Steel Tubes - Classification and Terminology
Mentioned terms of steel tubes are in standard EN 10079 or others (ISO 6929).
- Tube classification goes out several aspects: mode of production, cross section shape, tube ends treatment, sphere of tube usage.
- According to EN 10079 tubes rank among so-called long products. It is a product having permanent circular or another hollow section along, with both ends free and with relatively long length.
- By mode of production are tubes divided to two big groups - seamless and welded. Each of this groups can be sectionalized by method of tube production - hot or cold production. A part of tube products are also so-called hollow sections. Here belong seamless or welded tubes of circular, square or rectangular section, used as part of building steel constructions or machine units.
- Hollow bars are seamless tubes of circular section designed for production of machine parts by machining. Different from the two first tube groups hollow bars have qualitative and dimensional parameters, which fit to requirements of workability, heat treatment or surface quality.
Tubes in this guide book are ordered by application considering mode of production, similar to ordering in new steel tube EN.
Technical Standards of Steel Tubes
Technical characteristics of steel tubes are detailed in the appropriate technical standards.
Pipe parameters could be divided into three main groups:
- dimensions and their tolerances (depending upon the tube manufacturing method)
- steel grade and steel conditions
- technical delivery conditions
Individual national bureaus of standards use different procedures for data standardization of steel pipes. In real life three options are used:
- each main group of parameters is contained in a single standard. The standards are interconnected using references to the related ones. Dimensional standard contains dimensional tables and their tolerances; steel standard contains its chemical composition and mechanical properties for various methods of pipe manufacturing and steel tempers. The third standard of the technical delivery conditions (TDC) sets out all remaining requirements for pipes – testing, acceptance, certificates, packaging, marking, etc. At the same time it contains references to other standards where these activities are described (e.g. STN, CSN).
- the second option is when steel and its characteristics are included into the TDC standard, and this one contains dimensional tolerances. Two standards are used to describe a pipe - dimensional standard that contains dimensional table and the TDC standard (e.g. DIN).
- the third option - pipe parameters are in a single standard, which also contains the dimensional table, or extraction from the general table of dimensions constituting which is the content of the general dimensional standard (e.g. NFA, EN).
In real life there are cases, where both the seller and the buyer make bilateral TDC contracts, or they deliver pipes in accordance with the buyer’s specifications, which can also include the references to national standards. Normally, this is the case, where the demands for pipes are higher then those set-up in the national standards.
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