Dictionary for stainless steel sector, with many phrases and terms that are unique to mining especially to stainless steel industry.
A form of hydrogen embrittlement which may be induced in some metals by acid treatment such as pickling.
In a metal or alloy, a change in properties that generally occurs slowly at room temperature and more rapidly at higher temperatures.
An element added to a metal to effect changes in property, and which remains within the metal.
Heating to and holding at a suitable temperature and then cooling at a suitable rate, for such purposes as reducing hardness, improving, machinability, facilitating cold working, producing a desired microstructure, or obtaining desired mechanical, physical or other properties. Annealing is a broad term covering such thermal treatments as full annealing, normalizing, etc. When applying to ferrous alloys, the term “annealing,” without qualification, implies full annealing.
Alloy steels have enhanced properties due to the larger proportion of elements such as manganese and silicon present in carbon steels.
The heat treatment process by which steel products are reheated to a suitable temperature in order to remove stresses from previous processing and to soften them and/or improve their machinability and cold forming properties.
The sum of net industry shipments within a given country or region, plus its imports and minus its exports.
A segregated structure of nearly parallel bands aligned in the direction of working.
A finished steel product, commonly in flat, square, round or hexagonal shapes. Rolled from billets, bars are produced in two major types: merchant and special.
The decarbonized layer just beneath the scale that results from heating steel in an oxidizing atmosphere.
A process for making steel by blowing air through molten pig iron containing in a refractory lined vessel so as to remove by oxidation most of the carbon, silicon and manganese.
A solid semi-finished round or square product that has a minimum width or thickness of 1- ½ inches and the cross-sectional area varies from 2-¼ to 36 square inches.
Box annealing or pot annealing ferrous alloy sheet, strip or wire. See box annealing.
A vertical shaft type furnace used for reducing iron ore to pig iron in a continuous operation. The furnace is charged from the top, the air blast entering the bottom.
A defect produced by gas bubbles.
A hole in a casting or a weld caused by gas entrapped during solidification.
Heating hot rolled ferrous sheet in an open furnace to a temperature within the transformation range and then cooling in air, in order to soften the metal. The formation of a bluish oxide on the surface.
Brittleness occurring in some steels after being heated within the range of 300 to 650° Fahrenheit and more especially if the steel is worked at the elevated temperature. Killed steels are virtually free of this kind of brittleness.
Annealing steel by heating in a sealed container under conditions that minimize oxidation.
Annealing in a protective medium to prevent discoloration of the surface.
Steel sheet of high dimensional precision, in simple or complex form, sometimes multi-thickness, constituting principally automobile body parts.
A furnace used in integrated steelmaking in which coke and iron ore react together under a hot air flow to form liquid hot metal, also called pig iron.
Steel is classed as carbon steel when no minimum content is specified or required for aluminum, boron, chromium, cobalt, columbium, molybdenum, nickel, titanium, tungsten, vanadium or zirconium, or any other element added to obtain a desired ally effect; when the specified minimum for copper does not exceed 0.40%; or when the maximum content specified for maganese does not exceed 1.65%; silicon .60%; copper .60%.
Introducing carbon into a solid ferrous ally by holding above the critical temperature in contact with a suitable carbonaceous material, which may be a solid, liquid or gas.
In a ferrous alloy, the outer portion that has been made harder than the inner portion, or core, by carburizing and hardening.
Removing seams and other surface defects in metals manually with chisel or gouge or by a continuous machine, before further processing.
Planes along which crystals fracture more easily.
A place in metal where two portions of the metal in either a molten or plastic condition have failed to unite into a solid mass.
Plastic deformation of a metal at a temperature low enough to insure strain hardening.
The center portion of a piece of steel which may be of different chemical composition than the outside, as in the case of carburized parts, or which may have different mechanical properties than the outside due to the failure of penetration of heat treatment effect.
The defective ends of a rolled or forged product which are cut off and discarded.
Introducing carbon and nitrogen into a solid ferrous ally by holding above the critical temperature in contact with molten cyanide salt of suitable composition.
The primary fuel used by integrated iron and steel producers.
Steel is coated by a heat process, or through electrolysis, with a layer to protect the metal base against corrosion. The most commonly used coating material is zinc which can be applied either using the heat process (hot-dip galvanising) or using electrolysis (electro-galvanising). An organic coating (paint, plastic) can also be deposited on the zinc layer.
A finished steel product such as sheet or strip which has been wound or coiled after rolling.
A form of carbonised coal burned in blast furnaces to reduce iron ore pellets or other iron-bearing materials iron.
