Combined Metals of Chicago (CMC) offers a quick and easy to use glossary containing many of the terms we may use throughout the website.
A roughening or scratching of a surface due to abrasive wear.
The removal of material from a surface when hard particles slide or roll across the surface under pressure. The particles may be loose or may be part of another surface in contact with the surface being worn.
Accelerated Corrosion Test:
A test conducted under controlled conditions that are considerably more severe than those natural conditions whose effects are presumably being investigated. The advantages of such a test is the relatively short time required. Results are useful for qualitative comparisons, but are not reliable for predicting anticipated life in actual service. Usually performed according to ASTM B117.
Brittleness resulting from pickling steel in acid; hydrogen, formed by the interaction between iron and acid, is partially absorbed by the metal, causing acid brittleness.
A process of aging that increases hardness and strength and usually decreases ductility. (see Precipitation Heat Treatment)
Denotes material for important or highly stressed parts of aircraft for other similar purposes; such materials are extremely high quality requiring closely controlled, restrictive and special practices in their manufacture.
A process generally accelerated by temperature, wherein changes in mechanical properties occur in certain metals. These changes generally raise room temperature hardness, tensile and yield strength, while lowering ductility.
American Iron and Steel Institute. Published Steel Products Manual to Stainless and Heat Resisting Steels which provides information concerning tolerances, chemical analysis, definitions of technical terms and other related subjects which have been developed in the manufacture and use of stainless steels.
Composite sheet produced by bonding either corrosion-resistant aluminum alloy or aluminum of high purity to base metal of structurally stronger aluminum alloy. The coatings are anodic to the core so they protect exposed areas of the core electrolytically during exposure to corrosive environment.
A material that has metallic properties and is composed of two or more chemical elements of which at least one is a metal (i.e. steel is an alloy of carbon in iron; stainless steel is an alloy of carbon, chromium and sometimes nickel in iron.)
Those elements in alloys which are deliberately added during melting and refining to enhance the properties of that alloy.
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.
Forming an aluminum or aluminum alloy coating on a metal by hot dipping, hot spraying, or diffusion.
A process involving heating to a temperature at or above critical and cooling at a controlled rate, usually applied to induce softening. The process could alter mechanical properties, physical properties or micro structure.
AOD (Argon Oxygen Decarburization):
This term refers to both the process and the vessel that is used for the process in which hot metal from an electric furnace is refined to a chemical specification by blowing a mixture of gases (a combination of inert gas and oxygen) under the hot metal surface. The result removes carbon from ferroalloys to achieve a certain chemical specification. The economics of this process have indicated that this method is ideally suited for producing stainless, plus high and low-alloy steels.
An arc furnace is a melting device that gets its heat-generating capacity from the introduction of an electric arc to a charge of scrap materials and ferroalloys. This caused the melt-down to a liquid state known as “hot metal”.
A group of welding processes wherein the metal or metals being joined are coalesced by heating with an arc, with or without the application of pressure and with or without the use of filler metal.
American Society for Testing Materials is a voluntary standards development system. It is a non-profit organization which provides a forum for producers, users, consumers, and those having a general interest to meet on common ground and write standards for materials, products, systems and services.
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.
Any cold-finished round, square, octagon, hexagon or shape over 1/2″ in diameter or size. Any cold-finished flat 3/8″ and over width and 1/8″ and over in thickness. Any hot-rolled (not in coil form) or forged round, square, octagon, hexagon or shape 1/4″ and over in diameter or size. Any hot-rolled flat 1/4″ to 10″ inclusive in width and 1/4″ and over in thickness.
Basic Oxygen Process:
A steel-making process wherein oxygen of the highest purity is blown onto the surface of a bath of molten iron contained in a basic lined and ladle shaped vessel. The melting cycle duration is extremely short with quality comparable to Open Hearth Steel.
A test for determining relative soundness, toughness and ductility of a metal to be formed. Usually done in accordance with ASTM E290.
A process for making steel by blowing air through molten pig iron contained in a refractory-lined vessel so that the impurities are thus removed by oxidation.
A solid semi-finished round or square product that has been hot-worked by forging, rolling, or extrusion. An iron or steel billet has a minimum width or thickness of 1-1/2 inch and the cross-sectional area varies from 2-1/4 to 36 square inches. For nonferrous metals, it may also be a casting suitable for finished or semi-finished rolling or for extrusion.
An alloy containing two elements, apart from minor impurities, as brass containing the two elements copper and zinc.
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 vertical shaft type smelting furnace in which an air blast is used, usually hot, for producing pig iron. The furnace is continuous in operation, using iron ore, coke, and limestone as raw materials that are charged at the top while the molten iron and slag are collected at the bottom and tapped out at intervals.
A semi-finished steel form whose rectangular cross-section is more than eight inches. 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.
BOF (Basic Oxygen Furnace):
This term describes the process and the vessel that is used in the process by which hot metal, received from the induction or blast furnace, is refined to meet chemical specifications by blowing oxygen from a top lance against the “hot metal” bath surface. This reduces the carbon level to an acceptable level and raw materials are added to achieve a desired chemical specification.
Annealing steel in a sealed container under conditions that minimize oxidation (scale).
A family of welding procedures where metals are joined by filler metal that has a melting temperature below the solidus of the parent metal, but above 840°F (450 C).
See Coil Breaks.
Break Test (for tempered steel):
A method of testing hardened and tempered high-carbon spring steel strip wherein the specimen is held and bent across the grain in a vice-like calibrated testing machine. Pressure is applied until the metal fractures, at which point a reading is taken and compared with a standard chart of break limitations for various thickness ranges.
Bright Annealed Finish:
Bright cold-rolled, highly reflective finish retained by final annealing in a controlled-atmosphere furnace.
Process of annealing usually carried out in a controlled furnace atmosphere so that surface oxidation is reduced to a minimum and the surface remains relatively bright.
Brinell Hardness Test:
A test for determining the hardness of a material by forcing a hard steel or carbide ball with a specified load into a surface. The result is expressed as the Brinell hardness number, which is the value obtained by dividing the applied load in kilograms by the surface area of the resulting impression in square millimeters.
Finish generally produced by polishing; most common are no. 3 finish (approx. 100 grit) and a finer no. 4 finish (approx. 120 to 150 grit). Brushed finish appearance can also be simulated by final gauge rolling with ground rolls; reproducibility from lot to lot and even from beginning of rolling to end of rolling.
An out-of-flat condition on cold-rolled coils often called oil-canning; the cause can be varied. Buckles can cause more severe shape problems during slitting not to mention excessive camber.
Producing a bulge, bend, bow, kink, or other wavy condition by compressively stressing a beam, column, plate, bar or sheet.
Stainless is brightened by rubbing the surface with fabric buffs and compound.
A rough or sharp edge left on the material after cutting or slitting.
Joining two edges or ends by placing one against the other and welding them
When sheet or strip is rolled, it is not exactly straight from end to end. If a coil was unrolled along an absolutely straight stretch of highway, it would be found to wander from side to side or in some cases, run off the road completely. This deflection to the left and right is called camber. It is measured as the amount of left or right deflection in 8-feet. As it relates to plates is the horizontal edge curvature in the length, measured over the entire length of the plate in the flat position.
A compound of carbon with one or more metallic elements.
In 300 series stainless steel, Chromium reacts with Carbon in the temperature range of 800° to 1500°F causing “sensitization”. This reaction is generally considered to be detrimental to corrosion resistance because of the Chromium content decrease in the grain area adjacent to the grain boundaries.
Steel which owes its properties chiefly to carbon without substantial amounts of other alloying elements. Also known as straight carbon steel or plain carbon steel. It is classified as carbon steel when the maximum content does not exceed the following percentages: Manganese: 1.65; Silicon: 0.60; Copper: 0.60 (when specified).
