WO2025000096A1

WO2025000096A1 - Laser welding with shaped laser beam

Info

Publication number: WO2025000096A1
Application number: PCT/CA2024/050868
Authority: WO
Inventors: Florian Hanschmann
Original assignee: Magna International Inc.
Priority date: 2023-06-30
Filing date: 2024-06-27
Publication date: 2025-01-02

Abstract

A laser welder is configured to weld a first steel workpiece to a second steel workpiece to form a welded assembly. The welder generates a shaped laser beam to melt a portion of at least one of the workpieces to form a weld joint. During at least a part of the welding process, along at least one line passing through the laser beam, an intensity of the laser beam increases, then decreases, then increases. The welder includes electronics that control and/or change the shape of the laser beam during the welding process. A laser beam originating from the same laser generator as the welding laser beam may be used to remove at least a portion of an aluminum coating from one or more of the workpieces to be welded prior to welding.

Description

LASER WELDING WITH SHAPED LASER BEAM

CROSS REFERENCE

[0001] This application claims the benefit of priority from U.S. Provisional Application No. 63/524,295, filed June 30, 2023, titled “LASER WELDING WITH SHAPED LASERBEAM,” the entire contents of which are hereby incorporated by reference herein.

FIELD

[0002] The present patent application relates to a system and a method for laser welding steel sheets such as coated steel sheets.

BACKGROUND

[0003] Boron steel is often used in the automotive industry due to its ability to form a fully martensitic microstructure, which results in a high strength material. Despite low formability levels, boron steel can be hot stamped to increase formability, and create strong, formed structures such as a car door frame, through a hot stamping process. However, the boron steel alone tends to form an oxide layer at the surface during heat treatment. This oxide layer may create wear on the stamping die and prevent an adhesive painting process. Therefore, boron steel is often coated with an aluminum-silicon coating.

[0004] The aluminum-silicon coating on boron steel provides a barrier to prevent oxidization/scaling during the austenitization process and also allows the aluminum to react with iron within the coating. The iron-aluminum coating has a high melting point that is capable of withstanding the hot stamping process.

[0005] Hot stamping steel is commonly paired with laser blank welding due to the versatility of the process. Several blanks of different thicknesses and material can be joined together by laser welding and then hot stamped into one formed component. This has many advantages such as the ability to have some parts with structural strength and some with crash energy absorption capabilities, different material thicknesses to save on weight and costs, and better nesting of the blanks to reduce coil scrap rates.

[0006] The problem is that the aluminum-silicon coating can negatively affect the laser welding process. During welding, the aluminum has a tendency to mix with the iron and form a brittle intermetallic, which can cause cracking along the weld. The aluminum-silicon coating on the high strength, hot stamping steel (e.g., Usibor) pollutes the weld pool during laser welding. This iron-aluminum intermetallic adversely affects the weld’s hardenability. This also does not meet the mechanical property requirements (tensile strength, hardness, etc.) for a hot stamped component.

[0007] In a prior art method, ArcelorMittal Tailored Blanks (AMTB), the aluminum-silicon coating is removed using an ablation procedure (e.g., by an ablation laser). The highly accurate ablation process can remove the majority of the Al-Si coating, but leaves the intermetallic layer of Al-Fe. The uncoated blanks (or partially uncoated blanks) are then laser welded together. [0008] In another prior art method, powder (supplied by a power feed nozzle) or fdler wire (supplied by a filler wire feeding system) is added to bind the aluminum-silicon coating on the base metal, during the laser welding procedure, for example as shown in U.S. Patent Application PublicationNo 2021/0078106, the entire contents of which are incorporated herein by reference.

[0009] The present patent application provides improvements to systems and methods for laser welding steel blanks.

SUMMARY

[0010] One or more non-limiting embodiments provide a method and system for laser welding a first steel workpiece to a second steel workpiece to form a welded assembly.

[0011] According to one or more of these embodiments, the method includes: positioning the first and second workpieces to form an interface therebetween, using a laser beam to melt a portion of at least one of the workpieces at the interface, and resolidifying melted metal at the interface to form a weld joint between the first and second workpieces.

[0012] According to one or more of these embodiments, during at least a part of said using of said laser beam, along at least one line passing through the laser beam, an intensity of the laser beam increases, then decreases, then increases.

[0013] According to one or more of these embodiments, during at least a part of said using of said laser beam, an intensity of the laser beam at a middle of the beam is lower than an intensity of the laser beam at a different portion of the beam.

[0014] According to one or more of these embodiments, the method also includes changing a shape of the laser beam from a first shape to a second shape during said using of the laser bean to melt a portion of at least one of the work pieces.

[0015] According to one or more of these embodiments, the first shape and second shape each originate from the same laser generator. [0016] According to one or more of these embodiments, said changing occurs without physical movement of any optical element relative to any other optical element.

[0017] According to one or more of these embodiments, during at least a part of said using of said laser beam, and as viewed in a cross-section that is perpendicular to a path of the laser beam, a shape of the beam includes a closed-loop shape.

[0018] According to one or more of these embodiments, during at least a part of said using of said laser beam, and as viewed in a cross-section that is perpendicular to a path of the laser beam, a shape of the beam includes a figure eight (“8”) shape.

[0019] According to one or more of these embodiments, during at least a part of said using of said laser beam, and as viewed in a cross-section that is perpendicular to a path of the laser beam, a shape of the beam includes a spiral shape.

[0020] According to one or more of these embodiments, the first and second work pieces each comprise a steel material with an aluminum based coating thereon.

[0021] According to one or more of these embodiments, the method also includes feeding a filler wire to the interface, wherein said laser beam melts a portion of the filler wire.

[0022] According to one or more of these embodiments, the filler wire comprises a composition that includes nickel and chromium, and the method further comprises binding the filler wire with aluminum in the aluminum based coating.

[0023] According to one or more of these embodiments, the weld joint is formed between the first and second workpieces without previously removing the aluminum based coatings from the first or second workpieces.

[0024] According to one or more of these embodiments, the method also includes using a laser beam to remove at least a portion of the aluminum based coating from portions of the first and second work pieces, respectively, at or adjacent to where the weld joint will be formed.

[0025] According to one or more of these embodiments, the laser beam used for said removing of at least a portion of the aluminum originates from the same laser generator as the laser beam used for said melting of the portion of at least one of the workpieces.

[0026] According to one or more of these embodiments, the laser beam used for said removing of at least a portion of the aluminum has a different laser beam shape than the laser beam used for said melting of the portion of at least one of the workpieces.

[0027] According to one or more of these embodiments, the weld joint is formed without the use of a filler. [0028] One or more non-limiting embodiments provide a laser welder configured to weld a first steel workpiece to a second steel workpiece an interface between the first and second steel workpieces to form a welded assembly. According to one or more of these embodiments, the laser welder is configured to generate a welding laser beam such that along at least one line passing through the laser beam, an intensity of the laser beam increases, then decreases, then increases.

[0029] According to one or more of these embodiments, the welder also includes a laser generator configured to generate a seed laser beam.

[0030] According to one or more of these embodiments, the welder also includes at least one beam splitter positioned and configured to split the seed laser beam into a plurality of split laser beams.

[0031] According to one or more of these embodiments, the welder also includes a plurality of optical amplifiers positioned and configured to amplify respective ones of the plurality of split laser beams.

[0032] According to one or more of these embodiments, the welder also includes a plurality of phase modulators positioned and configured to modulate a phase of respective ones of the plurality of split laser beams.

