API 577 key terms

A written document that gives the required welding variables, such as process, filler metal, preheat, and electrical settings, so a production weld can be made consistently to a qualified design.

A record of the test weld made to qualify a welding procedure; it documents actual variables, test results, and examination results that support the WPS.

Evidence that a welder or welding operator has passed the required tests for a specific process, position, and joint configuration, showing the skill needed to produce sound production welds.

A welding condition that must be controlled and, if changed beyond specified limits, requires requalification because it can affect weld properties or soundness.

Heating the base metal before welding to reduce cooling rate, remove moisture, and help prevent cracking; the required temperature depends on material and thickness.

Controlled heating and holding of a completed weldment at a specified temperature, followed by controlled cooling, to reduce residual stress or temper hard microstructures.

Energy delivered per unit length of weld, usually calculated from arc voltage, current, and travel speed; it influences cooling rate, HAZ hardness, and mechanical properties.

A calculated value that expresses how alloying elements increase a steel's hardenability and cracking susceptibility compared with carbon alone in welded steel.

The base metal adjacent to a weld that is not melted but is changed by welding heat, often showing altered microstructure, hardness, or toughness.

Loss of ductility and cracking caused by hydrogen entering steel, often from moisture or contaminated consumables, especially in high-strength or hard weld zones.

A change in some stainless steels where chromium carbides form at grain boundaries during heating, leaving chromium-depleted zones that are vulnerable to corrosion.

Step-like cracking in plate thickness caused by high through-thickness restraint and inclusions, often found beneath welded joints in rolled steel.

A weld discontinuity where weld metal fails to bond to base metal or to previous weld passes, often caused by low heat input, poor access, or contamination.

A discontinuity in which the weld does not extend through the full joint thickness or does not reach the root, reducing the effective load-bearing section.

Gas trapped in weld metal as rounded voids; it can result from moisture, inadequate shielding, dirty surfaces, or improper welding parameters.

Nonmetallic slag trapped in weld metal or between passes, usually from incomplete cleaning or poor slag removal in flux-based processes.

A groove melted into the base metal at the weld toe or root and left unfilled, creating a stress concentration and reducing thickness.

A localized spot of melted or heat-affected base metal caused by an unintended arc, which can create hard spots and cracking.

Unwanted change in shape or dimensions of a weldment that occurs because of nonuniform heating, cooling, and shrinkage during welding.

Internal stress remaining in a weldment after welding and cooling, produced by restrained expansion and contraction; it can contribute to cracking or distortion.

Material placed at the root of a joint to support molten weld metal, retain shielding, or control root shape; it may be permanent or removable.

The first weld pass deposited at the joint root; it establishes penetration and fusion and is often the most critical pass for root defects.

The final weld pass on the outer surface of a joint, shaping the weld profile and covering underlying passes; it affects appearance and can influence stress concentration.

Depositing one or more layers on a surface before welding, often to improve compatibility, reduce dilution, or provide a suitable base for a repair.

A surfacing operation that deposits weld metal on a component to restore dimensions, add corrosion resistance, or provide a hard wear-resistant layer.

Welding performed to correct a defect, restore a worn area, or join a patch after removing unacceptable material; it usually needs approved procedures and inspection.

Removal of defective weld or base metal, often by grinding or gouging, to sound metal before repair welding; the cavity shape must allow proper access and fusion.

A nondestructive method that uses X-rays or gamma rays to produce an image of internal weld features, showing voids, inclusions, and some cracks.

A nondestructive method that sends high-frequency sound waves into material and analyzes echoes to detect internal discontinuities, laminations, and lack of fusion.

A nondestructive method that magnetizes ferromagnetic material and applies magnetic particles; surface or near-surface discontinuities create leakage fields that attract particles.

A nondestructive method that applies a liquid penetrant to a clean surface, removes excess, and uses developer to reveal surface-breaking discontinuities.

An ultrasonic technique using multiple small elements pulsed with controlled timing to steer and focus the beam, improving detection and sizing of discontinuities.

The specified limits used to judge whether a weld or discontinuity is acceptable; they are defined by the applicable code, standard, or contract.

A document that records a departure from specified requirements, describes the condition, and tracks disposition, corrective action, and closure for the affected item.

A project document listing inspection and test activities, their sequence, acceptance references, and who performs or witnesses each hold point.