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
- 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
- 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
Haematite (Hematite)
Iron oxide, having a composition Fe2O3, corresponding to 69.94% of iron and 30.06% of oxygen, specific gravity 5.26, occurring in nature in igneous, metamorphic, and sedimentary rocks as a product of the weathering of magnetite and associated with varying amounts of impurities.
Hair Line Cracks (Hair Cracks)
Internal ruptures in steel caused by stresses which arise from the combination of several factors, such as volume changes due to transformation, brittleness due to the presence of hydrogen, and the arrangement of the micro-structure, resulting from hot working. The size of such ruptures may vary considerably but they are usually comparatively short in length when viewed on a surface cut at right angles to the plane of defect and generally are so fine that they cannot be discerned other than after etching or by magnetic crack detection.
Half-Hard Temper
Cold Rolled steel produced to a Rockwell hardness range of 70 to 85 on the B scale. Product of this temper is intended for limited cold forming and will only withstand 90-degree bends made across the rolling direction.
Hangar Crack
A transverse ingot crack caused by obstruction to normal contraction of an ingot during cooling in mould, and is associated with incorrect feeder head setting. Also occurs from overfilling.
Hanging
See Slips.
Hardenability
The relative ability of a ferrous alloy to form martensite when quenched from a temperature above the upper critical temperature. Hardenability is commonly measured as a distance below a quenched surface at which the metal exhibits a specific hardness– 50 HRC, for example- or a specific percentage of martensite in the micro-structure.
Hardening
Increasing hardness by suitable treatment, usually involving heating and cooling. See also age hardening, case hardening, induction hardening, precipitation hardening, and quench hardening.
Hardness
A measure of the resistance of a material to surface indentation or abrasion; may be thought of as a function of the stress required to produce some specified type of surface deformation. There is no absolute scale for hardness; therefore, to express hardness quantitatively, each type of test has its own scale of arbitrarily defined hardness. Indentation hardness can be measured as Brinell, Rockwell, Vickers, Knoop, and Scleroscope hardness tests.
Hard Drawn Wire
Wire drawn with a relatively large reduction(over 10%) from the rod without heat treatment.
Hardness Index
A property of metallurgical coke to withstand abrasion. It is expressed as the percentage of coke remaining on ¼-inch screen when the coke of selected size is screened after it has been tumbled in a standard drum which is rotated for a specific time at a specific rate.
Hardness Value
Degree to which a material resists deformation, indentation or scratching. There are many numerical scales (and thus methods) to measure the hardness value (example: Brinell, Rockwell, Vickers, etc.)
Hardening
What Process that increases the hardness of steel, i.e., the degree to which steel will resist cutting, abrasion, penetration, bending, and stretching.
Why The increased endurance provided by hardening makes steel suitable for additional applications.
How Hardening can be achieved through various methods, including (1) heat treatment, where the properties of steel are altered by subjecting the steel to a series of temperature changes; and (2) cold working, in which changes in the structure and shape of steel are achieved through rolling, hammering, or stretching the steel at a relatively low temperature.
Heat (of Steel)
A batch of refined steel. A basic oxygen or electric furnace full of steel. One heat of steel will be used to cast several slabs, blooms or billets.
Heat Affected Zone
That portion of the base metal that was not melted during brazing, cutting, or welding, but whose microstructure and mechanical properties were altered by the heat.
Heat Cover
A cylindrical or rectangular inner cover placed over the coils prior to placing the furnace on the base in the Batch Anneal.
Heat Exchanger
Removes heat from oil with water.
Heat Exchanger Tubes
Tubes used in a unit for the purpose of transferring heat from one medium to another.
Heat Number
In the Batch Anneal, this is the computerized annealing sequence number used by the Firing Model to associate target values to the Heat Sequence. It is required to run the Firing Model. In the BOP a sequential number assigned to each batch of steel.
Heat Tinting
Coloration of a metal surface through thermal oxidation by heating to reveal details of structure.
Heat Treatment
What Altering the properties of steel by subjecting it to a series of temperature changes.
Why To achieve the desired microstructural / mechanical properties like the hardness, strength, or ductility of steel or alloys so that it is suitable for additional applications.
How The steel is heated and then cooled as necessary to provide changes in the structural form that will impart the desired characteristics. The time spent at each temperature and the rates of cooling have significant impact on the effect of the treatment.
