STRAIGHT SEAM ELECTRIC WELDED PIPES THERMAL TREATMENT METHOD Russian patent published in 1995 - IPC

FIELD: tube production. SUBSTANCE: they exercise local heating up to exceeding Ac₃ temperature of welding connection processing zone, that is equal to four time thickness of pipe wall, and also exercise heating of pipe sections by width of ± 100 dgr away from seam axis to temperature of 650 - 700 C and following cooling by air. In the case, Zone of heating up to temperature, that exceeds Ac₃, is increased beyond limits of production zone by additional value, that is proportional to decrease of pipe thickness. Between operations of welded connection heating and its cooling by air they introduce additional operation - cooling in steam medium down to temperature of no more than 650 C on outer surface. EFFECT: removal of nonuniform strength, that appears between pipe metal and metal of tempering zone during heating, and increase of pipe quality. 1 tbl