Handouts for basic Welding Terminologies and Definitions

Listed below are the basic welding terminologies and their detailed definitions, sorted in alphabetical order for the ease of your search about the concerning content.

A number

The designation number used for analysis of deposit weld metal. It provides a better understanding of weld materials type and their elemental study.

Air Carbon Arc Gouging

The process of cutting of metal by melting it with the heat of carbon arc and removing it by the thrust of air. In steel welding industries gouging is carried out with the help of air carbon arc cutting process. A special kind of equipment is applied to serve the joint preparation and sometimes for the removal of undesired metal for example: back gouging etc.  


 A material composed of two or more than two elements (metals and non-metals). An alloy material exhibits the properties of a metal, because it is necessary that an alloy must have at least one metal in its composition. For this an alloying material is added to a metal, in order to improve its service (mechanical) properties. Examples are the steels (iron alloy), brass (copper alloy) etc.

Alternating Current

An alternating current is characterized by its cyclic reverses of direction at specific regular intervals, forming a sine wave. In welding both alternating and direct current are used, depending on the type of welding procedures. Normally an alternating current creates arc problems, making it unstable but recent advancements in welding power supply has made it possible to produce good results.   


Liquid solution having the combination of chemicals like emulsifiers and corrosion inhibitors, which are employed on parts to be welded by spraying action, in order to prevent spattering during the process. They are easily washable after working. Now a days many anti-spatter sprays are available which are not only environment friendly but also have no adverse effects on welding operations.

Arc Blow

During welding some sort of magnetism causes an arc to change its direction, turning it out of the way from its track.

Arc Length

The extent of an arc from its one end (electrode) to the other end (weld). It depends on the distance between the electrode and work piece. If the torch or gun is kept nearer to the work metal, an arc gets shorter. On the other hand keeping the distance larger, makes an arc longer as compared to the former case.


Type of steel, having a face centered cubic crystal structure. The steel has austenitic phase in its structure because during its production heating is applied above the critical temperature line to dissolve all the carbides and elements into a single phase. Having this phase the material acts as a non-magnetic in nature. Austenitic stainless steels are the most common weld-able materials used in steel welding industries.

Back Fire

The process of flame receding into the welding gun. It is a short term aflame and soon tends to terminate.

Back Gouging

The process of scratching and excavation of parent metal and weldment from the side opposite to the weld deposit in order to assist good penetration for next weld pass at the gouged side.

Backhand Welding Technique

Type of welding technique in which the welding torch comes ahead of the welding rod. In this case, the feeding welding rod is positioned between the molten weld and flame, making an angle with welded portion.

Base Metal

The metals which are cut and joined by welding or employed to any other fabrication process for commercial and industrial use. Base metals have kind of a lower defensive character as compared to noble metals that is why they tend to be oxidized or corrode easily. Well there comes another definitions for a base metal. In welding, the metal which is to be cut and welded is referred to as base metal. Also in surface treatment applications, the metal under the coating/surface prepared is called as base metal. In terms of an alloy, the metal of main constituent in the composition is also referred to as a base metal.   

Butt joint

The weld joint where both work metals are joined, lying in the same line horizontally. As the name expresses, sides of flat work pieces are headed up with each other and weld is laid on upper surface of joint line.

Cap pass

The raised portion of weld, made by the last weld pass to end/terminate the welding procedure. The last weld pass is termed as cap pass.


The application of material layer on the work metal, to provide protection against atmosphere, oxidation, corrosion and wear. For example in welding industries, it is a common practice to clad the inexpensive carbon steel with the layer of stainless steel. The technique offers so many advantages and benefits by reducing the cost and can be applied by using arc welding processes; submerged arc welding, gas tungsten arc welding, plasma transferred arc welding, flux cored arc welding etc. The cladded layer on weld is also termed as ‘weld overlay’.

Cold Lap

In welding, cold lapping is characterized by partial or incomplete overlapping between the weld metal and parent metal and may induce small cracks. The main cause of cold lap, is incomplete fusion of a cold weld when made to a thick base metal. 

 Corner joint

Type of a fillet weld joint, where the work pieces are aligned perpendicularly making a shape of ‘L’. In this case, the weld is laid at the corner (meeting sides of work pieces) that is why it is referred to as corner joint.

Crater Crack

The cavity produced due to burning at the end of weld pass. It looks like an indentation on the weld surface.


The fabrication and behavior of a material concerns with lower temperature usually below minus one hundred and fifty (-150) degrees Celsius. It deals with study of behavioral characteristics of weld-able materials at extremely low temperature and implies it in their fabrication and production. Cryogenic applications involve the storage vessels for liquefied gases like nitrogen and helium.

Deposition Rate

The amount of weld metal deposited in a specific period of time. The units for deposition rate are kilogram per hour. In welding, another term is also used to express ‘the ratio of amount of weld metal deposited on the joint to the net amount of consumable used’, referred to as deposition efficiency.     


