Patent Application
20200055139
The present disclosure relates to a method to manufacture an electrical resistance weld between three or more sheet metal layers. More specifically, this disclosure relates to forming high quality weld nuggets between at least three sheet metal layers.
Resistance welding processes are pressure welding processes in which heavy current is passed for a short time through the area of interface of metals to be joined. Filler material is traditionally not implemented as part of a resistance welding process. Heat is generated in localized area which is enough to heat the metal to a sufficient temperature, so that the parts can be joined with the application of pressure (or force). Pressure (Le., force/area) is applied through the electrodes.
The process may employ an example current of the order of 10,000 Amps, 1 V and 0.5 seconds. Force is normally applied before, during and after the flow of current to avoid arcing between the surfaces and to forge the weld metal during post heating. An example pressure may vary from 30 to 150 Nmm−2 depending upon material to be welded and other welding conditions. For good quality welds, these parameters may be properly selected which shall depend mainly on material of components, their thicknesses, type and size of electrodes,
Current automotive vehicle manufacturing operations include, for example, the joining of two sheet metal layers by resistance welding. Vehicle body panels such as doors, hoods, deck lids and liftgates are often assembled by joining inner and outer panels stamped from sheet metal of suitable metal alloys. Ferrous or aluminum alloys are often used. The thickness of each sheet metal layer may vary from less than one millimeter to more than four millimeters.
Electrical resistance spot welding is often used to join such inner and outer panels or other metal parts. For example, an edge of an outer pan& sheet may be folded over an adjacent edge of an inner pan& sheet positioned in an assembly of the panels in which the hems are at the periphery of the sheets. The panel assembly is positioned for welding in areas removed from the hem joint. Axially aligned and opposing electrodes are pressed toward each other against opposite sides of the panel assembly. A momentary welding current is passed between the electrodes through the layers of metal to form a spot weld. The spot weld is characterized by a momentarily fused pool of metal and a re-solidified weld nugget at the interface of the contacting sheets. The electrodes are retracted and moved to another weld site.
In resistance spot welding, two sheets of metal are generally held between electrodes through which welding current is supplied for a definite time and also force is exerted on work pieces. The welding cycle starts with the upper electrode moving and contacting the work pieces resting on the lower electrode which is usually stationary. The work pieces are held under pressure and only then heavy current is passed between the electrodes for preset time. The area of metals in contact are rapidly raised to welding temperature, due to the flow of current through the contacting surfaces of work pieces. The pressure between electrodes, squeezes the hot metal together thus completing the weld. The weld nugget formed is allowed to cool under pressure and then pressure is released. This total cycle is known as resistance spot welding cycle. However, when three work pieces 112, 114, 116 must be welded together and at least one of the work pieces 112 has a reduced thickness relative to the others 114, 116, weld strength is compromised due to uneven heat distribution during the welding process which may result in an undersized weld 118 at the interface between a thin outer sheet 112 and the adjacent thicker metal sheet 114.
Referring now to
Therefore, it is desirable to strengthen a resistance welded joint between three or more sheet metal layers which may have varying thicknesses.
The present disclosure provides a method of manufacturing an electrical resistance weld in an assembly of at least three overlying sheet metal layers. The method includes the steps of: (1) providing a first sheet metal layer having a first thickness; (2) providing a second sheet metal layer having a second thickness onto a first sheet metal layer; (3) providing a filler material on the second sheet metal layer; (4) providing a third sheet metal layer having a third thickness onto the filler material and the second sheet metal layer wherein the third thickness is less than each of the first and the second thicknesses; (5) pressing a pair of welding electrodes against a pair of opposing outer surfaces with the filler material disposed therebetween; and (6) passing an electric current between the pair of electrodes through the filler material and the first, second, and third sheet metal layers to form a weld nugget which penetrates into at least two sheet metal layers.
It is understood that the foregoing method may further comprise the steps of (7) bonding the third sheet metal layer to the second sheet metal layer via a brazed joint formed by the melted filler material; and (8) bonding the second sheet metal layer to the first sheet metal layer via a resistance spot weld formed by the weld nugget. Alternatively, the foregoing method may further comprise the steps of (7) heating the filler material together with the first, second, and third sheet metal layers so that at least a portion of the first, second, and third sheet metal layers melt together with the filler material at the weld site to form a cohesive weld nugget. Regardless of which of the foregoing methods are used, it is understood that the filler material is configured to melt at a lower temperature relative to the each of the first, second and third sheet metal layers.
