Submerged arc welded spiral steel pipes use continuous welding wire as the electrode and filler metal. During operation, a layer of granular flux covers the welding zone. The electric arc burns beneath the flux layer, melting the wire tip and part of the base metal to form a weld. Under the heat of the arc, the upper part of the flux melts into slag, which reacts metallurgically with the molten metal. The slag floats on the surface of the molten metal pool, protecting the weld metal from air pollution and reacting with the molten metal to improve its composition and properties. It also allows the weld metal to cool slowly. Submerged arc welding can use higher welding currents. The advantages of submerged arc welded spiral steel pipes are high weld quality and high welding speed. Therefore, it is particularly suitable for welding large-diameter spiral steel pipes. Moreover, most submerged arc welded spiral steel pipes are produced using automated welding methods and are now widely used for welding carbon steel, low-alloy structural steel, and stainless steel.

High-frequency welding, also known as induction welding, is a solid-state resistance welding method. Based on the way high-frequency current generates heat in the workpiece, it can be divided into contact high-frequency welding and induction high-frequency welding. In contact high-frequency welding, the high-frequency current is transferred to the workpiece through mechanical contact. In induction high-frequency welding, the high-frequency current generates an induced current within the workpiece through the coupling effect of an external induction coil. High-frequency welding is a highly specialized welding method, requiring dedicated equipment depending on the product. It boasts high productivity, with welding speeds reaching up to 30 m/min. Using solid resistance heat as its energy source, the resistance heat generated within the workpiece by the high-frequency current heats the surface of the welding zone to a molten or near-plastic state, followed by the application (or non-application) of an upsetting force to achieve metal bonding.