[0033] According to one or more of these embodiments, the welder also includes an electronics controller operatively connected to the plurality of optical amplifiers and the plurality of phase modulators. The electronics controller is configured to control the optical amplifiers and phase modulators so as to control a shape of a beam formed by the combination of split beams

[0034] According to one or more of these embodiments, the laser welder is configured to change a shape of the laser beam from a first shape to a second shape while welding the first and second workpieces together.

[0035] According to one or more of these embodiments, the welder also includes a laser generator capable of forming the first shape and second shape.

[0036] According to one or more of these embodiments, the laser welder is configured to change a shape of the laser beam without physical movement of any optical element relative to any other optical element.

[0037] According to one or more of these embodiments, as viewed in a cross-section that is perpendicular to a path of the laser beam, a shape of the beam includes a closed-loop shape. [0038] According to one or more of these embodiments, as viewed in a cross-section that is perpendicular to a path of the laser beam, a shape of the beam includes a figure eight shape.

[0039] According to one or more of these embodiments, as viewed in a cross-section that is perpendicular to a path of the laser beam, a shape of the beam includes a spiral shape.

[0040] According to one or more of these embodiments, the laser welder is configured to generate and use a laser beam to remove at least a portion of an aluminum based coating from portions of the first and second work pieces, respectively, at or adjacent to where the weld joint will be formed.

[0041] According to one or more of these embodiments, the laser welder comprises a laser generator that is configured to generate a laser beam used for said removing of at least a portion of the aluminum

[0042] According to one or more of these embodiments, said laser generator is configured to generate a laser beam used for melting at least a portion of at least one of the workpieces during a welding process.

[0043] According to one or more of these embodiments, the laser welder includes a filler wire feed configured to feed a filler wire to the interface when the first and second workpieces are being welded to each other to form the welded assembly.

[0044] According to one or more of these embodiments, the filler wire comprises a composition that includes nickel and chromium, and the filler wire is configured to bind with aluminum in an aluminum based coating of the first and second workpieces so as to minimize formation of brittle intermetafiics due to mixing of the aluminum in the aluminum based coating with the iron/steel material in the weld joint.

[0045] One or more of these and/or other aspects of various embodiments of the present invention, as well as the methods of operation and functions of the related elements of structure and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this specification, wherein like reference numerals designate corresponding parts in the various figures. In one or more embodiments, the structural components illustrated herein are drawn to scale. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the invention. In addition, it should be appreciated that structural features shown or described in any one embodiment herein can be used in other embodiments as well. As used in the specification and in the claims, the singular form of “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise.

[0046] All closed-ended (e.g., between A and B) and open-ended (greater than C) ranges of values disclosed herein explicitly include all ranges that fall within or nest within such ranges. For example, a disclosed range of 1-10 is understood as also disclosing, among other ranges, 2-10, 1-9, 3-9, etc. Similarly, where multiple parameters (e.g., parameter C, parameter D) are separately disclosed as having ranges, the embodiments disclosed herein explicitly include embodiments that combine any value within the disclosed range of one parameter (e.g., parameter C) with any value within the disclosed range of any other parameter (e.g., parameter D).

BRIEF DESCRIPTION OF THE DRAWINGS

[0047] For a better understanding of various embodiments as well as other objects and further features thereof, reference is made to the following description which is to be used in conjunction with the accompanying drawings, where:

[0048] FIG. 1 shows a system in which a fdler wire having a composition including nickel and chromium is used, during laser welding procedure, to bind aluminum-silicon coating on the steel blanks in accordance with an embodiment of the present patent application;

[0049] FIG. 2 shows a system in which a fdler wire having a composition including nickel and chromium is used, during laser welding procedure, to bind aluminum-silicon coating on the steel blanks in accordance with another embodiment of the present patent application;

[0050] FIG. 3 shows a system in which a fdler wire having a composition including nickel and chromium is used, during laser welding procedure, to bind the aluminum-silicon coating on the blanks in accordance with an embodiment of the present patent application;

[0051] FIG. 3A shows a system in which a fdler wire having a composition including nickel and chromium is used, during laser welding procedure, to bind the aluminum-silicon coating on the blanks in accordance with another embodiment of the present patent application;

[0052] FIG. 4 shows a fdler wire feed in accordance with an embodiment of the present patent application;

[0053] FIG. 4A shows a fdler wire feed in accordance with another embodiment of the present patent application;

[0054] FIG. 5 shows a wire feed nozzle and a welding laser in accordance with an embodiment of the present patent application; [0055] FIG. 6 shows a system in which a filler wire having a composition of nickel and chromium is used, during laser welding procedure, to bind the aluminum-silicon coating on the blanks, wherein the system is at a weld start position, in accordance with an embodiment of the present patent application;

[0056] FIG. 7 shows a system in which a filler wire having a composition of nickel and chromium is used, during laser welding procedure, to bind the aluminum-silicon coating on the blanks, wherein the system is at a weld end position, in accordance with an embodiment of the present patent application;

[0057] FIGS. 8, 8A and 9 show a system in which a filler wire having a composition of nickel and chromium is used, during laser welding procedure, to bind the aluminum-silicon coating on the blanks in accordance with an embodiment of the present patent application;

[0058] FIG. 10 is a diagrammatic view of a laser welder according to one or more embodiments; and

[0059] FIGS. 11A-D are cross-sectional views of shaped laser beams or beam spots according to various embodiments.

[0060] FIG. 12 is a side view of a weld joint according to various embodiments.

[0061] FIGS. 13-14 are diagrammatic side views of a laser ablation process according to various embodiments.

DETAILED DESCRIPTION OF THE DRAWINGS

[0062] FIGS. 1-9 show a system 100 that includes a laser welder 102 and a filler wire feed 104. In one or more embodiments, the laser welder 102 is configured to weld a first workpiece 106 to a second workpiece 108 (and optionally additional workpieces, not shown) to form a welded assembly 110. Each workpiece 106, 108 is formed from a steel material. According to one or more embodiments, each workpiece 106, 108 comprises an aluminum based coating 118 thereon. In one or more embodiments, the workpieces 106, 108 are positioned together to form an interface 112 therebetween and a weld joint 114 is formed by the laser welder 102 between the workpieces 106, 108 along the interface 112. In one or more embodiments, the filler wire feed 104 is configured to feed a filler wire 116 to the interface 112 when the workpieces 106, 108 are being welded to each other (i.e., by the laser welder 102) to form the welded assembly 110. In one or more embodiments, the filler wire 116 comprises a composition that includes nickel and chromium. In one or more embodiments, the filler wire 116 is configured to bind with aluminum in the aluminum based coating 118 so as to minimize formation of brittle intermetallics due to mixing of the aluminum in the aluminum based coating 118 with iron or steel material in the weld joint 114.

[0063] In one or more embodiments, the filler wire 116 is configured to bind to aluminum in the aluminum based coating 118 so as to render the aluminum in the aluminum based coating 118 inert in the weld pool/joint 114. In one or more embodiments, the filler wire 116 is configured to bind to aluminum in the aluminum based coating 118 so as to prevent the formation of an aluminum - iron intermetallic phase in the weld bead/joint 114. In one or more embodiments, the filler wire 116 is configured to bind to aluminum in the aluminum based coating 118 so as to minimize mixing of the aluminum in the aluminum-based coating 118 with the iron/steel material in the weld joint 114.

