Direction: Resistance spot welding of two steel sheets is carried out in lap joint configuration by using a welding current of 3 kA and a weld time of 0.2 s. A molten weld nugget of volume 20 mm³ is obtained. The effective contact resistance is 200 micro-ohms. The material properties of steel are given as (i) latent heat of melting 1400 kJ/kg, (ii) density 8000 kg/m³, (iii) melting temp 1520°C (iv) specific heat 0.5 kJ/kg°C. The ambient temp is 20°C.