What is the purpose of the combination of pressure and electric current in resistance spot welding?

The combination of pressure and electric current in resistance spot welding serves the primary purpose of creating rapid heating and fusing of the metal. In this welding process, electric current is passed through the metals being joined, generating heat due to the electrical resistance at the interface of the materials. This localized heating reaches the melting point of the materials, allowing them to fuse together effectively.

The application of pressure during this process is critical as it ensures that the molten metal is forced together, promoting a strong bond as the metals solidify. The balance between the intensity of the current and the pressure applied determines the quality of the weld, making this combination essential for achieving strong and durable joints in various applications.

Other options do not address the primary function of this combination. For instance, while efficiency can be a byproduct of well-executed spot welding, it is not the main goal of using pressure and electric current. Similarly, while preventing oxidation is important, the immediate function during the welding process is the heating and bonding of metal rather than oxidation control. Finally, enhancing the surface finish of the weld is typically a secondary consideration, as the main aim is to achieve a solid and reliable joint through the welding process initiated by the combination of heat and pressure.