A process in which an austenitized ferrous material is brought into contact with a carbonaceous atmosphere having sufficient carbon potential to cause absorption of carbon at the surface and, by diffusion, create a concentration gradient.
Iron containing more carbon than the solubility limit in austenite (about 2%).
(1) An object at or near finished shape obtained by solidification of a substance in a mold. (2) Pouring molten metal into a mold to produce an object of desired shape.
A casting made by pouring metal into a mold that is rotated or revolved.
A pendulum-type single-blow impact test in which the specimen usually notched, is supported at both ends as a simple beam and broken by a falling pendulum. The energy absorbed, as determined by the subsequent rise of the pendulum, is a measure of impact strength or notch toughness.
Surface condition characterized by a series of close spaced lines across the strip width; generally caused by vibration in the mill rolls.
Chemical Content or Analysis:
A breakdown of elements present by percent of weight in metals or alloys. Although the ladle analysis is certified at the time of melting, additional analyses may be performed throughout the steel producing process.
Chemical symbol Cr. Element No. 24 of the periodic system; atomic weight 52.01. It is of bright silvery color, relatively hard. It is strongly resistant to atmospheric and other oxidation. It is of great value in the manufacture of Stainless Steel as an iron-base alloy. Chromium plating has also become a large outlet for the metal. Its principal functions as an alloy in steel making; (1) increases resistance to corrosion and oxidation (2) increases harden-ability (3) adds some strength at high temperatures (4) resists abrasion and wear (with high carbon).
One of a number of compounds of chromium and carbon, with or without limited amounts of other metallic elements when occurring in steel, appearing as separated phase in chromium steels and stainless steels.
A surface treatment at elevated temperature, generally carried out in pack, vapor, or salt bath, in which an alloy is formed by the inward diffusion of chromium into the base metal.
Classification of Stainless Steels:
Stainless steels are classified into five distinct groups, namely: austenitic, ferritic, martensitic, precipitation hardenable and duplex.
A rolling mill where each of the two working rolls of small diameter is supported by two or more back-up rolls.
Chemical symbol Co. Element No. 27 of the periodic system; atomic weight 58.94. A gray magnetic metal, of medium hardness; it resists corrosion like nickel, which it resembles closely; melting point 2696°F.; specific gravity 8.9. It is used as the matrix metal in most cemented carbides and is occasionally electroplated instead of nickel, the sulfate being used as electrolyte. Its principal function as an alloy in tool steel; it contributes to red hardness by hardening ferrite.
Surface condition characterized by a series of wide spaced lines generally caused by reels used in uncoiling.
Almost all coils will display coil set when un-banded except for very thin or very soft material. Because most coils are delivered with inside diameters of less than two feet, coil set resulting from bending to these diameters will be introduced even if the coil was “dead-flat” before recoiling at the mill or slitter. Mill capability is 6″ maximum in a 3-foot length.
A process of impressing images or characters of the die and punch onto a plain metal surface.
Cold Reduced Strip:
Metal strip, produced from hot-rolled strip, by rolling on a cold reduction mill.
Plastic deformation, such as rolling, hammering, drawing, etc., at a temperature sufficiently low to create strain-hardening (work-hardening). Commonly, the term refers to such deformation at normal temperatures.
Concast/Continuous Casting Method:
Concast is an abbreviation for continuous cast, a molding process developed as an alternative to the ingot casting method. In continuous casting, the mold is made of copper and is water-cooled to remove heat from the molten steel. As the metal passes through the water-cooled mold, it forms a solid shell on the outside while the inside is still full of liquid steel. This shell passes out the bottom of the copper mold and into a spray chamber where water is directed against it, removing more and more of the heat from the steel and causing it to solidify from the edge toward the center until it is completely solidified. This solidified slab passes out upon a roller conveyor where it is cut to the lengths desired for hot rolling.
The removal of surface defects (seams, laps, pits, etc.).
The process where coils are unwound and run continuously through an annealing furnace at prescribed speeds and softening temperatures.
Passing sheet or strip metal continuously through a series of pickling and washing tanks.
Continuous Strip Mill:
A series of synchronized rolling mill stands in which coiled flat-rolled metal entering the first pass (or stand) moves in a straight line and is continuously reduced in thickness (not width) at each subsequent pass. The finished strip is recoiled upon leaving the final or finishing pass.
Controlled Atmosphere Furnaces:
A furnace used for bright annealing into which specially prepared gases are introduced for the purpose of maintaining a neutral atmosphere so that no oxidizing reaction between metal and atmosphere takes place.
Cores are thick cardboard sleeves that hold light-gauge coils in the same way that thin cardboard sleeves hold Aluminum wrap in your home. The cardboard used with steels is about 3/4 inch thick and is extremely strong. Light-gauge material is frequently wrapped onto cores to prevent the coils from collapsing in transit. The use of cores also prevents damage to the wraps on the inside diameter by crane hooks or fork truck forks.
Destruction of metal by chemical or electrochemical reaction with its environment; simply said, “eating away of metals”.
The embrittlement caused in certain alloys by exposure to a corrosive environment. Such material is usually susceptible to the intergranular type of corrosion attack.
Cracking produced by the combined action of repeated or fluctuating stress and a corrosive environment.
The ability of a metal to withstand attack in an environment that is conductive to chemical or electrochemical reaction.
Corrosion Resistance Alloys:
These are materials which provide a higher degree of stress corrosion and/or chloride pitting resistance than that of common types 2XX, 3XX, or 4XX stainless steels. Corrosion resistant alloys are generally characterized by chrome content of at least 20% and/or moly content greater than 2%.
A piece of metal from which a test specimen is to be prepared – often an extra piece (as on a casting or forging) or a separate piece made for test purposes (such as a test weldment).
(1) The temperature or pressure at which a change in crystal structure, phase, or physical properties occurs. Same as transformation temperature. (2) In an equilibrium diagram, that specific value of composition, temperature and pressure, or combinations thereof, at which the phases of a heterogeneous systems are in equilibrium.
Cutting off ends of billets, ingots or slabs containing pipe or other defects.
The rolling of sheet, plate or slabs so that the direction of rolling is changed 90 degrees from the direction of the previous rolling.
Deviation from flat across the strip width.
Edge to edge thickness variation in flat rolled products. Crown is generally a smooth curve from the center of mill coil to within a few inches of the edge where thickness starts to drop or “feather” more rapidly. In narrow slit coils, crown will appear as a variation in thickness from coil to coil. On a half width slit coil or “split”, wedged shaped cross sections occur, thicker on one side than on the other.
Sub-zero temperature applications.
(1) A physically homogeneous solid in which the atoms, ions or molecules are arranged in a three-dimensional repetitive pattern. (2) A coherent piece of matter, all parts of which have the same anisotropic arrangement of atom; in metals, usually synonymous with grain and crystallite.
A method whereby the raw slit edge of metal is removed by rolling or filing.
Removal of carbon from the outer surface of iron or steel, usually by heating in an oxidizing or reducing atmosphere. Water vapor, oxygen and carbon dioxide are strong decarburizers. Reheating with adhering scale is also strongly decarburizing in action.
A departure of any quality characteristic from its intended (usually specified) level that is severe enough to cause the product or service to not fulfill its anticipated function. According to ANSI standard, defects are classified according to severity:
- Very serious defects lead directly to severe injury or significant economic loss.
- Serious defects lead directly to significant injury or significant economic loss.
- Major defects are related to major problems with respect to anticipated use.
- Minor defects are related to minor problems with respect to anticipated use.
A quality control term describing a unit of product or service containing at least one defect, or having several lesser imperfections that, in combination, cause the unit not to fulfill its anticipated function. NOTE: The term defective is not synonymous with non-conforming (or rejectable) and should be applied only to those units incapable of performing their anticipated functions.
Removal of grease, oil or other lubricant-type materials by immersion in an effective solvent.
