Chapter 1 1. Introduction Resistance welding covers a wide range of specific processes, mainly use for highly automated or even fully mechanized welding application, the majority in mass production. All these processes, except one (ESW, electroslag welding), need a mechanical clamping and pressurizing system to compress the workpiece areas intended to be welded prior to welding. Thus, these welding applications are categorized as resistance pressure welding processes (See figure 1-1)

Figure 1-1 principal types of resistance weld In Resistance Spot Welding, passage of a relatively high welding current I [kA] throughout a locally compressed workpiece area (by means of an electrode force F [daN]) during a properly defined period of time t [cyc, ms] heats this area due to resistive heating following (Figure 1-2)

Figure 1-2 principal of resistance of spot welding Values for Welding Force [daN], Welding Current [kA] and Welding Time [cyc, ms] are available in database format, and these values are commonly used to make a base setting to start from. Fine tuning within the parameter range (weldability lobe) can be done in order to optimise towards a specific application according to EN ISO 14327-2004 (Resistance welding – Procedures for determining the weldability lobe for resistance spot, projection and seam welding). Such a weldability lobe covers a range of combinations of welding current and welding time at a specific welding force level that lead to welds with sufficient dimensions, with a lower boundary indicating “stick” welds, and then an area of increasingly growing weld size towards the maximal possible weld size, followed by the upper boundary leading to splash welds. A so called stick weld is a