An aspect of the present disclosure is to provide a method for manufacturing a welded structure capable of effectively suppressing welding LME cracks generated during spot welding of a zinc plated steel sheet having ultra-high strength, and a welded structure manufactured using the same.

A joining device includes: a pair of pressing members disposed to face each other to sandwich joining target members from both sides in a stacking direction of the joining target members and configured to press the joining target members; and power supply members disposed on one or both sides in the stacking direction of the joining target members to sandwich a pressing target portion of the joining target members by the pressing members and configured to come into contact with and supply power to the joining target members. The power supply members are provided at positions not overlapping the pressing members in the stacking direction of the joining target members, and the pressing members press the joining target members while the power supply members supply power to the joining target members, thereby generating resistance heat in the pressing target portion and joining the joining target members.

Disclosed herein are compositions, methods, and systems for resistance spot welding or brazing an aluminum member to a steel member using a chromium layer disposed between the aluminum member and the steel member.

A cold-rolled and heat-treated steel sheet having a microstructure consisting of, in surface fraction: between 10% and 30% of retained austenite, the retained austenite being present as films having an aspect ratio of at least 3 and as Martensite Austenite islands, less than 8% of the Martensite Austenite islands having a size above 0.5 μm, at most 1% of fresh martensite, at most 50% of tempered martensite, and recovered martensite containing precipitates of at least one element chosen among niobium, titanium and vanadium. A method for manufacturing the cold-rolled and heat-treated steel sheet is also described.

A method of resistance spot welding a workpiece stack-up that includes a steel workpiece and an aluminum workpiece includes adhering an aluminum patch to faying surface of a steel workpiece, positioning an aluminum workpiece over the aluminum patch and the steel workpiece to assemble a workpiece stack-up, passing an electric current through the workpiece stack-up to create a molten aluminum weld pool, and terminating passage of the electric current to solidify the molten aluminum weld pool into a weld joint that bonds the steel and aluminum workpieces together through the aluminum patch. A workpiece stack-up having a weld joint that bonds an aluminum workpiece and a steel workpiece together through an aluminum patch is also disclosed. The weld joint establishes a bonding interface with the faying surface of the steel workpiece, and the aluminum patch is adhered to the faying surface of the steel workpiece around the weld joint.

A transition structure includes a metallic portion, a fiber portion including a plurality of tows embedded within the metallic portion and extending out from the metallic portion forming a fabric, and a binding material forming a matrix surrounding the fiber portion embedded within the metallic portion. The fiber portion may be attached to or form part of a composite vehicle component. The transition structure may join a metallic component and a composite component. The transition structure may be manufactured by creating first channels within a layer of a metallic substrate, inserting fiber tows into the first channels, placing a first metallic layer over the metallic substrate and the fiber tows, consolidating the metallic layer to the metallic substrate, and binding the fiber tows within a resin. Prior to binding, additional layers of channels and fiber tows may be consolidated onto the first metallic layer.

A method for resistance spot welding comprising the following successive steps: —providing at least two steel sheets with thickness (th) comprised between 0.5 and 3 mm, at least one of the sheets being a zinc or zinc-alloy coated steel sheet (A) with a tensile strength (TS) higher than 800 MPa and a total elongation (TEL) such as (TS)×(TEL)>14000 MPa %, wherein the composition of the steel substrate of (A) contains, in weight: 0.05%≤C≤0.4%, 0.3%≤Mn≤8%, 0.010%≤Al≤3%, 0.010%≤Si≤2.09%, with 0.5%≤(Si+Al)≤3.5%, 0.001%≤Cr≤1.0%, 0.001%≤Mo≤0.5% and optionally: 0.005%≤Nb≤0.1%, 0.005%≤V≤0.2%, 0.005%≤Ti≤0.1%, 0.0003%≤B≤0.005%, 0.001%≤Ni≤1.0%, the remainder being Fe and unavoidable impurities, —performing resistance spot welding of the at least two steel sheets for producing a weld with an indentation depth (IDepth) on the surface of said steel sheet (A) such as: 100 μm≤(IDepth)≤18.68 (Zn.sub.sol)−55.1, wherein (IDepth) is in micrometers and wherein Zn.sub.sol is the solubility of Zn in the steel of sheet (A) at 750° C., in weight %.

Proposed is a resistance spot welding method to join parts to be welded which are a plurality of overlapping metal sheets, including: dividing a current pattern into two or more steps for welding; before actual welding, performing test welding; and subsequently, as actual welding, performing adaptive control welding, in which the two or more steps for welding include a step of securing a current path between the sheets directly below the electrodes and a subsequent step of forming a nugget having a predetermined diameter, and a welding interval time is provided between these steps. This method thus yields a good nugget without causing splashing even under special welding conditions.

Provided is a method of manufacturing a joined member that is manufactured by applying resistance welding to a workpiece. The workpiece is provided with plating layers on sides to be in contact with electrodes. In a state in which a first electrode is in contact with a first area in a first plate material that is curved along a contour of a leading end of the first electrode and in which a second electrode is in contact with a second area in a second plate material that is curved along a contour of a leading end of the second electrode, energization between the first electrode and the second electrode is started to form a nugget.

A joining device includes: a first circuit in which a primary-side winding of a first transformer and a first capacitor are connected; a second circuit in which a primary-side winding of a second transformer and a second capacitor are connected; an electrode connected to secondary-side winding of the first transformer and secondary-side winding of the second transformer; and a charge switch configured to switch between energization/de-energization of the first and second capacitors from a power supply without the transformers being interposed. The first circuit has a first discharge switch and the second circuit has a second discharge switch. A method for manufacturing a joined object includes, by using the joining device, supplying an object to be joined to be sandwiched by the electrode; causing a current to flow through the electrode that sandwiches the object to be joined to join the object to be joined.