The process of changing the composition of consumable material in a weld bead due to blending of filler metal either with parent metal or with previously deposited weld metal. In welding, dilution is calculated by measuring the amount of parent metal or weld metal from previous weld bead.

Direct Current

The current having a unidirectional flow. Direct current mode is easiest to use and commonly preferred by most welders, for it does not cause severe weld spatter and no other consequent weld defects. In welding there are two electrode connections; direct current electrode positive and direct current electrode negative.

Direct Current Electrode Negative

When the work piece is attached to positive pole and the welding electrode is connected to negative pole of power supply, the electric current flows from the welding electrode. Such type of connection is termed as direct current electrode negative, (shortened form DCEN) in arc welding. This produce less amount of heat as compared to DCEP, therefore best suited for welding of thinner sections.

Direct Current Electrode Positive  

When the welding electrode is attached to the positive pole and work piece is connected to negative pole of power supply, the current flows into the electrode therefore producing high heat input. In arc welding such connection is referred to as direct current electrode positive and its shortened form is termed as DCEP.

Electro Slag Welding

Type of an arc welding process in which the feeding filler metal is heated and melted due to the electrical resistance offered by a molten slag. The process involves the use of electric arc and an additional flux that is why it is termed as electro slag welding. An arc is initiated from the filler wire which is used to heat and melt the feeding flux converted into a molten slag. There comes a point when the molten slag comes in contact with the wire tip, due to which the arc tends to be terminated. Due to the electrical resistance in molten slag, high heat is produced that helps to melt the feeding wire straight into the weld joint. Electro slag welding is primarily applied to weld thicker parts and sections in vertical position, merely in a single pass and in shortened from it is referred to as ESW.


A welding electrode acts like a conductor and is used to conduct electric current in the work metal in order to join the work pieces together. An arc is produced between an electrode and work piece that produces considerable heat to melt and fuse the work pieces. On the basis of consumption, it is classified in two sub-categories; consumable and non-consumable. Former not only produces an arc but also gets filled in the weld joint. Later is only used to produce arc and melt additionally added filler rods.  They are available in different shapes, size and composition. Common shapes are rods, sticks and continuous wires. 

Electrode Extension

The extension of electrode wire, out from the electrode holder. It is defined as the portion of welding electrode/wire that extends out from the contact point of a gun.  In arc welding, another term used for electrode extension is ‘electrode stick out’. It is an important factor to deal with the heating of electrode wire. Say if the wire is kept less extended, less heat will be produced therefore decreasing the deposition rate. But less stick out gives higher penetration results. On the other hand if the extension is kept higher, more heat will be produced giving higher deposition rates but in doing so shallow penetration results are obtained.

Electron Beam Welding

EBW stands for electron beam welding in which a high speed electron beam is allowed to concentrate on the work pieces to fuse them together. In this technique the kinetic energy of fast electrons on striking with the work metal, is converted into heat energy. This heat energy in turn helps to melt and blend the metal pieces together. The process involves the acceleration of electrons that can be made possible in the presence of vacuum. An electron beam welding equipment is specially designed in which the electron beam is monitored in vacuum with the help of electric and magnetic field generators.   

F number

The number used for the specification, welding characteristics and material type of electrodes. It indicates the electrode type (covering, material, flux) and welding properties (current, voltage, and penetration).

Filler Metal

An additional metal that is melted and fed to fill a joint between the work pieces. A filler metal adds up the material that fuses with both joint pieces.  

Fillet Weld

Joining of work pieces which are orthogonal (at 90 degrees) to each other. Fillet welding includes three types of joints; tee, corner and lap.  The weld looks like a triangle in shape with the facing side flat, convex or concave. Fillet weld are most commonly used joining method and offer less cost in steel fabrication industries.


The material used to clean the weld from unfair oxides and material in the form of slag and consequently the slag acts as a protective coating over the weld.  Also a flux on melting in the heat of arc, produces a gas shield against atmospheric pollutants.  

Flux core arc welding

Modified variation in metal inert gas welding which uses continuously feeding flux core electrode wires. As the name expresses, the wire has a flux inside the core of metal, which not only protects the weld pool by slag formation but also provides gas shielding. Same equipment is used for both MIG and FCAW processes, the only difference is the use of electrode wire type either the metallic wire or a flux cored wire. Flux core arc welding also classified into two subcategories on the basis of shielding type; Self Shielding (production of gases by the inside flux) and dual shielding (by the use of additional gas supply). The process also has close resemblance with shield metal arc welding because the flux has same constituents as in stick electrodes.

Flux core TIG filler rod

Filler rods having a flux in core, are employed to tungsten inert gas welding of three hundred (300) series of stainless steel and dissimilar metals, primarily to eliminate purging process. Their intended use is to produce quality welds in all positions and especially root pass without high-price purging methods.

