how thick do you weld with your wire feed / mig?

[lostcause]

i don't have experience with a lot of different welding techniques and/or theories, but to be honest, they really aren't completely relevant to most of what we need here, though it certainly is nice to understand other procedures. in the case of welding pipelines or pressure vessels, you have a different condition you are trying to satisfy. i don't know of any tbn members building pipelines or massive cogens in their back yard, so i suspect the welding skills required here are almost exclusively general fabrication.

For all pressure welds, every welding specification I have ever seen requires minimum of 2 passes regardless of the base metal thickness.

Welders generally speaking,don't go into a weld with the thought of having to make it in one pass,you use multiple passes as needed,if its thin,than one pass might be enough,if its thicker,you might need two or more

i worked for a fairly large steel fabricator for quite a few years - ballpark of 75,000-100,000 tons of fabricated structural steel a year over half a dozen fab shops. as a point of practice, you tried to avoid multiple passes at all times. certainly, there are conditions where it was not possible, but for most cases it is possible. we worked with a known load - either calculated from known forces, or based on the capacity of an incoming member. connection material was then sized based on this load, along with the size of welds and/or number of fasteners. due to the nature of the load, it is quite common to have thick material, but not require a large weld to satisfy the connection. we worked with a theory that the welders could consistently provide a 5/16" fillet in a single pass (3/8" fillet with saw), based on past experience. if you have a 24" long piece of material and a 5/16" weld did not satisfy the load, but the same weld over 30" would, then we would redesign with 30" long material. since enlarging a fillet past single pass generally will take at least 3 passes, it was more economical to use a little more material than to triple the labor. this can't be done when the material size can't be altered, such as pipes and fixed-size structural conditions, such as beam flanges.

sadly, things have digressed more. i still just wonder why i see so many people on here that own 200a+ wire feeders but only use them on light material, where i would think a 120v welder would be plenty.

 

[LD1]

So far I agree with most of the posters here. When I was young, I grew up on a stick welder. An old craftsman with the plug in cables to change amperage. Still have it but also have a 225 linde 220v. I'll take it over the sitck everytime no matter how thick. The only time I even use the stick anymore is only a very few reasons.

1. Hard to reach areas that make it difficult to get the mig gun in there. An example off the top of my head is welding the underside of spring perches and hangers on axles when doing a swap or something.

2. Very dirty metal that is in a bad area to get a grinder to clean well.

3. If I only have acess to the stick. (if the mig is at dads shop and me at home ora vice versa)

I have welded 1/2" with a single pass before and have yet to have anything fail. But Just as a home hobbier, things tend to be over built anyway.

The thickest I have welded was 1.5" single pass. That was the pivots welded to the bottom of channel Iron when I built my dump bed (which was all done with mig) and it has hauled and dumped several 6500lb loads of stone.

The 12 x 26lb I-beams spanning the 30ft of my garage to support the upstairs and motor pulls was done with this mig. V-grooved both sides and then welded both sides in a single pass. Then added 12" x 12" x 1/4" plate to each side of the web. Have not railed yet and the has yanked/moved two motors and moves my 750lb snow plow around frequently as well as the storage upstairs.

Also Had a Hook eyelet that I welded on the iron pipe to erect my chimney. It was either 3/8 or 1/2 thick and 2.5" long. Iron pipe was 5/16" thick. No v-grooving, just cranked up the mig and spray-transfered. Had no problem at all lifting the 1100lb (12" x 24' long) chimney in place.

There are quite a few other examples but if someone has got a 220v mig welder, why use a stick?? Other than the obvious like i mentioned. If done right, it is just as strong. And for the average joe who can only weld with a MIG, A good sound mig weld will beat a "poor" quality stick job done by a first timmer who was told he HAD to use 7018 rod other wise it wouldn't hold together.

Which reminds me of another point along the lines of this thread. Whats with everyone always saying 7018 this and 7018 that. Most guys on here aren't pros, and dont weld that much. And 7018 is hard to weld with. I always reccomend (and use myself) 6013 and 7014. They weld super smooth and great for a noob. And I have never had a weld fail that has been welded with either of theese.

OK Im done for now.

 

[gauthier]

Yeah,welds are made of different parts,if you know this you will know that many times you can't put it all in one pass. Groove welds,pipe/plate,are basicly all like this,even many fillit welds. Somes you put the root in[if your stick welding] with say a 1/8,than fill with a 5/32,than cap with even bigger rod. Sometimes you put root in with tig than fill and cap[as needed] with stick.Sometimes you mig root and stick out,or flux core out,different processes can be better at different parts of a weld than other processes,sometimes you even backgrind the root,and back weld it,[weld it on other side].

