Scientists invent new steel?

Discussion in 'Science' started by Mathuisella, Feb 7, 2015.

  1. Mathuisella

    Mathuisella Member

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    http://www.popularmechanics.com/technology/news/a13919/new-steel-alloy-titanium/

    From shipping containers to skyscrapers to turbines, good old steel is still the workhorse of our modern world. Now, scientists are discovering new secrets to make the material better, lighter, and stronger.

    Today a team of material scientists at Pohang University of Science and Technology in South Korea announced what they're calling one of the biggest steel breakthroughs of the last few decades: an altogether new type of flexible, ultra-strong, lightweight steel. This new metal has a strength-to-weight ratio that matches even our best titanium alloys, but at one tenth the cost, and can be created on a small scale with machinery already used to make automotive-grade steel.


    what do you guys think ?
     
  2. RobRoySyd

    RobRoySyd Member

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    I think the
    is going to be the real challenge. The difference in electrode potential between Fe and Al suggests this alloy would have a big corrosion issue.

    The process used to make this new alloy is interesting but I wonder how easy to work with any alloy made using it is going to be.
     
  3. patto

    patto Member

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    Absolutely world changing if it can be produced cheaply and efficiently.

    Two very good points. The ease of welding steel is important for widespread use. Steel already has big corrosion issues so the question then becomes are existing treatments as effective in controlling corrosion.

    Also note that in the bulk of steel usage, a stronger steel isn't a massive deal. In reinforced concrete surface area of contact would be important. In structural steel corrosion protection is often 50% of the cost of steel. Labour of construction is much more influential on costs so any difficulties in workability would not help.
     
    Last edited: Feb 7, 2015
  4. SCorpion2

    SCorpion2 Member

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    a steel that didn't corrrode would be a far more important discovery than stronger steel for use in reinforced concrete. That's why I think we are more likely to end up with plastic reinforcement in concrete structures rather than stronger steel.

    I'm sure there will be lots of various applications for this type of material. It would be interesting to see the force-displacement plot for the material to see just how ductile it actually is.

    Good find maths.
     
  5. RobRoySyd

    RobRoySyd Member

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    I thought rebar that doesn't corrode already existed, I recall some argy bargy over why it wasn't used in the tunnel under Sydney Harbour. Obviously such steel is more expensive which is why it's not generally used.

    We also have steel that does rust but forms a stable film that protects the rest of the steel. Such a steel was used for the Centrepoint Tower in Sydney.
     
  6. patto

    patto Member

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    Reinforcing steel doesn't corrode under normal circumstances anyway.

    True that. There is significant petential for plastic/carbon fibre reinforcing applications.

    It is in the link to the study. 30% strain before failure!

    [​IMG]


    Really discussion about structural applications is likely not relevent. The better applications will initially be mechanical, the motor industry for example. It will likely be too heavy for aerospace even if it is so much stronger than aluminium.
     
    Last edited: Feb 7, 2015
  7. SCorpion2

    SCorpion2 Member

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    We sort of have steels that don't rust to an extent or that rusting protects the steel. Rusting, after all, is just the oxidation of the material. Oxidation will only occur under certain circumstances. For instance, we can prevent rusting by galvanising or painting the steel. Galvanising and painting creates a barrier that prevents oxidation from the environment and galvanising goes one step further in that even if the galvanising is damaged, the galvanising will be oxidised first rather than the steel.

    We can use painted or galvanised reinforcement in concrete but it adds an additional 50% to the delivered price of the reinforcement. It is only temporary as the galvanising/painting will eventually break down. In reinforced concrete, the un-protected steel typically breaks down due to carbon dioxide reacting with the cement past to create carbolic acid. The carbolic acid reduces the pH of the concrete which then causes corrosion of the concrete. Normal black reinforcement actually rusts slightly in the concrete initially which does create a barrier to prevent further corrosion and the reduction in pH causes this initial barrier to become ineffective. The increase in atmospheric carbon does significantly reduce the useful life of reinforced concrete structures. This effect is normally referred to as concrete carbonation.

    The other common cause is that chloride ions penetrate the concrete which then cause corrosion.

    We can use sacrificial anodes to protect steel from corrosion but it does require that all steel is sufficiently connected to allow for the transfer of ions to the sacrificial metals. This also increases the cost of construction as well as the cost of maintenance over time. It is often used to protect structures that are subject to chloride ion attach.

    Sometimes we just increase the size of the steel section so that when the element does corrode it still has enough capacity to resist the design loads. We often do this for steel driven piles. Other practices is to coat steel in plastic and then place that steel in a vacuum to prevent corrosion. This is often used for large cable supported structures like suspension or cable stayed bridges.

    Most of the time, we can just routinely paint a steel structure and that is sufficient to prevent corrosion. Routine inspection and painting of structures is generally pretty cheap for the given replacement cost of a structure. These type of steel structures would probably benefit the most from an improved steel that is lighter or cheaper. A lighter structure means less material is required to support its own weight so the structure then becomes more efficient in terms of the ratio of dead load:live load.

    Of course, this all applies to the civil industry. I cant imagine how many different applications would appear in different fields where a cheap version of titanium alloys exists.

