Glossary

This glossary is designed to make sure that you know everything about coil processing inside and out. All of the words and phrases you read throughout the website will have a simpler and easier to read explanation here.

Age Hardening - This process increases hardness and strength for the price of ductility. Process usually follows rapid cooling or cold working.

Aging - The tendency of some steels to change in physical properties over time, at room temperature. The change is usually accompanied by an increase in hardness, yield and tensile strength and a decrease in ductility and impact.

Annealing - A process involving heating and cooling metals which causes metal softening. It increases the ductility of a metal and its workability.

Bend Tests - Various tests used to determine the ductility of sheets or plates that are subjected to bending. These tests may include determination of the minimum radius or diameter required to make a satisfactory bend and the angle through which the material can be bent without failure.

Black Annealing - A process of box annealing with ferrous alloy sheets, strips, or plates without the use of a deoxidizing atmosphere, either after hot working, pickling, or cold working.

Blister - A raised spot on the surface of metal due to expansion of gas. This causes subsurface metal separation such as; inclusions and small laminations.

Blowhole - A hole produced during the solidification of a metal, by which gas is held in small pockets.

Blue Brittleness - Brittleness occurring in steel when the steel is being worked within the rage of 300 ° F to 700 ° F, or after the cooling from this temperature range.

Bluing - A treatment for improving the appearance and resistance to corrosion of ferrous alloys by subjecting the surface (initially free from scale) to the action of air, stream, chemicals or other agents at a suitable temperature. Thus forming a thin blue film of oxide.

Bonderizing - Treating cold rolled or galvanized steel surfaces with phosphate to improve paint-adherence.

Box Annealing - A process of annealing ferrous alloys in a suitable closed metal container (with or without packing material) in order to minimize oxidation. The charge is usually heated slowly to a temperature below the transformation range, but sometimes above or within it, and is then cooled slowly.

Bright Annealing - A 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.

Brittleness - A tendency to fracture without appreciable deformation.

Burr - A rough or sharp edge left on metal by a cutting tool such as shear blades or slitter knives.

Camber - Is the deviation of a side edge from a straight edge. Measurement is taken by placing a straight edge on the concave side of a sheet and measuring the distance between the sheet edge and the straight edge in the center of the arc. Camber is caused by one side being elongated more than the other.

Capped Steel - Capped steels have characteristics similar to those of rimmed steels, but to a degree intermediate between those of rimmed and semi-killed steels. The gas entrapped during solidification is in excess of that needed to counteract normal shrinkage, resulting in a tendency for the steel to rise in the mold. The capping operation limits the time of gas evolution and prevents the formation of an excessive number of gas voids within the ingot. Capped steel is generally cast in bottle-top molds using a heavy metal cap.

Carbon Steel - also termed "ordinary steel", "straight carbon steel", "plain carbon steel", this steel owes its properties to the presence of carbon. There is no substantial presence of any other alloy, giving it the carbon related name.

Center Buckle - A condition in the band of steel where the center (in the direction of rolling) is longer that the edges and has a wave or buckle

Checking - A series of transverse cracks appearing on the edge o the strip. Checking results from using rough, or cracked ingot molds, so that resistance is offered to the natural contraction of the steel. Another common cause of checking is rolling the ingots at too low a temperature.

Chew-Up or Lap - Caused in the hot mill when the band or strip runs off pass and is folded over by entry guides and continues through mill double over. Chew-up or lap can also be caused by a pipe-type lamination.

Coarse Grain - An open or coarse grain condition which makes the steel unsuitable for customer's use either due to the undesirable appearance of the finished part or because of breakage which occurs when it is drawn.

Coating Weight - The amount of zinc on a galvanized sheet measured in ounces per square foot.

Cold Reduction Mill - Sheet and strip are cold reduced to the desired thickness for the following reasons: 1) to obtain the desired surface, 2) to impact desired mechanical properties, 3) to make gauges lighter than the hot strip mill can produce economically, and 4) to produce heet and strip of more uniform thickness. Cold reduction can be accomplished either in sheets or in coils, but reduction in coils is considerably more economical and is the more common practice.

Cold Work - Plastic deformation at such temperatures and rates that substantial increases occur in the strength and hardness of the metal. Visible structural changes include changes in grain, shape, and in the some instances mechanical twinning or banding.

Corrective Leveling - Capability of a leveling machine to remove or reduce shape defects across the strip, coil, or sheet in addition to flattening lengthwise curvatures.

Cover Sheets - Top and bottom sheets of lift.

Crop - The end or ends of an ingot, slab, or coil that contain the pipe or other defects to be cut off and discarded.

