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Steel Glossary
Plain-language definitions of 49+ steel industry terms for buyers, engineers, and procurement teams.
Annealing
A heat treatment process in which steel is heated to a specific temperature and then cooled slowly, typically in a furnace. Annealing relieves internal stresses, improves ductility, and softens the metal — making it more suitable for further processing such as cold rolling or deep drawing.
See also: Cold Rolling · Normalising · Temper Rolling
As-Rolled
Steel supplied in the condition as it comes off the rolling mill, without any subsequent heat treatment. IS 2062 and IS 808 material is typically supplied in the as-rolled condition unless a specific delivery condition (such as normalized) is specified.
See also: Normalising · IS 2062
View related standardBase Metal
The primary steel substrate before any coating or surface treatment is applied. In galvanized sheets, the base metal is typically a hot-rolled or cold-rolled steel coil that undergoes the galvanizing process.
See also: Galvanizing · Substrate · Hot-Dip Galvanizing
Bending Radius
The minimum radius to which a steel section can be bent without cracking or fracturing the outer surface. Expressed as a multiple of the material thickness (e.g., 1×t, 2×t). High-strength and higher-carbon steels typically require larger bending radii.
See also: Ductility · Elongation · Cold Rolling
Bright Annealing
Annealing carried out in a controlled atmosphere (typically nitrogen or hydrogen) to prevent surface oxidation, resulting in a bright, clean surface finish. Used for cold-rolled CR sheets and precision strip products.
See also: Annealing · Cold Rolling · IS 513
View related standardCarbon Equivalent (CE)
A formula used to estimate the weldability of steel by accounting for the effect of carbon and other alloying elements on hardenability. A lower CE value indicates better weldability. IS 2062 specifies maximum CE values for each grade to ensure weldability.
See also: Weldability · IS 2062 · Heat-Affected Zone
View related standardCharpy Impact Test
A standardized test that measures the energy absorbed by a steel specimen when struck by a swinging pendulum. The result (in Joules) indicates the toughness of the material at a specified temperature. IS 2062 E-quality grades mandate impact testing.
See also: Toughness · IS 2062 · Notch Toughness
View related standardCold Rolling (CR)
A metalworking process in which hot-rolled steel coils are passed through rollers at or near room temperature to reduce thickness and improve surface finish. Cold rolling increases yield strength and hardness through work hardening. CR sheets conform to IS 513 for plain carbon steel.
See also: Hot Rolling · Work Hardening · IS 513 · Annealing
View related standardCoil Set
The residual curvature present in flat steel sheets after they have been uncoiled from a coil. It appears as a natural bow or curve along the rolling direction. Cut-to-length processing with levelling corrects coil set to produce flat sheets.
See also: Levelling · Cut to Length · Flatness
Corrosion Allowance
Additional material thickness specified in pressure vessel and structural designs to compensate for the anticipated loss of metal due to corrosion over the design life. Commonly specified for pressure vessel plates under ASTM A516.
See also: ASTM A516 · Pressure Vessel · Coating
View related standardDeep Drawing
A sheet metal forming process in which a blank is drawn into a die cavity to form a cup or box shape. Requires steel with high ductility, low yield strength, and a high r-value (normal anisotropy ratio). IS 513 DD and EDD grades are specifically qualified for deep drawing.
See also: IS 513 · Ductility · r-value · Anisotropy
View related standardDeoxidation
The process of removing dissolved oxygen from molten steel before solidification. Methods include killed (silicon or aluminium deoxidized), semi-killed, and rimmed steel. Fully killed steels have better through-thickness uniformity and are required for pressure vessel and impact-tested applications.
See also: Killed Steel · Rimmed Steel · Ladle Refining
Dual Certification
A steel product certified to meet the requirements of two different standards simultaneously — e.g., IS 2062 E250 and ASTM A36, or EN 10025 S235 and IS 2062 E250. Dual-certified material reduces inventory by satisfying multiple specifications.
