1959 Volume 28 Issue 12 Pages 871-880
The hot-start has been thought to have the two functions, i. e., (1) easy arc striking and (2) deep penetration. In addition, the authors have found the third function, (3) elimination of blow holes. From the X-ray results of many short bead tests, optimum hot-start conditions are concluded as follows ; (a) boosted current is between 1.5 and 2 times of rated welding current and (b) the duration time of hotstart is between 1 and 2 seconds. The reasons why the hot-start can eliminate blow holes are explained by (a) rapid shutoff of air into arc by easy arc striking and (b) increased heat input into base metal.
A hot-start circuit without relays is achieved by using a magnetic amplifier with time delay characteristics.