[0064] In one or more embodiments, the laser welder 102 is configured to irradiate a laser beam 120 to weld the workpieces 106, 108 to form the welded assembly. In one or more embodiments, the laser welder 102 includes a direct diode laser. In another embodiment, the laser welder 102 includes a YAG laser. In yet another embodiment, the laser welder 102 includes a CO2 laser. In yet another embodiment, the laser welder 102 includes a fiber laser. In one or more embodiments, the laser welder 102 is an automated laser welder.

[0065] In one or more embodiments, during the laser weld procedure, the laser welder 102 is configured to produce either a continuous high power density laser beam 120 or a pulsed high power density laser beam 120 to melt the materials of the workpieces 106, 108 being joined. In one or more embodiments, the spot size of the laser beam 120 may be varied by adjusting the focal point of the laser beam 120. In one or more embodiments, the laser welder 102 includes a focus lens 152 as shown in FIG. 9 that is configured to focus the laser beam 120 onto the desired spot on the workpieces 106, 108 or onto the weld interface between the workpieces 106, 108.

[0066] In another embodiment, as shown in FIGS. 10-11, the laser welder 102 creates a shaped laser beam 120.

[0067] In one or more embodiments, the system 100 includes a controller and/or one or more processors that are configured to control components of the system 100. In one or more embodiments, the one or more processors are configured to control the movement of the workpieces 106, 108 during the laser weld procedure. In one or more embodiments, the movement of the workpieces 106, 108 is achieved through movement of the worktable. In one or more embodiments, the one or more processors are configured to control the movement and/or the operation of the laser welder 102 during the laser weld procedure. In one or more embodiments, the one or more processors are configured to control the operation of the filler wire feed during the laser weld procedure. In one or more embodiments, the one or more processors is/are configured to control the movement of the laser beam 120 across the surfaces of the workpieces 106, 108. In one or more embodiments, the one or more processors is configured to control the shape of the laser beam 120 so as to vary the laser beam 120 shape over time during the welding process. In one or more embodiments, the one or more processors is/are configured to control the movement of the filler wire feed material across the surfaces of the workpieces 106, 108.

[0068] In one or more embodiments, the laser welder 102 is configured to be dynamically adjustable to the workpieces 106, 108 into a variety of different joint configurations, such as lap joints, butt joints, T-joints, comer joints or edge joints. In one or more embodiments, the laser wattage, spot size, and/or beam shape of the laser welder 102 are chosen based on the material (s) being welded, the material thickness and the joint configuration.

[0069] In one or more embodiments, the laser welder 102 includes an inert shield (or protective) gas system. In one or more embodiments, the inert shield gas system is configured to supply or provide an inert shield gas onto the workpieces 106, 108. In one or more embodiments, the inert shield gas is directed onto portions of the surfaces of the workpieces 106, 108 during the laser weld procedure. In one or more embodiments, the inert shield gas may be an inert gas (e.g., carbon dioxide, argon, helium, or any combination thereof) that is configured to shield the molten weld pool. In one or more embodiments, the inert shield gas system of the laser welder 102 include a gas flow sensor that is configured to sense/detect the flow rate of the inert shield gases used in the laser weld procedure. In one or more embodiments, the gas flow sensor is configured to provide a signal proportional to the gas flow rate in the inert shield gas line. In one or more embodiments, the one or more processors of the laser welder 102 are configured to stop welding if the gas flow rate of the inert shield gas is not within a predetermined gas flow rate range. In one or more embodiments, the inert shield gas system is optional.

[0070] In one or more embodiments, the filler wire feed 104 is a filler wire feed shown in FIGS. 3-5. In one or more embodiments, the filler wire feed 104 includes one or more wire feed cables/tubings 202, a filler wire feed box 204, a filler wire spool 206, a wire feeder 208, and a wire feed nozzle 210.

[0071] In one or more embodiments, the filler wire 116 is stored on the filler wire spool 206, which is rotatably mounted in the filler wire feed 104. In one or more embodiments, the filler wire 116 is guided by or passes through the one or more wire feed cables/tubings 202 positioned between the fdler wire spool 206 and the wire feed nozzle 210. In one or more embodiments, the fdler wire 116 then exits through the wire feed nozzle 210. In one or more embodiments, the fdler wire feed 104 includes drive rollers (e.g., electrical powered) that are configured to move the fdler wire 116 through one or more wire feed cables/tubings 202 and the wire feed nozzle 210. In one or more embodiments, all the components of the fdler wire feed 104 are made of material that is configured to withstand high weld temperatures.

[0072] In one or more embodiments, the wire feeder 208, shown in FIG. 3, is a master wire feed drive. In one or more embodiments, the fdler wire feed box 204, shown in FIG. 3, is a slave wire feed drive. In one or more embodiments, the master wire feed drive 208 and the slave wire feed drive 204, both shown in FIG. 3, are servo-motor wire feed drives. In one or more embodiments, the slave wire feed drive 204 is configured to pull the wire off the fdler wire spool and feed the fdler wire toward the master wire feed drive 208. In one or more embodiments, the master wire feed drive 208 is configured to control the speed at which the fdler wire is fed into the process. In one or more embodiments, both the servo-motor wire feed drives (i.e., the master wire feed drive 208 and the slave wire feed drive 204 as shown in FIG. 3) are controlled by an E-Box (not shown in the figures). In one or more embodiments, the E- box is configured to receive wire feed commands from a cell control (e.g., PLC or robot) and coordinate the two drives to deliver the commanded wire rate. In one or more embodiments, the part names for the master wire feed drive 208 and the slave wire feed drive 204 (shown in FIG. 3) are model designations for an Abicor-Binzel wire feed system. In one or more embodiments, other equivalent and interchangeable systems made by different manufacturers may be used for the master wire feed drive 208 and the slave wire feed drive 204 (as shown in FIG. 3). In one or more embodiments, the filler wire can also be stored on a filler wire barrel or other storage systems as would be appreciated by one skilled in the art. In one or more embodiments, the filler wire barrels, as opposed to filler wire spools, are used as these filler wire barrels last longer.

[0073] In one or more embodiments, each of the workpiece 106 and the at least one additional workpiece 108 is formed from a steel material. In one or more embodiments, each of the workpieces 106, 108 may be referred to as base metal. In one or more embodiments, each of the workpieces 106, 108 is formed from a steel alloy material. In one or more embodiments, each of the workpieces 106, 108 is formed from boron steel. In one or more embodiments, each of the workpieces 106, 108 is formed from manganese boron steel. In one or more embodiments, the workpiece 106 is formed from a different steel grade, strength, and/or thickness than the workpiece 108.

[0074] In one or more embodiments, the workpieces 106, 108 are held on a worktable prior to the laser weld procedure and during the laser weld procedure.

[0075] In one or more embodiments, each of the workpieces 106, 108 comprises an aluminum based coating 118 thereon. In one or more embodiments, each of the workpieces 106, 108 comprises the aluminum based coating 118 on both top and bottom surfaces 122 and 124. In one or more embodiments, the workpieces 106, 108 comprises an aluminum silicon coating 118 thereon.

[0076] There is a theory and some preliminary experimental results that adding trace amounts of a metallurgical additive in the form of a powder (i.e., consisting of substantial amounts of Nickel and Chromium) can modify the aluminum-iron reaction in the weld melt pool, and improve weld properties. The powdered additive, however, has some drawbacks.

