Thread: welding thick steel sections

Hi everyone,

I have some serious/critical welding jobs coming up in some thick steel sections and was looking to tap into the experience on the forum for some advice.

As to my background/experience I am a farmer and done a moderate amount of mostly fabrication type welding. I have a 275amp 3 phase DC welder as well as a 250amp single phase MIG. In the coming months I am fabricating the steel for a large industrial shed on my property. This will involve erecting a 5 tonne overhead travelling crane in the shed.

This will involve cutting and welding the brackets for the crane supports and also cutting and welding the crane beam itself (to fit the dimensions of the shed). The shed columns are 310UC158 and the crane runway and crane itself is 610UB125 sections (both have 300mm PFC welded on top for extra rigidity). Obviously welding the crane back together and welding the 610 UB brackets to the side of the 310UC will be very critical.

So now I am considering whether the welders I have are up to this job. I have a bevelling machine to help prepare the edges and I realise you can make multiple passes but considering these are welds that cannot fail do I need to consider getting a bigger welder to make the job easier and safer. If so what size? I live in a pretty isolated area so no local welding shop to wander into and question.

I am happy to buy a bigger welder if it is necessary but what size? What size wire should I consider? Gas shielded flux core wire or solid wire? Any other considerations?

Thanks for your help.

Mark

PS all comments will be taken on the all care no responsibility principal

I'm pretty sure you can get Satincraft in 4mm rods?

I suppose on whether you are time poor or not.

Using something like a #22 iron power electrode 4mm maybe 5mm if really thick sections might be the go.

To get the job done quicker but at greater consumable expense probably something like a 400 amp MIG running flux cored wire will get you there.

I personally would not touch solid wire as I have seen way too many extremely nice perfect looking welds that have zero fusion with one side due to incorrect settings and procedure.

I think when I helped build the neighbours shed we went through two or three 12.5kg coils of flux cored wire. That was put through a lincwelder 225 connected to a LN25 wire feeder. It could only do CC so was not the best but got the job done. We were originally thinking of using Ferrocraft 22 stick rods, but it was simply too slow.

I am not sure why but MIG welders and stick welders cannot be compared amp to amp capacity. For example 250 amp single phase 15 amp plug mig welders are not uncommon. You will never find a 250 amp stick welder with a 15 amp plug on it. Our old transformer 140 amp stick used to melt 15 amp plugs after lots of heavy use. My 250 amp MIG never has.

Hi Richard,
Yeah you are definitely right about comparing stick vs MIG amperages. My 3 phase DC 275amp stick welder would be twice the welder my 250amp single phase MIG is. If it was a normal farm shed these would be fine. Some of this sheds welds will involve joining 25-40mm steel at right angles and need to hold 10-15T. So can't be too careful.
I have started looking for a 400-600amp 3 phase mig. Some of these have a serious hunger for power. Most suggest a 35 kVA generator to run!! Lucky I have a 75kVA generator at the shed so power should be fine. Having a friend check out a CIG 500i transmig and a EMW wega 600 mig this week. Some of these welds are extremely critical and lack of penetration would be catastrophic.
My welder friends say flux cored wire ?with CO2 shielding is the go.... and the bigger the better.
I think the tools to build this shed (welders,bevellers,mag drill and cutters,large power saw,vibrating power screed etc) will cost as much as the building itself
But do it right and you only have to do it once.

I'm super jealous of your equipment. Take some pics of the finished structure and post them up!

hi mark
most heavy fab shops in melb (ones at least still in business) use 400 amp migs and Lincoln 71mx 1.2 wire and a argo shield 52 gas mix for out of position structural beams and pipe work and straight wire 1.2 with gas for std beams columns end plates cleats on the bench ect , you haven't stated weld positions you need to do. but if you need all position the lincoln 71mx is one of the best to use . the flux freezes quickly and most people new to this wire are amazed at how vertical ups almost walk up by them self's.
used on heavy structural steel and pipe , jobs with this combo I have welded on are aami park bubble stadium roof, mcg light tower columns , southern star observation wheel to name a few.
multi passes ,clean smooth welds and with a gentle touch with a chisel the slag falls off like iron powder .
hope this may be of some help if your looking for strong structural welds .
good luck Damien

