Glossary D – G

Datum plane

The reference plane from which dimensions are measured.

Datum points

The reference points on a datum plane from which dimensions are measured.


Direct current.


Loss of carbon from the surface layer of a carbon-containing Alloy.


A departure of any quality characteristic from its intended level that is severe enough to cause the product or service not to fulfill its anticipated function.


A crystal that has a treelike branching pattern, being most evident in cast metals slowly cooled through the solidification range.


Removal of excess oxygen from molten metal, usually accomplished by adding materials with a high affinity for oxygen.


DET NORSKE VERITAS, An accrediting body based in Norway.


The ability of a material to deform plastically without fracturing, usually measured by elongation or reduction of area in a tensile test.


A technique in which a high polish is produced by making the part the anode in an electrolytic cell, where preferential dissolution at high points smoothes the surface.


In tensile testing, the increase in the gage length, measured after fracture of the specimen within the gage length, usually expressed as a percentage of the original gage length.


Reduction in the normal ductility or toughness of a metal, usually due to a physical or chemical change.


Subjecting the surface of a metal to preferential chemical or electrolytic attack in order to reveal structural details for metallurgical examination.


A solid solution of one or more elements in body-centered cubic iron.


A metal or wood frame used for making and holding a sand mold. The upper part is called the cope; the lower the drag.

Fluorescent magnetic particle inspection

Inspection with either dry magnetic particles or those in a liquid suspension, the particles being coated with a fluorescent substance to increase the visibility of the indications. Commonly referred to as FPI or FMT.


Plastically deforming metal, usually hot, into desired shapes with compressive force, with or without dies.

Full annealing

An annealing cycle designed to produce minimum strength and hardness.


Checking dimensional requirements by means of a gage.

Galvanic Corrosion

Corrosion of a metal in an electrolyte because of an electrical contact with another, more noble metal in the same electrolyte.

Gas metal arc welding

A fusion welding process in which metals are joined by heating in a protective gas atmosphere with an electric arc between a consumable metal electrode and the work

Gas tungsten arc welding

A fusion welding process in which metals are joined by heating them with an electric arc between a non-consumable tungsten electrode and the work.


Gas Metal Arc Welding.


An individual crystal in a polycrystalline metal or Alloy.

Grain size

For metals, a measure of the dimensions, areas or volumes of grains in a polycrystalline material; usually expressed an average when the individual sizes are fairly uniform.

Grit blasting

Abrasive blasting with small irregular pieces of steel, malleable cast iron, or hard nonmetallic materials.

Grit size

Nominal size of particles in an abrasive or of the abrasive particles in a grinding wheel, corresponding to the number of openings per linear inch in a screen through which the particles can just pass. Sometimes called “grain size.”


Gas Tungsten Arc Welding.