[0077] In one or more embodiments, trace amounts of a metallurgical additive are added in the form of the fdler wire 116. Additional studies have been performed with the metallurgical additive that yielded results that are more positive. It is also found that the metallurgical additive in the form of the fdler wire 116 yields good quality welds in regards to strength, fatigue, and corrosion. The physical structure of the weld formed using the method according to one or more embodiments also meets the criteria of all OEMs (Original Equipment Manufacturers). Since the metallurgical additive acts as a fdler material, the laser welds handle variance in gap sizes well. In one or more embodiments, the fdler wire 116 and powdered additive are applied simultaneously.

[0078] In one or more embodiments, the fdler wire 116 is configured to reduce the effect of gap variances and fill in weld defects such as undercuts. In one or more embodiments, the fdler wire 116 is also configured to bind with the aluminum silicon coating to provide acceptable weld mechanical properties. In one or more embodiments, the fdler wire 116 is also tracked using an encoder, which makes quality assurance and tracking much more efficient and certain. In one or more embodiments, the fdler wire feed speed is varied using adaptive welding to vary the weld speed according to gaps or other miscellaneous features in the weld line. Lastly, this procedure or process in accordance with one or more embodiments is cleaner because loose powder (i.e., powdered additive) will not make its way onto the floor and/or tooling.

[0079] In one or more embodiments, the chemical composition of the fdler wire 116 includes substantial amounts of Nickel and Chromium. In one or more embodiments, the nickel and chromium filler wire 116 is configured to bind with the aluminum-silicon coating of Usibor steel. However, in other embodiments, Nickel and/or Chromium may be reduced or even eliminated from the filler wire.

[0080] In one or more embodiments, the filler wire may include other elements such as the alloying elements in the base material (Usibor) that promote hardenability of the weld joint along with Nickle and Chromium.

[0081] In one or more embodiments, the percentage weight of Nickel in the filler wire 116 is between 51.10 and 63.90. In one or more embodiments, the percentage weight of Nickel in the filler wire 116 is between 0 and 63.90. In one or more embodiments, the percentage weight of Chromium in the filler wire 116 is between 7.20 and 16.00. In one or more embodiments, the percentage weight of Chromium in the filler wire 116 is 19. In one or more embodiments, the percentage weight of Chromium in the filler wire 116 is between 7.20 and 24.00.

[0082] In one or more embodiments, the percentage of Nickel in the filler wire 116 is between 1.68 and 2.85. In one or more embodiments, the percentage of Chromium in the filler wire 116 is between 0 and 2.7. In one or more embodiments, the percentage of Chromium in the filler wire 116 is between 0.49 and 0.83. In one or more embodiments, the percentage of Chromium in the filler wire 116 is between 0.49 and 0.95. In one or more embodiments, the percentage of Chromium in the filler wire 116 is between 0.49 and 1.00.

[0083] In one or more embodiments, the filler wire 116 material includes nickel based steel alloy, for example, Hastelloy C267. In one or more embodiments, the Hastelloy C267 material has 57% of Ni and 16% of Cr.

[0084] In one or more embodiments, the filler wire 116 material includes 4340 wire. In one or more embodiments, the 4340 wire material includes 1.8% Nickel and 0.78% Chromium.

[0085] In another embodiment, the percentage of Nickel in the filler wire 116 is between 7.80 and 10.40. In another embodiment, the percentage of Chromium in the filler wire 116 is between 2.10 and 2.70.

[0086] In yet another embodiment, the percentage of Nickel in the filler wire 116 is between 2.72 and 4.63. In yet another embodiment, the percentage of Chromium in the filler wire 116 is between 0.72 and 1.22.

[0087] In one or more embodiments, the carbon content in the filler wire 116 is between 0% and 0.59%. In one or more embodiments, the carbon content in the filler wire 116 is between 0.91% and 2.00%. In one or more embodiments, the carbon content in the filler wire 116 is created prior to drawing the filler wire 116. In one or more embodiments, the filler wire 116 includes a gradient of diffused carbon therein. In one or more embodiments, the fdler wire 116 undergoes a carburizing process. In one or more embodiments, the carbon content is added using a carburizing process on an already drawn fdler wire. In one or more embodiments, the carburizing process is configured to diffuse the carbon into the filler wire 116. In one or more embodiments, the carbon is added in any other alternate process/procedure that would be appreciated by one skilled in the art.

[0088] In one or more embodiments, the filler wire 116 may include up to 1% weight of Carbon. In one or more embodiments, the filler wire 116 may include from 0.35 to 0.80 % weight of Carbon. In one or more embodiments, the filler wire 116 may include from 0.35 to 0.90 % weight of Carbon. In one or more embodiments, the carbon present in the filler wire 116 may have an impact on hardness and microstructure. In one or more embodiments, the carbon present in the filler wire may substantially help the metallurgy.

[0089] In one or more embodiments, the Manganese (Mn) content in the filler wire 116 is between 0% and 0.29%. In one or more embodiments, the Manganese content in the filler wire 116 is between 0.3% and 0.9%. In one or more embodiments, the Manganese content in the filler wire 116 is between 0.91% and 2%.

[0090] In one or more embodiments, a method of cutting the material may affect the desired, but non-limiting, chemical composition of the filler material. In one or more embodiments, the preparation of the edges may affect the desired, but non-limiting, chemical composition of the filler material. In one or more embodiments, the trim type of the parts/edges may affect the desired, but non-limiting, chemical composition of the filler material. In one or more embodiments, the edges of the workpieces are prepared by laser cutting procedure. In another embodiment, the edges of the workpieces are prepared by shear cutting procedure. In one or more embodiments, the edges are machined. For example, in one or more embodiments, the chemical composition of the filler material used for the laser cut edges may be different than the chemical composition of the filler material used for the sheared edges.

[0091] In one or more embodiments, the nickel in the filler wire 116 is configured to bind with the aluminum in the aluminum based coating 118, while the chromium in the filler wire 116 is configured to harden the weld for improved mechanical performance.

[0092] In one or more embodiments, the filler wire may include 4340 Chrome-Molybdenum low alloy wire. In one or more embodiments, the filler wire may include Carburized 4340 wire. In one or more embodiments, the filler wire may include Stainless Steel 316L wire. [0093] In one or more embodiments, in addition to the effects on the weld, the fdler wire 116 is also configured to reduce the manufacturing costs of laser blank welding aluminumsilicon coated boron steel. First, if the addition of the metallurgical additive in the form of the filler wire 116 neutralizes the aluminum-silicon coating, then the blanks do not have to go through a laser ablation procedure (e.g., as shown discussed in the prior art method in the background section of the present patent application). This would save costs on the capital investments in the laser ablation equipment and manufacturing costs by eliminating the requirement for a W.I.P. (work in progress).

[0094] Secondly, with the addition of the metallurgical additive in the form of the filler wire 116, the tolerance on the weld gap will be larger, meaning that a fine blanking press may not be required. This may save additional capital costs because a conventional blanking press can be used.

[0095] Lastly, since the addition of the metallurgical additive in the form of the filler wire 116 is a more robust process/procedure that is configured to fill in undercuts, it could reduce the scrap rate of the process/procedure.

