Spot Welding: Reviewing the Basics

Mar 29, 2022

Spot welding or electrical resistance welding is commonly used across various industries and is widely considered the most efficient welding process to use when joining two pieces of sheet metal. This is true if the process is done correctly. If not done correctly, the weld will be insufficient, the metals will have to be discarded, and the process will need to begin again with new metal pieces. In this blog, we will explore spot welding and give some helpful tips to help along the way.

What is Spot Welding?

Spot welding is a three-step process involving intense heat and pressure and an electrical current with all three done at precise moments during the welding process. The three steps include:

Aligning the metal sheets. This may be the most important step. All metallic sheets must be lined up correctly. If not, the weld will be incorrect, but the welded pieces will not be detachable. New pieces of metal will need to be used and the process started over again.

The metal sheets should be the same size, at least 3 m.m. thick, for the best results.

Application of electrode pressure. Standard copper electrodes are generally used since they retain heat and resist oxidation. You may need tungsten-copper, tungsten, or electrodes that contain small amounts of Molybdenum (MO). MO increases the strength of steel and electrical conductivity and has a high melting point that prevents delamination (the total separation of the metals).

The electrode force must be precise. If too high, there may be spatter that will adhere to the metal sheets and possibly ruin them. This high pressure may also create a small spot weld that reduces its penetration.

High voltage current flows through the electrodes. After the electrodes are correctly positioned, the welder uses a foot pedal that sends the proper voltage of current through the electrodes into the sheet metal pieces.  At the same time, the welder squeezes the electrodes with the correct amount of pressure.

The current is then switched off and the pieces are held together while they cool down. The hold time depends on the type and amount of current that is used.  It is crucial that the hold time is accurately determined. If the hold time is too long, the metal may crack or become brittle. Too short of a hold time may result in weak welds that pull apart.

What Metals Are Used for Spot Welding?

Steel is the preferred metal for spot welding, but the process also works well with wire mesh. Low-carbon steel works better than high-carbon steel. Nickel alloys, titanium and wire mesh also work well with spot welding.

Aluminum and galvanized steel are not good metals for spot welding since they require higher levels of electrical current and a longer welding time. However, as the automobile replaces steel with aluminum for car bodies, spot welding seems to work well with aluminum in that industry.

Pros and Cons of Spot Welding

Like any type of welding, spot welding has its pros and cons. Some common advantages and disadvantages of spot welding mentioned by experienced welders include:

Pros of Spot Welding:

  • It is a fairly easy and quick process.
  • It is known to be highly efficient and uniformity is easy to achieve.
  • It is more energy-efficient than other forms of welding.
  • It is more economical since it saves on production costs.

Cons of Spot Welding

  • It requires a large working space.
  • It requires high heat which can cause the welder to suffer severe burns.
  • Some hazardous gases may be used which can affect the health of the welder.
  • When used to weld thick materials, the weld will be of low quality and in constant need of repair.

What Industries Use Spot Welding?

Many industries use spot welding. For example:

  • The automobile industry. The process is used primarily to manufacture vehicle bodies.
  • Electronics manufacturing. This includes items such as high voltage cables and circuit boards. Also, spot welding is used for welding gas sensors, solar panels, and switches.
  • Joining steel wires to nails. The process can produce about 1,200 nails per minute.
  • Dental laboratories. Spot welding repairs orthodontic materials and is even used in working with dental implants.
  • Battery manufacturing. The process fuses thin nickel strips to the battery terminals.

Contact Vern Lewis Welding Supply, Inc. for More Information

Learning about various types of welding processes will strengthen your skills and increase the knowledge you take into your practice. By looking at how spot welding is used across various industries as well as the pros and cons, we hope you have gained useful insight into this type of welding.

If you have any questions or need additional information about spot welding, contact one of our locations today and an associate will be glad to assist.

Join Our Newsletter

Receive special offers, product updates, and more!