What Is Spot Welding?

Last Updated on October 25, 2021 by weldinghubs

Different types of welding processes are common. The method of spot welding is also a method useable for the welding of thin metals. It is also an ancient process used in the history of manufacturing steel cars.

The lower thermal conductivity of the process makes it highly effective for the welding of thin metals. Similarly, the use of current flow for heat generation cuts the cost of complicated construction or installments. The process of spot welding is highly recommendable for a professional welder or a daily hobbyist. It is because a typical spot welder is also of reasonable price.

So, what Is Spot Welding? Another name for spot welding is resistance spot welding. This welding process works by using two copper electrodes that produce an electric current to join the metal sheets. By applying the electric arc and pressure, a detectable amount of heat generates in the metal having less thickness like carbon steel.

How Does Spot Welding Work?

Spot welding melts the metal sheets by the application of electric current. The welder places the metal sheets between two electrodes made of copper metal. The voltage applied across the electrodes causes the electric current to move between the two electrodes. As the current flows through the circuit, a conductive heat of flowing current produces. The amount of heat is enough to melt the metal parts.

The parts melt due to the heat generated. Then, the molten portion of the substance of the two sheets overlaps each other to make a connection. In this way, spot welding helps in the joining of two metal surfaces. The copper electrodes in contact with each other, using the metal sheets to be joined, also apply pressure on the metal parts.

So, a typical spot welding process goes on with the application of pressure and electric current. The electric current gives rise to heat that helps in making a junction between two components. Due to the melting of metallic parts using heat, there is no need for any filler material to join the components.

• You can read our new article: What is a fillet weld?

Types of spot welding

The process of spot welding is mostly useable for the welding of metal sheets. There are different types of the process. Some of the types of spot welding process include:

1. Stationary type spot welder.
2. Bench type spot welder.
3. Portable spot welding gun.
4. Robotics spot welding gun.
5. And multi-head spot welding machine.

All these types have their applications in different circumstances and for different types of material. For example, the process implying a stationary spot weld can make a junction one at a time. To make several junctions or spot welds in a single time duration usually needs the embossing of metal of the sheet.

Advantages & Disadvantages of spot welding

Following are the advantages of the spot-welding process:

• It is comparatively an easy process.
• The process is also cost-efficient.
• The production rate or the efficiency of the process is too much.
• Different metals are easily joinable using the method of spot welding.
• Spot welding is performable in both manual and automatic ways.
• The process is too better for metals that are thin in size.
• There is no need for any skillful person for the spot welding of metals.
• The base metal does not move towards the high heat place in this process.

Everything has its pros and cons. Spot welding also holds some drawbacks. The main disadvantages of the process include:

• The process works only for the welding of thin metals. You cannot spot weld the heavier or thicker metals efficiently or smoothly.
• The welding done through this method undergoes deformation or deterioration.
• The installment cost of the process is too much.
• The welding becomes weak if the supply of voltage becomes very low.

 

Spot welding diagram

A typical diagram representing the construction of a spot-welding process is as follows:

Spot welding procedure 

At first, there are two main parts of a spot-welding procedure.

• Building a connection of two metals.
• Fusing the metal parts.

Following are the further steps of these two parts:

a) Building a connection of two metals

Use these steps to make a smooth and flawless junction or connection between the two metals.

Step-01: Clean the metal pieces and the electrodes using a speck of cloth

Dirt or the rust present on the surface of the metal can deteriorate the quality of welding. Similarly, the dust from a previous weld imparts a negative effect on the quality of the spot weld. If there’s any debris material or dirt on the sheets you want to weld or the copper electrodes, it can produce a spark on the passing of electric current.

So, wipe down the surface of the metal or electrodes using a duster you want to weld. Use a clean cloth for the wiping. So it may not carry any dust or pollute the surfaces anymore. Don did not use any soap, washing detergent, or water to wipe out the area.

Step-02: Clamp the two pieces of metals together.

Connect the pieces of metal you want to join in such a way they remain in front of each other. You can use a pair of grips to make a junction. Clamp the metal sheets in such a way that they don’t have any freedom for moving.

Step-03: Positioning of the electrodes

Bring the electrodes of the welder inappropriate position so that you can place the metal piece in between them. Keep in mind that the electrodes present in the spot welding machine are easily adjustable and moveable. There is an adjustment knob present on the electrodes that help in the relocating of electrodes. Make enough space between the metal electrodes for the metal and then place the metal in between them. Tight the screws so that the metal piece does not move from its place.

b) Fusing of metal sheets

In this step, the metal sheets placed near each other fuse using an electric arc or applying electrode force. Following are the further steps in this process:

Step-01: Use personal protection equipment

Wear a pair of gloves and eye goggles to prevent any sparks produced during the welding. You will experience a bright light and a lot of heat in the process of Spot welding. So, you can use goggles to get protection against it. The spot welding does not cause too many sparks, so there is no need to wear a full welding hood or suit.

The latex gloves and eye goggles are enough to protect your eyes and hands. But you must be conscious of selecting the pair of gloves or goggles that fit your size. Large-sized goggles can let the bright light of the welding enter your eyes. It can cause extensive damage to your eyes. Adjust the goggles to cover your eyes completely. You can get this material from any welding shop or any online store of welding.

Step-03: Turn on the spot welding machine.

Plugin your welder and then turn it on by pressing the button. Try to connect the welder to a circuit that is nearby. The reason is that a switch at a distance can cause the tangling of the wire of the welder. These distractions can cause impairment in the process. When you are going to weld, flip the button to turn it on.

Step-03: Insertion of the metal sheets

Insert the pieces of metal held by the clamp between the tongs of electrodes. Hold the piece of metal between the tongs until the fusion is complete.

