Welding 101: Everything You Need to Know about Electrodes -
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Welding 101: Everything You Need to Know about Electrodes


Welding 101: Everything You Need to Know about Electrodes

Different types of welding, different equipment. But common to all of them is the welder rod or electrode. This is the metallic rod or wire that is used to create the bond between two metals. There are dozens of types of electrodes, each used with specific metals and in different welding types. Knowing which to choose will also determine the overall strength and finish of the weld.

Types of Electrodes

Types of Electrodes
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Electrodes can be divided into two basic types – consumable and non-consumable. This means that when creating the arc that fuses the base metals, the electrode material is consumed and forms part of the weld. Non-consumable electrodes have a higher melting temperature than the base metals and as a result, do not melt into the weld. Consumable welder electrodes are used in arc and MIG welding, whereas TIG welders use non-consumable electrodes. Choosing the right electrode then depends on the welding process involved.

Consumable Electrodes

Consumable Electrodes
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Consumable electrodes are the most common type of electrodes. These form part of the weld and melt into the fused metals during welding. Consumable rods in different sizes and with or without coatings are used by stick and arc welders. MIG welders use a consumable wire that is fed through the welding gun by the welding machine.

Welders use two types of electrodes in arc welding – bare electrodes and coated electrodes. Bare electrodes don’t have a flux coating, so are limited in their application. They are mainly used in welding wrought iron or manganese steel. Coated electrodes, on the other hand, can have a light flux coating, medium coating, or as is often the case a heavy flux coating. The flux coating acts as a shielding agent and prevents the base metals from oxidizing and contamination.

Light-coated electrodes are used mainly to stabilize the electrical arc and protect from oxides. The resultant weld has little to no slag. Medium coated electrodes, typically with a low-hydrogen content, are used to avoid cracks from forming in the weld. These are found in heavy-duty applications, like welding thicker sheet metals, welds in bridges and buildings, and pipeline construction. Heavy coated electrodes offer the best shielding properties and allow for quicker welding. The coating can consist of a cellulose layer, mineral layer, or both. Mineral coated electrodes produce more slag which helps create a protective layer as the metals cool. Heavy coated welder electrodes are used in welding different types of steel and iron and in creating dense layers of resistant materials between parent metals in what is known as hard surfacing.

Non-consumable Electrodes

Non-consumable Electrodes
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These come in two types – carbon and tungsten. Carbon electrodes consist of graphite and are used mainly for cutting purposes resulting from high temperatures. More common are tungsten electrodes. These are used in TIG welding. The electrodes can consist of pure tungsten and colored with a green tip, with traces of thorium and colored yellow or red, and with zirconium and colored brown. Thoriated tungsten electrodes offer better arc stability, can be operated at higher amperages, and leave the least amount of contamination. They are typically used for welding aluminum, stainless steel, copper alloys, nickel alloys, and titanium alloys.

Electrode Classification

Classification charts exist to help welders get the right electrodes for the application at hand. These consist of letters and numbers. Numbering informs welders of the type of coating in welding rods, the optimal position the rod can be used, whether AC or DC current is preferred for creating the arc, how deep the rod penetrates into the weld pool, and the rated tensile strength of the materials and the finished weld.

6011 Arc rods, for instance, tell welders that this rod has a tensile strength of 60000 pounds per square inch (first two digits), that it can be used in all welding positions (third digit) and the last digit informs of the type of coating and the current to be used. Another widely used welding rod, the 7018 electrode tells us that it can withstand 70000 pounds of pressure per square inch, that it too is suitable in all welding positions, and has a low-hydrogen, iron powder flux coating meaning it can be used with both AC and DC current. The difference between these two electrodes is that the 6011 electrode is a general-purpose rod used for welding most kinds of iron and mild steel, penetrates deep into the weld, and leaves little contamination. The 7018 rods, on the other hand, are used for smoother structural welds in high-tensile carbon steel. It doesn’t penetrate as deep but leaves more slag. Classification systems help differentiate between the various types of electrodes, where and how they are used, and the strength and finish of the weld.

Factors to Consider When Buying Electrodes

The information in electrode charts confirms the base metals that these can be used with, how strong the weld will be, and the type of welding machine required in order to produce different currents and different polarities. In addition, charts tell welders the thickness of the base metals and how deep electrodes can penetrate, all the possible positions (horizontal, vertical, flat, and overhead) the electrode can be used, and whether environmental factors will affect the quality and finish of the weld. If you’re confused as to which electrode to use for your next welding project, consult knowledgeable staff at welding shops for the most informed advice.

Ian Tompson