Titanium vs other metals

Discussion in 'Boat Design' started by Stumble, Jun 5, 2012.

  1. aranda1984
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    aranda1984 aranda1984

    Titanium replacement parts

    Replacing certain aluminum parts with material having higher tensile properties may work in some situatuions.

    However, the advice that you should ask an engineer to pick the right solution, is the best I have seen.

    I worked extensively with titanium. Drilled, milled and welded the stuff.
    No problem if you know what you are doing, otherwise you burn up the drill in a couple of seconds.
    Titanium is used mainly for it's ability to stand up against nasty corrosive substances.
    Making heat-exchanger tube plates, we normally use steel, (or stainless steel)but have a thin plate of titanium welded to one side that is exposed to the acid.

    Think of your problem this way: for instance, if you want to improve deflection (if the part is loaded in bending) the tensile strength of the material does not come into question, only the modulus of elasticity.
    So an engineer will be able to improve any shortcomings just by changing the shape or size and stick with the inexpensive, simple to use aluminum.

    Stephen I. M.
     
  2. Stumble
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    Stumble Senior Member

    To some extent this is true, but the primary drive for rediculously high titanium prices was really the US government. For decades it used about 95% of the worlds titanium supply, primarily for the DOD. Because of procurement rules the government could only buy from 100% US owned and located suppliers. So the few US sources had an effective monopoly on world demand, so they kept prices high, and didn't care about driving down costs.

    Recently a lot of that has changed as world demand for titanium has increased, and supplies from non-US sources have increased. This has really driven down the cost to manufactur Ti.

    Of course as prices have gone down, demand has risen, allowing fabrication costs to go down, allowing.... Basically a positive spiral for the cost of titanium bits. To the point that Allied Titanium can provide fasteners like bolts, nuts, screws, at around 25% more than the comparable part in 316SS for more specialized parts costs are higher, but getting better. And for truly unique parts, where both the titanium or SS would be one off productions, again we can often get pretty close to the SS price.


    I am not a machinist, so I can't promise that my information is 100% correct, but as I understand it Ti is not particularly difficult to weld, though it does take some special precautions to prevent oxygen embrittlement. But basically it is just TIG welding with argon, though both sides of the weld have to be argon shielded. And the argon has to be kept in place until the temprature drops to below 800F.

    As for machining, it is supposed to machine like stainless, slow, good chip removal, lots of cutting oil (at least with titanium olive oil seems to be prefered).
     
  3. Cheesy
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    Cheesy Senior Member

    Just to be pedantic, it is not a titanium coating, it is a titanium nitride coating which is very different. Titanium is very bad in wear situations. Coated drill bits are good however it is still a coating therefore the drill bit is still only as good as the steel underneath....
     
  4. ancient kayaker
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    ancient kayaker aka Terry Haines

    Titanium has some nice characteristics, it is almost as light as aluminum and almost as strong and stiff as steel, melting temperature is as high as some refractory materials, it's tough as well a strong and extremely corrosion resistant. However cost is much higher than steel or aluminum, or marine bronze for that matter, and fabrication is challenging as it's a beast to machine. It's great for satellites, high performance aircraft and robots, but I find myself wondering why on earth anyone would want to use it on a boat where there is very little incentive to prune weight or reduce volume particularly at such a cost . . .

    HSS drill bits will go through most things you are likely to encounter especially if you use the proper coolant/lubricant - ordinary paint thinner works fine for aluminum, cutting oil makes an incredible difference when drilling or cutting steel even with hand tools. Water works but not as well. I think a coolant is more important when using TiN coated drills as the coating is not a good heat conductor.
     
  5. Mr Efficiency
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    Mr Efficiency Senior Member

    I can see it being useful as a fastener where high corrosion resistance and strength are needed, and might see 316 stainless coming up short in the latter department.
     
  6. portacruise
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    portacruise Senior Member

    I also heard about this, and that there might be a stealth advantage in that particular time period, as well.

    "Titanium" drill bits seem to be more brittle than steel in my experience, but that may be because or the steel substrate required if they are plated with the nitride.

    Standard mass produced CF parts such as rods and tubing, splices etc., are becoming more available and would appear to have some advantages over titanium in some uses:

    http://dragonplate.com/ecart/categories.asp?cID=52

    Porta
     
  7. FranklinRatliff

    FranklinRatliff Previous Member

    It was not a fairy tale.
     
  8. paddilack
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    paddilack Junior Member

    Alfa

    attack submarines were doublehulled Ti nukes. Able to go very deap, and very fast also. apparently not as quiet as US subs, but able to operate below max depth of most NATO torpedoes at the time. Caused some gray hairs and bald spots for a while I believe..
     
  9. paddilack
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    paddilack Junior Member

    Shqval

    Combine this with VA-111 Shqval supercavitating "torpedoes" (really submerged missiles) at 200 Knots and you have the full attention of NATO Navies in the early 90's..
     
  10. DCockey
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    DCockey Senior Member

  11. MechaNik
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    MechaNik Senior Member

    I asked the manager of "Ermis 2" superyacht about their titanium deck fittings. He says "They were produced mainly by a professional company specializing in titanium fabrication. The hardware is extremely low maintenance and only needs polishing around the 316 stainless fasteners. Unfortunately we were not aware of titanium fasteners at the time. The cost of custom made bits is not excessively different when compared to stainless steel."
     
  12. upchurchmr
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    upchurchmr Senior Member

    "Excessively" has a different meaning between Superyacht owners and myself.
     
  13. Stumble
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    Stumble Senior Member

    Upchurch,

    It really depends on the part, but for the products we sell that are in mass production the prices can be as close as 20% more for titanium. Now that is only for the stuff we can make in large lots like common sized bolts, and nuts, but it isn't terribly bad for a product that is 2.5 times as strong, and will never corrode.

    Some of the parts we make where the stainless production numbers are low as well can also be reasonably closely priced. Like our titanium cleats that run about 50% more than stainless for the same size. Or chain plates that can be very similar in price as well.

    The problem with getting prices down across the board is simply one of production numbers. One off parts just cost more to manufactur than if we were running hundreds of them at a time.

    For instance our anchor swivel for 3/8" chain costs around $550 if I sell them one at a time. This is pretty high compared to stainless, though our design is better since we can take advantage of the stronger metal to reduce the swivel sides in such a way to allow for side loading. However the running price on a 316 stainless swivel is only about $170, so most people will opt for the stainless.

    However if we can find a chandlery that was willing to place an order for 100 or more pieces the price comes down dramatically... Our price on that $550 swivel for an order of 100 or more would be around $220. Obviously still more than the stainless, but only about 30% more. However that buys a swivel that is corrosion proof, even under water, and is so much stronger than the one it replaced there really isn't a comparison.

    I doubt titanium even with large order numbers will be competitive with galvanized steel any time soon, but it can be with stainless. The trick is to get demand high enough to allow for mass production to drive the prices down, and convince chandleries that it is worth taking the risk on larger order numbers.

    For instance if we could get West Marine to commit to inventorying just one of our shackles in each store, we could probably get the cost of that shackle down to close to the $200 range. But of course they need to see the need to buy it, which is of course my job.
     
  14. pdwiley
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    pdwiley Senior Member

    The thing that would concern me about using titanium in any load-bearing application is that it's known to be notch sensitive and therefore has the potential to fail catastrophically under load.

    PDW
     

  15. upchurchmr
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    upchurchmr Senior Member

    Bull.

    I'll check with our metallurgist and DADT experts to see what you might be thinking.

    Everything fails under enough load. I'll take Ti with a notch over Aluminum with a notch any day.

     
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