Ilta Inox Spa - Welded stainless steel tubes

> Glossary

Glossary

STAINLESS STEEL	An iron-based alloy containing chromium and carbon (with the addition of other elements such as nickel, molybdenum etc.). The chromium content is never less than 12%.
ELONGATION	Percentage of elongation of material with reference to a pre-established basic measurement.
ELONGATION AT BREAK	The permanent deformation between the references of the test piece measured after breaking as a percentage of the initial length of the section.
AUSTENITE	A solid solution of the carbon in the iron γ (having a cubic structure with centred faces).
BA (BRIGHT ANNEALING)	An annealing or solution heat treatment carried out in a controlled atmosphere composed of pure hydrogen or dissociated ammonia. This treatment allows the material to be obtained in softening conditions with a particularly shiny surface.
TENSILE STRENGTH (RM)	It is defined as the nominal stress applied in correspondence with the maximum load. It is given from the ratio between the maximum recorded load and the initial area of the resistant section of the sample.
DEVIATION FROM PROPORTIONALITY (RP0.2) OR ELASTIC LIMIT	Load corresponding to a non-proportional extension equal to a specified percentage (0.2%) of the basic length of the strain gauge (La).
YIELD POINT	It is the value of the nominal stress in correspondence with which, as elongation of the test piece increases, the load presents a single point following the change in the slope of the test curve.
INTERGRANULAR CORROSION	This occurs following the impoverishment of the Cr content in the grain edge area due to the formation of the Cr carbides in certain areas to values < 12% (lower limit which is why the steel loses its stainlessness). In these conditions cathodic areas are formed (inside the grain bodies) and anodic areas (chrome-impoverished areas adjacent to the grain edge).
CORROSION FATIGUE	Localised corrosion resulting from the combined action of cycling stresses. In the absence of stress the steel presents a clear fatigue limit (maximum cyclic stress for a certain time). In aggressive situations this limit ios significantly reduced.
STRESS CORROSION	Localised corrosion. In the presence of static or dynamic stress the corrosion process has characteristics that differ from those occurring in the absence of stress. It is a very worrying phenomenon as it develops at depth in limited areas of the material with particularly high penetration (~1-2 mm/h). It is especially dangerous because it occurs without any warning. It stops when stress ceases or it results in dispersal of the accumulated tension. In general, when the crack becomes visible the material is irremediably compromised by deep cracks (usually in transgranular “lightning bolt” form).
CHEMICAL PICKLING	Removal of surface oxide layer with chemical means.
NOMINAL DIAMETER	Term used to describe the measurement of the external diameter of the tube.
GRAIN SIZE	The size of the grain inside a solid metal.
HARDNESS	Surface resistance to a specified indentation force.
EDDY CURRENT	Method of detecting more or less hidden defects using the variation in induced currents applied to the material under test.
FERRITE	Solid solution of carbon in a iron (body-centred cubic structure).
PASSIVE FILM	Stainless steels possess a superficial protective self-repairing ability. The passive film reforms quickly if damaged, so long as there is enough oxygen.
STEEL GRADE	Stainless steels are classified according to the chenical composition in ferritic, austenitic and martensitic stainless steels.
INTERNAL WELD BEAD ROLLING	Mechanical reduction of the height of the internal cold weld bead.
OVALITY	The difference between the maximum and minimum diameters of a tube.
PASSIVATION	A natural characteristic of stainless steel is that it sometimes needs to undergo a nitric acid based chemical process . The chemical passivation process is different from chemical pickling.
CUT PERPENDICULARITY	Angle of deviation of end cut from 90%
MECHANICAL PROPERTIES	Measure of metal’s response to applied force or load. Mechanical properties usually described include resistance to breaking, elongation, yield and hardness.
TUBE STRAIGHTNESS	Longitudinal variation with reference to a linear metre.
TENSILE STRENGTH	Maximum resistance load of a material
ROUGHNESS	Grade of surface irregularity after working, measured in microns.
WELDING	Joining two touching edges of strip after circular shaping.
TIG and PLASMA WELDING	Joining the two edges of the preformed strip in an argon atmosphere using an electric arc. It is formed by the tungsten electrodes and the base material of the strip edges.
SLASER WELDING	Joining the edges of a preformed strip using a laser generator that fuses a minimal amount of the material.
H.F. WELDING	Joining the edges of preformed strip using a high frequency AC generator. It uses a coil to induce a high intensity electric current that bring the edges of the strip to near melting point. They are then pressed to achieve the weld.
FETTLING	An operation usually carried out by tools that remove the cut base on the tube end.
HEAT EXCHANGER	Device comprising a bundle of tubes within a casing to transfer temperatures between liquids, gases or vapours.
YIELD	Limit or point of no return of material elasticity.
BLANK SOLUBILISATION	Carried out in a thermal treatment furnace in a protected inert gas atmosphere. .
DESTRUCTIVE TEST	Test carried out by taking or destroying a part of the product to check for defects.
NON-DESTRUCTIVE TEST	A method of detecting more or less hidden defects using suitably accurate instruments without destroying the product.
THERMAL TREATMENT	Any high temperature thermal treatment (between 1040 °C and 1100 °C) of stainless steel to improve mechanical and physical properties.
HEAT ALTERED ZONE	The area affected by structural change between the weld area and base material.

Back top