I was welding a s.s blow pipe the other day, 60'' diameter, 1/8'' thick and when I ground a bit of the weld down, not all of it, there appeared to be a small line, like a hair line crack. If I feathered the grinder a bit it would appear to disappear. The pipe is 304/L and the mig wire I used was
316/L and I also tried 308/L with the same results. Any idea what this is and is it cause for concern. Thank you........Ed