Cross Breaks - Hard spots caused by abrupt deformation of the strip after hot rolling and due to stressing beyond the elastic limit of the metal. Usually occurs when coiled material is sheared into flay sheets.

Crown - The crown, or center, refers to the tendency of a sheet to be heavier in gauge in the center than on the edges. It may be caused by the use of hollow, or worn back-up rolls, work rolls improperly ground, or excessive work in the last finishing stand.

Decarburization - The loss of carbon from the surface of a ferrous alloy as a result of heating in a medium that reacts with the carbon.

Directional Properties - The loss of carbon from the surface of a ferrous allot as a result of heating in a medium that reacts with the carbon.

Dross Streaks - Excess zinc globs on the surface of hot galvanized sheets.

Ductility - The property that permits permanent deformation before fracture by stress in tension. Edge Buckle - Edge buckle is similar to center buckle except that the condition occurs in one, or both edges, of the strip and is generally confined to a narrower portion of the width.

Edge Build-Up - This term refers to the zinc build up on the edges of the strip in the continuous galvanizing process.

Elastic Deformation - Stretching of the material below the point at which a permanent "set" takes place. That is, in the range where the metal acts spring like or elastic.

Elongation - This term is used on order specifying tensile tests on which a minimum elongation between given points and distances has to be met. This elongation is expressed as percent of stretch over a given length.

Feather edge - A sharp reduction in gauge in the edge of a band which is caused by grooves worn in rolls due to extensive rolling of the same width material. The gauge variations on a feathered edge generally does not extend in from the edge more than one inch.

Finishing Temperature - The temperature at which hot mechanical working of metal is completed.

Fire Cracks - An irregular pattern of lines on the surface of a sheet caused by rolling with a fire cracked roll. Fire cracks will develop when a roll is not properly cooled.

Fish Tail - A defect which is due to the area near the edge of the partially reduced slab elongation more than the center and usually resulting in a tail end which is "U" hsaped. This is, t a great degree, overcome by cropping, or squaring the end just prior to entering the finishing train.

Flaking - Poor adherence of the zinc coating to the steel base.

Flattener - Basic machine used for removal or reduction of lengthwise curl or bending in strip, coil, or sheet. Generally employing 5, 7, or 9 opposed rolls with relatively large diameters.

Fluting - The kinking, or breaking of a sheet generally caused by curing the sheet on too small a diameter. Fluting, or paneling as it is often called, can be avoided by working the steel before bending. Cold working, such as temper rolling, stiffens a sheet sufficiently to prevent it from kinking. Steel with a definite yield point (a visible break in the stress-strain curve) will generally tend to flute.

Groove Marks - Lines on galvanized sheet caused by the grooves in the exit rolls.

Heat Pattern - A light pattern of red oxide on the surface which is usually heavier on the top side of the steel as rolled. This is a form of rolled-in-scale and is caused by the steel being too got after it has passed through the hydraulic sprays at the entry side of the finishing train.

Inclusions - Particles of impurities (usually oxides, sulfides, silicates, etc.) that are held mechanically, or age formed during the solidification, or by subsequent reaction in the solid metal.

Killed Steel - Killed steels are characterized by a more-uniform chemical composition and properties as compared to other types; they are, however, some variations in composition from surface to center and from top to bottom of the ingot.

Striger-type Lamination - result from inclusions, usually oxides and sulfides, which are more numerous in rimmed steel along the secondary blowhole zone in the bottom third of the ingot and in the center of the core zone near the top. IN the case of killed steel ingots, the position of these stringer inclusions depend upon the kind of inclusion present, but they are usually more numerous at the top and center.

Pipe-type Lamination - as a result of the shrinkage of steel during freezing, or solidificaton, a cavity is formed at the top of all ingots. In the case of rimmed steel ingots (this cavity or pipe as it is called) is porous and usually does not extend below the 85% yield position. Semi-killed and killed ingots from the 85% down to as low as the 70% yield position in some cases. If the steel is properly made and well heated, the walls of the pipe cavity usually weld together when the ingot is rolled, so that the pipe is not visible in the product.

Leveling - The process by which a leveling machine flattens metal strip, coil, or sheets by bending it up and down over the interrupting arcs of upper and lower sets of long, slender work rolls.

Modulus Of Elasticity - The number which represents the relative "springiness" of a given type of metal.

Normalizing - Heating to a temperature about 100 ° F above the critical range, as indicated by the iron carbon diagram, and cooling in still air. This process allows for more uniform metal properties in the steel.

Off Gauge - Material Outside the allowable gauge range. Head and tail ends of coils are generally off gauge.

