Posted on 08/12/2010 7:59:04 PM PDT by Swordmaker
Let's discuss your claim that the stainless steel in the chart I posted is a "low strength steel." That claim is BOGUS!
Although the 17-4 Stainless Steel on the chart is tested as a casting and its hardness at 120ksi is therefore lower than rolled or extruded form at 140-160ksi, the rating of this stainless steel makes it among the strongest of the stainless steels. In fact it is a "Precipitation-hardening martensitic stainless steel, which have corrosion resistance comparable to austenitic varieties, but can be precipitation hardened to even higher strengths than the other martensitic grades."
17-4PH, uses about 17% chromium and 4% nickel. There is a rising trend in defense budgets to opt for ultra-high-strength stainless steel such as 17-4PH when possible in new projects. So much for your claim of "allow strength steel!" The Defense Department's contracts are still in place and research and development is taking place on new weaponry using casting of liquid metal as we debate, much to your chagrin.
Sounds like mithril in the Lord of the Rings:
Mithril! All folk desired it. It could be beaten like copper, and polished like glass; and the Dwarves could make of it a metal, light and yet harder than tempered steel. Its beauty was like to that of common silver, but the beauty of mithril did not tarnish or grow dim."
Bilbo gave Frodo some mail made of mithril to protect him on his journey to the Cracks of Doom.
I wonder if this liquid metals stuff will have any applications in the manufacture of body armor?
If it could be extruded/drawn into fine fibers, I'd love to have a pair of snake leggings knit/woven of it...
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IIRC, Bilbo (in The Hobbit) took Sting from the trolls' hoard, and Thorin gave him his Mithril mail shirt from the dragon, Smaug's hoard -- and Bilbo passed them on to to Frodo (in FOTR).
Look, you putrid sack of idiocy. Hot Rolled shape and plate steel accounted for $46 Billion of $77 Billion for all Steel product sales in the US in 2005. The vast majority of this was shipped as A36 or an equivalent grade. Rebar, spring steel, tool steel and even threaded fasteners are only specialty items with specifically designed characteristics. They have their place, but the law is that when you increase the yield strength of by adding carbon you pay the price of ductility and resistance to fatigue. Tool steels use specific alloys to enhance the strength of the steel coupled with special heat treating that can produce impressive properties but the expense and other limitations of this product limit its use to essentially what you find it typically used for, tools and dies.
On Free Republic it is wise to ask someone before you haul off and open you fat yap, because you might be talking to someone who is an industry expert with more than 30 years of experience.
What is a mark of ignorance is looking at the values provided by swordmaker and not being impressed at 270ksi yield strength with almost twice the elasticity of copper in a cast form.
I am sure that the problems that others have hinted at around here probably center around very limited options for joining components via welding processes, but I have to plead ignorance about this aspect of this material. But the amorphous structure could allow easy melting and joining or make it nearly impossible, and as folks are saying that the golf club people got frustrated with this alloy, my money is on the difficult side in absence of real knowledge. But, for making cell phone or computer cases, its hard to see the downside.
Golfer seem to live in perpetual obsessive search of The Magic Club that will hit balls further, more accurately and give them a hole in one every nine holes.
That aside, the theory went that because this metal rebounds so well in collisions, (which is demonstrated in the above video of a ball of the metal bouncing off a hard surface) it wouldn’t put energy into temporary deformation of the club face and instead put more energy into the ball.
I will always subscribe to the assessment that golf is a way to ruin an otherwise perfectly nice walk.
On the flip side, that chart on the elasticity of this material couldn't be much more confusing. This is not a measure of ductility, but in fact a measure of "springiness" the amount of deformation the material can take without deforming.
A plain carbon steel will provide 25% elongation to rupture, where as hi-tensile, high carbon steels (like rebar) can only achieve 10% elongation to rupture. This is the trade off. But it is hard for me to imagine that only .5 percent of this strain is below the yield strength, so I am scratching my head too. On the surface this chart would seem to imply that all of these metals are fairly brittle, and I just don't get that. Maybe I got up on the wrong side of the bed.