See also: IS 2062 · ASTM A36 · EN 10025-2 · Mill Test Certificate
View related standardElongation
The percentage increase in gauge length of a test specimen at the point of fracture in a tensile test. Elongation is a key measure of ductility — higher elongation means the steel can be deformed more without breaking. IS standards typically specify minimum elongation values at 50mm or 80mm gauge length.
See also: Ductility · Tensile Strength · Gauge Length
Extra Deep Drawing (EDD)
The highest ductility grade of cold-rolled sheet under IS 513, intended for the most demanding drawing applications such as automotive body panels and appliance outer skins. Achieved through special aluminium-killed steelmaking and controlled annealing cycles.
See also: IS 513 · Deep Drawing · CR Sheet
View related standardFlatness Tolerance
The permissible deviation from a perfectly flat surface in a steel sheet or plate, expressed as the maximum height of a bow or wave per unit length. IS 1852 and related dimensional standards specify flatness tolerances for different product thicknesses and widths.
See also: IS 1852 · Coil Set · Levelling
View related standardGalvanizing
The application of a zinc coating to steel to provide corrosion protection through a sacrificial barrier. Hot-dip galvanizing (HDG) involves immersing the steel in molten zinc; electro-galvanizing applies zinc via electrodeposition. IS 277 governs galvanized plain sheets.
See also: Hot-Dip Galvanizing · IS 277 · Zinc Coating · Spangle
View related standardGauge
A traditional system for specifying the thickness of sheet metal, where a higher gauge number represents a thinner sheet (e.g., 18 gauge ≈ 1.25mm; 14 gauge ≈ 2.0mm). In modern steel supply, metric thickness in millimetres has largely replaced gauge designations, though the term remains in common use in India.
See also: Thickness Tolerance · IS 1852
Heat-Affected Zone (HAZ)
The region of base metal adjacent to a weld that has undergone microstructural changes due to the heat of welding without melting. The HAZ can have altered mechanical properties compared to the parent metal. Low carbon equivalent steels minimize adverse HAZ effects.
See also: Carbon Equivalent · Weldability · Welding
Hot-Dip Galvanizing (HDG)
A process in which cleaned steel is immersed in a bath of molten zinc (typically at 450–460°C), forming a metallurgically bonded zinc-iron alloy coating. HDG provides superior corrosion protection compared to electro-galvanizing and is specified for structural, solar, and outdoor applications. IS 2629 covers requirements for HDG of fabricated items.
See also: Galvanizing · IS 277 · Zinc Coating · Pre-Galvanized
View related standardHot Rolling (HR)
A metalworking process in which steel billets or slabs are rolled at temperatures above the recrystallization temperature (above ~900°C) to produce coils, sheets, plates, or structural sections. Hot rolling produces material with a characteristic mill scale surface. IS 1079 covers HR coils and sheets.
See also: IS 1079 · Mill Scale · Cold Rolling · Recrystallization
View related standardImpact Energy
The energy (in Joules) absorbed by a notched steel specimen during a Charpy or Izod impact test. Used as a measure of notch toughness, particularly at sub-zero temperatures. IS 2062 E-quality grades specify minimum impact energy at 0°C or lower.
See also: Charpy Impact Test · Toughness · IS 2062
View related standardKilled Steel
Steel that has been fully deoxidized by the addition of silicon, aluminium, or both, before casting. Killed steels have uniform composition, no gas porosity, and are required for all critical structural, pressure vessel, and impact-tested applications. Most modern steel is fully killed.
See also: Deoxidation · Aluminium Killed · Pressure Vessel
Lamellar Tearing
A form of cracking that can occur in welded steel structures when welding-induced stresses act through the thickness of a plate. It occurs along planes of weakness (inclusions) parallel to the rolling direction. Z-quality (through-thickness) steels with low sulphur content are specified to resist lamellar tearing.
See also: Through-Thickness Properties · Inclusions · Weldability
Levelling
A process in which steel strip or sheet is passed through a series of offset rolls to remove shape defects such as coil set, edge wave, centre buckle, and crossbow. Tension levelling and roller levelling are the two main methods used in service centre processing.