This is the difference between how a welder sees a joint[weld] and how a mig wire burner sees it. This stuff of how they sell mig machines to people[this one will weld this thickness,this one will weld this in one pass],is just a salesmans way of trying to sell a welding machine to someone who knows little or nothing about welding,about the stupidest thing to me,that I ever seen.Theres way more to welding than just buying a mig machine that will weld a certain thickness in one pass,thats not how you weld,and even if you could weld say,3/8th in one pass,most[about all] the time,you wouldn't want to be that hot,flat fillit would be[the only time] you could do that,if,you was actually welding on something that thick or thicker.
Its about the size of filler[wire or rod] that you plan on using that tells tou how many amp machine you need,and the smaller the filler,the less powerfull machine you need,and visa versa. In these fab shops[bridge,ship ect],they are after production,the way you can do this,is keep all welds flat when welding so's you can use a bigger filler and put down a bigger weld in a pass,do the sme thing over and over,and you can use less skilled welders in many of these type jobs,which cuts down on your cost,plus have the process semi or automatic. But for most other things,precision welding,pipewelding,homeowner,repair welding,thats not how you go into it,of course you need production,but you can't treat it like welding bridge girders.

 

[Transit]

A major problem with MIG is that there are a lot of units that are over rated. They are built as cheaply as possible, striped down, no capacitors to store energy, bosting that 120v unit to be able to weld 1/4 inch on a single pass and at best can do 1/8 inch. This is what gives MIG a bad name and makes one gun-shy. Some of the specs read, 250 amps max, 180 amps @ 3% duty cycle. I can generate more heat rubbing my hands together.

 

[yomax4]

It was asked, Why have a 200+ amp machine instead of the 90 amp when
1/2" Welds seem to hold fine. In my case and what is typical, With a larger amp machine you can run larger wire ( .045, 1/16 ) and run it Hot as to get great penetration and sound welds. I have owned dozens of welders from 80 amp - 400 amps. Often I would grab the 115v unit for tack welds or thin material But for 1/4" and up I always crank up the heat and really burn it in. I have had friends weld up trailers with the 115v units but I would never borrow one to haul any of my toys. You could of course pre-heat your material prior to welding with the 115v but it is a pain to weld on pre-heated material. Lastly, Larger welders can be turned up and the wire speed increased to hit some very nice travel speeds.

 

[lostcause]

It was asked, Why have a 200+ amp machine instead of the 90 amp when
1/2" Welds seem to hold fine. In my case and what is typical, With a larger amp machine you can run larger wire ( .045, 1/16 ) and run it Hot as to get great penetration and sound welds. I have owned dozens of welders from 80 amp - 400 amps. Often I would grab the 115v unit for tack welds or thin material But for 1/4" and up I always crank up the heat and really burn it in. I have had friends weld up trailers with the 115v units but I would never borrow one to haul any of my toys. You could of course pre-heat your material prior to welding with the 115v but it is a pain to weld on pre-heated material. Lastly, Larger welders can be turned up and the wire speed increased to hit some very nice travel speeds.

actually, i never asked why use a 200a instead of a 90a. i asked why i see so many people here that have a 200a+ wire feeder, but use a 200a+ stick whenever they go past 1/4". i just wonder why they bought a 200a+ wire feeder but and never run the heat past half way. if they weren't going to use it for anything thicker than 1/4", why spend $1500 when a $500 120v would do the trick. what don't they see fit about welding slightly thicker material with wire feed?

i use what i listed because it is what i have, not what i would choose. i guarantee i am pushing the envelope at times, but again, i will continuously say that it is not required to get 100% penetration on 99% of the welds that we (tbn members) use on home projects. trailer members are more often sized based on a bending condition and not an end shear condition. same with most section sizes and plate thicknesses in machinery. you do need to generate enough heat to assure that the materials fuse together, but complete penetration welds are seldom needed.

i believe that up to 1/4" is a good range to weld with a 120v welder, but i have used one far past that at certain times. is it the best choice? not really. do i worry that the weld will fail? not really. i expect the steel would buckle before the weld would give. sure, wire feeders may be the redheaded stepchild to some professionals, but anyone building a trailer or piece of small farm machinery rarely (if ever) has a joint that requires tig. at some point i intend to learn about and try tig welding, but then i'll probably only ever use it for the area where it is best suited - high strength welds on thin materials.

