What are welding electrodes?
Welding electrodes are lengths of wire that are connected with your welding machine to create an electric arc. Current passes through this wire to produce an arc, which generates a lot of heat to melt and fuse metal for welding.
An electrode is a coated metal wire. It is made of materials similar to the metal being welded. For starters, there are consumable and non-consumable electrodes. In shield metal arc welding (SMAW) also known as a stick, electrodes are consumable, which means that the electrode is consumed during its use and melts with the weld.
In Tungsten Inert Gas welding (TIG) electrodes are non-consumable, so they don’t melt and become part of the weld. With Gas Metal Arc Welding (GMAW) or MIG welding, electrodes are continuously fed wire. Flux-cored arc welding requires a continuously fed consumable tubular electrode containing a flux.
MORE: What is Welding?
How To Choose Welding Electrodes?
Stick electrodes are available in a wide range of types, each of which provides different mechanical properties and operates with a specific type of welding power source. There are several factors to consider in welding rod selection:
- Base metal properties
- Tensile strength
- Welding current
- Base metal thickness, shape and joint fit-up
- Welding position
- Specification and service conditions
- Environmental job conditions
Before you power up your machine and pick up your electrode holder, learn more about each of these factors.
Base metal properties
The first step in choosing an electrode is to determine your base metal composition. Your goal is to match (or closely match) the electrode composition to the base metal type, which will help ensure a strong weld. If you’re in doubt about the composition of your base metal, ask yourself these questions:
- What does the metal look like? If you’re working with a broken part or component, check for a coarse and grainy internal surface, which usually means the base material is cast metal.
- Is the metal magnetic? If the base metal is magnetic, chances are good that the base metal is carbon steel or alloy steel. If the base metal is not magnetic, the material could be manganese steel, 300 series austenitic stainless steel, or a non-ferrous alloy such as aluminum, brass, copper, or titanium.
- What kind of sparks does the metal give off when touched by a grinder? As a rule of thumb, more flare in the sparks indicates a higher carbon content such as in A-36 grade steel.
Does a chisel “bite” into the base metal or bounce off? A chisel will bite into a softer metal, such as mild steel or aluminum, and bounce off of harder metals, such as high carbon steel, chrome-moly, or cast iron.
To prevent cracking or other weld discontinuities, match the minimum tensile strength of the electrode to the tensile strength of the base metal. You can identify a stick electrode’s tensile strength by referring to the first two digits of the AWS classification printed on the side of the electrode.
For example, the number “60” on an E6011 electrode indicates that the filler metal produces a weld bead with a minimum tensile strength of 60,000 psi and, as a result, would work well with steel of similar tensile strength.
Some electrodes can be used with only AC or DC power sources while other electrodes are compatible with both. To determine the correct current type for a particular electrode, refer to the fourth digit of the AWS classification, which represents the type of coating and type of compatible welding current (see
The type of current you use also influences the penetration profile of the resulting weld. For example, a DCEP compatible electrode, such as an E6010, delivers deep penetration and produces an extremely tight arc.
It also has the ability to “dig” through rust, oil, paint, and dirt. A DCEN compatible electrode, such as an E6012, provides mild penetration and works well when bridging two joints or welding high speed, high current fillet welds in the horizontal position.
An AC-compatible electrode, such as an E6013, produces a soft arc with medium penetration and should be used to weld clean, new sheet metal.
Base metal thickness, shape and joint fit-up
Thick materials require an electrode with maximum ductility and low hydrogen to prevent weld cracking. Electrodes with AWS classification numbers ending in 15, 16, or 18 provide excellent low–hydrogen properties and good toughness (high impact values) to accommodate for residual stress.
For thin materials, you will need an electrode that produces soft arcs, such as a 6013. Also, smaller diameter electrodes will provide shallow penetration to help prevent burn-through on thinner materials.
You’ll also want to assess the joint design and fit-up. If you’re working on a joint with a tight fit-up or one that is not beveled, use an electrode that provides a digging arc to ensure sufficient penetration, such as an E6010 or E6011. For materials with wide root openings, select an electrode, such as an E6012, that creates a concave weld face suitable for bridging gaps and making groove welds.
