An electrode is one of the most important materials in welding, and the wide selection of electrodes can make a choice quite overwhelming. With some basic information about the factors to consider, choosing the right electrode doesn't have to grind a welder's productivity to a halt.
For starters, there are two basic kinds of electrodes. Consumable electrodes are used up during the stick and MIG welding processes, as they supply the filler metal used in the weld. Non-consumable electrodes are used during the TIG welding process and are typically made of tungsten, which is not burned up during the process. The tungsten electrode helps generate heat with the electrical current and is ground to form a point much like a pencil (though it's flat, not sharp at the end). The welding arc is conducted from the point of the electrode in TIG welding.
While a good deal of information about selecting the right electrode follows, there are many stick welders and instructors who highly recommend certain electrodes for their versatility and ease of use. For stick welders looking to make a quick start, the 6010, 6013, and 7018 electrodes are routinely mentioned as excellent choices. However, choosing the best electrode involves an understanding of the kind of metal it will be used on, the welder's settings, and the specifications for the job.
We'll begin by looking at consumable electrodes for Stick and MIG welding, and then follow with non-consumable electrodes for TIG welding.
While stick and MIG welding both use a consumable electrode, each process is quite different. Stick welding uses a consumable electrode coated in flux to lay the weld, while MIG welding uses a continuous and consumable wire electrode and a shielding gas that are fed through a welding gun (though MIG also offers flux cored wire). Stick offers versatility and portability, and MIG offers a clean, simple, and functional welding process.
Consumable Electrodes for Stick Welding
The speed, power supply, and position of the weld as well as the metal being welded are all factors to consider when selecting an electrode for stick welding. Since stick welding is particularly portable and versatile, there is a wide variety of electrodes available for each situation.
The electrode in stick welding is coated in a metal flux that helps purify and protect the weld. The flux creates a protective layer of slag that must be chipped off. This is quite unlike the consumable electrode wire in MIG welding that is protected by shielding gas and does not require flux or create slag.
There are three primary categories of electrodes for stick welding. Stick electrodes such as E6010 are “fast-freeze” electrodes designed to solidify quickly, making them ideal for all welding positions since the melted electrode won't run. There are “fast-fill” electrodes that melt quickly and offer improved welding speed. There also are intermediate electrodes known as "fill-freeze" or "fast-follow."
It's also critical to remember that the electrode must match or at least be compatible with the base metal that is welded. For example, mild steel works best with an electrode that begins with E60 or E70. In addition, the kind of joint and the amount of weld penetration required will be key factors to consider. While E6013 is an excellent overall choice for an electrode, it's particularly useful for wider weld joints.
The Fabricator provides a helpful guide to the stick electrode classification system used by the AWS with an example of the code used for mild steel electrodes:
- The letter E indicates an electrode.
- The first two digits represent the resulting weld's minimum tensile strength, measured in pounds per square inch (PSI). For example, the number 70 in a E7018 electrode indicates that the electrode will produce a weld bead with a minimum tensile strength of 70,000 PSI.
- The third digit represents the welding positions for which the electrode can be used. For example, 1 means the electrode can be used in all positions and 2 means it can be used on flat and horizontal.
- The fourth digit represents the coating type and the type of welding current (AC, DC, or both) that can be used with the electrode.
Unlike the electrode “sticks” used for stick welding, MIG welding uses a consumable wire that is fed through the welding torch. Much like stick welding, the proper MIG wire or electrode needs to be matched with the type of metal being welded.
Though most welder manuals will specify which wires to use in each situation, the most common MIG wires typically fall into the following range of thickness: .023, .030, .035, and .045. Larger projects, especially industrial ones, may require a thicker wire, but these are the first ones to consider for most projects.
MIG welding has its own classification system for wire electrodes that can be illustrated in the following example for ER 70S-6:
- ER: Electrode or filler rod for MIG or TIG welding.
- 70: 70,000 pounds minimum of tensile strength for each square inch of weld.
- S: Solid wire.
- 6: Amount of deoxidizing and cleansing agent on electrode.
There are many factors to consider for MIG wire since wires must be chosen based on the metal being welded and the type of weld, but in addition, certain wires require different shielding gases.
TIG welding uses a non-consumable electrode made primarily of tungsten (sometimes only tungsten) and conducts the heat and forms the arc. Since the electrode is not melting and forming the actual weld, it's far more important to consider the power settings of the welder and the matching size of the electrode. For example, the higher power of AC welding requires a larger electrode than lower power DC welding. The nature of the weld and the type of material being worked on will determine the appropriate welding set up, which subsequently dictates the best electrode.
The wrong electrode may deteriorate, fall into the weld, and contaminate the weld if the power is too high, while the welding arc will be difficult to control and maintain if there is too little power. It's tempting to use smaller diameter electrodes for TIG welding because the arc is quite easy to start with them, but the quality of the final weld is a higher priority.
Tungsten comes in 5 commonly used grades that are color coded:
- The pure grade of tungsten is color coded green and provides good arc stability for arc welding and is the least expensive.
- Ceriated is color coded orange and also permits easy arc starting, good arc stability, and longevity.
- Thoriated is color coded red and has a higher current capacity than Ceriated and has a high resistance to weld pool contamination, however it is more difficult to maintain a balled end on AC.
- Lanthanated is color coded gold and works much like the thoriated.
- Zirconiated is color coded brown and is probably the most preferred over all of them. It is excellent for AC welding. The higher quality tungsten will always give the best results.
Unless you plan on welding with a respirator, avoid electrodes that produce radiation such as thoriated. Ceriated and lanthanated are both good alternative choices. In fact, ceriated and lanthanated tungsten electrodes offer many of the same advantages as thoriated electrodes with none of the risks of radiation.