Heat Waste (Fire Waste)
The loss of material by scaling in a reheating or hot working process.
Heavy Coating
A condition caused by too much coating being applied to the strip.
Heavy Gauge
Product with a thickness above the customer’s maximum gauge tolerance.
Heavy/Light Gauge
Steel plate not meeting customer gauge specifications.
Heavy Structural Shapes
A general term given to rolled flanged sections that have at least one dimension of their cross sections three inches or greater. The category includes beams, channels, tees and zees if the depth dimension is three inches or greater, and angles if the length of the leg is three inches or greater.
Hertz
Term used to describe the frequency in an AC circuit. Essentially the same as cycles. If a circuit is 60 Hz or 60 cycles, that means that the AC wave has gone through 60 complete waves in one second.
Hickey
A coating defect consisting of a randomly oriented small speckled appearance on coated plate after inks are applied.
High Carbon Steel
Carbon steel containing generally more than 0.6% carbon. The more carbon that is dissolved in the iron, the less formable and the tougher the steel becomes. High-carbon steel’s hardness makes it suitable for plow blades, shovels, bedsprings, cutting edges, or other high-wear applications.
High Hot-Blast Temperatures
Use of better stove-firing techniques, better stove-changing equipment, improvements in burden materials, the use of tuyere-injected fuels and the control of blast moisture make it possible for the blast furnace to accept the higher hot-blast temperatures (upto 1250o C). This results in reduction in coke rate as well as improvement in blast furnace efficiency.
High Rockwell
A condition that occurs when the hardness of the steel is above the maximum limit as specified by the customer.
High Speed Steel
A special variety of tool steel which, by virtue of its composition, retains its cutting hardness at a low red heat.
High Strength Low Alloy (HSLA)
A specific group of steel in which higher strength, and in some cases additional resistance to atmospheric corrosion or improved formability, are obtained by moderate amounts of one or more alloying elements such as columbium, vanadium, titanium, used alone or in combination.
HNX Gas
A mixture of hydrogen and nitrogen gas used to prevent oxidation and to clean the strip during the annealing process.
Hold
Coil type indicating that a produced coil or lift has problems that need to be resolved by the Quality Assurance department.
Hollow Forging
Forging a tube, ring or drum on a becking bar or mandrel.
Home Scrap
Also called ‘revert scrap’, it includes such items as pit scrap ; ingots too short to roll; rejected ingots; crop ends from slabs, blooms and billets; shear cuttings from trimming flat-rolled products to specified size; products irrevocably damaged in handling or finishing; ends cut from structural shapes, rails, bars, pipe or tubing to bring them to standard or exact ordered lengths; turnings from machining operations, broken moulds; obsolete machinery, dismantled buildings, steel shot recovered from slag, and so on. Bloom and slab crops constitute the largest single item of home scrap.
Homogenizing
Holding at high temperature to eliminate or decrease chemical segregation by diffusion.
Hood
The membrane-type construction (alongwith the stacks) above the basic oxygen furnaces leading to the gas cleaning and dust collecting facilities are called hoods. These are cooled by water flowing in 1 ½ inch dia steel tubes separated on 2 inch centres.
Hook
A short bend or curvature caused either by improperly adjusted delivery guides or by any obstruction which may halt momentarily the forward motion of the bar from one roll stand to another.
Horse Shoe Quality
A quality of wrought iron specifically manufactured for horse shoes.
Hot Band (Hot-Rolled Steel)
A coil of steel rolled on a hot-strip mill (hot-rolled steel). It can be sold in this form to customers or further processed into other finished products.
Hot Briquetted Iron (HBI)
Direct reduced iron that has been processed into briquettes. Instead of using a blast furnace, the oxygen is removed from the ore using natural gas and results in a substance that is 90%-92% iron. Because DRI may spontaneously combust during transportation, HBI is preferred when the metallic material must be stored or moved.
Hot-Dip Galvanizing After Fabrication
A batch process used to produce a zinc coating on manufactured steel products by total immersion of structural or fabricated steel in a bath of molten zinc. The process provides a metallurgically bonded coating, generally 100 um (4 mils) thick, consisting of iron-zinc alloy layers covered with zinc.
Hot Drawn
Tubes which have been reduced in diameter, or diameter and thickness both, by drawing hot on a mandrel through a die.
Hot End
The section of a steel making complex from the furnace up to, but not including, the hot-strip mill.
