Patent Publication Number: US-2017368635-A1

Title: Oscillating remote laser welding on a fillet lap joint

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This PCT Patent Application claims the benefit of and priority to U.S. Provisional Patent Application Ser. No. 62/105,929 filed Jan. 21, 2015, the entire disclosure of the application being considered part of the disclosure of this application, and hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates generally to laser welding techniques, and more particularly to laser welding a fillet joint between metal materials for automotive vehicle applications. 
     2. Related Art 
     Structural components for automotive vehicles oftentimes include a plurality of metal materials joined together with a laser weld. Laser welding includes applying a concentrated heat source in the form of a laser beam along an interface between the two materials. The laser beam melts a portion of both materials along the interface, and the melted materials solidify to form the joint. This technique provides a strong joint and can be conducted at high rates, which is desirable in the production of automotive vehicle components. 
     Various different types of joints can be formed by laser welding, including overlap joints and fillet joints. Fillet joints are oftentimes preferred because they allow for a lightweight product and stable zinc degassing, which provides good weld quality. However, high position accuracy, which is difficult to achieve, is oftentimes required due to the size of the tolerances along the interface between the metal materials. One technique currently used to form fillet joints with high position accuracy includes using a remote laser along with a three-dimensional camera and an optical system. The camera and optical system precisely track the location of the interface and account for tolerances between the materials. However, this technique is oftentimes not suitable for use in certain light conditions and production environments, and the equipment is expensive. 
     SUMMARY OF THE INVENTION 
     The invention provides an improved method of joining two metal materials disposed at an angle relative to one another by laser welding. The laser welding step includes forming a fillet joint along an interface between the two materials by oscillating the laser beam as the laser beam moves laterally along the interface. The width of the fillet joint formed by the oscillating laser beam is greater than the width of the fillet joint that would be formed using a non-oscillating laser beam. The greater width of the fillet joint compensates for tolerances along the interface between the two materials without the expensive camera and optical system. In addition, the laser welding method provided by the invention is suitable for use in various light conditions and production environments. 
     The invention also provides a laser welding apparatus for joining two metal materials with a fillet joint. The apparatus provides a laser beam which oscillates as the laser beam moves laterally along an interface between the two materials. 
     The invention further provides a component for an automotive vehicle application including two metal materials and a fillet joint therebetween. The fillet joint is formed by laser welding with an oscillating laser beam to increase the width of the fillet joint and thus account for tolerances along the interface. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: 
         FIG. 1  illustrates a method of laser welding two materials according to an exemplary embodiment of the invention; 
         FIG. 1A  is an enlarged cross-sectional view of a portion of  FIG. 1  showing a laser beam in the process of forming a fillet joint between the two materials; 
         FIG. 2A  is a list of laser welding parameters used in an exemplary laser welding method; 
         FIG. 2B  includes laser welding parameters used in another exemplary laser welding method; 
         FIGS. 3A-3D  are screen shots of an exemplary software program used to implement the laser welding parameters; 
         FIGS. 4A-4C  are photographs of the fillet joint formed between the two materials according to an exemplary embodiment; 
         FIGS. 5A-5C  are photographs of the fillet joint formed between the two materials according to an another exemplary embodiment; 
         FIGS. 6A-6D  are photographs of the fillet joint formed between the two materials according to yet another exemplary embodiment; 
         FIGS. 7A-7D  are photographs of the fillet joint formed between the two materials according to another exemplary embodiment; 
         FIG. 8  is a photograph of the fillet joint formed between the two materials according to another exemplary embodiment; and 
         FIGS. 9A-9C  are photographs of a portion of a vehicle door including the fillet joint formed between two aluminum materials according to another exemplary embodiment. 
     
    
    
     DESCRIPTION OF THE ENABLING EMBODIMENTS 
     The invention provides an improved method for manufacturing metal components, especially those for use in automotive vehicle applications, including at least two metal materials  20 ,  22  joined together. An oscillating laser beam  26  is used to form a wide fillet joint  24 , also referred to as a fillet lap joint or a weld seam. The increased width of the fillet joint  24  compensates for tolerances along an interface  28  between the two materials  20 ,  22 . Thus, a reliable and strong fillet joint  24  can be formed in various light conditions and production environments. In addition, the fillet joint  24  is formed without the use of additional equipment, such as a three-dimensional camera and optical system for precise interface tracking.  FIGS. 1 and 1A  each show examples of the oscillating laser beam  26  joining the two materials  20 ,  22 . 
