A method for evaluating a welded between a first component and a second component comprises the steps of: bringing a first electrical pole into contact with the first component and bringing a second electrical pole into contact with the second component with the welded joint in between the first and the second pole; applying a first electrical quantity to the welded joint such that an electrical current (i) flows through the welded joint; measuring a second electrical quantity at the first and the second pole; comparing a measured value (.sub.F; U.sub.F) of the second electrical quantity with a reference value (.sub.0; U.sub.0); and evaluating the welded joint on the basis of the comparison step.

An electrode for the projection welding of a weld nut to a workpiece has an electrode welding head with parts including a replaceable welding interface disc fitted therein. The electrode can be disassembled so that the conductive electrode interface within the welding head may be replaced when it becomes worn.

A device for holding a stud with a radially flange and an axial shank. The holding device comprising a collet including a clamping section and a hollow insertion section defining an insertion axis such that the stud can be inserted via the insertion section to the clamping section. The holding device further comprising a tubular securing sleeve located radially inward of and concentric with the insertion section. A clearance is defined between a bottom end of the securing sleeve and a top end of the clamping section and is adapted to releasably receive the stud flange. A first air flow channel in a first direction is adapted to blow feed the stud into the collet; and a second airflow channel oriented in a second different direction is adapted to maintain the stud shank substantially in line with the insertion axis.

A welding auxiliary joining part is disclosed in the shape of a stud having a head, a shank and a tip. The welding auxiliary joining part is driven in by means of a mechanical-thermal setting method into a component of non- or poorly weldable material. During the driving in, a welding head is created due to mechanical deformation so that the component may be connected subsequently via the welding auxiliary joining part to a further component of weldable material by means of welding.

An apparatus and method for fastening layers of non-ferrous alloys, like aluminum, magnesium and copper utilizes a steel fastener and a spot welding machine. The fastener and metals are stacked and the heat from the welder's electric current softens the lower melting point aluminum allowing the fastener to penetrate the aluminum. A weld zone between the fastener and the various layers creates an internal weld. The fastener has a rough shaft that is coated by the molten weld zone and is hard to withdraw on solidification. Layers of non-conductive materials like plastics and ceramics may also be affixed to a conductive layer using a fastener made from a compatible material that extends through a pilot hole and welds to or penetrates a conductive layer. The fastener may have projections that initially reduce contact area with the stack.

A joining head for the joining of a joining element to a workpiece, wherein the joining head) has a fluid cylinder that acts in an axial direction for actuating a loading pin, and the fluid cylinder has a cross-sectional area and defines a dimension of the joining head in a predetermined radial direction, and the cross-sectional area of the fluid cylinder deviates from a circular shape in order to reduce the dimension of the joining head in the predetermined radial direction.

A setting welding device is set forth for setting stud-like auxiliary joining parts in a plurality of layers of material and subjecting them to a mechanical-thermoforming process on a second layer of material and connecting them to said second layer by way of a welding operation. For this purpose, the punch is used to apply to the welding auxiliary joining part mechanical and thermal loads that follow prescribed characteristic force and current curves. Furthermore, a corresponding connecting method that can be realized with the aid of the setting welding device is also disclosed.

An apparatus and method for fastening layers of non-ferrous alloys, like aluminum, magnesium and copper utilizes a steel fastener and a spot welding machine. The fastener and metals are stacked and the heat from the welder's electric current softens the lower melting point aluminum allowing the fastener to penetrate the aluminum. A weld zone between the fastener and the various layers creates an internal weld. The fastener has a rough shaft that is coated by the molten weld zone and is hard to withdraw on solidification. Layers of non-conductive materials like plastics and ceramics may also be affixed to a conductive layer using a fastener made from a compatible material that extends through a pilot hole and welds to or penetrates a conductive layer. The fastener may have projections that initially reduce contact area with the stack.

A joining-member welding unit includes a first member made of metal, a second member overlapped with one surface of the first member, a joining member made of the same kind of metal as the first member, and a welder. The second member has a through-hole defined by an inner wall surface thereof. The inner wall surface and the one surface define a recessed portion. The joining member includes a large-diameter plate portion having an outer diameter larger than a diameter of the through-hole and a thickness smaller than the diameter of the through-hole, and a protruding portion protruding from the large-diameter plate portion and to be inserted into the through-hole. The welder includes a holding portion that holds the joining member. The welder applies an electric current to the joining member to melt the protruding portion such that the first member and the second member are joined together.

A setting welding device is set forth for setting stud-like auxiliary joining parts in a plurality of layers of material and subjecting them to a mechanical-thermoforming process on a second layer of material and connecting them to said second layer by way of a welding operation. For this purpose, the punch is used to apply to the welding auxiliary joining part mechanical and thermal loads that follow prescribed characteristic force and current curves. Furthermore, a corresponding connecting method that can be realized with the aid of the setting welding device is also disclosed.