- 1 Overview of Flux Cored Arc Welding (FCAW) Process
- 2 Uses and Benefits of Flux Cored Welding
- 3 Buying Factors to Consider
- 4 Top 5 Flux Core Welders
- 5 Conclusion
Flux core welding has been around for more than 50 years. It is technically not a new process, but just a distinct electrode type that can work through a Metal Inert Gas (MIG) welding unit. This resulted in two categories of MIG units namely, flux core (only wire) and gas (solid wire). The gas units rely upon a distinct shielding gas as in the case of TIG, while flux core generates its own shielding gases upon the melting of wire.
Both MIG and flux cored arc welding are similar, as they use semi-automatic process and continuous wire feeds for ensuring a high production rate. However, the main difference is in the manner in which the electrode is protected from air. The flux core welding obtains its protection from flux core, which enables welding even in windy outdoors. MIG welding obtains protection from a gas bottle, which cannot survive well in windy situations or in outdoors.
As the name implies, flux cored welding features a hollow wire and a flux in the middle. It is the most productive manual welding and produces faster, high quality welds. When compared to MIG, a big difference exists in terms of weld per hour. While a MIG unit usually generates five to eight pounds of weld per hour, a flux core unit gives over 25 pounds.
In addition, the latter is capable of welding half-inch plates with in-depth penetration on sides, in just one pass. This is why flux core welding is chiefly the choice in the ship building industry. Typically, ships are composed of heavy plate for which too much welding has to be done.
Overview of Flux Cored Arc Welding (FCAW) Process
Just like MIG, flux cored welding needs three major essentials namely, a shield, filler metal, and electricity. It functions by supplying an electrode incessantly to the joint. Initially, the unit presses the trigger after which the wire feeder supplies the electrode, during which it is charged electrically.
When the electrode touches the metal joint, a short circuit occurs to heat up the electrode such that it starts melting. With the electrode, the metal at work also melts. In no time, both form a puddle, which melts the flux core simultaneously to form a shield from the air as well as a slag for preventing contamination.
With a flux core wire, one usually gets a bit dirtier weld than with a gas one. Moreover, it can be a bit tough to obtain quality results, at times.
Uses and Benefits of Flux Cored Welding
However, a flux-cored wire unit is optimized for getting results that a gas one cannot offer. For several applications such as flat, vertical-up, galvanized, and steel (hard to weld) welding, a flux-cored unit is preferred, as it does faster and better. Such a unit is also the choice of mild steel welding for its higher productivity.
Flux is better for shielding even in a dirty environment, which means it is preferable for field work. There is no need of tank or gas and that the unit is lighter as well as smaller enough to carry around. Moreover, the flux core unit burns hotter, which means it is ideal for thicker materials in one pass. Experts suggest FCAW on materials that are not thicker than 20-ga. With the right electrode, you can easily weld half-inch thick steel.
The biggest benefit of a flux cored unit is its cost lower than MIG welder. If cost is not a problem, you can consider buying a MIG welder that can deliver even flux core welding, an effective two-in-one deal.
Buying Factors to Consider
Just like other welders, there are some buying factors you need to consider while selecting a FCAW welding unit. Doing so certainly prevents you from being confused while coming across a variety of such units. Let’s explore these factors!!!
1. Types of Shielding
Flux-cored wires are available in two versions namely, shelf- and gas-shielded. Both have an external sheath and flux filling, of which flux is blended compound of alloys and deoxidizers for keeping pollutants away. In a self-shielding unit, an electrode itself as a tubular wire coated with a shielding powder lies in the middle. On the other hand, in a gas-shielded unit, the same electrode exists but with some other coating and a gas bottle is used, rendering a ‘Dual Shield’. Along the powder flux in the electrode’s middle, a shielding gas safeguards the weld area.
The flux wires in self-shielded units are highly portable and are ideal for ship building, structural steel welding, and bridge construction. On the other hand, gas-shielded wires are preferable for pressure vessels, heavy equipment designing, general fabrication, and petrochemical piping.
Both the wires are suitable for all-position or flat and horizontal welding on base stuff such as low-alloy steel, mild steel, stainless steel, exclusive alloy-based metals. You can even consider them for hard-surfacing fresh stuff to prevent them from abrasion as well as for rebuilding worn-out things.
2. Electrode Type
While the electrodes in use are same as for MIG welding, the difference is that the FCAW electrodes are tubular. Alternatively, they might have a hollow tube whose center holds the flux. On the other hand, MIG electrodes are robustly metallic.
A flux cored electrode is available in typical sizes, many of which are same as most MIG electrodes and others being similar to the stick electrode’s thickness. Some of the famous sizes for usual industrial applications are .035, .052, and 0.0625. Unlike hard-surfacing wires, these wires or electrodes for flux core welding have a classification as per American Welding Society (AWS), which is also important to consider apart from the size.
