METHOD FOR LASER SURFACE TREATMENT OF THREADED JOINTS OF LOW-ALLOYED STEELS Russian patent published in 2016 - IPC C21D1/09 C21D9/32 

FIELD: technological processes; machine building.

SUBSTANCE: invention relates to surface hardening of parts of machines and mechanisms by means of laser processing, and may be applied in machine building, in particular, for strengthening of threaded joints of pipes and coupling sleeves. Method involves treatment of threaded connection surfaces with laser beam, by forming heating spot of laser beam with diameter equal to pitch of thread, and moving beam along generatrix of threaded surface during its rotation around longitudinal axis. Along one turn of rotation of threaded surface, laser beam is moved by value equal to thread pitch due to mechanical connection with optical system of laser beam. Blackening of machined thread surface is performed before laser treatment, except zones adjacent to thread top and thread groove by at least 10 % of length of thread side surface. Formation of heating spot is performed upon thread side surface, and laser processing is carried out at angle, exceeding by 2-3° inclination angle of threaded surface relative to rotation axis of threaded connection.

EFFECT: higher mechanical strength of threaded connection due to elimination of layer with hardened structure that has high brittleness.

1 cl, 2 tbl