See also: Flatness · Coil Set · Cut to Length
Mill Scale
The blue-grey oxide layer (Fe₃O₄) that forms on the surface of steel during hot rolling. Mill scale is harder and more brittle than the base steel and must be removed before painting, galvanizing, or precision machining — typically by pickling in acid or shot blasting.
See also: Hot Rolling · Pickling · IS 1079
View related standardMill Test Certificate (MTC)
A quality assurance document issued by the steel manufacturer confirming that the material meets the specified standard. An MTC typically contains heat number, chemical composition, mechanical test results, and the relevant standard designation. Also called a Test Certificate or Mill Cert.
See also: Heat Number · Chemical Composition · IS 2062
View related standardMild Steel (MS)
Low-carbon steel with a carbon content typically below 0.25%. Mild steel is the most widely used engineering material, characterized by good weldability, machinability, and ductility. It conforms to structural standards such as IS 2062 and is available in all common product forms.
See also: IS 2062 · Low Carbon Steel · Carbon Equivalent
View related standardNormalising
A heat treatment process in which steel is heated to above the upper critical temperature (Ac₃) and cooled in still air. Normalising refines the grain structure, improves toughness, and eliminates the effects of hot working. IS 2062 allows supply in the normalized condition.
See also: Annealing · Grain Size · IS 2062
View related standardPassivation
The formation of a thin, stable oxide layer on the surface of steel (or zinc coating) that reduces further corrosion. Galvanized steel naturally passivates through the formation of zinc carbonate (white rust → stable patina). Chromate passivation is sometimes applied to galvanized products for additional protection.
See also: Galvanizing · Zinc Coating · Corrosion
Pickling
The chemical removal of mill scale and surface oxides from hot-rolled steel by immersing it in an acid solution (typically hydrochloric or sulphuric acid). Pickled and oiled (P&O) HR coils provide a clean, oxide-free surface suitable for forming, galvanizing, or cold rolling.
See also: Mill Scale · Hot Rolling · P&O Coil
Plate Mill Plate (PM Plate)
Heavy steel plates produced by rolling thick slabs in a plate mill rather than a continuous hot strip mill. Plate mill plates are available in greater thicknesses (typically 5mm to 150mm+) and wider widths than hot strip mill products. Used in pressure vessels, bridges, and heavy structures.
See also: IS 2062 · Pressure Vessel · ASTM A516 · Boiler Quality
View related standardPre-Galvanized
Steel coil or sheet that is galvanized in a continuous process before being formed into structural sections or profiles (as opposed to hot-dip galvanizing after fabrication). Pre-galvanized material is used for light-gauge sections such as purlins, strut channels, and cable trays. Coating may be damaged at cut edges and weld points.
See also: Hot-Dip Galvanizing · Galvanizing · Solar Structures
Quenching and Tempering (Q&T)
A two-stage heat treatment process: the steel is first quenched (rapidly cooled in water or oil) to form a hard martensite structure, then tempered (reheated to a lower temperature) to reduce brittleness while retaining high strength. Q&T steels such as S690QL offer very high yield strength (690 MPa+) for weight-critical applications.
See also: Martensite · Abrasion Resistant Steel · High Tensile
r-value (Plastic Strain Ratio)
A measure of the resistance of sheet steel to thinning during deep drawing. A higher r-value indicates better drawability. IS 513 EDD grade specifies minimum r-values. An average r-value (r̄) above 1.6 is desirable for deep drawn automotive parts.
See also: Deep Drawing · IS 513 · Anisotropy
View related standardRimmed Steel
Steel that has not been fully deoxidized, resulting in a characteristic 'rim' of pure iron at the surface and a core with higher carbon and impurities. Rimmed steels are largely obsolete in modern steelmaking, replaced by fully killed steels with more uniform properties.
See also: Killed Steel · Deoxidation · Continuous Casting
Rolling Direction
The longitudinal direction in which steel is rolled in the mill. Mechanical properties (especially toughness) are typically better in the rolling direction than in the transverse direction. Impact test specimens are usually oriented transverse to the rolling direction to represent the worst case.
