Glossary
A comprehensive glossary for professionals and enthusiasts
A
Annealing
Annealing is a heat treatment process applied to metals and alloys, including stainless steel, to alter their physical and chemical properties.
ASTM
ASTM stands for the American Society for Testing and Materials, an international standards organisation that develops and publishes voluntary technical standards for materials, products, systems, and services.
Austenitic
Austenite is a face-centred cubic (FCC) phase of iron that is stable at high temperatures and can be retained at room temperature by the addition of alloying elements, such as nickel.
C
Carburising
Carburising is a case-hardening heat-treatment process where carbon atoms diffuse into the surface of stainless steel, creating a hard outer layer while retaining a tough, ductile core.
Cladding
Stainless steel cladding is the process of bonding a thin stainless steel layer to a base metal. This technique combines the structural strength of the base with the superior corrosion protection, chemical resistance, and surface durability of stainless steel.
Cold Drawn Stainless Steel
Cold-drawn stainless steel refers to stainless steel products that have been shaped or reduced in cross-section at room temperature by pulling the material through a die.
Cold Rolling
Cold rolling is a process in which stainless steel is passed through rollers at or near room temperature, below its recrystallisation point.
Cold Working
Cold working refers to the plastic deformation of stainless steel at temperatures below its recrystallisation point.
Corrosion Fatigue
Corrosion fatigue is a type of accelerated metal deterioration resulting from the combined effects of cyclic mechanical stress and a corrosive environment.
Corrosion Rate Calculation
Corrosion rate refers to the speed at which a material deteriorates due to chemical or electrochemical reactions with its environment.
Corrosion Resistance
Corrosion Resistance refers to the measure of how effectively a material, particularly stainless steel, resists degradation caused during chemical or environmental exposure.
Crevice Corrosion
Crevice corrosion is a localised form of corrosion that occurs within confined spaces, such as crevices, cracks or gaps.
D
Decarburisation
Decarburisation in stainless steel is the removal of carbon from the surface layers of steel when exposed to high temperatures in the presence of gases like oxygen or hydrogen.
Delta Ferrite Content
Delta ferrite is a body-centered cubic (BCC) ferritic phase of iron that is stable & forms at high temperatures in Fe-Cr alloys like stainless steel. It is a ferritic structure that can remain in the final metal after solidification, depending on alloy composition and cooling rate.
Descaling
Descaling refers to the process of removing the oxide layer, heat-tint or other surface contaminants from stainless steel surfaces. It removes the surface scale that forms during casting or high temperature operations such as annealing, hot rolling, forging or welding.
Duplex Stainless Steel
Duplex stainless steel is an alloy that uniquely combines both austenitic and ferritic microstructures in roughly equal proportions.
E
F
Fatigue Strength of Stainless Steel
Fatigue Strength refers to the ability of a material to withstand repeated or fluctuating stress without failure over a prolonged period. In simpler terms, it defines how resistant a material is to cracking or breaking under cyclic loading.
Ferritic
Ferrite refers to the body-centred cubic (BCC) form of iron that remains stable at room temperature.
Ferro Alloys
Ferro alloys are a mix of iron and other elements like chromium, manganese, or silicon. These are added to stainless steel during its production to improve strength, corrosion resistance, and shine.
Forging
Stainless steel forging is a specialised forming process in which stainless steel is shaped under high pressure to produce components with superior mechanical properties and structural integrity.
G
Grades of Stainless Steel
Stainless steel grades refer to the different types of alloys based on composition, microstructure, and properties. They determine how the material behaves in terms of its durability, corrosion resistance, and suitability for specific applications.
Grain Boundary Precipitation
Grain boundary precipitation refers to the phenomenon where carbides or intermetallic compounds form preferentially along grain boundaries in a material’s microstructure.
Grain Refinement
Grain refinement refers to the process of reducing the size of grains within a material's microstructure to improve its mechanical and physical properties.
H
Hardening
Stainless steel hardening refers to a group of heat treatment techniques used to increase the hardness and strength of stainless steels.
Hardness Test
Heat Affected Zone (HAZ)
The Heat Affected Zone (HAZ) in stainless steel refers to the portion of the material adjacent to the welding or heated region that undergoes structural and property changes due to the heat.
Hot Band Annealing
Hot band annealing is a heat treatment process applied to selected stainless steel grades, primarily for Ferritic grades and for other alloys immediately after hot rolling. It aims to provide a uniform microstructure, improve ductility, and relieve internal stresses formed during rolling.
Hot Isostatic Pressing
Hot Isostatic Pressing (HIP) is a post-processing technique used to reduce internal voids and improve the density of metal components. In simple terms, it’s the process of applying high isostatic pressure and elevated temperature simultaneously in a sealed pressure vessel, usually filled with an inert gas such as argon, or in a vacuum.