Hot Etching
Development and stabilization of the micro-structure at elevated temperature in etchants or gases.
Hot Forming
Operations such as bending and pressing, after heating the material to appropriate temperature.
Hot Metal
The name for the molten iron produced in a blast furnace. It proceeds to the basic oxygen furnace in molten form or is cast as pig iron.
Hot Metal Process
A steel making process using molten metal from blast furnace mixer or cupola as major portion of the charge.
Hot Mill
The rolling mill that reduces a hot slab into a coil of specified thickness; the whole processing is done at a relatively high temperature (when the steel is still “red”).
Hot Quenching
An imprecise term for serious quenching procedures in which a quenching medium is maintained at a prescribed temperature above 70o C.
Hot Roll
Product that is sold in its “as produced state” off the Hot Mill with no further reduction or processing steps aside from being pickled and oiled (if specified).
Hot Roll Base
Hot rolled coils which have been pickled in an acid solution to remove surface oxidation, then is oiled to prevent rust. Coils that come directly off the Pickling Line and are not cold roll reduced on the tandem mill.
Hot Roll, P&O
Hot Roll Pickle and Oil that does not go to a in-house Tandem Mill. It may not necessarily be shipped out; it could go to the Temper Mill.
Hot Rolled Sheets
Manufactured by hot rolling slabs to the required thickness.
Hot Sawing
Cutting hot iron to length during or immediately following hot rolling, by a circular saw.
Hot-Strip Mill
A rolling mill of several stands of rolls that converts slabs into hot-rolled coils. The hot-strip mill squeezes slabs, which can range in thickness from 2-10 inches, depending on the type of continuous caster, between horizontal rolls with a progressively smaller space between them (while vertical rolls govern the width) to produce a coil of flat-rolled steel about a quarter-inch in thickness and a quarter mile in length.
Hot Working
Plastic deformation of metal at temperatures higher than recrystallization temperature. The forces required to deform the metal are very insensitive to the rate of application of loads and to temperature variations, but the basic strength of the metal after the deformation is essentially unchanged.
Hydro-forming
A forming process in which a tube is placed into a forming die. The tube is then formed to the shape of the die through the application of internal water pressure. The hydroforming process allows for severe shape deformation, making it ideal for automotive structural parts such as engine cradles, radiator supports and body rails. Various shaped and sized holes can be punched in the tube almost anywhere during the process.
Hydrogen Damage
A general term for the embrittlement, cracking, blistering, and hydride formation that can occur when hydrogen is present in some metals.
Hydraulic Lap-weld Process (Water-Gas Lapweld Process)
A process for making large diameter welded tubes in which a steel plate is bent into cylindrical shape in bending rolls. The overlapping edges are heated for short distances to welding temperature and subsequently welded by pressing them together by hydraulic power. The heating and pressing is repeated until the length is welded. The tube is then heated all over and passed through rounding rolls. For certain sizes, two plates may be required to make the necessary circumference.
I-Beams
Structural sections on which the flanges are tapered and are typically not as long as the flanges on wide-flange beams. The flanges are thicker at the cross sections and thinner at the toes of the flanges. They are produced with depths of 3-24 inches.
ID
Inside diameter (of a coil).
Immersion Etching
Method in which a microstructure is dipped face up into etching solution and is moved around during etching. This is the most common etching method.
Impact Tests
Tests to determine the energy absorbed in fracturing a test specimen at high velocity. There are various kinds of impact tests, such as charpy, izod, drop weight, etc.
Inclusions (Non-metallic Inclusions)
Refers to a defect when particles of nonmetallic impurities, usually oxides, sulfides, silicates, refractories and such, which are the products of deoxidation, are insoluble in the matrix and are mechanically held in steel during solidification.
Inclusion Count
Determination of the number, kind, size, and distribution of non-metallic inclusions.
Induction Hardening
A surface-hardening process in which only the surface layer of a suitable ferrous workforce is heated by electrical induction to above the upper transformation temperature and immediately quenched.
Induction Process
A process in which the heating is done by eddy currents generated in the charge by the induction coil surrounding the charge. Depending upon the frequency used, the process is called low frequency, medium frequency and high frequency melting.
Ingot
A form of semi-finished steel. Liquid steel is teemed (poured) into vertical cast iron moulds, where it slowly solidifies. Once the steel is solid, the mould is stripped, and the 25- to 30-ton ingots are then ready for subsequent rolling or forging.
