Titanium vs. steel

Warped flatheads and philips? yeah.

 

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My opinion is that titanium is superior in most ways to even the best iron based alloy, purely on a strength to weight basis and many other competitive criteria. However, in the real world of financial reality, the relative cheapness of iron based alloys is a powerful consideration.

You pays your money and you takes your choice.

 

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Wow, practically twice as stiff.
I didn't know that, I was just thinking about mountain bikes. Titanium bikes ride much stiffer than steel (unless it's an ultralight, high carbon steel bike). Now that I think about it, steel bikes are much heavier, so end up absorbing more shocks.

Here's a wiki page for some materials and their stiffness. The GPa values of Ti and steel match up with the ones on matweb (cool website, btw).

 

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Yeah matweb is a great site for looking up materials - too bad some of them are proprietary and a few inconsistent details released for some of the alloys.
At least it's good for the AISI/ASTM standards.

 

Titanium has about 65% the weight of steel. So basically, the statement that it is better in terms of strength to weight is basically true - in general.

However, exceptions exist. The strongest titanium alloys have around a peak yield strength of 1600 MPa. Accordingly, steel should have a yield strength of 2600 Mpa to match that performance. There are a few that can do this, such as ASTM 4036, varieties of stainless, or Cxxx maraging metals.

On a strength-to-volume basis, higher-strength steels are nearly unrivalled. They love to say that nylon and spider silk fibers have strengths in excess of 5 times that of steel on a per-weight basis, but logically, when you shift to a per-volume basis, steel happens to be around 1.4 times stronger. The only common mass-produced materials that rival steel's volumetric strength density that I can think of are carbon fiber and S-glass fiber. If you factor in the anisotropicity of these two, then there's not much else.

 

I am not a novice at understanding the strengths of materials in different regimes.

While titanium and various steels are strong ( pun unintended but delightful ) competitors in many ways of being a strong material, they both faint in the field of tensile strength, where several other well known and easily ( relatively speaking ) available materials are vastly more capable.

May I be redundant and doubly repeat my previous statement: you pays your money and you takes your choice.

 

just jumpin in for one question

I was looking up the strength and properties of steel vs. titanium and came across this thread(thank you google)

I read the first couple pages of comments and you all seem very well educated on the subject so I wanted to ask a question.

Say you wanted to build a mesh of wires(or pillar like archs) about one foot in diamiter, give or take, what kind of stability would either kind have? Which would be more benificial to use.
Also with both substances in that form, how well would either hold up to heat or missile/bombing attacks?

And how feasable would it be to create a mesh, or screen, that would form a very large half hemisphere(anywhere from 2-5 miles diamiter). About how large would that have to get with either metal b4 it lost its structural integrity. Or would it even have structural integrity to begin with?

I have no experience with this subject besides the fact the in general titanium produces a stronger substance, and steel makes a slick katana. I just would like all your opinions.

 

I wonder if you can make titanium more flexible by alloying tiny amounts of silicon...as in making 'spring steel'?

 

diamond is the best because it's hardest. with nanotechnology you'll probably be able to make even harder material.

50,000 years ago they had invisible walls of impenetrable substance (ultramatter). it was probably harder than diamond. by changing the vibration of matter you can make it harder or softer, heavier or lighter.

space is the softest material i know.

 

I'd say it all depends upon the application of each product and how it is used as to which is superior and cost effective.

 

I am just guessing (but usually make reasonably good guesses):

Properly designed, I am pretty sure more that mile (on Earth) diameter (half mile high, with more than half open mesh) is entirely feasible, even if the opening have thin sheet closing them.)

I bet that only steel is used in the near Earth surface and some structural (not alloy) mix with Titanium in the mid-altitude with some Al alloy only is used in the highest parts of a good design. (The very top will be flat 3D triangular grid structure for helicopters to land on -see next paragraph)

In the next century (2100s) probably the rich will live inside these sealed domes in truely "central air conditioned" in high rise apartmens with parks and perimeter guards to keep the "rif-raft" out. Most will "telecomute to work" but when they go to the park to walk the dog etc., ~ half their journey will be by elevator. - Is this what you are thinking of?

The problem is not technical, but social / economics factors is why these domes do not now exist. (Other rich will live their entire life on the high seas but the "boats" may look somewhat like these bomes too. Making their floor not "buckel up" in the center will be a technical challenge.)

 

Thx for the info, but I was actually thinking of a form of protection that could be erected to protect a city from bombings and missile strikes(and possibly nuclear attack), Ive heard a lil about the dome theories and if they had a well reinforced grid of defensive cage within the wall I could see it working effectively.
The technical opinion was well appreciated tho, thx

 

And in this vien, [even more far fetched, beware], how feasable would it be to support such a strucure and elevate it anywhere above 1/4-1/2 a mile in the air?

 

NO a big fuel-air misture blast would flatten a large dome structure easy. It would become the projectiles tha kill many below it. - a gift to the enemy!

 

Why cant we just have a domed disk shaped floating city, supported by hundreds of giant empty aluminum pylons?

The waves will simply flow around them...as with drilling rigs.

 

Water flow beneath the floor is not the problem (In fact there is very little motion to the water more than a wavelength below the surface.)

The problem is that the entire weight of the dome can not be on the floor circumference only. One way, somewhat ugly, to avoid the upward buckling of the floor is to have columns from the floor to the dome throughout the interior of the enclosed area. Perhaps the apartments could go to the dome and be these support structures that remove most of the dome weight from the circumference of the floor.

