Glossary
A
Metallurgical symbol representing aluminium.
Heat treatment comprising heating and appropriate temperature-holding, followed by cooling performed in conditions such that after return to ambient temperature, the structural state of the metal is close to the stable equilibrium state.
A treatment process that deposits a thick coat of Al So 3, thereby improving resistance to corrosion.
From a liquid phase, the steel is cast in a tower and cooled by a jet of neutral gas, which breaks the jet of cast steel into fine particles (powder).
Alloy steels having an austenitic structure at ambient temperature.
Operation during which the steel is heated to a temperature greater than the limit of stability of the ferrite, such that the latter is transformed into austenite, carbon and alloying elements being dissolved.
Steels whose structure includes austenite and ferrite.
B
Metallurgical symbol representing boron.
Metallurgical symbol representing berrylium.
Steels employed for the manufacturing of bearings.
Metallurgical symbol representing bismuth.
Whereby no heat treatment is applied after cold deformation. For this reason, the tubes have only limited suitability for shaping; no guarantees can be given regarding the limits of the latter.
After the final cold-deformation pass, the tube undergoes stress-relieving at relatively low temperature; the purpose of this phase is to relieve some or all of the stress. Using an appropriate shaping method, the tube can then be distorted cold within certain limits (bending, flaring etc.).
Cutting (with shears) of disks of metal prepared for preforming or pressing.
A thermochemical process applied to an iron alloy in order to produce boron-enrichment on the metal surface. Performed at high temperature, the process results in a layer of greater hardness.
The very precise adjusting of the inside diameter of a tube (or hole).
C
Metallurgical symbol representing carbon.
A treatment (in the liquid phase) involving the introduction of calcium silicon in order to alter the morphology of sulfides (nodular tendency).
Enriching the surface of a material by diffusion of carbon: on steels, the process results in greater hardness levels after final processing.
Non-alloy or alloy steels for heat treatment, with a carbon content less than or equal to 0.2%. They are intended to be case-hardened (carbon surface-enrichment) before hardening and tempering.
A drilled hole limited at both sides with a shaping bit, allowing machining between points.
An oblique surface obtained with a machine tool, involving cutting off the sharp edges of a material.
A process to transform the smooth surface of a metal part by applying acid to create a motif.
The separation of thin plates of steel at the surface of a working tool.
A machining operation designed to ensure passage or facilitate movement of a part.
Metallurgical symbol representing cobalt.
Whereby no heat treatment is applied after cold deformation. For this reason, the tubes have only limited suitability for shaping; no guarantees can be given regarding the limits of the latter.
An operation whereby an object (e.g. mint pattern) is pushed deep into a material using a tool.
Plastic deformation of a metal at a temperature below its re-crystallization temperature. The process results in increased strength characteristics (elastic limit & hardness), and reduced ductility (elongation, necking).
A tamping operation designed to settle powders and increase their density.
The level of compressive stress that can be applied to a steel before the material suddenly breaks.
Operation during machining to give the part the exact contour specified on the drawing.
Machining by breaking down a shape from solid material.
Metallurgical symbol representing chrome.
Steels designed to withstand a certain mode of damage (elongation, even up to breaking point) for permanent strain under heat.
Metallurgical symbol representing copper.
D
The action of compressing a metal part (either hot or cold), to induce a given shape.
A machining process consisting in drilling a hole or a cavity in a material.
A hollow or contoured mould used for reproducing a contour (extruded shape) in a recipient steel bloom.
Hot-forging of metal products using a die.
A process for transforming a bar into a greater length with a lower cross-section, by passing it cold through an extrusion die (cone).
Making holes with a drill bit ("drilled hole") or a punch ("punched hole").
Property of a material to distort before breaking. Can be gauged from the material's behaviour during necking down (i.e. reduction of the cross-section immediately prior to breakage).
Steels whose structure includes austenite and ferrite.
E
A process for machining metal parts by a very rapid succession of electrical discharges in an insulating liquid ("dielectric").
A steel electrode is immersed in a liquid slag and melts, due to the electrical resistance of the slag (the applied electrical energy is transformed into heat and causes melting of the electrode). As it passes through the slag, the molten steel from the electrode undergoes a refining phase. Any impurities and oxides are retained by the slag.
Copper obtained by electrolysis (i.e. by chemical breakdown of a substance in fusion or in solution, by passage of an electric current).
A steel forming process consisting in pushing the steel through an extrusion die (cone).
F
A machining operation to flatten a surface.
Metallurgical symbol representing iron.
Steels having a ferritic state that is stable at all temperatures.
A cooling condition such that the dip penetration is greater than or equal to the distance between the core and the surface of the part.
G
Occurs when two materials having different electrochemical properties come into contact with an electrolyte. The material having the lower electrochemical potential will corrode.
Case hardening in a gas stream.
A type of finishing operation on a machined part, employing a grinding wheel.
H
Metallurgical symbol representing hydrogen.
Electrolytic deposition ("electroplating") of chrome on a non-alloy or alloy steel, hardened or otherwise. The coating obtained is generally very hard (900HV).
Characterises a material's resistance to strain. The values obtained from hardness-testing enable the establishing of certain classifications.
These steels offer excellent resistance to oxidation and corrosion from high-temperature gases.
Steels in which at least one of the alloying elements is present by more than 5%.
A steel forming process performed either hot or cold, involving plastic deformation.
I
The required level of energy to be absorbed by the steel before sudden breakage. The characteristic is tested in a "keyhole specimen test" or "un-notched specimen test".
An evaluation performed by comparing standard images or counting the number and hardness of non-metal inclusions in a steel.
