What is welding electrode?
Welding electrodes are wire lengths attached to your welding equipment in order to generate an electric arc. An arc is created when electricity passes over this wire, generating enough heat to melt and fuse metal for welding.
Consider the following factors before choosing welding electrodes:
- The electrode rod’s tensile strength should be higher than the parent metals.
- Base metal parameters, form, joint design, and welding locations all must be considered.
The most common types are:
1. Consumable Electrodes
The melting point of consumable electrodes is low. These welding electrodes are most commonly used in metal inert gas (MIG) welding. Consumable electrodes are made of materials such as mild steel and nickel steel.
The only precaution you need to consider is replacing consumable electrodes at set intervals. The primary disadvantage of using such electrodes is that they do not have a wide range of industrial uses, even though they are simple to use and manage.
Consumable electrodes are classified into the following categories:
- Bare Electrodes
- Coated Electrodes
Bare electrodes are electrodes that do not have any form of coating and are typically used in applications where a coated electrode is not required.
Coated electrodes have been classified based on the coating factor. The coating factor is the ratio of the electrode diameter to the core wire diameter.
Coated electrodes can be classified into the following sub-types:
1.Light Coated Electrodes
Electrodes having a coating factor of 1.25 are light-coated. A light coating applied to electrodes aids in the removal of contaminants like oxides and phosphorous. A light coating also helps to improve arc stability
2.Medium Coated Electrodes
Electrodes having a coating factor of 1.45 are medium-coated.
3.Heavy Coated Electrodes
These electrodes have a defined composition and a coating that is applied by extrusion and dipping, and they are available in three different forms.
Cellulose: One-third of these coatings is cellulose, with the remaining two-thirds made up of various organic components. When the materials are subjected to the welding arc, they disintegrate into three gases: hydrogen, carbon monoxide, and carbon dioxide, which all help to intensify the arc. Because of the increased strength, the current may enter the metal more deeply, leading to stronger welds.
To protect the weld pool from contaminants, cellulose coatings also generate a layer of gas. The gas layer acts as a barrier between the metal and the other components that might cause porosity in a weld, such as oxygen, nitrogen, and hydrogen. Because porosity is harmful to a weld, electrodes with cellulose coating can generate better welds
Cellulose coatings are available in a range of chemical mixes, each with its own distinct qualities and optimal uses. While the cellulose component of the formula is a basic rule of thumb, the other organic elements vary substantially.
Mineral: Mineral coatings leave a slag layer on the welded surface. While slag may seem to be an annoyance, it actually has a function. Mineral-coated electrode slag cools significantly more slowly than cellulose-coated electrode slag and the welded materials underneath.
This allows contaminants to filter towards the metal’s surface, preventing them from affecting the weld’s structure.
Mixture: Fabricators choose electrode coatings that combine cellulose and minerals because they provide the best of all worlds. The chemical variety of these coatings gives a range of important benefits since they might include anything from a few components to upwards of ten distinct chemicals.
When working with more temperamental base metals, having both shielding gas and slag protection on a weld can be extremely beneficial.
Most Common Electrode Coatings:
Since some applications require specialized electrode coatings as well as characteristics, these are the 5 most common welding electrode coatings.
The fundamental distinction between rutile and cellulose is that rutile contains more titanium dioxide. Rutile electrodes are well-suited for welding low-carbon steel because they form a gas shield comprising oxygen, nitrogen, carbon, and hydrogen.
Slag from rutile electrodes, on the other hand, has a tendency to leave traces of titanium in the metal that is deposited. The addition of cellulose to rutile electrode coatings adds to the weld pool’s protection. These electrodes emit fewer spatters and fumes and may be used in a variety of settings.
Iron Oxide Electrodes:
Iron oxide electrodes create slag that is easy to remove from the weld and can be used with both AC and DC current. This coating’s chemical composition is rich in oxygen, which might cause weld deposits that are poorer in overall strength.
However, compared to cellulose electrodes, the risk of hydrogen embrittlement is substantially reduced. Iron oxide electrodes enable precise bead placement and great arc control.
Iron Powder Electrodes:
These electrodes are modifications of existing electrode coatings made possible by adding iron powder to a mixture. Metal powders are a frequent addition to electrode coating mixes because they can help improve efficiency and overall weld quality. Cellulose power electrodes are a frequent modification to cellulose electrodes that allows for AC usage.
