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

Galvalume®
Steel sheet with a unique coating of 55% aluminum and 45% zinc that resists corrosion. The coating is applied in a continuous hot-dipped process, which improves the steel's weather resistance. Galvalume® is a trademark of BHP Steel, and the product is popular in the metal building market.

Galvanneal Coatings (A Coatings)
Coatings on hot-dipped galvanized steels processed to convert the coating completely to zinc-iron alloys; dull gray in appearance, have no spangle, and after proper preparation, are well suited for painting without additional surface preparation, can withstand moderate forming and are more weldable than galvanized coatings.

Galvanize
A sheet product substrate to which free zinc is applied either by hot-dipping or electro-plating.

Galvanize Coatings (G Coatings)
Free zinc coatings applied to a hot rolled or cold rolled steel to produce galvanized steel. The coating can be applied by the hot-dip or electro-deposition process.

Galvanneal Furnace
A furnace (gas-fired or induction) which is placed over the strips as it exits the zinc bath for the purpose of producing fully alloyed iron zinc coating.

Galvanized Steel
Steel coated with a thin layer of zinc to provide corrosion resistance in underbody auto parts, garbage cans, storage tanks, or fencing wire. Sheet steel normally must be cold-rolled prior to the galvanizing stage.
Hot-dipped. Steel is run through a molten zinc coating bath, followed by an air stream "wipe" that controls the thickness of the zinc finish.
Electro-galvanized. Zinc plating process whereby the molecules on the positively charged zinc anode attach to the negatively charged sheet steel. The thickness of the zinc coating is readily controlled. By increasing the electric charge or slowing the speed of the steel through the plating area, the coating will thicken.
Differences. Electro-galvanizing equipment is more expensive to build and to operate than hot dipped, but it gives the steel maker more precise control over the weight of the zinc coating. The automotive manufacturers, because they need the superior welding, forming and painting ability of electro-galvanized steel, purchase 90% of all tonnage produced.

Galvanizing
Coating steel with a thin layer of zinc to increase its corrosion resistance. Most galvanizing is done on a hot-dip operation, but electro-galvalizing is becoming more important today. Electro-galvanizing is a cold-coating electroplating process that, unlike the hot-dip process, does not influence the mechanical properties of the sheet steel. Electro-galvanizing provides a more uniform coating.

Galvanizing Pot
Holds the molten free zinc coatings applied to a hot rolled or cold rolled steel to produce Hot-dip Galvanized steel.

Galvannealed
An extra tight coat of galvanizing metal (zinc) applied to a soft steel sheet, after which the sheet is passed through an oven at about 1200 degrees F. The resulting coat is dull gray without spangle especially suited for subsequent painting.

Gangue
Part of an ore, which has to be either removed during benefication of the ore, or slagged during smelting.

Ganister
A siliceous refractory material used in acid furnace.

Gardner Impact Test
In this test, a projectile is dropped from a particular distance to dent the steel to various depths. The impact is measured in inch-pounds, and the coating adherence is determined by assessing flaking or crazing on the convex side of the cup.

Gas Carburising
Carburising carried-out by heating the steel in direct contact with carburizing gases.

Gas Knife
It consists of a stream of gas, usually air or stream, directed at both sides of the strip being galvanized, as it emerges from the coating bath. The pressure of the gas and the positioning of the knife relative to the strip surface are controlled to give the desired weight of coating for the speed used. In special cases, nitrogen gas is used to produce a smoother finish.

Gate
The clearance cut in the front of a die to accommodate the bar undergoing forging and to retain a connection between the bar & the forging.

Gathering
Increasing the cross section of the stock beyond the original size.

Gauge
1. An instrument that measures pressure, temperature, level or flow depending on the purpose. 2. The thickness of the steel strip. Better-quality steel has a consistent gauge to prevent weak spots or deformation.

Gauge Code
Industry-standard code that indicates quality tolerance of the thickness of the steel.

Gauge Tolerance
A range by which a product’s gauge can deviate from those ordered and still meet the order’s requirements.