Ingot Corner Segregation
A longitudinal plane of relatively impure steel arising from segregation occurring in the region of a corner of an ingot.
Ingot Iron
Very low carbon steel generally made in the open hearth in which all the other elements are removed to the maximum extent possible. Some of the commercial products falling under this group have less than 0.1 percent of all elements put together.
Ingot Mould (Mould)
The container, usually made of cast iron, into which molten steel is poured and allowed to solidify.
Inmetco
What Inmetco is a coal-based process similar to FASTMET that uses iron oxide fines and pulverized coal to produce a scrap substitute. Mill scale and flue dust, inexpensive byproducts of steel making, can be mixed with the iron oxide fines. Inmetco, unlike other direct reduction products, is intended to be hot charged into an EAF, with attendant energy savings.
How The process includes three steps. First, iron oxide fines, pulverized coal and a binder are formed into pellets. Second, the pellets, two to three layers deep, are heated in a gas-fired rotary hearth furnace for 15-20 minutes to produce sponge iron. Subsequently, the iron must be desulfurized. The coal in the pellets provides much of the energy required in the second phase.
Insert
A piece of steel permanently fixed in the die, which may be used to fill a cavity or to replace a portion or the whole of the impression.
Integrated Mills
These facilities make steel by processing iron ore and other raw materials in blast furnaces. Technically, only the hot end differentiates integrated mills from mini-mills. However, the differing technological approaches to molten steel imply different scale efficiencies. See Mini Mills.
Integrated Steel Producer
A steel company which manufactures solid steel products; starts with raw materials such as iron ore, flux, etc, to make molten iron; converts the molten iron to liquid steel in the steel making furnaces and processes liquid to solid steel products.
Inter Annealed Wire
Wire drawn to an intermediate stage, annealed and drawn to the size required.
Inter-Chemical Gauge
Wet film thickness can also be measured using an Inter-chemical Gauge. A graduated circular cam is rolled against the plate between two parallel rollers. The wet film thickness is then read directly on cam at demarcation of coating wetting the cam.
Intermediate Annealing
Annealing wrought metal at one or more stages during manufacture and before final thermal treatment.
Intermediate Temper
A cold rolled hardness range specified with a 15-point Rockwell B spread. See Quarter Hard Temper and Half-Hard Temper.
Internal Cleanliness
Measure of number and types of non-metallic inclusions such as oxides, sulfides or silicates.
Interstitial Free Steel
A recently developed sheet steel product with very low carbon levels that is used primarily in automotive deep-drawing applications. Interstitial Free Steel’s improved ductility (drawing ability) is made possible by vacuum degassing.
Interrupted Aging
Aging at two or more temperatures by steps and cooling to room temperature after each step. Compare with progressive aging and step aging.
Interrupted Quenching
Quenching in which the metal object being quenched is removed from the quenching medium while the object is at a temperature substantially higher than that of the quenching medium.
IPM (In-Process Material)
An identifiable piece of steel; can be a slab, coil, or a bundle of sheets, or several slit mults banded together.
Iron Carbide
One of several substitutes for high-quality, low-residual scrap for use in electric furnace steel making. Iron carbide producers use natural gas to reduce iron ore to iron carbide.
Iron Notch
The opening for removing the liquid iron from the blast furnace. The opening on the inside of the furnace is larger than that on the outside so that the tapping hole can be drilled horizontally or at different angles. Although most of the older furnaces had only one iron notch, modern large blast furnaces have two or three and a few very larger ones have four.
Iron Ore
Mineral containing enough iron to be a commercially viable source of the element for use in steel making. Except for fragments of meteorites found on Earth, iron is not a free element; instead, it is trapped in the earth’s crust in its oxidized form. It is of two types : containing ferric oxide (Hematite) or ferro-ferric oxide (Magnetite).
Iron-Zinc Alloy Coating
See Galvanized Steel.
ISO Codes
The codes that designate the amount of contamination in the oil.
Isolate (Isolation)
To remove a boiler, or any particular part or system of a boiler, form service by closing the manual valves.
Isothermal Annealing
It is a type of full annealing in which the steel first is cooled to the temperature at which it is desired to have transformation occur, at a rate sufficiently rapid to prevent any structural change above that temperature. The steel then is held at the selected temperature for the time necessary to complete such transformation.
Isotropy
A term indicating equal physical or mechanical properties in all directions within a material.