Resistance welding uses heat and pressure to create a bond between two materials. With this type of welding, the heat is generated by electricity. Usually the materials that are bonded together by resistance welding will be metal, but plastics can also be bonded using resistance welding methods. If done properly, resistance welding is a fast and efficient way to bond two pieces of material together, but if done improperly the weld can crack, break and cause many other problems.
Spot welding is a method of resistance welding that is used in small projects and for making repairs. Spot welding is also used to bond thin sheets of metal together. In spot welding, electricity is passed between two copper electrodes, causing heat that melts and binds the metal sheets together. The heat creates, which also aids in the bonding of the metal sheets. Another aspect of spot welding is that, as the name implies, the welds are in small strategically placed spots instead of long welds all along the edges where the two pieces of material come together.
Flash butt welding is used for making butt joints for bar type or tubular components. For example, where two pieces of heavy gauge metal come together this is the type of weld that would be used. For many people this is the type of joint they think of when they think of welding. This type of weld is used in the construction of large buildings, in some places on cars and in other applications where large pieces of metal come together. This is a solid joint weld that is very strong if done properly. This type of welding requires high temperatures to accomplish.
Seam welding is used to seal the seam between two pieces of metal. With this type of welding two wheel-shaped electrodes are needed. The wheel shape of the electrodes allow for long continuous welds that reinforce the metals, making the weld as strong as possible. Many types of welding need to be done by a person in order for the weld to be done properly, but seam welds are often done by machines. This makes for quick, accurate welds that are extremely strong. After the product comes out of the machine it will be checked manually and any mistakes will be fixed manually using spot welds.