Hot Rolling
Hot rolling of stainless steel is a metal-forming process where stainless steel slabs or billets are heated above their recrystallisation temperature and passed through rolling mills to achieve the desired shape and thickness.
I
Induction Heating
Induction heating is a non-contact heating process that uses electromagnetic induction to generate heat within a conductive material such as stainless steel. Induction heating systems typically consist of a power supply, a customised induction coil, and an integrated cooling unit.
Ingots
Stainless steel ingots are solid blocks of stainless steel formed by casting molten metal into moulds.
ISO Standards for Stainless Steel
ISO Standards refer to the internationally recognised technical guidelines, that are set by the International Organisation for Standardisation (ISO) to ensure quality, safety, and reliability across materials and processes.
M
Magnetic Permeability in SS
Magnetic permeability describes how easily a material can become magnetised in the presence of a magnetic field. It defines how easily magnetic lines of force can pass through a substance when exposed to a magnetic field.
Martensite
Martensite is a hard, crystal structure in stainless steel formed through rapid cooling, resulting in a body-centred tetragonal (BCT) phase.
Metallography
Metallography is the study of the microstructure of metals using microscopic techniques.
Mill Test Certificate
A mill test certificate (MTC, or sometimes referred to as Mill Inspection Certificate in some cases)is an official quality assurance document issued by the manufacturer to verify that a metal product meets the required chemical and mechanical specifications.
N
Non-Destructive Testing
Non-Destructive Testing (NDT) refers to a group of testing techniques used to evaluate the integrity, quality, and properties of materials or components without causing damage. These testing methods help detect surface and subsurface defects, such as cracks, voids, corrosion and discontinuities, while preserving the part for continued use.
Notch Toughness
Notch Toughness refers to a material’s ability to absorb energy and resist fracture when a flaw or notch is present. It measures how stainless steel behaves under sudden impact or concentrated stress, particularly in low-temperature or high-stress conditions, where brittle failure is more likely.
P
Passivation in Stainless Steel
Passivation is a chemical treatment that enhances the natural corrosion resistance of stainless steel. It boosts the formation of a thin, stable chromium oxide film on the stainless steel surface that protects the steel from corrosion.
Passive Layer
The passivation layer is a very thin, protective film that forms on the surface of stainless steel when exposed to air or oxidising environments.
Pickling & Passivation
Pickling and passivation are chemical surface treatment processes used to restore and protect the natural corrosion resistance of stainless steel after fabrication.
Pickling Line (in Stainless Steel Plants)
A pickle line is a continuous processing system used in stainless steel manufacturing to remove surface scales, such as oxide layers and mill scale, heat tint formed during hot rolling or annealing.
Pipe Bending Radius
The pipe bending radius refers to the distance between the center of the bend’s curvature to the pipe’s centerline. It determines how tightly or smoothly the pipe is bent without causing excessive deformation, wrinkling, or cracking.
Precipitation Hardening Stainless Steel
Precipitation hardening stainless steel, also known as PH stainless steel, is a type of stainless steel that gains enhanced strength and hardness through a heat treatment process called precipitation hardening.
S
Seamless Stainless Steel Pipe
A seamless stainless steel pipe is a type of pipe manufactured without any welded joints, giving it a smooth and continuous structure throughout its length.
Sensitisation
Sensitisation in stainless steel refers to the formation of chromium carbides at grain boundaries when the alloy is exposed to elevated temperatures for extended periods, typically between 425°C and 870°C.
Sigma Phase Formation
Sigma phase (commonly denoted as σ-Phase) formation in stainless steel refers to the precipitation of a hard, brittle, chromium-iron intermetallic compound that develops in duplex, ferritic & austenitic stainless steels.
Solution Annealing
Solution annealing of stainless steel is a specialised heat-treatment process designed to restore and optimise the properties of stainless steel parts. In stainless steel fabrication, solution annealing involves heating the alloy to a high temperature and then rapidly cooling it.
Stainless Steel Angle
Stainless steel angles are structural components characterised by their L-shaped cross-sections, commonly used in construction and engineering applications for their strength, durability, and corrosion resistance.
Stainless Steel Bar Stock
Stainless steel bar stock refers to solid bars supplied as semi-finished materials for machining, fabrication, and manufacturing. It combines strength, corrosion resistance, and durability, making it ideal for structural, industrial, and precision applications.
Stainless Steel Beam
In structural engineering, stainless steel beams are horizontal elements designed to support vertical loads.
Stainless Steel Bright Bar
A stainless steel bright bar is a cold-drawn, precision-finished form of bar stock that offers a smooth, reflective surface, tight dimensional tolerances, and enhanced mechanical properties.
Stainless Steel Casting
Stainless steel casting refers to the process of producing complex stainless steel components by pouring molten stainless steel into moulds where it solidifies into the desired shape.
