Vertical Up

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Curious to know as to why or should I say how does vertical up provide more penetration (or does it not) compared to vertical down.  They say that vertical down is mainly used for thin materials.  Can anyone explain this theory?
Reply:Its all to do with travel speed.The arc burns in deeper with a slower rate of travel. Vertical down has little penetration because of the speed of travel required to avoid slag over roll and entrapment.Some operators see vertical up as being harder.It is all about manipulating the arc movement to control the tendency of the molten metal reacting to the effect of gravity.The secret is to deposit the  "runny" molten metal in a  place where it freezes quickly,that being the outer edges of the bead. Conversely the movement from side to side,through the center portion  is rapid, but being just slow enough not to create a slag hole.Judgement is required to place the arc for  the required amount of time on either side to effect no more build up up than would cause slumping. Short arc length  at all times is the key to all out of position welding.Clear as mud ain't it?Grahame.Last edited by Grahame; 01-20-2007 at 04:28 AM.
Reply:I gotcha.  ThanksSlower movements + Side to side + Short arc length = Vertical Up.
Reply:If you find you are having a hard time running vertical up, you can adjust your coupon at a bit less of an angle (45 deg) and work your way back to 90._________________Chris
Reply:Sounds good.  I'll try that.
Reply:I'll add that in vertical up you are building a "shelf" as you weave side to side which will give you something to build upon as you progress up the coupon. Otherwise it gets messy early on. Vertical down is used mostly on thinner wall because you deposit quicker, pipelines are welded in this manner. Once you get past 1/2 inch wall the advantage is lost because you have to stop more often to clean your slag in downhand. Don't know how clear I made that sound, but there it is. Lorenzo nailed it; keep a close arc length. Part of the technique of downhand is using the arc-blow to hold your molten bead in position as you weld. Which vert are you working on?If you don't have the time to do it right, then you definitely don't have the time to do it over.
Reply:There is almost no code work done vertical down.  I do know there are some down hill procedures done for large pipelines.  The great risk with downhill welding is that it is so fast that you will get cold lap at the edges of the bead.  When you weld vertical up you can see the puddle fusing to each side as you build on that shelf.
Reply:Originally Posted by ClanweldI'll add that in vertical up you are building a "shelf" as you weave side to side which will give you something to build upon as you progress up the coupon. Otherwise it gets messy early on. Vertical down is used mostly on thinner wall because you deposit quicker, pipelines are welded in this manner. Once you get past 1/2 inch wall the advantage is lost because you have to stop more often to clean your slag in downhand. Don't know how clear I made that sound, but there it is. Lorenzo nailed it; keep a close arc length. Part of the technique of downhand is using the arc-blow to hold your molten bead in position as you weld. Which vert are you working on?
Reply:The reason vertical up gives better penetration is that heat goes up, the metal is getting preheated before the puddle gets there. On verticle down you're advancing toward relatively cold metal. The puddle tends to lap over cold metal and flux without fusing if great care and the correct rod are not used.
Reply:Originally Posted by lotechmanThere is almost no code work done vertical down.  I do know there are some down hill procedures done for large pipelines.  The great risk with downhill welding is that it is so fast that you will get cold lap at the edges of the bead.  When you weld vertical up you can see the puddle fusing to each side as you build on that shelf.
Reply:I am not aware of any ASME codes that prohibit downhill welding. ASME Sec IX for procedure and performance qualification list the direction of progression as a variable. Individual project specifications may restrict progression. Downhill welding when done properly, has no less strength than uphill. I could see where it would be easy to make a good looking downhill weld that if not done propery, would be poorly fused. I would rather inspect uphill welded joints than downhill welded joints.In many instances, if the arc is NOT one the leading edge of the puddle putting energy into melting the base metal, it is easier to get fusion type discontinuities. When welding uphill, the arc is VERY easy to keep on the leading edge of the puddle. When welding downhill or even flat, this can be a little more difficult. If you go about halfway down this page http://weldinginspectionsvcs.com/WorkPictures.htm  you can see a couple of FLAT welded joints that show lack of fusion. One is a SAW joint with 1/16" wire and over 300 amps. The second was done with FCAW .In my opinion, one advantage of downhill over uphill would be the fact that the convex bead profiles that often come when improper welding is done in the vertical up position, would not occur. This would minimize the risk of fusion discontinuities that would occur between beads.Have a nice dayhttp://www.weldingdata.com/
Reply:Main problem in practice with vert-down is most welders aren't very proficient at it, and if you don't know what you're doing it is very easy to gain slag inclusions. The slag tries to run past your arc and you end up welding over it. Moving quickly, higher heat input and keeping close to your work with a proper stinger angle are all a must for a satisfactory weld bead. I know because I passed a 6G downhand with a 6010 open root/7018 filler, and I can tell you it wasn't easy. Not many foreman want to see that kind of welding because they are used to seeing guys screw it up royally, even taking it as a sign the welder doesn't know his stuff when he (or she, nod to weldrwmn) attempts it. Cold lap can be a problem,. but the problem lies with the operator. In a nutshell, it's a specific technique that has it's place and when done properly will pass xray and destructive testing.If you don't have the time to do it right, then you definitely don't have the time to do it over.
