Mig uphill? downhill?

[bscott]

hi.. Im kind of new to mig welding. Have been trying to learn on my own. I have been practicing a lot, but i havent been able to make a good uphill bead. If i turn the voltage and wire speed real low it seems like i can get closer to doing it. Most mig welds i have seen are downhill. is that the most practical thing to do? Am runing a hobart 210 welder with .035 solid wire and 75/25 argon mix. I have been following the door chart for wire speed and voltage. with a little experimentation. Any suggestions would be appreciated. Thanks.

[Sandy]

It's called 'vertical up' and 'vertical down'. There seems to be a consensus that vert up with mig is difficult at best. Sooo vertical down appears to be the most common practice. Problem is that the better penetration is with vertical up. Verical down just might end up be a hot glue job without proper care and attention.

So much really depends on joint prep and joint type. There were a couple of discussions on this board about this very thing however. Not too long ago either. Do a little looking aound here and if you can't find what you need holler.

[Sandy]

Try these.

http://www.weldingweb.com/showthread...light=vertical
http://www.weldingweb.com/showthread...light=vertical
http://www.weldingweb.com/showthread...light=vertical
http://www.weldingweb.com/showthread...light=vertical

[keith]

Vertical down is no good as a structural weld as penetration is very limited making the weld weak and prone to failure under load. vertical up is hard to do but with lower amps and correct technique (and practice) you'll get it.
when welding feed in the shape of a upside down u eg. from side to side but higher in the middle. try to keep the pace steady and even and hold the handpiece so the gas shroud faces uphill (hand lower than gas shroud)

[TxRedneck]

Scott, personally I have welded in many fab shops over the years that are mig welded. Solid wire has no problem with downhill, downhand, or vertical down, all depends on who your talking to and region you live and work. It is true that downhill has less penetration. However, that can be compensated for and it is used in a lot of structural applications not requiring load specification and such. For example of this, many smaller buildings, tank structures, silo structures and other similar applications are downhill welded. Oil rigs, many applications in siesmic regions, bridges, much more than a shopping complex ect would need uphill welding, but also typically you will find inspection process to boot. In most of your manufac secter though you will find the downhand to be preferred. You ask why? For one you can weld much much faster. For two, its easier. For three, its just accepted. With uphill its all about the physics like is the downhand. Uphand heat rises. As the heat rises it preheats what your fixin to weld. Therefore you have more metal closer to that melting point before it wants to fall back off the joint. With downhand you start at the top. For this reason heat rises but gives you no benefit. You must raise your heat settings so you can account for this. typically you dont need to raise your heat much if any from flat, but with uphand you must lower your heat because as the heat rises it preheats and reduces the amount of heat necessary to get penetration. You can get much faster weld speeds for downhand than uphand because of this. For most around the house and even on the farm applications this is adequate. Solid wire will do this, not flux. Flux tends to drip down into the puddle and get flux inclusions. 7018 stick welding exhibits the same problem. You can weld a 5P down for root and a 7018 still needs to be done uphand. Hope this helps.
CHRIS

[bscott]

Thanks for the help guys. i"m gonna keep practicing. But i'm not afraid to downhill in the meantime. Ive always preferred uphill with 7018 but it sure seems harder with the mig. I guess vertical down would sure be the way to go on really thin stuff?

[TxRedneck]

definately scott...you hit the nail on the head. Thin gauge should always be done fast and down. It will also help with distortion.
CHRIS

[Sandy]

Originally Posted by bscott

Thanks for the help guys. i"m gonna keep practicing. But i'm not afraid to downhill in the meantime. Ive always preferred uphill with 7018 but it sure seems harder with the mig. I guess vertical down would sure be the way to go on really thin stuff?

Loaded questions One of the unspoken issues is giving the go ahead signal not knowing who you're giving it to, but yes, for that thin tubing and such vert up with a mig will probably end up being a disaster. Sounds like you've got a handle on it.

Poor fusion is poor fusion whether it's up or down and as TX says most vert ups are in load bearing situations, single pass, so-on. Minimum disruption of the parent metal. In that case they'd probably be stick anyway.

In my mind a guy needs to be able to do both well. Just wish mine weren't so darn oogly. A crappy vertical up is going to have some decent penetration but also a bunch of stress risers. Might not be the best thing for a flexing trailer frame for example. A vertical down might be neat in appearance but not much more than glue if all a guy was doing was outrunning the puddle instead of controlling it. That might pull loose on a flexing trailer frame. So I guess it's more an issue of how conscientious you are and how good your welds are. Not how you got them there or how pretty they are.

I'm a hobby guy so take everything I say with two grains of salt.

PS
You're not going to find much info on vertical up mig out there anywhere. After you've tried you know why.

[Robin Hood]

You know it's funny, I was telling a buddy that stopped by my shop today that ask the same thing. Back in the late 70s early 80s in the shipyard you were not to run anything down hill, unless you were looking for a pass to the gate but it was called "short arc" and I still use the procedure to this day. But to answer your Question you can run down hill with .035 wire and almost break threw 1/4" plate, I even run down hill on 1/2" plate and have never had a weld fail, but if you want to practice your vertical set the heat just a little lower than you would for a flat weld (with 75/25) note that with .035 you will be looking at a filet of 1/2" to 5/8" just start and move side to side climbing slowly counting,123 123 123 123 on the way up on the sides.
I hope this helps.

[Robinson Welding]

Generaly my understanding is that vert down is used for parent metal under 1/4". This can change depending on a companies own weld specs. I worked for a locomotive plant where vert down was only used for non structure parts such as body panels. THe majority of work was solid wire MIG and all of us frame welders had to pass a x-ray test preformed vert up on 5/8" plate. Basicaily what I am getting at is a perfect weld free of any inclusions can be preformed vert up with solid wire MIG.

[TxRedneck]

Robinson, I agree you are completely right in what you have said. However, I ask you to give us your input as you obviously have some on whether you think this gentleman should run vert. up or down, and under what conditions would up be needed vs down. Also hes looking for some technique advice. I have done sawmill equipment in the uphand with solid wire, flux core and metal core all requiring inspection, and some was xray, which was stupid I thought. haha. Ok thanx pal.
CHRIS

[Robin Hood]

As a rule of thumb, If it not's thick enough to short arc up hill, it's thin enough to mig down hill......

[Robinson Welding]

As far as technique, Robin Hood has it well described for vert up. This is a small weave and with a weave, holding the sides for a short time allows the metal to wash in, preventing the molten material from flowing to the center. Keep practicing and good luck!

[Robin Hood]

(Robinson Welding) Thank you.....One more note. If you see a sag.....count faster..........

Mike