The Armour Archive

Ceawlin wrote: There is a lot of scale to sand off. I've heard you can use an acid bath to take it off, but someone mentioned that the 4130 can become brittle under certain conditions.

Eachann wrote:Ceawlin, what are you using for your tempering (temperature, time, etc)? I was under the impression that due to the low amount of carbon (0.3 %), you really couldn't over-harden 4130 for armor (not an expert, just an interested bystander)..

Hardened and Hardenable Metals Suitable for Making Armour wrote:4130 / (EN) 25CrMo4 -
In my opinion 4130 looks to be the best material for SCA, BotN,
and ACL armour in all area except rust resistance. The heat
treating process is much more forgiving with 4130 than with
1050 carbon steel. The yield strength and ductility are better
at higher hardnesses than with 1050.

In the USA 4130 is currently easier to purchase in small amounts
than 1050. Welding filler rod is available in 4130, but not in 1050.

The as water quenched hardness for 4130 is Rc52, for 1050 it's
Rc62. The effect of this is that accidentally dropping or hitting a 4130
plate that has not been tempered is much less likely to cause it to
crack,

Tempering temperatures suitable for armour are much lower, than
with 1050 carbon steel. The effect of this is that a kitchen with good
temperature controller can be used to temper 4130 plates,

To harden 4130 heat it to 1650F to 1700F depending on how long
it take you to get it into the quench tank after you open the kiln door
and quench it in water. When tempered at 400F for 30 minutes it
seems to resist denting as well as 304 stainless steel 2.8 to 3 times
its thickness. Data sheets for 4130 stainless steel list the 2% yield
strength at that temper as 220ksi with a elongation before break of
10%. When tempered to 500F for 30 minute temper the 2% yield
strength at that temper as 208ksi with a elongation before break of
11.5%. When tempered to 600F for 30 minute temper the 2% yield
strength at that temper as 195ksi with a elongation before break of
13%.

For ACL armour other than helmets I recommend a 500F / Rc48
temper. For helmets I recommend a 600F / Rc45 temper. If you are
using an oven for tempering that only goes up to 550F, that should
be fine.

Ironbadger wrote: There is another potential issue.
I would have to rely on torch or forge heat and judging temperature by eye, as I do not have an electric oven or thermometers to control temp precisely.

I suspect I would be courting failure before I even begin....

-Badger-

Tom B. wrote: If this is something that you decide to pursue as a more common type of work

Ironbadger wrote:For the moment, its something I am looking to do to see what its like.
I'm no longer looking to become a full time armourer.
Mostly, I am doing it for myself and to make a bit of cash once in a while.

But there is a lot I would really like to make, and plenty I want to learn, just to learn it.

The idea of making lightweight, hardened armor appeals to me as a skill to learn, and maybe to profit from once in a while.

I'm never going to be competing with more dedicated armourers, as I'm more of a knife and sword making guy at heart.

But I would like to play with 4130 armor, if I can manage suitable tools.


-Badger-

Ironbadger wrote:Theres something I would need to know.
I know of the trick of using vinegar to remove scale, but had not heard of 4130 possibly becoming brittle under the effects of mild acid.

Anyone have more definitive answers on this?
I'd be using something like cheap white vinegar in gallon jugs for preference because its readily available and about as inexpensive as anything I could think of, while easy to clean up.

-Badger-

Ceawlin wrote: There is a lot of scale to sand off. I've heard you can use an acid bath to take it off, but someone mentioned that the 4130 can become brittle under certain conditions.