To me, the manufacturing process (ie, molding) is the clear attraction here. Apple can get any form they need from machining of an aluminum alloy or stainless, but even CNC machining is very high overhead compared to using this type of.liquid metal “glass” and molding. If Apple were suddenly to gain 50% market share tomorrow, they would not be able to keep up with demand with their current manufacturing processes.
As for all the strength this class of alloys has: I thought of one (exactly one) application after I posted above and that is the frame/shroud for large thin displays. Think of a notebook with a 20”± screen. No one has complained to date of breakage of aluminum cases. Unless one work hardens aluminum, it it plenty tough for consumer product. The heat conductance of aluminum is an added bennie with modern hot chips too.
What some have complained of is screen breakage as a result of case flexibility, so the possibile other upside here would be the ability to make a very thin (relative to aluminum) shell around a large screen that doesn’t flex so much that the screen fails mechanically.
In the world of gun parts, where machining has been the manufacturing process for over 150 years, a couple of parts manufactures are going to MIM for the smaller parts that are not subject to chamber pressures or that need spring properties. Think of things like triggers, safeties, guide rods, etc. The quality seems OK to me and the reduced costs give the company making mass-production parts a higher net margin after they get set up.
Machining is still my preference tho. I just like making chips. ;-)
Yea, ok maybe Sword spends his weekends beating plowshares into blades. ;-) If he does, more power to him. The world neds more people who know how to make fine weapons.
My beef here wasn’t about the liquid part of the technology. I can see the upside to that straight away. The issue I had was the idea that Apple was solving some strength or ding resistance problem with this material. There really isn’t any problem with aluminum in this regard, and there is always titanium for the yuppie poseurs who want to one-up the rest of us mere mortals packing aluminum-cased Macbook Pro’s.
FWIW, I’m an Apple user, own two Macs, wife owns one, we will be buying more in the future. So I’m not some Apple basher, but I’ve been around Apple since the Apple II, so Steve’s Reality Distortion Field rarely works on me any more.
The one downside of this type of material I’ve read about is that the lack of plastic deformation means that you get little to no warning before yield failure. It seems like the ultimate in a work-hardening failure.
I could foresee a problem with this property in a small widget that gets dropped repeatedly, then one day the case shatters. An aluminum or stainless case would dent or scratch, but not shatter on the (eg) 50th drop.
The other issue I could foresee is in laptops with hard disks. If one dropped a laptop encased in this type of material such that it bounced really well, that’s going to drastically increase the G-loads a hard disk needs to withstand w/o crashing the head.
Yes, I've made swords. But it was about 42 years ago. . . and they just had to produce a suitable "CLANG!" when struck together, so the nature of the steel was of little importance. They were for my college drama department. They needed about 40. I cut them out of 1 1/4" x 3/16" x 36" steel bar stock, added welded on 1/2" x 6" x 1/8" cross guard to each side 6" from the bottom, added a weded on 1 1/4" round button pommel, glued on wooden grips, wrapped that with black duct tape, ground the end to a dull point — voilà! Fairly safe stage Swords with suitable "CLANG!" It took me about a week to turn out 40 of them. We bought some fancier ones for the principal actors.
I studied a lot about the physics and chemistry of metals in college. But that was also 40 years ago and mostly theoretical. Now I work for an implant dentist who was an aerospace engineer. He is very much into materials science and knows quite a bit about these liquid metals. He developed many of the modern techniques used in dental implantology and is always looking for lighter, stronger cartable metals for such uses.
Getting back to swords, and sword making, I've also collected edged weaponry and studied their manufacture and know quite a bit about steel and the trade offs between strength, spring, hardness, the ability to hold an edge, etc. Read about the construction of Japanese swords sometimes and the folding of the metal in the various layers that goes into a katana and the qualities each part of the interior and exterior metals of the sword provides to the overall finished product. Created through empirical trial and error over centuries of sword making, the results of fine Samurai blade technology still challenge the efforts of modern metallurgy to duplicate.
Dave, I think Apple's purpose here is less esthetic than practical. Apple will be able to reduce the thickness of the walls of the cases, increasing the volume of the inside space, allowing more room for battery capacity, giving longer operational time before recharging.
