METHOD FOR MANUFACTURING COLD-WORKED WELDLESS PIPES FROM TITANIUM ALLOYS Russian patent published in 2022 - IPC C22F1/18 B21B3/00 B21B21/00 B21J5/00 

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy, namely, to the manufacture of weldless cold-worked pipes from titanium alloys, and can be used for manufacturing heavy-duty articles. Method for manufacturing cold-worked weldless pipes from titanium alloys includes machining hot-worked cylindrical workpieces, pressing, levelling, and machining the resulting hot-pressed pipes, followed by multi-pass cold rolling while performing intermediate heat treatments in vacuum, depending on the alloy, and finishing heat treatment of pipes of the finished size in vacuum. The PT-1M or PT-7M alloy is used as titanium alloys for the pipes; prior to heating for pressing, a protective coating is applied to the surface of the workpieces, constituting a slip coat consisting of a mixture of powdered EVT-24 enamel, ground bentonite clay, and liquid glass. Pressing is then performed at a temperature T_H determined by the dependence: T_H = T_PP – k·ε·υ_PR, wherein T_PP is the polymorphic transition temperature, °C; k is an empirical coefficient accounting for the influence of deformation heat-up, °C·s/mm; for the PT-1M alloy, the empirical coefficient k is from 0.035 to 0.12, and for the PT-7M alloy, the empirical coefficient k is from 0.02 to less than 0.15, ε is the logarithmic degree of deformation; υ_PR is the rate of movement of the deforming tool during pressing, mm/s. Cold rolling is performed with a 40 to 44% degree of deformation, using liquid process lubricants; and intermediate heat treatments are performed in vacuum at a temperature of 670 to 690°C for 120 minutes for the PT-1M alloy or at 730 to 790°C for 120 minutes for the PT-7M alloy. The finishing heat treatment of pipes of the finished size is performed in vacuum at a temperature of 670 to 690°C for 120 minutes for the PT-1M alloy or at 730 to 790°C for 120 minutes for the PT-7M alloy.

EFFECT: required mechanical properties of the pipes are obtained, and yield coefficient is increased due to the absence of defects on the surface of cold-worked pipes.

2 cl, 5 dwg