Degassing Process (in steel making):
Removing gases from the molten metal by means of a vacuum process in combination with mechanical action.
(1) Removal of oxygen from molten metals by use of suitable chemical agents. (2) Sometimes refers to removal of undesirable elements other than oxygen by the introduction of elements or compounds that readily react with them.
(1) Spreading of a constituent in a gas, liquid or solid, tending to make the composition of all parts uniform. (2) The spontaneous movement of atoms or molecules to new sites within a material.
A change in the visual appearance of the material caused by formation of oxides when exposed to contaminating atmosphere, always at elevated temperatures.
Steels exhibiting both austenitic and ferritic structures and characteristics.
The ability to accept permanent deformation.
Finish obtained by cold-rolling on polished rolls without the use of any coolant or metal lubricant, of material previously plain pickled, giving a burnished appearance.
Dumping occurs when imported merchandise is sold in or for export to the domestic market at less than the normal value of the merchandise – that is, at a price that is less than the price at which identical or similar merchandise is sold in the comparison market, the home market (the market of the exporting country), or third-country market (in this case, “market” is used as proxy to “home market” in cases where home market cannot be used). The normal value of the merchandise cannot be below the cost of production.
Wavy projections (i.e. ears) formed during deep drawing as a result of directional properties or anisotropy of the strip.
The outer boundaries of a sheet product. If untrimmed, they are termed Mill Edge. The rolling process squeezes the area and causes the edges to form a semi-cylindrical, slightly ragged profile. As it runs parallel with the rolling direction, it deviates from a true straight line causing some slight variations in strip width. The appearance of a mill-edge product varies from a fine, finishing file rasp appearance, to a very “sawtooth” condition. Micrometer readings along a narrow band along the edge of the strip may indicate slightly less gauge thickness than that of the rest of the strip. This condition is termed “feathering”. When blanking or shearing parts from mill-edge material, sufficient width allowance should be made to insure obtaining the shape and size of the pattern sheet. If trimmed, they are termed Cut Edge. There, the edge will resemble the result of shearing, slitting, or trimming the mill edge. The overall width from one end of the coil to other will be uniform. If the product has been slit in a pickle line, the edge may exhibit some slight jaggedness, but no sawtooth condition appears. Edge also refers to type of finish on the side of the material.
- #1 edge – Round or square edge, rolled.
- #2 edge – Square, produced by slitting, not filed.
- #3 edge – Square, produced by rolling, filing after slitting.
An electromagnetic nondestructive testing method in which eddy current flow is induced in the object. Changes in the flow caused by variations in the object are reflected into a nearby coil or coils where they are detected and measured by suitable instrumentation.
Electric Arc Furnace (EAF):
Steelmaking furnace where scrap is generally 100% of the charge. Heat is supplied from electricity that arcs from the graphite electrodes to the metal bath. Furnaces may be either an alternating current (AC) or direct current (DC). DC units consume less energy and fewer electrodes, but they are more expensive.
Electric Furnace Steel:
Steel made in any furnace where heat is generated electrically, almost always by arc. Because of relatively high cost, only tool steels and other high-value steels are made by the electric furnace process.
Galvanizing by Electro deposition of zinc on steel.
Electrolytic Tin Plate:
Black plate that has been electroplated with commercially pure tin on both sides.
Electron Beam Microprobe Analyzer:
An instrument for selective chemical analysis of a small volume of material. An electron beam bombards the area of interest and x-radiation thereby emitted is analyzed in a spectrometer.
Method for imparting brilliance to stainless steel by removing a thin layer of the surface akin to a reverse electroplating process without any working of the underlying metal. Also known as bright finishing. The process highlights surface irregularities (i.e. roll grit pattern, pickle matte, scratches, pits and digs). Very special processing is required to enhance surface to be electropolished.
The amount of permanent extension or stretching a material will undergo before fracture. The value is expressed as a percentage and is obtained by tensile testing. Elongation is an indication of the materials ductility. In testing, a two-inch length is normally scribed on the tensile specimen in the area that is expected to fail. After the test is conducted, the tensile specimen pieces are measured to determine the full extension of the scribe marks. Percent elongation is calculated by multiplying by 100. For example, if the increase is 1″, then the percent elongation would be 50. The higher the number the better the ductility.
Maximum alternating stress which a given material will withstand for an infinite number of times without causing fatigue failure.
Shaping metal into a chosen continuous form by forcing it through a die of appropriate shape.
The phenomenon leading to fracture under repeated or fluctuating stresses having a maximum value less than the yield strength of the material. Fatigue fractures are progressive, beginning as minute cracks that propagate under the action of the fluctuating stress.
Highest value of stress that a material can withstand for a given number of cycles.
A metallurgical phase of iron in which metallic alloying elements are in solid solution, but carbon is essentially insoluble. Ferrite is virtually absent in quenched martensitic and austenitic stainless steels, but its presence characterizes ferritic stainless steels. Annealed martensitic steels contain ferrite and carbide.
Grade of steel containing in excess of about 12% chromium and used in a condition in which their micro-structure consists of ferrite plus carbides.
Ferritic Stainless Steel:
Straight Chromium non-hardenable class of stainless steel alloys with Chromium ranging from 10.5 to 30% and Carbon under .20%. A term used to identify certain high-chromium content, stainless steels, such as Types 409, 430, 434, 430, 439, 442, and 446. These steels are essentially non-hardenable by heat treatment and only slightly hardenable by cold work.
An iron-bearing product, not within the range of those called steels, which contains a considerable amount of one or more alloying elements, such as manganese, silicon, phosphorus, vanadium, chromium, ferromanganese, ferrophosphorus, ferrosilicon, and ferrovanadium. The chief use of these alloys is for making additions of their respective alloying elements to molten steel.
A finishing material which contains about 70% chromium. It is used when it is desired to add chromium to steel.
A product of the blast furnace, containing, besides iron, 78 to 82% of manganese and some silicon, phosphorus, sulphur and carbon. It is used as a deoxidizer and for the introduction of manganese into steel.
- HRAP No. 1. Hot-rolled, annealed, and descaled.
- Bright-annealed.Is a bright cold-rolled highly reflective finish abstained by final annealing in a controlled atmosphere furnace.
- Temper-rolled.The finish of products resulting from cold-working the annealed and descaled or bright-annealed product sufficiently to obtain mechanical properties higher than those normally obtained. Appearance will vary depending upon the amount of cold work required and the alloy.
A resistance butt-welding process in which the weld is produced over the entire abutting surface by pressure and heat, the heat being produced by electric arcs between the members being welded.
Measure of variance from a flat surface. On cold-rolled strip flatness variance is measured: 1) across the width (i.e. crossbow) and 2) along the length (i.e. edge wave). Crossbow allowable variance is expressed in thousandths of an inch maximum per inch of width (i.e. commercial flatness is .020″ P.I.W.). Edge wave is calculated knowing the length of a typical wave and the height of that wave; the wave-controlling condition is then stated by the formula of wave height divided by twice the wave length times 100 being less than a stated percentage (i.e. w/21 x 100 < 6%).
(1) Texture showing the direction of metal flow during hot or cold working. Flow lines often can be revealed by etching the surface or a section of a metal part. (2) In mechanical metallurgy, paths followed by volume elements of metal during deformation.
The shear stress required to cause plastic deformation of solid metals.
A shear which severs steel as the piece continues to move. In continuous mills, the piece being rolled cannot be stopped for the shearing operation, so the shear knives must move with it until it is severed.
(1) In refining, a material used to remove undesirable substances as a molten mixture. It may also be used as a protective covering for molten metal. (2) In welding, a material used to prevent the formation of, or to dissolve and facilitate the removal of, oxides and other undesirable substances.
(1) As a noun; a metal product which has been formed by hammering or pressing. (2) As a verb; forming hot metal into the desired shape by means of hammering or pressing.
Metal in any form less than 0.006 in. in thickness.