A common flux cored electrode is classified as E71T – 1, wherein E means electrode, 7 represents minimum tensile strength (70,000 lbs Per Square Inch (PSI) of weld), 1 signifies all-position welding ability (0 is for flat and horizontal), T means tubular, and 1 indicates usability and performance abilities.
In case of shielding gas, the classifications are noticeable as E70T-1C and E71T-1C/M. Herein, C represents usage only with 100% carbon dioxide shielding gas, while C/M allows even use of argon gas.
You should also consider the diameter of wire. The diameter of .030 inches is an all-around choice for a variety of metal thicknesses. Consider 0.35-inch diameter for welding thicker material at high heat. You should also look for the stick-out, length of intact electrode (not melted) elongating from the contact tube’s tip, excluding the arc length. Usually, flux-cored welding needs almost 3/4-in stick-out, which is twice of what is suggested for MIG welding.
3. Shielding Gas
For dual shielding units, the options of shielding gasses are limited. They are argon (AR), carbon dioxide (CO2), mix of carbon dioxide and argon, and a mix of argon and oxygen. The gas-shielded flux-cored models need pure carbon dioxide or a mix of argon and carbon dioxide. While the former ensures good penetration but with less stable arc and more scatter, the latter ensures better arc quality and lower scatter but with less penetration.
In case of carbon dioxide, the weld’s mechanical properties are not ideal, as flux in the wire unfavorably reacts to the gas. The arc is also not stable as expected. Even argon reacts with flux, which is not good. However, if used individually, both these gases deliver a good looking weld. Keep in mind that the look of weld is different than the quality of weld.
Of all the gases in use, the most common ones in use are a mix of argon and carbon dioxide or oxygen and argon. The famous combination is 75% argon and 25% carbon dioxide, which ensures a stable arc, metal’s more spray transfer, and less spatter. In case of oxygen and argon mix, oxygen in small amount ensures arc stability as well as improved mechanical properties.
It is always wise to look for manufacturer’s recommendations for gas and electrodes.
4. Power Supply/ Welding Polarity/Voltage Type
A MIG welding and a flux cored unit are same machines with a constant voltage supply. Such a power supply retains the voltage at the same level or nearby, at least. This is unlike a stick or TIG welding unit, which retains steady amperage.
In a flux cored unit, the amperage changes with the change in speed of the wire feed. The quicker the feed, the more is the electrode’s contact, which results in increased amperage as well as heat. A majority of good flux core-only units have restricted amperage range.
The type of voltage in use is Direct Current (DC), similar to the one that a battery generates. The polarity is normally DC electrode positive, which indicates that the welding handle is the circuit’s positive side or the flow of electricity is from metal to handle. Such an arrangement is normal in case of larger electrodes. While welding sheet metals and with smaller electrodes, polarity is switched to DC electrode negative.
Unlike those for MIG welder, the power supplies for flux arc welding come with more, power. In short, the latter units are tremendously powerful MIG units. A few flux core units can run with 1000+ amps!
Flux core-only machines are generally 110v only and generate less amperage (140amps) than a gas model or an alternator. A few of these models can even support gas shielding and tackle steel of 24-gauge to 1/4 inches thick. They can cover almost all user needs. Although you can utilize a flux core wire in a gas model, the vice-versa is not possible. A majority of gas units over 140 amps are capable of welding aluminum without wire breakage.
Most flux core units will be 110 or 220v, while a few can work with both. The reliable, entry-level 110v units up to 125amps are generally flux core-only machines. However, you can look for 110v/125amp gas models online, for welding steel with thickness of 18-gauge up to 3/16 inches. Those with 220v are 140amps and support any of the two wires.
You can even find higher powered units beginning from 180 amps and 220v. However, they are costly and feature either dual or self shield. Popular brands such as Lincoln, Hobart, and Miller offer such units, which even work on 110v. Just bear in mind that a dual voltage unit is costlier than its equivalent 220v unit but delivers more flexibility. They are approximately 210 amps.
5. Transfer Type
Two metal transfers are in use for welding with a flux electrode, which are Globular and Spray Transfer. Of the two, spray transfer is more popular and widely used one. As the name indicates, metal from the electrode is heated such that it squirts the metal filled, to the joint. On the other hand, globular heats the electrode such that metal globs drops from the electrode to the joint. The differences between the two transfers are also in terms of wire speed, voltage settings, and gas in use.
6. Push or Pull Welding
Consider a pull (drag) method for flux-cored welding, wherein the welding gun’s tip points back at the weld pool and pulls far from the finished weld. Just remember this rule: Drag if slag.
You need to consider two angles: Travel and Work. A travel angle is relative to the gun in a 90 degree position within the flat surface of the joint. Usually, this angle ranges from 5 to 15 degrees, but can go beyond 20 degrees in abnormal welding conditions, creating more spatter, instable arc, and less penetration.
On the other hand, work angle is the position of gun in context with the flat surface of the joint. Usually, it differs with each position of welding as well as joint configuration. This angle refers to the flat, horizontal, and vertical positions.