Stainless Steel Chemical Composition
The material composition of stainless steel defines its structure, properties and performance. Stainless steel is an iron-based alloy that primarily includes Fe (Iron), Cr (Chromium), Ni (Nickel), Mo (Molybdenum), C (Carbon) and sometimes N (Nitrogen) or other elements.
Stainless Steel Coils
A stainless steel coil is a long, slender strip of stainless steel wound into a roll after being processed at either elevated temperatures or room temperature.
Stainless Steel Fabrication Tolerance
A fabrication tolerance refers to the permissible limits of variation in a manufactured part’s dimensions with respect to the given specifications. When considering tolerance in fabrication, it refers to the allowable deviation of a finished stainless steel component from its nominal size while still being acceptable.
Stainless Steel Fasteners
Stainless steel fasteners are threaded or mechanical-joint fastening components made from stainless steel, used to securely join parts in assemblies.
Stainless Steel Flanges
Stainless steel flanges are mechanical components used to connect pipes, valves, pumps, and other equipment within a piping system.
Stainless Steel Heat Number
A heat number is a unique code assigned to a stainless steel melt during a single production process. It serves as an identification number that links the final product to its original melt, ensuring full traceability of chemical composition, mechanical properties, and test results from manufacturing to inspection.
Stainless Steel Pickling
Stainless steel pickling is a chemical or electrochemical treatment process employed to remove surface impurities such as oxide scales, heat tints, and other contaminants that form during high-temperature processing.
Stainless Steel Pipe Schedule
The stainless steel pipe schedule chart is a numerical designation that indicates wall thickness for a given nominal pipe size. The schedule number is simply a dimensionless number historically linked to wall thickness, not a formula for pressure.
Stainless Steel Reinforcement Bar (Rebar)
Stainless steel reinforcement bar (or Rebar), is a corrosion-resistant reinforcement material used to strengthen and support reinforced concrete structures.
Stainless Steel Scrap Grading
Stainless steel scrap grading refers to the process of classifying scrap based on its alloy composition, cleanliness, and suitability for melting & recycling.
Stainless Steel Sheet
Stainless steel sheets are premium flat-rolled products manufactured from high-quality alloys. These sheets are primarily composed of iron, chromium, and other elements like nickel and molybdenum.
Stainless Steel Slabs
Stainless steel slabs are flat products formed by solidifying molten stainless steel in rectangular shapes through continuous casting.
Stainless Steel Strip
A stainless steel strip is a flat-rolled product, typically less than 600 mm in width. These strips are renowned for their exceptional corrosion resistance, strength, and versatility, making them suitable for a diverse range of industrial applications.
Stainless Steel Surface Finish
A stainless steel surface finish defines the texture, polish, and appearance of stainless steel after manufacturing. It determines how the material looks, feels, and performs in service.
Stainless Steel Surface Roughness (Ra value)
Stainless steel surface roughness refers to the microscopic peaks and valleys that form on an alloy’s surface during manufacturing or finishing processes. These microscopic irregularities define the surface profile and directly influence the material’s appearance, friction behaviour, and corrosion resistance.
Stainless Steel Tempering
Stainless steel tempering is a heat treatment process that increases toughness and ductility while reducing the hardness of the alloy. This is done by reheating the alloy to a temperature below its critical transformation range after it has been hardened through quenching.
Stainless Steel Wire
Stainless steel wire refers to a high-strength, corrosion-resistant wire. It is made of various alloys, typically containing chromium and nickel.
Stress Corrosion Cracking (SCC)
Stress Corrosion Cracking (SCC) is a type of localised corrosion that occurs when a metal or alloy under tensile stress is exposed to a corrosive environment, resulting in sudden and often catastrophic cracking.
Stress Relieving in Stainless Steel
Stress relieving in stainless steel is a controlled heat treatment process used to reduce the internal residual stresses that develop during manufacturing processes such as welding, forming, or machining.
Super Duplex
Super Duplex stainless steel is a high-performance alloy that contains a balanced mix of austenite and ferrite phases, along with elevated levels of chromium, molybdenum, and nitrogen.
U
Ultimate Tensile Strength (UTS)
Ultimate Tensile Strength (UTS) is the maximum stress that a material can endure while being stretched or pulled before breaking.
Unified Numbering System
The Unified Numbering System (UNS) is a standardised method for identifying metals and alloys based on their chemical composition.
W
Welded Stainless Steel Pipes
A welded stainless steel pipe is made by forming stainless steel sheets or strips into a required hollow shape and joining the edges through continuous seam welding.
Work Hardening
Work hardening, also known as strain hardening, is the process by which stainless steel becomes stronger and harder when it is deformed when stress applied above its yield strength through processes such as bending, rolling, or drawing.
Wrought Stainless Steel
Wrought stainless steel refers to stainless steel that is shaped by mechanical working rather than casting. The stainless steel undergoes deformation processes such as rolling or forging, which refine its internal grain structure.