[CliffordK (OP)]

Every once in a while one hears of a new super-material.  Stronger & lighter than steel.

So, what exactly is "stronger than steel?

Steel, of course, comes in a variety of alloys from your typical "mild steel" to exceptionally strong tool steel, to somewhat brittle high speed steel.  And, of course, various stainless steel alloys.

I have some 50 year old pieces of farm equipment.  And, anything that isn't steel has sure taken a beating from weather checking of tires big enough to stick a finger in to huge cracks in the steering wheel. 

Airplanes, of course, have tremendous issues with metal fatigue.  Typically aluminum in the aircraft industry, but steel can also experience fatigue in some situations.

Often in use, while aluminum is lighter than steel, some of it is made up with more bulk  In some situations, bulk can lead to additional rigidity, but the weight savings is not always as high as one might expect.

There is a lot of talk about carbon fiber.  But, it might better be considered a fiber/resin composite.  I presume, however, it can fail under many of the same stresses that cause fiberglass to fail.

So...
What can replace steel?
Or should it be engineered steel?

[damocles]

Steel piano wire is the strongest material in tension, volume for volume, but nylon filaments are stronger weight for weight. Carbon fibre comes in between on both measures.

[evan_au]

One of those materials often quoted as "stronger than steel" is spider silk.

Just as there are many steel alloys, so there are many species of spider, and most spiders produce several different kinds of silk for different purposes - some emphasising tensile strength, some toughness, and some because they are sticky.

It is really a question of "Stronger than steel in which application?". For example, some kinds of silk stretch when they get wet - this might be a problem in some applications. You also need to consider failure modes - if you exceed the rated load, does it fail gracefully, or catastrophically? (Composites share the load across many fibers, and so tend to fail more gracefully.)

But the claim usually comes down to the fact that spider silk is less dense than steel, and so the comparison is often qualified by "stronger than the same mass of steel".

I imagine that the same caveat applies to kevlar, carbon nanotubes, diamond and graphene, which are also sometimes the subject of similar claims.

See:  http://en.wikipedia.org/wiki/Spider_silk#Strength

[Bored chemist]

Dollar for dollar, aluminium and timber may be stronger than steel

[bizerl]

I've also heard anecdotally that living bone is stronger than steel, but again weight for weight.

It's always a bit of a headline though. I'm not sure I'd want to pit a ball bearing against my tibia, even if they did weigh the same. And I'm sure a jagged piece of wood would do quite a bit of damage to a sheet of foil of the same weight.

[syhprum]

Is it not time we adopted a different name for the small steel ball used as projectiles ? they are not bearings but the balls used in bearings should we not call them bearing balls ?

[CliffordK (OP)]

I've also heard anecdotally that living bone is stronger than steel, but again weight for weight.

The body can be quite extraordinary.
While a grinding wheel can do nasty things to flesh, I have used my fingers to guide a file, capable of cutting steel, but not too damaging to flesh (at least with a light touch)

Leather can be surprising resilient to a variety of environments.

[shagydeep]

Hello,
uuhhh nothing is stronger than steel... O8)

[kingpanel]

Utility wise, steel is more in use than aluminum is. However, recent trends have shown that the popularity and usage of aluminum are increasing. It is set to overtake steel in the very near future. This is because of the lightness and corrosion resistant qualities. Secondly,aluminium is abundantly available in the Earth’s crust. The cost of manufacturing aluminum from [spam link removed - mod] from its bauxite ore is infinitely less than the cost of manufacturing stainless steel.

[Bored chemist]

The cost of manufacturing aluminum from [spam link removed - mod] from its bauxite ore is infinitely less than the cost of manufacturing stainless steel.

Nope, it is definitely finitely less.

[Petrochemicals]

Titanium has the same modulus in tension and compression which is why it is so brilliantly springy.  Titanium is stronger than steel by weight in tension and compression than steel but is 1.07 times greater in bulk. Ultra strong steel is stronger in ridgidity than titanium due to alloying and hardening through carbon alloying, this however meano it 8s far more brittle. Plastic is stronger than steel in tension by weight but deformation in compression.

Titanium however is stronger than stainless steel by 3 times in weight terms, whilst having corrosion resistance, and resistance to heat and billogical inert. It is more difficult to harden though.

Tungsten is stronger than any other metal I believe, but is poisonous and is highly affected by traces of other elements.

If they can bring down the costime of titanium it will, but manufacture costs are that steel costs 80 a ton scraplease stainless is 200 and titanium is 9000 pounds a ton scrap. Copper was 3000 a ton to give you an idea of prices

[alancalverd]

The cost of manufacturing aluminum from [spam link removed - mod] from its bauxite ore is infinitely less than the cost of manufacturing stainless steel.

Nope, it is definitely finitely less.

Interesting economic argument here. Steel is generally manufactured using coal or gas heating, which imposes an ongoing revenue cost. The energy required to extract aluminum from bauxite makes those sources uneconomic or environmentally undesirable, so production tends to be centered on hydroelectric power, with a high capital but very low revenue cost.

It's interesting to compare the total energy investment in (and environmental impact of) a railway such as HS2, against providing the same service with aircraft. The breakeven seems to be around 50 years, beyond which there may just be an argument in favor of rail transport.