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Glossary

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  14. R
  15. S
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  17. U
  18. W
  19. Y
  20. Z
  1. Austenite

    Type of crystalline structure of iron and steel that is generally only stable at a high temperature. It can be transformed into Ferrite or Martensite. The addition of appropriate elements, Nickel for example, may make it stable even at ambient temperature.

  2. Austenitic steel

    Steel made up of Chrome-Nickel alloys, with Chrome content between 17 and 26% and Nickel content between 7 and 22%.

  3. Brushed pipe

    Pipes brushed mechanically both in-line and off-line. Round pipes with HF welding are also supplied coarse (W0).

  4. Carbon equivalent value (C.E.V.)

    Weldability index of steel. This value, together with the thickness and the increase in the strength of the product, affects the formation of cracks in the welded zone with consequent fragility of the H.A.Z. (Heat Affected zone)

    C.E.V. = C +
    Mn
    +
    Cr + Mo + V
    +
    Ni + Cu
    6
    5
    15
  5. CE Marking

    Marking that proves that the manufacturer has implemented an in-house control schedule and has carried out the initial standard tests. Consequently the products comply with standard EN 10219 and therefore with Directive 89/106/EEC. Authorisation to apply such marking is indicated in the declaration of conformity issued under the sole responsibility of the manufacturer. This marking is applied on sales documents or on the test document.

  6. Checkering

    Surface finishing of the steel obtained through rolling using rollers with relief patterns. It appears with diamond checkers distributed over the full surface (UNI 3151).

  7. Coated steel

    Alloy/Non-alloy steel coated by hot dipping in zinc baths or baths of alloys containing zinc and/or aluminium, for example DX51D.

  8. Coil zinc treatment

    Galvanisation process consisting in a treatment in which the metal sheet is placed in a melted zinc bath at 700° within a ceramic tank. The coating thickness is indicated by a value expressed in g/m2, and is included in the steel’s designation, i.e. +Z275, meaning that the steel has an average coating thickness of 275 g/m2 ( EN 10327) .

  9. Conventional limit of elasticity (RP0,2)

    Value resulting from a tensile test (EN 10002). It is the stress corresponding to the non-proportional elongation equal to a fixed percentage (0.2%) of the initial gauge length.

  10. Elongation

    Increase in the initial length between the references of a sample during the tensile test.

  11. Expansion test

    Destructive method used to establish the suitability of a metal circular pipe to be subjected to plastic expansion deformation by means of a spindle (ISO 8493).

  12. Ferrite

    Structure of steel featuring a small amount of Carbon.   

  13. Ferritic steel

    Steel featuring mainly Chrome and a low Nickel content

  14. Finish (Degree)

    Condition of the surface of the pipe that can be obtained through surface treatments. The degrees are established by standards (EN 10296-2 and EN 10217-7) and are identified by the symbol W followed by numbers and/or letters. It also bears in mind the initial material.

  15. Flattening test

    A destructive method used to establish the capacity of circular pipes to withstand plastic deformation through flattening. A section of pipe is pressed perpendicularly between two press plates up to a preset height. The weld may be positioned at 90° to assess its external holding or at 0° to assess its internal holding (ISO 8492).

  16. Galvanisation suitability classes

    Guide to the classification of the aptitude of steel to be galvanised, based on the silicon and phosphor content in the casting analysis. UNI EN 10025-2 defines three classes.

  17. Heat Affected Zone (H.A.Z.)

    It is the portion of pipe heated right by the weld. Its hardness decreases in the centre of the welding axis on the edges where it is similar to base steel.

  18. High Frequency Welding (HF)

    Welding method with induced heat, using an induction coil that generates a magnetic field localised on the two edges by an internal impedance, which melt after being brought together and pervaded by rollers. It allows high speed welding, up to 100 metres/minute.

  19. Hot galvanisation

    Industrial process in which a pipe, with appropriately prepared surface, is dipped in a pure zinc bath. The coating is obtained by a layer of zinc (EN 1461/EN 10240), see also the item entitled Galvanisation classes.

  20. Impact strength test (KV)

    A test that provides the value of the energy (Joule) absorbed during impact by a standard sized notched sample. The test provides a strength or fragility parameter of a material at a certain temperature (ambient, 0°C, -20°C). The reference standard is EN 10045-1.

  21. Induced current test (Eddy Current)

    A Non-Destructive Test based on the use of induced currents. The defects are highlighted as alterations in the induced electromagnetic field. The reference standard is EN 10246.

  22. Intergranular corrosion

    Corrosion localised in the boundaries of the crystallites of the steel which, due to thermal reasons, is sensitized and therefore susceptible to the aggression of certain corrosive agents because the percentage of chrome is not sufficient to create the protective oxide film.

