Method of manufacturing metal component and laser welding apparatus

1 . A method of manufacturing a metal component, the method comprising:

generating a laser beam;

splitting the laser beam into a first laser beam and a second laser beam;

reflecting the second laser beam;

irradiating the first laser beam through a first condensing optical system to an irradiation position on a surface of a workpiece made of metal, wherein the first condensing optical system condenses the first laser beam;

irradiating the second laser beam through a second condensing optical system to the irradiation position, wherein the second condensing optical system condenses the second laser beam;

adjusting a spot diameter ratio, wherein the spot diameter ratio is a ratio of a first spot diameter to a second spot diameter, wherein the first spot diameter is a diameter of the first laser beam on the irradiation position, wherein the second spot diameter is a diameter of the second laser beam on the irradiation position; and

moving the irradiation position to weld the workpiece,

wherein after the adjusting, the first spot diameter is 5.0 percent or more and 15.0 percent or less of the second spot diameter,

wherein after the adjusting, an energy density of the second laser beam on the irradiation position is 1.5 percent or less of an energy density of the first laser beam on the irradiation position,

wherein after the adjusting, a first focal position is located within a range of 0.0 mm or more and 2.0 mm or less from the surface of the workpiece in a direction from the first condensing optical system to the surface of the workpiece, wherein first focal position is a focal position of the first laser beam, and

wherein after the adjusting, a second focal position is located within a range of 10.0 mm or more and 20.0 mm or less from the surface of the workpiece in a direction from the surface of the workpiece to the first condensing optical system, wherein the second focal position is a focal position of the second laser beam.

2 . The method according to claim 1 , wherein

the second condensing optical system includes a plurality of lenses; and

the adjusting changes an interval of the lenses to adjust the spot diameter ratio.

3 . The method according to claim 1 , wherein

a center of the first laser beam on the irradiation position is disposed behind a center of the second laser beam on the irradiation position in a moving direction of the irradiation position.

4 . A laser welding apparatus comprising:

a laser oscillator generating a laser beam;

a beam splitter splitting the laser beam into a first laser beam and a second laser beam;

a mirror reflecting the second laser beam;

a first condensing optical system condensing the first laser beam, the first condensing optical system irradiating the first laser beam to an irradiation position on a surface of a workpiece made of metal;

a second condensing optical system condensing the second laser beam reflected by the mirror, the second condensing optical system irradiating the second laser beam to the irradiation position;

an adjuster adjusting a spot diameter ratio, wherein the spot diameter ratio is a ratio of a first spot diameter to a second spot diameter, wherein the first spot diameter is a diameter of the first laser beam on the irradiation position, wherein the second spot diameter is a diameter of the second laser beam on the irradiation position; and

a controller configured to control the adjuster such that

the first spot diameter is 5.0 percent or more and 15.0 percent or less of the second spot diameter,

an energy density of the second laser beam on the irradiation position is 1.5 percent or less of an energy density of the first laser beam on the irradiation position,

a first focal position is located within a range of 0.0 mm or more and 2.0 mm or less from the surface of the workpiece in a direction from the first condensing optical system to the surface of the workpiece, wherein first focal position is a focal position of the first laser beam, and

a second focal position is located within a range of 10.0 mm or more and 20.0 mm or less from the surface of the workpiece in a direction from the surface of the workpiece to the first condensing optical system, wherein the second focal position is a focal position of the second laser beam.

5 . The laser welding apparatus according to claim 4 , wherein

the second condensing optical system includes a plurality of lenses; and

the adjuster changes an interval of the lenses to adjust the spot diameter ratio.