Monday, 20 May 2019

Types of Welding Electrodes

welding electrodes

An electrode is defined as a conductor through which electricity enters or leaves an object, substance or region. In arc welding, an electrode is used to conduct current through a workpiece to fuse two pieces together. There are various types of welding electrodes. This article will take a look at these different types of welding electrodes, what they are made of and their functions.

Types of Welding Electrodes

Bare Welding Electrodes: These electrodes are made of wire compositions that are required for safe applications. They have no coating other than what is required in wire drawing. The wire drawing coatings have a slight stabilizing effect on the arc, but have little use otherwise. They are commonly used in the welding of manganese steel and can also be used in other applications where a coating is not required.

Light Coated Electrodes: These types of welding electrodes have a light coating that is applied on the surface through washing, dipping, brushing, spraying, tumbling or wiping. The coatings serve to improve the characteristics of the arc stream. They have a definite composition and are classified as under the E45 electrode series.

Light coated electrodes serve a variety of functions. These include:

  •         Dissolving or reducing impurities like oxides, sulfur and phosphorus.
  •         Changing the surface tension of molten metal so that the globules of metal that leave the end of the electrode are smaller and more frequent allowing the flow of molten metal to become more uniform.
  •         Increasing stability by introducing materials that are readily ionized into the arc stream.

Shielded Arc or Heavy Coated Electrodes: These are used for welding steels, cast iron and hard surfacing. They have a definite composition and a coating this is applied by dipping or extrusion. There are the different types of these electrodes that are manufactured, classified by their various coatings which include mineral coatings, cellulose coatings and those who have a combination of the two. Cellulose coated electrodes protect the molten metal with a gaseous zone around the arc as well as the weld zone. The mineral coated electrode forms a slag deposit.

Shielded Arc or Heavy Coated Electrodes work by producing a gas shield around the arc that prevents the oxygen or nitrogen that is in the air from contaminating the metal. The electrodes also work to reduce impurities like oxides, sulfur and phosphorous that could otherwise impair the weld deposit.

Tungsten Electrodes: These are a non consumable electrode that is used in the process of gas tungsten arc welding. These electrodes are identifiable by a painted end mark as follows:

  •         Green: Pure tungsten: these types of welding electrodes are usually used on less critical welding operations than the tungstens which are alloyed. Theyhave a relatively low current carrying capacity and low resistance to contamination.
  •         Yellow: 1% thorium or Red: 2% thorium-these have a higher electron output and better arc-starting and arc stability than pure tungsten. They also have a higher current carrying capacity, longer life and greater resistance to contamination.
  •         Brown: .3-.5% zirconium-These generally fall between the pure and thorium electrodes in performance although there is some indication of better performance in certain types of welding use AC power.

Direct and Alternating Current Arc Welding Electrodes: These types of welding electrodes are used In welding that requires a power supply to create an electric arc between the electrode and the base material to melt the metals at the welding point. Direct current electrodes are designed for reverse and straight polarity. It is preferred for many types of covered, nonferrous, bare and alloy steel electrodes.

Alternating current is preferred for welding in restricted areas or when using high currents required for thick sections because it reduces arc blow. It is used in atomic hydrogen welding and in carbon arc processes that require the use of two carbon electrodes. It permits a uniform rate of welding and electrode consumption.

Carbon Electrodes: Carbon electrodes are used in carbon arc welding, twin carbon arc welding, carbon cutting and air carbon arc cutting and gouging. Those that are using this sort of welding should consult the military specification entitled “Electrodes Cutting and Welding Carbon – Graphite Uncoated and Copper Coated” which provides a classification system and other information involving the requirements for this type of electrode welding.

Stick Electrodes: Stick electrodes are used in stick welding which is a manual arc welding process that uses a consumable electrode covered with a flux to lay the weld. Stick electrodes vary by size, material, strength, welding position, soft arc designation and iron powder mix. These properties make the different types of electrodes suitable for different applications.

It’s a good idea to learn about different types of welding electrodes. Welding is an important part of manufacturing. Anyone who plans to weld professionally should learn more about this process as well as which electrodes are used in the various applications.