welding structual beams

[LOUIE2180]

hi guys

I need to do some welding on some beams which are going to be used in the construction of my house.

What i want to know is it acceptable to use a mig welder to do this? and if so what wire do i need to use? All i have on my eng drwgs is to use electrodes that comply with AS1553.

I have a 205 amp mig at home hence the reason i want to do it with mig.

Any imput would be greatly appreciated,

thanks louie.

[gallegos]

You probably want to have a look at AS1554.1 which details welding requirements for structural steel. Private message me if you would like a hand finding a copy.

Depending on how thick the material a 200A welder might be a bit small... You probably still do it but you will find yourself spending most of you time waiting for the welder to cool down so you can do some more.

Do you know if you are going to have any problems from the council or builder doing this yourself? I am planning to do the same when I build in a few years but always wondered if this would be a problem.

[Dave J]

Hi louie,
If you have a look at this post
https://www.woodworkforums.com/f65/ho...photos-113771/
I welded it all up with a 195 mig transmig. I just made sure that all joins were heavily beveled both sides for good root penetration, no trouble with overheating it at full amps.
As far as council, I am not sure on there codes for doing it your self, sorry.
Dave

[DoctorWu]

I did my own building job as an owner-builder and there was quite a bit of structural steel involved, most of which was pre-fabricated off-site but with some joining to do. My engineer, who is by the way very competent, inspected it all and ticked it off. I didn't do the site-welding but the bloke who did used a Lincoln that was about the size of a small lunch box and weighed not much more than a couple of k's. So, ideal for carrying across a roof etc.
Disadvantage of a mig for site welding is the gas can be dispersed if there is enough of a breeze.

[Com_VC]

I'm always wondered if you would need to have a ticket for this?

[Bloss]

If the beams are engineered then your engineer will have to sign off on all parts for council approval. So if he specced beams and that they needed to be welded according to the standard (as he no doubt did) then his sign-off only applies if they are done to that standard.

I'd be checking with engineer and council before DIYing.

[danielhobby]

Hi all,firstly a mig flat out at 205 amps is really only good for material thickness of approx 10 mm,no matter how you might prep your joints,and only beams up to 250ub fall into this size.you make no mention of size so can you check that.Secondly the person making the joint must be an "experienced operator",able to understand the correct procedure and shape/size of prep and then the welder must be able to read the weld as its happening so as to ensure pentration with parent metal,this last point is the largest problem(in my opinion)with small migs and inexperianced welders.Also the position of the join in relation to the length of beam and load point is crucial in looking at wether it can /should be done to save a few hundred dollars on a beam.regards Danny.

[NewLou]

Gidday

Typically -Mig Wire electrode type classification es6-gc/m-w503ah (DEsigned to be used with Hot rolled or cold rolled plain carbon steels) would be used for this kind of Job................

Generally structural steel is welded using 1.2 wire @ 28 Volts (Somewhere between 250-280 amps) This ensures a good full penetration Weld usually laid down as a 6mm fillet.

At a guess id say your running 0.9 diameter wire thats usually good for 16-24 Volts (70-200AMPS) Its important to remember that load bearing structural welds need to be done right!!!

Let me know if you need anymore information!

Regards Lou

[LOUIE2180]

Thanks guys for alL your replies.

The extent of the welding required is to weld some 75x75x5 square tube to 12mm base and a couple of 300 PFC with some 100x100x10 angle stitch welded @ 75/150. On my engenering drwg it only makes reference to using MMA electrodes. This is where the confusion lies.

Also im a fitter by trade with mig welding certificate and i do a fair bit of mig welding at work.

Thanks louie

[NewLou]

Sounds like your Mig hasent got the balls to do the Job to Spec! I wouldnt do any of these welds under 26-28 Volts................ However on a positive note youve obviously got access to some grunty 3 phase Migs @ Work..............

In the circumstances your working in Mig wire lays down stronger than Stick............ Your workshop Migs I'll be setup n ready to go ...........

If i was doing this job @ Work (Im a Mig welder in heavy construction) Id setup @ 28 Volts make sure your base plates are pre heated @ least till their warm to the touch then lay down your welds...................

At work we wouldnt do any prep for fillet welds on base plates other than a pre heat for any base plates 12mm & Over..............

You should be able to rip through your stitch welds without a drama ..............

Hope it all goes well!!!!

Regards Lou

[spooled]

I do quite a bit of structural fabrication for houses/buildings and I have to say NewLou is on the money. I weld most steel at around 30v with 1.2 wire. Not sure exactly how many amps that is but I know I can't get the weld size and pen required with my single ph machine, which is rated at 250a but is prbably more like 210-220a.

As far as standard goes for the engineer, the welding would have to be done to 1554.1. He'd be specifying stick welding because he's probably got a generic spec that he always uses. The process used won't effect the standard, e.g. I use MIG in the shop for fabricating and stick for on site welding of posts to beams. As long as welds are the correct size and standard it doesn't matter what you use.

[the fabricator]

before welding the beams on your house, and im not assuming your a bad welder, but it really pays off to do the press test. weld two small samples( 50mm x 100 mm x 10mm thick) in the fillet position and lay down your best weld, take it to the nearest hydraulic press and crack it in on itself. the weld should rip out the roots of the weld completely as even the best looking welds can just be molten metal on the surface.

i recomemend everyone do this, will really make you surprised at how hard it is to lay down a strong weld.

edit: just read that Louie has done a ticket in mig, so he probably has them down pat

[.RC.]

Buggered if I know but I thought smaller welders are capable of this sort of work, you just need to run more then one bead...

To give you an example... A saw a ticketed welder one weekend weld up a piece of metal that had been ripped from the bucket of a 40 tonne excavator.... He used 4mm low hydrogen rods, and filled in the V'ed out grrove that was something like 600mm long and 50mm deep...He put a lot of weld into it and it was a successful fix...

Where time (and money) is not an issue I cannot see how a smaller welder running smaller beads cannot suffice for this job... it is different on a construction site where you do not want to be paying someone $35 an hour to run two beads when one with a bigger machine will do...

[DoctorWu]

Buggered if I know but I thought smaller welders are capable of this sort of work, you just need to run more then one bead...

To give you an example... A saw a ticketed welder one weekend weld up a piece of metal that had been ripped from the bucket of a 40 tonne excavator.... He used 4mm low hydrogen rods, and filled in the V'ed out grrove that was something like 600mm long and 50mm deep...He put a lot of weld into it and it was a successful fix...

Where time (and money) is not an issue I cannot see how a smaller welder running smaller beads cannot suffice for this job... it is different on a construction site where you do not want to be paying someone $35 an hour to run two beads when one with a bigger machine will do...

I've been taught that a number of small welds is better than one larger weld. Less stress in the weld site."$35 an hour"!? You're lucky if you only pay that!!

[NewLou]

Erm thats where a lota blokes get it wrong..................

I can lay down 25 neat stringer beads that looks the ducks guts n try to fill or fix anything! .................but if Ive got Cold Lap or the weld isnt Hot Enough (Through not using enough Volts/AMps) or not prepped correctly................ then the weld will fail!

Mig welders work differently to stick.........................

In a nutshell if your rig hasn't got enough balls to lay down a full penetration weld then u shouldn't be using it to weld structural jobs (ie: Be able to pump out at least 28VOlts) smaller 2 phase rigs cant do this.....................thats why U never see them being used in industry ...............

SMaller Rigs have there place but should never be used in a structural situation where a failure could mean death or injury !!!!

Regards Lou