Welding Terms and Definitions

As Greenville, South Carolina’s premier welding company we at Greenville Weld Company feel obligated to teach you how to speak welder. It is specialized language derived from decades of being kept in the dark, behind the lens, staring at bright blue lights. Please enjoy:

General Welding Terms

Base Metal
The primary or main piece of metal or material being welded or fabricated.

Bead
The weld metal deposited during the welding process. In pipelining, this also refers to the first pass of a pipeline weld.

Butt Joint
A joint where two pieces of metal are joined along their edges, common in pipe welding and some structural scenarios. Also common at manufacturing plants in the area like GE or Boeing.

Fillet Weld
A weld of triangular cross-section joining two surfaces at right angles, a very common weld joint in all industries of welding. Imagine a two pieces of metal connecting in a perpendicular fashion.

Flux
A material used to prevent, dissolve, or facilitate the removal of oxides and other undesirable surface substances. This material has 5 key traits when melted from the weld arc, they are; creates a shielding gas, stabilizes the cooling rate of the weld pool, the melted flux cools and becomes slag which shields from foreign inclusions, some flux compounds add alloys to the the weld deposit which can increase the deposition rate, & helps control stabilize the arc.

MIG Welding (Metal Inert Gas)
A welding process using a shielding gas & continuous wire spool fed through a welding gun.

TIG Welding (Tungsten Inert Gas)
A welding process using a non-consumable tungsten electrode to produce the control the arc, while the other hand controls the filler metal. This process typically requires the two hands to work together.

Heat-Affected Zone (HAZ)
The area of base metal altered by welding or cutting.

Weld Pool
The localized area of molten metal in a weld prior to its solidification.

Penetration
The depth that the weld metal fuses into the base metal or previous weld bead.

Shielding Gas
An inert or semi-inert gas used to protect the weld area from atmospheric gases; it removes oxygen from the weld area.

Slag
The residue formed on the surface of molten metal as the flux cools after being melted during the welding process.

Spatter
Droplets of molten material scattered during welding, sometimes called BB’s.

Tack Weld
A small weld used to hold parts in proper alignment just before welding an item out fully. Proper tack placement and size can make the job much easier or much more difficult if done incorrectly.

Weldment
An assembly whose parts are joined by welding, a common term used in the manufacturing industry.

Arc Welding
Any welding process using an electric arc to melt metals at the welding point, a common term that is often misused as it is quite vague.

Electrode
The conductor through which electricity enters or leaves, used in welding to create the arc. The electrode varies depending the welding process.

Filler Metal
Any metal added in a joint while welding, brazing, or soldering. Every filler metal has different purposes and welding characteristics.

Groove Weld
A weld made in a groove between workpieces. Sometimes a groove weld is a butt weld, but not all the time. And sometimes a butt weld is a groove weld, but not all the times. It is a technical debate among the welding gurus of the world.

Hardfacing
Applying a hard, wear-resistant layer of metal to a surface. You can weld stainless alloys onto the surface of carbon steel to harden your tools or work piece.

Joint Preparation
The process of preparing the edges of materials to be welded.

Overhead Welding
Welding performed from the underside of a joint. Not necessarily over your head when standing, but the weld is on the bottom of a surface to your head will have to be below the weld to see it..

Porosity
Cavities in the weld metal caused by gas pockets. A very common issue when welding in the field, or in the elements. Often caused by wind gusts, a crushed or leaking shielding gas line, or many other factors.

Root Pass
The first weld pass in a multiple-pass weld, and often referred to as the “bead” in pipeline and other gas/oil industries.

Seam Welding
A process that produces a weld at the faying surfaces of a lap joint or butt joint. Often between to walls or sections.

Spot Welding
A process where contacting metal surfaces are joined by heat from resistance to electric current flow. The resulting welds will have a circular appearance.

CWI Inspection Terms

Weld Defects
Imperfections in the weld that can affect its strength and integrity, defined by numerous codes.

Undercut
A groove melted into the base metal adjacent to the weld toe or root and left unfilled by weld metal, increasing the likelihood of metal failure.

Lack of Fusion
A weld defect where the weld metal does not properly fuse with the base metal or previous weld bead.

Cold Lap
A condition where the weld metal does not properly bond with the base metal, often due to insufficient amperage or improper technique.

Lack of Penetration
A weld defect where the weld metal does not fuse through the thickness of the joint. Common on root passes when improper technique is used.

Arc Strike
An imperfection caused by the arc starting or straying outside the weld area, it can cause failure of the base metal under operating conditions.

Heat Input Calculations
The calculation of the amount of “heat”, or energy, introduced into the weld area, critical for ensuring proper weld quality. Too much heat input will alter the molecular property of steel to a point where it should not be used in any critical component.

Weld Porosity
Gas pockets trapped within the solidified weld metal, the acceptable limitations of which are define in the applicable code for that weld.

Weld Profile
The shape and contour of the weld bead as observed in a cross-section. A cause of great conflict on jobsites all across the world, it is typically not defined or labeled by most codes but welding inspectors still commonly reject welds for the dreaded “weld profile”. Other welders will also give you a hard time over excessive “weld profile” calls.

Crater
A depression at the end of the weld bead caused by the improper termination of the welding arc.

Back Gouging
The removal of weld metal and base metal from the root side of a weld to facilitate repair and complete the fusion and penetration that would have been missed.

Overlap
Excess weld metal that extends beyond the weld toe or weld root, often referred to as cold lap in the field.

Crack
The dreaded C word…. A fracture-type discontinuity characterized by a sharp break and high ratio of length and width of the opening. This will often result in the welder losing his job.

Inclusion
Non-metallic materials entrapped in the weld metal or between the weld metal and base metal.

Lamellar Tear
A subsurface discontinuity in the base metal, characterized by a step-like crack formation.

Interpass Temperature
The temperature of the weld area on multiple pass welds at the start of a new pass, not a new rod.

Preheat Temperature
The temperature to which the base metal is heated immediately before welding is started. The purpose of preheat of often mistake in the field, the true purpose is to slow the cooling rate of the base metal. Controlled cooling rates are the #1 method used on good welds that need to endure extreme conditions and critical functions.

Post-Weld Heat Treatment (PWHT)
A controlled process used to relieve residual stresses, reduce hardness, and improve the ductility of the weld and the heat-affected zone. An expensive, time consuming process that will rectify all the molecular changes made during the weld process.

Pitting
Corrosion of a metal surface, confined to a point or small area, that takes the form of cavities.

Understanding these terms helps you communicate your needs and appreciate the craftsmanship that goes into each project. At Greenville Weld Company, we are committed to delivering professional solutions tailored to your welding needs.

Reach out today to discuss how we can help bring your vision to life.