A generation ago, manufacturers built welding machines to deliver specific arc characteristics to improve results in specific applications along with using certain types of electrodes. However, based on technology limitations, it could be expensive and somewhat difficult to design a welder that performed equally well in every situation.
Today, inverter technology and microprocessors enable manufacturers to incorporate additional controls that allow operators to make finer adjustments to the arc characteristics. This helps an operator tailor welding performance to match various applications and electrodes. When it comes to the stick welding process, many of the newer multi-process CC/CV inverters offer three key controls that are active when welding in stick mode:
- Electrode type setting (E7018 versus E6010)
- Adjustable arc force control
- Adjustable hot start
However, just because these varied controls are offered doesn’t mean the operator needs to make adjustments to these settings for achieving the best performance. This article provides some guidelines for using these controls for improving welding performance with cellulosic type electrodes (E6010) and low-hydrogen (EXX15, EXX16) and E7018 basic type electrodes, welding with DC-positive polarity.
As a side note, modern TIG/stick inverters with an AC/DC output often provide good E7018 performance in the AC mode, which can improve welding performance and combat arc blow, but that’s a topic for another article.
Electrode selection
If given the option, the one function that operators absolutely want on an inverter is electrode selection control. Simply explained, the electrode selection control automatically adjusts various factors, such as the open circuit voltage and volt/amp curve. This accommodates the operating characteristics required by different electrodes.
As an example, the ESAB Rebel and other multi-process inverters in this category feature two settings: E70XX and E60XX. Larger industrial multiple inverters, such as the Warrior 500i, have three settings that are designated as basic (E7018), rutile (E6013) and cellulosic (E6010).
When welding with stick electrodes, the operator sets the amperage while the voltage output may vary by the design of the power source. The operator can cause the arc voltage to vary by increasing or decreasing the arc length. A slight increase in arc length causes arc voltage to increase and a slight decrease in amperage. With a decrease in arc length, the arc voltage decreases with an increase in amperage. The amount of amperage change depends on machine design and how steeply the volt/amp curve droops; a steep curve produces less change while a flatter curve produces wider change.
Most experienced operators understand the volt/amp curve preferences. For beginners with less experience, a quality inverter with electrode selections helps them to optimize the best performance for different coatings for cellulosic, rutile and basic types.
As a side note, just because an inverter has a setting for cellulosic electrodes doesn’t mean the arc performance will meet expectations. Therefore, it’s recommended to have a “try before you buy” attitude if you plan to weld with E6010, or any electrode really.
Adjustable arc force control
Arc force, as implemented in inverters, is a function that automatically increases amperage when the voltage drops below a set threshold (often around 18 V). In situations where the operator holds a tight arc to force metal to the backside of a joint when using an E6010, the additional amperage help prevents the arc from extinguishing.
For welding with E7018 electrodes, especially on a machine with an electrode selection option, the factory default for arc force will be set at an optimum setting using an arbitrary number between 0 and 100. Low-hydrogen (E7018) electrodes normally require little arc force. The rule of thumb is to start on the low side/factory default and make a test weld while holding a tight arc and feeling some resistance as the arc forces metal into the puddle. If the electrode doesn’t stick, that indicates sufficient arc force. If it does stick, increase the arc force by a small increment, perhaps five percentage points. If the arc seems excessively harsh and creates spatter, reduce it.
Each model and brand of inverter will perform differently. The guideline here is not to use extremely high settings with arc force and also to remember that an inverter’s arc force only works in low-voltage situations.
Of course, given that the proper arc length for an E7018 is approximately 3/32 in. maximum from the weld joint using a 1/8-in.-dia. electrode, those who weld infrequently often struggle to hold a tight arc. Adjustable arc force control can help them achieve good penetration while preventing stuck electrodes (or, let’s be honest, reducing the frequency of stuck electrodes).
Another application where professionals like to use arc force is for welding with a very close arc length or when using a larger electrode at a very low current setting to prevent the electrode from sticking to the part being welded.
Adjustable hot start
During arc starting or restriking of the electrode, the “hot start” setting momentarily boosts the welding current to help establish the molten weld pool on the cold plate and consume the ending of previous weld (if there was one). Some machines enable operators to adjust hot start duration as well as the amount of hot start current, typically expressed as a percentage of the welding current.
Again, the rule of thumb is to start low, make test welds and slowly increase values if needed. A good starting point would be a hot start duration of 0.25 sec. to 0.5 sec. and an additional 15 percent of the set welding current. If the arc starts easily, leave the setting alone. More is not better, as high settings make the electrode run harsher and create spatter and unintended consequences, such as burning away metal outside of the joint.
Whether hot start is used or not, operators must use the correct arc starting technique with E7018. Because of their flux composition, low-hydrogen electrodes may not adequately shield the weld during arc start, and using the hot start cannot compensate for poor technique. For the proper technique, here are some suggestions:
- Strike the arc about 3/16 in. (one or two electrode diameters) in front of where the weld is to begin, such as from the edge of the plate or the end of the previous weld.
- Establish the correct arc length when quickly moving the electrode to melt the back edge of the joint or to tie in the new weld with the previous one.
- Move forward so that the fully established arc welds over the spot of the arc strike.
This technique ensures that the new weld consumes the previous weld stop and, when done properly, eliminates starting porosity where the arc was struck. If there is a big knot or convex bead shape at the junction of the old and new welds, that indicates an incorrect technique, typically a failure to have the arc fully established and consume the previous weld.
As far as arc starts are concerned, everyone who has tried to re-use a partially consumed E7018 electrode knows the end of the rod glazes over, making arc starts extremely difficult. Although the typical solution is to bang the end of the rod to remove the glaze, don’t get into this bad habit. Banging can remove valuable flux. Instead, remove the glaze by scraping the end on a rough surface. You can also take your glove and carefully remove the glaze back to the core wire or perhaps use a file. This keeps the flux in place so it can do its job. If the flux becomes chipped, discard the electrode and use a fresh one.
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