Sheet steel vs sheet aluminium

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New Member
Hello all, new member here.
I have been sitting on an idea for about six months now and it seems time to start asking questions of the people who have experience in this.
Having trained as a blacksmith/metalworker, I have been thinking of making a starter piece (I thought maybe a Reach bracer armour piece) out of cardstock paper using the pepakura method, then printing out the pepakura pattern again and this time tracing it out onto either sheet steel or aluminium.

Here is where I come to my question, from looing around on the forum it seems like those that have used metal for their builds have mainly chosen aluminium, weight being a consideration. I have only worked with sheet steel so far, and apart from being more expensive, heavier and more resistant to cracking, do any of you have suggestions of things to consider when making my material choice?
P.s Thickness is something else I'm not sure about when using a pepakura template
I use 0.75mm steel because it's cheaper (I think? haven't compared it, but it's definitely cheaper for me to work with) and I can just get it locally at the hardware store. I can also weld it with flux core wire, so I don't need argon, which would be an additional cost. So it basically comes down to what you can get, how much you want to spend, and what you can/want to work with. Aluminium allows you to use thicker material while not being as heavy as steel, which can be useful, as 0.75mm is pretty much on the edge of what I can weld, so there isn't much room for grinding or thinning from forming. It's doable though. I'd say get some material (doesn't have to be much) and just try out something small that has most processes you need and then decide based on that.
0.032" (0.75 mm) is a good thickness steel. I'm using chrome-moly alloy 4130, but works pretty much the same as regular mild steel in this thickness. I use it for a lot of my medieval projects. It's thick enough that it resists buckling/wrinkling when doing complex shapes, but thin enough it's not hard to bend and isn't too bad on weight. Also, that seems to be the breaking point where steel starts getting more expensive per weight. Once I jump another gauge thickness up the cost seems to jump disproportionately!

I'm doing a Noble 6 build primarily in 6061 aluminum, but 4130 alloy steel for the helmet and probably the knees. Most of the body armor parts are straight bends with only slight compound curves and are well suited for aluminum. I like the fact that rust won't be an issue, too!

I started on a helmet with aluminum and it was absolutely awful to work. To get compound curves and tight bends, it was cracking out. Steel is much, much easier to work complex shapes.

I'm actually doing a pretty rugged helm design. I'm using 0.063" (1.5 mm) 4130 alloy steel for the top section of the helm because I can hot work it and pull it/dish it/stretch it into the shapes needed out of a single piece. The finished thickness will be about 1mm. The back panel will be 0.032" since those are relatively simple contours. Likewise, the lower jaw and sides will also be 0.032". The "ears" are yet to be determined. I'll try it in the thinner stuff. All parts will be heat treated/hardened then tempered back to a spring hardness like I do with my combat medieval armor.

I'm also trying to avoid welding and will be doing hidden rivets. You bevel your holes, rivet tight, then grind the heads flush so they cant be seen.
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