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Agglomerating Processes

Fine particles of limestone (flux) and iron ore are difficult to handle and transport because of dusting and decomposition. The powdery material is therefore usually processed into larger pieces. The raw material’s properties determine the technique that is used by mills.

Baked particles that stick together in roughly one-inch chunks. Normally used for iron ore dust collected from the blast furnaces.

Iron ore or limestone particles are rolled into little balls in a balling drum and hardened by heat.

Small lumps are formed by pressing material together. Hot Briquetted Iron (HBI) is a concentrated iron ore substitute for scrap for use in electric furnaces.

A change in the properties of certain metal and alloys (such as steel) that occurs at ambient or moderately elevated temperatures after a hot working heat treatment or cold working operation. Typical properties impacted are: hardness, yield strength, tensile strength, ductility, impact value, formability, magnetic properties, etc.
AISI (American Iron and Steel Institute)
An association of North American companies that mine iron ore and produce steel products. There are 31 member companies and 118 associate members, which include both suppliers and customers that distribute, process, or consume steel. The AISI represents the interests of Canada, Mexico, and the United States.
Alloying Element
Any metallic element added during the melting of steel or aluminum for the purpose of increasing corrosion resistance, hardness, or strength. The metals used most commonly as alloying elements in stainless steel include chromium, nickel, and molybdenum.
Alloy Steel
An iron-based mixture is considered to be an alloy steel when manganese is greater than 1.65%, silicon over 0.5%, copper above 0.6%, or other minimum quantities of alloying elements such as chromium, nickel, molybdenum, or tungsten are present. An enormous variety of distinct properties can be created for the steel by substituting these elements in the recipe.
Aluminum Killed Steel (Special Killed)
Steel deoxidized with aluminum in order to reduce the oxygen content to a minimum so that no reaction occurs between carbon and oxygen during solidification.

A heat or thermal treatment process by which a previously cold-rolled steel coil is made more suitable for forming and bending. The steel sheet is heated to a designated temperature for a sufficient amount of time and then cooled.

The bonds between the grains of the metal are stretched when a coil is cold-rolled, leaving the steel brittle and breakable. Annealing “recrystallizes” the grain structure of steel by allowing for new bonds to be formed at the higher temperature.

There are two ways to anneal cold-rolled steel coils: batch and continuous.

a. Batch (Box) Three to four coils are stacked on top of each other, and a cover is placed on top for up to 3 days, then b. heated in a non-oxygen atmosphere (to prevent rust) and slowly cooled.
Continuous. Normally part of a coating line, the steel is uncoiled and run through a series of vertical loops within a heater. The temperature and cooling rates are controlled to obtain the desired mechanical properties for the steel.

Apparent Supply
Derived demand for steel using AISI reported steel mill shipments plus Census Bureau reported imports, less Census Bureau reported exports. Domestic market share percentages are based on this figure, which does not take into account any changes in inventory.
Argon-Oxygen Decarburization (AOD)

A process for further refinement of stainless steel through reduction of carbon content.

The amount of carbon in stainless steel must be lower than that in carbon steel or lower alloy steel (i.e., steel with alloying element content below 5%). While electric arc furnaces (EAF) are the conventional means of melting and refining stainless steel, AOD is an economical supplement, as operating time is shorter and temperatures are lower than in EAF steelmaking. In addition, using AOD for refining stainless steel increases the availability of the EAF for melting purposes.

Molten, unrefined steel is transferred from the EAF into a separate vessel. A mixture of argon and oxygen is blown from the bottom of the vessel through the melted steel. Cleaning agents are added to the vessel along with these gases to eliminate impurities, while the oxygen combines with carbon in the unrefined steel to reduce the carbon level. The presence of argon enhances the affinity of carbon for oxygen and thus facilitates the removal of carbon.


A natural reduction in work force as a result of resignations, retirements, or death.

