AISI | Steel Glossary P-T

Everything You Always Wanted to Know About Steel…But Were Afraid to Ask - December 2004

Michelle Applebaum Research provides this collection of terms and concepts used in our research, company and industry reports, and other steel publications as an invaluable tool for those in the steel industry.

Reproduction of all or part of this glossary is specifically prohibited without the written consent of the author.

The ultimate earnings level of a company at the top of the business cycle. This is the expected profit during the time of the highest commodity demand and the strongest product pricing.

Fine particles of iron ore mixed with bonding clay and roasted into hard round balls for blast furnace feed.

Process that cleans a steel coil of its rust, dirt and oil so that further work can be done to the metal.

When hot-rolled coils cool, rust forms on the unprotected metal; often coils are stored or transported while exposed to outside air and water.

Through a continuous process, the steel is uncoiled and sent through a series of hydrochloric acid baths that remove the oxides (rust). The steel sheet is then rinsed and dried.

The name for the melted iron produced in a blast furnace, containing a large quantity of carbon (above 1.5%). Named long ago when molten iron was poured through a trench in the ground to flow into shallow earthen holes, the arrangement looked like newborn pigs suckling. The central channel became known as the “sow,” and the molds were “pigs.”

A structural steel product with edges designed to interlock; used in the construction of cofferdams or riverbank reinforcement.

Technically a tube is used to transport fluids or gases. However, pipe and tube are often used interchangeably in steel lexicon, with a given label applied primarily as a matter of historical use.

Sheet steel with a width of more than eight inches, with a thickness ranging from one quarter of an inch to more than one foot (see Sheet Steel).

Fabrication technology in which fine metallic powder is compacted under high pressure and then heated at a temperature slightly below the melting point to solidify the material. Primary users of powder metal parts are auto, electronics and aerospace industries.

A small group of stainless steels with high chromium and nickel content, with the most common types having characteristics close to those of martensitic (plain chromium stainless class with exceptional strength) steels. Heat treatment provides this class with its very high strength and hardness. Applications for PH stainless steels include shafts for pumps and valves as well as aircraft parts.

Involves sawing plate (primary aluminum plate products) into square or rectangular shapes to tolerances as close as 0.003 of an inch.

A blast furnace enhancement to reduce an integrated mill’s reliance on coke (because of environmental problems with its production). Up to 30% of the coke charged into the blast furnace can be replaced by this talcum-like coal powder, which is injected through nozzles at the bottom of the furnace.

The cutting of holes into carbon steel beams or plates by pressing or welding per customer specifications.

Modified Basic Oxygen Furnace in which the oxygen and other gases are blown in from the bottom, rather than from the top. While the Q-BOP stirs the metal bath more vigorously, allowing for faster processing, the design produces essentially the same steel grades as the top-blowing basic oxygen furnace. Today’s state-of-the-art furnace design combines the previous technologies: 60% of the oxygen is blown from above, with the rest blown through the bottom of the vessel.

The testing required for a new process adopted to make certain grades of steel with exacting end uses. In order for the process to become qualified, the steel made by the process must be tested.

A process of hardening a ferrous alloy of suitable composition by heating within or above the transformation range and cooling at a rate sufficient to increase the hardness substantially. The process usually involves the formation of martensite.

Either natural gas or coal can be used to remove the oxygen from iron ore in order to produce a scrap substitute. In gas-based processes, the iron ore is heated in a vessel as reformed natural gas passes through. In coal-based processes, iron ore is combined with gasified or ground coal and heated. The oxygen in the ore combines with carbon and hydrogen in the gas or coal, producing reduced, or metallic, iron.

Heat-resistant brick. Because its melting point is well above the operating temperatures of the process, refractory bricks line most steelmaking vessels that come in contact with molten metal, like the walls of the blast furnace, sides of the ladles, and inside of the BOF.

A commodity-grade steel used to strengthen concrete in highway and building construction.

The process of replacing the refractory lining of a liquid steel vessel. Once it wears out, the brick lining of a furnace must be cooled, stripped, and replaced. This maintenance can be significant because a blast furnace reline may require up to three months to complete.

The impurities in mini-mill steel as the result of the mix of metals entering the process dissolved in obsolete scrap. Residuals are key concerns regarding the mini-mills’ recent entry into the flat-rolled market, where high residuals can leave sheet steel too brittle for customer use.

The stand of rolls used to reduce steel sheet or plate by passing the steel back and forth between the rolls; the gap between the rolls is reduced after each pass.

Round, thin semi-finished steel length that is rolled from a billet and coiled for further processing. Rod is commonly drawn into wire products or used to make bolts and nails. Rod trains (rolling facilities) can run as fast as 20,000 feet per minute — more than 200 miles an hour.

