BEST PRACTICES FOR USING LOW HYDROGEN SMAW ELECTRODES
This class of stick electrode also is ideal for use in joints involving high-strength, high carbon or low alloy steels. The E7018 electrode’s wide versatility makes it a workhorse for many SMAW applications.
PROPER TECHNIQUES & TROUBLESHOOTING
Success in achieving X-ray quality welds using E7018 or any low hydrogen electrode in the SMAW process comes down to technique. Porosity and cracking are the most prevalent of these defects.
The first thing to do when starting a weld is to hold a very short arc because the longer the arc length, the higher the possibility of arc-start porosity. Avoid creating a gap between the electrode and the work piece. Instead, keep a small distance between them. Pulling a long arc means you are moving too far away from your work, potentially causing issues with the slag that result in mechanical defects.
Long arcs are the most common culprit for causing porosity issues with low hydrogen SMAW welding. Most people have the tendency to touch the plate, pull back on the electrode and go back into the plate. When you long arc an electrode the actual voltage value goes up and makes the arc hotter, creating a gap between the welding puddle and the electrode.
You cannot count on slag to protect the area when you pull too far out of the joint. This leaves a gap in the shielding gas that can cause the material to prematurely melt without slag.
Be sure to set the welding power source in the correct amperage range while welding. The electrode’s flux is designed to do a few important things, including protecting the weld. But if you run at too high of an amperage, you will prematurely destroy the coating and cause defects in the weld.
Also, do not set the hot start control on the machine too high because it can generate a long arc and prematurely melt the electrode’s coating. This creates insufficient shielding and, ultimately, porosity in the weld.
A useful note to keep in mind: The rule of thumb for low hydrogen amperage range, every thousandth is an amp, e.g., ¼ in = .25 in = 250 amps, ⅛ in = .125 in = 125 amps).
Next, do not whip the electrode out of the puddle. While there are certain electrodes that you can manipulate, low hydrogen electrodes perform better when you maintain a drag at (preferably) a 5 deg to 10 deg angle, slightly up in the same travel direction. Be sure to aim it up from the puddle. Too much of a drag angle will cause your weld to fingernail – the phenomenon that occurs when the electrode coating burns off unevenly and leaves a large piece of heavy coating behind on the weld.
When welding the second pass, use a weaving motion or stringer technique. If you opt to weave, think of the number “8” lying sideways and move from left to right in that motion. Pay close attention to the bead width when using the weaving technique. Try to keep it at ¾ in or smaller for the maximum width overall after multiple passes. For the stringer motion, create the letter “I” and follow in a straight motion.
Another important thing to keep in mind is the fact that electrodes last only so long. You will get only so many inches of weld with a single electrode before needing to restart your work with a new one. Be aware that restarting can cause a variety of problems if not done with care.
One of the most common issues occurring with restarting is that the welder gets too much of an upward rod angle and creates fingernailing or a long arc situation. Many people start too high and drag it above the crater. To avoid these scenarios when restarting an electrode, start about ¼ in to ½ in above your work or the previous weld.
Think of it this way: If you had an 8 in plate and you weld 3 in, many people would try to strike the arc at the top and drag down to where the weld ends. Instead, start no more than ¼ in to ½ in above the crater to keep the joint as clean as possible. You want to angle the electrode directly into the joint at no more than 5 deg or 10 deg.
Sometimes you might not burn up the entire rod during a job and may want to restart with that same electrode at another time. It is likely, however, that the electrode tip has hardened, leaving the covering brittle and tough.
If you are like most people, you are going to want to put the electrode in a holder and bang it on the plate like a hammer. Do not do this because banging can chip the electrode’s coating, affect slag production and cause the weld to go off center and crack.
Instead, disconnect the electrode from the stinger and roughly rub it on the surface of the welding table. Again, do not bang the electrode. Scratch it to expose the core wire so you can make a good connection and have proper conditions for good arc shielding.
Additionally, proper storage of low hydrogen electrodes is critical once the container has been opened to prevent moisture pick up. Low hydrogen electrodes can be re-dried if proper care and technique is used. Please consult the electrode manufacturer for their recommendations.
Proper training in SMAW techniques is crucial for achieving good results, particularly when work involves low hydrogen electrodes. Understanding how these electrodes function and exploring the proper techniques required to deliver X-ray quality welds will pay big dividends in better weld quality and fewer porosity defects.
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About the Author: Joseph Kolasa is a welding school instructor and Joseph Murlin is the SMAW consumable product manager at The Lincoln Electric Company, 22800 Saint Clair Avenue, Cleveland, OH 44117-8542, www.lincolnelectric.com.