Spot Welding
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Spot Welding Service
Spot welding is accomplished by applying sufficient pressure to fuse metals by transmitting low voltage and high current electrical pulses to the welding electrodes, causing the metal to melt instantly. This process is similar to cold welding in terms of applying pressure, but no electric current is applied to the weld in cold welding.
The first stage in spot welding is overlapping metal sheets or pieces. Once the metals are securely positioned, pressure is applied by electrode force. This pressure can be applied manually, pneumatically, through springs or hydraulics, depending on the type of machine.
The second stage is the application of high current to the targeted area between the electrodes. The current reacts with the internal resistance of the metals, creating molten metal. The metals reach temperatures of around 2000 °C, above their melting point. The electrodes need to have a higher melting point than the workpieces. Usually, copper alloy electrodes are used, but depending on the metal being welded, the electrodes can also be made of tungsten, molybdenum, and other materials.
The final stage is the cooling and solidification of the ingot. During this stage, the welding electrodes remain in contact with the ingot and act as a support as the metals cool and harden. Once the metals have cooled, the process is complete. It is important to note that Nova Fabrication specializes in joining metals in the spot welding process. In this process, Nova Fabrication’s technological equipment and experienced teamwork ensure high-quality welding results.
What Is Resistance Spot Welding
Spot welding (RSW) is electric resistance welding that joins overlapping metals between two electrodes. The workpieces are held together by pressure applied by squeezing between the electrodes, and heat is generated by the passage of welding current through the resistant metals. This allows the materials to join and form a weld joint. The joint created by resistance spot welding looks like a button or a core. Hence, spot welding derives from the precise application of current to a small area on the metal surface.
Because the metals are joined using a large amount of energy over a short period (approximately 10-100 milliseconds), the area around the welding core is not affected by excessive heat, which means that the heat-affected zone is minimal, and a clean weld is created. At Nova Fabrication, we continue to deliver clean and reliable welding results with our expertise in spot welding technology. In the process, our company’s technological infrastructure and team of experts work to create high-quality and durable welds.
How Does Spot Welding Work?
The spot-welding process is simple. It works through the delivery of high voltage current concentrated on a small patch that is under pressure. The electric current is powerful enough to instantaneously melt the metal and start the fusion process. In this case, it’s highly imperative that the workpieces are aligned properly. Failure to do so can cause the product to fail and waste the material.
Another important element that determines the quality of the weld is the pressure, it has to be perfect as too little would result in subpar weld quality and too much of it could damage the base material.
In its essence, the process for these products requires three basic steps. Anything else prevalent in the industry today is an additional step to maintaining consistent quality and standards in the process. Here are the three basic steps of spot welding.
Step 1: Aligning the Workpieces
With spot welding machines; The material is melted, the parts are fused at the point of interruption, the pressure from the electrodes is maintained, and the molten “nugget” solidifies, creating 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.
Step 2: Applying Pressure
The second stage is the application of pressure. Spot welding operates through a combination of both pressure and heat from current flow. Generally, pure refractory copper electrodes are the perfect choice for this because they resist heat and don’t oxidize even under immense pressure. This way ensures that there is no material flaw like an unwarranted reaction or delamination in the workpiece.
Step 3: Letting the Current Flow
The final step after selecting the pressure and position of the electrodes is to start the current. Generally, a leg pedal initiates the circuit and allows the current to flow, which concentrates on a single point and causes it to melt.
The time and intensity of the current depend on the overall thickness of the two workpieces. After the fusion, the current close off but the pressure remains the same so that the workpieces can join properly.
Advantages of Spot Welding
Spot welds are the common choice for the automobile sector where both functionality and aesthetics are extremely important. This balance is one of the most important advantages of the welding process that sets it apart from other processes like TIG and MIG welding.
Here’s a list of the few advantages of deciding to join sheet metals with a spot weld:
- Fast, clean, and efficient process with little to no post-processing requirements.
- A simple and straightforward process that doesn’t need much training.
- Works without any open flame, while is both dangerous and inefficient.
- Robots in the assembly line can create a spot weld as the process is relatively straightforward.
- Can join multiple metal sheets at the same time.
- It doesn’t need any filler material.
- Cost-effective and inelaborate as it doesn’t need inert gases or filler metals.
Disadvantages of Spot Welding
While there are several advantages that make spot welds a success, there are some drawbacks too. Here are a few disadvantages that go against the spot-welding process.
- Even the smallest misalignment in the workpieces can cause major issues.
- The process may cause permanent deformation in the base metal, which affects the aesthetics.
- The process doesn’t work on thicker metal pieces that are thicker than 3mm.
- Spot welds are localized, which might be weaker than other welding joints.
- The final quality depends on the pressure. Any variability in pressure can significantly reduce the quality.
- Electrodes may need replacement after some time because of thermal cracking.
