SteeLog is a metallurgical dictionary on more than 5,000 terms used in the metals and metalworking industries. You may search for a particular term or click on a letter of the alphabet to view all the terms in a specific section. This content is protected by copyright but is available for your own personal use.
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Ga - Chemical symbol for Gallium
G Coatings - Galvanize Coatings
Gage - Any one of a large variety of devices for measuring or checking the diemsions of objects.
Gage Blocks - Steel blocks machined to extremely accurate dimesions.
Gage, Center - See center gage
Gage, depth - A tool used in measuring the depth of holes or recesses.
Gage, Drill - A flat steel plate drilled with holes of various sizes, each marked with the correct size or number, into which small twist drills may be fitted to determine the size of their diameters.
Gage, Drill Point - A gage used to check the 59” angle on drills
Gage, Feeler (thickness gage) - A gage consisting of a group of very thin blades, each of which is accurately ground to a specific thickness.
Gage, indicating (dial indicator) - A gage consisting of a dial,commonly graduated (marked) in thousandths of an inch, to which is fastened an adjustable arm.
Gage Length - The original length of that portion of the specimen over which strain or change of length is determined.
Gage Marks - Reference marks; in tensile testing, the marks which indicate the gage length, used in determination of tensile elongation.
Gage, Radius (fillet gage) - Any one of a number of small,flat,standard-shaped metal leafs or blades used for checking the accuracy of regular concave and convex surfaces.
Gage, Screw Pitch - A gage consisting of a group of thin blades used for checking the number of screw threads per unit of distance, usually per inch on a screw,bolt,nut,pipe or fitting.
Gage, Surface (scribing block) - A gage used to check the accuracy of plane surfaces to scribe lines at desired distances from a given surface and to check the height of a point or points on a piece of ork from a given surface.
Gage, Telescoping - A T-shaped gage used to measure the diameter or width of holes.
Gaggers - Metal pieces of irregular shape used to reinforce and support the sand in the mold.
Gagging - Checking dimensional requirement by means of a gage.
Galfan - A galvanized product coated with 95% free zinc, 5% aluminum and traces of mish metal in the coating; provides extra corrosion protection with lighter coating weight; has improved formability over regular free zinc coatings (hot dipped galvanized regular products).
Galvalume(r) - 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 A8 is a trademark of BHP Steel, and the product is popular in the metal building market.
Galvaneal Coating (A) - 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.
Galvanic Action - When iron and steel are subject to conditions of aqueous corrosion the incidence and rate at which the corrosion takes place will alter if the steel is coupled with other metals or alloys that are also exposed to the electrolyte. Copper, brass, bronze, lead and nickel are more “noble” and act as auxiliary cathodes to the steel and accelerate its anodic dissolution, that is, its corrosion. Magnesium, zinc and zinc-base alloy are nearly always less noble and tend to divert the attack from the steel to themselves. The galvanic relationship of various metals is an important factor affecting corrosion.
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.
Galvanize - A sheet product substrate to which free zinc is applied either by hot-dipping or electro-plating.
Galvanize Coatings (G) - 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 electrodeposition process.
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. ELECTROGALVANIZED. 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. Electrogalvanizing equipment is more expensive to build and to operate than hot dipped, but it gives the steelmaker more precise control over the weight of the zinc coating. The automotive manufacturers, because they need the superior welding, forming and painting ability of electrogalvanized 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 electrogalvalizing is becoming more important today. Electrogalvanizing is a cold-coating electroplating process that, unlike the hot-dip process, does not influence the mechanical properties of the sheet steel. Electrogalvanizing 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.
Gamma Iron - A face-centered cubic form of pure iron, stable from 1670 to 2551 B0F (910 to 1400 B0C).
Gang Milling - A milling set-up where a number of cutters are arranged on an arbor so that tseveral surfaces can be machine at one time. It is commonly used for production purposes.
Gannister - An acid (silicious) refractory often used in furnace linings.
Gap - The distance between the slitter knives (ex .001", .002").
Gas Carburising - A heat treatment method used in the case-hardening of steel. Carbon is absorbed into the outer layers of the components by heating in a current of gas, rich in carbon compounds. The process is more versatile than some other methods as the depth of the case and the limiting carbon content of the case can be controlled by the composition of the atmosphere, the dew point and the temperature.
Gas Porosity - A condition existing in a casting by the trapping of gas in the molten metal or by mold gases evolved during the pouring of the casting.
Gas Stream Temp - The temperature of has stream used in heating the coils. Typical temperatures range from 1180 degrees to 1330 degrees. The system will accept a number < 1500 degrees F.
Gate - The end of a runner in a mold where molten metal enters the mold cavity.
Gate Valve - A type of valve that is opened or closed by turning the knob counterclockwise or clockwise respectively.
Gating System - The complete assembly of sprues, runners and gates in a mold through which steel flows before entering the casting cavity.
Gauge - The thickness of sheet steel. Better-quality steel has a consistent gauge to prevent weak spots or deformation.
Gauge Chart - A paper strip used to record the gauge of the strip as it runs on the side trimmers.
Gauge Code - Industry-standard code that indicates quality tolerance of the thickness of the steel.
Gauge Length - Used in the mechanical testing of steel. Better-quality steel has a consistent gauge to prvent weak spots or deformation.
Gauge Plate - An alloy tool steel supplied in flat and square section with the surfaces ground to close limits. It is also known as Ground Flat Stock and is used for the manufacturing of gauges, punches, dies, jigs, templates, ect..
Gauge Tolerance - A range by which a product's gauge can deviate from those ordered and still meet the order's requirements.
