FCAW pretty much can do it all

THE FABRICATOR® MAY 2005

September 26, 2002

By:

FCAW not only is easy to teach and to use, it's one of the most flexible welding processes around.

Any welder who has been in the trade very long has a lot of interesting tales to tell, and I've got quite a few myself.

I started out in an oil and agriculture equipment repair shop. We repaired and rebuilt bulldozers, road graders, dirt movers, and the like. I was the maintenance-repair welder, and I mainly used 7018 and 6011 stick welding. (By the way, another name for "maintenance-repair welder" is "Hey you, come fix this now!")

I learned a lot on that job. The scariest project I had there was working overtime all by myself. The place was a few miles outside the city on about 100 acres. I wasn't afraid of the bogeyman or robbers, but I met my fear one night when I decided to start a big D9 bulldozer before I left for home. I just had to hear that big piece of machinery fired up.

This 'dozer was so huge it took up a whole section of the shop and needed a starter motor just to get the engine going. I got it started all right, but once I did, I didn't know how to shut it off! Man, I was freaking out trying to shut that dang thing down, afraid that if I pulled the wrong lever, I'd go flying through the wall. I finally shut it down—after taking a couple of years off my life from all the stress.

The worst part of that job was washing cow manure off bulldozers in a -40-degree wind chill so I could weld or cut on defects. Being the new guy, I always ended up with the high-pressure hose out on the back 40. But that was just part of the job, and doing it made me a better man.

After a year there I took a job in a black-iron fabrication plant. We fabricated and welded structural members (beams, columns, and braces) for the construction industry and worked on plant maintenance and modifications.

After passing a 7018 plate test, I was asked if I could use the flux-core process.

"Of course I can!" I said as I remembered my former welding teachers Phil Newell and Mike Waldrop screaming in my ear to "relax my hand and watch the puddle." Phil once said that if I did those things, along with the other basics, there was no process I couldn't do.

I had a lot to learn, though. Confidence is great as long as it doesn't turn into cockiness. I learned early on to ask questions if I didn't know something and to try to learn all the tricks and tips I could from the old-timers.

I also learned that being in the welding field a long time doesn't guarantee good craftsmanship. There are a few people out there who always have been and always will be slackers, but they usually don't last long on a job. Luckily, most of the old hands in the welding trade are good craftsmen. A welder new to the trade can learn a great deal from them.

When I started in the black-iron shop, my partner was a crusty old World War II veteran. That guy could cuss, gripe, and complain for hours on end, but he was a wealth of information. Under that attitude was a really nice guy who enjoyed teaching me.

We used flux-cored arc welding (FCAW) on just about everything in there. FCAW is an excellent process, whether you are a hobbyist or a skilled structural welder in the shop or field. It is a very efficient process to use in all conditions.

FCAW is very similar to gas metal arc welding (GMAW). In GMAW, a solid steel wire is fed from a spool through drive rolls that push, pull, or push and pull the wire through the gun. The same is true with FCAW.

GMAW uses direct current, electrode positive (DCEP), while FCAW uses direct current, electrode negative (DCEN), or direct current electrode positive (DCEP).

GMAW uses a shielding gas to protect the puddle from contaminants in the atmosphere such as nitrogen and hydrogen. On the other hand, FCAW uses a tubular wire that has flux in the middle. The flux then burns, emitting a shielding gas, which protects the puddle. The flux turns into slag, just as in the shielded metal arc welding (SMAW) process. Shielding gas is not necessary, but it can be used to make a bead even smoother.

Advantages

When using FCAW, a welder does not have to stop and change rods as in SMAW. That means longer beads with fewer restarts, high weld deposit, and more production. This means less chance of defects in the restart area.

The process uses DCEP and produces deep fusion with a good weld appearance. In addition, smaller-diameter wires can be used in all positions.

FCAW can be used with or without shielding gas; if you use shielding gas, carbon dioxide is very cheap. (Other gases, such as 75/25, also can be used.) The flux contains oxidizers, so the base metal needs minimum cleaning before a weld is made. Postweld cleanup is a breeze because the slag chips off very easily.

On top of that, the wire stickout with FCAW is a lot longer than with GMAW (about to inch), so welders can see and control the puddle much better. It couldn't be any better if it welded itself—which it can if it is set up for automatic welding. I usually can have a student welding satisfactorily the first day with FCAW (and GMAW, for that matter).

Disadvantages

Fumes! FCAW puts out more smoke than a Houston barbecue joint. If you are using FCAW in a shop, you really should have a strong point-of-contact ventilation system. If not, your lungs are going to be full of welding fumes, and that just isn't healthy.

Other than the fumes, the only other disadvantage is that FCAW usually is used only on mild steel. It has limited uses for cast iron and stainless, but mild steel is all I've ever seen it used on.

In the Field

The only time I used FCAW in the field was on column splices in which one column was stacked on the one below it. This arrangement uses gusset plates where the bolts are attached, and the column itself is beveled for a groove weld.

The included angle (the sum of both column angles where the beveled edges meet) usually is very wide, which leaves a large amount of welding to be done. These are zero-defect welds that are X-rayed for soundness. Stick welding takes entirely too long for these angles and requires too many restarts, which increase the chance of defects.

With FCAW, one welder sits in a basket on one side of the column while another welds the opposite side. This puts the same amount of heat on each side, eliminating any distortion. It makes for good, continuous beads with little time lost. And in construction, time equals money.

In the Garage

Ahhh—this is the fun part. There are about a billion projects you can use FCAW for in the ol' garage. Heck, you could start a business making cookers, smokers, artwork, and other gadgets if you want to. FCAW is a great process for the home welder, and there are some really nice, affordable machines out there nowadays.

For less than $500 you can get a fully equipped GMAW-FCAW machine that can plug right into your garage's 110 outlet. Just make sure you have the fuses to back it up, or you may start blowing all the circuits in the house. You can pick up a machine for less, but the ones that are right around $500 come set up completely for GMAW or FCAW. I'd lay down the extra bucks and go for it all.

Follow all safety procedures! This cannot be overstated. A former student of mine and his friend burned down his parents' garage (with a car in it) after grabbing a bite to eat. They left a piece they had been welding by some rags, which caught fire with the help of some gasoline, which set the whole place ablaze. No one was hurt, but they lost the garage and a truck they had been working on for about two years.

If you're careful and creative, FCAW has a lot of uses, and it really is a nice process for all skill levels.



High School Career Center in Texas

Marty Rice

Contributing Writer
High School Career Center in Texas
Marty Rice is a welding instructor at a high school career center in Texas. He is an honorary member of the Ironworkers Local 263.

 

Questions for the author can be e-mailed to vickib@thefabricator.com

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