Glossary of Steel Terms

Glossary of Steel Terms

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Gages
Mfrs. standard numbering systems indicating decimal thickness' or diameters.

Galling
The damaging of one or both metallic surfaces by removal of particles from localized areas due to seizure during sliding friction.

Galling
Developing a condition on the rubbing surface of one or both mating parts where excessive friction between high spots results in localized welding with substantial spalling and a further roughening of the surface.

Galvanic Corrosion
Corrosion associated with the current of a galvanic cell consisting of two dissimilar conductors in an electrolyte or two similar conductors in dissimilar electrolytes. Where the two dissimilar metals are in contact, the resulting action is referred to as couple action.

Galvanizing
Coating steel with zinc and tin (principally zinc) for rust proofing purposes. Formerly for the purpose of galvanizing, cut length steel sheets were passed singly through a bath of the molten metal. Today's galvanizing processing method consists of uncoiling and passing the continuous length of successive coils either through a molten bath of the metal termed Hot Dipped Galvanizing or by continuously zinc coating the uncoiled sheet electrolytically- termed Electro-Galvanizing.

Gamma Iron
The form of iron stable between 1670 (degrees) F., and 2550 (degrees) F., and characterized by a face-centered cubic crystal structure.

Gas Welding
Welding with a gas flame.

GFM - Gyratory Forging Machine
A machine designed to hot forge a cylindrical bar shape while it is turning at speed.

Gilding Metal
A copper-zinc alloy containing 95% copper and 5% zinc. While similar to deoxidized copper in physical properties, it is somewhat stronger and very ductile. It has thermal and electrical conductivity slightly better than half that of electrolytic copper and corrosion resistance comparable to copper.

Grain
A solid polyhedral (or many sided crystal) consisting of groups of atoms bound together in a regular geometric pattern. In mill practice grains are usually studied only as they appear in one plane. (1) (Direction of) Refers to grain fiber following the direction of rolling and parallel to edges of strip or sheets. (2) To bend across the grain is to bend at right angles to the direction of rolling. (3) To bend with the grain is to bend parallel to the direction of rolling. In steel, the ductility in the direction of rolling is almost twice that at right angles to the direction of rolling.

Grain
An individual crystal in a polycrystalline metal or alloy, including twinned regions or subgrains if present.

Grain Boundary
Bounding surface between crystals. When alloys yield new phases (as in cooling), grain boundaries are the preferred location for the appearance of the new phase. Certain deterioration, such as season cracking and caustic embrittlement, occur almost exclusively at grain boundaries.

Grain Coarsening
A heat treatment that produces excessively large austenitic grains.

Grain Flow
Fiber like lines appearing on polished and etched sections of forgings, caused by orientation of the constituents of the metal in the direction of working during forging.

Grain Growth
An increase in the average size of the grains in polycrystalline metal or alloy, usually a result of heating at elevated temperature.

Grain Growth
An increase in metallic crystal size as annealing temperature is raised; growth occurs by invasion of crystal areas by other crystals.

Grain Size
(1) For metals, a measure of the areas or volumes of grains in a polycrystalline material, usually expressed as an average when the individual sizes are fairly uniform. Grain sizes are reported in terms of grains per unit area or volume, average diameter, or as a grain-size number derived form area measurements.

Grain Size
Average diameter of grains in the metal under consideration, or alternatively, the number of grains per unit area. Since increase in grain size is paralleled by lower ductility and impact resistance, the question of general grain size is of great significance. The addition of certain metals affects grain size, for example vanadium and aluminum ten to give steel a fine grain. The ASTM has set up a grain suze standard for steels, and the McQuaid-Ehn Test has been developed as a method of measurement.

Grain Size
A measure of the areas or volumes of grains in a polycrystalline metal or alloy, usually expressed as as average when the individual sizes are fairly uniform. In metals containing two or more phases, the grain size refers to that of the matrix unless otherwise specified. Grain size is reported in terms of number of grains per unit area or volume, average diameter, or as a number derived from area measurements.

Grain-Boundary Liquidation
An advanced stage of overheating in which material in the region of austenitic grain boundaries melts. Also known as burning.

Grain-Boundary Sulfide Precipitation
An intermediate stage of overheating in which sulfide inclusions are redistributed to the austenitic grain boundaries by partial solution at the overheating temperature and reprecipitation during subsequent cooling.

Grains
Individual crystals in metals.

Granular Fracture
A type of irregular surface produced when metal fractures, characterized by a rough, grain like appearance as differentiated from a smooth silky, or fibrous, type. It can be sub classified into trans-granular and inter-granular forms.. This type of fracture is frequently called crystalline fracture, but the implication that the metal has crystallized is completely misleading.

Granular Fracture
A type of irregular surface produced when metal is broken, that is characterized by a rough, grain like appearance as differentiated from a smooth silky, or fibrous, type. It can be sub-classified into trans-granular and inter-granular forms. This type of fracture is frequently called crystalline fracture, but the inference that the metal has crystallized is not justified.

Granulated
A coarse grain or pebbly surface condition which becomes evident during drawing.

Granulation
The formation of grains immediately upon solidification.

Graphite
The polymorph of carbon with a hexagonal crystal structure.

Graphitization
Formation of graphite in iron or steel. Primary graphitization refers to formation of graphite during solidification. Secondary graphitization refers to later formation during heat treatment.

Graphitizing
A heating and cooling process by which the combined carbon in cast iron or steel is transformed, wholly or partly, to graphitic or free carbon.

Graphitizing
Annealing a ferrous alloy in such a way that some or all of the carbon is precipitated as graphite.

Gray Cast Iron
A cast iron that gives a gray fracture due to the presence of flake graphite. Often called gray iron.

Grinding
Removing material from from a work piece with a grinding wheel or abrasive belt.

Grinding Cracks
Shallow cracks formed in the surface of relatively hard materials because of excessive grinding heat or the high sensitivity of the material.

Ground Flat Stock
Annealed and pre-ground (to close tolerances) tool steel flats in standard sizes ready for tool room use. These are three common grades; water hardening, oil hardening, and air hardening quality.

Guide
Device for holding the metal in the proper position, during rolling, or slitting.

Guide Scratch
Scratches or marks appearing parallel to edges of cold rolled strip caused by scale or other particles which have become imbedded in or have adhered to the rolling mill guide. Also applies to similar scatches appearing as a result of slitting.

Gun Drill
A drill, usually with one or more flutes and with coolant passages through the drill body, used for deep hole drilling.