Electrode consists of a wire made of metal core, it comes with insulated wiring. In metal arc welding, electrodes are made of carbon and metal. On the other hand, in automatic welding, there are electrodes that use bare wire. There are different types of welding electrodes designed for different purpose of works. Electrodes made of metal, such as a mild steel electrode, are most common.
There are 3 types of metal electrodes:
This type of electrode has very limited usage. In bare electrodes, metals are exposed to oxygen and nitrogen when passing through the electrode. It decreases the strength of the metal. A bar wire is not a preferable option as its application makes it difficult to control the arc. As a result, metal turns into vapour.
Ammonia, Manganese Dioxide, Silica, Dolomite, Clay, Sodium Silicate, and Calcium Carbide are mainly used as the material in the electrode coating. All these are deoxidizing agents. The coating applied plays a key role in the determination of the resultant metal’s strength.
Heavy Coated Electrode
Also known as shielded arc electrodes, this type of electrode is basically used to obtain metals of supreme quality with superior mechanical properties. As a result, when it comes to strength, durability, or malleability, heavy-coated electrodes are second to none. This type of material has a plethora of applications.
Mild steel electrode is the most common coating used for coated electrodes. Other types of coating include cast iron, stainless steel weld, and Inconel electrode.
Why Coating of an Electrode is really important?
Electrode coating is basically the material which is applied around a wire to steady the arc. It also improves the chemical properties of the welded metal. Ammonia, Clay, Borux, Ferro-silicon, Sodium Silicate, Feldspar, Dolomite, Potassium Silicate, Silica, Manganese Dioxide, Cellulose, Ferro-manganese, Iron Oxide, Iron Powder are some of the most popular material in electrode coating.
More often than not, the quality of an electrode is determined by its coating. There are many reasons why which are as follows:
- The coating plays a key role in the maintenance of the arc.
- It also protects the molten metal from exposure to oxygen and nitrogen present in the air by producing a shield of gas in the welding pool.
- It also reduces the rate of cooling by providing a blanket on the weld.
- It also assists in seamless introduction of new alloying materials which are not present in the core wire.
Classification of Electrodes
As already discussed, there are different types of electrodes available in the market. Electrodes are classified on the basis of PREFIX and SUFFIX letters.
- Prefix letters consist of letters like ‘A’ and ‘M’. Semi-automatic or automatic welding is determined by the letter ‘A’ and metal arc welding is denoted by the letter ‘M’.
- Suffix letters consist of letters such as ‘H’, ‘K’, ‘P’, and ‘T’.
- The letter ‘H’ denotes Hydrogen Control.
- The letter ‘T’ denotes Iron powder covering which gives a metal recovery range of about 110 – 130%.
- The letter ‘K’ denotes Iron powder covering which gives a metal recovery range more than 130%.
- The letter ‘P’ denotes deep penetration.
So the next time you go to buy a mild steel electrode, pay attention to the letters in the electrode name to better understand its capabilities.