To determine what position(s) a particular electrode is qualified for, refer to the third digit in AWS classification. Here’s how you decipher the qualified electrodeposition:
- 1 = flat, horizontal, vertical, and overhead
- 2 = flat and horizontal only
For example, a 7018 electrode can be used in flat, horizontal, vertical, and overhead positions.
Specification and service conditions
Make sure to assess the conditions that the welded part will encounter throughout its service. If it will be used in high heat or low-temperature environments subjected to repetitive shock loading, a low hydrogen electrode with higher ductility will reduce the chance of weld cracking.
Also, be certain to check for welding specifications if you’re working on critical applications such as pressure vessel or boiler fabrication. In most cases, these welding specifications will require you to use specific types of electrodes.
Environmental job conditions
To achieve the best results, you should always remove excessive mill scale, rust, moisture, paint, and grease. Clean base metals help prevent porosity and increase travel speeds.
If cleaning your base metal is not possible, E6010 or E6011 electrodes deliver a deeply penetrating arc that has the ability to cut through contaminants.
How To Read The Code On Stick Electrodes?
The American Welding Society (AWS) has a numbering system that offers information about a specific electrode, such as what application it is best used for and how it should be operated for maximum efficacy.
|Digit||Type of Coating||Welding Current|
|0||High cellulose sodium||DC+|
|1||High cellulose potassium||AC, DC+ or DC-|
|2||High titania sodium||AC, DC-|
|3||High titania potassium||AC, DC+|
|4||Iron powder, titania||AC, DC+ or DC-|
|5||Low hydrogen sodium||DC+|
|6||Low hydrogen potassium||AC, DC+|
|7||High iron oxide, potassium powder||AC, DC+ or DC-|
|8||Low hydrogen potassium, iron powder||AC, DC+ or DC-|
The “E” indicates an arc welding electrode. The first two digits of a 4-digit number and the first three digits of a 5-digit number stand for tensile strength. For example, E6010 means 60,000 pounds per square inch (PSI) tensile strength, and E10018 means 100,000 psi tensile strength.
The next to last digit indicates position. So, “1” stands for an all-position electrode, “2” for a flat and horizontal electrode, and “4” for a flat, horizontal, vertical down, and overhead electrode. The last two digits specify the type of coating and the welding current.
|Electrode||Tensile Strength||Position||Type of Coating & Current|
What is the welding electrode coating?
Electrode coatings should provide gas shielding for the arc, easy striking and arc stability, a protective slag, good weld shape, and most important of all a gas shield consuming the surrounding oxygen and protecting the molten weld metal.
Various electrode types are available, the type often being defined by the nature of the coating.
Electrode Coating is covered with a relatively high-quality covering applied in a layer of 1 to 3mm thick. The weight of such a coating is from 15 to 30% of the electrode weight. The greatest of welding is done with coated electrodes. This restricts the process to a slow manual operation. If the flux coating is placed inside a long tube, the electrode can be in the form of a bare wire in the form of a coil.
Then the shielded arc process can be made continuous and automatic. The primary purpose of a light coating is to increase arc stability; the coating is also called an ionizing coating. Since the electrode coating is brittle only straight stick electrodes can be used.
The function of Electrode coatings
- Improving the arc stability by providing certain chemicals which have this ability by ionizing the path of the arc
- Provide a protective gaseous atmosphere to prevent oxygen, hydrogen, and nitrogen picks up by the molten metal.
- Protective slag over hot metal
- Provide flux, which helps to remove oxides and other impurities from the molten metals
- Reduce spatter of weld metal – when coating burns off slower than the core.
- Acts as deoxidizer
- Slow down the cooling rate of the weld (due to the protective layer of slag) to prevent hardening.
- Coatings are normally insulators of electricity and so prevent the use of electrodes in narrow grooves etc.,
Types of Coatings:
While there are universal characteristics within each type of electrode coating, the unique chemical makeup of each individual coating will provide different properties. Be sure to research the best applications of each coating to make sure you choose one that suits your project well.
These coatings are comprised of around one-third cellulose and two-thirds other organic materials. When exposed to the welding arc, the materials decompose to form three separate gases—hydrogen, carbon monoxide, and carbon dioxide that strengthen the arc. This added strength allows the current to more deeply penetrate the metal, resulting in stronger welds.
