Hardened and Hardenable Metals Suitable for Making Armour

[Craig Nadler]

I'm updating this post with more details as I get them. Last Updated Nov. 05, 2017

I've started work on a tutorial on the different hardened or hardenable metals that are suitable for making high performance armour for HMB/ACL/IMCF/BotN style sport fighting with steel weapons or SCA style sport fighting with rattan weapons. This is a very rough draft, Please make comments if you have anything to add. The estimates of dent resistance are my best guess / opinion.



Notes on Ductility Needed for Armour:

One rule of thumb that I've developed is for how ductile the
steel used for full contact armoured combat sport armour
should be. In my opinion the absolute minimum lab
measured elongation for break for the material at the heat
treatment that you are using should be 10%. Based on
results seen with 4130 and 17-7ph stainles steel I'd
recommend 11.5% for body and 13% for helmets.



Quick Reference for Yield Strength and Ductility:

Mild Steel 29ksi / 39% EBB
304 Stainless Steel 42ksi / 55% EBB
1050 Carbon Steel / C50 / ST50 at Rc43 ~180ksi / ??% EBB
4130 / (EN) 25CrMo4 at Rc48 208ksi / 11.5% EBB
65G / GOST 65 (Russia/Ukraine) ~155ksi / ??% EBB
30HGSA / 30KhGSA (Russia/Ukraine) 192ksi / ??% EBB
410 Stainless Steel at Rc45 156ksi / 12% EBB
17-7ph Stainless Steel (USA) 150ksi / ??% EBB
Full Hard 301 Stainless Steel 140ksi / 9% minimum EBB
17-4ph Stainless Steel (USA) 150ksi / 11% EBB
Titanium - Grade 5 / 6Al-4V (USA) 128ksi / 14% EBB (227ksi adjusted for density)
Titanium - Grade 2 / "Pure titanium" (USA) 49ksi / 28% EBB (85ksi adjusted for density)
Titanium - OT-4 (Russia/Ukraine) 99ksi / 18% EBB (171ksi adjusted for density)

EBB = Elongation Before Break
~ = I'm guessing at the yield strength based on the most similar material
that that I can find a material data sheet for.



Basic Baseline Metals:


Mild Steel / 1008 -
Relatively speaking it is very easy to shape cold, but has very
poor corrosion resistance and a very low yield strength. The 2%
yield strength is is 29ksi with an elongation before break of 39%.


304 Stainless Steel / (EN) X2CrNiN18-7 -
Has a high degree of corrosion resistance and about a 1/3 higher
yield strength than mild steel. The dent resistance is generally
considered to be that of mild steel 1.33 times its thickness or
about two sheet metal gauges.

The 2% yield strength is is 42ksi with an elongation before break
of 55%.



Hardenable Steels:


1050 Carbon Steel / C50 / ST50 -
In the annealed condition it can be shaped much like mild steel.
It is heat treated by heating it to 1600F and quenching in water
or oil, then tempering it for 30 minutes. When quenched in water
and tempered to 700F / 371C resulting hardness is Rc39. It's dent
resistance seems to be that of 304 stainless steel around 2,5
times it's thickness.
I do NOT recommend hardening 10XX past Rc40.


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.


65G / GOST 65 (Russia/Ukraine) -
I obtained a fair amount of unhardened 0.8mm Russian 65G (1065)
steel. Looking at the 0.65% carbon contain oil rather than water
would likely be the better choice for a quenching medium, however
not of the other steels that I normally work with use an oil quench.
I choose to use a water quench because that is what I had on hand.
The critical hardening temperature for this sort of straight carbon
steel should be around 800C. To be sure that the thin parts reached
full hardness I set the kiln at 900C to account for the parts cooling
off between the time that I opened the kiln door and when I
submerged the parts in the quench water.

After quenching the parts in water the hardness measured in the
Rc57-58 range. A Temper of 30 minutes at 350C resulted in a Rc49,
at 400C a Rc43 hardness, and at 450C a Rc37 hardness. While
fixing the warp in a large number of brigandine plates I noted that
65G at a Rc43 hardness is far more brittle than 1050 at the same
hardness. If the hardened plates required a fair amount of reshaping
then cracking around weak points are a significant problem. Even
at a Rc37 hardness 65G was much more brittle than 1050 at Rc43
and vastly more brittle than 4130 at a Rc48 hardness.

