7018 cert bend

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okay guys whats up, so im taking a free college course at IVY Tech for welding and all we do is certification bend tests using stick welding with 7018. We work our way up (flat then 2g then 3g then 4g) well ive taken certifications before but not on stick welding. i took the 1g and 2g and passed both of them pretty easily the first time. well, now im on the big one, vertical up, i actually bent today and my face bend passsed perfectly (of course) but, like i figured, the root failed. im pretty good at vert up using the z weave, but its always the root pass that i screw up on. for the root i use the 3/32 elecrodes runnin about 70 amps (not sure but i think the heat is good) i do the typical thing cruise through the middle, pause at the sides. now i figured since i could just practice on plates i decided to run 2 root passes in stringers, looked okay some slight flaws but okay, i got excellent penetration, but then when i used the 1/8 electrodes i screwed up and ran out of time and just threw em away. so...uh...any tips? i dont like runnin vert up in a stringer and would like to do it all weaveing. after the root passes im really good at the weave. dont know why my root passes are always bad, even in MIGStandard Cert  (2) 3/8in. 3x7in. plates with a .25 backing, 45 degree groove angle with a ..25in root opening (sometimes a little bigger for penetration)Last edited by tmcglaughlin; 06-30-2009 at 11:12 PM.
Reply:that root i think would be much easier welded with a 1/8 7018. at least thats what i use with that size joot opening with that angle and thickness of backing. electrode angle at 90* right down the middle of the root opening 115 amps short arc length and just let it fill. which ivy tech do you attend? they have several campuses.
Reply:i live in indianapolis indiana so i attend the meridian campus located in downtown indiana. you use the 1/8 rod on that, do you weave the root or just an uphill stringer?
Reply:just a stringer. not much room to do a weave in that root opening with a 1/8 rod. 3/32 might work with a little weave though. do they offer the unlimited version of that test at the indy campus?
Reply:I took the exact same cert several years ago. I used 3/32" 7018 at no less than 90 amps for the root. The trick I found was to spend a full 2 seconds (I remember counting 1 mississippi, 2 mississippi) on each side of the joint and whip the rod across the center. Keep the arc length real tight, rod pointed slightly uphill and perpendicular to the coupon. Make sure you don't try to rush uphill too fast, and don't burn the rod down to nothing. I seem to remember it took almost three rods to fill the root opening.On the subsequent passes, you'll spend a bit less time on the sides, and travel from side to side somewhat slower, so you don't lose the puddle. The final cover pass should be about 1/2 to 3/4 inch wide, and look like one giant perfect bead, with no undercut on the sides, and not too high across the center. What gave me fits was starting a new rod and trying to make a smooth transition from the end of the previous bead. If your root is pulling from the parent metal on the root bend test, your probably not spending enough time on the sides of the joint. That and 70 amps is too cold.Miller Thunderbolt AC/DC (Sold)Miller Dialarc 250HFMiller MM251Miller MM200 (Sold)Miller MM130Miller Spot WelderVictor O/A rigMiller Spoolmatic 1 (Sold)
Reply:Originally Posted by bratkid63I took the exact same cert several years ago. I used 3/32" 7018 at no less than 90 amps for the root. The trick I found was to spend a full 2 seconds (I remember counting 1 mississippi, 2 mississippi) on each side of the joint and whip the rod across the center. Keep the arc length real tight, rod pointed slightly uphill and perpendicular to the coupon. Make sure you don't try to rush uphill too fast, and don't burn the rod down to nothing. I seem to remember it took almost three rods to fill the root opening.On the subsequent passes, you'll spend a bit less time on the sides, and travel from side to side somewhat slower, so you don't lose the puddle. The final cover pass should be about 1/2 to 3/4 inch wide, and look like one giant perfect bead, with no undercut on the sides, and not too high across the center. What gave me fits was starting a new rod and trying to make a smooth transition from the end of the previous bead. If your root is pulling from the parent metal on the root bend test, your probably not spending enough time on the sides of the joint. That and 70 amps is too cold.
Reply:Did you preheat the base metal? I won't comment on weaves, I have done them, but not under test conditions. I like 1/8" rods up around 115-118 amps also. The root-pass is the heart and soul of your test, it has to be tied into three pieces, each side plate and the backer and all the way up and through. A cold start at the root level is death. Don't try to grab too much of the side plate, while at the same time, don't fail to tie into them. And make sure you are FUSING the backer, not just laying on top of it. Clean every thing shiny. Use a wire wheel or sanding disc to finish the prep-work. That is to say, clean each piece before assembling them together, then clean them again after assembly. No slag, rust, paint and no mill scale in the zone, then the preheat. Keep a nice lively bait, Yellowtail love that. Oh wait, I'm thinking of something else...Relax!! City of L.A. Structural; Manual & Semi-Automatic;"Surely there is a mine for silver, and a place where gold is refined. Iron is taken from the earth, and copper is smelted from ore."Job 28:1,2Lincoln, Miller, Victor & ISV BibleDanny
Reply:As Tanglediver said, make sure your metal is clean (probably the most important advice that I forgot to mention ). We used to bead blast the coupons and backer plate to a near white condition.Make sure your fit up is good also. A lot of times the backer plate may not be flat, due to being sheared instead of sawed (sawn?). I know for a fact a gap between the backer and coupon can kill you on a test. We would clamp everything flat to the bench for tacking.As far as preheat, we never did that, not on 3/8" plate. If you run at 90 amps, it'll burn in without a problem.How long is your backer plate? We cut ours 9", so it would extend 1" past the plate on both ends. Start welding on the backer only, then work your way towards the joint. Same thing at the top of the joint, weld past the joint onto the backer only.Miller Thunderbolt AC/DC (Sold)Miller Dialarc 250HFMiller MM251Miller MM200 (Sold)Miller MM130Miller Spot WelderVictor O/A rigMiller Spoolmatic 1 (Sold)