Titanium was harder than stainless steel would have been?!

peacefuljeffrey

peacefuljeffrey

Joined
Feb 24, 2001
Messages
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All I've ever heard about titanium knives is that they are not as hard as stainless steel, for the most part. Now there is a current article (online and in the papers) that says the Concorde crash occurred because the tire was punctured by a piece of debris from a DC-10 that was soooo hard, essentially because it was titanium!

Here's a linked article:

Runway debris a factor in Concorde crash

I want to know what knife-people and metallurgists make out of these claims, which seem to come from the "experts" hired by people suing over the crash. Are they employing mysticism and myth about titanium in order to make illegitimate claims? Would a piece of stainless steel have been incapable of doing what titanium did? Here's a quote from an article I have clipped from the local paper:
" 'The strip that should have been in stainless steel turned out to be made of titanium, a stronger alloy that made the plane's tire burst and set off a chain reaction that led to the Concorde crash,' said Jerome Boursican, a lawyer for a pilots' union that is a civil party to the legal case over the crash."

Seems to me like it's typical B.S. from a hearse-chasing lawyer who is expecting everyone else to be too dumb to know that stainless steel is harder, in general, than titanium. He seems to have seized on the talk of titanium being stronger "ounce-for-ounce" than steel and turned titanium into some sort of super-metal.

What do you all think?

Blue skies,
-Jeffrey
 
peacefuljeffrey,

Names like stainless steel and titanium are meaningless. To make an accurate assessment the alloys must be defined.

662 titanium is superior than many of the lesser grades of stainless steel. It is however inferior to blade steels.

Clear as mud right? ;)
 
titanium is very tough...they make high performance engine valves out of it.
the appeal if it is that it is WAY lighter than steel.

the downside is that it's expensive......

check out the price of a set of steel valves for your car engine, and then price a set of titanium valves for it :-o
 
The point is, there are too many variables here. The titanium COULD be harder than steel tempered to very low hardnesses. Simply naming metals is completely useless.
 
...and "strong" and "hard". Carbon fibre is extremely strong (for its weight...even not for its weight), but it's definitely not hard.
 
It's typical B.S. from a hearse-chasing lawyer.

If it were titanium or stainless steel or brass or aluminum -- it's still harder than the tire. What's the difference how much harder?

There was a thread a while ago about some consumer product that praised itself for being so sharp because it was titanium. :eek: And just think -- before that I believed every advertisement I heard. :)
 
Pretty vague. However, if they are comparing aircraft grade Ti to unhardened steel then the Ti is much harder. I am no expert but the reason Ti is so expensive is not its rarity but difficulty in machining/processing due to its natural hardness. (Mid 40 Rc I believe) You only have to try to cut steel and Ti with a bandsaw once to see the difference. Steel can, of course, be made much harder than Ti can with heat treating.
 
jerrinfla said:
titanium is very tough...they make high performance engine valves out of it.
the appeal if it is that it is WAY lighter than steel.

the downside is that it's expensive......

check out the price of a set of steel valves for your car engine, and then price a set of titanium valves for it :-o
Click to expand...

You are correct, in that Ti is used in high performance engine parts.
But I wanted to add that Ti isn't stronger then steel. Ti is only stronger in terms like : If you took 6oz of Ti it is stronger then 6oz of steel.

But if you took a 2inchx2inch block of each of the metals, steel would be stronger. The downside of the steel, is that although stronger, it is heavier. You know what I mean?
-Kevin
Edited to add: I just realized I could explain it simpler...
Ti is stronger if measured by weight
Steel is stronger if measured by mass

So if you make a door out of steel to a certain size, and one of Ti to a certain size, the steel door is stronger.

If you are asked to make a 60lb door out of Ti and a 60lb door out of Steel the Ti door would be stronger becuase it is larger and can be thicker.
 
Comparing blade steels with titanium is too complicated for must of us to understand so I won't even try...

Mission Knives uses a titanium alloy and they say it's hardened to 45RC. Check out their website for more information.

My experience with titanium is mostly with knife handles, folders such as Sebenza's...they scratch very easily and look old or worn quickly.

Different steels, metals, polymers etc., have their uses. For blade steel I prefer good old fashion carbon steel that's been proberly heat treated!

Cheers,
Collecter
 
Well, first of all the cutlery that is Ti coated (and that isn't a scam) is not Ti coated but TiN coated, which is MUCH harder than even hardened steel. Which brings me to the second variable here: regular SS is pretty soft, only the hardening (heat treat) lets the steel change from one crystal structure partially to another. To compare heat treated to non heat treated steel is surprisingly similar to comparing graphite to diamond, obviously a small change in hardness there as well.

This is only covering hardness and we haven't covered toughness, tensil strength shear strength etc. Ti is a great material in its own right. While I wouldn't want a knife with a Ti blade, I would take one with a Ti handle and a good blade steel anytime.

As to the Concord...common guys. We all know that it takes only a nail or even a piece of plastic to puncture a tire under the right conditions. And once any crap, made from any material, large enough to have sufficient inertia (let it be steel, Ti, rubber or a bird) gets into the intakes of the Concord and actually makes it to the fan blades, you can kiss that engine goodby. Fan blades of...let's say 0.25 m diameter turning at 15000 rpm (both lower end approximations) will give a fanblade tip speed of "only" 25000 mi/h! And yes those are really three zeros.
 
The difficulty in machining Ti is because of the plasticity or ease of deformity compared to ss. There is also less demand for machine tools design for Ti, therefore they cost more. Ti is still termed as an exotic material in a machine shop.
 
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