Use your one hand to keep the metal in place. Use the other hand to press down the handle of the tongs.

Step-04: Close the tongs to create pressure.

Squeeze the tongs to apply the electrode force on the metal sheets. When the tongs connect with the sheets, the current will pass through the metal and will generate heat over the place you want to weld. The metal will start to heat up after a few seconds.

Step-05: Hold for 3-5 seconds.

If you want to create a smooth and leveled weld, hold the metal in between the electrodes for about 3-5 seconds. It will result in a long-lasting and sturdy weld. Do not allow the holding time to exceed for more than 5 seconds because it will create too much heat that can lead to over-melting of the metal.

Step-06: Cool the metal for 5 minutes.

Take the metal out from between the copper electrodes and monitor it to check that the fusion of metals is complete. Allow the metal sheets to cool before moving towards other welds. Take a cloth and wipe the metal surface to remove any debris.

Step-07: Make sure that the cooling of metal is complete.

Step-08: You can repeat the process of spot welding many times and can make many spots to connect the metal from every place.

Where is Spot Welding Used?

Spot welding is useable in the following fields or industries:

• Aerospace engineering.
• Metal furniture.
• Automotive industry.
• Building and construction.
• Rail system.
• White goods.
• Electronics.
• Medical building and manufacturing.

The easy automation of spot welding with artificial intelligence or robotics helps bring a great deal of productivity. You can use this process for the welding of different manufacturing units. The process is highly useable for the building and construction of cars having steel.

Materials that work for spot welding

Low thermal conductivity and a higher value of electrical resistance control the process of spot welding. The best material for spot welding is carbon steel. Moreover, you can also do spot welding for the steel with great ease. But the spot welding is not better for materials containing high carbon steel. Because the high percentage of carbon results in brittleness that can cause cracks in the welds.

Similarly, the steel that passes through galvanization usually demands high voltage and current. So, spot welding does not go smoothly. The deterioration of zinc alloys occurs due to the copper electrodes. It will affect the quality of welding.

If you want to do spot welding for the steel with a zinc coat, you need to change the electrodes frequently.

The dressing of the electrodes is compulsory. It means you need to remove the contaminants from the surface or reshape the surface of the electrodes.

Parameters of spot welding

• The electrode force is responsible for holding the metal sheets together. If you want to achieve a good melt quality, the electrode force must be sufficient. A suitable value for the electrode force is 90 N per mm2 because the greater magnitude of electrode force decreases the heat energy. The decrease in heat increases the demand for electric current.
• Squeeze time The time duration between the implication of the electrode surface on the metals and the current flow across the electrodes is the squeeze time. There must be sufficient squeeze time so that the level of electrode force gets achieved. So, you must delay the application of current.
• Weld duration or weld time The time of passing of the welding current through the sheets of metals is the weld duration. It must be short. You can calculate the value of weld time by using a simple formula. If the thickness of the sheets to be weld is greater than 2 mm, you can divide the diameter of sheets by 10. In this way, you will know the value of weld time.

Hold time starts after the completion of welding. At this time, you must hold the metal in between the electrodes even after the welding process completes. It is so to allow the metal sheets to cool down. It helps in the solidification of the molten metal and proper overlapping of the metals.

 

Applications of spot welding

Spot welding has a large number of applications due to the feasibility of its process.

Automobile industry:

In this industry, spot welding helps in the joining of steel sheets useable in the building of cars. The use of spot welding in the automobile industry is old. The low thermal conductivity and low cost of the process make it useable to manufacture machines and automobiles.

For electronics:

Spot welding also helps in the joining of metal compartments to manufacture different electrical equipment. But it helps in building infrastructure made of thin metals.

Fusing nails:

Different Nails used in the holding and construction bridges are fused or joined using the spot-welding technique.

Conclusion

Spot welding is the most useable process for welding. It helps in the welding of manufacturing lines and steals cars for many long years. The easiness of the process is because there is no need for any filler material for this process.

You can weld the two sheets of metals by applying pressure and current using an electric arc. All the processes are very smooth and easy and bring no tiredness. There is no need for Ultraviolet radiation protection because you do not have any danger of a bright or luminous arc. Moreover, the cost of a typical spot welder is also reasonable.

FAQ

Is spot welding easy?

Spot welding is easily doable for the steel. The reason is its higher electrical resistance and lower thermal conductivity. However, the metals like aluminum and zinc alloys do not undergo a good or smooth weld. So, you can do spot welding for carbon-carbon steel with ease.

How thick can you spot weld?

Joining parts or metal sheets having a thickness of 3 mm is achievable viva spot welding. The metallic components to be weld must meet a ratio of 3:1. The diameter of the welds made using spot welding must be between 3 mm to 12.5 mm.

Can you spot-weld aluminum?

The process of spot welding is easily useable for metals having a greater thickness or hardness. But pure aluminum, being a very light metal, has less hardness and thickness. So, spot welding does not bring a satisfying efficiency for aluminum due to its reactivity.

How strong is a spot weld?

A shear strength or weight-bearing capacity of 1100 pounds or lbs can be achievable using the spot weld. However, this strength is 499.5 kg less than a full-fledged, penetrated weld. The shielding gas and voltage of the arc are applied to control the area of the interface.

Is spot welding hard?

You may need a large volume and a spacious place for the spot welding. Smooth and efficient welding is not achievable in a narrow area. So, it can become very hard or tiring for your to do a spot weld in a small place. Therefore, spot welding is comparatively a tiring process.

How much is a spot welder?

A spot welder is a workstation used for the overlapping of metal sheets. It works with the application of pressure. A typical spot welder in use of professional welders or DIY hobbyist usually lies in the range of 13.99 dollars to 44.56 dollars. Such welders have an output range of 500 amperes.