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.