I recommend using a 1 hour 450C temper for a hardness of Rc37
for 65G steel. I would not recommend hardening 65G pass a Rc37
hardness.


30HGSA / 30KhGSA (Russia/Ukraine) -
This alloy is similar to 4130 except that it does not contain any
molybdenum. Much of the following information is based on a
translation of a research paper on this alloy steel titled "Effect of
Tempering on the Facture Toughness of Steel 30KhGSA" by
T.M. Golovinskaya and N.I. Chernyak published in Kiev, Ukraine in
"Probelmy Prochnosti" on September 16, 1974.

The recommend heat treatment is to heat the steel to 880C and
quench it in oil. As a personal note I have found that depending
on the how thin the steel is or how quick it is quenched once the
furnace is opened it may be required to heat it to 900C or even 920C
to reach full hardness. A 350C one hour temper should result in a
yield strength of 192ksi / 1324MPa. The steel heat treated with this
process I have found to have a hardness of Rc43.

When you compare 30KhGSA to the OT-4 titanium commonly
used in armour in Russia and Ukraine 30KhGSA is 94% stronger
per volume and 12% stronger by weight. Please note that by
stronger I specifically am referring to yield strength, which is a
good measure of how well a metal will resist denting. This does
not take in to account how much the metal flexes when it is
struck by a weapon. When selecting the thickness of alloy steel
to use in armour you should keep in mind that even if the armour
is undamaged if the wearer is injured it has still failed.

I recommend using a 1 hour 340C temper for a hardness of Rc43
for 30HGSA alloy steel.


Hardenable Stainless Steels:


410 Stainless Steel -
The corrosion resistance is much less than 304 stainless steel, but
much better than mild steel or 1050 spring steel. In the annealed
state the yield strength is on par with 304 stainless steel, but the
ductility is around half of that of 304 stainless steel.

When heated to 1850F and air quenched and then tempered to 400F
for 2 hours it seems to resist denting as well as 304 stainless steel
2.3 times its thickness. Data sheets for 410 stainless steel list the
2% yield strength at that temper as 156ksi with an elongation before
break of 12% with a Rc45 hardness.

I look at this material as a compromise between 1050 spring steel
and 304 stainless steel. You get some of the corrosion resistance of
304 Stainless Steel and some of the dent resistance of 1050 spring
steel.

THIS IS VERY IMPORTANT: If you do not temper 410 stainless
steel long enough after a water quench it can be very brittle while
still having a hardness that looks ok, I do NOT recommend a water
quench, it only adds to the stresses that you'll need to relieved
during the tempering step. An air quench is safer and easier. I'm
not sure if there is any point to oil quenching plates as an air
quench seems to work very well and gets the plates to full
hardness.


420A Stainless Steel -
This is a higher carbon version of 410 stainless steel with 0.15-0.25%
carbon. This material seems to be readily available in the Ukraine
and Russia, but in the USA it only seems to be available if you are
buying a truck load at a time.

Going by the data sheets for this material it seems that a 190-195ksi
yield strength with at least a 12% elongation before break. On paper
it looks like it MAY be a good choice for armour. Some of the issues
are that it still would have the poor rust resistance for something
classified as a stainless steel as with 410 stainless steel, it is an
"air hardening" steel so hot working or welding are problematic.
Another big issue in the USA is that most sheet metal being sold as
420 stainless steel is actually 420B, 420C, or 420HC all of which
have too much carbon for use making armour.


17-7ph Stainless Steel (USA) -
The corrosion resistance is on par with 301 stainless steel and close
to that of 304 stainless steel. In the annealed / condition A state the
yield strength is some what lower than 304 stainless steel and the
ductility is some what lower than 304 stainless steel. When
compared to annealed 410 stainless steel 17-7ph stainless steel is
easier to cold form. With the TH1100 heat treatment it resist denting
as well as 304 stainless steel 2.2 times its thickness.

