Basic tips for arc welding
Thursday, July 26, 2012 12:39:06 PM Australia/Sydney
Basic Tips to Improve MMAW (Manual Metal Arc Welding) or most commonly known as Stick Welding including tips to help with AC or DC inverter welding machine selection.
• DC welding machines like the Lincoln, Toolex & Unimig inverter range offer many advantages over AC for almost all Stick welding applications, including: easier starts, less sticking, less spatter/better looking welds, easier vertical up and overhead welding, easier to learn "how to weld" and these machines also offer a smoother arc.
• AC welding machines also have their place in the market for value & cost of machines, robustness and their ability to weld any metals that may be magnetised due to wearing or rubbing components. Eg, farm machinery.
• Duty cycle is the number of minutes a machine will run for out of a 10 minute block in time eg 35% @ 135 amps. This means the machine will run for 3.5 minutes @ 135 amps.
Always try to properly clean any parts prior to welding. The best method is with an angle grinder or wire brush, remember preparation is the name of the game & although arc welding can be a lot more forgiving than welding with a tig or mig machine. Most skilled welders would have no real issues burning through some residual grease or rust with an arc welder. However the industry standard is as always "MAKE SURE IT IS CLEAN".
A good way to remember the basic's of stick welding is to remember the word CLAMS: Current setting, Length of arc, Angle of electrode, Manipulation of the electrode and Speed of travel. remembering the principal of these five points will help you become a champion welder. (this is commonly taught throughout Australia)
Now that you're ready to weld, remember CLAMS. Bringing all of these points together in one action whilst learning to weld may seem very daunting however it will become second nature with practice.
Current setting: The correct current, or amperage, setting mostly depends on the diameter and type of electrode selected. For example, a 3.2mm in. 6010 rod runs well from 75 to 125 amps, while a 4mm 7018 rod welds at currents up to 220 amps. The side of the electrode box will usually tell you the proper operating ranges. The user should select an amperage based on the material's thickness, welding position (about 15 percent less heat for overhead work compared to a flat weld) and visual inspection of the finished weld.
Length of arc: The correct arc length will vary depending on electrode selection and application. As a good starting point, arc length should not be any greater than the diameter of the metal portion of the electrode. Holding the electrode too closely decreases welding voltage. This creates an erratic arc that may extinguish itself or cause the rod to freeze, as well as produces a weld bead with a high crown. Excessively long arcs (too much voltage) produce spatter, low deposition rates, undercuts and porosity.
Beginners will generally weld with too long of an arc, this means they will produce rough weld beads with lots of spatter. Practice will show you that a tight, controlled arc length improves weld appearance as well as creates a narrower bead and greatly reduces spatter.
Angle of travel: Stick welding flat, horizontal and overhead uses a "drag" technique. Hold the rod perpendicular to the joint and tilt the top of the electrode in the direction of travel approximately 5 to 15 degrees. For welding vertical up, use a "push" technique and tilt the top of the rod 15 degrees away from the direction of travel.
Manipulation: In Australia we are not taught to weave an electrode like the Americans do. Welders and apprentice welders passing through Australian Technical college's & the like are taught when welding thicker material you should place down more runs rather than trying to weave one run. For people that choose to weave you will find your welds will end up with undercuts & over welding which will cause cracks and other issues. The most common process we use is called a 3 run 2 layer weld. The best way to describe this is by laying a "root weld" which will be placed in the very centre of the joint. You would then place a second run at the lower edge of the root weld. The third weld is then placed at the top edge of the root weld. By welding with this process the user will see two finished welds with the top weld overlapping the bottom weld and both welds then covering the root run. This process gives a much more stable and even welded joint.
When welding vertical up, focus on welding the sides of the joint and the middle will take care of itself, always remember to lay down that all important root run before attempting a vertical up. Pause slightly at the side to allow the far side of the bead to cool, the weld puddle to catch up, and to ensure solid "tie-in" to the sidewall. If your weld looks like fish scales, you moved forward too quickly and didn't hold long enough on the sides.
If you are hardfacing metal, always place your runs with a very cold (low amp) setting. The general idea is to lay down a weld with little penetration, by keeping the amps low you will find the weld metal will sit high on the work piece. A good tip is to do a crisscross method therefore if you are trying to increase the working life of a cutting edge or a digging bucket the abrasive material i.e. Dirt or mud will get caught in the pattern and subsequently wear against itself instead of the parent material or the hardfacing. Always be careful when hardfacing as it is easy to weaken the parent material and make it prone to cracking or breakage.
Speed of travel: Proper travel speed produces a weld bead with the preferred contour (or "crown"), width and appearance. Adjusting travel speed so that the arc stays within the leading one-third of the weld pool. Slow travel speeds produce a wide, convex bead with shallow penetration. Excessively high travel speeds also decrease penetration and will create a narrower and /or highly crowned bead, and possibly undercuts.
A few last words of advice. Always remember that you need a good view of the weld pool. Otherwise, you can't ensure you're welding in the joint, keeping the arc on the leading edge of the puddle and using the right amount of heat (you can actually see a puddle with too much heat roll out of the joint). For the best view, keep your head off to the side and out of the smoke so you can easily see the puddle. Make sure you are in a comfortable position, do a few practices runs of the weld your about to attempt to ensure you can complete the weld comfortably and to reduce fatigue. Try to limit outside influences like wind, loud noise & poor light. Be aware of your surroundings and always remember clothing catches fire easily, you will never get used to spatter burns so prepare yourself to avoid flinching as best you can. Welding produces UV rays that will burn within minutes so always protect yourself with good quality leather welding jacket's, skull caps, gloves / gauntlets, sock protectors, heavy pants, leather boots and a good quality auto tinting helmet. All of these items will help you be a better welder & I know from experience the cost of an auto tinting helmet is a whole lot cheaper than not being able to close your eyes from sunburn or welders flash because you didn't use your old flip down helmet while tacking.
Remember that learning from your mistakes makes you human. There's no shame in grinding out bad welds. In fact, professional welders create perfect welds by recognizing imperfections, grinding them out and welding them again.
In each of our Gasweld Tool Centres you will find our team members are very knowledgeable and experienced on machine, consumable & safety equipment selection, we like all of our customers to feel free to drop in and browse our extensive range of welding equipment and to let our helpful sales people guide you through which process, machine and consumables will best suit your desired application.