Glossary

Galling

A condition whereby excessive friction between high spots results in localized welding with subsequent splitting and a further roughening of rubbing surfaces of one or both of two mating parts.

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.

Gauges & Width Tolerance

Customers always order a specific gauge and width (and in some cases length). Since it is impossible to produce material to that exact gauge or width, the actual gauge or width will vary to be slightly above, slightly below, and sometimes exactly on the ordered gauge and width. Tables have been published by various organizations which spell out how much above and below the ordered width, gauge, and length you are permitted to be and still have an acceptable product. Probably the most common of these tables are those in the ASTM Specification A480. Mill price books usually contain tolerance data.

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 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

The enlarging or coarsening of the individual grains within the metal or alloy during heating at a temperature above the recrystalization temperature. Excessive grain growth can cause Orange Peel during drawing.

Grain Size

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. In metals containing two or more phases, the grain size refers to that of the matrix unless otherwise specified. Grain sizes are reported in terms of number of grains per unit area or volume, average diameter, or as a grain-size number derived from area measurements.

Grains

Crystals.

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.

Green rot

A form of high-temperature attack on stainless steels, nickel-chromium alloys, and nickel-chromium iron alloys subjected to simultaneous oxidation and carburization. Basically, attack occurs by first precipitating chromium as chromium carbide, then oxidizing the carbide particles.

Grit

Grit refers to small particles of something that tend to be abrasive. Sugar and salt are grit. The coarseness or fineness of grit is defined by a numbering system, with coarse grit having low numbers such as 12 and fine grit having high numbers such as 1000. This numbering system is used to define the fineness or coarseness of the abrasive belts that we use to grind or polish the steel, the abrasive wheels that are used to condition the slab, and the shot that is used to blast the rolls for the skin pass mills that create different matte finishes.