Hybrid laser arc welding process and apparatus

1. A method of welding at least two workpieces together by metallurgically joining faying surfaces of the workpieces, the method comprising:

placing the workpieces together so that the faying surfaces thereof face each other and a joint region is defined, the joint region comprising an intersurface portion defined by and between the faying surfaces;

welding the workpieces together by performing a multistage welding process along the joint region, the multistage welding process comprising conducting a laser beam welding process on the joint region and then conducting a hybrid laser arc welding process on the joint region, the laser beam welding process comprising projecting a first laser beam onto the joint region and causing a projection of the first laser beam on the joint region to travel along the joint region, penetrate the intersurface portion of the joint region, and form a preliminary weldment in the joint region, the hybrid laser arc welding process being conducted along the joint region and remelting the preliminary weldment, the hybrid laser arc welding process comprising simultaneously causing an electric arc and a second laser beam to travel along the joint region while melting a filler material with the electric arc, wherein projections of the second laser beam and the electric arc on the joint region overlap to simultaneously form a weld pool in the preliminary weldment; and then

cooling the workpieces to yield a welded assembly comprising a weld joint within the joint region and through the intersurface portion thereof.

2. The method according to claim 1 , wherein the first and second laser beams are created by splitting a primary laser beam.

3. The method according to claim 2 , wherein the primary laser beam is at a power level of at least four kilowatts.

4. The method according to claim 1 , wherein the first laser beam is at a power level greater than the second laser beam.

5. The method according to claim 1 , wherein the second laser beam is at a power level greater than the first laser beam.

6. The method according to claim 1 , wherein the first and second laser beams are separated along the joint region by a distance of less than 2.5 centimeters.

7. The method according to claim 1 , wherein the first and second laser beams are separated along the joint region by a distance of about 0.5 to about 2 centimeters.

8. The method according to claim 1 , wherein the first and second laser beams are parallel to each other.

9. The method according to claim 1 , wherein the first and second laser beams are perpendicular to a surface portion of the joint region defined by surfaces of the workpieces adjoining the faying surfaces that remain exposed after the workpieces are placed together.

10. The method according to claim 1 , wherein the projection of the first laser beam on the joint region has a diameter less than a diameter of the projection of the second laser beam on the joint region.

11. The method according to claim 1 , wherein the preliminary weldment formed by the laser beam welding process solidifies more rapidly that the weld joint formed by the hybrid laser arc welding process.

12. The method according to claim 1 , further comprising placing a shim between the workpieces so that the faying surfaces contact the shim and the shim is within the intersurface portion of the joint region.

13. The method according to claim 12 , wherein the shim is melted by the laser beam welding process of the multistage welding process.

14. The method according to claim 1 , wherein the intersurface portion and the weld joint extend at least one centimeter beneath a surface portion of the joint region defined by first surfaces of the workpieces adjoining the faying surfaces that remain exposed after the workpieces are placed together.

15. The method according to claim 1 , wherein the electric arc is generated by a gas-shielded fusion arc welding process.

16. The method according to claim 1 , wherein the preliminary weldment solidifies and entraps gas bubbles therein, and gases within the bubbles are released from the preliminary weldment as a result of the hybrid laser arc welding process remelting the preliminary weldment.

17. The method according to claim 1 , wherein the welded assembly is a power generation, aerospace, infrastructure, medical, or industrial component.

18. The method according to claim 1 , wherein the welded assembly is a component of a wind turbine tower.

19. An apparatus for welding at least two workpieces together by metallurgically joining faying surfaces thereof that face each other to define a joint region, the apparatus comprising:

means for welding the workpieces together by performing a multistage welding process along the joint region, the welding means comprising means for conducting a laser beam welding process on the joint region and means for conducting a hybrid laser arc welding process on the joint region;

the laser beam welding process means being adapted to project a first laser beam onto the joint region and cause a projection of the first laser beam on the joint region to travel along the joint region, penetrate an intersurface portion of the joint region defined by and between the faying surfaces, and form a preliminary weldment in the joint region; and

the hybrid laser arc welding process means being adapted to conduct the hybrid laser arc welding process along the joint region and remelt the preliminary weldment to form a weld joint by simultaneously causing an electric arc and a second laser beam to travel along the joint region while melting a filler material with the electric arc and while overlapping projections of the second laser beam and the electric arc on the joint region to simultaneously form a weld pool in the preliminary weldment.

20. The apparatus according to claim 19 , wherein the first and second laser beams are created by means for splitting a primary laser beam, the splitting means causing the first and second laser beams to be perpendicular to a surface portion of the joint region.