Forehand Welding Technique

Type of welding technique in which the welding rod comes ahead of the welding torch, making an angle with un-weld portion. In this case the welding flame is directed between the rod and molten weld pool.  

Friction Welding

The type of welding that does not involve the melting of work metal that is why it is referred to as solid state welding. In this process one part is allowed to rotate against the surface of a fixed part. The friction offered by the sliding surfaces, helps to produce heat. This in conjunction with the applied force on lateral sides cause to deform contact surface plastically and blend the parts together.


The joining and blending of two pieces of metal or the base metal with filler metal by melting during the welding process.

Globular Transfer

Type of a metal transfer mode in GMAW in which globule like molten droplets are formed at the tip of electrode wire due to high heat produced. These molten droplets disengage and tend to separate from the electrode and fill the weld pool due to short circuiting or gravity. The technique costs less and often uses carbon dioxide as shielding gas but on the detrimental side it causes undesirable spatter, residual stress level and rough weld surface. As the separation of globule like droplets is caused by gravity, the mode is only employed to flat and horizontal positions.  


The process of wearing the uneven work piece surface, in order to make it smooth and clean. In weld fabrication industries several kinds of grinders are applied on work metal to facilitate the welding process.

Groove Weld

Type of joining by filling the weld metal in the groove (opening) between the pieces. For this beveling is process to make space where the weld metal is filled to provide complete penetration. Groove weld is applied on high strength welds and is most common practice in pressure equipment fabrication industries. Depends upon the beveling, groove weld mostly referred to various joint shapes; U bevel, J bevel, V bevel, double bevel.   

Heat Affected Zone

The part of parent metal next to the weld metal, is affected by the heating and cooling cycle during welding and is normally termed as Heat Affected Zone. Due to unfair cooling, the affected part is subjected to variation in micro-structure and mechanical properties.  

J groove weld joint

Type of a joint for groove welding, having a gap in shape of alphabetic letter ‘J’ between the two work pieces. In this case, one metal piece has flat edge while the other one has concave appearance.

Joint Preparation

This includes the beveling of parent metals to produce groove for the weld metal to be filled. In steel fabrication industries, edge preparation is done by cutting, grinding and machining.

Lap joint

Type of a fillet weld joint, where the work pieces overlap each other making a right angle at the edges.


The size of a fillet weld is determined by a factor, termed as Leg. It is a distance measured from weld root to the toe.  

MIG Welding

Type of an arc welding process, where heat is produced due to an arc formed between electrode wire and work metal. The heat produced as a result helps to melt both the wire and work metal, render them to join. In this technique the electrode wire uncoils from a spool and allow to feed through a welding gun. Within the same gun, a supply of shielding gas is allowed along with electrode wire, to avoid any entrapment of surrounding contaminants. Base on the type of shielding, the process is classified in two categories; Metal Inert Gas (when the inert gases like argon, helium are used) and Metal Active Gas (when mixture of gases like carbon dioxide, argon, oxygen in particular composition are employed). Common names are Metal Inert Gas referred to as MIG, Metal Active Gas referred to as MAG and Gas Metal Arc Welding referred to as GMAW. The process is used to weld steel family and non-ferrous metals like Aluminum.

P number

The designation number of weld-able materials assigned by American Society of Mechanical Engineers. The number describes the specifications, mechanical and welding characteristics of materials. Another designation number, referred to as ‘S’ number also used for some materials.

Parent Metal

In welding industries, the pieces of metal (weld-able steels) that are joined by welding or brazing. The term parent metal is also referred to as ‘base metal’ and ‘weld-able metal’.

Partial Joint Penetration

Not complete penetration of weld metal into the joint, which is made deliberately.


It is a measure of depth to which the weld metal penetrates from open joint surface. Penetration is an important point of consideration in Weld Inspection.

Post Weld Heat Treatment

As the name states, the controlled heat treatment of a welded material next to the welding is referred to as post weld heat treatment. The intended purpose of PWHT is to minimize/relief residual stresses and to soften the hardened weld material in order to prevent cracking during service. This practice is commonly exercised in steel welding fabrication industries.  

Pulsed Spray Transfer

It is a modified form of spray transfer mode, using current pulses to allow the transfer of tiny molten droplets through stable arc. For this, specially designed power sources are used to produce current in pulses with specific frequency.  As the current settings and heat input are lower, the process can be employed to weld thinner material. The weld pool area is not too big due to lower heat input, render it to be practicable in all positions. Now a days, pulsed spray transfer is applied to a variety of ferrous and non-ferrous materials and gives quality weld results.

Root Face

The flat or unbeveled part of beveled edges of parent metal at the joint root. For groove welding, joint is prepared by beveling. The portion at the root of joint is left flat which is termed as root face.  