There is a slight problem (with easy solution) in construction in that you cannot build the entire circular floor and dome before you have these internal support columns. - So you start with just a ring (no central floor) and sea wall on both sides of it. - Sort of like a below sea level, circular race track. Then you build some more floor as a smaller radius ring and there are briefly three sea walls, but the one between the two others can now be disassembled and you can start building the apartments etc where it was. As the weight increases, the sea walls are made higher. Eventually the outter one only exists and it is of course curving inward and now called the "dome." Note that the floor and lower section of the seawall dome is made for the same corrsion resistant steel. - You do not want to promote electrolytic corrosion with different metals.
Also note that probably part of the mesh openings are covered on one side by Fresnel plastic lenses that concentrate sun light onto high temperature solar cells. The entire city turns to track the sun. Part of the energy they produce runs these motors and some probably recovers zink (for corrosion protection by corroding) from the sea or otherwise prevents the slow crossion and kills barnicles etc. IT IS AN INTERESTING PROJECT - too bad I will be dead before even real design work starts.

I.e. at all stages in the construction the area loading of the structure pushes the floor down in a distributed way so that the flexing of tendency of the floor to buckle up is counter acted by the weight locally pushing down.

Despite all this the floor is much more expensive and an engineering challenge than the dome. If a mile in diameter the waves will tend to break it up the same way a torpedo destroys large warship. Most people think that is by hitting the ship. It is not. The torpedoed blows a big bubble far below the ship which briefly finds it ends well supported by water and it central section unsupported. The ship breaks in the middle by falling into the air hole the torpedo made. Likewise, if the north edge and south edge of the mile diameter city are in water but the EW diameter is in air, the city will go to the bottom. The amplitude of the "city scale" waves MUST BE LESS than the depth into the water of the city floor so it always has water under all parts of the floor.

PS I need to added to my prior post that only the ultra rich live in these floating cities (except for a few good looking ladies providing services to them, but they are ultra rich in another way, so not really an exception. I also assume that security against pirates is by robots and automatic guns etc. not hired private army that might take over.) These floating cities will be much more costly controlled environments than the land based ones, but offer a tax free haven to compensate -probably have their own currency etc.

Later by edit: I think it is best to start at the center and work your way outward during construction. the weight of the central apartments can hold the floor down. These apartments need not have full height intitially so their weight can be adjusted to meet the current counter balancing needs.

 

neither. I'm partial to aluminum.

 

You guys are getting lost in numbers a bit.

Comparing titanium to steel is apples and oranges. And a misnomer in both cases.

Titanium can not match the strength of steel, not the hardness of steel. But titanium exceeds steel in some other forms of material performance. I am a knife collector and we discuss this sort of thing in great depth, with knife makers and even material physicists.

Many high end knives are made with a titanium alloy handle and a good steel alloy blade. Like a Chris Reeve Sebenza for example. Each of these has a titanium handle and an S30V steel blade. They run around $450-500 a piece, the plain one around $375-$400.

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Most titanium, though it is one of the most plentiful elements on earth, is not pure titanium, so there is no one such thing as "titanium", you have to be more specific. Much of what is called "titanium" is alloyed with other materials, usually aluminum and platinum. This matters as to the material performance. So when discussing the material you have to be specific to the exact alloy of the titanium, it's very rarely pure titanium crystal and that substacne is not very useful. Titanium is expensive because of the process needed to separate it from the ore(most commonly the Kroll process

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if you are curious, there are other means but Kroll is far and away the most common for now), but the titanium itself is everywhere on earth, very plentiful.

Nor is there one "steel", you have to be far more specific. In fact many steels used today are alloyed with forms of platinum, and aluminum, and many other material elements. This makes modern steel very uniform in molecular and carbide structure, and able to reach hardness levels thought impossible only 10-20 years ago.

You take a ZDP189 steel? A Cowry X or Cowry Y steel? These are some of the most amazing alloys on the planet. S30V, S60V are two other 'high end' steels. Then there is good old CPM154 designed for jet aircraft engines, this is one of the most common higher-end knife steels today, or the Hitachi equivalent of ATS34. A2, D2, 1085, 1095, 52/100(great stuff), 12C27, AUS6, AUS 8, VG10, SGPS, etc... many, many steels.

The way a steel performs depends primarily on the way it is heat treated, this is even more important than the recipe(mixture of elements). The heat treatment of metals is the oldest and most explored form of material physics in the history of man, it literally changes the molecular matrix and the nature of the molecules themselves. So you can't make strength or performance judgements even based on the recipe(type) of steel alone either. How was it heat treated? with what Rockwell hardness in mind? Titanium is even alloyed into steels.

There is no simple answer to this question except:

In strength of any type including tensile, and hardness, steel wins by a long shot.

In resistance to temperature(very high melt point give titanium a high ceiling of 'temper') tolerance of vibration, certain types of torsion stress, strength to weight, and corrosion resistance, titanium wins.

 

I was thinking: since plumbing gets corroded and leaky after 50-100 years of use, would it be economical to make titanium plumbing? Wouldn't it be more healthy to have pipes made of titanium so less corroded metals get into your drinking?

Reminds me of how Germany makes their roads out of cement rather than black top garbage. Their roads last hundreds of years before work is needed. Our roads however, create lots of jobs.

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Gain something lose something, it would probably cost more resources now to switch over to making only cement roads than would be worth the change.

 

I think you need to watch a plumber work, and then decide. How is a plumber going to custom bend titanium pipes to fit curvatures exactly?

I've seen plumbers with pipe benders match up radiators nice and easily. You would have to have pre-bent standard radii joints if you used titanium, and that would be incredibly restrictive, and reduce the options for placing things.

Also, copper being soft, it seals at joints nicely, and solders really easily too.. Titanium being hard, would require 'o' rings, and they perish and fail eventually, so you've traded a maintenance problem there.