Taking the time to grasp the many alternatives available when dealing with a style of welding that requires separate, coated electrodes may make or break a project. When choosing an electrode, keep in mind other criteria, including location, tensile strength, and core metals.
Cellulose electrodes are ideal for vertical placement since they leave a very thin, easy-to-remove slag layer behind. When cellulose coatings are heated, they decompose, producing hydrogen and carbon dioxide. This creates an effective protective gas layer over the weld pool.
Nevertheless, the weld may be vulnerable to hydrogen embrittlement as a result of all this. Citric acid coatings function best with DC in their purest form. The addition of other components to the coating, on the other hand, may make it possible to utilize it with AC as well. Cellulose electrodes provide all of the benefits of rutile electrodes with the added benefit of deeper penetration and less slag.
These electrodes, also known as hydrogen-controlled electrodes, require a little extra attention before welding. Before using them, the electrodes must be kept dry and heated. Failure to do so could cause the coating’s chemical composition to become unstable, resulting in a weakened weld structure.
Basic electrodes deposit a small amount of hydrogen in a regulated manner, reducing the possibility of porosity and cracking in a weld. If properly stored and maintained, these electrodes are a great alternative for dealing with steel.
2. Non-Consumable Electrodes
Non-consumable electrodes are easier to understand than consumable electrodes, not only because they do not melt, but also because there are just two varieties.
Non-consumable electrodes are classified into two categories:
- Carbon or Graphite electrodes: It is primarily used in cutting and arc welding applications and is comprised of carbon and graphite.
- Tungsten electrodes: It is a non-filler metal electrode that is made mostly of tungsten, as the name implies.
These welding electrodes are not consumed throughout the welding process, or to put it another way, they do not melt while welding. However, due to the vaporization and oxidizing processes that occur during welding, the electrode length is reduced slightly. When non-consumable electrodes have a high melting point, they cannot fill the gap in the object.
Non-consumable electrodes are comprised of pure tungsten, graphite, or carbon that has been coated with copper. Carbon has a melting temperature of 3350 degrees Celsius, while tungsten has a melting point of 3422 degrees Celsius. In tungsten inert gas welding (TIG) and carbon arc welding, non-consumable electrodes are used.
Non-Consumable Electrodes Have the Following Important Characteristics:
- Shielding gases must be used when employing non-consumable electrodes. Shielding gases are inert gases that are used to protect the welding area from oxygen and the surrounding area.
- Non-consumable electrodes are typically made as cathodes, whereas workpieces are usually made as anode material.
Welding Electrode Classification
This classification depends on how to use and choose welding electrodes in a realistic way. The American Welding Society has classified electrodes into various forms to make them easier to recognize and identify.
- The letter “E” denotes an arc welding electrode.
- The first two or three digits: This number reflects the tensile strength of the deposited material in thousands of pounds per square inch when pulled apart.
- The third or fourth digit identifies the location of the weld. If 0 is selected, no categorization is applied; 1 is for all positions; 2 is for flat and horizontal positions; and 4 is for flat positions only.
- The fourth digit denotes the kind of coating as well as the type of electric power source, which is either AC or DC, with either straight or reverse polarity.
- The number E6010 denotes an electric arc rod with a stress tensile strength of 60,000 psi, adaptability to all situations, and direct current with terse polarization.
- 1 – All position
- 2 – Flat and horizontal position only
- 4- Flat, horizontal, vertical down and overhead
It is important to keep electrodes dry since moisture can ruin the characteristics of their coatings and cause excessive spatters. It may result in the formation of porosity and fractures in the welded zone. When electrodes have been exposed to a moist environment for more than 2-3 hours, it is recommended that they be dried in a suitable oven for at least 2 hours at 500 degrees F.
These should be kept in a damp-proof container after being removed from the oven. Never bend the electrode since this might break the coverings and expose the core wire. Users should not be using the electrodes with exposed wire for welding. The electrodes with the suffix “R” are more resistant to moisture.
When working with welding electrodes, you must take the following precautions:
- Keep the electrodes dry at all times.
- Moisture is highly detrimental to electrodes because it damages the electrode coating. As a result, you must keep welding electrodes in a moisture-free area as soon as they have dried. There are a variety of containers available that will keep you dry.
- Finally, never bend the electrodes because this might damage the electrode coating.