[0096] FIGS. 1-2 and 6-7 show a method 500 for laser welding the workpieces 106, 108 to form a welded assembly in accordance with one or more embodiments of the present application. In one or more embodiments, the method 500 comprises positioning (e.g., procedure 502 as shown in FIG. 5) the workpiece 106 and the at least one additional workpiece 108 together to form the interface 112 therebetween. As noted above, in one or more embodiments, each of the workpieces 106, 108 is formed from a steel material. As noted above, in one or more embodiments, each of the workpieces 106, 108 comprises the aluminum based coating 188 thereon. In one or more embodiments, the method 500 also comprises: forming (e.g., procedure 504 as shown in FIG. 2) the weld joint 114, by the laser welder 102, between the workpieces 106, 108 along the interface 112; and feeding (e.g., procedure 506 as shown in FIGS. 1 and 2) the filler wire 116, by a filler wire feed 104, to the interface 112 when the workpiece 106 and the at least one additional workpiece 108 are being welded to each other to form the welded assembly.

[0097] FIGS. 1 and 2 show two orthogonal views of the same wire feed arrangement, in which the filler wire feed 104 is positioned in front with respect to the laser welder 102 and/or the workpieces 106 and 108. As shown in FIG. 2, the filler wire feed 104 (i.e., supplying the filler wire 116) is positioned ahead (i.e., in the direction of the welding Dw) of the laser welder 102. In one or more embodiments, as shown in FIG. 1, the filler wire feed 104 (i.e., supplying the filler wire 116) is positioned on the same longitudinal axis as the laser welder 102. In one or more embodiments, as shown in FIG. 1, the filler wire feed 104 (i.e., supplying the filler wire 116) is positioned at an angle with respect to the workpieces 106, 108. FIGS. 1 and 2 show different views of the same process. In one or more embodiments, the filler wire is fed at an angle.

[0098] FIG. 6 shows a procedure of the method 500 in which a weld start position in shown, while FIG. 7 shows a procedure of the method 500 in which a weld end position is shown. Both the laser welder 102 (projecting the laser bean 120) and the filler wire feed 104 (providing the filler wire 116) are moved over a weld path between the weld start position of FIG. 6 and the weld end position of FIG. 7.

[0099] In one or more embodiments, as discussed above, the filler wire 116 comprises a composition that includes nickel and chromium. In one or more embodiments, the method 500 further comprises binding the filler wire 116 with aluminum in the aluminum based coating 118, when the workpieces 106, 108 are being welded to each other to form the welded assembly, so as to minimize the formation of brittle intermetallics due to the mixing of the aluminum in the aluminum based coating 118 with the iron/steel material in the weld joint 114.

[00100] In one or more embodiments, the method 500 further binding the filler wire with aluminum in the aluminum based coating, when the workpiece and the at least one additional workpiece are being welded to each other to form the welded assembly, so as to minimize the formation of brittle intermetallics due to the mixing of the aluminum in the aluminum based coating 118 with the iron/steel material in the weld joint 114.

[00101] In one or more embodiments, aluminum reaction with iron is minimized. In one or more embodiments, the aluminum-iron intermetallic is the main brittle intermetallic being formed. In one or more embodiments, the filler wire is configured to prevent the formation of this aluminum-iron intermetallic. In one or more embodiments, the nickel in the filler wire is configured to bind with the aluminum.

[00102] In one or more embodiments, the tensile strengths of the weld joint and the workpieces are equal to or greater than 1200 MPa. In one or more embodiments, the tensile strengths of the workpieces are equal to 1500 MPa.

[00103] In one or more embodiments, the hardnesses of the weld joint and the workpieces are equal to or greater than 400HV.

[00104] In one or more embodiments, the workpiece 106 and/or 108 includes Usibor® (a high resistance boron micro alloyed aluminum-silicon steel). In one or more embodiments, the workpieces 106 and/or 108 include Ductiobor® (a high resistance boron micro alloyed aluminum-silicon steel). In one or more embodiments, the tensile strengths of the weld joint and the workpieces that are made of Usibor® and/or Ductiobor® are about 500 MPa. In one or more embodiments, the hardnesses of the weld joint and the workpieces that are made of Usibor® and/or Ductiobor® are less than 400HV. In one or more embodiments, the workpieces include any brand of boron steel that uses an aluminum silicon coating.

[00105] In one or more embodiments, the weld joint formed using the system and method of the present patent application includes a martensite microstructure. In one or more embodiments, the workpieces are welded together to form weld assembly. In one or more embodiments, the weld assembly then undergoes a heat treatment process and a cooling process. In one or more embodiments, during the heat treatment process, the metallurgy of the weld assembly is 100% martensitic. After the cooling process, the weld assembly has a martensitic microstructure. In one or more embodiments, there may be small trace amounts of other microstructures, but the vast majority of the weld assembly is martensitic microstructure after the heat treatment process.

[00106] In one or more embodiments, the method 500 of the present patent application provides shifts in a continuous cooling transformation (CCT) phase diagram to promote martensitic microstructure.

[00107] In one or more embodiments, unlike the AMTB procedure as described in the background section of the present patent application, there is no ablation of the aluminum based coating or uncoating of the aluminum based coating required in the method 500 of the present patent application. In one or more embodiments, the method 500 does not require an ablation procedure (e.g., by an ablation laser) to remove the aluminum-silicon coating. In one or more embodiments, the method 500 does not require any uncoating procedure to remove the aluminum-silicon coating. This creates a cheaper and faster manufacturing process or procedures.

[00108] In one or more embodiments, unlike the powder process or procedure as described in the background section of the present patent application, the method 500, in one or more embodiments, is a cleaner procedure or process. That is, there is no residual powder on part surface(s), on the floor, and/or tooling surface(s). In other words, the cleaner tooling surface(s), the cleaner part surface(s), and the cleaner floor are better for a production environment to keep the manufacturing cell cleaner and prevent powder from creating an unclean environment and potentially clogging things. [00109] In one or more embodiments, the method 500, in one or more embodiments, is performed on blanks having thicknesses that are less than 1.8 mm. In one or more embodiments, the method 500 is also performed on blanks having same thickness. In one or more embodiments, the method 500 is also performed on blanks having stepped joints. In one or more embodiments, the method 500 is configured to weld together steel blanks with a range of thickness from a minimum of 0.5 mm to a maximum of 5.0 mm, with a maximum thickness ratio of 5: 1. In one or more embodiments, the method 500 is configured to weld together steel blanks having a step thickness of less than 0.40 mm. In one or more embodiments, step thickness difference or jump in thickness is less than 0.19 mm or greater than 0.41 mm. In one or more embodiments, the method 500 is configured to weld all reasonable steel sheet thickness for tailored blanks.

[00110] In one or more embodiments, the system 100 of the present patent application is able to perform laser weld procedure on all reasonable steel sheet thickness for tailored blanks as the system 100 uses an optical seam tracker 600 as shown in FIGS. 8 and 9. In one or more embodiments, the optical seam tracker 600 is configured to project a laser beam 602 to illuminate the weld interface. In one or more embodiments, the optical seam tracker 600 includes an optical seam camera. In one or more embodiments, the camera is configured to see the weld interface or weld joint location. In one or more embodiments, the optical laser is used to inspect, measure, and evaluate the seam prior to welding. In one or more embodiments, the optical laser is used to inspect, measure, and evaluate the weld. In one or more embodiments, there is an optical laser in front and behind the weld process to inspect, evaluate, and measure the weld seam and weld bead.

