If you are interested in a welding career, you might have already looked into the welding tools and equipment that are used. One of the most essential welding tools is the welding gun or welding machine which produces an electric current that melts and binds metal.
Whether you are a professional welder or a DIY enthusiast, you should know what welding electrodes are. This article will help you to differentiate between different kinds of welding electrodes and give you a good idea of their strengths and weaknesses so that you can determine the best choice for your welding applications. Read on to find out more.
What Are Welding Electrodes?
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.
How To Choose Welding Electrodes?
Now you know, an electrode is a metal wire that is coated. It is made out of materials with a similar composition to the metal being welded.
There are a variety of factors that go into choosing the right electrode for each project. In summary:
- SMAW or stick electrodes are consumable, meaning they become part of the weld and are also referred to as a filler electrode or welding rod.
- TIG tungsten electrodes are non-consumable as they do not melt and become part of the weld, requiring the use of a welding rod.
- TIG filler rods are an optional filler material used to fuse two pieces of stock together as a composite.
- The MIG welding electrode is a continuously fed wire referred to as MIG wire.
Electrode selection is critical to ease of cleanup, weld strength, bead quality, and minimizing any spatter.
Electrodes need to be stored in a moisture-free environment and carefully removed from any package (follow the directions to avoid damage).
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|
Covered Welding Electrodes
When molten metal is exposed to air, it absorbs oxygen and nitrogen and becomes brittle or is otherwise adversely affected. A slag cover is needed to protect molten or to solidify weld metal from the atmosphere. This cover can be obtained from the electrode coating.
The composition of the welding electrode coating determines its usability, the composition of the deposited weld metal, and the electrode specification. The formulation of welding electrode coatings is based on well-established principles of metallurgy, chemistry, and physics.
The coating protects the metal from damage, stabilizes the arc, and improves the weld in other ways, which include:
- Smooth weld metal surface with even edges
- Minimum spatter adjacent to the weld
- A stable welding arc
- Penetration control
- A strong, tough coating
- Easier slag removal
- Improved deposition rate
The metal-arc electrodes may be grouped and classified as bare or thinly coated electrodes and shielded arc or heavy coated electrodes. The covered electrode is the most popular type of filler metal used in arc welding.
The composition of the electrode covering determines the usability of the electrode, the composition of the deposited weld metal, and the specification of the electrode. The type of electrode used depends on the specific properties required in the weld deposited.
These include corrosion resistance, ductility, high tensile strength, the type of base metal to be welded, the position of the weld (flat, horizontal, vertical, or overhead), and the type of current and polarity required.
Coatings of Welding Electrodes
The coatings of welding electrodes for welding mild and low alloy steels may have from 6 to 12 ingredients, which includes:
- Cellulose to provide a gaseous shield with a reducing agent in which the disintegration of cellulose produces the gas shield surrounding the arc
- Metal carbonates to adjust the basicity of the slag and to provide a reducing atmosphere
- Titanium dioxide to help form a highly fluid but quick-freezing slag and to provide ionization for the arc
- Ferromanganese & ferrosilicon to help deoxidize the molten weld metal and supplement the manganese content and silicon content of the deposited weld metal.
- Clays & gums to provide elasticity for extruding the plastic coating material and to help provide strength to the coating
- Calcium fluoride to provide shielding gas to protect the arc, adjust the basicity of the slag, and provide fluidity and solubility of the metal oxides
- Mineral silicates to provide slag and give strength to the electrode covering
- Alloying metals including nickel, molybdenum, and chromium – to provide alloy content to the deposited weld metal
- Iron or manganese oxide to adjust the slag’s fluidity and properties and help stabilize the arc.
- Iron powder to increase productivity by providing extra metal to be deposited in the weld.
types of welding electrodes
The rods used for MIG and stick welding are examples of consumable electrodes. They have filler material, which melts to create weld joints.
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.
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 similarity 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.
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.
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 towards 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.
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.
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.
Storage of Electrodes
Electrodes must be kept dry. Moisture destroys the desirable characteristics of the coating and may cause excessive spattering and lead to porosity and cracks in the formation of the welded area. Electrodes exposed to damp air for more than two or three hours should be dried by heating in a suitable oven (fig 5-32) for two hours at 500°F (260°C).
After they have dried, they should be stored in a moisture-proof container. Bending the electrode can cause the coating to break loose from the core wire. Electrodes should not be used if the core wire is exposed.
Electrodes that have an “R” suffix in the AWS classification have a higher moisture resistance.
Electrode Defects & Their Effects
If certain elements or oxides are present in electrode coatings, the arc stability will be affected. In bare electrodes, the composition and uniformity of the wire is an important factor in the control of arc stability. Thin or heavy coatings on the electrodes will riot completely remove the effects of defective wire.
Aluminum or aluminum oxide (even when present in 0.01 percent), silicon, silicon dioxide, and iron sulfate are unstable. Iron oxide, manganese oxide, calcium oxide, and stabilize the arc.
When phosphorus or sulfur is present in the electrode more than 0.04 percent, they will impair the weld metal because they are transferred from the electrode to the molten metal with very little loss. Phosphorus causes grain growth, brittleness, and “cold shortness” (i. e., brittle when below red heat) in the weld.
These defects increase in magnitude as the carbon content of the steel increases. The sulfur acts as a slag, breaks up the soundness of the weld metal, and causes “hot shortness” (i. e., brittle when above red heat). Sulfur is particularly harmful to bare low-carbon steel electrodes with a low manganese content. Manganese promotes the formation of sound welds.
If the heat treatment, given the wire core of an electrode, is not uniform, the electrode will produce welds inferior to those produced with an electrode of the same composition that has been properly heat treated.