WIRE MELTING CHARACTERISTICSA non linear relationship exists between the rate at which the wire is fed into the arc and the current required to burn it off to maintain a constant arc length. This is known as the burn off characteristic and differs for each filler wire composition and diameter. The curves shown in Fig. illustrate the burn off characteristics of steel in Argon + O2 mixture. It will be seen that to alter the welding current a proportionate increase in the wire feed rate is required. The smaller the diameter of the wire, the faster is the wire feed speed required to reach the same current.