Mill stands place considerable pressure on slabs, blooms and coils to further process the material. There are two general ways of applying the force to the steel — screw and hydraulic systems.

This older method used the basic principle of the screw to adjust the space between the mill rolls. Because metal touches metal, these configurations will wear down over time and can cause quality problems.

This modern system uses fluid pressure to rapidly adjust the roll spacing several times per second. These minute, instantaneous adjustments allow for superior gauge tracking and higher quality products.

Any of the mills in which metal undergoes a rolling process. These include the slabbing mill, hot roll mills, cold roll mills, SR mills, and DR mills.

Any operating unit that reduces gauge by application of loads through revolving cylindrical rolls; operation can be hot or cold. The elevated temperature rolling mill is the Hot Mill and is capable of reducing the gauge of a slab 92-99%.

The first rolling stand through which metal passes during hot rolling. Once reduced by the roughing stands, the metal continues on to the finishing stands where smoother rolls with a smaller gap are used to complete the hot roll process.

Produces various sizes and shapes of aluminum plate according to customer-supplied drawings through the use of CNC controlled machinery.

Ferrous (iron-containing) material that generally is remelted and recast into new steel. Integrated steel mills use scrap for up to 25% of their basic oxygen furnace charge; 100% of the mini-mills’ raw material for their electric furnaces generally is scrap.

Waste steel that is generated from within the steel mill, through edge trimming and rejects. It normally is sent directly back to the furnace.

Excess steel that is trimmed by the auto and appliance stampers and auctioned to scrap buyers as factory bundles. This is a high-quality scrap as the result of its low-residual content and consistent chemistry.

Iron-bearing items such as old automobiles; household appliances; farm, office, and industrial equipment; ships and railroad cars; buildings and bridges that have completed their useful life which can be recovered from the junkyard and remelted. The residual impurity of such scrap normally relegates obsolete scrap to the mini-mills (see No. 1 Heavy Melt).

Raw material that can be charged in place of scrap in electric arc furnaces and basic oxygen furnaces. Scrap substitutes include, among others, DRI, HBI, iron carbide, and pig iron.

An air pollutant device that reduces the temperature of an emission – a liquid spray is used to remove pollutants from a gas stream by absorbtion or chemical reaction.

Pipe made from a solid billet, which is heated, then rotated under extreme pressure. This rotational pressure creates an opening in the center of the billet, which is then shaped by a mandrel to form pipe.

Steel that does not meet the original customer’s specifications because of a defect in its chemistry, gauge or surface quality. Mills must search to find another customer (that can accept the lower quality) to take the off-spec steel at a discount. While secondary will not affect the reported yield, margins will suffer.

Steel shapes — for example, blooms, billets, or slabs — that later are rolled into finished products such as beams, bars, or sheet.

Compact mill used for rolling cold coils of stainless steel in order to make the steel thinner, smoother, and stronger.

To control the thickness of steel better at lower capital cost, and to roll thinner sheets and strips.

Stainless steel sheet or strip passes between a matching pair of small work rolls with extremely smooth surfaces, heavily reinforced by clusters of back-up rolls. The rolls reduce the steel to the desired thickness.

A catchall name for an operation that buys steel, often processes it in some way and then sells it in a slightly different form. A service center is distinguished from an end-user by the fact that, unlike an end-user, a service center sells steel, not a fabricated product. Service centers are manufacturers to the extent that they add labor to steel by providing a service.

Rolling, heating, and quenching steel sheets often affect the dimensions of the steel. Levelers, temper mills, and edge trimmers rework the processed steel to match customer specifications.

If the edges of sheet and strip are not controlled during reduction, they must be trimmed parallel by shears. This process may be performed by either the steel mill or steel processor to match customer needs.

Thin, flat-rolled steel. Coiled sheet steel accounts for nearly one-half of all steel shipped domestically and is created in a hot-strip mill by rolling a cast slab flat while maintaining the side dimensions. The malleable steel lengthens to several hundred feet as it is squeezed by the rolling mill.

The most common differences among steel bars, strip, plate, and sheet are merely their physical dimensions of width and gauge (thickness).

Fist-sized, homogenous pieces of old automobile hulks. After cars are sent through a shredder, the recyclable steel is separated by magnets. Mini-mills consume shredded scrap in their electric arc furnace operations.

A type of specialty steel created by introducing silicon during the steelmaking process. Electrical steel exhibits certain magnetic properties, which make it optimum for use in transformers, power generators, and electric motors.

The metal’s grain runs parallel within the steel, permitting easy magnetization along the length of the steel. Although grain-oriented steel may be twice as expensive to produce, its magnetic directional characteristics enable power transformers, made from this metal, to absorb less energy during operation.

