power vs thickness....

[Aesgarth]

I'm about to start welding on a fence, the posts are going to be 40x40x3mm box welded to 40x40x10mm plates, the panels will be top and bottom horizontal bars of 110x6mm flat with 16mm square uprights in between - roughly every 100mm.. I'm hoping my mig is up to the job but thinking it probably isnt, so how much power am i looking at needing to be able to stick that lot together properly?

Thanks.

 

[Richard.]

Well it's a fence and I'm assuming it's just got to stand up, hold its own weight and deal with a few windy days? So you'll stick it together well enough for what it's got to do with 160amps if need be. If it was to be welded with proper penetration into the 6mm and 10mm plates then you'll need a minimum of 200amps. I'm not Sure that's Essential though unless you plan on putting load on it.

 

[Aesgarth]

I'm not planning on on putting load on it but one side of it will be accessible to the public and i do anticipate people will lean on it. I was considering TIGing the posts together, there's only 14 of them compared to 300ish 16mm square uprights - don't want to TIG both ends of all of them.

 

[Aesgarth]

I only have a clarke 151te so max 150A. May have to do a bit of prep on the joints. :-/

 

[Richard.]

If you've got a tig does it not offer the facility of mma. This would be the safest bet. You never know what the general public are gonna do to it. Use the mig for the 3mm wall box as it will be perfect for that and use some 3.2's for the thicker stuff

 

[Aesgarth]

It does have mma facility but I've never tried it. I do have some offcuts i can practice on though. I have run about 10 practice beads when i was doing my tig course a couple of years back. Good suggestion.

 

[Richard.]

Best of luck.

 

[Piero]

Might want to look at the effects of different gases.

 

[Richard.]

Might want to look at the effects of different gases.

High CO2 will help further regards heat/pen but with those thicker sections if he's got the unit then sticks is going to be more suitable.

 

[Kent]

I should likely go MMA for the thicker stuff on it, you can also cheat a bit by the way the joints are formed and use that MIG though if you give it plenty rest. I just never get the descriptions given verbally by novice or self taught Fabricators to advise further on that without a drawing. Look out with stick if its supplied in unpainted galvanised though as every little slag trap and fault in those stick welds will pop out and smack you right in the eye after galvanising.
Don't bother messing with co2 it makes it harder not easier and for what your doing no real tangible gain. Agoshield universal or similar is just fine.
For gates and railing work you need the biggest single phase you can get to deal with the thicker joints and black bar etc. to be fair but a 150 mig will do the box and MMA will do the rest. Personally I should just use stick for the lot if I didn't have a bigger Mig and save keep switching processes. 3.2mm decent E6013 rod about 100 on the box and about 120 on the bar depending

 

[PSweeney]

was wondering the same recently., made a stand for a small lathe, 3mm box to 6mm plate feet, 185A Portamig off a 32A supply and whilst it laid down nice hot welds, I didn't feel like I had the power to fully penetrate the 6mm plate. It holds up fine and I'm sure it'll be OK but I wish I had bought the 210A version.

 

[rikrobson]

I managed to blow a large hole in some 5mm thick 100mm box section with a 4mm 6013 rod while playing with the MMA function on my new 250i R-tech

 

[Kent]

I managed to blow a large hole in some 5mm thick 100mm box section with a 4mm 6013 rod while playing with the MMA function on my new 250i R-tech

Not surprising really 3.2mm at 100-120 was what you needed, in fact if the fit was good a 2.5mm at about 80 could have been perfect 4mm is a lot of hot metal to handle in less practiced hands

 

[Aesgarth]

I just never get the descriptions given verbally by novice or self taught Fabricators to advise further on that without a drawing.

Doesn't help that after reading back what i wrote it bears little resemblance to what i actually meant. Does thia help?

Edit: got the description completely wrong...

 

[Kent]

though that was the situation just couldn't read that in it. your issue with the little mig will be the 16mm square to the 40x10, these will end up going in cold as your not doing much past the start and stop.
Here is a way you might handle it without using the stick which will actually do it fine BTW. Drill the 40x10 and have the bars actually inside those holes top and bottom. Plug weld it on the very bottom &very top and fill the gaps with a weaved fillet on the bottom top face and underside. This way your using the material strength in your favour (the welds can be surprisingly neat when you get the hang of it)
I think if some kids start climbing on it etc there is otherwise a risk of a bar breaking out and someone getting hurt.
MMA is way the better choice if your up to it.
The base plates should be ok if you crank things up direct the heat at the plates and get them down to shiny before hand
I assume this is on your own property

 

[Richard.]

I think it's a really neat idea to drill them and fit the bars inside the holes which ever method you weld it with. The strength will be doubled. You'll have a lot less squaring up to do and even though that's a lot of holes it will actually not take any longer to do as your tacking and squaring of each bar is massively reduced. Kent nice tip.

 

[Aesgarth]

Quite like that idea. Tried stick welding with the tig set today, only used 2 rods just to see how i got on with it, not bad but definitely need a bit of practice. I'll have another play tomorrow.

 

[Bill Edwards]

You may already have some, but I'd strongly suggest that you use decent quality rods from a known brand. Cheap rods can be OK, and some can be a complete nightmare even for the experienced.
Make life as easy as possible when trying to stick weld.

The idea of drilling holes is a good one, but personally I would not be comfortable welding the 40 x 10 flat onto the posts with a 150a MIG, so I'd certainly want to do that with MMA.

 

[Aesgarth]

The rods i have are cheap ones from aldi. I'll try to get some decent ones tomorrow or I'll order some for next week. I also have some 4mm (i think) rods that may not be crap but are a bit big.....

 

[Bill Edwards]

4mm! No!

3.2 would work, but I would say you should use 2.5.
People have different preferences with regard to preferred welding rods, but I don't think you'll find anybody who would advise against Murex rods. Phoenix are pretty decent, and if you can't get either then just stick to known welding brands.