Orange Peel Effect - A surface roughening encountered in forming products from metal stock that has a coarse grain size.

Oxidizing - Chemical union of iron and oxygen to form an oxide or scale.(Rust)

Pass - The process of putting metal through a rolling mill.

Paint Tite - Process term referring to the treatment of galvanized sheet in a phosphate solution to promote paint adherence.

Pickle - Chemical or electrochemical removal of surface oxides.

Pits - Depressions in the surface of a sheet or strip caused by foreign material, such as scale, being rolled into the steel at the hot strip mill and falling out in subsequent operations.

Pipe - A cavity formed by contraction in metal (especially ingots)during solidification of the last portion of liquid metal.

Plastic Deformation - Permanent deformation occurring in forming of metal which occurs after elastic limits have been exceeded.

Rimmed Steel - Rimmed steels are characterized by marked differences in chemical composition across the section and from top to bottom of the ingot. They have an outer rim that is lower in carbon, phosphorous and sulfur than the average composition of the whole ingot, and an inner portion, or core, that is higher than the average in those elements.

Scabs - Scabs are caused by the steel splashing from the stool at the start of the pour and sticking to the mold walls. In the case of a leaky nozzle, or a fan flaring shaped stream, the steel may also touch and stick to the mold sides and, in this case, a curtain type of scab may be formed higher up in the ingot.

Scales - Iron oxide on surface of steel - surface of a hot rolled sheet as rolled.

Scarfing - Cutting the surface of slabs, ordinarily by using a gas torch, to remove surface defects prior to rolling at the mill.

Scratch or Gouge - This type of defect can be recognized, in most cases, as to its source. If the scratch or gouge occurs in the hot strip mill, there will be an oxide which has formed at the base of it. Scratches or gouges occurring at the finishing end can be recognized by the bright appearance at the base of the defect which is indicative of oxide removal after the steel has cooled.

Shear Strength - is usually 50-70% of Tensile Strength and is a maximum shear stress which a material can withstand without a rapture and is the maximum load required to cut off a specimen in such a way that the resulting piece are separate from each other.

Seam - A small crack or crevice in the surface of steel which has been closed, but not welded by subsequent rolling. It is usually produced by some defect either in casting, or in working, such as blowholes that have become oxidized.

Segregation - Non-uniformity of composition in steel caused by a separation of one or more of the elements during the solidification of an ingot. Since liquid steel is a solution of various elements in molten iron, some of these elements reach their freezing points before others as the steel cools. Those elements with the lower melting point would segregate in the last portion of the ingot to solidify.

Semi-Killed - Semi-killed steels are characterized by variable degrees of uniformity in composition and have properties intermediate between those of killed and rimmed steels.

Slivers - Slivers are due to detective teeming of the molten metal and to a tearing of the corners of the steel in blooming, roughing or finishing. Tearing is attributed to many things, such as over oxidation in the open hearth, or burning during reheating or soaking.

Soaking - Holding steel at a temperature sufficiently long to allow complete and uniform penetration of the heat.

Spangle - Zinc crystallization pattern on a galvanized sheet.

Spleter - Common term for industrial zinc.

Speroidizing - A process of heating and cooling that produces a rounded or globular form of carbide in steel.

Stretcher Strains - Stretcher strains occur during the forming of drawing of a product.

Strain - The amount of elongation or compression that occurs in a metal at a give stress or load.

Stress - The amount of force, which is applied to the cross section of the material.

Tensile Strength - Or ultimate tensile strength, is the cross sectional stress in tension at which failure or fracture of the metal occurs.

Tension Leveling - The optimum method of leveling and correcting shape defects in strip or coil. Principle involves relatively expensive equipment on which strip or coil is rewound slightly faster than it is unwounded, resulting in plastic deformation or yielding of the metal throughout its cross section.

Top Dross - Skimming for the continuous galvanize pot. Composition consists of approximately 87% zinc, 5% aluminum, and 6% to 8% carbon.

Thin Skin - Term applied to the physical condition of an ingot that has a very narrow skin zone. It is found in rimmed and semi-killed steel only and it is caused by and improper balance between heat, carbon and oxygen content at the tapping and pouring state of the steel making process. A thin skin has a tendency to break during rolling resulting in seams.

Wavy Edge - A condition in the band of steel where the edges are longer than the center.

White Rust - Corrosion product of zinc, generally in connection with galvanized sheets. Material consists mainly of basic zinc carbonate.

Work Hardening - Hardening of metal resulting from mechanical working, particularly cold working.

Yield Strength - The stress or force at which some permanent deformation of the material occurs and the stretching is no longer strictly elastic.

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