Ovens where coke is produced. Coal is usually dropped into the ovens through openings in the roof, and heated by gas burning in flues in the walls within the coke oven battery. After heating for about 18 hours, the end doors are removed and a ram pushes the coke into a quenching car for cooling before delivery to the blast furnace.
Passing a sheet or strip that has previously been hot rolled and picked through cold rolls (below the softening temperature of the metal). Cold rolling makes a product that is thinner, smoother and stronger than can be made by hot rolling alone.
A process for solidifying steel in the form of a continuous strand rather than individual ingots. Molten steel is poured into open-bottomed, water-cooled moulds. As the molten steel passes through the mould, the outer shell solidifies.
Cold rolled coil (see cold rolling)
Steel in the first solid state after melting, suitable for further processing or for sale. Synonymous with raw steel.
The loss of carbon from the surface of a ferrous alloy as a result of heating in a medium that reacts with the carbon at the surface.
A misnomer for tempering. See tempering.
A group of processes for making iron from ore without exceeding the melting temperature. No blast furnace is needed.
Strictly speaking the elastic limit of a material is the producing a measurable change in length after the load is released. Owing to the difficulty of making a test to determine the true elastic limit, it is common practice to apply the load at a constant rate of increase and also measure the increase of length of the specimen at uniform load increments. The point, at which the increase in length of the specimen ceases to bear a direct ratio to the increase in load, is called the proportional limit. For commercial purposes the elastic limit and the proportional limit may be considered equal, although the elastic limit will usually be slightly higher than the proportional limit.
In tensile testing, the increase in the gage length, measured after fracture of the specimen within the gage length, usually expressed as a percentage of the original gage length.
Maximum stress to which material may be submitted without causing fatigue failure.
A steel consisting of nothing but pearlite (about .90 carbon)
ELECTRIC ARC FURNACE
A furnace for scrap-based steelmaking. Once the furnace is charged and covered, graphite electrodes are lowered through holes in the roof. The electric arc travelling between the electrodes and the metallic charge creates intense heat which melts the scrap. Alloying elements can be added during the process.
Specially manufactured cold rolled sheet and strip containing silicon, processed to develop definite magnetic characteristics for use by the electrical industry.
An alloy of iron that contains a sufficient amount of one or more other chemical elements to be useful as an agent for inducing these elements into a molten metal, usually steel.
A fibrous or woody appearing structure found in fractures of wrought metal, and generally indicating directional properties.
Temperature at which the hot working is finished.
A type that is produced by rolls with smooth surfaces and ranges of dimension, varying in thickness. The two major flat steel product categories are thin, flat products (between 1mm and 10mm in thickness) and plates (between 10mm and 200mm thick and used for large welded pipes, ship building, construction, major works and boilers).
Breaking a metal specimen and examining the fractured surface with the unaided eye or a low-power microscope to determine such things as composition, grain size, case depth, soundness or presence of defects.
Heating to above the critical temperature range followed by slow cooling through the range.
GRAIN GROWTH (coarsening)
An increase in the size of grains in polycrystalline metal, usually effected during heating at elevated temperatures.
Produced when hot or cold rolled sheet or strip is coated with zinc, either by the hot-dipping or electrolytic deposition processes. Zinc coating applied by the hot dip method is normally heavy enough to resist corrosion without additional protective coating. Materials electronically galvanised are not used for corrosion-resistant applications without subsequent chemical treatment and painting, except in mild corrosive conditions, due to the thin coating of zinc. Galvanise is a pure zinc coating. A special heat-treating process converts the pure zinc coating to a zinc/iron alloy coating, and the product is known as Galvanneal.
Increasing the hardness by suitable treatment, usually involving heating and cooling. When applicable, the following flame hardening, induction hardening, precipitation hardening and quench hardening.
Method of heating and cooling of finished metals or alloys to produce certain desirable properties and conditions.
Brittleness in metal in the hot forming range.
Deforming metal plastically at such a temperature and rate that strain hardening does not occur.
Hot dip galvanised (see galvanised steel)
HOT AND COLD ROLLING MILL
Hot-rolling mill: Equipment on which solidified steel preheated to a high temperature is continuously rolled between two rotating cylinders.
Cold rolling mill: Equipment that reduces the thickness of flat steel products by rolling the metal between alloy steel cylinders at room temperature.
Molten iron produced in the blast furnace.
Hot rolled coil (see hot rolling)
A steel having more than the eutectoid percentage (about .90) of carbon.
