METHOD OF HARDENING OF THE METALLIC CYLINDRICAL PIPE Russian patent published in 2007 - IPC C21D7/00 C21D9/08 

FIELD: mechanical engineering; methods of volumetric hardenings of the metallic products.

SUBSTANCE: the invention is pertaining to the field of volumetric hardenings of the metallic products by methods of training mechanical actions. The technical result of the invention is the increased cyclic service life. For reaching the technical result the cylindrical thin-walled pipe is subjected to the multiple training action at the continuous gyration of the main axes of the stressed state by the simultaneous application of the stretching axial force, the interior pressure and the twisting moment. At that the axial thrust and the interior pressure are applied in the form of the constant sign cycles in the opposite phase, and the torque - in compliance with the symmetrical cycle with the lag or with the phase advance by the quarter of the cycle concerning the phase of one of the extreme values of the axial thrust. At that the formed rotational training biaxial stretching is given the helical rising character with bringing the maximal main stress up to the level of the material tensile strength at the rotation frequency of the main axes of the stress state of no less than 5-10 Hz.

EFFECT: the invention ensures the increased cyclic service life of the of the metallic thin-wall cylindrical pipes.

6 dwg