Welder standing over workpiece

Welding terminologies can seem broad and confusing even to those with several years of welding experience. If you are interested in welding or a career in orbital welding, it is important to know the basics. We are here to help. 

Although technicalities across manual welding and orbital welding may differ, most terminologies are shared. This post will serve as a glossary of welding terms where we examine commonly used nomenclatures in orbital welding.  

Common Glossary of Welding Terms

Alternating current (AC) welding: The welding process where the direction of current reverses frequently. A 60 Hertz (Hz) current changes polarity 120 times every second. 

Arc length: The distance from the electrode tip to the weld point of the workpiece. 

Arc voltage: The voltage of the welding arc between the end of the wire and the workpiece.

Arc voltage control: The device used to control the voltage and maintain the precise arc length during the automated welding process. 

Arc welding: The welding process where workpieces are joined together using heat generated from an electric arc.

Arc welding electrode: The length of wire through which the current passes to create an electric arc.

Autogenous welding: The fusion welding method that does not require the addition of filler metal from an external source.

Automated welding: The process of welding using equipment and controls that do not require direct and continuous handling from a welding operator. 

Base metal: The metal that is being welded.

Bevel: An angular surface at the end of the metal to be welded.

Bevel angle: The angle at which the plate is prepared for welding. The standard bevel angle for pipe welding is 37.5 degrees.

Cladding: The process of depositing materials to form a new surface on the workpiece to improve the properties like corrosion resistance or heat resistance.

Cold working: The process of improving the properties of the metal without any application of heat to shape and size them below the re-crystallization temperature.  

Complete fusion:  The fusion is done in the entirety of the base metal surface or the different layers intended for welding. 

Cryogenic welding: The welding process performed for metals operating at the cryogenic temperature. The cryogenic temperature may be as low as -400F, which is required to ensure liquefaction of gases. 

Deposition rate: The speed at which the filler metal is deposited into the weld.

Depth of fusion: The distance from the weld surface to the point in the base metal from where the fusion extends. 

Direct current (DC) welding: The welding process where the polarity of the current remains constant. DC welding produces a more stable arc. 

Distortion: A weld defect occurring in the base metal due to an uneven heating and cooling cycle that causes expansion or contraction of the workpiece. 

Electrode: The metallic wire or rod that transmits electric current to produce an arc. 

Feed speed: The rate at which the filler wire is consumed while welding.

Filler metal: The metal deposited during the welding process. 

Filler wire: The filler metal in the form of a wire to be added during the fusion.

Flux: The material used in welding that acts as the agent to dissolve oxides, release trapped gases, remove slags, and ensure clean weld results by removing impurities. 

Flux-cored arc welding (FCAW): A mechanized arc welding process where a flux wire is continuously fed and a DC current is supplied to fuse the metals. 

Fusion zone: The base metal area that has been melted to aid in the joint formation.

Gas metal arc welding (GMAW): A type of arc welding process where a consumable electrode is used to produce an arc. This is also known as Metal Inert Gas (MIG) welding.

Gas tungsten arc welding (GTAW): A type of arc welding process that uses non-consumable electrodes and shielding inert gas to create a weld. The weld produced is generally clean and of high quality. The use of filler metal is optional depending on the application. This is also known as Tungsten Inert Gas (TIG) welding.

Heat affected zone (HAZ): The area of the base metal near the weld that has undergone microstructural property changes due to heat exposure. 

Hot cracking: The defect occurring during weld solidification where shrinkage can result in crack formation.

Inclusion: Slag, contaminants, and other foreign materials entrapped in the weld.

Inert gas: The gas that does not chemically react with elements to interfere with the welding process. Helium and argon are the most commonly used inert gases.

Interpass temperature: The temperature at which the weld metals are deposited in each weld pass.   

Joint preparation: The process of preparing edges or joints of the workpiece like pipes or tubes using machining, cleaning, or plating techniques. 

Lack of penetration: Weld imperfection caused when the root of the joint does not meet the root of the weld bead (i.e., the root is not completely fused).  