A steel having less than the eutectoid percentage (about .90) of carbon.
A test to determine the behavior of materials when subjected to high rates of loading, usually in bending, tension or torsion.
A casting suitable for working or remelting.
Commercially pure open-hearth iron.
A producer that converts iron ore into semi-finished or finished steel products. Traditionally, this process required coke ovens, blast furnaces, steelmaking furnaces and rolling mills. A growing number of integrated mills use the direct reduction process to produce sponge iron without coke ovens and blast furnaces.
The primary raw material in the manufacture of steel.
JOINT IMPLEMENTATION (JI)
Joint Implementation is the mechanism under the UN Framework Convention on Climate Change by which developed (Annex 1) countries can invest in emissions reduction projects in other developed countries. Each project is awarded with a number of Emission Reduction Units equal to the amount of emissions saved.
These are extra large H-profile structural steel sections. They are specified where there is a need for exceptional strengthor load bearing capability in buildings and other structures.
When used for horizontal load bearing they are referred to as jumbo beams, and as jumbo columns when applied in vertical load bearing duties.
Jumbo sections are rolled from blooms or beam blanks in a beam mill, and typically have a web depth of 500mm or more.
Steel deoxidized with a strong deoxidizing agent such as silicon or aluminum in order to reduce the oxygen content to such a level that no reaction occurs between carbon and oxygen during solidification.
This is steel that has been treated with a deoxidising agent such as aluminium or silicon while molten and prior to casting. The aim is to significantly lower or totally remove the steel’s oxygen content so that there is no gas formed during subsequent solidification. The resulting cast steel is non-porous and very homogeneous, and as either a flat or long product can undergo significant forming or drawing during subsequent processing.
A seamlike surface defect caused by folding over fins or sharp corners in hot metal and then rolling or forging them into the surface.
Weld made on overlapped edges of scarfed or beveled skelp to form tubing or pipe.
The process whereby conditions (temperature, pressure and chemistry) are controlled within the ladle of the steelmaking furnace to improve productivity in preceding and subsequent steps, as well as the quality of the final product.
Used by the steel industry to remove impurities from the iron made in blast furnaces. Limestone containing magnesium, called dolomite, is also sometimes used in the purifying process.
Used for transportation of gas, oil or water generally in a pipeline or utility distribution system.
Long products are used in all industrial sectors, particularly in the construction and engineering industries. The group makes heavy long products, light long products and wire-drawn products.
LOST TIME INJURY FREQUENCY RATE (LTIFR)
LITFR is the number of injuries which has resulted in an employee or contractor being away from work at least one day after the day it occurred, per million hours worked.
The structure of metals as revealed by examination of the etched surface of a polished specimen at a magnification not exceeding ten diameters.
Working metal through rolls, presses, hammers, etc., to change its shape, properties or structure.
MODULUS OF ELASTICITY
A measure of the rigidity of metal. Ratio of stress, within proportional limit, to corresponding strain. Specifically, the modulus obtained in tension or compression is Young’s modulus, stretch modulus or modulus of extensibility; the modulus obtained in torsion; the modulus covering the ratio of the mean normal stress to the change in volume is the bulk modulus. The tangent modulus and secant modulus are not restricted within the proportional limit; the former is the slope of the stress-strain curve at a specified point; the latter is the slope of a line from the origin to a specified point on the stress- strain curve. Also called “elastic modulus” and “coefficient of elasticity.”
Welded or seamless tubing produced in a large number of shapes to closer tolerances than other pipe.
A small non-integrated or semi-integrated steel plant, generally based on electric arc furnace steelmaking. Minimills produce rods, bars, small structural shapes and flat rolled products.
A structure in which the crystals of on constituent are surrounded by envelopes of another constituent which gives a network appearance to an etched test specimen.
Adding nitrogen by heating at a temperature below the critical in contact with some nitrogenous material.
Heating to about 100°F. above the critical temperature and cooling in still air to ordinary temperature.
Heating a metal or alloy to such a high temperature that its properties are impaired. When the original properties cannot be restores by further heat treating, by mechanical working or by a combination of working and heat treating, the overheating is know then as burning.
High carbon iron—made by reduction of iron ore in the blast furnace.
The central cavity formed by contraction in metal, especially in ingots, during solidification.
The maximum stress at which strain remains directly proportional to stress.
An enriched form of iron ore shaped into small balls.
A flat rolled product from slabs or ingots of greater thickness than sheet or strip.