In the above method, it is understood that a weld site is defined by the region of the first, second and third sheet metal layers between the pair of welding electrodes and the filler material is disposed on the second sheet metal layer at the weld site. The filler material may optionally, but not necessarily, be a copper alloy or an aluminum alloy, and the filler material may also optionally, but not necessarily have a porous structure. The filler material and the first, second and third sheet metal layers form a three-sheet assembly which is held between the pair of electrodes for a definite time period wherein the pair of electrodes exerts force on the three-sheet assembly and transfers a current through the three-sheet assembly. Under this scenario, the weld nugget becomes a spot weld upon cooling. Alternatively, under another non-limiting example scenario, each electrode in the pair of electrodes may be a roller which is configured to move relative to the three-sheet assembly at the weld site such that the weld nugget becomes part of a seam weld upon cooling.
It is also understood that the above method may further include an optional additional fourth step may of providing a fourth sheet metal layer and a second filler material which may optionally, but not necessarily, be disposed between the fourth sheet metal layer and an adjacent layer. The first, second and third sheet metal layers may also, but not necessarily each be formed from steel or aluminum alloy.
In yet another embodiment of the present disclosure, a method of forming an electrical resistance weld in an assembly of overlying sheet metal layers includes the steps of: (1) providing a plurality of sheet metal layers; (2) providing a filler material between at least two sheet metal layers in the plurality of sheet metal layers to form a multi-layer assembly; (3) pressing a pair of welding electrodes against a pair of opposing outer surfaces of the multi-layer assembly; and (4) passing an electric current between the pair of electrodes through the multi-layer assembly to form a weld nugget which penetrates each metal layer in the plurality of sheet metal layers.
It is understood that the foregoing method may further comprise the step of: (5) heating the filler material via the electric current so as to melt the filler material to create a brazed joint from the melted filler material. It is understood that under this arrangement a portion of the multi-layer assembly is bonded together via the brazed joint while another portion of the multi-layer assembly is bonded together via the weld nugget. Alternatively, the foregoing method may further comprise the step of: (5) heating the filler material via the electric current so as to melt the filler material together with at least a portion of each of the plurality of sheet metal layers disposed between the pair of welding electrodes so as form a cohesive weld nugget which penetrates each sheet metal layer in the plurality of sheet metal layers.
In the foregoing example method, a weld site may be defined by the region of the plurality of the sheet metal layers between the pair of welding electrodes and the filler material may be disposed at the weld site. Moreover, the filler material may optionally, but not necessarily, be either a copper alloy or an aluminum alloy. The foregoing example method may further include the step of cooling the weld nugget to form a spot weld. Alternatively, the foregoing example method may further include the step of moving the pair of welding electrodes relative to the multi-layer assembly to form an adjacent overlapping weld nugget which overlaps the weld nugget wherein the pair of welding electrodes are rollers. Under this latter alternative, the method may further include the step of cooling the adjacent overlapping weld nugget and the weld nugget to form a seam weld.
The present disclosure also provides for a resistance welded multi-sheet assembly which includes a plurality of sheet metal layers, a filler material and a weld configured to join the plurality of sheet metal layers. The plurality of sheet metal layers includes an interior sheet metal layer disposed between two exterior sheet metal layers. The filler material may be disposed between at least two sheet metal layers in the plurality of sheet metal layers. The weld extends through the interior metal layer and into each exterior metal layer by at least 10% of the thickness of exterior metal layer. Similarly, it is also understood that the filler material of the foregoing multi-sheet assembly may, but not necessarily, be either a copper alloy or an aluminum alloy.
The present disclosure and its particular features and advantages will become more apparent from the following detailed description considered with reference to the accompanying drawings.
These and other features and advantages of the present disclosure will be apparent from the following detailed description, best mode, claims, and accompanying drawings in which:
Like reference numerals refer to like parts throughout the description of several views of the drawings.
Reference will now be made in detail to presently preferred compositions, embodiments and methods of the present disclosure, which constitute the best modes of practicing the present disclosure presently known to the inventors. The figures are not necessarily to scale. However, it is to be understood that the disclosed embodiments are merely exemplary of the present disclosure that may be embodied in various and alternative forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for any aspect of the present disclosure and/or as a representative basis for teaching one skilled in the art to variously employ the present disclosure.
