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Go W el d i n g .Or g Flux Cored Arc Welding!

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FCAW Welding

Flux core arc welding was introduced in the 1950s. Technically theintroduction of this process was not new. It was just a new type of anelectrode that can be used on a MIG welding machine. Flux cored arcwelding is a process similar to MIG welding. Both processes usingcontinues wire feeds, and similar equipment. The power supply for aFCAW, and a MIG welder, are the same machine. They are bothconsidered semi automatic processes, and have a very high productionrate.

The main difference between flux cored arc welding and MIG welding isthe way the electrode is shielded from the air. Flux cored arc welding justlike the name implies, has a hollow wire with flux in the center, similar tothe candy called pixy sticks. Just as the name states, a Flux Core. The

main difference be tween MIG welding and flux core arc welding is, FCAWgets its shielding from the flux core, and this allows the operator to weldoutdoors where it is windy. Its like a SMAW welding electrode turnedinside out! MIG welding gets its shielding from a bottle of gas which hasserious draw backs, when welding outdoors, or in drafty conditions.

Flux Cored Arc Welding Produ ction

Flux cored arc welding is the most productive of the manual weldingprocesses! When comparing MIG welding to flux core arc welding, there is ahuge gap in production, in the amount of weld per hour. A MIG welder cantypically produce 5 to 8 pounds of weld per hour, verses a FCA welderpacking 25 plus pounds of weld per hour. On top of that flux core welding canweld 1/2" plates in a single pass with full penetration on both sides. Flux corearc welding for this reason is primarily used in the ship building industry. Shipsare made of heavy plate, and have endless amounts of welding that needs tobe done. Flux core welding produces high quality welds, fast, and even whenin windy conditions.

Weld ability o f Metals

Welding with flux core electrodes has some serious cons when it comes to the weld ability of metals. So far, FCAW hasbeen perfected on most carbon steels, cast iron, nickel based alloys, and some stainless steels. Unfortunately mostnon ferrous exotic metals cannot be welded and that includes aluminum. On the upside for most hobbyists the flux coreelectrode may be an excellent choice for general garage work, because if used in a MIG welder there is no shieldinggas required on some electrodes.

How Flux Cored Arc Welding Works

Flux cored arc welding just like MIG welding requires three main ingredients, electricity, filler metal, and a form ofshielding from the air. Just like MIG welding, flux core welding works by feeding an electrode continuously to the joint.First the welder squeezes the trigger, and then the wire feeder begins to feed the electrode to the joint, at the sametime the electrode gets electrically charged. Once the electrode hits the metal joint, the electricity short circuits, andheats up the electrode till the electrode begins to melt. Once the electrode begins to melt, the metal also starts tomelt, and then both of them start to create a puddle. This puddle at the same time melts the flux core, creating ashield from air, and at the same time produces a slag that protects the weld from contamination.

FCAW Self-Shielding v s. Dual Shield

Flux cored arc welding comes in two types of shielding. The first difference is in the electrode itself, it is a tubular wirewith a shielding powder in the center. In technical terms this is called Self-Shielding or sometimes branded "InnerShield". The second is the same type of electrode, but another ingredient is added. A bottle of gas is used in additionto the flux core shielding. The technical term for this is Dual Shield. In the case of dual shielding, you have a powderflux in the center of the electrode and an external shielding gas protecting the weld area.

FCAW Voltage Type - Welding Polarity Power Supply

A flux cored welding power supply is also a MIG welding power supply, they are the same machine. That is a ConstantVoltage Power Supply. Constant voltage power supplies keep the voltage near, or at the same level. Unlike a TIG, orStick welder, that keeps the amperage consistent. In the flux cored welder the amperage is changed with the wire feedspeed. The faster the wire feeds, the more contact the electrode has, producing more amperage, and heat.

The voltage type used is D/C direct current like the type current produced by a battery. The polarity used in industrialflux core arc welding is typically D/C electrode (+) positive. This means that the handle is the positive side of the circuit,or the electricity flows from the metal to the welding handle. This is typical when larger electrodes are used. Whenwelding with smaller electrodes and sheet metals, the polarity is changed to D/C electrode (-) negative.

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The main difference between FCAW, and a MIG welders are, flux cored arc welding power supplies are available with,much, more, power! Basically they are an extremely powerful MIG welder! Some flux core arc welders come with thecapabilities of running over an extremely hot, 1000 plus amps! That is where they leave MIG welding in the dust forproduction.

Shielding Gasses for FCAW

In the case of dual shielding being used with a flux cored electrode thechoices of shielding gasses are limited. The choices are as follows:

CO2 Carbon dioxide

Ar Argon

CO2 / Ar A mixture of the two

Ar / Ox A mixt ure of the two

CO2 by itself produces the deepest penetrating weld but has some draw backs. The mechanical properties of the weldare not the best due to fact the flux in the wire reacts with the shielding gas. Others draw backs are, it produces a lot ofspatter, and the arc is stiff and not as stable as it can be.