Cooling rapidly from the hardening temperature by subjecting the part to the proper coolant such as oil, water, molten salt, molten lead, airblast, etc.
A stage in the process of making crude steel, during which the crude steel is further refined (i.e. most residual impurities are removed) and additions of other metals may be made before it is cast.
Equipment that reduces and transforms the shape of semi-finished or intermediate steel products by passing the material through a gap between rolls that is smaller than the entering materials.
Brittleness in metal in the hot forming range.
REDUCTION OF AREA
The decreased of cross-sectional area of a tension test-specimen at a point of rupture, expressed as percentage of original area.
Temperature at which the grain size and structure of the steel is refined, usually above the upper critical.
A low-carbon steel containing sufficient iron oxide to give a continuous evolution of carbon monoxide while the ingot is solidifying, resulting in a case or rim of metal virtually free of voids. Sheet and strip products made from the ingot have very good surface quality.
SBQ, or special bar quality, is a predominantly North American term to describe steel long products for more demanding processing or end-use applications than can be met by commodity grades. Elsewhere the term “engineering steels” is widely used.
The chemistry and production routes for SBQ are more complex than for merchant bar and other commodity grades, and they are generally machined, forged or cold drawn during subsequent processing.
The main application area is the automotive industry for engine, transmission, steering and suspension components, but these steels find widespread applications from hand tools to electric motors and in the petrochemicals and other industrial sectors.
On the surface of metal, an unwelded fold or lap, which appears as a crack, usually resulting from a defect obtained in casting or working.
SELF-HARDENING STEEL (Air Hardening)
A steel containing sufficient carbon and other alloying elements to harden fully during cooling in air or other gaseous mediums from a temperature above its transformation range. The term should be restricted to steels that are capable of being hardened by cooling in air in fairly large sections about two inches or more in diameter.
SINKHEAD OR HOT TOP
An insulated reservoir on top of an ingot mold holding excess molten metal which it feeds to the ingot proper when shrinkage occurs. Designed to prevent pipe.
Steel or iron plate from which pipe or tubing is made.
A piece of metal, intermediate between ingot and plate, with the width at least twice the thickness for rolling down into plates.
A primary mill which produces slabs.
Holding steel at fixed temperature long enough for a complete, uniform penetration of the heat.
Composite word derived for Solid Non-metallic IMpuritieS.
Cracking and flaking of the metal surface.
Prolonged heating at a temperature near the critical range followed by relatively slow cooling, causing the carbides to assume approximately a spherical shape.
Steel products such as billet, blooms and slabs. These products can be made by direct continuous casting of hot steel or by pouring the liquid steel into ingots, which are then hot rolled into semi-finished products.
A flat rolled product over 12 inches in width and of less thickness than plate.
Rolled sections with interlocking joints (continuous throughout the entire length of the piece) on each edge to permit being driven edge-to-edge to form continuous walls for retaining earth or water.
A plant in which iron ore is crushed, homogenised and mixed with limestone and coke breeze and then cooked (“sintered”) to form sinter which is the main ferrous component of blast furnace burden.
A process which combines ores too fine for efficient blast furnace use with flux stone. The mixture is heated to form clumps, which allow better draft in the blast furnace.
A semi-finished steel product obtained by rolling ingots on a rolling mill or processed through a continuous caster and cut into various lengths. The slab has a rectangular cross section and is used as a starting material in the production process of flat products, i.e. hot rolled coils or plates.
A by-product, containing inert materials from the ‘burden’ (the materials put into the blast furnace at the beginning of the steel making process), that is produced during the melting process.
The product of the direct reduction process. Also known as direct reduced iron (DRI).
This steel will tolerate continual deflection under load, but recover to its original form once the loading is removed. It is a medium carbon steel (0.4-0.95%) available both as a long product (bar, wire) or in flat form. High yield strength is important and the key alloying additions used to determine the steel’s final properties are silicon and manganese.
There is a considerable difference in the in-service requirements imposed on spring steels, with automotive engine valve springs an example of the top end of the performance range. These have to operate with precision at a rate of several thousand compression cycles per minute over a normal engine lifespan of several thousand hours.
Most springs are made from hardened and tempered steel, though to ease the manufacture of larger springs these may be produced from annealed steel and hardened after fabrication.
Stainless steels are distinguished from carbon steel by their chromium (ferritic steel) content and, in certain cases, nickel (austenitic steel). Adding chromium to carbon steel makes it more rust and stain-resistant, and when nickel is added to chromium stainless steel it enhances its mechanical properties, for example its density, heat capacity and strength.
