TPT September 2007

T ube M ills: R olling & F orming M ethods

chromium-molybdenum-vanadium-niobium (eg P91, X10CrMoVNb91) – are more commonly required for power plants. The chemical industry requires tubes based on chromium-molybdenum steels (13CrMo45, 10CrMo910, 11CrMo910 and 25CrMo4), used in high pressures and temperatures above 450°C. These grades are also resistant to the hydrogen action, with the field of hydrogen application currently a major part of VVT’s R&D. VVT tubes are also used in the area of oil, gas and water exploitation and distribution. The production of casing pipes includes cutting of the threads on the ends of the tube and on the inner surface of the couplings for the thread protection. The ends are beveled on pipelines produced in accordance with API 5L for the trunk distribution frame of the oil and natural gas, as are the tubes produced in accordance with EN10208-2 (linepipes for combustible fluids). VVT-Vitkovice Valcovna Trub as – Czech Republic

› VVT’s pipe is manufactured on 2 rolling mills: big and small Mannesmann pilger mills

turn of the rollers. This way, the material is deeply and perfectly worked during the production process. It gives the final product very unique, incomparable mechanical and physical quality characteristics, suitable for use in highly demanding conditions. The products are mainly used for piping systems (steam pipelines) for the

nuclear and classic power plants or heat exchangers. These pipelines are resistant to the chemical impact of the circulating media. Power engineering often requires low alloyed creep-resistant steels based on molybdenum, or dispersive-strengthened steels using vanadium carbide particles (e.g. 16Mo3, 14MoV63). However, middle- alloyed high-temperature steels – based on

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S eptember /O ctober 2007