According to the material data sheet the yield strength of 17-7ph
stainless steel in the RH950 heat treatment condition is 18% higher
than the TH1050 condition. However the heat treatment process for
the RH950 condition is much more technical, time consuming, and
costly. Based on a batch of 17-7ph stainless steel test plates that
heat treated to the RH950 condition I saw a noticeable increase in
brittleness, but did not notice much of a difference in dent resistance.
Please note that I measured the hardness of the test plates to verify
that the heat treatment process had been performed correctly. For
armour I now recommend a TH1100 heat treatment. I saw enough
failures of 17-7ph stainless steel armour heat treated to TH1050
to warrent this change.

Please note that an electric kiln with an automatic temperature
controller is needed to heat treat 17-7ph stainless steel. Also, due
to the length of the heat treating process 17-7ph stainless steel is
much more costly to have commercially heat treated than 1050,
4130, or 410 stainless steel. The cost of the 17-7ph stainless steel
sheet metal is also much higher than 1050, 4130, or 410 stainless
steel.



High Yield Strength or Pre- Hardened Metals:


Full Hard 301 Stainless Steel -
The corrosion resistance is close to that of 304 stainless steel. This
material is difficult to shape so it is only useful for parts that have
only a simple curve or a moderate compound curve. The dent
resistance seems to be that of 304 stainless steel of 1.8 to 2 times
its thickness.

This material is hardened at the steel mill by passing it through a
rolled mill cold until it work hardens to Rc43. If this material is hot
work then it returns to its annealed state and can not be rehardened.


17-4ph Stainless Steel -
The corrosion resistance is close to that of 304 stainless steel. This
material is very difficult to shape so it is only useful for parts that
have only a simple curve or a slight compound curve. This material
should be heat treated before it is shaped. Heat Treating it to
H1150 only slightly increases the yield strength, but it increases the
ductility from a 5% elongation before break to 11%.

301 full hard stainless steel is about half the price when I checked.
The yield strength of 17-4ph stainless steel at a heat treatment
ductile enough for armour is very close to that of 301 full hard
stainless steel. 17-4ph stainless steel requires heat treating, but
301 full hard stainless steel does not. I don't see any good reason
to choose 17-4ph stainless steel over 301 full hard stainless steel.


Titanium - Grade 5 / 6Al-4V (USA) -
This material does not rust. The yield strength per volume is
128ksi / 880MPa and the density is 4.43 g/cc / 0.160 lb/in³. The
density of 4130 alloy steel is 7.85 g/cc / 0.284 lb/in³ so it is
1.775 times heavier per volume. If you multiple the 1.775 by the
128ksi yield strength to get a idea of the strength to weight
relative to 4130 alloy steel it is 227ksi / 1565MPa, which is 9%
more than the 208ksi / 1434MPa. The elongation before break is
14%.


Titanium - Grade 2 / "Pure titanium" (USA) -
The material does no rust. The yield strength per volume is
49ksi / 340MPa and the density is 4.51 g/cc / 0.163 lb/in³. The
density of 4130 alloy steel is 7.85 g/cc / 0.284 lb/in³ so it is
1.742 times heavier per volume. If you multiple the 1.742 by the
49ksi yield strength to get a idea of the strength to weight
relative to 4130 alloy steel it is 85ksi / 586MPa, which is nearly
double that of 304 stainless steel, but far less than that of any
hardened steels.The elongation before break is 28%.


Titanium - OT-4 (Russia/Ukraine) -
The material does not rust. The yield strength per volume is
99ksi / 685MPa and the density is 4.51 g/cc / 0.164 lb/in³.
The density of 4130 alloy steel is 7.85 g/cc / 0.284 lb/in³ so it
is 1.732 times heavier per volume. If you multiple the 1.732 by
the 99ksi yield strength to get a idea of the strength to weight
relative to 4130 alloy steel it is 171ksi / 1179MPa, which is 18%
less than the 208ksi / 1434MPa.

[GuntherofOrkney]

nice. so far with my 410 stainless shoulders they have not shown any signs of rust and have never even wiped them down after practice for the last 3 monthes and i practice an average of 2times a week. I am a huge fan of 410 stainless.

Any info on 4130 chromoly steel?