Except in the examples, or where otherwise expressly indicated, all numerical quantities in this description indicating amounts of material or conditions of reaction and/or use are to be understood as modified by the word “about” in describing the broadest scope of the present disclosure. Practice within the numerical limits stated is generally preferred, Also, unless expressly stated to the contrary: percent, “parts of,” and ratio values are by weight; the description of a group or class of materials as suitable or preferred for a given purpose in connection with the present disclosure implies that mixtures of any two or more of the members of the group or class are equally suitable or preferred; the first definition of an acronym or other abbreviation applies to all subsequent uses herein of the same abbreviation and applies mutatis mutandis to normal grammatical variations of the initially defined abbreviation; and, unless expressly stated to the contrary, measurement of a property is determined by the same technique as previously or later referenced for the same property.
It is also to be understood that this present disclosure is not limited to the specific embodiments and methods described below, as specific components and/or conditions may, of course, vary. Furthermore, the terminology used herein is used only for the purpose of describing particular embodiments of the present disclosure and is not intended to be limiting in any way.
It must also be noted that, as used in the specification and the appended claims, the singular form “a,” “an,” and “the” comprise plural referents unless the context clearly indicates otherwise. For example, reference to a component in the singular is intended to comprise a plurality of components.
The term “comprising” is synonymous with “including,” “having,” “containing,” or “characterized by.” These terms are inclusive and open-ended and do not exclude additional, un-recited elements or method steps.
The phrase “consisting of” excludes any element, step, or ingredient not specified in the claim. When this phrase appears in a clause of the lifter body 14 of a claim, rather than immediately following the preamble, it limits only the element set forth in that clause; other elements are not excluded from the claim as a whole.
The phrase “consisting essentially of” limits the scope of a claim to the specified materials or steps, plus those that do not materially affect the basic and novel characteristic(s) of the claimed subject matter.
The terms “comprising”, “consisting of”, and “consisting essentially of” can be alternatively used. Where one of these three terms is used, the presently disclosed and claimed subject matter can include the use of either of the other two terms.
The terms “upper” and “lower” may be used with respect to regions of a single component and are intended to broadly indicate regions relative to each other wherein the “upper” region and “lower” region together form a single component. The terms should not be construed to solely refer to vertical distance/height.
Throughout this application, where publications are referenced, the disclosures of these publications in their entireties are hereby incorporated by reference into this application to more fully describe the state of the art to which this present disclosure pertains.
The following detailed description is merely exemplary in nature and is not intended to limit the present disclosure or the application and uses of the present disclosure. Furthermore, there is no intention to be bound by any theory presented in the preceding background or the following detailed description.
The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary, or the following detailed description.
Referring now to
It is understood that the foregoing method may further comprise the steps of (7) bonding the third sheet metal layer 12 to the second sheet metal layer 14 via a brazed joint 25 formed by the melted filler material; and (8) bonding the second sheet metal layer 14 to the first sheet metal layer 16 via a resistance spot weld 21 formed by the weld nugget. Alternatively, the foregoing method may further comprise the steps of (7) heating the filler material together with the first, second, and third sheet metal layers so that at least a portion of the first, second, and third sheet metal layers melt together with the filler material at the weld site to form a cohesive weld nugget 18. Regardless of which of the foregoing methods are used, it is understood that the filler material is configured to melt at a lower temperature relative to the each of the first, second and third sheet metal layers.
It is understood that cohesive weld nugget 18 may, but not necessarily include at least a portion of the filler material 30 initially positioned at interface 26 (where filler material is provided) and extends beyond interface 24 such that the filler material 30 melts together with the first, second and third layers when current is applied. It is understood that traditional ratio of the first thickness 52 to the third thickness may, but not necessarily, generally not exceed a 1 to 2 ratio.
In the above method and as shown in
When manufacturing a seam weld 86 according to the present disclosure, three (or more) metal sheets 12, 14, 16, 70 (see
Referring now to
In yet another embodiment of the present disclosure and as also demonstrated by both
In the foregoing example method, a weld site 62 may be defined by the region of the plurality of the sheet metal layers 90 between the pair of welding electrodes 28, 29 and the filler material 30 may be disposed at the weld site 62. Moreover, the filler material 30 may optionally, but not necessarily, be either a copper alloy 64 or an aluminum alloy 66. The foregoing example method may further include the step of cooling the cohesive weld nugget 18 to form a spot weld 84 which penetrates each sheet metal layer. Alternatively, the foregoing example method may further include the step of moving the pair of welding electrodes 28, 29 relative to the multi-layer assembly 91 to form an adjacent (and optionally overlapping) cohesive weld nugget 18′ (shown in phantom in
With reference now to
Referring now to
While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the disclosure in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the exemplary embodiment or exemplary embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope of the disclosure as set forth in the appended claims and the legal equivalents thereof.