Argon by itself will also weld with a flux cored electrode, but just like CO2, it reacts not favorable with the flux. BothArgon and Carbon dioxide can make a decent looking weld if used by themselves. What the weld looks like verses theactually quality of the weld are two different stories.

The most common gasses used for dual shield FCAW are a mixture of Carbon Dioxide and Argon or Argon andOxygen. The most popular is C25 / 25% Carbon Dioxide and 75% Argon. This gas produces a stable arc, less spatter,and allows more of a spray transfer of metal. I recently used this mixture when taking my 3G flux cored arc welding

certification. In some other cases a mixture of Argon and Oxygen may be used. Oxygen in small percentages stabilizesthe weld arc and improves the mechanical properties of the weld.

Ultimately if using dual shield its always best to read the electrodes manufactures recommendations or ask yougas supplier for the proper g as.

FCAW Electrode Types

The electrodes used for flux cored welding are almost visually the same as a MIG welding electrode. The difference isthat flux cored electrodes are tubular, or a hollow tube with flux in the center. MIG welding electrodes are solid metal.

Flux cored electrodes come in standard sizes. Some are the same size as most MIG welding electrodes but others arecomparable to the thickness of a stick welding electrode. Here are some of the more popular sizes for standardindustrial applications:

.035

.045

.052

1/16

As with most electrodes there is a standard classification code or designation code, on the spool they come on. Tounderstand the classifications better it is important to know some basics about where the classification codes aredifferent.

A somewhat common flux cored welding electrode is the E71T 1. As with all electrodes the numbers and letters allmean something. There identifications are as follows.

E Stands for electrode.

7 Stands for the minimum amount of tensile strength. In this case it is 70,000

lbs of tensile strength per square inch of weld. The way this number is figured is

by adding four zeros to the number.

1 Stands for the position that this electrode can be welded in. There are onlytwo designations and they are 0 for flat and horizontal welding, then there is

1 for all position welding.

T Stands for a tubular electrode. When T is used it is always assumed it is

a flux cored electrode.

1 The last is the shielding flux type designations.

As a note with all flux cored electrodes they need to be stored in a dry place. Otherwise the may pick up moisture andthis will cause major weld defects.

Flux Cored Welding Transfer Types

When welding with a flux cored electrode there are two metal transfer types used! The transfer types are SprayTransfer and Globular. Spray transfer is the most commonly used. Just like the name states the metal from theelectrode gets heated up to the point that it literally sprays the filler metal to the joint. Globular transfer heats up the

electrode hot enough for globs of metal to drip off of the electrode to the weld joint. What separates the two transfertypes are, voltage settings, wire speed, and the gasses used, if any.

Flux Cored Arc Welding Jo int preparation

Joint preparation for flux core is not as critical as with MIG welding. FCAW can typically burn through mill scale andminor rust. In many cases when the metal is cut with a torch, it can be welded as-is, with no additional cleaning. For theship building industry this is a huge savings in labor cost. In addition to easy joint preparation, beveled grove joints canbe narrower for metals inch or thinner, and they can be welded in a single pass with full penetration on both sides.

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Ceramic Backing Tape

Commonly in the ship building industrymany joints are welded from a single side using a ceramic backing tape. Theceramic backing tape is like a mold to pour metal in, but in this case the electrode will fill that mold. When ceramicbacking tape is used it allows for full joint preparation and outstanding weld quality. This in return gives full control ofthe shape and penetration of the back side of the weld. Once the weld is finished, the ceramic tape is simply peeledoff, and thrown away. The great think about using ceramic backing tape is that it is just like welding an open root buttjoint, but requires much less skill! The pictures below are of the first t ime I used ceramic backing tape on a 3G weldjoint. Its real easy as long as you keep the arc in the puddle!

FCAW Machine Set-Up

When setting up a for flux cored arc welding machine there isno simple answer! The basics of flux cored machine set-upare the same as MIG welding. On some welding machines likethe Millermatic 250, there is a welding machine setting charton the inside panel. The picture on the left is the inside panelof the Millermatic 250, showing the recommended voltagesettings, wire feed speed, for the the metal thickness range.As the picture shows there are two main ingredients, they arevoltage settings, and wire feed speed. The voltage settingcontrols the voltage and when choosing them it is best to usethe electrodes manufactures voltage recommendations. When

choosing a voltage ranges there are two factors thatdetermine it, electrode size, and metal thickness. After thatyou can fine tune your settings to your comfort level. The wirefeed speed setting is what controls the amperage and manytimes the transfer type. The faster the wire feeds to the joint,the more contact the wire has, and that increases theamperage. Most of the time you want the sound of the weld tohave a fast deep crackle to it. This is very important whenwelding overhead! The overhead position needs the wirespeed feed fast enough to avoid globs being formed. If globsstart forming on the end of the electrode, you will soon findthe nozzle getting filled with spatter, and chances are you willfind some of that spatter burning you!