See Reversing Mill.
Descriptive treatment of fracture, especially in metal, with specific reference to photography of the fracture surface.
Breaking a specimen and examining the fractured surface with the unaided eye or with a low-power microscope to determine such things as composition, grain size, case depth, soundness, and presence of defects.
Pertains to the machining characteristics of an alloy to which one or more ingredients have been introduced to produce small broken chips, low power consumption, better surface finish or longer tool life.
Deep pits in steel coils caused by laps sliding past each other or strip dragging across a roll that is not turning.
Coating steel with zinc and tin (principally zinc) for rust-proofing purposes. Formerly for the purpose of galvanizing, cut-length steel sheets were passed singly through a bath of the molten metal. Today’s galvanizing processing method consists of uncoiling and passing the continuous length of successive coils either through a molten bath of the metal termed “Hot Dipped Galvanizing” or by continuously zinc-coating the uncoiled sheet electrolytically-termed “Electro-Galvanizing”.
Bounding surface between crystals. When alloys yield new phases (as in cooling), grain boundaries are the preferred location for the appearance of the new phase. Certain deterioration, such as season cracking and caustic embrittlement, occur almost exclusively at grain boundaries.
Fiber-like lines appearing on polished and etched sections of forgings, caused by orientation of the constituents of the metal in the direction of working during forging.
Gauges & Width Tolerance:
Customers always order a specific gauge and width (and in some cases length). Since it is impossible to produce material to that exact gauge or width, the actual gauge or width will vary to be slightly above, slightly below, and sometimes exactly on the ordered gauge and width. Tables have been published by various organizations which spell out how much above and below the ordered width, gauge, and length you are permitted to be and still have an acceptable product. Probably the most common of these tables are those in the ASTM Specification A480. Mill price books usually contain tolerance data.
Grit refers to small particles of something that tend to be abrasive. The coarseness or fineness of grit is defined by a numbering system, with coarse grit having low numbers such as 12 and fine grit having high numbers such as 1000. This numbering system is used to define the fineness or coarseness of the abrasive belts that we use to grind or polish steel coils.
For metals, a measure of the areas or volumes of grains in a polycrystalline material, usually expressed as an average when the individual sizes are fairly uniform. In metals containing two or more phases, the grain size refers to that of the matrix unless otherwise specified. Grain sizes are reported in terms of number of grains per unit area or volume, average diameter, or as a grain-size number derived from area measurements. Usually tested according to ASTM E112.
The enlarging or coarsening of the individual grains within the metal or alloy during heating at a temperature above the re-crystallization temperature. Excessive grain growth can cause Orange Peel during drawing.
The response of an alloy to a specified heating and quenching cycle – usually understood to be the maximum hardness that can be attained with the individual heat using the specified heat treatment, as used in connection with the martensitic (hardenable) stainless steels.
Any process for increasing the hardness of a metal or alloy.
Measurement of a material’s resistance to deformation. The types of hardness tests measure the material’s resistance to penetration. The hardness tests conducted include: 1) Rockwell, 2) Superficial and 3) Micro-hardness 4) Brinell tests. The Rockwell test is employed for heavy gauge (>=.040) strip; B scale is used for annealed stainless steels or some softer nonferrous alloys and metals. C scale is used for tempered stainless steels and high-strength nonferrous metals and alloys. The superficial hardness test is for intermediate gauges with 15-, 30- and 45-kilogram loads; T scale is for annealed stainless, etc.; N scale is for tempered stainless, etc. Micro hardness tests are performed on light foil gauges (.010″ or less) and is expressed as DPH or VHN with the testing load employed. Regardless of test method employed, higher numbers indicate harder material.
The quantity of steel produced by a furnace with one melting. Steel melting is a batch process and each batch is a heat.
An identifying number assigned to the product of one melting in an electric arc furnace: e.g. 19345. Sometimes, but not universally, the first digit indicates the furnace number; the second digit indicates the year in which the heat was melted. The last three (and sometimes four) digits show that this was the 345th heat melted in No. 1 furnace during 1989.
Controlling the constitution and properties of metals and alloys by heating and cooling.
A defective surface condition characterized by chevrons at roughly 45° angles to the rolling direction. Condition can be induced during cold-rolling.
High Strength Steel:
Commonly known as High Strength Alloy(HSLA)-A specific class of low-alloy steels in which increased mechanical properties and, usually, good resistance to atmospheric corrosion are obtained with moderate amounts of one or more alloying elements other than carbon.
In steel mill practice, a process whereby ferrous alloy base metals are dipped into molten metal, usually zinc, tin, or terne, for the purpose of fixing a rust-resistant coating.
Hot Roll Band:
This is what a coil is called as it is removed from the hot mill downcoiler until it has received its first cold-rolling operation.
A test to determine the behavior of materials when subjected to high rates of loading usually in bending, tension, or torsion. The quantity measured is the energy absorbed in breaking the specimen by a single blow, as in the Charpy or Izod.
Particles of impurities (usually oxides, sulfides, silicates, aluminates) that are formed during solidification. Inclusions are generally described as nonmetallic. The test procedure for measuring the micro cleanliness or severity of inclusion content is ASTME-45.
Quench hardening in which the heat is generated by electrical induction.
Historically, after steel had been melted and refined, it was cast into ingot molds. These are vertical, very thick walled boxes of gray iron with a cavity in the middle the size of the desired ingot. Steel is poured into this cavity and allowed to solidify. The steel contracts in volume as it solidifies and pulls away from the mold to form the ingot. Once the ingot is removed from the mold, it is to be hot-rolled into a slab for further processing.
Localized attack at grain boundaries, with relatively little corrosion of the grains. As corrosion proceeds, the grains fall out and the metal or alloy disintegrates. Austenitic stainless steels are susceptible to inter-granular corrosion if heated in the 800°F to 1500°F range which causes “sensitization” or Chromium depletion adjacent to the grain boundaries. Usually tested according to ASTM A262.
The placing of a sheet of paper between two adjacent layers of metal to facilitate handling and shearing of rectangular sheets, or to prevent sticking or scratching.
An annealing treatment given to wrought metals following cold work hardening for the purpose of softening prior to further cold-working.
Formation of oxides beneath the surface of a metal.
The aging of an alloy at two or more temperatures by steps, and cooling to room temperature after each step. Compare with progressive aging.
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.
Isothermal Transformation (IT) Diagram:
A diagram that shows the isothermal time required for transformation of austenite to commence and to finish as a function of temperature. Same as time-temperature-transformation (TTT) diagram or S-curve.
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Steel deoxidized by silicon or aluminum to reduce the oxygen content to a minimum so that no reaction occurs during solidification of the metal. Killed steels have more uniform properties and chemical composition than other types. Stainless steels are not “killed”.
A large vessel into which molten metal or molten slag is received and handled. Molten metal may be transported short distances by carrying it in a ladle.
Defects resulting from the presence of blisters, seams or foreign inclusions aligned parallel to the work surface of the strip. Unfortunately “lamination” is used as a catchall term for any and all surface defects.
A discontinuity appearing as a seam caused from folding over during hot-rolling.
Elongated surface markings or depressions caused by localized plastic deformation that results from discontinuous (in homogeneous) yielding. Also known as Lauders bands, Hartmann lines, Piobert lines, or stretcher strains.
A process to flatten any shape deficiencies (wavy edges and buckles) in the sheet, prior to final shipment. Most cold-rolled sheet initially has a crowned cross-section that, if such a shape is desirable to the customer, must be flattened in the leveling line.
Identification of material, using an inked wheel, or jet printer which prints on the strip.
Partial melting of an alloy.
The principal direction of flow in a worked metal, tensile testing can be done in this direction.
Macro Etch Test:
A test for visual evaluation of the homogeneity and soundness of an ingot, bloom, billet, or bar. It involves pickling a disc or cross section in strong acid until deep etching displays the steel’s macro structure.