A flat position facilitates 90-degree, 180-degree, and lap joints. By holding the gun at 90 degrees and pointing the metal toward the joint with a normal travel angle, side-to-side small gun motion fills a big gap. Keeping the gun at 90 degrees gives you a fillet weld, which is also possible at 60 or 70 degrees for passing more heat into the metal’s bottom. The thicker the metal, the more is the angle. Keep these facts in mind and choose a unit that allows flexibility at the desired angles.
8. Duty Cycle
It is apparent that a higher voltage welder is more robust than a lower one, which is essential for generating more heat as well as welding thicker stuff. It is also essential for handling aluminum that demands more amperage than steel having identical thickness. Unlike a lower amperage (90amps) 110v unit, a 220v unit has a higher duty cycle for giving the result faster. This is why duty cycle is an important factor to consider. It indicates minutes within 10 minutes for which you weld before the unit needs to recharge.
For instance, if the duty cycle is stated as 30%, it means the welder can weld for three minutes at an interval of every 10 minutes. This cycle is dependent upon the load of amperage load, which means the measurement is stated at a specific amperage rating. For instance, the duty cycle is stated as 30% @ 90A.
The amperage rating is what the welder can emit in the most extreme condition. Let’s assume that the specification of a welder is 30-120A with 30% @ 90A duty cycle. This means that while it is possible to weld a thicker metal at 120A, the unit shall also run at 90A for three minutes incessantly.
It is recommended to compare the duty cycle of promising welders. However, do not compare a unit with 30% @ 70A with the one having 30% @ 90A. Remember to compare oranges to oranges and kiwis to kiwis. Most economical welders will have a duty cycle mentioned at 60A or less, but this is inadequate to tackle the thicknesses of steel for basic fabrication.
9. Overheating Protection
It is essential to look for a welder that can fight against overheating or else it soon becomes futile. While you can consider using a welder for a short time, overheating can make you wait for long until the unit cools. This is just not efficient. Thus, it is best to look for thermal overload protection.
Top 5 Flux Core Welders
This heavy-duty model is gasless welder with 50-120A output and duty cycle of 10% @ 105A and 35% @ 60A. It features flux cored wire of 0.030-inch in diameter for welding steel ranging from 0.023 to 0.035 inches as well as aluminium ranging from 0.030 to 0.035 inches. It is easy to set up, as there is no hassle of gas and comes with variable speed control, cooling fan, torch capabilities, and overload protection. Consider this durable unit for auto repairs, home tasks, and shop projects. It is best for mild steel. And yes, it is also more affordable than other popular units.
2. Forney 299:
This unit is ideal for a starter and is a gasless flux core unit to weld steel ranging from 24 gauge up to 1/4 inch at 20% @ 80A. Its plug-n-play mechanism is quite simple to use and accepts 2 to 10lb spools, making this unit quite versatile. The unit tackles .030″ wire, which can give good results on heavy metal. However, it is not for heavy duty fixes or tasks. You can expect welding for 1/4″ steel, but not with enough penetration. Nevertheless, the precision and adjustability are commendable and the digital readout is just user-friendly. The weld is smoother and that there is less splatter than older Hobart units.
This one is capable of welding aluminium with its gas shield welding technique. It is robust enough to weld mid steel of up to 3/8″ with gasless technique at 20% @ 90A. It is easy to use and explore through its plug-n-play mechanism and is very portable. You can consider it for repair tasks at home and shop. According to customers who have used it, this unit is ideal for the Do It Yourself (DIY) individual handling steel having thickness of 10-gauge (1/8-inches) or thinner.
This 70A unit comes with dual capabilities, Flux-cored and MIG, and plugs into 20amp outlet of 115v in homes. It can even work with gas shield technique although that is sold separately. The unit is capable of welding up to 1/8-inch mild steel at 20% @ 70A. It is lightweight and compact enough to go anywhere with you and is easy to use. The welder features continuous wire feed speed setting, variable voltage settings, and accessories such as gas nozzle, work cable, solid wire spool, hose, lens, and self-shielded spool of wire. It might sound a bit costly, but it is exactly what you get for what you pay.
This one is perhaps the most economical single phase welder in this list. It is an ideal for starters as well as mid users. With a current of 50-120A and duty cycles of 35% at 60A and 10% at 105A, it is capable of welding steel with thickness ranging from 0.023 to 0.035 inches. The unit comes with wire brush, good spool of flux wire, additional fuses, additional electrodes, torch, and weld mask. However, there is no manual or instructions, although e-mailing can get you one as quickly as possible.
The fact is that flux core welder is a typical MIG unit with almost the same equipment but with some differences. While many consider them to be different welding processes, the difference only lies in the kind of electrode and type of shielding. So, using a flux core unit is just using a different electrode in a MIG welder. You just need to use the right flux core electrode for your job that needs to happen faster than a typical MIG unit.