    For a material to successfully replace current mild steel deformed reinforcement, it would need to cost less than $3,000/tonne delivered to site. It has to have a decent Yield Stress, say, around 500mPa and it probably should be ductile. The civil industry is toying with different methods to recycle HDPE (so milk cartons etc) so that it has a sufficient Youngs Modulus, yield stress, price and ductility. Its not a bad way of recovering resources and certainly doesn't suffer from the corrosion issues that black steel usually does. I would think that it recycled HDPE would be primarily used in structures like concrete pipes, bridges and multi-story structures.

    It certainly does. I've seen many structures just 30 or 40 years old where repair of corroded reinforcement has gotten to the stage where it is no longer economic to repair the structure and just cheaper to knock it down and re-construct.

    oh yeah, i missed those figures down the bottom.

    I'm sure the discussion about civil applications is relevant, just that the material would be suited to other applications. If they can produce the material for less than 50% more than traditional mild steels then there is potential for its application in structures.
     
    Last edited: Apr 2, 2015
  8. RobRoySyd

    RobRoySyd Member

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    Don't you let my old chemistry lecturer hear you say that, his thesis was on rusting. :shock:

    It can be way more complex than just the oxidation of the iron if water is involved. The hydrogen is what does the real damage. That's what causes rusting steel to swell and flake off.
     
  9. SCorpion2

    SCorpion2 Member

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    Haha. I'm no chemist, I'm just a civil engineer. I just need to understand it enough to recognise the causes of failure and how to treat or prevent that failure mode.

    For example, I always refer to carbonation due to carbolic acid when its actually carbonic acid.
     
    Last edited: Feb 7, 2015
  10. Chaffe

    Chaffe Member

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    Shitty CCS Chinese steel (roughly 210 MPa bar) is around $1500 a tonne in China, welded and painted from Chinese yards.

    Stainless Steel doesn't rust but it costs an arm and a leg.

    It does sound like corrosion is a significant issue for this based on the article. If that is the case you'll probably only see it in buildings as that will be the only place where it can be adequately protected. If this thing corrodes relatively quickly without protection I doubt we'll see it in cars, planes or boats.
     
  11. aXis

    aXis Member

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    The oxidation they are talking about in the article is whilst the steel is molten in the furnace. The journalist was obviously confused and insinuated it's environmental oxidation by saying "out in the real world".

    In normal steel production they have molten silicate slag sitting on top of the molten metal and this acts to exclude oxygen - as you can imagine molten metal is a lot more reactive and oxidises quicky if not protected. This new steel cant use silicate as it reacts with the aluninium, so they will need to use a new slag compund.

    I dont see this being a huge issue as there are lots of existing flux and slag compunds anyway.
     
    Last edited: Feb 9, 2015
  12. Phido

    Phido Member

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    Planes will use more titanium (engines particularly in TiAl) now its easier to work, and composites (body). We need to process more titanium. Australia has about 40% of the worlds reserves yet produces no titanium metal.
    Cars will use more aluminium and composites.
    Building are still after light weight strong steels for re-enforcement and structural steel. Buildings are getting higher.
     
  13. patto

    patto Member

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    What do you base this assertion on?

    Structural steel is a very small component of a building's weight. Even if stronger steel is available, buckling will quickly become the limiting factor which is dominated by cross section.

    Light weight reinforcement is largely inconsequential when it a minor component in a heavy matrix.

    Sure if cost is similar then lighter weight and stronger is better. But costs are not going to be similar. When it comes to structural steels, being stronger is not a significant advantage in most applications. More ductility is not an advantage either, steel is already ductile enough for structural purposes.
     
  14. Fortigurn

    Fortigurn Member

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    That was such an informative and well put together post; I wish there was a like button. :thumbup:
     
  15. SCorpion2

    SCorpion2 Member

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    No worries, happy to share! :)

    I can think of a few instances where stronger reinforcement steels would be advantageous. Pre-cast driven concrete piles for instance. The costs and time savings by being able to use an excavator mounted driving rig is quite a bit when compared to larger rigs. Pile sizes are still often governed by how much steel you can cram into a small cross-section, particularly when they are partially laterally loaded.

    Higher strength concretes will allow for the use of higher strength reinforcement as well. It really wasn't all that long ago when 20 MPa concretes and 250MPa plain reinforcement bars were in use.
     
    Last edited: Apr 2, 2015
  16. duong01

    duong01 Member

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    The guy who wrotes this article probably didn't realize in order to protect liquid hot metal from oxidation you either cover it in slag or have to be a total inert chamber lol
     
  17. duong01

    duong01 Member

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    yeah but its not cheap enough to be production. you still have different grades of welding rods that have different composition in the inert gas generating coating or fluxes in the core that will be used for backshielding.

    penetration and thermal properties aside in production welding a lot of times you'll see GP rods being used in place of alloy/hardfacing rod or low-hydrogen rods if possible due to just purely cost
     
  18. patto

    patto Member

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    That seems a reasonable circumstance where a stronger steel that doesn't cost much more would be useful. But like I said this is mostly a cost factor. And unless the cost differential is small such discussion is immaterial.

    We could use stainless steel or other steels in such applications with which has 200-250% of the strength of rebar.

    Super alloys are largely the realm of manufacturing not of normal civil construction.
     
  19. Eddyah

    Eddyah Member

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    No-one else thought of Ayn Rand's book upon reading the title of the thread ? ;)
     

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