Resistance joining, typically resistance welding, uses a strong electric current to join metals quickly and without the need for filler materials. The materials’ natural electrical resistance creates intense heat when the current is passed through the parts to be joined. This heat creates fusion, providing strong, filler-less bonds that are widely used in sectors such as automotive, appliance and electronics manufacturing. Frequently used to join thin sheet metals, resistance processes include seam, spot and projection welding, and are often automated for increased efficiencies. Resistance welding is one of the most widely used and well-established methods of joining used by industry.
How Resistance Joining Works
There are number of common steps that are used in resistance joining procedures, as follows:
- Clamping: The metal parts to be joined are clamped in place
- Current Flow: An electrical current is passed through copper electrodes and to the workpieces
- Heating: The electrical resistance at the point of contact between the metals generates significant heat
- Fusion: This heat softens or melts the parts as pressure forces the workpieces to fuse together and join as they cool
Key Types, Advantages, and Applications
Resistance joining is easily automated, which makes it extremely efficient, offering high production rates. The process produces strong and reliable joints without the need for extra material, flux, or shielding gas.
These advantages have led resistance welding to become a mainstay of the automotive industry, where spot welding is used to quickly build parts such as car doors and chassis, as well as by industries including aerospace, where it is used to join overlapping sheets to create aerospace bodies. Resistance welding has an excellent track record for producing quality joints in sheet materials. In the European automotive industry alone, more than 150 million resistance spot welds are made each day.
Resistance welding is also used for a range of other sheet metal fabrication applications, including resistance seam welding (RSEW), which is used for the creation of continuous, gas tight seams for radiators, drums, and tanks, and resistance butt welding (RBW), which is used to join rods, wires and narrow strips of up to ~16mm end-to-end in one operation.