See also: Anisotropy · Lamellar Tearing · Charpy Impact Test
Spangle
The characteristic crystalline snowflake-like pattern visible on the surface of hot-dip galvanized steel. Spangle size is controlled by adjusting the cooling rate and zinc bath chemistry. Regular spangle, minimized spangle, and zero spangle (skin-passed) finishes are available depending on application requirements.
See also: Hot-Dip Galvanizing · IS 277 · Zinc Coating
View related standardStructural Steel
Steel intended for use in load-bearing structural applications such as buildings, bridges, and industrial frames. Indian structural steel conforms to IS 2062, which specifies grades from E250 to E650 in various quality designations (A, B, BR, C). Section profiles (angles, channels, beams) are governed by IS 808.
See also: IS 2062 · IS 808 · Mild Steel · Yield Strength
View related standardSulphur (S) Content
Sulphur is a residual impurity in steel that forms manganese sulphide inclusions, which reduce ductility, toughness, and weldability. Modern structural and pressure vessel standards specify maximum sulphur content (typically ≤0.040% or lower for IS 2062 and IS 2041). Ultra-low sulphur grades are used for Z-quality steels.
See also: Lamellar Tearing · Chemical Composition · IS 2062
View related standardTemper Rolling
A light cold reduction (0.5–2%) applied to annealed cold-rolled steel to suppress the yield point phenomenon (Lüders bands), improve flatness, and adjust surface roughness. Temper-rolled CR sheets conform to IS 513 and are essential for quality paint-line applications.
See also: Cold Rolling · IS 513 · Lüders Bands · Annealing
View related standardTensile Strength (UTS)
The maximum stress that a material can withstand while being stretched before breaking, expressed in MPa (megapascals) or N/mm². Also called Ultimate Tensile Strength (UTS). Distinguished from yield strength, which is the stress at which the material first permanently deforms.
See also: Yield Strength · Elongation · IS 2062
View related standardThickness Tolerance
The permitted variation in thickness above or below the nominal specified thickness for a steel product. IS 1852 specifies rolling and cutting tolerances for hot-rolled steel. Tighter tolerances are available for cold-rolled products under IS 513.
See also: IS 1852 · IS 513 · Dimensional Tolerance
View related standardToughness
The ability of a material to absorb energy and deform plastically before fracturing. Toughness is measured by area under the stress-strain curve or by impact tests (Charpy/Izod). High toughness is critical for structures subjected to dynamic or impact loading, especially at low temperatures.
See also: Impact Energy · Charpy Impact Test · Ductility
Ultimate Tensile Strength (UTS)
See Tensile Strength. The maximum load divided by the original cross-sectional area, representing the peak engineering stress before fracture.
See also: Tensile Strength · Yield Strength · Elongation
Weldability
The relative ease with which a steel can be welded to produce a sound joint with the desired properties. Weldability decreases as carbon and alloy content increase. IS 2062 specifies maximum carbon equivalent values to ensure all grades are readily weldable without preheating in normal conditions.
See also: Carbon Equivalent · Heat-Affected Zone · IS 2062
View related standardWork Hardening
The increase in strength and hardness of a metal caused by plastic deformation at room temperature (cold working). Cold rolling exploits work hardening to increase yield strength of steel strip. Excessive work hardening reduces ductility and can cause cracking.
See also: Cold Rolling · Annealing · Yield Strength
Yield Strength
The stress at which a material begins to deform plastically (permanently). Below the yield point, the material deforms elastically and returns to its original shape when the load is removed. Yield strength is the primary design parameter for structural steel — the 'E' grade designations in IS 2062 (E250, E350, E450, E550) directly reflect the minimum yield strength in MPa.
See also: IS 2062 · Tensile Strength · Elastic Modulus · Proof Stress
View related standardZinc Coating Mass
The weight of zinc applied per unit area of galvanized steel, expressed in g/m² (both sides combined). IS 277 specifies coating mass designations from Z100 (100 g/m²) to Z450 (450 g/m²). Higher coating mass provides longer service life in corrosive environments. In European notation, Z275 is the most common structural designation.
See also: Galvanizing · IS 277 · Hot-Dip Galvanizing · Corrosion Protection
View related standard