[Craig Nadler]

I haven't tried 4130 yet. Currently I'm working with 17-7ph stainless steel. It looks like it will out perform 410 stainless steel in dent resistance, rust resistance, ease of heat treating, and not scaling up during heat treatment. The only down sides that I see at this preliminary stage is that it cost almost twice as much and is said to be very difficult to weld.

[Thomas Powers]

What about some of the Ti alloys?

[Scott Martin]

Hi Craig

You may also want to update the stainles steel (304) to its actual performance, which is a bit better than 1.5x mild steel, SCA has a "2 gauge rule" actual performance is closer to 4 gauges but I'd much rather have 18 stainless gauntlets than 16 mild in terms of protection, and the lighter weight is a bonus.

430 stainless is similar in performance to 304 and can be less expensive, although it is somewhat less corrosion resistant (still doesn't rust under normal conditions)

316 Stainless is similar in performance to 304 and is generally more expensive, although it is incredibly corrosion resistant (used for Hydrogen Sulphide piping). I find it easier to weld, and the food industry is currently transitioning from 403 to 316, which should bring the price down

17-7 needs more care in hot forming, since it will "bubble" at the upper end of orange heat (Aluminum Volatilization?) I find that it is more dent resistant in its annealed form than 304 stainless. I haven't tested heat treatment yet, still playing with the "raw" form.

Scott Martin

[Craig Nadler]

Scott Martin:

I only included mild steel and 304 stainless steel is base lines to compare hardened and hardenable steels to. I'm opinion is that 2 gauges stronger is just about right for comparing mild steel and 304 stainless steel. This is also in line with the 2% yield strengths of mild steel vs. 304 stainless steel.

The results that I got with the first batch of 17-7ph stainless steel test plates was very impressive and much better than 410 stainless steel.



Thomas Powers:

Titanium and Aluminium are not allowed in ACL/BotN steel fighting so I'm excluding them.

[GuntherofOrkney]

titanium and aluminum are ok for acl but not botn/hmb. my suit has alot of aluminum in it currently but i am upgrading to spring steel asap.

[Kenshin Hanabe]

Keep up the good work!

[Tostig]

Craig, et al,

This is nice work and really useful info. This succinctly outlines the key features and benefits of the materials.

I'd like to see discussion about the look of the metal. To my mind that might shift a decision from one metal to another to gain something more period looking or at least not glaringly modern.

Thanks,

-- Tostig

[Tostig]

Other insights about workability, like fire scaling, weldability, application of finishes, etc would be really handy have compiled in one place too.

[Ernst]

Since the article is destined for an international audience, I would incorporate Fahrenheit to Celsius conversions into the paper as a parenthetical. This saves potential readers the trouble of having to look it up if they aren't familiar with the metric.

[Scott Martin]

Craig, et al,

This is nice work and really useful info. This succinctly outlines the key features and benefits of the materials.

I'd like to see discussion about the look of the metal. To my mind that might shift a decision from one metal to another to gain something more period looking or at least not glaringly modern.

Thanks,

-- Tostig

In general if it's a stainles steel then it has a lot of chromium in it, and is "too white" in appearance unless it is blackened or has some other surface treatment. If you want it to look right, it will rust.

10xx series steels have the correct "look" and are the closest match to the period metal available with modern materials. Note that "Mild" steel is generally 1018 (not enough carbon to harden) but is visually close to 1050 / 1070.

4130 is very similar in appearance to the 10xx steels, but as noted above it will rust. Dave Wise (Sir Alexis) has done a lot of work with 4130, which is easier to get since it is a common aviation alloy also used for performance cars and bicycle tubes ("Chromolly")

I will add that of the materials in this list, mild steel is the most effort to polish - it's so soft that looking at it funny causes scratches, and it transmits heat really well so you can't get good heat transfer which makes the surface melt more difficult and has a tendency to get your whole piece hot - stainless steels polish relatively easily. I'll let you know how the various carbon steel alloys polish once I have played with them a bit. "hot roll" steel is just not worth the effort to clean up, although I hear that a good vinegar bath will deal with most of the firescale that is on the surface as part of the process.

Craig, did you do the heat treatment for the 17-7 in your kiln, or have it batched out?

