GTAW WLD 150 Welding And Joining Practice Test

Heat input rises with the current needed to melt the filler metal. A larger diameter filler rod requires more current to melt and deposit it at the same rate, so the arc delivers more energy into the weld per unit length. That extra energy widens the heat-affected zone and increases thermal distortion in the welded part. Therefore, larger diameter filler metal increases heat input and distortion. The other statements don’t fit the practical relationship: using a larger diameter filler doesn’t reduce heat input, filler diameter does influence heat input because it changes the current required, and while a smaller diameter can require less heat, the statement about it universally reducing heat input and distortion isn’t as accurate as describing the direct effect of a larger diameter increasing heat input.