Because there is no preferential direction for magnetization, non-grain-oriented steel is best used in rotating apparatus such as electric motors.

A process that combines iron-bearing particles, once recovered from environmental control filters, into small pellets. Previously, these materials were too fine to withstand the air currents of the smelting process and were thrown away. The iron is now conserved because the chunks can be charged into the blast furnace (see Agglomerating Processes).

Steel that is the entry material to a pipe mill. It resembles hot-rolled strip, but its properties allow for the severe forming and welding operations required for pipe production.

The most common type of semi-finished steel. Traditional slabs measure ten inches thick and 30–85 inches wide (and average about 20 feet long), while the output of the recently developed “thin-slab” casters is approximately two inches thick. Subsequent to casting, slabs are sent to the hot-strip mill to be rolled into coiled sheet and plate products.

The impurities in a molten pool of iron. Flux such as limestone may be added to foster the congregation of undesired elements into a slag. Because slag is lighter than iron, it will float on top of the pool, where it can be skimmed.

Cutting a sheet of steel into narrower strips to match customer needs. Because steel mills have limited flexibility as to the widths of the sheet that they produce, service centers normally will cut the sheet for the customer.

Finish achieved when zinc is allowed to “freeze” naturally on the sheet – galvanize. Achieved by adding antimony to the hot dip bath.

SBQ represents a wide variety of higher quality carbon and alloy bars that are used in the forging, machining, and cold-drawing industries for the production of automotive parts, hand tools, electric motor shafts, and valves. SBQ generally contains more alloys than merchant quality and commodity grades of steel bars, and is produced with more precise dimensions and chemistry.

Category of steel that includes electrical (see Silicon Electrical Steel), alloy (see Alloy Steel), stainless (see Stainless Steel), and tool steels (see Tool Steels).

Refers to a wide variety of high-quality custom-made tubular products requiring critical tolerances, precise dimensional control and special metallurgical properties. Specialty tubing is used in the manufacture of automotive, construction, and agricultural equipment, and in industrial applications such as hydraulic cylinders, machine parts, and printing rollers. Because of the range of industrial applications, the market typically follows general economic conditions.

The term for grades of steel that contain more than 10% chromium, with or without other alloying elements. Stainless steel resists corrosion, maintains its strength at high temperatures, and is easily maintained. For these reasons, it is used widely in items such as automotive and food processing products, as well as medical and health equipment. The most common grades of stainless steel are:

The most commonly specified austenitic (chromium-nickel stainless class) stainless steel, accounting for more than half of the stainless steel produced in the world. This grade withstands ordinary corrosion in architecture, is durable in typical food processing environments, and resists most chemicals. Type 304 is available in virtually all product forms and finishes.

Austenitic (chromium-nickel stainless class) stainless steel containing 2%–3% molybdenum (whereas 304 has none). The inclusion of molybdenum gives 316 greater resistance to various forms of deterioration.

Ferritic (plain chromium stainless category) stainless steel suitable for high temperatures. This grade has the lowest chromium content of all stainless steels and thus is the least expensive.

The most widely used martensitic (plain chromium stainless class with exceptional strength) stainless steel, featuring the high level of strength conferred by the martensitics. It is a low-cost, heat-treatable grade suitable for non-severe corrosion applications.

The most widely used ferritic (plain chromium stainless category) stainless steel, offering general-purpose corrosion resistance, often in decorative applications.

A technique used to predict when a steelmaking function’s quality may deteriorate. By tightly monitoring the product’s variance from specifications, the operator can determine when to apply preventative maintenance to a machine before any low-quality (secondary) steel is produced.

A reversing steel sheet reduction mill with heated coil boxes at each end. Steel sheet or plate is sent through the rolls of the reversing mill and coiled at the end of the mill, reheated in the coil box, and sent back through the Steckel stands and recoiled. By reheating the steel prior to each pass, the rolls can squeeze the steel thinner per pass and impart a better surface finish.

The amount of steel used per unit of gross domestic product. Intensity reflects the secular demand for steel, as opposed to cyclical demand. The amount of steel used in vehicles and the popularity of alternative materials affect the intensity, or how much steel is needed per unit produced. The state of the economy, however, determines the number of units.

Consumer products such as automobiles and appliances that, because so much of their weight is from steel, exhibit a high demand correlation with steel.

End-of-period material stocks reported by the Metals Service Center Institute (MSCI).

Banding and packaging material that is used to close and reinforce shipping units, such as bales, boxes, cartons, coils, crates, and skids.

Properties related to the ability of steel to oppose applied forces. Forms of strength include withstanding imposed loads without a permanent change in shape or structure and resistance to stretching.