Most unionized companies cannot unilaterally reduce their employment levels to cut costs, so management must rely on attrition to provide openings that it, in turn, does not fill. Because the median ages of work forces at the integrated mills may be more than 50, an increasing number of retirements may provide these companies with added flexibility to improve their competitiveness.


The largest category of stainless steel, accounting for about 70% of all production. The austenitic class offers the most resistance to corrosion in the stainless group, owing to its substantial nickel content and higher levels of chromium. Austenitic stainless steels are hardened and strengthened through cold working (changing the structure and shape of steel by applying stress at low temperature) instead of by heat treatment. Ductility (ability to change shape without fracture) is exceptional for the austenitic stainless steels. Excellent weldability and superior performance in very low-temperature services are additional features of this class.

Applications include cooking utensils, food processing equipment, exterior architecture, equipment for the chemical industry, truck trailers, and kitchen sinks.

The two most common grades are type 304 (the most widely specified stainless steel, providing corrosion resistance in numerous standard services) and type 316 (similar to 304, with molybdenum added, to increase opposition to various forms of deterioration).

Auto Stamping Plant
A facility that presses a steel blank into the desired form of a car door or hood, for example, with a powerful die (pattern). The steel used must be ductile (malleable) enough to bend into shape without breaking.
Automatic Gauge Control
Using hydraulic roll force systems, steelmakers have the ability to control precisely their steel sheet’s gauge (thickness) while it is traveling at more than 50 miles per hour through the cold mill. Using feedback or feed-forward systems, a computer’s gap sensor adjusts the distance between the reduction rolls of the mill 50–60 times per second. These adjustments prevent the processing of any off-gauge steel sheet.
An air pollutant control device used to trap particles by filtering gas streams through large cloth or fiberglass bags.
Bake Hardenable Steel
A cold-rolled, low-carbon sheet steel used for automotive body panel applications. Because of special processing, the steel has good stamping and strength characteristics, and, after paint is baked on, improved dent resistance.
Basic Oxygen Furnace (BOF)

A pear-shaped furnace, lined with refractory bricks, that refines molten iron from the blast furnace and scrap into steel. Up to 30% of the charge into the BOF can be scrap, with hot metal accounting for the rest.

BOFs, which can refine a heat (batch) of steel in less than 45 minutes, replaced open-hearth furnaces in the 1950s; the latter required five to six hours to process the metal. The BOF’s rapid operation, lower cost, and ease of control give it a distinct advantage over previous methods.

Scrap is dumped into the furnace vessel, followed by the hot metal from the blast furnace. A lance is lowered from above, through which blows a high-pressure stream of oxygen to cause chemical reactions that separate impurities as fumes or slag. Once refined, the liquid steel and slag are poured into separate containers.