[00111] As shown in FIG. 9, both the optical seam tracker 600 and the filler wire feed 104 (i.e., supplying the filler wire 116) are positioned ahead (i.e., in the direction of the welding Dw) of the laser welder 102. In another embodiment, the optical seam tracker 600 is positioned ahead (i.e., in the direction of the welding Dw) of the laser welder 102 and the filler wire feed 104 (i.e., supplying the filler wire 116) is positioned on the same longitudinal axis as the laser welder 102 (e.g., similar to the arrangement of the laser welder 102 and the filler wire feed 104 in FIG. 1).

[00112] In various contemplated embodiments, different, specifically formulated chemical compositions of the filler wire are provided. For example, the chemical composition of the filler wire 116 contains Nickel (Ni) and at least one of: Carbon (C), Silicon (Si), Manganese (Mn), Phosphorous (P), Sulfur (S), Chromium (Cr), or Molybdenum (Mo). In one or more embodiments, the C content in the filler wire 116 is between 0% to 1.5% by weight, Si content in the filler wire 116 is between 0% to 3% by weight, Mn content in the filler wire 116 is between 0% to 2.5% by weight, P content in the filler wire 116 is between 0% to 0.05% by weight, S content in the filler wire 116 is between 0% to 0.03% by weight, Ni content in the filler wire 116 is between 6% to 22% by weight, Cr content in the filler wire 116 is between 16% to 30% by weight, and Mo content in the filler wire 116 is between 0% to 4% by weight. In aforementioned chemical composition, the remaining element in aforementioned composition of filler wire is Iron (Fe).

[00113] In one or more embodiments, the filler wire 116 material includes carburized wire. In an example, a carburized 4340 wire material includes 1.3% Carbon, 0.78% Chromium, 0.85% Manganese, 0.25% Molybdenum, 1.8% Nickel, 1.8% Silicon, 0.011% Phosphorus, and 0.014% Sulfur, the percentages being by weight. In some embodiments, the remaining element in aforementioned composition of filler wire is Iron (Fe).

[00114] In one or more embodiments, the filler wire 116 material is a stainless steel including e.g., Ni, Cr, or C. In an example, the 316L wire material includes 0.03% Carbon, 17% Chromium, 2% Manganese, 2.5% Molybdenum, 12.5% Nickel, 0.75% Silicon, 0.045% Phosphorus, and 0.03% Sulfur, the percentages being by weight. In aforementioned chemical composition, the remaining element in aforementioned composition of filler wire is Iron (Fe). [00115] According to the present disclosure, the filler wires including e.g., Ni, or C within the percentage by weight ranges, discussed herein, act as an austenite stabilizing element. As such, a ferrite microstructure formation is prevented in the welding zone at temperature ranging from 900°C to 950°C. Weld joints having austenitic microstructure or ferritic microstructure may cause cracking in the weld, weld having less tensile strength than the workpieces being welded, create granular weld, or other weld related issues.

[00116] Referring to Figures 10 and 11, according to one or more non-limiting embodiments, when welding with no filler (wire or powder) or when welding with filler wire(s) and/or powder(s) that do not have a composition discussed herein (e.g., without Ni, or C), a strength (e.g., ultimate tensile strength (UTS)) of the welded joint may be lower than 1200MPa. In addition, the welded joint fails (e.g., break, cracks, etc.) during cooling or when loaded. From spectroscopy (e.g., EDX) results, as shown in Figure 10, aluminum (lighter grey pixels in the image) is not well distributed or mixed in the weld and there is evidence of high concentration of aluminum areas (e.g., region 1001 in Figure 10). Figure 11 shows a microstructure of the weld seam. The microstructure also shows a substantial amount of Ferrite (lighter grey pixels in the image) mixed with Martensite. For example, Ferrite amounts to 10-70% by weight and Martensite may amount to 30-90% by weight. As a result, the welded joint is brittle or has lower strength compared to welded joint formed using filler wires discussed herein.

[00117] Consider welding two plates using an existing filler wire. For example, welding a combination of 1 ,2mm Boron steel with AlSi coating and 1 ,6mm Boron steel with AlSi coating with no filler wire (other than discussed herein). The resulting welded joint has a minimum UTS 800MPa, but less than 1200 MPa and a minimum Vickers hardness of HV250.

[00118] According to one or more embodiments the laser welder 102 provides a laser beam 120 that forms a generally round or oval spot with a highest beam intensity at the middle of the spot. However, according to various alternative embodiments, the laser welder 102 additionally and/or alternatively provides a shaped beam 120 that forms a shaped spot at the beam-to-metal interface (e.g., where the beam impacts the surface(s) of the sheet 106, sheet 108, and/or weld joint).

[00119] As shown in FIG. 10, according to one or more embodiments, the laser welder 102 for providing a shaped laser beam 120 comprises a laser generator 300 (e.g., YAG laser, CO2 laser) that generates a seed laser beam 302. The laser welder 102 includes one or more beam splitters 304 for splitting the seed laser beam 302 into a plurality of split beams 120a, a plurality of optical amplifiers 306 for amplifying respective ones of the split beams 120a, and a plurality of phase modulators 308 for modulating respective ones of the split beams 120a. The split beams 120a form a two dimensional array of coherent split beams 120a that recombine to form the coherent shaped beam 120. According to various embodiments, the one or more splitters (304) split the seed beam 302 into an array of split beams 120a comprising (1) at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 30, 40, 50, 60, 70, 80, 90, 100, 250, and/or 500 split beams 120a, (2) less than or equal to 1000, 500, 250, 100, 90, 80, 70, 60, 50, 40, 30, 20, and/or 10 split beams 120a, and/or (3) any number of split beams 120a between any two such upper and lower limits (e.g., between 3 and 1000, between 5 and 500, between 10 and 250). According to various embodiments, the array of split beams 120a may form various array patterns (e.g., a square or rectangular grid (e.g., 10x10 grid of 100 split beams), a hexagonal grid, a circle of split beams 120a), which may be related to or unrelated to an intended shape of the beam 120.

[00120] According to one or more embodiments, the use of parallel amplifiers 306 to amplify the split beams 120a formed from a single seed beam 302 formed by a single laser generator 300 helps to facilitate coherent recombination into the beam 120, which may increase the output power of the beam 120 to a greater extent than with in-series amplifiers. However, according to various alternative embodiments, a plurality of discrete laser generators 300 may be used to form respective beams 120a that are combined to form the beam 120.

[00121] As shown in FIG. 10, the laser welder 102 includes control electronics 310 that are operatively connected to the seed laser generator 300, amplifiers 306, and phase modulators 308 so that the control electronics 310 can individually control an intensity and/or phase of each beam 120a. For example, by individually varying the intensity and/or phase of different beams 120a, the electronics 310 can control the shape of the combined beam 120. As a result, as shown to the right in FIG. 10, the shaped beam 120 has an intensity that varies across its cross-section/spot (i.e., in a cross-section taken perpendicular to an axis/path 314 of the beam 120). According to various embodiments, the laser welder 102 can change the shape of the beam 120 without physically moving optical elements (e.g., lenses, mirrors, the laser generator 300) relative to each other. According to various embodiments, the laser welder 102 can change the shape of the beam 120 in micro seconds during a welding process so as to use different beam shapes at different times in the welding process. According to various embodiments, the laser welder 102 can sequence through different beam shapes over time during the welding process.

[00122] According to one or more embodiments, a sensor 312 (e.g., a camera) is used to sense the shape, intensity, and/or phase of the beams 120a and/or beam 100 and provide the sensed information back to the electronics 310 so that the electronics 310 can responsively adjust the beams 120a to better meet the desired beam 120 characteristics (e.g., via a feedback control loop).