Scott Martin

[Craig Nadler]

Scott Martin:

I heat treated it myself. I posted these notes on the 17-4 Ph and 17-7 Ph Stainless Steel for Armour thread:

I just heat treated two 0.035"/20ga./0.9mm 17-7ph stainless steel test plates to condition TH1050. The heat treating process was to heat the test pieces to 1400F for 90 minutes, then air cool them for a few minutes before putting them in a 55F water tank. I used ice and a digital thermometer to keep the temperature between 53F and 57F for 30 minutes. I then heated the test pieces to 1050F for 90 minutes, then let them air cool. Here are my notes so far:

1) The annealed / condition A 17-7Ph stainless steel cuts much more crisply than annealed 410 stainless steel, which is very gummy when sheared.

2) Annealed / condition A 17-7ph stainless steel seems to cold work very well. I'm wondering if the people on this thread who said that they had a hard time shaping it were talking about 17-4ph stainless steel instead.

3) The test pieces discolored from the heat treatment, but there was no fire scale as with 1050 spring steel or 410 stainless steel.

4) My initial feeling is that the dent resistance is on par with 1050 spring steel with a 650F temper. This is based on hitting it with a 24oz.ball peen hammer. I was just heat treating 1050 spring steel to a 650F temper today so it was fresh in my mind from having to fix some minor warping. I'm guessing that the dent resistance was on par with between a 0.090"/13ga./2.3mm or 0.0109"/12ga./2.8mm 304 stainless steel.

5) It did not seem brittle. I clamped the corner of a dished plate in a vise and bent it back and forth a few times and it did not crack.

[robertdonnell]

I don't know where you fight but if you can hide the metal say in a coat of plates, aluminum can be hardened, it is 1/3 the weight and 1/3 the strength of steel so you would think well it is a wash but it is not, that makes the Aluminum thicker and more firm so to make steel as ridged you have to flute and edge the steel, Al plates can be just a plate.

Brigantine Armor hides the plates on the inside so that is another good place for Al.

[Galfrid atte grene]

Anecdotal, but I've fought 2x weekly in my 410 suit for a couple years in the northeast US and I've never seen rust (with no prevention attempted).

[Ingelri]

4130 behaves much like 1050.

[Rhynella the Wanderer]

New to this and experimenting. Using 16 gauge steel, but I know from the recent hail storm and leaks in the ceiling that my steel will rust in 30 minutes when dripped upon, thus my worries in producing armor for valiant, yet dampened, fighters. I'm debating on lamellar plates and leave it up to the wearer to protect the steel, with foreknowledge of course, but my conscience struggles even with that. Still researching.

[Baron Alcyoneus]

If you were making a covered coat of plates, or brigandine, you could simply use galvanized steel.

[Craig Nadler]

Here are my recent test notes:

I just finished heat treating a small batch of 17-7ph stainless steel test plates to condition RH950. I verified the hardness after the 8 hours of -100F in the 2nd step and after the final step. The hardness measured matched the spec.. I clamped a test plate with a shallow dish in it in a vise a bent it 100 degrees and it snapped. I tried a flat test plate with the same test and it did snap on the 1st bend, but I did when bent back the other way. Next, I tried compressing a knee lame so that the ends were touching. The lame bent and it seemed to me not to resistance bending or denting any better than TH1050. That being said the difference in yield strength is only 19% between TH950 and TH1050 I could easily of not noticed a 19% increase in strength.

Notes:

One thing that I was looking for was if a plate that warped slightly could be fixed after the heat treating. The answer to that question seemed to be yes it can be fixed

17-7ph stainless steel at RH950 did seem somewhat more brittle than TH1050, but not to the point where I wouldn't use it.

It seemed to me that 1050 spring steel with a 650F temper is as good as 17-7ph stainless steel at condition RH950. Maybe TH1050 would then be on par with 1050 spring steel at a 700F-675F temper.




I finally got around to ordering some 0.032" and 0.040" 4130 sheet metal to test. Going by the spec. sheet this stuff looks like it may have the best dent resistance in ACL/BotN fighting of all the materials that I've tested.

I think that 17-7ph stainless steel at a TH1050 or a RH950 condition is a very good material and it has a lot of rust resistance. That being said 1050 spring steel can be made somewhat more dent resistance before you get into hardnesses that are too brittle to be safe.

