Double-beam laser heat treatment method with adjustable light spot size

The invention provides a light spot size adjustable double-beam laser heat treatment method which comprises the following steps: (1) determining the length and width of a homogenized light spot according to parameters of a gear to be processed; (2) controlling the two homogenizing light spots to be focused on the two sides of the tooth top of a certain tooth to be machined; (3) the two tooth surfaces are subjected to synchronous laser quenching scanning, and the surface heating temperature of a double-beam irradiation area is controlled to be kept in an austenite phase change area; during laser quenching scanning, lifting of a double-beam laser heat treatment machining head is controlled through a mechanical arm, a beam combiner is controlled to swing through a driving motor, and therefore it is guaranteed that in the double-beam tooth surface scanning process, homogenized light spots on the two sides are always focused on the tooth surface; and (4) the operation steps of (2)-(3) are repeated until laser quen