Where do i need to tack weld???

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Since im at my new job (almost a year but i don't think i will do more there) one of the welders have problems with my tack welds, now im doing the way he want it to keep him shut up, but still don't understand and confused!Im a fitter, so the only welds i do is tack weld (i even have a certification card for that by the CWB haha) , im supposed to know what im doing, and supposed remember what i've learned at school, at school the teacher said for example a typical HSS square with a base plate to make a regular column, tack weld it direct in the center line of the base/HSS or Beam plate ±.The reason for that was because when the welder start to weld, he's supposed to start on the corner of the HSS or Beam, so when he's welding at your tack weld its supposed to melt the tack to ''replace'' the tack with a real weld bead! (im really sorry for this english haha i know its sucks) But the welder at my job say: do your tack weld at the corner, because i start welding on your tack weld so my beads look equal and regular (maybe he's too lazy to get skills otherwise) but i don't judge him, im not a welder!whats about that ? who's saying the thrut ? Personally what my old teacher said sounds logic to me!Calculator > Bevel Square
Reply:As the fitter its basically your job to keep the welder welding. Ask him what he wants. Is he the only welder your fitting for? This is typically how it works in the pipe fitting and welding world. You are a pair the fitter and the welder. Key to a fast and happy welder is a fast and GOOD fitter. Every welder is different, when fitting its not a bad idea to ask the welder how he wants certain things done.
Reply:I'm sort of curious about this too.Most of the stuff I do isn't really that critical, so generally I tack something up, weld the untacked areas, then grind the tack down a bit when I come to it in order to have a nice uniform bead (I don't grind it beyond the penetration zone).  I only grind the tack when I feel it's no longer necessary to hold the piece from moving.  I've seen welding instructions which state that the tack is supposed to be welded over, not removed or ground.  I see the sense of this where you don't want any dimensions to change.But, except at extremely high amps, is it really possible to "melt" the tack weld, and incorporate it into the finish bead?  It seems that the fact that the tack will mess up the uniformity of the bead tells you something....... The tack really hasn't "melted".  Let's face it, penetration into the base metal on the finish bead is hindered by the tack I would imagine.  It's another layer of filler between the rod and the base metal.It's been my experience that welding over a tack can be done successfully, in terms of preserving the beauty  of the finish bead only by increasing travel speed at the tack, thereby in essence "bypassing" it.  Trying to "melt" it just adds a lump because of the extra filler at the tack.  So, in essence, you really are relying on the penetration of the original tack because the finish bead really doesn't provide the penetrating heat at the tack weld because it's blocked by the tack weld filler.I suppose this sounds a little crazy, and I'm overthinking it a bit Granted, the tack filler is incorporated into the finish bead, but I really don't think the full force of the arc goes to the base metal at this point.  I might be wrong, wouldn't be the first time "Any day above ground is a good day"http://www.farmersamm.com/
Reply:Well, that sure was a convoluted mess "Any day above ground is a good day"http://www.farmersamm.com/
Reply:So what I'm really saying is................MAKE SURE YOUR TACKS ARE GOOD, AND NOT JUST A BLOB OF METAL.  It has to be a penetrating tack HOT hot HOT "Any day above ground is a good day"http://www.farmersamm.com/
Reply:somewhere i saw tack defined as a temporary weld..
Reply:http://weldingdesign.com/blodgett/ta...ds-joint-0409/"Any day above ground is a good day"http://www.farmersamm.com/
Reply:http://www.jflf.org/pdfs/papers/design_file103.pdf"Any day above ground is a good day"http://www.farmersamm.com/
Reply:You can't "melt" a tack weld. If you weld over it you'll get a high spot on your weld. Tack it on the corners
Reply:"you can't melt a tack weld"? really? The only reason you get a distortion when burning over a tack is because there is more filler material in that area. simple as that. Not because the tack didn't melt. your tack shouldn't have enough material in it to cause a problem anyway. As for the concerns of the welder vs what the fitter was taught. Do what the welder asks. He's the one who's certified, and it's his name on the weld when it's done.There are no problems. There are only solutions. It's your duty to determine the right one.Hobart Handler 210Airco 225 Amp MSM Stinger
Reply:It depends on the shop but on fussy stuff the tack weld must be ground out and filled with weld.   General guidelines are that you make your weld beads small but at least one inch long.  This will prevent martensite formation if the weld tack cools too quickly.  Make your tacks long and small.  For example if the fillet is 10 mm then lay in a 5 mm tack weld one inch long minimum.  The welder will be able to run right over it slightly speeding up.