I would echo dodge at4's comments, fluxcore is the ducks guts. One of the most common wires around here is good old Kobe DW100 with CO2 gas.
Just bear in mind that you are only building one shed, presumably for yourself, so speed is very much secondary to weld soundness and ease of use. No wire/electrode will magically make up for poor preparation and technique, nor will brute power. The biggest killer is trying to put in too much metal in one pass, your wire must always remain at the leading edge of the weld puddle. This applies to both solid and flux cored wires.
While flux core run hot by a 400+A machine will undoubtedly be quicker, just as good a job could be done with your 250A mig and/or stick welder, for a much lesser cost if labour is free. Your 250A machine will push .9mm wire to its maximum and do justice to 1.2mm if that's your fancy.
One often overlooked factor that favours stick welding for site work is the ease with which you can set up to weld 6 or 8 metres in the air on a breezy day. Try and do the same with a mig and either solid wire or gas shielded flux core.
As far as stick electrodes for your job, I'd give 7024's a miss and stick to low hydrogen rods in 3.2, 4.0 and 5.0mm sizes. 7024 are a shallow penetrating electrode and restricted to downhand work.
I noticed that you were looking at an EWM machine. Based on my experience with 4 of these machines on a mine site, I would run as far as I could. We were supplied 3 brand new machines, all of which failed before the fourth machine managed to last until I left that site (6 months). They were all run in a dry workshop from a 415V supply that was tested and verified as within spec.

Thanks guys for your comments. Will take them on board.

Still to go and look at (and run) the EWM600 and a CIG 500i . Will give them a good try out first and thanks for the warning Karl.

Check the regulations, overhead crane to me says AS/NZS 1554 code for structural welding. Before I retired where I worked wanted a small jib crane built and because I was the only one currently coded I had to weld it even though there were others who were perfectly capable but it had to be a current code holder. The paper trail is important so they know who to hang out in the case of an accident.

Originally Posted by clive hugh

Check the regulations, overhead crane to me says AS/NZS 1554 code for structural welding. Before I retired where I worked wanted a small jib crane built and because I was the only one currently coded I had to weld it even though there were others who were perfectly capable but it had to be a current code holder. The paper trail is important so they know who to hang out in the case of an accident.

Thanks for your advice Clive. The crane and the supporting structures will be welded by a professional welder. I will limit myself to non critical welds. But I hope to do all the preparation ie cutting/bevelling etc myself.
In the end this crane will be in my private shed and no-one will touch it other than me. Having said that I will do it as professionally as possible.

I had no idea flux core wire was so cheap these days, Why would you bother with lots of stick or gas with prices like this.

Hyundai Flux Core SF-71MC MIG Welding Wire(E71T-1) - 1.2mm x 15KG Spool | eWelders

Originally Posted by .RC.

I had no idea flux core wire was so cheap these days, Why would you bother with lots of stick or gas with prices like this.

Hyundai Flux Core SF-71MC MIG Welding Wire(E71T-1) - 1.2mm x 15KG Spool | eWelders

you still need to use a shielding gas with this wire, if you had lots of welding to I'm with you much better than burning sticks

Originally Posted by markgray

Thanks for your advice Clive. The crane and the supporting structures will be welded by a professional welder. I will limit myself to non critical welds. But I hope to do all the preparation ie cutting/bevelling etc myself.
In the end this crane will be in my private shed and no-one will touch it other than me. Having said that I will do it as professionally as possible.

And what happends when you sell the house or worce case you pass away and leave it behind.

I hate to be the safty nazi, because i hate them myself but it is somthing to think about. In saying that as 1554 as far as i can remeber is basicly if it looks good it will pass no worries.

Sent from my SM-G900I using Tapatalk

Originally Posted by brendanh

And what happends when you sell the house or worce case you pass away and leave it behind.

I hate to be the safty nazi, because i hate them myself but it is somthing to think about. In saying that as 1554 as far as i can remeber is basicly if it looks good it will pass no worries.

Sent from my SM-G900I using Tapatalk

You are dead right in what you say, however in my opinion, for what it's worth, the welding is not the biggest issue. To my mind, the crane will need to be re engineered due to the beam having been altered and the supporting structure also engineered in order to remain on the right side of the law. Simplest would be to find a friendly engineer to sign off on the job, but this may well cost more than the crane did.
In the event of the OP passing away, I guess he will not be worried about compliance or otherwise, but in the case of the property being sold it would be wise to clearly mark the crane as being decommissioned, even to the extent of putting an out of service tag on the isolator switch along with a padlock and noting that the crane is not engineer certified. The only legal way that the new owner could put it back in service is to enlist the services of a qualified person to repair/certify the crane. Removal of out of service tags may only be done by an appropriately qualified person once repairs are complete and the item is servicable. If the new owner chooses to use bolt cutters to remove the padlock and tag, then they just assumed liability.

Ok guys calm down. The ONLY person who is going to use this crane is ME. I want it safe but no employees/friends etc will touch this crane. The shed is on a family property which has been owned for >100 years and is not likely to be sold.
The crane and its supporting structure are significantly over engineered. Could probably put 20 tonnes on this structure and it would not come down. I have an engineer friend who has shown my plans to his structural engineer friend and he is happy. Obviously he is not going to sign off on this type of job without the full structural workup and quality assured/certified construction which I don't need. The price for structural engineered plans/quality assured construction/crane certification would probably exceed the price of building the whole shed!! Thanks for the concern but I have built temporary lifting gantries to lift much greater weights without problems so I am sure it will be fine.

Cheers

Mark