Resistance spot welding is the joining of metals by applying pressure and passing a current through the area of metal to be joined for a limited period of time. The key advantage of resistance welding is that no other materials are required to make the joint, making this process extremely cost-effective.
There are various forms of resistance welding (e.g. spot, seam, projection, flash and upset), which differ mainly in the type and shape of the welding electrodes used to apply the pressure and conduct the current. The electrodes, typically made of copper-based alloys due to their excellent conductive properties, are cooled by water flowing through cavities inside the electrode and the other conductive tools of the resistance welding machine.
Resistance welding machines are designed and built for a variety of automotive, aerospace, and industrial applications. Automation makes the action of these machines highly controlled and repeatable, allowing manufacturers to produce quickly.
How Does Resistance Spot Welding Work?
In this process, pressure and heat are applied to the weld area using shaped copper electrodes that pass an electric current through the elements. The material melts and fuses the pieces together. At this point, the current is turned off, the pressure from the electrodes is maintained, and the molten “nugget” solidifies to form the joint.
The welding heat is generated by the electric current, which is transferred to the workpiece through electrodes made of a copper alloy. Copper is used for the electrodes because it has high thermal conductivity and low electrical resistance compared to most other metals, ensuring that heat is preferentially generated in the workpieces rather than in the electrodes.
Types of Resistance Spot Welding in Malaysia
- Flash Welding
Like other Resistance Welding Processes, Flash Welding uses heat generated by resistance to welding current flow and the force to push the workpieces together applied over a defined period of time. Flash Welding is a Resistance Welding Process, which creates the resistance by flashing action. This effect is produced by a very high current density at very small contact points between the workpieces. At a predetermined point after the flashing starts, a force is applied to the workpieces, and they are moved together at a controlled speed. The rapid compression created by this force drives oxides and contaminants out of the weld.
- Projection Welding
Like other Resistance Welding Processes, Projection Welding uses the heat generated by the resistance of the welding current and the force to push the workpieces together applied over a defined period of time. Projection Welding locates welds at predetermined points by using protrusions, embodiments, or overlaps, all of which concentrate heat generation at the point of contact. Once the welding current creates sufficient resistance at the contact point, the protrusions collapse to form the weld nugget.
Solid protrusions are commonly used when welding fasteners to parts. Embodiments are often used when joining sheet or plate material. An example of Projection Welding with material overlaps is cross wire welding. In this case, the intersection of the wires themselves localizes the heat generation and thus the resistance. The wires settle into each other, forming a weld nugget.
- Upset Welding
Like other Resistance Welding Processes, Upset Welding uses the heat generated by resistance to the welding current, as well as the force to push the workpieces together, applied over a defined period of time. Similar to Flash Welding, Upset Welding the workpieces are already in firm contact with each other, so there is no burr. The pressure is applied before the current is switched on and maintained until the process is complete.
- Seam Welding & Spot Welding
Resistance Seam Welding is a subset of Resistance Spot Welding, in which wheel-shaped electrodes are used to transfer force and welding current to the parts. The difference is that the workpiece rolls between the wheel-shaped electrodes while welding current is applied. Depending on the setting of the welding current and the welding time, the welds produced can be overlapping and form a complete weld seam or simply be individual weld spots at defined distances. Resistance Spot Welding, like all Resistance Welding Processes, creates welds by heat generated by the resistance of the welding current between the joining surfaces and by force to compress the workpieces over a defined period of time. Resistance Spot Welding uses the face geometries of the welding electrodes themselves to focus the welding current on the desired weld joint, as well as to apply force to the workpieces. Once sufficient resistance is generated, the materials settle and bond, creating a weld nugget.
Resistance spot welding is a welding technique used for almost all known metals. The actual welding is done at the interface of the parts to be joined. The electrical resistance of the material to be welded causes local heating at the interfaces of the metals to be joined. In order to achieve the most satisfactory result, welding procedures must be developed for each type of material. TSIS Welding Solutions offers full technical support to provide an innovative solution to our customers. They are always welcome to test run, demo and weld test before purchasing our products. Call us now!