welding question

[wedge40]

I'm going to ask this just for general knowledge of welding. Using mig welders in particular. If I'm looking at Mig adds, I notice they sometime mention being able to weld a certain thickness of steel, 1/4", 1/2" etc. Is the what it's capable of welding in a single pass? And will multiple passes be as strong as a single pass.
Just wanting a little info about welding thats all.
If you were going to weld 1" and 3/4" steel together, would mig give the same results (strength wise) as a stick welder.

Wedge

 

[weldingisfun]

I think you will get answers to your questions at these sites:
Knowledge | Lincoln Electric
Miller - Welding Discussion Forums
Weld Talk Message Boards - Powered by vBulletin
Take your choice.

 

[digger2]

I'm prob. going to get an argument on this,but .......I've been a welder for 33 yrs. and i do know a little about it.
As far as the strength of mig welding compared to stick,i think there are alot of variables,and there really is'nt space here to explain it all.I've seen mig welds done with a machine that was set up wrong that you could knock the weld apart with a hard blow from a hammer.Of course i've seen the same thing with some stick welds,like at the hands of a beginner.
With proper prep. and procedure,a mig weld is usually strong enough for anything.BUT..if i build something that i absolutely,positively want it to hold
like something my life depends on,i'll stick weld it every time.
Sheet metal is one thing,but anything 1/4" and up,i'll stick it.Stick welding has more penetration than mig,and i'll argue that with anyone.But mig does have its place in the welding world,mostly for speed and appearance.I have nothing against mig,i have one myself,along with a stick machine and a tig.
All these machines have there place,it just depends what you are doing.
Everybody has there opinion,this is mine.......Digger2

 

[ray66v]

Digger is right, yes you can weld thick metal with a mig. But, it will require many passes and heat build up can be harder to control (think warpage). With proper beveling and sometimes preheat I have welded some really thick steel with a mig. Keep in mind unless you buy a heavy commercial machine you will find the thermal overload protection shutting you down as you hit the end of the duty cycle. (This can really slow things down). Migs are best suited for sheet metal work, (easy to control in tight places and making critical plug welds). If you want to do a lot of heavy fabrication work, though it may take a little more practice to use, a stick welder will be more efficient and can be much faster. There is a pretty big difference in stick welders as the price in creases. A good machine that can weld with DC and has an arc starter would be ideal but, your gonna pay for those. If you don't mind how "pretty" your welds look you can certainly get by with a basic AC machine.

 

[Sully2]

I'm going to ask this just for general knowledge of welding. Using mig welders in particular. If I'm looking at Mig adds, I notice they sometime mention being able to weld a certain thickness of steel, 1/4", 1/2" etc. Is the what it's capable of welding in a single pass? And will multiple passes be as strong as a single pass.
Just wanting a little info about welding thats all.
If you were going to weld 1" and 3/4" steel together, would mig give the same results (strength wise) as a stick welder.

Wedge

Properly done...by a fully compentant welder..a weld done with a "wire fed welder" ( MIG or using fluxcore wire) will be every bit as strong as the same sort of weld done by a stick machine...PERIOD

Any wire fed maching fully capable of doing 1/2" steel in a single pass is going to cost you a WAD..and I do mean a WAD. Capable of doing 3/4"...and or 1"..in a single pass...plan on trading the deed to your property for it cause " you aint got enough $$$"

A multi pass weld certainly CAN BE as strong as a single pass..BUT..the chance for "bad spots" increases GREATLY.

My own usage is steel 3/16-1/4 with the occasional 5/16's thickness..and I bought a wire fed machine capable of doing 1/2" thick ..single pass..using FLUXCORE wire ( it penetrates deeper..and I have to work outside..where the shielding gass for MIG would be blown away)

If you intend much 3/4-1" stock welding..buy a large stick welder ( I prefer DC stick machines) and a stack of large rods.

 

[Sully2]

...
Sheet metal is one thing,but anything 1/4" and up,i'll stick it.Stick welding has more penetration than mig,and i'll argue that with anyone.

"Penetration" is exactly that..penetration! Any welder of any sort..capable of 100% penetration will create equally strong welds. In fact.."some" welding wire used for MIG machines have HIGHER tensile strength than rods made for stick machines. Hence a properly made weld using that wire would be STRONGER than the same weld using a stick machine

 

[ray66v]

If I may speak for digger; I believe what he means is there is a propensity for mig welds to have "cold starts" particularly on thick metal. A Cold start will limit penetration and sometimes in the case of a small weld area, can leave you with a weaker weld than if it was done properly. A large enough mig with heavy enough wire and or proper preheat, can limit and or eliminate this problem. Using a stick welder with a good size rod is the best way to, in most cases, get a good weld going the fastest, particularly at home on heavy material.

 

[Mickey_Fx]

I'm not a pro by any stretch but I have to side with Sully. IMO operator knowledge and proper setup has a bigger impact than the source of heat.

Don't know how many of you watch either HOW'S IT MADE or SOME ASSMBLY REQUIRED but in the past week they had a segment on a company that makes HUGE earth moving equipment. Many welded sub-assys made from thick plates fixtured and welded by robot welders. No stick welders in use.

For home equip and what the typ person can afford, a stick welder suitable for heavier work is more affordable. YMMV

 

[wedge40]

Wow, Thanks for the replies.. I didn't think about peoples "preferences". People keep mentioning preheat? I'm guessing this would be getting the two pieces of metal fairly hot before starting to weld (MIG). Maybe in the red or orange range. Just a guess.

Wedge

 

[ray66v]

Preheat is not at high temperatures, it is just a kick to get things started faster. The preheat can help stop a large mass from sucking all the heat out of the weld as you start it. I guess 500 degrees will usually do the trick. Keep in mind that if you are working with hardened steel you do not want to use a lot of heat on it.
I have seen structural steel being welded (vertical beams on a skyscraper) where they had propane rosebud torches on two sides across from each other warming. And two welders were welding on the other two sides across from each other.
Beveling the edge of the steel so that the thickness your working with is within the ability of your machine is another way to get a good start. Then as you make additional passes the metal will be heated from the previous passes and the welds, (especially from inadequate equipment and will flow better). A good welder can do this with a cutting torch and produce something very quickly that would take forever any other way. (I can't do it).
Welding is an art and is an extremely complicated science if you break it all the way down to the textbooks. But, like most things if you know the basics and have someone who you can ask for help when you need it, you can get by most of the time.