November 24, 2009
Did you hear the one about the welder who was tired of bending over to weld and made the fatal mistake of using a 55-gallon drum as a welding table? In this article, welding instructor Marty Rice discusses this mistake and describes some common technical mistakes new welders make, some more serious than others. All can be avoided.
New welders naturally will make plenty of technical mistakes. By Merriam-Webster's definition, technical means "having special and usually practical knowledge, especially of a mechanical or scientific subject." Even if the new welder has completed a technical/trade school or college welding program, the practical knowledge comes from actually doing it on the job.
Theoretical knowledge comes from books and courses; practical knowledge comes from getting out there and doing it. Mistakes also come from getting out there and doing it. Some mistakes are OK and can actually help you learn. Forgetting to turn the shielding gas on before you run a gas metal arc weld (GMAW or MIG) will create an uneven, porosity-filled weld that looks like crap. Make that mistake once, and you most likely won't make it again. This mistake that falls in the "helping you learn" category can be fixed with a grinder. Actually, many welding mistakes can be fixed with a torch and grinder.
However, some technical mistakes are not so easy to fix and could lead to serious consequences, such as equipment failure, ruined materials, injury, or even death. Ours is a great trade, but also a dangerous trade, and some technical mistakes can be devastating.
It's easy for me to write about technical mistakes new welders make because I was a new welder once and made plenty of them. (As a matter of fact, I still make a lot, but that's a whole 'nother story.) Safety can never be stressed enough, and I advise new welders to learn all they can about welding safety by studying the guidelines from the major manufacturers, schools, and field texts. See the resource list at the end of this article.
Every year I hear of someone getting maimed or killed—or causing someone else to be injured or killed—because of a technical mistake. An example I read a while back was of a fellow who was welding on a big plate from a dump truck. He had the plate on the ground and got tired of leaning down to weld on it. He saw a 55-gallon drum, brought it over, and used it as a table to weld on; he had no idea what was inside. His technical mistake was twofold in that he should have known never to use an unfamiliar container, because they can hold toxic, flammable, or explosive substances, all three of which can maim or kill you.
The next and last technical mistake he made was striking the arc on the container to get it going. 7018 welding rods usually strike pretty easily at first, but once you stop welding, the slag covers over the filler rod (which the current flows through) and must be struck just right to restart the arc. You have to either scratch-start it pretty danged hard, or kind of hammer down and scratch-start at the same time. It's a skill acquired by doing it over and over again, and mastering it has driven many a new welder crazy. When the process is done incorrectly, the electrode sticks to the work. I had a student a few years ago who became so frustrated in his attempts to start the arc that he destroyed his $300 custom hood!
Here's a tip: Do not get in a fight with an inanimate object. You know, like punching your engine block when your ratchet slips on a stripped bolt and you skin your knuckles? You either will hurt yourself, or cost yourself money like my student did. Much better to take a break, gather your thoughts, and start again after you've cooled down. It seems as though every year I also have a student come in with a swollen hand from punching a wall—usually because of parent or girlfriend problems. You cannot weld well with a big ol' cast on your hand!
A good welder strikes the arc exactly where the weld is to begin or exactly in the crater on an existing bead. On many critical tests, such as a nuclear project, if you strike the arc anywhere other than these spots, you fail the test, even if your beads are perfect.
A big technical mistake newbies make is striking the arc on the welding table at school, or on a piece of scrap, and then carrying it over to the weld plate. Another mistake is taking the rod and scratching the slag off on a rough wall, or whatever, and then putting it in the stinger and striking it. Do this on the job and you'll be run off.
In the example of the welder who used a container for a welding table, when he struck the arc on the drum, the vapors inside exploded and, ironically, propelled the heavy plate he was working on into his head, killing him instantly. Whether you're using an old-school hood or a new quick-change helmet, strike the arc exactly where you want it. If you use an old-school hood, you need a firm foundation and a nod.
Your firm foundation is you leaning against something or doing whatever you can to become as physically comfortable and stable as possible. Position your rod right where you want to start, and then nod your head to make your hood come down. Do not get into the habit of having to push down your hood with one of your hands. Doing so can cause you to move your rod from where you want it to strike. Again, the more you do this, the better you get. The more you burn, the better you'll be.
And while we're on foundations, you have to learn to relax your hand if you want to be a good welder. The more relaxed your hand is, the more weld pool control you have. Relax your hand and watch the puddle. That is the most fundamental aspect of welding, yet many new welders cannot get it through their heads to relax and instead put a death grip on the stinger. I guess it's just human nature to want to hold onto something tightly; even after a lot of years in the trade I'll find myself gripping the stinger or gun too tightly and have to make myself relax. But you gotta learn to do it, because welding is done with the wrist, and if the wrist isn't relaxed, you ain't gonna get a good weld.
New welders often forget that in welding, "cleanliness is next to godliness." If you don't clean oil, dirt, grease, rust, and mill scale off the workpiece, you risk contaminating the weld.
Using the wrong rod or process is a common mistake among new welders, as is using the wrong rod or wire diameter. Using the wrong machine with the wrong duty cycle or the wrong polarity setting (direct current electrode positive, DCEP, should be used for thick, direct current electrode negative, DCEN, for thin) is a technical mistake that shows the welder doesn't have a clue about what's going on.
Many new welders use the wrong temperature settings. Speaking of temperature, never change the temperature setting (amps) on a stick welding machine when it is under a load (being used for welding) because you can get electrocuted.
Not knowing the base metal they are working on is a huge technical mistake new welders make. A good welder not only knows how to run a bead, but also knows what the base metal is made of (for example, mild steel is 0.33 percent carbon and iron; stainless is mild steel alloyed with chromium), what the weld will do to the base metal (i.e., heat-affected zone), whether pre- or postheating is necessary, and the metal's machining capabilities.
Another big-time technical mistake that both new and longtime welders make is using 7018 low-hydrogen rods incorrectly. Because of its low hydrogen characteristic, 7018 has a low tolerance for moisture. If moisture gets in the flux, the weld can suffer from excessive porosity.
The best way to use these rods is to take them directly from a hermetically sealed container. If you are using rods from an open container, first put them in an oven and heat them to the correct temperature. And no, I'm not talking about using an old refrigerator with a light bulb in it to heat up the rod, like I've seen done on many shop and field jobs.
The heat needs to be accurate, and the only way you're gonna get that is by using a professional rod oven. 7018 can be reheated one time at a specified temperature in a rod oven (Figure 1).
Photo courtesy of http://rodovens.com
These are but a few technical mistakes new welders make. These and others can be avoided by burning and learning. As I've said in many articles, learn all you can from trade school and college courses, welding manuals, and the vast media available nowadays on the Net, such as articles, educational sites, and videos.
Learn all you can from journeymen and -women who have seen and done it. If they are worth a dang, they will go out of their way to help you avoid mistakes. Do not teach yourself to weld, because you will not know when you are doing something wrong. There are some things you can learn by yourself, but you must be evaluated by someone who knows welding if you want to learn correctly.
Never get in the "comfort zone," and never stop learning. One of the things I love about welding is how I am always learning something new. Welding is a very diverse and complex trade with a whole lot to learn. Make learning a lifelong experience and burn, baby, burn.