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Tubes Glossary

A thermal treatment for the steel where a homogenous heating phase for a suitable period at temperatures betweena AC1 e AC3 (da 700° C a 900° C), is followed by controlled cooling. 


Inspection certificate in which the manufacturer declare that the products are in compliance with the order providing the test results based on nonspecific inspection.


Inspection certificate in which the manufacturer declares that the products are in compliance with the order. The document is validated by the manufacture’s authorized inspection representative, independent of the manufacturing department. This certificate provides the results of specific inspection, and it is produced on condition that the manufactures uses tracking procedures and provide the requested inspection documents.


Checks of the composition of a steel are carried out when the coil checks-in. An emission spectrometer is the usual instrument. Production standards include casting analysis and relative tolerances on product analysis.


Cold rolled sheet is produced by processing hot rolled strip through a cold rolling process followed by annealing and/or temper rolling. This process will produce steel with thinner gauges, closer dimensional tolerances and a wider range of uncoated surface finishes.


Eddy Current testing is a non-destructive testing method that utilizes an eddy current flow to detect a discontinuity in the weld area of the tubing.


Value resulting from a tensile test. Measurement of elongation after tensile breaking as a % of initial length.


Electric resistance weld tubing (ERW) is a method of tubing production where slit coils of steel are put through a gradual cold forming operation until the two edges of the steel are joined together in a tubular form. The heat for the continuous weld is generated at the seam by the resistance to the flow of electric current applied through an induction coil.


A destructive test performed that tests the weld suitability of a piece of tube when it is expanded over a cone at various degrees of expansion.


Refers to the thin layer of zinc finish that is applied to steel. Galvanized steel is used in applications where rust resistance is needed. It is identified by a crystalization pattern on the surface called "spangle". Galvanized tubes can be supplied in two ways: "pregalvanized" meaning that the steel is galvanized at the steel mill or as "hot-dipped galvanized" meaning that the tubes are produced from a hot rolled steel and then hot dipped after welding. 


A measure of the resistance of a metal to indentation, deformation or scratching. In practice it means the resistance of the surface to penetration by a harder body.


It is the union of the edges of the preformed belt made by a high frequency alternating current generator (HF), which uses a coil to induce a high intensity electric current that leads to incipient fusion the edges of the tape, which are pressed to make the welding.


It is a mill process which involves rolling the steel at a high temperature, which is above the steel’s recrystallisation temperature.As the steel cools in the open air, the surface oxidizes creating a blue grey scale finish.  Wall thickness tolerances within the coil will not be as uniform or as tight as steel produced as cold rolled.


ID refers to the inside diameter of the tubes.


The theoretical or stated single value given to the gauge or wall thickness of steel.


Testing methods of detecting defects without destroying or permanently changing the material being tested.


OD is an abbreviation for outside diameter.


The discrepancy (%) between the tube’s maximum and minimum measure.


Often referred to as HR P&O, pickled & oiled is a finish where hot rolled coil is descaled of oxide film or scale by either a chemical method, mechanical method, or a combination of both and then oiled to help prevent corrosion after descaling.  Pickled & oiled steel offers a cleaner surface than hot rolled steel, making it an attractive alternative to cold rolled steel in terms of cost if wall thickness tolerances are not as critical.


Measure of degree of surface roughness (in microns) of a steel, usually after working.


External/internal removal of welding bead. The standards can stipulate the allowed amount of internal beading.


Industrial plant for continuous longitudinal cutting/slitting of coil into strips.


Stainless steel is a steel alloy that contains more than 10 percent chromium. Stainless steel is known for not staining, corroding or rusting as easily as carbon steel. There are various different grades of stainless steel including stainless 304, 316, 409, 410 and 416. 


Steel is an alloy of iron and carbon and other elements. In steel, small amounts of carbon, other elements, and inclusions within the iron act as hardening agents that prevent the movement of dislocations that are common in the crystal lattices of iron atoms.The carbon in typical steel alloys may contribute up to 2.14% of its weight. Varying the amount of carbon and many other alloying elements, as well as controlling their chemical and physical makeup in the final steel (either as solute elements, or as precipitated phases), slows the movement of those dislocations that make pure iron ductile, and thus controls and enhances its qualities. These qualities include such things as the hardness, quenching behavior, need for annealing, tempering behavior, yield strength, and tensile strength of the resulting steel.


A constant section sample is subjected to axial tensile stress that increases gradually until total breakege of the sample. The test mainly provides the breaking load Rm (Mpa), the unitary yield load Rs or Reh (Mpa), elongation at rupture A (%).


The allowable difference in measurements from a desired value between what the customer requests or what an EN/ASTM specification calls out for.  Examples of common tubes tolerances include OD, ID, wall thickness, chemical and length tolerances. 


Degree of longitudinal deviation in the tube (in mm or %) compared to the ideal longitudinal axis. 


Tube obtained by a continuos forming of a flat rolled product (strip or sheet) and subsequent welding of the adjacent edges. Eurotubi performs a longitudinal welding.