     The method begins by providing the metal materials  20 ,  22  to be joined. Various materials  20 ,  22  can be joined using the method, and the materials  20 ,  22  can be the same or different from one another. In one embodiment, the materials  20 ,  22  include steel or another iron-based material, aluminum, or an aluminum alloy. For example, both materials  20 ,  22  can be formed of steel, both materials  20 ,  22  can be formed of aluminum, or one material can be formed of steel and the other aluminum. The size and shape of the materials  20 ,  22  to be joined depends on the desired application of the finished component. In the exemplary embodiments shown in the Figures, both materials  20 ,  22  are provided in the form of a sheet. 
     In preparation to form the fillet joint  24 , the two materials  20 ,  22  are disposed at an angle relative to one another. In the exemplary embodiments, as best shown in  FIG. 1A , a side surface  30  of the first material  20  is disposed at an angle, for example perpendicular, to a top surface  32  of the second material  22 . However, the side surface  30  and top surface  32  could be disposed at other angles relative to one another. The two materials  20 ,  22  present the interface  28  at the intersection of the side surface  30  and the top surface  32 , and the fillet joint  24  is formed along the interface  28 . 
     As alluded to above, there are tolerances associated with the location of the interface  28  and/or the position of the materials  20 ,  22  relative to one another along the interface  28  that need to be accounted for during the laser welding process to ensure a strong fillet joint  24  is formed along the entire interface  28 . For example, the location of the interface  28  may extend along a curved, bent, non-straight, or random path, rather than a straight line. The distance between the side surface  30  and the top surface  32  may also vary along the interface  28 . These tolerances typically arise due to the various methods used to form the materials  20 ,  22 . For example, when the side surface  30  of the first material  20  is trimmed to a desired shape, there are tolerances associated with the trimmed side surface  30 . 
     Once the materials  20 ,  22  are provided and positioned at an angle relative to one another, the method includes laser welding the materials  20 ,  22  along the interface  28  to form the fillet joint  24  between the two materials  20 ,  22 . In the exemplary embodiment, this step includes forming the fillet joint  24  between the side surface  30  of the first material  20  and the top surface  32  of the second material  22 . However, the fillet joint  24  could be formed in other locations, depending on the shape of the materials  20 ,  22  to be joined. 
     As shown in  FIG. 1 , an apparatus  34  including a laser head  36  remote to the materials  20 ,  22  to be joined emits the oscillating laser beam  26 . In the exemplary embodiment, the laser head  36  moves laterally along the interface  28  while emitting the laser beam  26  toward the materials  20 ,  22 . Any type of laser capable of melting the metal materials  20 ,  22  can be used. The laser beam  26  melts a portion of the first material  20  and a portion of the second material  22  located along the interface  28 , and the melted portions solidify to form the fillet joint  24 . The size of the melted portions can vary depending on the size of the materials  20 ,  22 . 
     As stated above, the laser beam  26  continuously oscillates as it continuously moves laterally along the interface  28  in order to form the improved fillet joint  24 , which is wider than the fillet joint that would be formed using a non-oscillating laser beam. The laser beam  26  moves continuously until the entire fillet joint  24  between the side surface  30  and the top surface  32 . The wider fillet joint  24  provides a reliable and inexpensive way to compensate for the tolerances between the two materials  20 ,  22 . The oscillating laser beam  26  emitted from the laser head  36  moves in at least two different directions while the laser head  36  moves laterally along the interface  28 . In the exemplary embodiment shown in  FIGS. 1 and 1A , the laser beam  26  oscillates in two directions along an x-axis. The laser beam  26  could alternatively oscillate along a y-axis and/or a z-axis, instead of or in addition to oscillating along the x-axis. The path along which the laser beam  26  oscillates can comprise various different patterns, designs, or figures. For example, the path of the oscillating laser beam  26  can be at an angle, for example perpendicular, relative to the interface  28  between the two materials  20 ,  22 . In one embodiment, the laser beam oscillates in a “figure 8” pattern as the laser head  36  travels laterally along the interface  28 . The oscillating laser beam  26  influences the melt pool dynamics and the heat affected zone of the materials  20 ,  22 , which in turn contribute to the increased width w. 