There is sometimes a third ingredient when the flux cored electrode is a dual shield type electrode. That is the gas flowrate for the shielding gas. This varies for the type of wire size used, cup size, and windy conditions. On my 3G FCAWWelding certification I used around 30 CFH in a class room setting. But other times when welding in drafty conditions Ihad to go as high as 60 CFH on the gas setting.

In the case the welding machine used is a MIG welder; the rollers need to be changed to the proper size. In addition tothe proper roller size, the tension settings on the rollers should not be too tight. Otherwise the electrode will getcrushed in the rollers and cause problems in the weld. When setting the tension of the rollers they should be looseenough that it is easy for the rollers to slip when the wire is stopped. On the other hand the tension should be tightenough to keep the wire feeding to the joint without any disturbing the wire speed allowing a stable arc. Don't forget thetip, nozzle, and liner (if needed).

FCAW Welding Techniques

Before trying to weld with the flux cored electrode,first you need to know the designation on the label. Remember fluxcored electrodes come with two position designations. First is "0" and that's for flat and horizontal welding ONLY! Thesecond designation is "1" and that is for all position welding! Always know what the electrode is designed to do.

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FCAW is very similar to MIG welding when it comes to welding techniques! The main difference is how the puddle looksand the fact that welds are covered in f lux much like stick welding.

The first thing to consider is if you need to weld back hand or fore hand. Either technique can be used for any positionand remember these are just guidelines!

Back hand welding is when the handle of the welder is dragged like a Stickwelder. The back hand technique is common for flux core welding in the flatand horizontal positions. The only other time you may want to consider theback hand technique is when welding in the 4G position. The reason for thisis to avoid getting spatter on yourself. I tried welding a grove weld in theoverhead position using the fore hand technique and quickly got burned by afew sparks that got inside my leather. The picture on the left shows thespatter the nozzle got from welding in the overhead position, this is typical,and unavoidable. The down side of back hand welding is that the weld puddleis a little harder to see.Also when welding overhead the machine set-up mustbe perfect! If you are less experienced you may find you weld wonders off ofthe weld joint without knowing it. You typically focus on the weld puddle sizebehind the crater just like stick welding. This method produces a very deeppenetrating, high, and narrow weld.

This picture is a weld I did in the 4G position, even though the back handtechnique produces a high weld, they look pretty much like it was welded inthe flat position. The fore hand method is when the welding handle is pushedin the direction of the travel. This method is typically used on thinner metals,in the vertical up, and for overhead fillet welds (4F). The fore hand methodalso work well in the flat or horizontal position. This method of travel makesseeing the weld puddle easy. This allows you to see the weld joint easier andthe chances of wandering off of the joint are not very likely. The down side ofthis technique is spatter can sometimes become excessive if the travel angleis not right.

When FCAW the electrode extension or stick-out is greater when compared toMIG welding. MIG welding requires the electrode extension to be typically ofan inch or less; otherwise the shielding gas wont do its job. With dualshielding the or less stick-out does apply in many situations. When FCAWwith a self shielded electrode, extension should be kept about of an inch ormore, depending on the type, and side of the electrode. In many cases theextra electrode stick-out pre-heats the electrode. This in return help dry offthe flux inside the wire, and prevents much of the moisture the flux may haveabsorbed in storage from contaminating the weld. The picture on the right is aflux core weld done on a scrap metal, with to short of a stick-out, and somemoisture in the wire resulting in weld porosity.

When it comes to flux core welding techniques there are no simple answers. Most of the techniques are the same aswith all welding processes. For instance the whip of the weld, doing circles, and weave techniques used for widerwelds. When it comes to doing wider weave welds, it is the least common. Most flux core electrodes are typicallydesigned for stringer beads. Many times on wider welds the flux will peel off by itself without chipping. The picturesbelow are the cap of a 3G weld done using dual shielding, C25 gas, and E71T-1. All it takes is just a tap with achipping hammer and the flux just drops to the floor!

The angles to weld in different positions are similar to MIG welding! What changes when using flux core welding is acombination of many different factors like, electrode types, flux types, shielding gas (if any), and the thickness of themetal welded! It comes down to practicing with a specific type of electrode, on the same thickness of metal, by using atrial and error method. What works with one electrode type and metal thickness, may not work with another. I havepersonally found that welding overhead requires a perfect angle, and a precisely set-up machine in order to get the jobdone. The overhead angle is about 10 degrees, no matter if the method is fore hand or back hand. Otherwise it willseem like it is impossible to get a good weld. All of the other positions are not as critical when it comes to travel angle.Just like any other welding process it is best to take a piece of scrap metal similar to the piece to be welded and do a

quick practice run before welding!

The Conclusion

The reality of flux core arc welding is using a typical MIG welding machine and mostly the same equipment, with a fewsmall exceptions! Although they are considered two different types of welding processes, it is only the electrode type,and shielding type, that separate them. Learning and understanding flux core welding is about learning to use adifferent type of electrode in a MIG welding machine. That is all there really is to flux core arc welding.

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