A photographic reproduction of any object that has not been magnified more than ten times.
The structure of a metal as revealed by examination of the etched surface at a magnification not exceeding ten diameters.
A nondestructive method of inspection for determining the existence and extent of possible defects in ferromagnetic materials. Finely divided magnetic particles, applied to the magnetized part, are attracted to and outline the pattern of any magnetic-leakage fields created by discontinuities.
Commonly expressed as permeability which is the ratio of the magnetic induction to the magnetic intensity. The important factor to remember is that the permeability increases as the material becomes more magnetic. The 300 series stainless is non-magnetic in the annealed condition. However, as these grades become increasingly cold worked, they become more magnetic. Annealing will restore the non-magnetic condition.
A process of annealing white cast iron in such a way that the combined carbon is wholly or partly transformed to graphitic or free carbon or, in some instances, part of the carbon is removed completely.
A metal bar around which other metal may be bent.
Quenching an austenitized ferrous alloy in a medium at a temperature in the upper part of the martensite range, or slightly above that range, and holding it in the medium until the temperature throughout the alloy is substantially uniform. The alloy is then allowed to cool in air through the martensite range.
A hard constituent in all steels which is a transformation product of austenite. In stainless steels it can be formed from austenite by high-temperature heat treatment (i.e. 410, 420, 440) or by cold-working (i.e. 301, 302, 304); method depends on chemistry balance.
Martensitic Stainless Steels:
(400 SERIES WHICH HAVE HIGH CARBON). These grades of stainless have chromium in the range of 11% to 17% as the sole major alloying addition. This is the same as the ferritic grades. However, carbon is added in amounts from 0.10% to 0.65% to radically change the behavior of the martensitic alloys. The high carbon enables the material to be hardened by heat treatment.
A special test for revealing grain size when the steel is heated above the critical range. The test sample is immersed in a carbonaceous medium, heated to 1700°F for a designated period of time and then allowed to cool. The treatment causes the grains of the steel to be outlined sharply when polished, etched, and viewed under a microscope. There are eight standard McQuaid-Ehn grain sizes, ranging from No. 8, the finest, to No. 1, the coarsest.
Those properties that reveal the reaction, either elastic or plastic, of a metal to an applied stress. Tensile strength, yield strength, elongation, reduction of area, hardness, impact strength, and bendability are mechanical properties.
Plastic deformation or other physical change to which metal is subjected, by rolling, hammering, drawing., etc. to change its shape, properties or structure.
Contains from 0.30% to 0.60% carbon and less than 1.00% manganese. May be made by any of the standard processes.
The range of temperature in which an alloy melt; that is the range between solidus and liquidus temperatures.
In general these elements are distinguished by their luster, malleability, conductivity, and ability to form positive ions. Iron, Chromium, Nickel, Molybdenum, Cobalt, Titanium among others are metallic. Carbon, Sulfur, Phosphorus, Nitrogen, etc. are nonmetallic.
Science concerning the constitution of metal and alloys as revealed by the microscope.
The art and science which deals with the extraction of metals from their ores and the adaptation and application of these metals to the uses for which they are intended.
A hardness test employed to check light-gauge metals and alloys.
The internal structure of metals as viewed at high magnification (usually 100 diameters or more) under the microscope.
The normal edge of steel produced in hot rolling and does not conform to any definite contour. Mill edge products may contain some edge imperfections, the more common of which are checked edges, thin edges (feather) and damaged edges due to handling or processing.
A highly reflective finish obtained by polishing with successively finer abrasive and buffing extensively free of grit lines. Finish is used most for architectural applications.
Modulus of Elasticity (tension):
Force which would be required to stretch a substance to double its normal length, on the assumption that it would remain perfectly elastic, i.e., obey Hooke’s Law throughout the twist. The ratio of stress to strain within the perfectly elastic range.
The temperature at which a martensitic transformation starts during cooling after austenitization.
Local reduction of the cross-sectional area of metal by stretching.
A structure in which the crystals of one constituent are surrounded by envelopes of another constituent which gives a network appearance to an etched test specimen.
Metals or alloys that are free of iron or comparatively so.
A term opposed to refractory alloy. A non-refractory alloy has malleability, that is, ease of flattening when subjected to rolling or hammering.
Rolled steel too light or too heavy to meet requirements.
A process of hardening a ferrous alloy of suitable composition by heating within or above the transformation range and quenching in oil.
A method of measuring the ductility and drawing properties of strip or sheet metal which involves determination of the width and depth of impression. The test simulating a deep drawing operation is made by a standard steel ball under pressure, continuing until the cup formed from the metal sample fractures. Readings are in thousandths of an inch. This test is sometimes used to detect stretcher straining and indicates the surface finish after drawing, similar to the Erichsen ductility test.
One-Side Bright Mill Finish:
Sheet material having a moderate degree of brightness on one side. The reverse side is uncontrolled and may have a dull, non-uniform appearance.
Roughening of the surface sometimes encountered in forming or drawing metals that have a course grain structure.
Oscillate Wound/Ribbon Wound:
Oscillate winding is a technique that was developed to aid in winding and shipping customer orders for multiples. (Multiples are created by slitting or shearing a coil into any width or set of widths.) The slits are wound back and forth on a mandrel in the same manner that a fishing line is taken up on a reel; that is, left to right, right to left, left to right. This allows for multiples to be wrapped on one wide coil that is easily handled in shipping.
Heating a metal or alloy to such a high temperature that its properties are impaired. When the original properties cannot be restored by further heat treating, by mechanical working, or by combination of working and heat treating, the overheating is known as burning.
Aging under conditions of time and temperature greater than those required to obtain maximum change in a certain property, so that the property is altered in the direction of the initial value.
Usually refers in the steel industry to oxide of iron, of which there are three principal ones: FeO, Fe304, Fe203. In addition, there as many mixtures of these oxides which form on the surface of steel at different temperatures and give the steel different colors.
To prevent damage to the surface during shipment, handling, or storage, the material is frequently coiled with a large roll of paper paid off at the same time so that between each wrap of metal there is a wrap of paper. This paper between the steel wraps prevents the surface of the metal from rubbing against each other to damage the surface.
In a rolling mill, one pass is equivalent to one individual reduction in gauge of the entire coil being processed. A number of passes may be required to achieve the aim gauge for a particular rolling operation.
Immersion of stainless steel in a solution of nitric acid, or of nitric acid plus oxidizing salts, which restores the original corrosion resistant surface by forming a thin transparent oxide film. The treatment also dissolves any embedded or smeared iron picked up on the surface during processing.
A relatively inactive state in which the metal displays a more noble behavior than thermodynamic conditions predict or more simply defined as the reason why the metal does not corrode when it should.
A eutectoid transformation product of ferrite and cementite that ideally has a lamellar structure but that is always degenerate to some extent.
Mechanical working of metal by hammer blows or shot impingement.
Expression of reduction in gauge during any rolling process. Percent reduction equals starting gauge minus finish gauge after rolling divided by starting gauge times 100.
Nickel alloys containing about 20 to 60% Fe, used for their high magnetic permeability and electrical resistivity.
Product description for flat-roll coils which requires excellent finish and critical flatness.
A photographic reproduction of any object magnified more than ten diameters. The term micrograph may be used.
Those properties discussed in physics (exclusive of those described as mechanical properties), for example, density, electrical conductivity, coefficient of thermal expansion. The term physical properties is often used incorrectly to describe mechanical properties.
Removing surface oxides from metals by chemical or electrochemical reaction.
Microscopic imperfection of the coatings, that is, microscopic bare spots, also microscopic holes penetrating through a layer or thickness of light
Sharp depressions in the surface of the metal generally attributed to localized chemical attack by a corrosive media. In stainless steels, molybdenum additions (i.e. types 316, 317, 434) help improve pitting resistance.