Corrosion appearing at the joints between the grains of the metal.
Whereby the physical characteristics are identical in all directions (length, shortest width, longest width).
J
K
The quotient of the initial section (So) by the final section of a product transformed by heat. The forging ratio or grade = So/S.
L
M
Represented by grades with 13% of Cr (e.g. X 20 Cr 13), and a sufficient carbon content (C > 0.08%). Their behaviour is comparable to that of high heat-treat steels.
Metallurgical symbol representing magnesium.
A quality of surface appearance obtained by polishing, equivalent to a glazed surface.
Metallurgical symbol representing manganese.
Metallurgical symbol representing molybdenum.
N
Metallurgical symbol representing azote.
Metallurgical symbol representing niobium.
Whereby tubes are heated to a temperature higher than transformation temperature AC3 (inversion point), then cooled. Both heat-treatment steps are performed in a controlled atmosphere.
Metallurgical symbol representing nickel.
A thermochemical processing operation applied on metal materials: temperature-holding (generally below AC1 for steels) is performed in a suitable medium to obtain surface enrichment in nitrogen (increases the case hardness, while improving the fatigue and friction properties).
Chrome-molybdenum or chrome-aluminium-molybdenum steels generally treated by hardening and tempering and intended for nitriding treatment (the latter leading to surface hardening through general diffusion of nitrogen).
A type of heat treatment consisting of austempering, followed by still-air cooling to obtain an homogeneous structure.
The appropriate rolling conditions (temperature, pressure, speed etc.) on the production route to give a product having a final structure practically identical to that of a product which has followed the normalizing route.
P
Metallurgical symbol representing phosphorus.
Metallurgical symbol representing lead.
A machining operation to remove the crust from a product (e.g. round bar).
The action of hammering or inducing plastic deformation in a cold-workable material.
A point-attack phenomenon occurring under the effect of halogen ions - particularly chlorides - and resulting in perforation of the alloy. The use of grades containing molybdenum can prevent the phenomenon.
Removing bumps or bends from a distorted, curved or bent sheet.
Cutting of steel parts using high-temperature ionised gas.
A rubbing action to give a unified and shiny appearance to the surface of a metal.
A case-hardening process in which the parts are heated in the presence of a solid case-hardening material obtained from a powder.
Steels produced from a powdered alloy; products are created by the application of forming processes (bilateral compression or hot isostatic compression at a temperature below the fusion point).
Hardening is obtained by precipitation of a compound from a supersaturated solid solution.
A piece of steel engraved with relief to form medals, for example.
Q
Operation consisting in cooling a metal alloy more quickly than in still air.
S
Metallurgical symbol representing soufre.
A case-hardening process whereby the parts are heated in a molten salt bath of suitable composition to achieve the required surface enrichment.
The machining of bowls or cavities.
Metallurgical symbol representing silicium.
Operation involving three processes occurring simultaneously:inter-welding of particles of powders of different compositions, recrystallization, removal of porosity.
A mechanical component subject to translational motion, for feeding or distributing a fluid or a material.
An operation to split or saw a sheet or a block of steel into lengths.
Creating clearance to facilitate movement of a part or tool.
Metallurgical symbol representing tin.
Annealing performed a few dozen degrees below AC1, with consecutive slow cooling.
A heat treatment for austenitic steels, involving heating to high temperature followed by cooling at a sufficiently fast rate to maintain an homogeneous austenitic structure after return to ambient temperature.
Heat treatment involving the dissolution and solution-holding of certain components of the alloy (phases, precipitates).
A quality of surface appearance obtained by polishing, equivalent to that of a mirror.
An annealing process that changes the geometric shape of cemented carbides (such as modifying cementite platelets into stable spherical shapes).
Steels employed for manufacturing springs.
An operation to flatten, straighten or improve a surface.
The conjunction of stresses (internal or external) and exposure to aggressive environments (essentially chloride-based) can result in cracks above 50°C.
Heat treatment to reduce the degree of internal strain without substantially modifying the structure of the material (the temperature is at most equal to the hardening temperatures).
The make-up and configuration of elements within a material.
A hardening process involving quenching after heating of the material's surface (by high-frequency flame induction).
T
A long straight notch made by machining into a steel part.
Metallurgical symbol representing tantalum.
Machining at a angle
An operation that consists in threading the inside surface of a hole, using a special tool ("tap").
Heat treatment applied to a product in the quench-hardened or solution-hardened state, to achieve a desired level of operating characteristics. It is accompanied by softening (after quenching) or by hardening (after dissolution).
Defined as the load required per unit volume to cause a steel to break.
Development of the martensitic transformation into the thickness of the part, to the very centre of the material.
Metallurgical symbol representing titanium.
V
Metallurgical symbol representing vanadium.
In a vacuum electric arc furnace, a self-consuming electrode is melted through the action of the electric arc. Due to vacuum effect, the elements evaporate with a high vapour pressure. Any non-metal inclusions drift into the peripheral zone of the fused ingot, and can be removed by turning.
An operation during production of steel, employing a vacuum to remove oxygen, hydrogen and nitrogen.
A physical coating applied in the vapour phase.
W
Metallurgical symbol representing tungsten.
COR-TEN steels (for "corrosion-tenacity") offer improved resistance to atmospheric corrosion. The product acquires natural oxidation of its surface, leading to a patinated appearance.
Adding material (by welding) into the worn parts of a item of tooling.
X
Y
Expresses the relationship between tension (strain) and mild elongation in the elastic range (tensile test E = strain / elongation in the elastic range).