Methods and laser welding devices for deep welding a workpiece

Abstract

The disclosure relates to methods and systems for deep welding a workpiece, a surface of the workpiece being irradiated by a first laser beam and a second laser beam. In a workpiece surface plane (OE) a first beam width B1 of the first laser beam is larger than a second beam width B2 of the second laser beam and in at least the workpiece surface plane (OE) the second laser beam lies inside the first laser beam. The intensity of the first laser beam alone is sufficient to produce a keyhole in the workpiece. The keyhole produced in the workpiece has a width KB in the workpiece surface plane (OE), KB substantially equaling B1, and B2≤0.75*KB. The methods and systems provide good seam quality, high penetration depth, and high welding speed.

1 . (canceled) 
     
     
         2 . A method for deep welding a workpiece, the method comprising:
 irradiating a surface of the workpiece using a first laser beam having a first laser power L 1  and a first beam width B 1  and a second laser beam having a second laser power L 2  and a second beam width B 2 ;
 wherein L 1  is at least 1 kW; 
 wherein B 2 <B 1 ; 
 wherein the second laser beam is directed onto an area of the workpiece surface plane within an area of the workpiece surface plane onto which the first laser beam is directed, and 
   wherein a beam parameter product (BPP) of the first laser beam (BPP 1 ) is greater than a beam parameter product of the second laser beam (BPP 2 ), wherein a high BPP represents a low beam quality;   guiding the first and second laser beams in a multicore fiber having at least one core fiber and a ring fiber, wherein the first laser beam is guided in the ring fiber and the second laser beam is guided in the core fiber, and the first and second laser beams exit from a fiber end of the multicore fiber before the workpiece;   directing the first and second laser beams by a common optical unit onto the workpiece, wherein the common optical unit comprises a collimation lens and a focusing lens; and   imaging the fiber end with the common optical unit in a common focus on or in the workpiece.   
     
     
         3 . The method of  claim 2 , wherein the first laser beam and the second laser beam have a same focal position or have focal positions spaced apart from one another by less than 1 mm in a direction perpendicular to the workpiece surface plane. 
     
     
         4 . The method of  claim 2 , wherein the method is used to produce a keyhole in the workpiece, and wherein focal positions of the first and second laser beams are located in the workpiece surface plane or below the workpiece surface inside a keyhole. 
     
     
         5 . The method of  claim 2 , wherein B 2 ≤0.75*B 1 . 
     
     
         6 . The method of  claim 2 , wherein B 2 ≤0.5*B 1 . 
     
     
         7 . The method of  claim 2 , wherein BPP 1 ≥2*BPP 2 . 
     
     
         8 . The method of  claim 2 , wherein BPP 1 ≥4*BPP 2 . 
     
     
         9 . The method of  claim 2 , wherein L 1  is less than or equal to L 2 . 
     
     
         10 . The method of  claim 2 , wherein L 2 ≥2*L 1 . 
     
     
         11 . The method of  claim 2 , wherein L 1  is greater than L 2 . 
     
     
         12 . The method of  claim 2 , wherein L 1  and L 2  are each 2.5 kW. 
     
     
         13 . The method of  claim 2 , wherein a welding speed feed rate is from 1 to 10 meters per minute. 
     
     
         14 . The method of  claim 2 , wherein the first laser beam has a first focus diameter of about 300 microns to about 440 microns, and the second laser beam has a second focus diameter of about 110 microns to about 150 microns. 
     
     
         15 . The method of  claim 2 , further comprising aligning the first laser beam and the second laser beam coaxially to have a common beam axis. 
     
     
         16 . The method of  claim 15 , wherein the common beam axis extends substantially perpendicularly to the workpiece surface. 
     
     
         17 . The method of  claim 2 , further comprising generating an original laser beam from a common laser source, coupling a first part of the original laser beam into the ring fiber to form the first laser beam, and coupling a second part of the original laser beam into the core fiber to form the second laser beam. 
     
     
         18 . The method of  claim 2 , further comprising
 generating the first laser beam with a first laser source,   generating the second laser beam with a second laser source, and   superimposing the first laser beam and the second laser beam with a beam splitter element.   
     
     
         19 . The method of  claim 18 , further comprising directing the superimposed laser beams onto the workpiece using a common focusing optical unit. 
     
     
         20 . A laser welding device for deep welding a workpiece, comprising:
 one or more laser sources that generate a first laser beam having a first laser power L 1  and a first beam width B 1  and a second laser beam having a second laser power L 2  and a second beam width B 2 , wherein
 L 1  is at least 1 kW, 
 B 1  is greater than B 2 , and 
 a beam parameter product (BPP) of the first laser beam (BPP 1 ) is greater than a beam parameter product of the second laser beam (BPP 2 ), wherein a high BPP represents a low beam quality; 
   a multicore fiber having at least one core fiber and a ring fiber, wherein the first laser beam is guided in the ring fiber and the second laser beam is guided in the core fiber, and wherein the first and second laser beams exit from a fiber end of the multicore fiber before a workpiece; and   a common optical unit arranged to direct the first laser beam and the second laser beam in a common focus onto or into the workpiece.   
     
     
         21 . The system of  claim 20 , wherein the common optical unit comprises a collimation lens and a focusing lens.