
Scientists Invent a New Steel as Strong as Titanium - chromaton
http://www.popularmechanics.com/technology/news/a13919/new-steel-alloy-titanium/
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msandford
Steel can be stronger than titanium depending on the alloy and heat treatment.
It's not uncommon to see heat treated 4130 upwards of 100ksi which is right in
line with titanium. At those hardnesses it tends to be more brittle, though,
unlike titanium.

The breakthrough here isn't that they can make it strong, it's that they've
made it both strong and tough. Toughness is how much something deforms
plastically rather than breaking. Mild steel is very tough but not terribly
strong, you can easily make it 4x (or more) stronger by sacrificing toughness.

Not having to make an engineering tradeoff between strength, toughness and
price would be pretty fantastic.

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Armisael16
It's easy to make steel that's stronger than titanium; the challenge is making
steel with a higher specific strength than titanium, since titanium is so much
less dense. Steel is still the clear winner by volume, which is what
unqualified 'strength' refers to.

Titanium is also nice for its anti-corrosive and non-magnetic properties, and
its low coefficient of thermal expansion. There's a reason it showed up in
aerospace very early - its a good fit there.

~~~
simonh
And military submarines with non-magnetic hulls are considerably harder to
detect.

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msandford
Man, that would be an expensive sub, made completely out of titanium. At $8/lb
and 6000 tons (12 million pounds) you're talking about $100mm just in
materials and that's before you do anything. Titanium is very difficult to
weld due to oxygen embrittling the weld so you'd have to put everyone on
rebreathers and assemble the whole hull inside a giant tent with a slight
positive pressure of argon only. That's the kind of project that'll give
people nightmares.

~~~
durkie
Why a giant tent? Why not normal MIG/TIG welding that floods just the weld
area with argon?

~~~
mtreis86
[http://weldingdesign.com/archive/beginnings-and-
development-...](http://weldingdesign.com/archive/beginnings-and-development-
pressure-hull-welding-united-kingdom-submarines)

The quality of the weld is extremely important, enough so to justify the 0% o2
environment.

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alricb
In addition to being old news, this story isn't all that exciting. They've
made an Aluminium-based steel that's 13% lighter than ordinary steel(density
of about 6.83 vs. 7.85) and that isn't brittle like previous Aluminium steels.
It could have interesting uses, especially if it can be made cheap and with
good properties (weldability, formability, workability, corrosion resistance),
but they're just at the small-scale stage and they have a corrosion resistance
problem to solve.

~~~
wrsh07
Shouldn't they add [Feb 2015] to the title?

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alricb
Previously on HN:
[https://news.ycombinator.com/item?id=9001704](https://news.ycombinator.com/item?id=9001704)

(Same South Korean researchers)

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pjkundert
I wonder how it compares to "Flash Bainite" steel?

[http://www.flashbainite.com](http://www.flashbainite.com)

For the DARPA Armor Challenge, to stop a .30-cal APM2 armor piercing round,
requires:

1/4" Flash 500 vs. 1/2" Titanium vs. 3/8" High Hard vs. 1-1/8" Aluminum

From:
[http://www.flashbainite.com/about/applications.html](http://www.flashbainite.com/about/applications.html)

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jsonmez
Yes, but is it as strong as Rearden Steel?