Orbital welding: The automated welding process, especially used for welding pipes and tubes, where the workpiece is kept static while the arc is rotated 360° around it. 

Overhead welding: The welding position taken to weld the underside of the workpiece. The risk of weld pool dripping and sagging makes the welding more difficult to perform for welders. 

Phase transformation: The changes in crystalline structure as a result of excessive heating and cooling due to the metal being exposed to elevated temperature. 

Porosity: A common weld defect where the inclusions and trapped gas during weld solidification form pockets or pores in the weld surface.   

Post weld heat treatment: The process of applying uniform heat after the welding process is completed at a temperature below the transformation range of the metal being used. This is done to release any entrapped gases, lower residual stress, and improve weld quality. 

Power source: The device used to provide electric current and voltage suitable for producing an electric arc.  

Preheating: The process of heating the entire base metal or the area around the joint to a certain temperature before the welding process so as to slow down the cooling rate, thus, reducing the hydrogen buildup in the weld area and eliminating the chances of developing cracks.

Residual stress: The stress developed in the weld metal due to non-uniform thermal expansion. 

Root: The narrowest point at the back of the weld which intersects the base metal surface.

Root cracking: The crack that originates from the root bead to the subsequent beads. As a result of shrinkage stress. 

Root pass: The initial step of the welding process where the first layer of the weld bead is placed in multi-pass welding. 

Semi-automated welding: The manual welding process where weld equipment is utilized to control one or more steps such as feed speed or gas flow rate, while the weld operators manually guide the weld torch movement. 

Shielding gas: The inert or semi-inert gases used especially during GTAW or GMAW process which form the shield around the arc to prevent the external elements, like oxygen, or inclusions from interfering with the molten weld pool. Argon and helium are the most commonly used shielding gases. 

Travel angle: The angle at which the electrode is pointed with respect to the weld surface plane that is parallel to the direction of travel. 

Tungsten electrode: The most commonly used electrode in arc welding, made out of ‘tungsten’. These are non-filler, versatile electrodes that are typically color-coded to distinguish between their various types— 2% thoriated, 1.5% lanthanated, 2% ceriated, 0.8% zirconated, and pure tungsten electrodes.  

Underbead cracking: The crack developing in the HAZ near the fusion line due to the excessive entrapment of hydrogen molecules. These are sometimes also known as cold cracking or hydrogen cracking. 

Undercut: The defect along the edge of the base metal resulting from the use of excess heat during welding. 

Welding arc: The electric discharge from the electrode to the workpiece containing high heat that is used to join metals during welding. 

Weld current: It is the amperage required to carry out a successful weld. The weld current requirement is based on the thickness of the weld metal as well as the speed at which the welding process is carried out to ensure a quality result. 

Weld head: The device used in orbital welding of pipes and tubes which can automatically rotate an electric arc along the joints to create a fusion. It is usually accompanied by a power supply and a monitoring system.

Weld pass:  A single course of travel during welding when the weld beads are laid along the joint. 

Weld procedure specification (WPS): A document containing all important directions required for welders to carry out the welding process according to the industry standards.

Weld pool/ Weld puddle: The volume of metal in the weld that is molten due to the application of heat. 

Weld reinforcement: The excess amount of weld metal when filling a weld joint. 

Enhancing Your Understanding Of Orbital Welding

Orbital welding is a complex process and its success depends on the ability of welders, technicians, and stakeholders to understand the reasoning behind each step. The above glossary of welding terms fundamental to orbital welding can act as a guide to help you understand common industry language so you do not miss any details. 

Arc Machines, Inc. is a leading welding technology provider with a range of orbital welding solutions and services to help you understand and simplify your welding process. For inquiries regarding products, or if you have questions about this glossary of welding terms, contact sales@arcmachines.com. Arc Machines looks forward to providing the expertise, equipment, and services your project needs. Contact us to learn more.

Engineering Department | Arc Machines, Inc.

The first engineers at Arc Machines were also part of NASA’s Apollo program, and we continue to hold our staff to those that level of drive and quality. Not only do we produce the best welding machines on the market, but we can also build customized machinery—tailored to your operation.

Leave a Reply