Reply:Heat goes up in air or a gas- not in a solid. It travels equally in all direnctions in a solid.
Reply:Originally Posted by turboblownHeat goes up in air or a gas- not in a solid. It travels equally in all direnctions in a solid.
Reply:Originally Posted by tresiThat's interesting! A few weeks ago I had to repair a horizontal crack in a piece of equipment. The two pieces that were cracked was 3/4" thick and 5 1/2 " wide. It's been kinda cool here lately and it was an unknown alloy so I gave it a little preheat, about 200- 250 degrees. During this job I had a short interruption. I checked the temp before starting back up. The temp below the crack was around 240 while the temp above the crack was around 460. It would interesting to more closely map temps, distance from the weld and time.
Reply:Originally Posted by tresiThat's interesting! A few weeks ago I had to repair a horizontal crack in a piece of equipment. The two pieces that were cracked was 3/4" thick and 5 1/2 " wide. It's been kinda cool here lately and it was an unknown alloy so I gave it a little preheat, about 200- 250 degrees. During this job I had a short interruption. I checked the temp before starting back up. The temp below the crack was around 240 while the temp above the crack was around 460. It would interesting to more closely map temps, distance from the weld and time.
Reply:On the nosey.If you don't have the time to do it right, then you definitely don't have the time to do it over.
Reply:Originally Posted by SrA_USAF(Stupid question) What did you use to check the temp?
Reply:Originally Posted by SrA_USAF(Stupid question) What did you use to check the temp?
Reply:Originally Posted by enlpckIf the piece wasn't insulated, most likely the air picked up heat from the lower part and rose (convection) reducing heat loss from the upper part. Also, during welding, the heat that is not picked up by the material being welded will induce convective currents (in the air, gas from the welding process, etc), preferentially giving heat to the upper piece.
Reply:Originally Posted by lorenzoProbably a thermal scanner.... like the one I usehttp://i147.photobucket.com/albums/r...d%20up/P08.jpg
Reply:As all the postings here are really good information I have to add that I believe a vertical down weld can be just as strong as a vertical up if done properly. I have welded on a lot of 3/4" angle in a vertical down fashion and to this day I have never had a vertical down fail. If a welder is experienced enough then he/she should be able to establish a good vertical down weld. As far as heat transfer well I think that depends on your method of welding, travel speed, etc... I like to use what I call the back stepping method which can help with distributing the heat in a vertical down weld. I do a lot of robot programming and have used both vertical ups and downs and have had success both ways.
Reply:I knotice that when going down that the pool follows the arc at about the same rate as the arc.  Would it help to lower the volts and raise the amps?  I'm talking very little adjustments that way the weldor has to concentrate his arc a little longer rather than letting the pool just fall too fast.
Reply:The method is to up the amperage, for instance 1/8" 7018 on vert up you would run approx 155A, downhand up it to 165A. Voltage is not a factor. You are using the arc blow from the welding rod to hold back your puddle as you progress down the joint. You are moving at a faster rate of travel than if you were running an uphill bead. Takes lots of practice.If you don't have the time to do it right, then you definitely don't have the time to do it over.
Reply:What about MIG.Wouldn't want to give you bad info; I've done it successfully but don't know the corrrect technique.If you don't have the time to do it right, then you definitely don't have the time to do it over.