Welding electrodes can be defined as a piece of wire or rod that is used to join two metal items together during the welding process. By connecting the welding electrode to the welding machine, a welding current is carried and an electric arc is established, fusing the metals for joining. It is also possible, in some cases, for the electrode itself to serve as the filler material during the joining procedure. There are various types of electrodes used in the welding process.
There are a number of factors that should be considered when selecting an electrode for welding, including the type of metal to be welded, the composition of the metal to be welded, the welding position, and the design of the joint. Listed below are various types of electrodes used in welding.
Types of Electrodes in Welding
There are two types of welding electrodes i.e., consumable electrodes and non-consumable electrodes. Below is a classification of electrodes that are used in arc welding.
Non-Consumable Electrodes
A non-consumable electrode is one that is not consumed during the welding process, i.e. one that is not melted away by arc heat or fused on the weld bead during the welding process. Electrodes of this type have a high melting point and serve as electrodes for the establishment of an electric arc. In general, non-consumable electrodes can be used for a much longer period of time since it does not form a part of the weld bead.
A welding electrode’s material does not depend on the base metal to be welded, while consumable electrodes consider this factor. There are several types of non-consumable electrodes on the market today. They are usually made out of carbon, graphite, or tungsten. There are a number of welding methods that utilize non-consumable electrodes, including atomic hydrogen welding, carbon arc welding, tungsten inert gas welding, etc.
Consumable Electrodes
Consumable electrodes are those which melt due to the heat generated by the arc and are fused into the weld bond. To put it another way, these electrodes are consumed while the welding process takes place, and they are then deposited on the weld bead as a result. Consumable electrodes are characterized by their low melting points, allowing the arc to melt both metal pieces and the tip of the electrode, which acts as a filler material.
The consumable electrodes used for welding vary according to the composition of the metals to be joined. Typically, consumable electrodes are manufactured from low alloy steel or nickel steel with a diameter between 2mm and 8mm and a length between 200mm and 500mm. Again, these electrodes are distinguished by the type of flux coating they are coated with.
There are two types of consumable electrodes and these can be categorized as follows:
- Bare Electrodes
- Coated Electrodes
1. Bare Electrodes
There is no flux coating on these electrodes. Automatic and semiautomatic welding often utilizes these electrodes. These electrodes are plain, which causes the metal globules to be transferred from the electrode to the work, where they come into contact with oxygen and nitrogen.
A number of nonmetallic constituents are formed as a result of this process, and they are trapped in the solidifying weld metal. Therefore, the material’s strength and ductility are reduced. The use of bare electrodes is appropriate for welding at lower voltages.
In accordance with their size, these electrodes can use currents ranging from 160 to 310 amperes. When the electrode is connected to the negative terminal of a DC supply, it is possible to weld satisfactorily with bare electrodes.
2. Coated Electrodes
There are two types of coated electrodes and these can be categorized as follows:
- Lightly Coated Electrodes
- Heavily Coated Electrodes
Lightly Coated Electrodes
This is an improved version of the bare electrode in which a thin layer of coating is present which is about several tenths of a millimeter thick. Lime is mixed with soluble glass to form a coating that serves as a binder. A light coating is mainly used to increase the stability of the arc, which is the main purpose of the coating. Therefore, this coating is also referred to as stabilized coating.
An electrode of this type is better suited to protecting welds from oxidation. They offer a number of advantages over bare electrodes. The welding voltage and current required by these electrodes are higher than those required by bare electrodes. For welding non-essential tasks, these types of electrodes are used.
Heavily Coated Electrodes
As the name implies, heavily coated electrodes have a thick layer of coating. Asbestos clay, calcium carbonate, titanium oxide, ferromanganese, silica, flour, titanium oxide, and ferromanganese are common coating materials of heavily coated electrodes. Generally, these electrodes are used in order to obtain a high-quality weld metal by preventing oxide and nitride formation.
Advantages of coated electrodes
Coated electrodes have the following advantages in welding:
1. Because the electrodes are coated with materials that stabilize arcs like Na, CaCO3, Ti, and K, the arc produced by the electrodes is stabilized.
2. Using these electrodes will increase the melting rate, which will result in a faster welding process.
3. An electrode is coated to protect it from contamination caused by atmospheric conditions.
4. A welding process involves the removal of any impurities present on the metal surface being welded.
5. With an ac supply, the coated electrode has the advantage of keeping arc spacing ionized even at zero current. By creating covering gases around the arc and surrounding the arc, the coated electrode can overcome the tendency to deionize the arc at zero current instant.
6. Coatings provide insulating properties to the electrodes when they are exposed to the outside environment. Therefore, these electrodes are capable of handling high currents.
7. When welding with these electrodes, metal spattering is prevented.
8. It is very easy to weld overhead and vertically with these electrodes.
