MMAW advice - 3G

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Alright I am doing a 3G ticket which is MMAW Hydrogen Controlled on plate and I'm a bit over my head. Please lend some advice on polarity and current settings.Welds that I need to pass on are 3 pass fillet - 10mm Got this weld down:Pre heat plate1st run 6mm - 4mm Electrode 7018 H8 Ferrocraft 55U on 190amp DCEN2nd run extend the leg 4mm - 4mm Electrode 7018 H8 Ferrocraft 55U on 175amps DCEP3rd run capping - 4mm Electrode 7018 H8 Ferrocraft 55U on 160amps DCEPVertical up 2 or more passes - 10mmHaven't tried this one yet!What should my polarity be? DCEN so the heat is in the plate? 4mm or 3.2mm Electrode?Horizontal butt - CP?Overhead butt - CP?At the moment I only get a chance to stick weld Thursday nights and that's at the course so any advice I can take with me and try out would be a bonus. Thanks guys
Reply:All the E7018 electrodes I'm familiar with are meant to be run in DCEP or AC polarity.  Not DCEN.  Cellulosic electrodes can be used in DCEN, but not low hydrogen EXX18 electrodes.In regards to the rest of your question, I"m not sure I understand the joint preparation you're using.  What's the base meta lthickness?  Pipe or Plate?  What's the bevel angle, root opening, and root face?  Is this an open root joint?  Or are you using a backing strip/ring?I assume the first case you describe is a flat or horizontal joint.  For the vertical joint your heat should be somewhat lower, maybe 15% or 20% lower.  Likewise, I'd opt for the 3.2mm(1/8") electrode over the 4mm(5/32") rod.  This will also drop your heat input.  For the overhead, you can use heat settings anywhere between the settings you use for vertical and flat/horizontal.  All this assumes you're using some kind of backing strip.  Settings for the first bead on an open root joint will depend greatly on the joint prep.Post some additional descriptions, and we'll see if we can help.  Good luck.Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:From his description it sounds to me he's talking about a 2F horizontal T-joint on 3/8" plate (10mm ~= 3/8") for the first weld.  He talks about a fillet weld and extending the legs on the second and third passes.  6mm legs on first pass, adds 4mm to one leg on each of the next 2 passes, for a total leg length of 10mm.Not enough information about the other joints.MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op
Reply:Perhaps, but the opening line of the OP's post mentions a '3G ticket'.  Your guess is as good as mine(or better).  I suggest we wait and see what he says... Originally Posted by DesertRider33From his description it sounds to me he's talking about a 2F horizontal T-joint on 3/8" plate (10mm ~= 3/8") for the first weld.  He talks about a fillet weld and extending the legs on the second and third passes.  6mm legs on first pass, adds 4mm to one leg on each of the next 2 passes, for a total leg length of 10mm.Not enough information about the other joints.
Reply:Gday i say u are talking about your 3E not 3G for AS1796 and am doing that at the moment for all the welds I am using the same electrode I am using 4816 WIA 16TC for all the welds and on AC current.  For the 3 pass horizontal fillet I preheat the plates a little and do my first pass at 190 amps with a 4mm electrode and then put the last 2 passes in at 160amps also with a 4mm electrode.  For the vertical up fillet i use a 3.2mm 16TC electrode with the plates also preheated a little and do the first run at 130 amps and the second at 120 amps.  For the horizontal butt weld i use a 2mm root face and about 2.5mm root gap and put the root run in with a 2.5mm 16TC electrode and then change to a 3.2mm electrode at 130 amps and put 2 more runs in to nearly filling the vee and then put 3 capping passes on with the first 2 at 130 and the last at 120 to try and stop the undercutting on the top edge. I haven't done many overhead yet so cant really coment but the ones ive done the settings are very similar to the horizontal butt.
Reply:3.2mm for your vert up 4.0mm for down hand make your root face the same as your gap. a good gapguide is stick your steel rule in the gap add give a bit of a wiggle. tee joint no gap butt joint gapbetween 120-130 amp.
Reply:The horizontal fillet and vertical fillet are on 12mm plate and the horizontal and overhead butt welds are on 10mm plate for those that are asking this is if he is doing 3E which id say that is what he is talking about.  The size of the weld for the fillets is 10 to12mm, outside of this range and you fail and the butts have to be within 3mm of each side of the preparation.Last edited by davidw88; 09-10-2009 at 11:46 PM.
Reply:3E Yes, Sorry I was tired when I wrote the OP. Thanks for the responses. All the books I've been reading have lead me to believe that DCEP will give greater penetration as 2/3 of the heat is built up in the positive side of the arc in this case the work. Thou when I've done nick break tests, I found a slightly noticeable difference in penetration between DCEP and DCEN. Cigweld Consumables Guide said in relation to the electrodes Ferrocraft 55U "The preferred polarity for ease of use in root pass welding is DC-" then later saying DC+ was preferred for capping. Would anyone care to shine some extra light on this?At the moment I've only done the 3 pass horizontal fillet, Got a welding procedure that works(OP) may need to change it after trying things posted above.Thanks
Reply:i personally never run any 7018 on anything but dcep. even though its ac capable i stay away from that too. i also weld with cellulosic electrodes on dcep. if i weld with stick, its pretty much dcep. if you weld with these rods on dcen around here ppl tend to look at you kinda funny. dcen does give a more shallow penetration. used more for sheet metal with F2 rods.
Reply:I only ran 16's on negative once and all i seemed to get was alot of porosity so i never done it again, either run them on positive or on AC.
Reply:So you guys are running a rod a 5/32 7018at 190 amps? Seems a little hot for me especially on 3/8 plate. and a 1/8 at 130 amps is certainly at the highest end of the range for customary applications.Last edited by lugweld; 09-13-2009 at 09:02 AM.Esab Migmaster 250Lincoln SA 200Lincoln Ranger 8Smith Oxy Fuel setupEverlast PowerPlasma 80Everlast Power iMIG 160Everlast Power iMIG 205 Everlast Power iMIG 140EEverlast PowerARC 300Everlast PowerARC 140STEverlast PowerTIG 255EXT
Reply:The welding certificate is for the welding of pressure vessels if you don't run the first pass on your horizontal fillet at 190 with the 4mm the bottom corner of the plate will not get penetration and that is with a machined edge but the other runs dont have to be run so hot the next 2 passes i only put in at about 160 to 165. For the vertical up fillet I run the first pass at 130 otherwise you will not get the penetration in that corner either, and the capping pass at 120, thats with a 4816 electrode which is the equivalent to a 7016 in american rod numbers.
Reply:Gday, just wondering how u went with your test, did u pass?