Gel Spotting
A coating defect consisting of the uniform circular spots or droplets of higher film thickness on the coated sheet. Gel spotting, while appearing similar to slinging, is much more uniform in appearance and caused by a different mechanism. Gel spotting occurs when a partially gelled coating is applied to the substrate.

Geometric Marking
Unusual design put on one side (lite coating) of a coil to identify a different coating weight.

Ghost
A segregated streak, usually containing a concentration of sulphide, oxide, etc. which have become elongated during rolling or forging. This looks different in colour than the rest of the sheet when sheet is tarnished.

Goethic Section
A rolled or forged product having approximately square section. The dimensions are specific with specified radius or chamfer at corners without any concavity on the sides.

Gouges
A gross type of scratch.

Grade
The term grade designates divisions within different types based on carbon content or mechanical properties; for example, "This is a high tensile (grade) structural steel."

Grain Structure
Microstructure consisting of grains (crystals) and phases in metals; generally requires examination under a microscope of an etched, polished specimen for observation.

Granular Fracture
A type of irregular surface produced when metal is broken that is characterized by a rough, grain-like appearance, rather than a smooth or fibrous one. It can be sub-classified into trans-granular and inter-granular forms. The fracture is frequently called crystalline fracture, but the implication that the metal failed because it crystallized is misleading, because all metals are crystalline in the solid state.

Granulated Slag
Molten blast-furnace slag is quenched quickly in water to form a product called ‘granulated slag’. No crystallization occurs in this process. Depending upon chemical composition of the slag, its temperature at the time of quenching in water, and the method of production utilized, the physical structure of the granulated grains may vary from a friable popcorn-like structure to grains resembling dense glass.

Graphite Electrodes
Made from petroleum coke at high heat to form artificial crystalline carbon, graphite electrodes are used in electric steel-making furnaces.

Graphitization
The decomposition of iron oxide or, in any event, the rejection of elemental carbon in a casting after solidification has taken place, the carbon being liberated in the form of graphite which is usually found existing as minute, flaky particles disseminated throughout the casting.

Graphitizing
Annealing a ferrous alloy such that some or all the carbon precipitates as graphite.

Greenfield Steel Mill
New mill that is built "from scratch," presumably on a green field.

Grinding
Removing material from a workpiece using a grinding wheel or abrasive belt.

Grit Size
Nominal size of abrasive particles in a grinding wheel, corresponding to the number of openings per linear inch in a screen through which the particles can pass.

Grit
1. Texture of the surface of a roll; applied through sand-blasting and grinding; the lower the number, the higher the grit and the rougher the surface; 50, 90, 150, 200, and 220 grit. Temper Mills may run grit. Grit also refers to the finish on the surface of the steel. 2. The size of the shot blast used to mechanically texture a roll for producing a grit finish product. Grit can be classified as either night or heavy. Light grit is a non-metallic inorganic material with excellent abrasive characteristics, such as aluminum oxide. Heavy grit is principally of the metallic type such as cast-iron shot. Metallic grit is the type most generally used on a bar product.

Grit Blasting
Or blast-cleaning, is a mechanical process used for removing scale and rust from bar products. It consists of eroding or abrading away the scale from the surface of the bar impinging an abrasive substance like sand, aluminum oxide, or a metallic substance like cast iron or steel shot.

Ground Roll Finish
The bright or smooth microfinish on the last stand of a tandem mill or temper mill; produced by grinding; determines the surface finish of the product where brightness is desired.

Guides
In order to prevent collaring and to ensure that the steel piece being rolled enters and leaves the pass in the correct position, guides are employed. These guides vary in form and size to fit the conditions. Guides may be employed on both sides of the pass, in which case they are designated as entering guides and delivery guides.

Guide Mark (Guide Scratch, Guide Score, Guide Shearing)
A surface defect resulting from abrasion between the steel / iron and a guide used for ensuring location in rolling.

Guards
Devices employed mainly on the delivery side of the mill to control the direction of the piece being rolled after it leaves the pass. Reversing and three-high mills are provided with guards on both sides of the mill.

Gutter
A recess surrounding the impression in the die face , to receive access metal beyond the fash proper