[00123] According to one or more embodiments, a laser welder 102 utilizing a laser 300 and components 302, 304, 306, 308, 310, and/or 312 made by Civan can be used.

[00124] According to various embodiments, the combined shaped beam 120 passes through the focusing lens 152 (see FIG. 9). However, according to various alternative embodiments, the focus lens 152 is omitted or replaced with alternative optical and/or electrical focusing element(s) that focus the shaped beam 120. According to various embodiments, the electronics can shift a focal length of the beam 120 without moving parts (e.g., at 50 MHz).

[00125] As used herein, beam shape means the shape of the beam 120 as viewed in a cross section that is perpendicular to the beam 120’s path/axis 314. As used herein, a spot shape means the shape of the spot formed by the beam 120 impacting the sheet(s) and/or weld joint. [00126] FIGS. 11A-D illustrate beam and/or spot shapes formed by the beam 120 according to various embodiments. For example the beam/spot shape(s) formed by the beam 120 and laser welder 102 may include an infinity shaped beam/spot 320 (FIG. 11 A), a spiral shaped beam/spot 322 (FIG. I IB), a figure eight shaped beam/spot 324 (FIG. 11C), and/or a closed- loop shaped beam/spot 326 (FIG. 1 ID). The closed-loop shape 326 has ahigher intensity along the perimeter defining the closed-loop shape 326 than at some point radially inward of the perimeter (e.g., in the middle area within the loop). The closed-loop shape 326 may be circular (a circular ring) or non-circular (e.g., oval-shaped ring, egg-shaped ring, etc.), and may be comprise curves and/or angles (e.g., a square-shaped closed-loop, a polygonal closed-loop, a closed loop combining lines and/or curves). The figure eight shaped beam/spot 324 and/or infinity shaped beam/spot 324 may each comprise multiple adjacent (e.g., touching, overlapping, non-overlapping) closed-loop shapes such as the shape 326. However, as explained above, according to various embodiments, the laser welder 102 can generate any shape desired by individually altering different beams 120a. According to various embodiments, the beam/spot shape may additionally and/or alternatively have a shape in which the intensity is highest in the middle of the beam/spot, and trails off further and further from the middle (e.g., a circular or oval shape with a highest intensity in the middle of the circle or oval).

[00127] According to various embodiments, the beam shape and/or spot shape may have: (a) a lower intensity in the middle of the beam/spot than at a location disposed radially outward from the middle of the beam/spot, (b) a highest intensity at a location spaced from a middle of the beam/spot, and/or (c) a shape (e.g., a spiral) that is not mirror-symmetrical about any axis. [00128] According to one or more embodiments, and as shown in FIGS. 11A-D, along at least one line 330 passing through the beam, an intensity of the beam 120 increases then decreases then increases. According to various non-limiting embodiments, the line 330 passes through a middle of the beam 120. According to various alternative embodiments, the line 330 does not pass through a middle of the beam 120. According to various embodiments, the line 330 is perpendicular to the beam axis 314, which projects straight into the page in FIGS. 11 A- 1 ID. According to various embodiments, the line 330 forms an acute angle with the beam axis 314. According to various embodiments, along at least one line 330, the beam intensity increases, then decreases at least three times (e.g., as is the case for lines 330 shown in FIGS. UB and llC).

[00129] According to one or more embodiments, the laser welder 102 is configured to vary between different beam/spot shapes over time during a welding process. [00130] FIG. 12 illustrates an exemplary welded blank 110 in which coated sheets 106, 108 are joined at a weld joint 114. Structurally important regions of weld joint 114 include the weld joint surfaces 114a (circled in FIG. 12), the weld-joint-to-sheet interfaces 114b (emphasized by added curved lines), and pits or depressions 114c in the surfaces 114a. Stresses tend to concentrate in these regions 114a, 114b, 114c, so it is advantageous to avoid weakening the weld joint in these regions 114a, 114b, 114c.

[00131] Conventional laser welding laser beams have circular or oval shapes and focus laser energy toward the middle of the shape/spot. When welding aluminum-coated sheets 106 and 108 using such conventional laser beams, aluminum from the coating tends to become dispersed in the weld joint 114, including at the important regions 114a, 114b, 114c. Dispersion of aluminum into these regions 114a, 114b, 114c tends to weaken the weld joint 114. In contrast, by using shaped laser beams/spots and/or by changing the shape of the laser beam/spot over time, as explained above, it is believed that the welding process can tend to cause the aluminum from the coating to accumulate less in the regions 114a, 114b and/or 114c and more in less structurally significant regions of the weld joint 114 (e.g., in the middle of the weld joint 114 where stresses are lower).

[00132] As explained above, various embodiments utilize filler wire with a composition (e.g., via Ni and/or Cr additives) that binds with aluminum in the weld joint to reduce the extent to which aluminum might otherwise weaken the weld joint. Alternatively, the filler wire may minimize or even omit such additives. For example, according to one or more embodiments in which the shaped laser beam reduces an adverse impact of aluminum in the weld joint, a steel filler wire with little or no Ni or Cr may be used. In such embodiments, the steel filler wire may provide gap compensation (i.e., to fill the gap at the interface and weld joint) but not be specifically intended to metallurgically account for the presence of aluminum coating in the weld joint.

[00133] While various embodiments utilize filler wire, other embodiments alternatively use filler powder or no filler at all. For example, according to one or more embodiments, the use of shaped laser beam 120 facilitates the welding of aluminum-coated sheets 106, 108 to form strong welded blanks without using a filler (e.g., without using filler wire or filler powder). In such anon-filler embodiment, the weld joint consists of material from the sheets 106, 108 and unavoidable impurities.

[00134] In various embodiments, the aluminum coating is not removed from the sheets 106, 108 near the weld joint prior to welding the sheets. As explained above, the use of particular filler wire and/or a shaped laser beam can account for the dispersion of aluminum into the weld joint and limit any resulting weakening of the weld joint 114. However, according to one or more alternative embodiments, some of all of the aluminum coating can be removed from surfaces of the sheets 106, 108 near where the weld joint is to be formed. For example, as shown in FIGS. 13-14, the aluminum-silicon layer 106a, 108a of the sheets 106, 108 may be removed prior to welding, while leaving the intermetallic layer 106b, 108b of the sheets 106, 108 intact. According to one or more embodiments, a shaped and/or varying-shaped laser beam from the laser welder 102 (or a standalone ablation laser system that is separate from a welding laser) can be used to ablate the aluminum-silicon coating 106a, 108a from one or both surfaces of one or both sheets 106, 108 prior to welding the sheets 106, 108 together. In such an embodiments, as shown for example in FIG. 13 (before ablation) and FIG. 14 (after ablation), one laser ablation system 102 may be disposed above the sheets 106, 108 to ablate the aluminum-silicon coating 106a, 108a on the top surfaces of the sheets 106, 108 near the to-be- formed weld, and a second laser ablation system 102 may be disposed below the sheets 106, 108 to ablate the aluminum-silicon coating 106a, 108a from the bottom surfaces of the sheets 106, 108 near the to-be-formed weld. According to various embodiments, the ablation removes at least 50, 60, 70, 80, 90, 95, and/or 100% of the aluminum-silicon coating 106a, 108a on one or both surfaces of one or both sheets 106, 108. According to various embodiments, the intermetallic layer 106b, 108b remains intact after ablation. After ablation, the same laser system 102 or a different laser system 102 can be used to weld the ablated sheets 106, 108 together.