Bar Turning
Involves machining a metal bar into a smaller diameter.
Long steel products that are rolled from billets. Merchant bar and reinforcing bar (rebar) are two common categories of bars, where merchants include rounds, flats, angles, squares, and channels that are used by fabricators to manufacture a wide variety of products such as furniture, stair railings, and farm equipment. Rebar is used to strengthen concrete in highways, bridges, and buildings.
The forming of metals into various angles.
A semi-finished steel form that is used for “long” products: bars, channels or other structural shapes. A billet is different from a slab because of its outer dimensions; billets are normally two to seven inches square, while slabs are 30 inches to 80 inches wide and two inches to ten inches thick. Both shapes are generally continually cast, but they may differ greatly in their chemistry.
Black Plate
Cold-reduced sheet steel, 12 inches to 32 inches wide, that serves as the substrate (raw material) to be coated in the tin mill.
Blast Furnace
A towering cylinder lined with heat-resistant (refractory) bricks, used by integrated steel mills to smelt iron from iron ore. Its name comes from the “blast” of hot air and gases forced up through the iron ore, coke, and limestone that load the furnace.
An early step in preparing flat-rolled steel for use by an end user. A blank is a section of sheet that has the same outer dimensions as a specified part (such as a car door or hood), but that has not yet been stamped. Steel processors may offer blanking for their customers to reduce their labor and transportation costs; excess steel can be trimmed prior to shipment.
A semi-finished steel form, with a rectangular cross-section that is more than 8”. This large cast steel shape is broken down in the mill to produce the familiar I-beams, H-beams, and sheet piling. Blooms are also part of the high-quality bar manufacturing process: Reduction of a bloom to a much smaller cross-section can improve the quality of the metal.
An accident caused by the failure of the walls of the hearth of the blast furnace, resulting in liquid iron or slag (or both) flowing uncontrolled out of the blast furnace.
Brownfield Expansion
A “brownfield” contrasts to a “greenfield” (or a facility new from the ground up). A brownfield expansion means adding on to an existing facility.
The very subtle ridge on the edge of strip steel left by cutting operations such as slitting, trimming, shearing, or blanking. For example, as a steel processor trims the sides of the sheet steel parallel or cuts a sheet of steel into strips, its edges will bend with the direction of the cut (see Edge Rolling).
Scrap consisting of sheet clips and stampings from metal production. This term arose from the practice of collecting the material in bushel baskets through World War II.
Butt-Weld Pipe
The standard pipe used in plumbing. Heated skelp is passed continuously through welding rolls, which form the tube and squeeze the hot edges together to make a solid weld.
a. Camber is the deviation of a side edge from a straight edge. Measurement is taken by placing a straight edge on the concave side of a sheet and measuring the distance between the sheet edge and the straight edge in the center of the arc. Camber is caused by one side being elongated more than the other.
b. The hook or dogleg near the ends of a coil.
Camber Tolerances
Camber is the deviation from edge straightness. Maximum allowable tolerance of this deviation of a side edge from a straight line are defined in ASTM Standards.

Normal ability to produce metals in a given time period. This rating should include maintenance requirements, but because such service is scheduled to match the needs of the machinery (not those of the calendar), a mill might run at more than 100% of capacity one month and then fall well below rated capacity as maintenance is performed.

Engineered Capacity
The theoretical volume of a mill or smelter, given its constraints of raw material supply and normal working speed.

“True” Capacity
Volume at full utilization, allowing for the maintenance of equipment and reflecting current material constraints. (Bottlenecks of supply and distribution can change over time — capacity will expand or reduce.)

Carbon Steel
Steel that has properties made up mostly of the element carbon and which relies on the carbon content for structure. Most of the steel produced in the world is carbon steel.
Casing is the structural retainer for the walls of oil and gas wells, and accounts for 75% (by weight) of OCTG shipments. Casing is used to prevent contamination of both the surrounding water table and the well itself. Casing lasts the life of a well and is not usually removed when a well is closed.
The process of pouring molten metal into a mould so that the cooled, solid metal retains the shape of the mould.
Process to directly cast molten steel into a final shape and thickness without additional hot or cold rolling. This reduces capital investment, energy, and environmental cost.
The act of loading material into a vessel. For example, iron ore, coke, and limestone are charged into a Blast Furnace; a Basic Oxygen Furnace is charged with scrap and hot metal.
The chemical composition of steel indicating the amount of carbon, manganese, sulfur, phosphorous and a host of other elements.
Chromium (Cr)
An alloying element that is the essential stainless steel raw material for conferring corrosion resistance. A film that naturally forms on the surface of stainless steel self-repairs in the presence of oxygen if the steel is damaged mechanically or chemically, and thus prevents corrosion from occurring.

Method of applying a stainless steel coating to carbon steel or lower alloy steel (i.e., steel with alloying element content below 5%).

To increase corrosion resistance at lower initial cost than exclusive use of stainless steel.

By 1) welding stainless steel onto carbon steel; 2) pouring melted stainless steel around a solid carbon steel slab in a mold; or 3) placing a slab of carbon steel between two plates of stainless steel and bonding them by rolling at high temperature on a plate mill.

The process of covering steel with another material (tin, chrome, and zinc), primarily for corrosion resistance.
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