Ge - Chemical symbol for Germanium
Gear, Blank - A stamping,casting or any piece of material from which a gear is to be machined. It is usually a disk
Gear Oil - See Drive Oil.
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.
Gem Switch - An electronic module clamped to a tank sight glass used to transmit information to the computer regarding tank level.
Generating Tubes - Boiler tubes that extend from the three upper drums to the mud drum. Generating tubes are used to generate the majority of steam produced by the boiler.
Generator - The combination of an electrical generator and the steam turbine that drives it to produce electricity.
Geometric Marking - Unusual design put on one side (lite coating) of a coil to identify a different coating weight.
Germanium - Chemical symbol Ge. A rare,grayish-white metal chemcically similar to tin; obtained from processing copper and zinc. Used in the production of infrared glasses, fiber optics,electronic detectors and semiconductors.
Ghosting - A coating defect consisting of an image on the freshly coated plate giving the appearance of the substrate being bent or darker in color.
Gib - A tapered strip of metal placed between the bearing surface of two machine parts to ensure a precision fit and provide an adjustment for wear.
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.
Gland Evacuation Pump - A pump that takes the water that has condensed from steam of the seals on the #9 Generator.
Gland Water - Same as seal water.
Glaze - See “Pick-up, Rolled.”
Globe Value - See Gate Valve.
Going Down - Term referring to moving the strip to the prime reel.
Gold - Chemical symbol Au. The heraldic metal. A rare yellow mineral that is the most malleable and pliable of all metals. Gold does not tarnish or corrode, and is unaffected by exposure to air or water.
Gouging Abrasion - Abrasion involving gross surface indentation and possible removal of sizable metal fragments.
Governor - Device that controls the steam control valves on a turbine. Turning the handle in the "raise" position opens the steam control valves and will either speed the machine up if it is off-line or will cause the machine to produce more electricity if it is on-line. Turning the handle to "lower" has the opposite effect.
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 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 Fineness Number - A system developed by AFS for rapidly expressing the average grain size of a given sand. It approximates the number of meshes per inch of that sieve that would just pass the sample if its grains of uniform size. It is approximately proportional to the surface area per unit of weight of sand, exclusive of clay.
Grain Size Control - When a steel is austenitised by heating to above the critical range, time is required for the production of a Homogeneous structure during which there is a tendency towards grain growth. Although subsequent hot and cold working affect the grain size, it is originally controlled at the steel making stage by the addition of aluminium.
Grain Size Measurement - Grain size is normally quantified by a numbering system. Coarse 1-5 and fine 5-8. The number is derived fron the formula N 2n-1 where n is the number of grains per square inch at a magnification of 100 diameters. Grain size has an important effect on physical properties. For service at ordinary temperatures it is generally considered that fine grained steels give a better combination of strength and toughness, whereas coarse grained steels have better machinability.
Grain Structure - Microstructure consisting of grains (crystals) and phases in metals; generally requires examination under a microscope of an etched, polished specimen for observation.
Grain-Boundary Liquidation - An advanced stage of overheating in which material in the region of austenitic grain boundaries melts. Also known as burning.
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 (Crystalline Fracture) - A type of irregular surface produced when metal is broken.
Grasshopper - A vibrating unit that is used to carry hot fines from the hot screens to the #21 conveyor belt. Also called the hot fines vibrator.
Gratebars - Spaced to allowed air to pass through the sinter mix for aglomation/sintering process. They are located on the pallets on the sinter machine.
Gravity Filter - A unit of coal and sand media that utilizes gravity to draw water through it. The filter removes any solids carried over from the clarifiers.
Gravity Hammer - A class of forging hammer wherein energy for forging is obtained by the mass and velocity of a freely falling ram and the attached upper die. Examples are board hammers and air-lift hammers.
Gray Cast Iron - A cast iron that gives a gray fracture due to the presence of flake graphite. Often called gray iron.
Grease System - Lubricating system that supplies grease to various parts of the finishing mill.
Grease System Timer - An electronic or mechanical device used to start a grease system at predetermined intervals.
Green Rot - A form of high-temperature attack on stainless steels,nickel-chromium alloys and nickel-chromium iron alloys subjected to simultaneois oxidation and carburization. Basically, attack occurs by first precipitating chromium as chromium carbide, then oxidizing the caarbide particles.
Green Sand - A naturally bonded sand or a compounded molding sand mixture which has been tempered with water for use while still in the damp or wet condition.
Green Sand Core - A sand core used in the unbaked condition, also a core made from green sand and used as rammed.
Green Sand Mold - A mold composed of moist molding sand and not dried before being filled with molten metal.
Green Strength - The strength of a tempered sand mixture at room temperature.
Greenfield Steel Mill - New mill that is built "from scratch," presumably on a green field.
Grey Iron - Alsoo known as flake iron on account of all or part of the carbon content being in the form of graphite distributed through the metal as flakes.
Grinding - Process of removing metal by abrasion from bar or billet stock to prepare stock surfaces for forging. Occasionally used to remove surface irregularities and flash from forgings.
Gripper Bar Kink - A condition created by poor initial start on the reel or a loose first lap.
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.
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.
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.
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.
Guides - Devices used for keeping the strip square to produce a proper weld.
Guillotine Valve - A slide-plate type valve which blocks the flow of material through a line.
Gutter - A slight depression surrounding the cavity in the die to relieve pressure and control flash flow.
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.
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.
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 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 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 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.
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.
Guide - Device for holding the metal in the proper position, during rolling, or slitting.
Gun Drill - A drill, usually with one or more flutes and with coolant passages through the drill body, used for deep hole drilling.
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