[00135] According to one or more embodiments, the same laser system 102 (including the same laser generator 300) is used to both ablate the aluminum-silicon coating 106a, 108a and then weld the ablated sheets 106, 108 together. In such an embodiment, the shape, focus, and/or intensity of the beam 120 can first be set so as to facilitate ablation, and then be altered by the electronics 310 and/or additional electric or optical elements so as to weld the sheets together. According to various embodiments, the ablation and welding can occur during a single pass of the system 102 by the interface 112 between the sheets 106, 108, for example by rapidly switching between an ablation beam 120 and a welding beam 120 as the beam 120 moves along the interface 112. Alternatively, the system 102 may first carry out the ablation along the entire interface 112 during a first pass over the full length of the interface 112, and then weld the sheets 106, 108 together during a second pass over the length of the interface 112 so as to form the weld joint 114. [00136] One or more non-limiting embodiments provide good mixing of the liquid metal within the weld pool during the laser welding process, which may advantageously result in a more homogeneous mixture of elements in the weld pool and resulting weld joint 114. This may also provide a more homogenous mixture of microstructure(s) in the resulting weld joint 114. This homogeneity may, in turn, provide a stronger weld joint, either before and/or after heat treatment of the welded blank 110.

[00137] For example, the differential intensity of different portions of the laser beam 120 may result in differential temperatures within different portions of the weld pool, which may promote temperature-differential-induced mixing. V arying the shape of the beam 120 over time may similarly result in different temperatures within different portions of the weld pool and thereby promote better mixing.

[00138] Although the present patent application has been described in detail for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that the present patent application is not limited to the disclosed embodiments, but, on the contrary, is intended to cover modifications and equivalent arrangements that are within the spirit and scope of the appended claims. In addition, it is to be understood that the present patent application contemplates that, to the extent possible, one or more features of any embodiment can be combined with one or more features of any other embodiment.

Claims

What is claimed is:

1. A method for laser welding a first steel workpiece to a second steel workpiece to form a welded assembly, the method comprising: positioning the first and second workpieces to form an interface therebetween, using a laser beam to melt a portion of at least one of the workpieces at the interface, and resolidifying melted metal at the interface to form a weld joint between the first and second workpieces, wherein, during at least a part of said using of said laser beam, along at least one line passing through the laser beam, an intensity of the laser beam increases, then decreases, then increases.

2. The method of claim 1, wherein, during at least a part of said using of said laser beam, an intensity of the laser beam at a middle of the beam is lower than an intensity of the laser beam at a different portion of the beam.

3. The method of claim 1, further comprising changing a shape of the laser beam from a first shape to a second shape during said using of the laser bean to melt a portion of at least one of the work pieces.

4. The method of claim 3, wherein the first shape and second shape each originate from the same laser generator.

5. The method of claim 3, wherein said changing occurs without physical movement of any optical element relative to any other optical element.

6. The method of claim 1, wherein during at least a part of said using of said laser beam, and as viewed in a cross-section that is perpendicular to a path of the laser beam, a shape of the beam includes a closed-loop shape.

7. The method of claim 1, wherein during at least a part of said using of said laser beam, and as viewed in a cross-section that is perpendicular to a path of the laser beam, a shape of the beam includes a figure eight shape.

8. The method of claim 1, wherein during at least a part of said using of said laser beam, and as viewed in a cross-section that is perpendicular to a path of the laser beam, a shape of the beam includes a spiral shape.

9. The method of claim 1, wherein the first and second work pieces each comprise a steel material with an aluminum based coating thereon.

10. The method of claim 9, further comprising feeding a filler wire to the interface, wherein said laser beam melts a portion of the filler wire.

11. The method of claim 10, wherein the filler wire comprises a composition that includes nickel and chromium, and wherein the method further comprises binding the filler wire with aluminum in the aluminum based coating.

12. The method of claim 9, wherein the weld joint is formed between the first and second workpieces without previously removing the aluminum based coatings from the first or second workpieces.

13. The method of claim 9, further comprising using a laser beam to remove at least a portion of the aluminum based coating from portions of the first and second work pieces, respectively, at or adjacent to where the weld joint will be formed.

14. The method of claim 13, wherein the laser beam used for said removing of at least a portion of the aluminum originates from the same laser generator as the laser beam used for said melting of the portion of at least one of the workpieces.

15. The method of claim 14, wherein the laser beam used for said removing of at least a portion of the aluminum has a different laser beam shape than the laser beam used for said melting of the portion of at least one of the workpieces.

16. The method of claim 9, wherein the weld joint is formed without the use of a filler.

17. A laser welder configured to weld a first steel workpiece to a second steel workpiece an interface between the first and second steel workpieces to form a welded assembly, wherein the laser welder is configured to generate a welding laser beam such that along at least one line passing through the laser beam, an intensity of the laser beam increases, then decreases, then increases.

18. The welder of claim 17, further comprising: a laser generator configured to generate a seed laser beam; at least one beam splitter positioned and configured to split the seed laser beam into a plurality of split laser beams; a plurality of optical amplifiers positioned and configured to amplify respective ones of the plurality of split laser beams; and a plurality of phase modulators positioned and configured to modulate a phase of respective ones of the plurality of split laser beams.

19. The welder of claim 18, further comprising an electronics controller operatively connected to the plurality of optical amplifiers and the plurality of phase modulators, wherein the electronics controller is configured to control the optical amplifiers and phase modulators so as to control a shape of a beam formed by the combination of split beams

20. The welder of claim 17, wherein the laser welder is configured to change a shape of the laser beam from a first shape to a second shape while welding the first and second workpieces together.

21. The welder of claim 20, wherein the laser welder comprises a laser generator capable of forming the first shape and second shape.

22. The welder of claim 20, wherein the laser welder is configured to change a shape of the laser beam without physical movement of any optical element relative to any other optical element.

23. The welder of claim 17, wherein, as viewed in a cross-section that is perpendicular to a path of the laser beam, a shape of the beam includes a closed-loop shape.

24. The welder of claim 17, wherein as viewed in a cross-section that is perpendicular to a path of the laser beam, a shape of the beam includes a figure eight shape.

25. The welder of claim 17, wherein as viewed in a cross-section that is perpendicular to a path of the laser beam, a shape of the beam includes a spiral shape.

26. The welder of claim 17, wherein the laser welder is configured to generate and use a laser beam to remove at least a portion of an aluminum based coating from portions of the first and second work pieces, respectively, at or adjacent to where the weld joint will be formed.

27. The welder of claim 26, wherein the laser welder comprises a laser generator that is configured to generate a laser beam used for said removing of at least a portion of the aluminum, wherein said laser generator is configured to generate a laser beam used for melting at least a portion of at least one of the workpieces during a welding process.

28. The welder of claim 17, further comprising a filler wire feed configured to feed a filler wire to the interface when the first and second workpieces are being welded to each other to form the welded assembly.

29. The welder of claim 28, wherein the filler wire comprises a composition that includes nickel and chromium, and wherein the filler wire is configured to bind with aluminum in an aluminum based coating of the first and second workpieces so as to minimize formation of brittle intermetafiics due to mixing of the aluminum in the aluminum based coating with the iron/steel material in the weld joint.