MANUFACTURING METHOD OF PIPES FOR PROCESS NEEDS OF OIL WELLS Russian patent published in 2012 - IPC C21D9/08 C21D1/40 B21J5/04 

FIELD: metallurgy.

SUBSTANCE: manufacturing method of tubing involves heating of ends of measuring pipes, simultaneous fixation of pipe at two points, upsetting of each pipe end on horizontal forging machine, cooling in the air from forging temperature to room temperature, heating for drawing up to temperature of 320-360°C by passing electric current throughout the pipe volume with exposure during 1-3 minutes; at that, together with upsetting of pipe ends there formed are four flattened surfaces for key with length of 30-40 mm from the pipe end at the distance of 30-35 mm per pass by means of stamp of the specified design, and normalisation of upset pipe ends and transient zone with length of up to 600 mm is performed prior to drawing at the temperature of 810-860°C. Hold-down pressure and contact area of special key in places of flattened surfaces with the pipe body is decreased, there are no surface defects, marks (scores), and therefore the pipe wear is reduced.

EFFECT: improving strength properties of pipe at pipe cutting points on upset ends and enlarging its service life due to reducing the pipe wear at lifting and lowering operations.

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