Like the challenge of the pyramids, the issue for modern technology is not one of possibility but instead practicality. Modern technology would not attack the problem in the same way as the Samurai sword makers did. Yet they attacked the problem in a novel way that made the best use of the willingness to expend time and resources available to create a superior product.
Steels are capable of incredible properties, as you pointed out in the issue of precipitation hardening of the 17-4 Stainless. Ultimately, this all comes down to structure. Steel is a conglomerate of soft iron and hard iron carbide in some form. Stainless Steels have enough alloy that they may still transition into ferrite or not and stay austinitic, yet the strength of this material still depends on the grain structure, and the placement of the carbides. Trace elements like vanadium increase the hardenability of the steel by stabilizing the carbides at higher temperatures. Ultimately strength and ductility typically go in opposite directions but the fineness of the grain and carbide precipitates increases the ductility. Steel achieves its strength from the hard bits and its ductility from the soft. Like butter filled with sand becomes hard but can be shattered with a small blow. The ferrite stretches and holds the structure together like rubber bands and yields when the forces become too high.
When a metal is quenched so fast that the hard brittle structure called martinsite cannot form from the austinite, it transitions to a very fine but brittle structure called bainite. Heat treated properly, this structure yields the finest structure of ferrite and cementite and thus the best properties possible for steel. However, it is difficult to quench plain carbon steel this fast and the hardening alloys such as vanadium, chromium, and others make this possible as they are increased and at some point make this possible even in a relatively slow oil quench.
The samurai sword masters achieve this very same sort of fine grain with their folding work, and overlay this with a very highly directional structure that provides the equivalent of modern composite structures in that the impurities and such are turned into a structural element that provides additional stability to the blade in its intended axis of loading by aligning them parallel with the flat surface of the blade. The risk being that the blade if the laminations are not broken up sufficiently can be vulnerable to splitting. Yet for most blows, these flaws are not stressed appreciably and instead the full strength of the material is available.
Engineers who deal with steel professional start seeing it like wood. Thinking of grain and the failings of grain like it fails in wood. Materials such as tools and highly worked and heat treated steel items do not suffer this effect as much because the grain size and configuration is more controlled. Quenching to martinsite or bainite prevents grain formation and thus the structures formed are very very fine after heat treatment releases the enormous internal stresses that the transformation causes and precipitates the carbides into a fine matrix of cementite among very small grains of ferrite.
Anyway, the cost of processing is the main deterrent to folks attempting to replicate the swords of the old masters. Other than proving a point, there isn't much demand for genuine swords of these characteristics. As you say, most swords now are good enough if they just "clang" well. LOL.
I could foresee a problem with this property in a small widget that gets dropped repeatedly, then one day the case shatters. An aluminum or stainless case would dent or scratch, but not shatter on the (eg) 50th drop.
The other issue I could foresee is in laptops with hard disks. If one dropped a laptop encased in this type of material such that it bounced really well, that’s going to drastically increase the G-loads a hard disk needs to withstand w/o crashing the head.
Unfortunately, I haven't seen anything that speaks to the ductility of this material or its ability to withstand strain past its yield point or its fatigue resistance. All of the things that you speculate may be true but if it were so it would be a terrible problem that would be obvious enough to cause Apple not to be interested. They already have built cases of titanium and aluminum so they know the capabilities of these materials as well as the cost of manufacturing using them, so I give them more credit on this matter than you are willing to go as of yet.
Perhaps I will get off my lazy butt and actually look into this question yet.
The Dremel-like tool is actually the tool in. CNC machining center.
A CNC can typically turn the tool at 8,000 RPM to 15,000 RPM, and has 3 to 5 axis positioning control down to 0.0002” ±.
With the tool turning at these types of speeds, the machine has multiple jets of coolant flooding the tool to keep it cool and flush the chips out of the working area.
Thus most CNC machining centers have big enclosures surrounding the actual working area. If they didn’t, the operator work be bathed in chips and coolant.
