In a butt welding process using arc welding, the arc power is found to be 2.5 kVA. The process is used to weld two steel plates each of 3 mm thickness as shown in the figure. Determine maximum possible welding speed. It is assumed that the metal transfer is of short circuit type and the arc is on for 85% of the total time. Take α_steel = 1.2 × 10^-5 m²/s, k_steel = 43.6 W/m°C, melting point of steel = 1530°C and ambient temperature = 30°C.