The method of measuring grain size, in which the grains within a definite area are counted.
The ability of a metal to be deformed extensively without rupture.
Pounds Per Inch of Width (P.I.W.):
Pounds per inch of width refers to the weight of a one-inch wide multiple of a coil. To determine the PIW, divide the weight of the coil by its width in inches.
The transfer of molten metal from the ladle into ingot molds or other types of molds; for example, in castings.
The art of producing metal powders and of utilizing metal powders for the production of massive materials and shaped objects.
Hardening that is caused by the precipitation of a metallic compound from a super-saturated solid solution.
Precipitation Heat Treatment:
Any of the various aging treatments conducted at high temperature to improve mechanical properties.
Heating before some further thermal or mechanical treatment. For tool steel, heating to an intermediate temperature immediately before austenitizing. For some nonferrous alloys, heating to a high temperature for a long time, in order to homogenize the structure before working.
Heating an alloy or metal below the transformation temperature to facilitate softening. In some alloys (i.e. 410, 420, 440), heating above the transformation temperature can result in hardening with air cooling to room temperature.
An instrument that measures surface roughness the height and depth of surface ridges.
Pounds per square inch.
The movable part that forces the metal into the die in equipment for sheet drawing, blanking, coining, embossing and the like.
Shearing holes in sheet metal with punch and die.
PVC is an abbreviation for polyvinyl chloride plastic, a material used to coat stainless steels. The heavy plastic ranges from 0.001 to 0.006 inches thick, normally has a dye in it to color it (white or black) and one side has a contact adhesive coating. Customers use it to protect the surface of the stainless while they are doing manufacturing operations on it and then peel it off after they are finished with those operations. PVC should not be allowed to remain on the stainless for extended periods of time, especially in sunlight, as it will adhere to the stainless more and more tightly as time goes on and can, in extreme cases, be virtually impossible to remove.
An instrument of any of various types used for measuring temperatures.
Refers to the suitability and integrity of the steel for the purpose or purposes for which it is intended.
Aging that occurs after quenching following solution heat treatment.
Quenching and Tempering:
A process by which steel is rapidly cooled from above its upper critical temperature to a temperature far below this range. Water or oil is normally used to accelerate the cooling. In the as-quenched condition, the product is not suitable for most commercial applications because of its lower ductility and hardness. The steel must, therefore, be tempered in order to soften it somewhat to improve its ductility and toughness. Tempering is a heat treatment done at lower temperatures usually in the range between 400°F and 1200°F.
RA & RMS:
RMS (root mean square) is the measure of the surface texture of a material. Texture is a deviation of the actual surface profile from the nominal surface, including roughness and waviness. RA has replaced RMS as the US standard because it averages important detail needed to analyze complex engineering surface.
Edges of Sheet or Strip which are torn, split, cracked, ragged or burred or otherwise disfigured.
In inspection, the difference between the highest and lowest values of given quality characteristic within a single sample.
Removal of residual stresses from cold-working as the result of annealing.
Process whereby the distorted grain structure of cold worked metals or alloys is replaced by a new strain free grain structure during annealing above a specific minimum temperature (recrystallization temperature).
A temperature, usually just higher than the transformation range, employed in the heat treatment of steel to refine the structure — in particular, the grain size.
A heat-resistant material, usually nonmetallic, which is used for furnace linings and such.
A term applied to those alloys which due to hardness or abrasiveness present relative difficulty in maintaining close dimensional tolerances.
Elements present in a metal or alloy that are not deliberately added during melting and refining; in most stainless steels for strip product, residual elements might be phosphorus, sulfur, tin, and lead.
A reversing mill is used to reduce material to gauge. The steel enters the rolling mill from one side, passes through the other side and then comes back through the mill again. Normally, it will go left to right through the mill a number of times being rolled a little thinner each time it goes through.
A term applied to a common method of winding strip steel layer upon layer around an arbor or mandrel.
A slight transverse wave or shadow mark appearing at intervals along the piece.
Rock Candy Fracture:
A fracture that exhibits separated-grain facets, most often used to describe intergranular fractures in large grained metals.
Rockwell Hardness (HRB or HRC):
Rockwell is a method of measuring the hardness of materials. Hardness, in this sense, means resistance to penetration. The test gets its name from Stanley P. Rockwell who devised the test and original machines, later selling the rights. The test measures the hardness by pressing an indentor into the surface of the steel with a specific load and then measuring how far the indentor was able to penetrate. While there are a number of Rockwell tests, the common is Rockwell B. Rockwell C is used on hard materials. When the material is very thin, lighter loads must be used. Resulting in Rockwell 30T, 1ST, Rockwell 15-N, 30-N scales. There are conversion charts which will allow conversion from one method of hardness to another, but it must be remembered that these conversion charts cannot precisely convert from one to another. Unfortunately, most customers do not recognize that there are different Rockwell tests and/or do not realize that conversion charts are not totally accurate.
Concave or convex defects introduced on the surface of the metal or alloy coil by rolls. A combination of roll pressure and the defects in the rolls or contamination on the rolls determine the severity of the roll marks. Roll marks are generally repetitive.
Finished edges, the final contours of which are produced by side or edging rolls. The edge contours most commonly used are square corners, rounded corners and rounded edges.
The process in which a series of staggered rolls of small diameter is used to remove bow and waves from sheet. While passing through the roll, the sheet is bent back and forth slightly and is delivered approximately flat.
An operation used in forming sheet.
Corrosion mechanism of iron and steel when iron oxide is formed. Passive stainless steel does not rust, but iron or steel contamination on the surface will, which gives consumer a false impression concerning the stainless steel itself. Passivation of stainless steel parts in a nitric acid solution will remove this contamination while maintaining the passivity of the stainless steel surface.
Salt Spray Test:
An accelerated corrosion test in which metal specimens are exposed either continuously or intermittently to a fine mist of salt-water solution. An accelerated salt-spray test used by automotive is the CASS test.
An imperfection consisting of a thin, flat piece of metal attached to the surface of a sand casting or ingot. A scab usually is separated from the casting proper by a thin layer of sand or refractory and is attached to the casting along one edge. An erosion scab is similar in appearance to a cut or wash.
Scale is a layer of oxide that forms on the surface of steel when it is exposed to oxygen at elevated temperatures. Scale can form on the steel in the reheat furnace, the soaking pits, in the hot mill, and in the annealing furnaces.
Resistance to corrosion by air at elevated temperatures. In stainless steels, Chromium is the most important element for increasing the scaling resistance particularly at temperatures above 1000°F.
Mechanical finish produced by applying Scotch Brite (registered trademark of 3M Co.) to the surface of the metal to give a fine scratch pattern appearance. It is also useful in reducing tool wear (i.e. removal of abrasive surface oxides).
On the surface of metal, an unwelded ford or lap which appears as a crack, usually resulting from a defect obtained in casting or in working.
Steel that is incompletely deoxidized and contains sufficient dissolved oxygen to react with the carbon to form carbon monoxide and thus offset solidification shrinkage.
Sendzimir Cold Rolling Mill:
Frequently referred to as Z mill which features 1-2-3-4 top and bottom roll arrangement; each work roll is supported throughout its entire length by two first intermediate rolls, that are, in turn, supported by three second intermediate rolls which transfer the roll separating forces to a rigid one piece cast steel housing through four backing assemblies. A Z-mill operates with very small diameter work rolls. The roll setup facilities exertion of high forces on the coil which in turn accomplishes rolling to very thin gauges and tight tolerance.
Term normally used for 17-7PH™1 precipitation hardenable stainless steel. However, whenever it is used by a potential customer, it should be clarified that they mean 17-7PH™1. In the past, 17-7 has been used to signify type 301 which also is 17% Chromium -7% Nickel stainless steel, but not precipitation hardenable.
- Less than .1876″ thick, and more than 23-15/19″ wide, and cut to length.
