Technique for welding jointed tubes

[hotrodteg]

Hey guys I have a question about the kinda of technique you guys use to get nice consistant beads. I been practicing with tubes of mild steel that I have notched and tid welded together.

The question is when running the puddle do you guys form the puddle on both sides of each tube the dab the wire in and run the puddle again and dam? Or is there a different kinda technique used to get the weld like the picture I have attached on the bottom of this page?

These are pictures of tig welds on 4130 tubing for roll cages that i found on a website. I just really curious on what kinda technique is best. I cant get the consistent beads like this photo. Thanks I will post some pictures of my welds tommorow.

Also can anyone tell what kind of technique is used hear?
Run puddle and dab, lay the filler down and run over it? thanks

[jarto017]

I'm by no means an expert on the subject, but I have welded some tube so I'll take the bait. If your fit up is nice and tight, like it should be with tig, you should be able to start a puddle in the middle of both tubes, sometimes adding a dab of filler helps. Then you should be able to walk the puddle around the joint using whatever technique you are comfortable with. Either way those are nice welds.

[hotrodteg]

Thanks for the input jarto017

So you start your puddle in the middle between both pipes then run and dab?

Thats the technique I been doing but still cannot get beads that look likt the picture above that I attached I guess it will just take some time and practice.

[jarto017]

Snap some pics and I'm sure someone will be able to better diagnose it for you.

[dandimand]

I weld like that all the time its years or practice to get good at it and those are nice. just dab and move a small torch helps and you have to be comfortable use a foot pedal etc.. fit up should be zero gap and there has to be a vent hole drilled inside of each tube welded as if you dont it will have a blowout .er70s-2 is the rod to use dont use the -3 it causes some porosity not sure why but it does. if you dont have a good fit welds like that are pretty much impossible .if your new at it i would just lay the rod in and weave it in just watch the undercut honestly this will be just as strong just not quite as pretty .the other technique could be learned on fillets once you have that down then you can try on the tube . what most ppl dont realize is your doing this in all different positions and sometimes using the foot pedal and getting comfortable can be a pain but that comes with experience . you have to vary the heat quite a bit as your going around the tube to maintain and even appearance. that will come with time.try to do some fillets that look like this first here is a pic.

[dyn88]

call me mean if you may but the welds on those tubes "look" incredable, but at a close look you will see quite a bit of undercut, which is a good place to create a weak point.

[T_Bone]

call me mean if you may but the welds on those tubes "look" incredable, but at a close look you will see quite a bit of undercut, which is a good place to create a weak point.


Hi dyn88,

I think it's the camera angle that's making them appear under cut. A close up look may give a different opinon tho :D

As a CWI, I can't see anything there that would lead me not to certifiy the welds as a small amount of undercut is allowable according to code, although not desireable.

[HAWK]

Hi dyn88,

I think it's the camera angle that's making them appear under cut. A close up look may give a different opinon tho :D

As a CWI, I can't see anything there that would lead me not to certifiy the welds as a small amount of undercut is allowable according to code, although not desireable.

It may be the camera angle. Most times pictures don't do justice to TIG welds. I do a bunch of Sched 10 pipe for sprinkler systems and rarely get undercut. However, if it happens it's trashed. We don't even waste the time to pressure test.

[dyn88]

in pic two It shure does look like undercut, What percentage of the weld is "allowed" to be undercut? I was always under the thought that undercut on any flame hardenable steels was a guaranteed spot for a crack to start. The haz on those wwelds also looks perfect.

[Billet Benny]

Nice tigs welds are nothing but two things. Proper fundamentals for the weld at hand and practice. That's it. Fundamentals includes all the things you know you should be doing. When you learn to use proper amperage, work angle, travel angle, arc length, travel speed, etc. etc. you only then begin to tune your beads to your liking through practice. The fundamentals can be cheated but you'll learn what other fundamentals change to keep things in order once the basics are down. Beyond that and practice that's all it is. I believe welding is half prep, half knowledge, and the rest is skill. =] Looking at the pictures you posted they were probably made by adding filler after each small movement forward of the torch. This "dab" method as everyone calls it is the most common for joints like that.

As for drilling vent holes in tubes, I only find it necessary on tubes that are already sealed up from welding and are in the thinner ranges of wall thickness. When it does blow back out it's nasty.

[T_Bone]

in pic two It shure does look like undercut, What percentage of the weld is "allowed" to be undercut? I was always under the thought that undercut on any flame hardenable steels was a guaranteed spot for a crack to start. The haz on those wwelds also looks perfect.


Generaly .01 deep at .16% of the total length of weld. New code could be different as I havn't recertified for a few years as I retired. :D

If it was indeed undercut, code would allow for the repair of the undercut.

[weldaround]

The only way you will produce nice welds is pratice (lots). I never was a big fan of dipping the filler weld. I've always like free hand, draging the cup or if you got lots of room to move walking the cup. A combonation of those can be good to like free hand the root, drag the fill pass and finish off with walking the cup for the cap. As far a undercut goes you have to play by the code (which ever code that is) in your case if there just some roll bars then if you like take a small file and blend it in, if there boiler tubes then I wouldn't try that I'd fill them in. If their sch.40 check the code your working under (maybe they will let you have a 1/16"). Different ways to tackel it !!!!!!!!! When it comes to blowing a whole. If you do just keep welding and once your done let it cool down and go back and repair the whole that you made. The reason you blow a whole is because, the air in the tube is expanding and it has no where to go so it builds up and comes through the weld puddle but, once you blow a whole then the air has somewhere to go and your problem is solved just keep on welding. Let your piece cool down and fill the whole ! I don't clame to know it all but that's my two cents


John................. ;)