Cellulose coatings also emit a layer of gas to protect the weld pool from impurities. The gas layer creates a barrier between the metal and other elements, like oxygen, nitrogen, and hydrogen, that can create porosity in a weld. Porousness is poison for a weld, so using electrodes with cellulose coating can help ensure higher quality weld joints.
Cellulose coatings come in a variety of chemical mixtures, each with its own unique properties and best applications. While the cellulose component of the recipe is a general rule of thumb, the additional organic materials vary greatly.
Mineral coatings leave a layer of slag over the weld. While the slag might seem like an annoying side effect, it actually serves a very useful purpose. The slag from a mineral-coated electrode cools much slower than a cellulose-coated electrode and the welded material underneath.
This allows time for impurities to filter to the surface of the metal, preventing them from compromising the structure of the weld.
Electrode coatings with a combination of cellulose and minerals are a popular choice among fabricators because they provide the best of both worlds. Since these coatings can have anywhere from just a few components to upwards of 10 different ingredients, the chemical diversity of these coatings provides a range of significant benefits.
Having both shielding gas and slag protection on a weld can be incredibly useful when working with particularly temperamental base metals.
Most Common Electrode Coatings:
While there are certain applications requiring specific electrode coatings and characteristics, these are five of the most common welding electrode coatings you’re likely to see.
Well suited for vertical positioning, cellulose electrodes leave behind a very thin, very easy-to-remove layer of slag. Cellulose coatings break down into hydrogen and carbon dioxide as they are heated. This provides an effective protective gas layer over the weld pool.
However, this can also place the weld at risk for hydrogen embrittlement. In their purest form, cellulose coatings work best with DC. However, the addition of different elements to the coating may allow for use with AC as well. Cellulose electrodes give you all the ease of a rutile coating, but with deeper penetration and less problematic slag.
Nearly identical to cellulose, the main difference is that rutile has a higher percentage of titanium dioxide. This creates a gas shield of oxygen, nitrogen, carbon, and hydrogen, making rutile electrodes well-suited for welding low carbon steel.
However, slag from rutile electrodes can tend to leave behind traces of titanium in the deposited metal. The addition of cellulose to rutile electrode coatings provides added protection over the weld pool. These electrodes give off lower levels of both spatter and fume emissions and are great for use in all positions.
Iron Oxide Electrodes:
Good for use with both AC and DC current, iron oxide electrodes produce slag that is very easy to remove from the weld. The chemical composition of this coating is high in oxygen and can tend to cause weld deposits that are weaker in overall strength.
The risk of hydrogen embrittlement, though, is significantly lower than with cellulose electrodes. Iron oxide electrodes provide great arc control and allow for neat, precise bead placement.
Also referred to as hydrogen-controlled electrodes, these electrodes require a bit more care prior to welding. Electrodes must be stored in a dry location and baked before use. Failure to do so can create an unstable chemical composition in the coating resulting in a compromised weld structure.
Basic electrodes deposit a low, controlled level of hydrogen which minimizes the risk of porosity and cracking in a weld. If properly stored and maintained, these electrodes a great option for working with steel.
Iron Powder Electrodes:
These electrodes are variations of other electrode coatings resulting from the addition of iron powder to a mix. Metal powders are becoming an increasingly popular addition to electrode coating mixtures as they can help increase efficiency and overall weld quality. Iron power electrodes are a common variation on cellulose electrodes that enable the electrode for use with AC.
When working with a type of welding that requires separate, coated electrodes, taking the time to understand the different options available can make or break a project. Remember to consider additional factors—such as position, tensile strength, and core metals—when deciding on an electrode.
types of welding electrodes
TIG welding, on the other hand, employs non-consumable electrodes. These electrodes consist mostly of tungsten, which does not melt (unlike consumable electrodes) due to its high melting point. It merely supplies an electric arc for welding. The filler material is provided using a wire that is manually fed.
Hence, the main difference between the two is that consumable electrodes melt, whereas non-consumable electrodes do not.
The two categories have several types of electrodes, as well.