[Craig Nadler]

How many of the FULL-TIME armourers that offer spring steel have heat treating kilns with a computerized temperature controller? After talking with a few different armourers I realized that Winter Tree Crafts is the only one that I KNOW that has a real heat treating kiln. It seems that most armourers are using manually operated top loading pottery kilns that they picked up used. A few armourers are outsourcing their heat treating.

You can get away with using a manual kiln (i.e. - no computerized temperature controller) for alloys that are heat treated using a quench and temper process, but precipitation hardened alloys would be problematic. It also seems that some armourers use a manual kiln for the hardening step, and then use a kitchen oven for the tempering step.

The reason that I bring this up is that the equipment that you are using effects which alloy would be best suited for you to use. It seems that 4130 is the most forgiving of the heat treatable alloys equipment wise.

[Nissan Maxima]

Slow industries(Grettr gauntlets) uses computer controlled ovens.

[Craig Nadler]

Nissan Maxima:

I thought that Grettr was a full-time engineer and did armour as a sideline business. Is that not the case?

One of the points that I was going to make is that the profit margin in producing armour seems to be too low to support buying a new purpose built heat treating kiln.

[Caius705]

Automatic controls are difficult but I know it's fairly simple to jerry rig an electronic temperature measurement system
a cheap thermocouple from ebay and a decently accurate voltmeter, possibly some tcouole extension wire. Very simple set up.
Instrumentation tech here, never done heat treating before.

[Baron Alcyoneus]

Close enough?

http://www.bigceramicstore.com/info/cer ... oller.html

[Craig Nadler]

I know that you can add a temperature controller to a manual kiln, I've done it before. My question was which full-time armourers besides Winter Tree Crafts have a kiln with an automatic temperature controller.

[Tom B.]

Nissan Maxima:

I thought that Grettr was a full-time engineer and did armour as a sideline business. Is that not the case?

One of the points that I was going to make is that the profit margin in producing armour seems to be too low to support buying a new purpose built heat treating kiln.

He just reciently went full time with the armouring business.

[Craig Nadler]

I updated the sections on 4130, 410 stainless steel, and 17-7ph stainless steel.

[Caius705]

Craig, in your experience, 4130 works about the same as 1050 when both are in the annealed state, correct?

[Craig Nadler]

I haven't tested the 4130 material that I bought yet, but there shouldn't be much of a difference.

[Caius705]

Craig, with regards to 301 SS, how does Half Hard 301 compare to 304? 3/4 hard 301 to 304?

[RoundTop]

Speaking from working with 301 1/2 this last weekend, apart from the hardness, it is wonderfully "springy". It flexes and recovers extremely well. Thin shavings of it that coiled up while I was cutting it acted just like a good spring, unlike mild or stainless

[Craig Nadler]

Caius705:

The 2% yield strength for:

304SS is 42ksi
301SS annealed is 40ksi
301SS 1/4 hard is 75ksi
301SS 1/2 hard is 110ksi
301SS 3/4 hard is 135ksi
301SS full hard is 140ksi

Those numbers came from here:

http://www.aksteel.com/pdf/markets_prod ... lletin.pdf

and here:

http://www.aksteel.com/pdf/markets_prod ... %20PDB.pdf

[Craig Nadler]

Seeing as this thread is back on top I'll talk about 4130 vs. 1050 for ACL/BotN steel fighting armour.

* In the USA you can get 4130 sheet metal online in small sheets. With 1050 you need to buy at least 50 pounds per thickness ordered.
* 4130 weld filler rod and MIG wire is available from http://www.weldtool.com/, 1050 is not available.
* 4130 is generally considered easier to weld than 1050 due to the low carbon content of 4130. 4130 has 0.30% carbon and 1050 has 0.50% carbon.
* 4130 has enough carbon for any hardness that would be at all reasonable for armour, but not enough to allow you to easily create a piece of armour that would shatter. 1050 can be made so hard as to shatter when struck with a steel weapon.
* 4130 has better ductility at a given hardness than 1050. Even at a 400F temper (Rc49+ hardness) the "Elongation Before Break" is 10%.

[Caius705]

Thanks Craig, you kick ass.

[Kenshin Hanabe]

Very insightful, thanks!