  23. Laser welding

    Welding method using a laser beam that melts the edges previously brought together by pressure rollers.

  24. Low carbon steel

    It comprises hot rolled steel suitable for cold forming, for example DD11 (EN 10111) and cold rolled steel, for example DC01 (EN 10130).

  25. Martensite

    One of the structural forms of steel obtained through quenching (hardening) austenite. It is a phase that features a high degree of hardness and mechanical strength, but is also fragile.

  26. Mirror-polished pipe

    Pipes polished mechanically to increase their brightness (WP).

  27. Non-alloy steel

    Steel defined as such due to its low alloy elements that do not exceed, in any case, the limits indicated in standard EN 10020 (also indicated in the catalogue of Padana Tubi)

  28. Non-Destructive Test (N.D.T.)

    Test method used to detect defects in the product, such as the welding for example, performed with electromagnetic or ultrasound equipment.

  29. Passivation

    Phenomenon consisting in the spontaneous formation, through mere contact with atmospheric air, of a very fine layer of oxide that protects the heart of the material against corrosion. In stainless steel, the phenomenon is due to a minimum content of 12% of chrome that does indeed form the protective oxide or due to titanium, that develops the oxide film without the presence of any alloy in particular.

  30. Pickling

    Treatment used to eliminate layers of oxides on the surfaces that form during hot treatment.

  31. Pipe straightness

    Degree of longitudinal deviation of the pipe (in mm or %) compared to the ideal longitudinal axis. This deviation can be corrected through straightening.

  32. Polished pipe

    Pipes polished with sheets of variable grain size depending on the requirements of the customer (WP). The final finish obviously differs based on the grain used.

  33. Relief finish

    Surface finishing of steel obtained through rolling using rollers with relief patterns. It appears with a relief finish distributed over the full surface (UNI 4630).

  34. Scarfing

    External and/or internal removal of the welding beads. Standards may impose the entity of the admitted residual internal bead.

  35. Sendzimir

    Galvanisation process consisting in a treatment in which the metal sheet is placed in a melted zinc bath at 700° within a ceramic tank. The coating thickness is indicated by a value expressed in g/m2, and is included in the steel’s designation, i.e. +Z275, meaning that the steel has an average coating thickness of 275 g/m2 ( EN 10327) .

  36. Stainless steel

    Steel with at least 10.5% of Chrome and 1.2% of Carbon at the most.

  37. Steel

    Iron-carbon alloy with carbon content no higher than 2 percent (EN 10020 Definition and classification of types of steel). The qualities of steel are defined with reference to the chemical composition resulting from cast analyses.

  38. Steel designation

    Many systems are used for stainless steel, amongst which the most popular are AISI (American organisation) and the numerical system defined by EN 10088-1.

  39. Steel designation

    For non-alloy structural steel, i.e. S355JR, the designation comprises the following
    - letter S, that designates steel for structural use;
    - indication of the minimum yield point;
    - capital letters JR for the qualities with characteristics of impact strength specified at different temperatures;
    The addition of the letter H at the end indicates that the section is hollow.
     

  40. Strain hardening

    Increase in the mechanical characteristics of a material through cold deformation. The initial conditions of the characteristics can be restored through thermal treatment (i.e. annealing).

  41. Tensile test

    A method in which a sample with constant section is pulled axially with a force that increases gradually until the sample breaks completely. This test mainly provides: the tensile strength Rm (N/mm2), the upper yield point Reh (N/mm2), the ultimate elongation A (%). This test is carried out pursuant to EN 10002.

  42. Test Document

    A document that declares product conformity to the sales specifications. According to standard EN 10204, there are four types: 2.1 (conformity to order), 2.2 (conformity to order with non-specific test results), 3.1 (conformity to order with specific test results) and 3.2 (conformity to order with specific test results validated by a representative of the customer). The contents of the certificate are regulated by standard EN 10168.

  43. TIG Welding

    Welding method in which an electric arc is formed between a nonconsumable electrode and the surface to be welded. Inert gas prevents the electrode from burning. The speeds obtainable are however low.

  44. Ultimate strength (Rm)

    Value resulting from a tensile test (EN 10002). It represents the maximum admitted stress the sample can withstand during testing. It is the result of the ratio between the maximum stress registered during the test and the initial area of the resistant section of the sample (It is expressed in Newton/mm2).

  45. Upper yield point (Reh)

    Value resulting from a tensile test (EN 10002). It is the stress value in the point on the test graph where the sample starts to yield (it is expressed in Newton/mm2).

  46. Welding seam

    Excess material during welding due to the pressure applied on both sides of the coil.

  47. Yielding

    It is the point in which the material, subjected to stress, passes from an elastic state to a plastic state; it appears with a plastic deformation without any increase in the stress.

Glossary