Abstract: A spot welding monitoring method is configured to monitor a state of spot welding that holds a work including metal plates stacked on each other, between electrodes in a pair, and supplies electricity between electrodes. The spot welding monitoring method includes: by a converter disposed in a vicinity of a weld zone of the work, detecting a change in magnetic flux density of a magnetic field generated around the weld zone by the supplying of the electricity between electrodes, and converting the change in the magnetic flux density into a current; and calculating three-dimensional data on a melting zone of the work, based on a temporal change in a value of the current.

Abstract: A pierce metal includes a head and a shaft. The shaft is configured to penetrate through an aluminum die-cast member with a protruded tip surface of the shaft being exposed from the aluminum die-cast member, and an outer peripheral surface of the shaft is configured to come into contact with a through-hole of the aluminum die-cast member, upon joining the aluminum die-cast member and the iron-based member together. The head and the iron-based member in contact with the protruded tip surface are configured to be held under pressure and applied with electric power by weld electrodes to perform spot welding of the protruded tip surface and the iron-based member, upon joining the aluminum die-cast member and the iron-based member together. The outer peripheral surface includes a non-contact part configured to come into non-contact with the through-hole in a state in which the shaft is penetrated through the aluminum die-cast member.

Abstract: A pierce metal includes a head and a shaft. The shaft is configured to penetrate through an aluminum die-cast member with a protruded tip surface of the shaft being exposed from the aluminum die-cast member, and an outer peripheral surface of the shaft is configured to come into contact with a through-hole of the aluminum die-cast member, upon joining the aluminum die-cast member and the iron-based member together. The head and the iron-based member in contact with the protruded tip surface are configured to be held under pressure and applied with electric power by weld electrodes to perform spot welding of the protruded tip surface and the iron-based member, upon joining the aluminum die-cast member and the iron-based member together. The outer peripheral surface includes a non-contact part configured to come into non-contact with the through-hole in a state in which the shaft is penetrated through the aluminum die-cast member.