25mm double V butt joint

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The other night at Tech I was doing my 25mm double V Joint "for Mig  4 " so it had to be a good one.The most common way is a root run, then a hot pass, next a capping layer in 2 passes and then a final capping layer in usually 3 passes.Did it that way on the first side and it was a good one so I figured I had a pass any way  and I had a good lot of heat in it now so on the other side I did a hot pass over the existing root , then a slow but high deposition cap and finally another pass with the wire wound up 100% and the volts  1 click under max. Did the last pass very slow but running the torch in 3-4mm circles.The end result was a weld about 1" wide ,smooth ,a nice mound up for reinforcement and no under cut ...it looked like a big submerged arc weld. Both teachers passed me on it and when we cut it both sides were fine , one of the teachers said that they prefer the students do this test in multiple passes as it takes more skill and that is what your trying to get at TAFE.Fair enough comment.The teachers and I then were discussing  which would be stronger and the general consensus was there probably not much difference either way but both still lent to wards multiple passes.Wondering  what the professional fabricators on this forum thought
Reply:multiple pass welding is usually beter because of less inclusions in the passes and reduction in scrincage of the welds reducing stress, ecesive weaving can cause too much heat producing perosity in the weld..? thats my thoughts anyway...speed is not always best.some might say its imposible
Reply:Originally Posted by welderjimmultiple pass welding is usually beter because of less inclusions in the passes and reduction in scrincage of the welds reducing stress, ecesive weaving can cause too much heat producing perosity in the weld..? thats my thoughts anyway...speed is not always best.
Reply:Take your sample over to the burning table and cut the weld out setting your torch to cut as close to the weld on each side of the joint.  Take the weld you cut out and nick break it.  To nick break cut a notch with a hacksaw about an eighth of an inch across the face then put it in a big vise with the cut at jaw level.  Pull it over with a pipe extension or hammer on it.  When the weld snaps open look at the grain structure.  The multiple pass section should have a much finer grain.  Most codes limit weld size on fillets to 3/8th on one pass.  Any fillet weld larger must be done in two or more passes.  The only exception I know about is for submerged arc welding where you can put in larger single pass fillets.  Big single pass welds are just not good practice.