Injection molding doesn’t look as neat as CNC machining, but it can have much higher rates of production and lower costs per piece made.
You know Jonathan Ive has been having a field day with this stuff. Apparently it can be molded with micron-level detail for things like markings (that Apple logo), slip-resistant textures and even holograms. If Apple paid for an indefinite exclusive license, you know they're going to leverage it into some cool stuff.
Actually, they are. They do not represent anything close to typical alloys, and they are highly selective in what they show.
LiquidMetal has been around for a long time, and the high elasticity is intriguing, but it's not really higher than much more common - and easier to work - copper beryllium alloys (which - in addition to having a very high Young's modulus - has extremely high conductivity making it ideal for test probe tips and flexible antennas/connectors). They've been pushing it for a decade, and still haven't gotten a high-profile win because it really doesn't bring much new to the table.
And if you want a REALLY high Young's modulus, look at tungsten - twice the yield strength of LiquidMetal, and three times the Ym.
Your high carbon steel is hard but brittle and corrodes easily.
High carbon steels typically do NOT corrode easily; ever heard of stainless steel, or spring steel? Both are considered high carbon (in that carbon content is typically between 1% and 2%), but are well-known for not corroding.
The liquid metal here is hard but NOT brittle.
That's called Young's modulus. LiquidMetal is around 95 GPa, which is rather pedestrian in terms of metals available, being somewhere between glass and brass.
It's also corrosion resistant.
No more so than stainless, surgical, or other high carbon steels. And considerably less than many tungsten, nickel, or beryllium alloys.
It's also much lighter.
Not even close. I've got some of their technical data here (was investigating it for industrial linear springs about 6 years ago), and the density of their alloys line right up with typical steels, being around 7.9 grams per cc. About 3 times of most Ti alloys, and slightly higher than NiChrome.
Oh, and the Vertu phone has been using LiquidMetal for its frame for quite a while. Simply because it's expensive and "cool". But I guess Apple has to follow the lead of Vertu...;)
This is a "cool sounding" thing, but in reality LiquidMetal is not really useful over other alloys, which explains why it simply is getting zero penetration in the metals market. But now that Apple claims it, it has become an uber-metal because, well, Apple says so!
Then he should avoid LiquidMetal. It's density ranges from ~7.4 to 8.0 grams per cc, depending upon the alloy. That's right in range with other cast steel alloys, and about 2.5 to 3 times aluminum (and about 4 times magnesium).
Note that casting Al and Mg and AlMg alloys is rather well understood, and depending upon alloy selection, you can get Ym values close to LiquidMetal with about a 3X savings in density.
LiquidMetal's alloys (note, there is no alloy called "LiquidMetal") can be cast much thinner in more complex shapes. Estimates show half the weight for a MacBook Pro re-cast using these alloys.
Note that casting Al and Mg and AlMg alloys is rather well understood
As are the rather serious limitations that LiquidMetal's alloys don't have.
Having worked with some LiquidMetal samples in the past, their estimates and claims should be taken with a VERY large block of salt... There's a reason no one is using LiquidMetal - it doesn't live up to the hype.
As are the rather serious limitations that LiquidMetal's alloys don't have.
And those limitations would be?
Yeah, you bought a golf club. Beyond that I have a hard time believing.
There's a reason no one is using LiquidMetal - it doesn't live up to the hype.
Nobody's put much effort into it yet. Apple has a long history with new materials. I bet you were a LiquidMetal fan until Apple got involved.
And those limitations would be?
Regular metals don't cast very well due to their crystal structure. There are various methods to overcome many of the problems, most of which involve more time, effort and expense. Apple is not going to intricately investment cast 20+ million consumer products a year.
Apple moved away from plastic for good reasons, the aesthetics, heat conductance and strength just isn't there, but Apple's switch to metal has its own obvious problem: machining is expensive. So Apple is looking for a metal that can be manufactured as cheaply and accurately as a plastic. All evidence shows that LiquidMetal alloys can fill this role. That Apple has been playing with this stuff for a couple years and just decided to dump a ton of money on an exclusive license pretty much shows Apple found some great uses for it.
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