The Armour Archive

cold rolled versus hot rolled mild sheet steel - which is it preferable to use for making armour and why?

Totally a personal thing.

I like to work with cold roll. My friend Kevin likes to work with hot roll. We both turn out decent stuff.

Hope this helps

I personally prefer cold rolled to hot roll for the following reasons. It ends up as a stronger piece without heat treating. Hot roll has a black oxide finish that almost always has to be removed to finish the piece.
I do like it to train new armourers as it moves easier.

im pretty new here so my opinion isnt that valueble but for what its worth..in the short time ive been working with sheet metal i prefer cold rolled. hot rolled you have to over work it to make it nearly as strong as cold rolled....but if i try something i have read about and i feel nervous about it il give it a go on hot rolled just because its cheaper...but i do my final on cold rolled

Taa

Bad Wyrmspleen! No scooby snack. You've been here long enough to know better.

A search of the archived Archive or the Essays page would have given you all the answers you wanted. Such as my essay.


Frederich

Frederich's essay is pretty much spot on! The only thing I would add is that once you dish a piece of hot rolled, it is effectively the same as cold rolled, just like heating a piece of cold rolled to cherry red renders it normalized. The only time you see an appreciable difference in strength between cold and hot rolled is on pieces that are simply curved and not really stretched/thinned/dished or otherwise cold worked...etc. Down here there's about a 50% increase in price going to cold rolled.

Although, not having to jack around with removing scale makes cold rolled worth the extra price to many. Scale comes off easily with a vinegar soak...but I really hate the small of vinegar!

Frederich, I think Wyrmspleen was fishing for our feel of the materials.

Krag: Have you tried muratic? I hate the smell of vinegar too.
I use 1 gal. hardware store swimming pool acid to 4 gal. water.
In a 5 gal. plastic bucket with lid.
2nd. bucket for clean rinse water.
It will also remove rust.
Soak for about 40 minutes.

For the longer parts I pour it into a Wal-Mart plastic rectangle pan.

Black iron (hot rolled) is all I can get locally.
Occasionally; I have come across some cold rolled and it was a pleasure to work with.
Especially when it is new. Left out in the weather, it is no better than hot rolled.

As far as strength vs. hammering; I can not tell any difference.

Like Summits-Ogier said, it is a personal thing.

Hal

What! no scooby snack! and yeah, what Halberds said about 'fishing for everyones feel for materials' (thanks Hal, good save).

I ordered a sheet of cold rolled 2mm today so that is what I will be working with now most of my 1.6 is used up. I can definately see the benefit of hot rolled when I bash cold rolled so much it cracks (happens reguarly on my projects...) so I will have to try annealing some of it, esp when it comes to those 14th C knee and elbows I want...

I use HOT rolled for some reasons:
I find it near here
It's cheap
The black oxide can easily removed with HCl
The same Black oxide is a nice base for internal paint and is a good protection against rust itself
I like the black coat

A lot of the HR on the market these days is P&O, which will give you a surface that rivals CR. The biggest differance between the two is thickness tolerance.
An example:

16 gauge sheet has a nominal thickness of .0598 (thanks to "light-to-gauge production...more sheet from the coil!)

HR P&O tol range: .0658/0.648
CR tol range: .0538/.0548

The CR has closer tolerances.

Hal,
Yes, I used to use HCl. I don't like storing it though. No matter how tight the lid is, everything within a couple feet of the storage location seems to rust! To keep it out of reach of my son I have to keep it up high which means everything below is subject to rusting.

Related note....I have a hot bluing tank now we can play with at the armour-in. It uses 99.97% NaOH crystals dissolved into water at 8lbs per gallon. Heat to 300*F and dip. Good for putting on a black oxide layer . The high carbon sheet armour rusts just by looking at it. Hopefully this will aid! I can only fit ebow/knee cops in the tank though!