corten steel

[chunkolini]

I have been asked to make a welsh dragon and we discussed using corten steel to avoid corrosion damage over time
The customer likes the Corten bridges on the A483 over Abergavenny they are looking fantastic after a few years in the Welsh sunshine.
So working corten
welding? can you use mild steel mig wire? Im sure I heard that this is ok
sheet first. the wings and body will be made of sheet probably 1.6mm. Does it cut and bend similarly to mild steel or is it harder to form? I have plasma cutter, angle grinders and hand held power shears and a set of 4ft rollers for curves
Plan A is to make a hollow body using this sort of structure. Basically two sheets cut to size with an internal frame and then wise strips welded around the edges to give a solid looking body.

Plan B (slowly becoming Plan A)
is build a structure of round bars and fill it in with small panels to give a structure like this

bars and strips.
ive seen round bar for sale but no flat strip. Id be looking for 10mm round bar and 30x5mm strip.
would they both have similar properties to mild steel? for cold working. I cant see many problems with the round bar but the strip? would it bend along it's flat side like this? of would it just refuse to bend?

to date I've always used hot rolled mild steel with no problems

can anybody recommend a supplier? I've found sheets of 1.5mm for £176 at Buy Metal Online pricey but seems ok for a posh product
but no strips so far.
I think thats enough for starters
Cheers all.

 

[Jelly_Sheffield]

can you use mild steel mig wire? Im sure I heard that this is ok

Corten MIG wire is a thing, about £150 a reel (the cheapest I could find, Corten ER 80S-G Low Alloy from Weldstar on Zoro) and only available in 15kg reels... If you have any doubts, I would probably just price a reel of wire into the job.

The general advice is that under 10mm thickness, making fusion welds, then normal SG2 MIG wire or 7018 Electrodes are fine, and the dilution of the puddle into the parent metal should result in acceptable weathering properties on the weld.

If you are building up on the surface to make decorative details, you probably won't get that level of dilution, and the weld metal will weather differently, which over time may induce corrosion in the parent metal.

I would also suggest that you won't get sufficient dilution in the middle of multipass fillet welds, so ideally you'd do any large fillets as a single pass with larger wire/electrode if not using Corten filler.

ive seen round bar for sale but no flat strip. Id be looking for 10mm round bar and 30x5mm strip.

I would think that any decent stockholder or profiler which carries Corten would be able to supply you the 5×30 strip by guillotining it off a sheet/plate.

would they both have similar properties to mild steel? for cold working. I cant see many problems with the round bar but the strip? would it bend along it's flat side like this? of would it just refuse to bend?

Generally speaking Corten has similar cold working properties to a low-carbon structural steel of an equivalent strength grade.

If you have been working with S235 or S275 then Corten will be slightly more difficult to bend. If you have been using S355, then Corten will be about equivalent.

USS (the manufacturer) recommends "Corten A" (a high phosphorus grade) for use in aesthetic fascias and artistic projects due to its superior bending performance (compared to Corten B which is for structural applications).

If you're buying branded Corten (and not an equivalent grade) then it will be supplied hot rolled, as that's all USS manufacture it as.

 

[Prajna]

Well @Jelly_Sheffield seems to know his stuff. It seems that Corten s often welded with ms rods or wire unless thick/multi-pass (as mentioned) or, and here's the kicker, for sculptural work where it is desirable for the welds to weather the same as the base metal. I would add that Corten does work harden like stainless, certainly when being drilled.

 

[hotponyshoes]

I've welded shipping containers (3mm?) with normal mig wire. The welds hold fine but you can certainly see a difference in the weathering. Fairly rapidly as well. It might even out over time but I don't know as I've painted them all eventually.

It's no different than mild steel to cut or bend. I've not noticed any work hardening (but I'm used to working with stainless) although my experience with work hardening is limited to bending a half cut bit back and forth until it snaps off.

If you can find someone putting doors into shipping containers the offcuts from that are about 30mm wide although might be a bit thick for you?

If tig is an option then you can get corten filler in small quantities rather than buying a full roll of mig wire. Or you could just wave the torch around to get plenty of dilution?

 

[chunkolini]

Cheers guys.
I think stump up forThe wire, use sheet and round bar for the dragon.
He's going to stand on a 2m globe.
I was going to use edge best strip for lines of latitude and longitude.
I think I'll suggest using mild steel for this and galvanising the globe.
I could use 30x5mm mild strip for the globe. It would last for years.
But I'd rather it be a lifelong thing.

 

[nickk]

I’ve always found it more bend resistant when working cold,I made all the buckets for a water wheel restoration so the rolling and bending took a lot more time and effort,welding up to 6mm was no different but when I later fabricated with 8 & 10mm,used corten wire,you could see a difference in tones after a period of weathering.

 

[dan.taylor.1]

It's worth checking what gas mix is required for the wire you want to use as it may be different to what you use now.

 

[Dragnet]

The consensus with my fabricator is that under 10mm there'll be enough copper around to make the weld reasonably close to the rest of the steel so we haven't worried about it. I've done the window reveals in 2mm and the cladding in 3mm for this extension, with no noticeable weathering differences so far after several years. All done with a Sealey 130XT and normal wire with Argon/CO2. I would like to think I can tell the difference between a sheet of mild and a sheet of weathering steel, as it seems to be a little oily in texture by comparison. I can't say I've noticed any difference in working.

 

[Prajna]

I've welded shipping containers (3mm?) with normal mig wire. The welds hold fine but you can certainly see a difference in the weathering. Fairly rapidly as well. It might even out over time but I don't know as I've painted them all eventually.

It's no different than mild steel to cut or bend. I've not noticed any work hardening (but I'm used to working with stainless) although my experience with work hardening is limited to bending a half cut bit back and forth until it snaps off.

If you can find someone putting doors into shipping containers the offcuts from that are about 30mm wide although might be a bit thick for you?

If tig is an option then you can get corten filler in small quantities rather than buying a full roll of mig wire. Or you could just wave the torch around to get plenty of dilution?

I was thinking containers were 3mm too but I've just put a door in the side of a 20 foot one and the sides certainly seem thinner, around 1.5mm I'd guess. Could be that I just had blunt drill bits but the main doors were a bit of a feat to drill through for fitting a lock box.

 

[julianthegypsy]

I was advised that mild wire is fine up to 4mm as there is sufficient dilution in the pool to get copper into the weld. I made a stove in 4mm corten once and it was fine.