External heat assisted welding of dissimilar metal workpieces

A method of joining an aluminum workpiece and a steel workpiece, the method comprising:

• providing a workpiece stack-up that includes a first side presented by an aluminum workpiece surface and a second side presented by a steel workpiece surface, the workpiece stack-up comprising an aluminum workpiece and an adjacent overlapping steel workpiece, wherein a faying surface of the aluminum workpiece confronts a faying surface of the steel workpiece to provide a faying interface;
• pressing a weld face of a first welding electrode and a weld face of a second welding electrode against the first side and the second side of the workpiece stack-up, respectively, while a temperature of the first welding electrode is at an elevated temperature that does not exceed a melting point of the aluminum workpiece, the first weld face and the second weld face being pressed against their respective first and second sides of the workpiece stack-up in facial alignment with one another at a weld site
• passing an electrical current between the weld face of the first welding electrode and the weld face of the second welding electrode to create a molten aluminum weld pool within the aluminum workpiece, the molten aluminum weld pool wetting the faying surface of the steel workpiece;
• ceasing passage of the electrical current between the weld face of the first welding electrode and the weld face of the second welding electrode to allow the molten aluminum weld pool to solidify into a weld joint;
• and
• controlling the temperature of the first welding electrode after passage of the electrical current between the weld face of the first welding electrode and the weld face of the second welding electrode has ceased, and with the first welding electrode still in contact with the aluminum workpiece, to maintain the temperature of the first welding electrode at a holding temperature that prevents full solidification of the molten aluminum weld pool into the weld joint until a temperature of the steel workpiece at the weld site cools to below the melting point of the aluminum workpiece.

A method of joining an aluminum workpiece and a steel workpiece, the method comprising:

• providing a workpiece stack-up that includes a first side presented by an aluminum workpiece surface and a second side presented by a steel workpiece surface, the workpiece stack-up comprising an aluminum workpiece and an adjacent overlapping steel workpiece, wherein a faying surface of the aluminum workpiece confronts a faying surface of the steel workpiece to provide a faying interface;
• pressing a weld face of first welding electrode and a weld face of a second welding electrode against the first side and the second side of the workpiece stack-up, respectively, with the first weld face and the second weld face being pressed against their respective first and second sides of the workpiece stack-up in facial alignment with one another at a weld site
• passing an electrical current between the weld face of the first welding electrode and the weld face of the second welding electrode to create a molten aluminum weld pool within the aluminum workpiece, the molten aluminum weld pool wetting the faying surface of the steel workpiece;
• ceasing passage of the electrical current between the weld face of the first welding electrode and the weld face of the second welding electrode to allow the molten aluminum weld pool to solidify into a weld joint;
• and
• controlling a temperature of the first welding electrode after passage of the electrical current between the weld face of the first welding electrode and the weld face of the second welding electrode has ceased, and with the first welding electrode still in contact with the aluminum workpiece, to maintain a temperature of the first welding electrode at a holding temperature that prevents full solidification of the molten aluminum weld pool into the weld joint until a temperature of the steel workpiece at the weld site cools to below a melting point of the aluminum workpiece.