 

[MESSMAKER]

actually, i never asked why use a 200a instead of a 90a. i asked why i see so many people here that have a 200a+ wire feeder, but use a 200a+ stick whenever they go past 1/4". i just wonder why they bought a 200a+ wire feeder but and never run the heat past half way. if they weren't going to use it for anything thicker than 1/4", why spend $1500 when a $500 120v would do the trick. what don't they see fit about welding slightly thicker material with wire feed?

i use what i listed because it is what i have, not what i would choose. i guarantee i am pushing the envelope at times, but again, i will continuously say that it is not required to get 100% penetration on 99% of the welds that we (tbn members) use on home projects. trailer members are more often sized based on a bending condition and not an end shear condition. same with most section sizes and plate thicknesses in machinery. you do need to generate enough heat to assure that the materials fuse together, but complete penetration welds are seldom needed.

i believe that up to 1/4" is a good range to weld with a 120v welder, but i have used one far past that at certain times. is it the best choice? not really. do i worry that the weld will fail? not really. i expect the steel would buckle before the weld would give. sure, wire feeders may be the redheaded stepchild to some professionals, but anyone building a trailer or piece of small farm machinery rarely (if ever) has a joint that requires tig. at some point i intend to learn about and try tig welding, but then i'll probably only ever use it for the area where it is best suited - high strength welds on thin materials.

Well written response!

 

[FlaDon]

I deal with inspection of xray quality pressure welds everyday with my day job. Most of the small sized 3" OD and smaller pipe welds on this job are done using GTAW (TIG). SMAW is not used till the diameter gets to be 4" or larger. The biggest problem with them failing xray is the welder running too cold and getting cold lap on tie ins or between passes. If you dont have the amps available or just dont use the correct setting then it is easy for even a skilled welder to cold lap the weld. This means that the weld metal did not fuse to the underlying metal whether it is base metal or weld metal. If you do not run the right amperage with either GMAW (MIG), SMAW or GTAW for the size of the filler pass, you will get non fusion. With MIG this is usually evident in the toe (side) of the weld but it could also be covered over and look really pretty on the outside and yet underneath the weld metal may just be laying on top with only partial fusion to the base metal. You will usually have much better welds if you carry a smaller size fillet and make multiple passes especially with the low amperage machines. For all pressure welds, every welding specification I have ever seen requires minimum of 2 passes regardless of the base metal thickness. There is no limit to how thick the material that can be welded with any machine if you limit the weld size to the applicable amperage limitation of the machine. Most qualified welding procedures for GMAW, SMAW and GTAW limit the size of filler passes to 5/8" maximum and you need lots of power to make one that size without cold lapping the metal. The other problem is with porosity which can substantially weaken a weld. For Pressure piping 1/4" thick the allowance is .062" for one single pore, anything larger is rejectable. Anyone want to try their hand with a MIG weld for this. By the way, any non fusion is cause for reject no matter how small.

Even when welding inside a boiler firebox, 5/8" weld would have been huge with a stick. But there is no way I would trust a MIG weld on the dirty 5/8" thick firebox steel that has been exposed to oil soot for nearly 100 years. One of the things people forget about is it isn't just amps that count. You also have to figure in voltage. 200 amps at 32 volts is not the same as 200 amps at 72 volts.

 

[kcender]

Hey guys. Just thought I would give my opinion on this subject.I make my living as a welder in the ship repair business for the navy.All of the welds we do have to be done right the first time.I have welded steel,stainless steel,aluminum,brass, copper,cast iron,and many other types of hardened steels.I use TIG,MIG,FCAW,and stick.In the repair business I come across different situations every day that require welding.Each job has to be evaluated and a welding process determined based on experience.No one process can be used for everything.Having something not break is not a true test of a weld.I realize most TBN'ers are backyard guys but there seems to be a lot of confusion over welding.If I had to weld something that my life depended on I would use stick.It may be slower but it is as strong as any weld if done properly. As far as single verses multipass welds each job has to be evaluated on the situation. Multipass welds may be more foolproof but they also cause more distortion and stresses,provided the total weld size is the same.As far as machine size it is only as good as the power going into the back of it which is not always the same depending on how good the supply is coming into your garage.As for welding half inch plate with 90 amps I certainly wouldn't do it regardless of joint preparation.

 

[LD1]

.If I had to weld something that my life depended on I would use stick.It may be slower but it is as strong as any weld if done properly.

What about your car/truck that you drive everyday that was more than likely mig welded by robots, or the jackstands you use to crawl under that car to chainge the oil, they were probabally mig welded too.

Everyone makes stick out the be superior to mig in terms of strength. That is not true if the mig is done properly. One of the main reasons stick is used in construction is portability and cleanleniess. Mig is not as quick as stick if you are dealing with dirty steel. By the time you prep it, it coul have already been sticked. And it is a lot easier it add length to the stinger and ground cables on a stick. Imagine trying to mig with the welder a few hundred feet away:confused2: