $100-$200 to rent).  And while you might be able to get away by tying the bottle to the wall for a short time, eventually you’re going to want a cart to carry the welder and bottle to make things simple.  (Either way you’ll need to secure the bottle carefully, as the high pressure contained within — as much as 2000+ PSI — can turn that heavy bottle into a missle, as anyone who’s seen an episode of the A-Team can attest.)

An additional advantage to MIG welding is the ability to eventually swap in different wire and different gas combinations to allow you to weld materials other than mild steel, such as aluminum and stainless. 

Your choice here really comes down to how much you’d like to invest and what you intend to do with your welder.  If you’re going to be working with mild steel only and want to make the minimum possible investment, a flux-core unit will work fine for you.  They’re simpler to use, more compact, and some of the lowest-priced units.  If you think you might want to move on to MIG welding later, consider picking up a conversion-capable unit.  Or if you’re ready to jump in with both feet, go ahead and get a MIG-ready welder.

Key Manufacturer Specs

Welding Amperage/Duty Cycle 

The most basic component of a welder is its power supply.  You’ll note that the welders listed above all put out far more amperage than the 20A that they draw from the wall.  To accomplish this, the welder stores up power internally and provides it to the gun when you pull the trigger, sort of like a water tower stores up water from a slow source (like a lake) and provides faster flow during peak need.  Obviously the welder can’t put out a greater amperage than it takes in forever; it must ”take a break” every so often to recharge. 

Correction: As reader Cybergibbons commented below (and numerous others emailed to us), our analogy isn’t quite right here.  The welder doesn’t as much store energy to provide greater amperage as it does step down the line voltage.  Therefore, duty cycle (described in the next few paragraphs) is determined not by power storage capability, but rather by the thermal capabilities of the various power supply components.  Thanks for setting us straight!

Manufacturers provide two specifications to give you an idea of how capable the unit is at storing and delivering power: welding amperage and duty cycle. 

Duty cycle is a measurement of how many minutes out of ten you can weld with the unit before it must stop to recharge.  For example, if the unit could weld for two minutes out of every ten, it would be said to have a 20% duty cycle.  Clearly the duty cycle will change based on the amperage load, so any duty cycle measurement will be fixed at a particular amperage.  For example, you might see a duty cycle listed as 20% @ 90A.

Welding amperage indicates the range of amperage that the unit can provide under the most extreme conditions.  To put all this into perspective, consider a welder spec’d at 30-120A welding amperage with a 20% @ 90A duty cycle.  While you can weld at 120A (to handle thicker material), this particular welder will operate at a lower duty cycle than the listed 20% above 90A.  However, at 30A you’ll likely see a far greater usage percentage.

One way to tell a quality welder is by a longer duty cycle, but be sure to compare apples to apples.  A welder with a 20% @ 70A duty cycle doesn’t compare favorably to a welder with 20% @ 90A.  On some of the least expensive units you’ll often find duty cycle specificed at 60A or less, which isn’t enough to handle the thicknesses you’re most likely to see in basic steel fabrication.

Weld Thickness

Higher amperage allows you to place more heat into the metal, and therefore allows you to weld thicker material.  You’ll note in the comparison chart that weld thickness corresponds almost directly to amperage range, where units with the widest amp range can tackle the widest range of thicknesses. 

Watch out for spec sheets that show the ability to weld much thicker material than other welders with comparable amperage ranges; usually this means that they’ve included “multi-pass” welds in their spec.  (By making additional passes, it’s possible to weld material thicker than your welder can penetrate in a single pass.)  While this is useful information, you’ll want to make sure you’re comparing single-pass to single-pass or multi-pass to multi-pass.

Gun Length, Ground Length, and Power Cord Length

While not super critical, longer cables give you the ability to work farther away from the wall plug — a useful capability.  Many of the units listed here offer 8′ or 10′ gun cables, and you can easily find the length of the other cables in the product manuals.

Read the Product Manual 

An important note:  the product manual often provides much more information than you’ll find on the box or in an online product description.  When you’re shopping, the best way to get the real “scoop” is to download and read the product manual.  The manuals for virtually all the welders listed here are available from the manufacturers online and contain complete specs, parts lists, and lots of other details.

Read on for our recommendations.

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This entry was posted on Wednesday, June 14th, 2006 at 11:06 am and is filed under Features, Welding. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.