Used for low-pressure conveyance of air, steam, gas, water, oil or other fluids and for mechanical applications. Used primarily in machinery, buildings, sprinkler systems, irrigation systems, and water wells rather than in pipelines or distribution systems.
Flat steel coil products, with widths of less than 600mm for hot rolled products and less than 500mm for cold rolled products. The wider flat products are called wide strips.
STRUCTURAL PIPE AND TUBING
Welded or seamless pipe and tubing generally used for structural or load-bearing purposes above-ground by the construction industry, as well as for structural members in ships, trucks, and farm equipment.
Rolled flange sections, sections welded from plates, and special sections with at least one dimension of their cross-section three inches or greater. Included are angles, beams, channels, tees and zeds.
Opening the outlet of a melting furnace to move metal.
Pouring a molten metal from a ladle into ingot molds, particularly iron or steel.
Reheating a quench-hardened or normalized ferrous alloy to a temperature below the transformation range and then cooling at any desired rate.
The maximum load per unit of original cross-sectional area obtained before rupture.
Vacuum degassing (VD) is used following steel making to reduce the carbon, nitrogen, hydrogen and sulphur content of molten steel. Phosphorus can also be reduced. The process takes place under vacuum in a ladle furnace, and is frequently employed by both volume and special steels producers.
When dealing with high-chromium steels, VD allows very low carbon content to be achieved without heavy chromium losses from the melt.
Vacuum degassing has become widespread as demand for higher quality steels has grown in sectors like automotive, construction, offshore, pipe making and rails. In alloy steel products like bearings VD steels improve fatigue life, while in flat products, very low carbon VD steels are well suited to demanding processing and fabrication.
About 80% of world vanadium production goes into steelmaking, but it is also an important constituent of certain high performance non-ferrous aerospace alloys. It is usually added to steel as a ferro-alloy (FeVa).
In steel, vanadium increases tensile strength, toughness and fatigue resistance, as well as improving the hardenability of some grades and conferring rust resistance. An early application was armour plate.
Today, vanadium’s main applications are in high-strength low-alloy sheet for the automotive sector, in engineering steels – such as for axles, crankshafts and gears – and in spring and high-speed tool steels. In stainless steels it is typically used for producing grades needed for applications like surgical instruments.
These are used in conjunction with roughing mills to ensure correct slab width prior to further rolling. The edger’s rolls keep the sides of the steel slab square as well as controlling width.
Vacuum oxygen decarburisation is a method for reducing the carbon content of molten steel. Oxygen is blown on to the surface of the metal, which is held in sealed vessel at reduced pressure. Very low carbon levels are possible. This method is often used in stainless steel production.
In coking coal this term refers to any constituents of the coal, apart from moisture, which are released (vaporised) at higher temperatures. These are usually mostly hydrocarbons, but also sulphur.
Along with other properties such as ash and moisture content, volatile matter content is one of the key parameters used in defining the quality of a coal.
Hardness resulting from mechanical working.
This is made from hot rolled or cold reduced strip, sheet or plate. Small and medium diameters are produced in continuous, multiple-roll mills that progressively bend incoming, unheated strip into a circular cross-section prior to welding along the longitudinal seam. Tube may subsequently be cold-drawn through dies to achieve precise dimensions and finish.
This is cheaper than the seamless process but welded tube generally has a lower mechanical and pressure performance.
Large diameters are made from discrete plate. First this is bent into a “U” shape, then an “O” shape, which is welded prior to mechanical or hydraulic expansion – the “E” of the UOE process – to achieve final dimensions. This pipe can be 400-1,600mm diameter.
Spiral welded tube/pipe uses HR strip that is twisted as it goes through a mill to form a hollow spiral which is then welded. It is cheap to make but has traditionally had a lower integrity than conventional welded pipe – though it is improving. Diameters of up to 2,500mm are possible.
This method of joining metals is essential for certain types of pipemaking and is widely used in structural steel fabrication, shipbuilding etc.
The workpieces are melted at the point where they are to be joined using a very localised, high temperature energy source, and a filler material is added to create a small additional amount of molten metal. When this cools the workpieces fuse together to form a strong joint. Pressure is sometimes applied to the workpieces during welding.
The commonly used energy sources are an electric arc and a gas flame.
Submerged arc welding (SAW) is widely used in the large scale production of steel tube and pipe from strip, sheet or plate. In this electric arc process, the molten weld area is protected from the atmosphere by a layer of conductive flux in order to prevent any contamination.