Consumable electrodes are the key to stick, MIG, and flux-cored arc welding. The consumable electrodes used for stick welding are called stick electrodes. These include heavy-coated electrodes, shielded arc, and light-coated electrodes.
1. Light coated electrodes
As the name implies, light-coated electrodes have a thin coating on their surface, which is applied by methods like spraying and brushing.
These electrodes and their coatings are made from several different materials. The filler material bears a lot of similarities to the base metal that is being welded.
The light coating also serves another vital purpose. This coating reduces impurities, such as sulfur and oxide, to give a better quality weld. It also allows more consistent melting of the filler material so that you can create a smooth-looking and reliable weld bead.
Since the coating is thin, the slag produced is not too thick. Shielded arc electrodes bear some similarities to light-coated electrodes. The main difference is that they have a thicker coating. These heavy-duty electrodes are suitable for more demanding welding applications, for instance, the welding of cast iron.
2. Bare electrodes
Using bare electrodes can be tricky because the arc is somewhat unstable and difficult to control. The light coating increases the stability of the electric arc, thereby making it easier for you to manage. Bare electrodes have limited applications. For example, they are used for welding manganese steel.
3. Shielded arc electrodes
Shielded arc electrodes have three different types of coatings, which serve different purposes. One kind of coating contains cellulose, and it uses a protective gas layer to protect the weld region. The second type of coating has minerals that produce slag. The third kind of coating has a combination of minerals and cellulose.
Shielded arc electrodes generate a protective gas layer, which forms an effective barrier to shield the hot weld zone from contamination and corrosion by the surrounding air. This results in stronger and more reliable welds. The heated weld zone must be kept safe from atmospheric gases like nitrogen and oxygen, which react with the high-temperature metal to produce brittle, porous, and weak welds.
Shielded arc electrodes minimize sulfur, oxides, and other types of impurities within the base metal to give regular, smooth, and clean welds. These coated electrodes also produce a more stable electric arc compared to bare electrodes, which makes welding more manageable and reduces spattering.
Shielded arc electrodes also produce slag due to the mineral coating. This slag appears to be a hassle to remove, but it serves a beneficial purpose. It cools much more slowly as compared to shielded arc electrodes. This process draws out impurities and sends them to the surface. Consequently, you will get high-quality welds that are clean, durable, and strong.
Non-consumable electrodes are simpler to understand not only because they do not melt but also because there are only two types.
1. Carbon electrodes
The first kind is the carbon electrode that is used for both cutting and welding. This electrode is made out of carbon graphite. It may be coated with a copper layer or left bare.
The American Welding Society has not issued any specifications for this kind of electrode. However, military specifications do exist for carbon electrodes.
2. Tungsten electrodes and their different kinds
The second kind of non-consumable electrode is the tungsten electrode, which is used for TIG welding. These electrodes consist of pure tungsten (which have green markings), tungsten-containing 0.3 to 0.5 percent zirconium (these have brown markings), tungsten with 2 percent thorium (which have red markings), and tungsten-containing 1 percent thorium (which has yellow markings).
Non-consumable electrodes made from pure tungsten, have limited use, and are suitable for light welding jobs. There are two reasons for this. First, pure tungsten does not possess the durability and strength of tungsten alloys. Second, pure tungsten can suffer problems with high currents.
Tungsten electrodes with 0.3 to 0.5 percent zirconium offer excellent results with alternating current. They are an improvement over pure tungsten, but not as good as tungsten electrodes with thorium content.
Tungsten electrodes with 1-2% thorium content are some of the most widely used non-consumable electrodes since they last longer and have a higher resistance than other kinds of tungsten electrodes. They can be used for higher currents compared to pure tungsten electrodes. These electrodes also provide greater arc control and are easier to start.
While using a tungsten electrode, it is better to use the maximum allowable current if they have a plain cylindrical, or else it becomes difficult to control the arc and sustain it.
For better arc control and stability, you should grind the tips of these electrodes to a point, that is, you need to make the tips conical. If you do this, you will have to select touch-starting instead of DC welding machines.
Remember that tungsten electrodes with thorium and zirconium will have improved durability than pure tungsten electrodes if you opt for tapered electrodes using touch-start.