Reply:Originally Posted by ThorsHammer"you can't melt a tack weld"? really? The only reason you get a distortion when burning over a tack is because there is more filler material in that area. simple as that. Not because the tack didn't melt. your tack shouldn't have enough material in it to cause a problem anyway. As for the concerns of the welder vs what the fitter was taught. Do what the welder asks. He's the one who's certified, and it's his name on the weld when it's done.
Reply:The bridge code states the tacks are incorperated into the base metal with sub arc welding , still a good tack should be made hot and small . My favorite for my part time job is E7014  1/8 around 180 amps , that will keep it glued down .
Reply:Originally Posted by CamAusYou can't "melt" a tack weld. If you weld over it you'll get a high spot on your weld. Tack it on the corners
Reply:Samm, the first welding job I had I had a couple days where I was instructed on a proper tack and then I was watched closely by another fitter.  The tacks had to penetrate just like the finish weld.  They had to be symmetrically balanced on the legs and look like s mini weld.  Usually you weld a tack hotter than you weld at due to you are aren't inputting a lot of heat that will flatten a weld.  the Tack has to be smaller than the finished weld to.  a good welder can weld right over a tack and you never know it.  he is able to account for the tack with his puddle and weld up to is and over and move on with ease.  if he spends too much time on the tack trying to burn it in he will get a build up and the tacks will telegraph.  most tacks will burn in some but since the tack is rooted like a weld only the face and toes  are burned in.On open root welds the tack is ground so the beginning and the ending of the tack is  ramped and welded over.  some grind down the tack down, and I have but it should not be necessary.
Reply:Layoutman:  you should make your tack welds much in the same manner as you did your tacking test.   My copy of the code is old but:  Tack welds located in the path of fillet welds 10 mm or smaller in size or in the root of joints requiring specific root penetration, shall be sufficiently small that they do not produce objectionble changes in the weld surface or result in decrease in penetration: otherwise they shall be removed or reduced in size by any suitable means prior to welding.   So as it says small beads.  Sorry Zap but if you were subject to a passing glance from one engineer I can remember you would have been scolded like a little child for puttting short dabs in.  This is the voice from one who was taken to task for doing just that.Last edited by lotechman; 05-12-2012 at 10:39 AM.
Reply:So if i understood everythings, it doesn't matter WHERE i have to put my tack welds and its more about the heat and the size of my tack welds right ?Most of the times i just try to put my tack welds where it's easier to align and adjust the pieces that i m fitting!Last edited by LayoutMan; 05-12-2012 at 11:50 AM.Calculator > Bevel Square
Reply:Originally Posted by lotechmanLayoutman:  you should make your tack welds much in the same manner as you did your tacking test.   My copy of the code is old but:  Tack welds located in the path of fillet welds 10 mm or smaller in size or in the root of joints requiring specific root penetration, shall be sufficiently small that they do not produce objectionble changes in the weld surface or result in decrease in penetration: otherwise they shall be removed or reduced in size by any suitable means prior to welding.   So as it says small beads.  Sorry Zap but if you were subject to a passing glance from one engineer I can remember you would have been scolded like a little child for puttting short dabs in.  This is the voice from one who was taken to task for doing just that.
Reply:Yup you can run over them as long as they are small.  I had a continual porosity problem on a Submerged arc production shop.  It turned out that the guys were tacking the assemblies by putting the MIG gun on one location and just pulling the trigger.  The Sub arc would not penetrate and it also gave porosity.  I had to yell and scream at them before they started putting in little one inch long beads.  I pointed out that they were screwing their mates who did the repairs.   Before I figured it out I was told the metal was cheap Chinese junk.  Then the porosity was from the cutting oils left from machining.  Finally I marked where the gobs located with a soapstone.  After sub arc, at every soapstone mark there was porosity.   Small tacks are prone to forming martensite.  Often when doing CWB weld testing which is a groove fillet combination they will show tearing or cracking outside the weld zone where the backing bar was welded to the coupon.
Reply:Originally Posted by LayoutManSo if i understood everythings, it doesn't matter WHERE i have to put my tack welds and its more about the heat and the size of my tack welds right ?Most of the times i just try to put my tack welds where it's easier to align and adjust the pieces that i m fitting!
Reply:Originally Posted by zapsterI agree to disagree..Tacked..Weld over tack..I do this all day every day.If the tacks are smaller than the fill then there is no problem at all.....zap!
Reply:Fit something up using bridge tacks, and see what reaction you get.Bgbkwndo.