Why aren't more blades made from titanium?

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Jaymz

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There's a lot of ceramic blades and obviously steel, but in the week or so that I've been browsing, I've only seen one full titanium knife.

Isn't titanium better than steel for everything?
 
mongomondo said:
Titanium is soft
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Really? I thought it was harder than steel. Much harder.

Edit: Seems like there is only some beta c ti that reached 55 rockwell back in 2006. I wonder if it's commercially available nowadays.
 
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40rhc

the only purpose for it is explosive ordnance guys, and divers. and there are better alternatives for both.
 
Jaymz said:
There's a lot of ceramic blades and obviously steel, but in the week or so that I've been browsing, I've only seen one full titanium knife.

Isn't titanium better than steel for everything?
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Nope. Ti is used mainly to reduce weight and for it's heat and corrosion resistance. Useful to make light, tough handles and to reduce corrosion and weight on a diving knife that's going to be strapped to your calf or ankle but that's about it
 
It's also non-magnetic. But in terms of most characteristics that average users want out of blade steel (edge retention, ability to take and keep a fine edge, etc), it doesn't compare to most common high end steels.
 
it has lots of modulus, or flexibility. i work in the bicycle industry and some titanium bikes are good for the shock resistance of the road but it is not as stiff as carbon fiber or aluminum. And aluminum, is lighter anyway.
 
In certain situations, a Titanium blade is ideal. Beta Titanium is a great performer.
 
There are many materials harder than steel and yet we don't see blades made out of them. Hardness is not the only characteristic that makes a material suitable for blades. The word "steel" refers to a very broad family of materials. Not all steels are suitable for making good blades.

Ti, while it can be hard, does not take and retain a good cutting edge.

Certain alloys of carbon-steel are the preferred materials for cutting tools because their molecular structure includes carbides. Carbides are the key. Ti does not form carbides.
 
I have a Mission MBK, a skeletal handled 4" blade. It's a nice kitchen utilty because it cleans up easily and I don't have to worry about drying it off each time the way I would with carbon steel or a folder. MBK stands for Mission Book Knife to give you an idea of the orgiinal purpose. Unfortunately, it will not get the kind of edge I like for extended food work.
 
Rather than repeating myself, I'll just repost what I said here.

Planterz said:
There's a lot of myths surrounding titanium. Firstly, as we're discussing, it makes for a very poor blade material. The most common alloy is 6Al4V (6% aluminum, 4% vanadium), and while it's very strong and light, it sucks for knife blades. It really can't be heat treated, it's soft and when you get down to the edge, it's weak and brittle for cutting applications. The advantages are that it's light, non-magnetic, and won't rust (there's no iron) or otherwise destructively oxidize (all titanium in fact instantly oxidizes, just like aluminum, but the layer of oxidization doesn't corrode or discolor). This makes it a good choice for hold-out, last ditch self defense knives (where you only need to make a cut/stab or two), diving knives, and Navy divers who need to disarm magnetically activated mines. But for a tool that gets used daily, it's a bad choice.

Mission's Beta Ti is a slightly different beast; it can be heat hardened and is more suitable as a blade material, but at its best, it's comparable to the lowest quality flea market crap knife steels (and even then, the crap steel might outperform Beta Ti, and it's certainly easier to sharpen). If you absolutely MUST have a working knife made from Ti, Mission is the way to go.

If you simply want a blade that won't ever rust (magnetism and weight be damned), there's better options than titanium. One is Stellite 6k or Talonite, which are cobalt alloys. They're harder than titanium, softer than all but the softest knife steels, but it's greatest property (other than being rust-proof) is it's slickness. Because it's so slick, it doesn't dull as quickly because there's less friction. So even though it's softer, its edge retention is as good as most any mid level blade steel. They use these cobalt alloys in the blade fans of jet engines because they wear down less than aluminum, steel, or titanium (air friction can actually grind away at the blades in jet engines). If Stellite 6K or Talonite is just too expensive (it is expensive, and quite difficult to work with), there's the very economical option of H1 or X1.5 steels (which use nitrogen instead of carbon) used by Spyderco and Benchmade. Despite being mostly iron, these "steels" simply will not ever, ever rust.



The other myth regarding titanium is in how strong it is. Titanium is not necessarily stronger than steel. Steel of the right alloy, with the right heat treatment will always be stronger than titanium. So if strength is what you want (weight be damned), steel will be the way to go. Where titanium has the advantage is in the strength-to-weight ratio. The easiest example to look at (for me, anyway) is in bicycle frames. The 3 most common metals used are aluminum, steel, and titanium (there's also scandium, and of course carbon fiber, but that's not what we're talking about here). A steel frame will always be stronger. Theoretically, you could make a titanium frame stronger than a steel frame by using more titanium, but that defeats the point in having a titanium frame in the first place. Titanium is used in some bikes because you can make a very strong frame (and other components)--stronger than aluminum--lighter than a steel one. Aluminum is commonly used (extremely common) because it's much lighter than steel, and sufficiently strong. The advantage of using titanium over aluminum is weight and strength, but it's far, far more expensive. Titanium also has different properties that make for a different ride (titanium is a lot springier than Al, steel, or CF). For example, on a rigid frame (no suspension) single speed, a Ti fork will absorb more shock than a steel fork, but it'll be bouncier. This comes down to personal preference. Anyway...


The myth of superior titanium blades will continue because the myth perpetuates itself. People who make movies don't know better, or if they do, they assume the audience won't. For example, Wesley Snipe's silver-etched titanium sword in the "Blade" movies. Also, there's the Shick Quattro Titanium razor blades. Pay attention to the commercial. They say the blades are titanium. They're not. They're steel, like any other razor blade, but coated with titanium nitride (TiN), which is a common knife blade coating, and also used on high-speed tools for machining. But the public doesn't know WTF titanium nitride is, and titanium sounds "cool" (because of people who believe the myth), so that's what they say in the commercial.
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Blades have been made from silver and bronze, too, but none of them are consistent performers like steel. Even ceramic is too brittle for everyday use, outside of very specialized circumstances, using great care.
 
Ti can be made sharp and you can shave with a blade of titanium or cut paper but not for very long though because the edge is soft and it will roll on harder materials and other than being a great pry bar and non magnetic as well as light weight and completely free of rust problems there is really no other advantage to it. It makes a fair dive knife for prying up rocks, buried treasure, clams or whatever else and when serrated they can cut rope well and stuff like that and if you must have ti get the beta ti blade. The talonite and stellite are over rated to me. I'd sooner take an H1 Pacific Salt and a Rock Salt to the rain forests over anything of these materials personally.

There used to be a web site that showed a bar of steel and then showed a bar of aluminum and a bar of titanium by the steel bar with each the size they would have to be to all be the same strength as one another. The steel was far smaller than the aluminum and significantly smaller than the titanium.

As I recall titanium has a higher strength to weight ratio than steel which simply means if you had a bar of titanium and a bar of steel and both weighed exactly the same that the ti would be stronger. Aluminum has a higher strength to weight ratio than steel also but this doesn't mean it would be a good choice for a blade. It says nothing for how much space that bar of ti would have to have to sit in though. So to give you an idea of a 2 ton jet made of steel or a 2 ton jet made of titanium you would see that the titanium jet would be about 2/3rds bigger in size and foot print of the all steel one. The closest site I could find to the information I was looking for is here.
http://www.swordforum.com/metallurgy/titanium.html

STR
 
Give me steel any day. The only time when a titanium blade would help save much weight would be on large knives where the forces at work make it a totally inappropriate material.
 
Besides the aforementioned reasons I'd think cost might have something to do with it as well.
 
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