What is Spot Welding?
Spot welding (also known as resistance spot welding) is a resistance welding process. This welding process is used to weld two or more metal sheets together by applying pressure and heat from an electric current to the weld area.
It works by bringing copper alloy electrodes into contact with sheet surfaces, whereby pressure and electric current are applied and heat is generated by current flow through resistive materials such as low carbon steels.
Spot welding is among the oldest welding procedures. It is used in a wide variety of enterprises, but especially for welding steel sheet automobile bodies.
What is Spot Process?
Spotting is the process of connecting two metals without filler material. The formula used to calculate the relationship between voltage, current, and resistance in an electrical circuit known as Ohm’s Law is used for spot processing.
Spot welding, which depends on the amount of heat and the thermal conductivity and electrical resistance of the metal, as well as the time the current is applied, can be expressed by the following equation:
Q = I2Rt
In this equation, “Q” is heat energy, “I” is current, “R” is electrical resistance, and “t” is when current is applied.
These metals, which are joined to each other by heat, are cooled with water after spot welding, and the welding process is completed.
Basic Features of Spot Welding
Advantages of Spot Welding
- It is considered one of the most efficient welding processes.
- Typically used to join two or more metal sheets together.
- Spot welding gives reliable results and creates long-lasting welds.
- Because spot welding uses an electric current flowing through the electrodes, no metal welding material is required.
- It prevents breakouts.
- It is a fast welding process.
- There is no risk of electric shock.
- There is no possibility of deformation while welding.
- It is a fast process that keeps your projects running smoothly.
- A large amount of energy allows welding to occur without applying too much heat to other areas of the metal.
At Aktif Lazer, we use spot welding and argon welding in welding room operations. You can check our page for detailed information.
How is Spot Welding Made?
Spot welding, a type of resistance welding, is one of the oldest welding processes where two or more metal layers are welded together without using any filler material.
The process involves applying pressure and heat to the weld area using shaped alloy copper electrodes and conducting an electric current through the weld pieces. At the spot weld; the material melts, fusing the pieces at the point where the current is cut off, the pressure from the electrodes is maintained and the molten “nugget” solidifies to form the joint point.
The welding heat is generated by the electric current transferred to the workpiece through copper alloy electrodes. Copper is used for electrodes as it has high thermal conductivity and low electrical resistance compared to most other metals, allowing heat to be generated preferentially in the workpieces rather than the electrodes.
Stages of Spot Welding
The best way to understand how to spot welding is done is to examine the construction stages.
Step 1: workpieces and metal sheets are aligned;
First, the workpieces or metal sheets are lined up perfectly aligned to each other. This is a very important step because once the plates are welded together there is no going back. If they are not aligned correctly, the weld will be wrong and you will have to repeat this step.
Step 2- electrode pressing;
In the next step, suitable electrodes are selected for welding the two workpieces together. Instead of pure copper resistance electrodes, the pure insulating material is used because of its ability to retain heat and resist oxidation. It also contains Molybdenum (Mo) fractions which have a sufficiently high melting point to prevent delamination.
Step 3 – made so that the current passes through the electrodes;
Once the electrodes are in place, a pedal is used to create a high-voltage current that flows through the rods and workpieces. When it comes to quality welds, it is very important to clamp the electrodes into the metal sheets with the appropriate amount of pressure.
The heat required to melt the metal is generated from the resistance of the base metal and is limited to the junction of the electrode and the weld area. During the holding phase, the flow is turned off while the pressure is maintained and the metal sheets are allowed to cool.
The amount of time the current passes through the workpieces and the type of current used to depend on the thickness and type of material you are working with. After the sheets are joined correctly, the electrodes are removed and repositioned at the next spot to be welded.
Uses areas of Spot Welding
Due to its low thermal conductivity and higher electrical resistance, weld detection of steel is relatively easy, suitable for low carbon steel spot welding. However, high carbon content steels are prone to poor fracture toughness or cracking in welds as they tend to form hard and brittle microstructures.
Galvanized steel (zinc-coated) requires slightly higher welding currents to weld than uncoated steel. In addition, copper electrodes in zinc alloys rapidly deteriorate the surface and cause loss of weld quality. When spot welding zinc-plated steels, the electrodes either have to be changed frequently or the electrode tip surface is observed where a cutter removes contaminated material and reshapes the electrode to reveal a clean copper surface.
Other commonly spot-welded materials include stainless steels (especially austenitic and ferritic grades), nickel alloys, and titanium.
Although aluminum has thermal conductivity and electrical resistance close to that of copper, the melting point for aluminum is lower, which means it can be welded. However, due to its low resistance, very high current levels must be used when welding aluminum (two to three times higher than steel of equivalent thickness).
Copper and its alloys can also be joined by resistance spot welding, but spot welding copper is not easily achieved with conventional copper alloy spot welding electrodes because the heat generation at the electrodes and the workpiece are very similar. Electrode materials typically used for copper spot welding include molybdenum and tungsten.
Sectors where spot welding is applied
- automobile industry
Spot welding is a popular welding method in the automobile industry because it is an inexpensive but effective way of joining sheet metal. Therefore, it can be used with trained personnel or robots as it requires very little skill. As a result, it means more cars are being developed because the welding process is fast and efficient.
- for electronics
This welding method is widely used in the manufacture of electronics such as circuit boards, gas sensors, and even solar panels. This method is known as electronic resistance welding and is also used to create complex and delicate electrical components, from wires to switches to hand tools.