     The width w of the fillet joint  24 , which should be great enough to compensate for the tolerances between the two materials  20 ,  22 , depends on the oscillation amplitude of the laser beam  26 . This is unlike comparative fillet joints formed using a non-oscillating laser beam, wherein the width w of the fillet joint depends on the beam size alone. The oscillation amplitude is the total distance covered by the oscillating laser beam  26  relative to a single axis during one oscillation cycle. For example, if the laser beam  26  oscillates by repeatedly moving 0.5 mm in one direction along an x-axis and then 0.5 mm in an opposite direction along the x-axis, the oscillation amplitude is 1.0 mm. The oscillation amplitude is typically predetermined prior to the laser welding process and depends on the size and shape of the materials  20 ,  22 , as well as the size of the tolerances between the materials  20 ,  22 . If there are significant variations in the interface  28 , or in the location of the side surface  30  of the first material  20  relative to the top surface  32  of the second material  22 , then the oscillation amplitude should be set to a relatively high value. If there are minor variations in the interface  28  or location of the side surface  30  of the first material  20  relative to the top surface  32  of the second material  22 , then a lower oscillation amplitude should be set. In the exemplary embodiment of  FIG. 1 , the oscillation amplitude is set to compensate for trim edge tolerances of +/−0.5 mm. 
     In certain embodiments, the method employs a plurality of oscillation amplitudes when forming the fillet joint  24  between the two materials  20 ,  22 . For example, the oscillating laser beam  26  can oscillate relative to both the x-axis and the y-axis as the laser head  36  moves laterally along the interface  28  between the materials  20 ,  22 . For example, when the laser beam oscillates according to the “figure 8” pattern, a first oscillation amplitude refers to movement of the laser beam  26  relative to the x-axis, and a second oscillation amplitude refers to movement of the laser beam  26  relative to the y-axis. 
     The method can also employ different oscillation amplitudes along different portions of the interface  28  between the materials  20 ,  22 . For example, if greater tolerances are located along one portion of the interface  28 , a greater oscillation amplitude is used along that portion of the interface  28 , while a lower oscillation amplitude is used along another portion of the interface  28 . The laser beam  26  can switch from one oscillation amplitude to another as the laser head  36  continuously moves laterally along the interface  28 . The oscillation amplitude can also be set or adjusted while the laser head  36  moves laterally along the interface  28 . 
     The method further includes setting other laser welding parameters, in addition to the oscillation amplitude, prior to or during the welding process. The other parameters typically include welding speed, energy or power level provided to the laser, pulse or no pulse, oscillation type figure or pattern, frequency of the oscillation figure, and defocus or no defocus. The welding speed is the speed at which the laser head  36  moves laterally along the interface  28 . The power parameter typically includes the percentage of available power used during the welding process. The pulse parameter can be activated when it is desirable to repeatedly turn the laser beam  26  on and off, for example to reduce the amount of heat applied to the materials  20 ,  22 . The oscillation type refers to the figure or pattern along which the laser beam  26  travels as the laser head  36  moves laterally along the interface  28 . For example, the laser beam  26  can move in two opposite directions relative to the x-axis and/or the y-axis. In one embodiment, the laser beam  26  travels in a “figure 8” pattern relative to the x-axis and or the y-axis. The frequency parameter refers to the number of oscillation figures per minute, for example the number of “figure 8” patterns per minute. The method typically includes applying a focused laser beam  26 . However, the defocus parameter can be activated when it is desirable to move the materials  20 ,  22  closer to the laser head  36 , or move the laser head  36  closer to the materials  20 ,  22 , for example to increase the size of the laser beam  26 . 
       FIG. 2A  illustrates the laser welding parameters for an exemplary method which includes oscillating the laser beam  26  according to the “figure 8” pattern. The method employs a first oscillation amplitude of 1.5 mm, which is the total distance covered by the laser beam  26  in the x-direction during one oscillation cycle, and a second oscillation amplitude of 0.5 mm, which is the total distance covered by the laser beam  26  in the y-direction during one oscillation cycle. In this embodiment, the welding speed is set to 30 mm/second, the power is set to 50% (2 kW), the pulse parameter is not activated, the frequency of the oscillation figure is 50 Hz, and the defocus parameter is not activated. 