- Sheet coil. Sheet not cut to a length, but coiled.
- Less than .1876″ thick, and under 24″ wide.
- Over .1875″ thick, over 10″ wide, and cut to length.
- Semi-finished steel block; width at least twice its thickness.
- Sheet is material which measures under 3/16 inch (4.76 mm) in thickness and 24 inches (609.6 mm) and over in width.
A type of cutting operation in which the metal object is cut by means of a moving blade and fixed edge or by a pair of moving blades that may be either flat or curved.
Shot blasting consists of attacking the surface of a material with one of many types of shots. Normally this is done to remove something on the surface such as scale, but it is also done sometimes to impart a particular surface to the object being shot blasted, such as the rolls used to make a 2D finish. The shot can be sand, small steel balls of various diameters, granules of silicon carbide, etc. The device that throws the shot is either a large air gun or spinning paddles which hurl the shot off their blades.
Skid & Shroud:
Skids are platforms upon which material is placed for shipment. These platforms are normally of wooden boards nailed to 2 x 4’s or 4 x 4’s so that a fork truck can get its forks underneath the platform. The material being shipped is usually fastened to this platform by narrow strips of thin metal called banding. To shroud means to cover the steel being shipped with heavy, water-proof paper to protect it from moisture and handling damage during transit.
To skin pass material is to give it a very light pass on a rolling mill after final annealing. There is essentially a minimum reduction in thickness during this last pass. It is usually done for one of these three reasons:
- to flatten the material
- to impart a particular surface to the steel from the rolls
- to cold-work the material to slightly increase its mechanical strength
Edging process on flat-rolled metal and alloy strip. After metal removal, a #5 square edge is produced.
Slab describes the size and shape of material at an early stage of processing. A slab is typically 6 inches thick, 51 inches wide, and around 200 inches long. It will be processed to become a hot roll band or a plate. Slabs may come directly from the continuous caster or be formed from ingots via the blooming mill.
To slit steel is simply to cut it. The most common slitter available is a pair of scissors. The slitters used in the mill have circular blades that resemble washers. These rotate as the steel passes through them. The slitters have a payoff reel and a take-up reel which pass the steel through the slitter knives. Between these two reels are two shafts, one above the steel and one below the steel. The round slitter knives are placed on the shafts and adjusted so that they cut off the edges of the steel to produce a good edge and/or cut the steel into narrow strips of the width the customer wants.
Slitting stock is produced with the knowledge that the product will be further processed by mill customer. Mill produces the final gauge but not the final width. The customer will do additional slitting/shearing.
Defects in the nature of irregularly shaped pieces of steel clinging loosely to finished steel. Slivers may result from defective composition (over-oxidized, high sulfur); defective teeming of molten steel, defective heating (burning), tearing of corners in early stages of rolling, etc.
A metallurgical thermal processing operation in which the metal or matte is separated in fused form from nonmetallic materials or other undesired metals with which it is associated.
Prolonged heating of a metal at selected temperature.
Reduction in ductility of a metal or alloy associated with local penetration by molten solder along grain boundaries.
Solution annealing is a process performed on steels. The process consists of heating the material up to a temperature above 1950°F and holding it long enough for the carbon to go into solution. After this, the material is quickly cooled to prevent the carbon from coming out of solution. Solution-annealed material is in its most corrosion-resistant and ductile condition.
Solution Heat Treatment:
A process in which an alloy or metal is heated to a suitable temperature, is held at that temperature long enough to allow a certain constituent to enter into solid solution, and is then cooled rapidly to hold that constituent in solution. Most solution heat treatments soften or anneal.
An instrument using an extended surface — a photographic plate or film, or a fluorescent screen — for receiving the X-ray diffraction pattern.
The procedure of making sheet metal discs into hollow shapes by pressing the metal against a rotating form (spinning chuck) by a tool.
An electric-resistance welding process in which the fusion is limited to a small area. The pieces being welded are pressed together between a pair of water-cooled electrodes through which an electrical current is passed during a very short interval so that fusion occurs over a small area at the interface between the pieces.
Normally refers to full hard and extra full hard condition depending on the alloy, specification and customer. In the case of type 301, customer’s expectations should be made clear to avoid error.
Condition that occurs when a flat-rolled metal or alloy is cold-worked; upon release of the forming force, the material has a tendency to partially return to its original shape because of the elastic recovery of the material. This is called “Springback” and influenced not only by the tensile and yield strengths, but also by thickness, bend radius and bend angle.
Additions of elements to 300 series stainless steel which are stronger carbide formers than Chromium. These carbide forming elements (Titanium in type 321 and Columbium in type 347) essentially “tie up” all of the Carbon present preventing Chromium from reacting with Carbon and thus avoiding sensitization and serious loss of corrosion-resistance.
The broad classification of iron-base alloys (50% minimum iron) containing at least 10% chromium that are known for their excellent corrosion- and heat- resistance. Other elements are also added to form alloys for special purposes in addition to the corrosion-resistance imparted by the chromium. Some of these elements are: nickel for increased corrosion resistance, ductility and workability; molybdenum for increased corrosion-resistance, particularly resistance to pitting, increased creep strength and high- temperature strength; columbium and titanium for stabilization; sulfur and selenium for improved machinability.
An alloy of Carbon and Iron.
Straight Chrome (Martensitic/Ferritic):
As the name indicates, the straight chromes essentially contain only chromium as their major alloying element. To become a stainless steel, a material must have a minimum chromium of 10.5% with chromium in the mid 20’s being the normal highest chromium. All of the straight chromes have a ferritic structure in the annealed condition. This ferritic structure is quite soft and, accordingly, not exceedingly strong. However, the martensitic stainless with their higher carbons have the ability to be made very hard by heat treatment. Typical of the non-hardenable ferrites are types 409, 430, 434, and 436, while martensitics are types 410, 420, and 440.
An increase in hardness and strength caused by plastic deformation at temperatures lower than the recrystallization range.
Strand Casting: (see Continuous Casting)
Strand casting is the direct casting of steel from the ladle into slabs. When two or more heats are cast without interruption, the process is called continuous strand casting. In strand casting, a heat of steel is tapped into a ladle in the conventional manner. The liquid steel is then teemed into a tundish which acts as a reservoir to provide for a constant casting rate. The steel flows from the tundish into the casting machine and rapid solidification begins in the open ended molds. The partially solidified slab is continuously extracted from the mold. Solidification is completed by cooling the moving steel surface. More than one strand may be cast simultaneously, depending upon the heat and slab size. A reduction in size may be carried out by hot-working the product as it exists from the strand prior to cutting the cast section to length. Chemical segregation is minimized due to the rapid solidification rate of strand cast product. Steel produced from a strand-casting operation is always fully killed steel, thus is generally considered to have excellent surface quality. Approximately 50% of the steel used in producing plate products is from strand castings.
The ability of a material to resist applied forces.
Material criteria used primarily in the transportation industry. High ratios for Titanium and Aluminum alloys stress the need to develop higher strength inducing process for heavier Iron, Nickel and Cobalt base alloys to improve their strength-to-weight ratios.
Failure by cracking from the combined effects of corrosion and stress. One of the important characteristics is the absence of visual overall attack. The metal or alloy appears to be satisfactory except where it is cracked.
A process of reducing residual stresses in a metal or alloy by heating to a suitable temperature and holding for a sufficient length of time.
Stress Rupture Test:
A method of evaluating elevated-temperature durability in which a tension-test specimen is stressed under constant load until it breaks. Data recorded commonly include: initial stress, time to rupture, initial extension, creep extension, reduction of area at fracture. Also known as creep-rupture test.
A hydraulic stretching of material past its yield point to impart permanent deformation to obtain better-than-rolled flatness.
Strip is material which measures 3/16 inch (4.76 mm) and under in thickness and under 24 inches (609.6 mm) in width.