Root Opening

It is referred to as the space between the edges of beveled parent metals at joint root. It is an important joint consideration for effective root welding results.

Shield Metal Arc Welding

One of the most commonly used arc welding procedure throughout the world. The procedure uses flux coated electrodes which is heated and fed due to an arc formation between the consumable electrode and work piece. The coated flux not only produce a protective slag but also provides shielding due to the formation of gases. Common names are; Manual Metal Arc Welding referred to as MMA, stick welding and flux shield arc welding referred to as FSAW. It has been the most popular arc welding process in Steel fabrication industries.

Short Circuiting

Type of transfer mode in gas metal arc welding by using lower current settings, to produce lower heat as compared to globular transfer. Due to which molten droplets instead of falling into the weld pool, prefer to make a gap between pool and electrode wire and consequently short circuit occurs. As a result a series of alternating extinguishes and reigniting takes place at a rate of hundred (100) cycles per second. This occurs so rapidly that the arc looks continuous to an observer. SCT stands for short circuit transfer, provides better weld surface with minimal spatter allowing it to apply for all positions. But on the detrimental side due to lower current and heat, this mode may not give sound results in thicker material. Lower heat and fast cooling may impart lack of fusion and penetration problems in weldment. 


The fused coating over weld due to the burning of flux used in welding process. The slag coating provides protection and facilitate cooling of weld. It must be removed either by chipping or brushing before the next weld pass.

Slag Inclusion

Type of a weld imperfection when the particles of solid slag are entrapped in the weldment or between the parent metal and weld metal, leaving the weak zones in the weld. This occurs when no proper slag removal and weld cleaning is exercised.

Spray Transfer

Type of metal transfer in gas metal arc welding in which tiny molten droplets from electrode wire are fed to weld pool mainly in the form of spray due to higher current and heat supply. This mode is used in higher weld deposition applications with minimal spatter. As the weld pool area tends to be bigger due to higher heat input, it is primarily employed to weld thicker material. Although reduce spatter and higher deposition rate are the benefits but on the other hand this mode is only recommended to flat position.

Submerged Arc Welding

An arc welding process in which arc and the weld pool is submerged under the thick layer of granular flux. Normally the flux used, (consists of lime, calcium fluoride, manganese oxide and silicon dioxide) on melting plays several important roles during welding. The flux has tremendous ability to act as a conductor and provides a conductive path between an electrode and work piece. Apart from slag making, it gives off shielding gases that provides protection to the weld zone from atmospheric pollution and in this way no additional gas supply is required. Similar to Metal inert gas welding, SAW also involves the continuous feeding of electrode wire. In this process flux overlay prevents the weld spatter and envelops the intense fumes and sharp light.

Tee joint

Type of a fillet weld joint, where the work pieces are perpendicular to each other making a right angle between the sides. As the name states, the joint assembly looks like a tee.


In fillet weld there are two strength consideration factors
Actual Throat – it is defined as the length/distance from weld root directed to the center of curved weld face. In other words, it is the length of actual fillet weld.
Theoretical Throat – Consider a right triangle inside the fillet weld. The distance determined from the weld root directed in a straight line perpendicular to the hypotenuse of that triangle.  

TIG Welding

Type of an arc welding where high melting tungsten/tungsten alloy electrode is employed to burn the feeding filler wire to deposit the weld. The welding procedure is known as Tungsten Inert Gas Welding because an inert gas argon, helium or their mixed combination is used as shielding against surrounding contaminants. It is primarily applied to weld steel family, aluminum, coper and magnesium alloys.

Travel Speed

In easy sense, it is defined as ‘How fast a weld deposit is laid’. It is a rate at which weld covers a certain distance/length. Fast travel means, weld covers a long length in short time while on the other hand slow travel means, weld covers same length within long duration of time. Travel speed if determined by measuring the time by using stop watch and the length of weld deposit.


An undesired depression due to melting of parent metal usually occurs at the weld toe and root. This makes a weak weld due to incomplete blending.

V groove weld joint

Type of a joint for groove welding, having a gap in shape of alphabetic letter ‘V’ between the two work pieces. A joint having V groove on both upper and lower side is referred to as double V bevel.

Weld Bead

A part of metal melted and deposited to the joint in one pass. A weld bead is also termed as weld layer.

Weld Pass

Deposition of weld metal to the joint in single move. The welding involves more than one pass is referred to as multi-pass welding.

Weld Toe

The portion between the exposed weld face and parent metal. It is defined as the joining line of weld metal of exposed surface with the parent metal.


The process of joining materials through fusion by applying heat, resistance or pressure. Based on joining techniques, welding is characterized into many types; Arc welding, Resistance Welding, Laser Welding, Electron Beam Welding, Gas Welding etc.

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