WIDE FLANGE BEAMS
These heavy duty structural sections are often referred to as H-beams and I-beams (because of their cross-sectional appearance). They are mainly used in the frames of industrial and hi-rise structures, are internationally traded and are a stockholder item in standard lengths. Dimensions are in metric, except in the USA where they are sold as “W” shapes in inches.
H-beams are mainly hot rolled from blooms. They are classified by depth (web plus end-flange thickness – hence the “W” notation in the US) and weight per unit length. These parameters are typically up to 1,000mm-plus and 600 kg/metre respectively.
They are sometimes confused with I-beams, which have similar uses but narrower flanges and smaller web depths and steelthicknesses.
This is the process by which steel wire is produced from a larger diameter feedstock, usually wire rod.
Wire is the smallest diameter steel product, and to achieve the gauges needed for manufacturing items like fencing, nails, tyrecord and ultra-fine filtration gauzes, the cold rod is pulled through a series of drawing dies, each of successively smaller bore diameter.
A continuous multi-die wire-drawing machine can have up to 15 blocks, each containing a die. These have a metal casing but the forming hole is made in a ‘nib’ of tungsten carbide, or natural or synthetic diamond. Though mostly round, wire can be flat or have other profiles.
A wide range of steels may be drawn, from the mild steel used for paper clips and champagne cork wire, to spring grades and the high strength steels needed for suspension bridge cables and piano wire.
Hot rolled from low, medium and high carbon or alloy steel billet, wire rod is delivered as coil, most commonly at 5.5mm dia, but in sizes up to 60mm dia. Close control of final cooling is a critical part of production.
Low carbon rod is used for undemanding applications like fencing wire and concrete reinforcing mesh, while medium and high carbon rod goes into higher performance uses like steelcord for car tyre reinforcement.
Some rod (cold heading carbon and alloy grades) is used to make fasteners (bolts, screws, nails, rivets), and alloy rod is commonly machined into products like engineering bearings. Some rod provides filler metal in welding operations.
This is a type of iron, which unlike hard, brittle pig iron – such as is tapped from a blast furnace – is tough and malleable, allowing it to be forged and welded. It has a high tensile strength and is more corrosion resistant than steel.
Wrought iron has a very low carbon content – lower than many steels – but importantly it has traces of manganese/sulphur/phosphorus/silicon-containing slag which give it a fibrous structure and which contributes to its desirable properties.
Production is by melting and then stirring new pig iron or scrap cast iron to lower the carbon content, a process known as “puddling”. This is followed by forging to optimise slag content.
Wrought iron was widely used for structural, engineering and decorative applications, and consumption declined after the mid-nineteenth century once steel became more widely available. Small amounts are produced today for artistic applications and restoration work.
Arguably the most famous example of wrought iron in action is the Eiffel Tower, Paris.
Metals which after melting, casting and solidifying have been further worked in a hot or cold condition to alter their shape and/or dimensions by rolling, forging, extruding and drawing.
The load per unit of original cross-section area at which a marked increase in the deformation of the specimen occurs without increase of load. It is usually calculated from the load determined by the drop of the beam of the testing machine or by use of dividers.
The Sendzimir mill is specifically designed for processing stainless steel and other metals which rapidly work harden during cold rolling, making gauge reduction difficult.
A typical Sendzimir rolling stand is immediately recognisable by its large number of small diameter back-up rolls (typically about 20) clustered around two small-diameter work rolls. This is in contrast to the large diameter work rolls and two or four large back-up rolls on most rolling mills.
The large number of back-up rolls on the Sendzimir allows very high reduction forces to be exerted on the passing sheet, and gauges down to 0.025mm are not unusual for stainless steel – although several passes through the mill may be required to achieve this. After each cold reduction, stainless coil must be annealed before it can be further processed.
The original design was developed the Polish engineer Tadeusz Sendzimir, but this type of mill is also referred to as a Z-mill or cluster mill, and apart from rolling stainless, is used for silicon and certain carbon steels, as well as some non-ferrousmetals.
This is the practice when making steel dumping calculations of counting negative anti-dumping margins as zero, and not allowing them to fully offset positive margins in order to keep any margins that are imposed artificially high.
In steel it is a practice which in recent years is particularly associated with the USA, and the continued use of zeroing is routinely challenged by the European Commission, most recently at WTO hearings.
The key argument against zeroing is that without it the dumping margin could be “de minimis” (too small to be worth enforcing), or even negative.
Trade policy observers have long considered this to be a fundamentally distortive practice, as it almost always ensures the finding of dumping margins.