An annealing treatment in which a steel is heated to a temperature below the A1 temperature and then cooled slowly to room temperature.
The layer of metal underlying a coating, regardless of whether the layer is base metal.
A generic term covering several processes applicable to a suitable ferrous alloy that produce, by quench hardening only, a surface layer that is harder or more wear resistant than the core. There is no significant alteration of the chemical composition of the surface layer. The processes commonly used are induction hardening, flame hardening and shell hardening. Use of the applicable specific process name is preferred.
The surface quality of flat-rolled stainless products may vary according to manufacturing practices. It is important to both producer and purchaser that surface-quality requirements be clearly established. It must be recognized, however, that some degree of variation in surface quality may exist from lot to lot. It is customary to visually inspect products in the “as-rolled” condition to ensure their freedom from injurious imperfections such as gross slivers, snakes, cracks, blisters, and gouges. Minor pits, seams and scratches are not considered injurious and are not customarily removed in plate only. It should be recognized that when surfaces are subjected to descaling operations subsequent to mill inspection, imperfections may be disclosed that were not visible in the “as-rolled” condition. Therefore, products that will be inspected after descaling necessitate special surface conditioning and closer inspection than customarily employed, and the surface requirements should be established in each instance. Flat roll product for certain cold-drawing or cold-pressing operations may require a high degree of surface finish, even to the need for a surface-ground finish.
Steel block where material is wound when rolling or slitting.
Arrangement of rolling mills, in direct line, allowing the metal to pass from one set of rolls into the next.
Surface discoloration on a metal, usually from a thin film of oxide or sulfide.
Transverse slipping of successive layers of a coil so that the edge of the coil is conical rather than flat.
Light cold-rolling of sheet steel. The operation is performed to improve flatness, to minimize the formation of stretcher strains, and to obtain a specified hardness or temper.
Carefully selected and controlled heat-treating operation performed on steel after it has been fully hardened by heat treatment. The operation results in a desired degree of change in the internal structure and mechanical properties. The mechanical properties resulting from tempering are usually intermediate between the fully hardened and the annealed properties.
The value obtained by dividing the maximum load observed during tensile testing by the specimen cross-sectional area prior to test initiation. Tensile strength is expressed in psi (pounds per square inch), ksi (1000 pounds per square inch) or a metric equivalent such as mpa (milli pascals) or N/mm (newtons per square millimeter). Simply put, tensile strength is the maximum load a given cross-section of material can withstand before breaking apart.
Tensile testing is a procedure to calculate the yield strength and the ultimate tensile strength of the material. The procedure begins with a specially prepared specimen, usually 8 inches long and with a half-inch reduced section in the middle. The specimen is put into a machine which grips the ends, and then pulls the specimen apart. As the machine does this, it measures the load required to make the material go from the elastic to plastic deformation and the load required to actually break the material. By factoring in the original cross-sectional area of the reduced section at the middle of the specimen, it is possible to calculate the pounds per square inch when the material went from the elastic to plastic deformation. This is the yield strength. Again using the cross- sectional area and the load required to break the specimen, you can calculate the ultimate tensile strength (or simply tensile strength).
Mechanical operation where coiled metal or alloys are stretched beyond their yield points. Tension level can improve flatness and camber.
A mechanical operation where coil metal is stretched beyond its yield point.
Tension Testing (Tensile Testing):
A mechanical test employed to determine both strength and ductility properties of material. Measurements obtained from a tensile test include ultimate tensile strength, yield strength and percent elongation.
Specified limits of deviation from a measurement can be dimensions, strength, analysis.
The permissible deviation from the desired value.
Any high carbon or alloy steel capable of being suitably tempered for use in the manufacture of tools.
A gradual deterioration of tools and dies. In the case of fabrication of stainless steels, the surface oxides of the stainless gradually either abrade or build up on the tooling. Other factors (high hardness, non-metallic inclusions) can also accelerate tool wear.
A twisting action resulting in shear stresses and strains.
Toughness may be defined as the ability of a material to accept applied stresses by either elastic or plastic deformation, depending on the stress level, without sudden brittle failure.
A constitutional change in a solid metal, e.g., the change from gamma to alpha iron, or the formation of pearlite from austenite.
Literally, ‘across’, usually signifying a direction or plane perpendicular to the direction of working. Tensile testing can be done in this direction.
Cleaning articles by rotating them in a cylinder with cleaning materials.
A method for removing the surface from a circular piece by bringing the cutting edge of a tool against it while the piece is rotated.
A stand having only two rolls. Some two-high mills are reversing with screw-downs to adjust the rolls; others are one way only and may or may not have screw-downs for roll adjustment and may or may not be a part of a continuous mill.
Ultimate Tensile Strength:
The maximum stress in pounds per square inch (psi) that causes the material to fracture.
A rolling mill in which rolls with a vertical axis roll the edges of the metal stock between some of the passes through the horizontal rolls.
Defines the chemical analysis (Unified Numbering System) as a joint responsibility of the SAE and ASTM.
Vacuum is best characterized as a lack of atmosphere (i.e. air, oxygen or other gases). Hence when metals or alloys are heated to high temperatures in a vacuum furnace, there is essentially no oxygen present to oxidize and discolor the surface of the material. Unfortunately, vacuum annealing is not conducive to strand annealing (i.e. uncoiling, heating and recoiling).
Melting in vacuum, usually by electrical induction, to remove gaseous contaminants from the metal or alloy. CEVM, VAR and VIM are terms relating to this process.
Vickers Hardness (Test): Standard method for measuring the hardness of metals, particularly those with extremely hard surfaces; the surface is subjected to a standard pressure for a standard length of time by means of a pyramid shaped diamond. The diagonal of the resulting indention is measured under a microscope and the Vickers Hardness value read from a conversion table.
Out-of-flat condition generally introduced during cold-rolling of metal or alloy coils. Edge waves are more common and generally can be minimized by allowing for “dropping a cut” during edge slitting. It is also possible to produce wavy edges during slitting.
The feasibility of welding a particular metal or alloy. A number of factors affect weldability including chemistry, surface finish, heat-treating tendencies, etc.
Wedge: (See Crown)
In any given coil the variance in width from one edge to the opposite edge.
The hardness developed in metal as a result of cold work. The degree to which hardness and strength increases varies widely with different metals and alloys. Among the stainless steels the chromium-nickel grades are by far the most responsive.
A wavy condition obtained in drawing in the area of the metal that passes over the draw radius. Wrinkling may also occur in other reforming operations when unbalanced compressive forces are set up.
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Yield of a Coil:
For non-standard grades of steel, price is affected by the weight ordered. Yield of coil is the expected ship weight of a single coil of a particular type of steel and is used in the calculation of price.
The load per unit of original cross-section at which, in soft steel, a marked increase in deformation occurs without increase in load.
The stress at which a material exhibits a specified limiting proportionality of stress to strain. As the tensile load on a specimen is increased through the elastic (i.e. no permanent deformation) range, a stress will be reached at which the specimen will begin to deform in a plastic manner (i.e. permanent deformation which will not recover upon release of load). The procedure employed to measure this stress is called “offset method”, hence yield strength is noted in parentheses by 0.2% offset. Yield strength is specified in psi. (pounds per square inch), ksi (1000 pounds per square inch) or a metric equivalent (MPA or N/mm). Materials stressed beyond their yield strength will take a permanent set; the magnitude of set depends upon the stretching incurred beyond the yield strength.
The full name for a Z-mill is Sendzimir mill. A Z-mill operates with a very small diameter work roll, normally about 2 inches, backed up by a number of rolls in a pyramid-shaped stack. This roll set up allows you to exert extremely high forces through the work roll and yet keep the work roll from extreme flexing. The take-up roll on the Z-mill also exerts a tension on the coil as it comes through the mill. The combination of high pressure and tension makes the mill capable of rolling material thin and flat.