       FIG. 2B  illustrates laser welding parameters for another exemplary method which includes oscillating the laser beam  26  according to the “figure 8” pattern, wherein the first oscillation amplitude is 1.5 mm and the second oscillation amplitude is 0.5 mm. In this embodiment, the welding speed is set to 50 mm/second, the power is set to 75% (3 kW), the pulse parameter is not activated, the frequency of the oscillation figure is 80 Hz, and the defocus parameter is not activated. 
       FIGS. 3A-3D  includes screen shots of an exemplary computer software program which can be used to implement the welding parameters. In the embodiment of  FIGS. 3A-3D , the oscillation figure type is the “figure 8” pattern described above. 
       FIGS. 4A-9C  are photographs showing materials  20 ,  22  joined together with the fillet joint  24  formed according to the method of the invention.  FIG. 4A  shows an example of the fillet joint  24  formed between the first material  20  and the second material  22  when welding speed is 50 mm/second and when the side surface  30  (trim edge) of the first material  20  is centered at 0 mm.  FIG. 4B  is a cross-sectional view of the fillet joint  24  of  FIG. 4A  along line B-B; and  FIG. 4C  is a magnified view of the fillet joint  24  of  FIG. 4A . 
       FIG. 5A  shows another example of the fillet joint  24  formed between the first material  20  and the second material  22  when the welding speed is 50 mm/second and when the side surface  30  (trim edge) of the first material  20  is centered at 0 mm.  FIG. 5B  is a cross-sectional view of the fillet joint  24  of  FIG. 5A  along line B-B; and  FIG. 5C  is a magnified view of the fillet joint  24  of  FIG. 5A . 
       FIG. 6A  shows another example of the fillet joint  24  formed between the first material  20  and the second material  22  when the welding speed is 50 mm/second and the side surface  30  (trim edge) of the first material  20  is spaced up to +0.6 mm from the centered position.  FIG. 6B  is a magnified view of the fillet joint  24  of  FIG. 6A .  FIG. 6C  is a cross-sectional view of the fillet joint  24  of  FIG. 6B  along line C-C, wherein an oscillation amplitude of 0.5 mm compensates for a tolerance of +0.3 mm.  FIG. 6D  is a cross-sectional view of the fillet joint  24  of  FIG. 6B  along line D-D, wherein an oscillation amplitude of 0.5 mm compensates for a tolerance of +0.5 mm. It was concluded that welding parameters used to weld the fillet joint  24  of  FIGS. 6A-6D  adequately compensate for a trim edge tolerance of up to +0.5 mm. 
       FIG. 7A  shows another example of the fillet joint  24  formed between the first material  20  and the second material  22  when the welding speed is 50 mm/second and the side surface  30  (trim edge) of the first material  20  is spaced from up to −1.2 mm from the centered position.  FIG. 7B  is a magnified view of the fillet joint  24  of  FIG. 7A .  FIG. 7C  is a cross-sectional view of the fillet joint  24  of  FIG. 7B  along line C-C, wherein an oscillation amplitude of 0.27 mm does not compensate for a tolerance of −1.0 mm.  FIG. 7D  is a cross-sectional view of the fillet joint  24  of  FIG. 7B  along line D-D, wherein an oscillation amplitude of 0.42 mm compensates for a tolerance of −0.3 mm. It was concluded that welding parameters used to weld the fillet joint  24  of  FIGS. 7A-7D  adequately compensate for a trim edge tolerance of up to −0.5 mm. 
       FIG. 8  is a photograph of the fillet joint  24  formed between the first and second materials  20 ,  22  according to another embodiment, wherein the welding parameters used to form the fillet joint  24  include a welding speed of 40 mm/second, power level of 3.8 kW, and oscillation frequency of 50 Hz. 
       FIGS. 9A-9C  are photographs of a portion of an example door for use in an automotive vehicle including the fillet joint  24  between the first and second materials  20 ,  22 . The fillet joint  24  is again formed using the oscillating laser beam  26  described above. The first and second materials  20 ,  22  are formed of  5182  aluminum and each has a thickness of 1.5 mm. 
     Obviously, many modifications and variations of the present invention are possible in light of the above teachings and may be practiced otherwise than as specifically described while within the scope of the following claims.