Mil Spec Std.1595a

By - Date 08-17-2000 01:40

I am currently certifying under mil spec std 1595a and was hoping someone could advise me on the procedures for welding inconel 718. We have to weld an open butt .060 plate with argon purge. Everyone seems to have the same results, Lack of fusion. This is hard to beleive because the visual inspection shows complete fusion and a very nice looking root. The xray shows a dark line running thru the center of the weld. It looks like if you can see both the front and backsides of the weld and all the walls were broke down with a nice looking bead, that there could be no L.O.F. How can this be? Aparently there is some oxidation getting trapped in the core of the weld? If anyone is familliar with this, I would certainly like to hear from you along with a few others that are currently certifying under this procedure. Thanks for any help--C.l.

By - Date 08-17-2000 14:58

The indication you are describing is called hollow bead which could be caused by several things , spacing too tight , dirty bevel , running the bead too fast , try changing your welding parimeters & you should have the problem solved. good luck DARRELL HENRY darrellhenry@whitewinginsp.com

By - Date 08-20-2000 15:44

Thanks Darrell, Could you give me a little more input on "hollow Bead" and what can be done to prevent it? What kind of gap should be used for .060 thick plate with a feather edge bevel using .060 filler wire? We are using an .060 gap. I don't think cleanliness is a problem because we are buffing with scothbrite and cleaning with alcohol. Thanks for the reply--C.L.

By jodycollier Date 12-29-2000 13:02

I experienced the same phenomenon on .040" inconel 718 square groove butt weld 1g position. X -ray indication was a straight line down the middle of a weld that was obviously penetrated. The suspect weld was then sectioned in seven areas where the indication appeared assuming we could better characterize the indication at 100-200x . After metallographic prep including electrolytic etch using 10% oxalic acid, guess what? there was no indication of lack of fusion or hollow bead, only grain boundaries that were thick and of the typical columnar arrangement in a weld bead and that were perfectly alligned in the center of the bead. The main obvervation of the weld was that it was welded with a faster that normal travel speed. It is still hard for me to imagine how this caused enough change in density for it to cause a distinct RT indication ,but it happened . My best advice is to take a look at travel speed, if ripples are elongated or v shaped slower speed should be used