Slow growth of cracks in stainless steel caused by the combined effect of mechanical stress and exposure to a corrosive environment.

Thin, flat steel that resembles hot-rolled sheet, but it is normally narrower (up to 12 inches wide) and produced to more closely controlled thicknesses. Strip also may be cut from steel sheet by a slitting machine (see Sheet Steel).

Steel product group that includes I-beams, H-beams, wide-flange beams, and sheet piling. These products are used in the construction of multi-story buildings, industrial buildings, bridge trusses, vertical highway supports, and riverbank reinforcement.

Raw material used as an input for steel processing: For example, hot-rolled steel is the substrate for cold-rolling operations.

An alloy, usually based on nickel, cobalt, or iron, developed for high temperature service where relatively severe mechanical stressing is encountered and where high surface stability is frequently required.

Stainless steel alloys with significant additions of chromium, nickel, molybdenum, or copper. Super stainless steel is used in chemical processing, petroleum refining, marine, heat treating, pollution, and waste control industries where there are requirements for extra corrosion protection, strength, or heat resistance.

A resolution of an unfair trade dispute that can suspend further proceedings in an unfair trade suit. The U.S. government, in consultation with the domestic industry, can enter into such an agreement with the foreign industry.

Natural mineral containing less than 30% iron. It is the primary ore used in blast furnaces.

Domestic supplies of iron-rich ores (greater than 50% iron) were largely depleted in the 1940s, so integrated steel companies now process the lower grade taconite to make it useful.

A section of sheet or strip that is cut-to-length and trimmed to match specifications for the manufacturer’s stamping design for a particular part. Because excess steel is cut away (to save shipping costs), all that remains for the stamper is to impart the three-dimensional shape with a die press (see Blanking).

A type of cold-rolling mill, the tandem mill imparts greater strength, a uniform and smoother surface, and reduced thickness to the steel sheet. Unlike the original single-stand mills, a tandem mill rolls steel through a series of rolls (generally three to five in a row) to achieve a desired thickness and surface quality.

An exotic alloy having high corrosion resistance; used for medical implants, chemical process equipment, and aerospace engine components.

Involves splitting metal beams. Tee straightening is the process of straightening split beams.

A type of cold-rolling mill, usually with only one or two stands, that finishes cold-rolled, annealed sheet steel by improving the finish or texture to develop the required final mechanical properties. By changing the rolls of the temper mill, steel can be shipped with a shiny, dull, or grooved surface.

Sheet steel coated with a mixture of lead and tin. Terne principally is used in the manufacture of gasoline tanks, although it also can be found in chemical containers, oil filters, and television chassis.

Continuous tin-plating facility to produce tin mill steel sheet to be used in food and beverage cans and other containers.

A plating process whereby the molecules from the positively charged tin or chromium anode attach to the negatively charged sheet steel. The thickness of the coating is readily controlled through regulation of the voltage and speed of the sheet through the plating area.

Chromium-coated steel. Because it is used in food cans just like tin plate, it ironically is classified as a tin mill product. Tin-free steel is easier to recycle because tin will contaminate scrap steel in even small concentrations.

Thin sheet steel with a very thin coating of metallic tin. Tin plate is used primarily in canmaking.

Titanium and its alloys have very high strength-to-weight ratios. At normal temperatures, they have high resistance to corrosion. Used primarily in aerospace and chemical processing applications.

A customer’s specifications can refer to dimensions or to the chemical properties of steel ordered. The tolerance measures the allowable difference in product specifications between what a customer orders and what the steel company delivers. There is no standard tolerance because each customer maintains its own variance objective. Tolerances are given as the specification, plus or minus an error factor; the smaller the range, the higher the cost.

The act of processing steel for a fee (“toll”). Owners of the steel sheet may not possess the facilities to perform needed operations on the material (or may not have the open capacity). Therefore, another steel mill or service center will slit, roll, coat, anneal, or plate the metal for a fee.

Short (Net) Ton: 2,000 pounds. Normal unit of statistical raw material input and steel output in the United States.

When referring to OCTG, tubing is a separate pipe used within the casing to conduct the oil or gas to the surface. Depending on conditions and well life, tubing may have to be replaced during the operational life of a well.

The shallow refractory-lined basin on top of the continuous caster. It receives the liquid steel from the ladle, prior to the cast, allowing the operator to precisely regulate the flow of metal into the mold.

Include tungsten and tungsten carbide powders, sintered tungsten carbide products and cutting tools for the metalworking, mining, oil and gas, and other industries requiring tools with extra hardness.

Type of furnace whereby stock to be heated is placed upon cars, which are then pushed or pulled slowly through the furnace.

Grinds one or all six sides of a small square or rectangular piece of aluminum plate into close tolerance.

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