OT- can someone tell me what this metal is??

I dug this hard drive spindle out of a dead harddrive. Its the thing that sits right on top of the spindle with like 3 little Torox screws on it. When
I got it off this thing looks shiny grey, like some grade of stainless steel but they are totally non magnetic... I mean I stuck the strong magnet from the same harddrive on it and it acted like it was nothing. The metal is hard too, a file just remove a little bit of the metal and seems to damage the file rather than the file doing anything to it. It weights very little, almost like aluminum but its NOT aluminum. The color isn't the same (the whole harddrive spindle is aluminum and this metal is darker)
I am suspecting Titanium, what do you think?
heres a picture...
http://i107.photobucket.com/albums/m320/rahimiiii/IMG_0039.jpg
http://i107.photobucket.com/albums/m320/rahimiiii/IMG_0040.jpg
http://i107.photobucket.com/albums/m320/rahimiiii/IMG_0041.jpg
The last picture is the thing under a strong magnet, note it did not even react to the magnetic force. It's not the same material as the magnet base plate because it sticks to magnet like crazy.
--
TAI FU



Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Stainless steel is non-magnetic.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
this thing is too light to be stainless steel.... also stainless steel looks white compared to this one. I had a peice of titanium before and its exactly this color.
--
TAI FU
"NaCl" < snipped-for-privacy@sbcglobal.net> wrote in message
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Take a grinder too it, if you get white sparks she be Ti!
I'd duno what to say it is! What HD did it come off?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
a Hitachi Deskstar... 60gb
--
TAI FU
< snipped-for-privacy@aol.com> wrote in message
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

SOME stainless steels are non-magnetic,some are magnetic. If it's light it could be magnesium or titanium. Probably magnesium. (it's castable and easily machined compared to Ti.)
--
Jim Yanik
jyanik
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Common misconception. SOME varieties of stainless steel are non-magnetic; nickel is sometimes added (to make it shiny) and that kills the magnetism. Other formulations are magnetic.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
If this thing goes right on top of a harddrive platter it would make sense to use something that is totally non magnetic....
--
TAI FU
"Scott Schuckert" < snipped-for-privacy@aol.com> wrote in message
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

Nickel is magnetic.
--
Joe Michel



Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Yes, it is. Your point being? Stainless steel containing nickel is NON-magnetic.
"...when nickel is added, for instance, the austenite structure of iron is stabilized. This crystal structure makes such steels non-magnetic.... "
http://en.wikipedia.org/wiki/Stainless_steel
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

But that's irrelevent. As wikipedia says,
There are different types of stainless steels: when nickel is added, for instance, the austenite structure of iron is stabilized. This crystal structure makes such steels non-magnetic and less brittle at low temperatures.
So it's what the nickel-steel alloy does for the crystal structure, not the properties of either metal.
--
Joseph J. Pfeiffer, Jr., Ph.D. Phone -- (505) 646-1605
Department of Computer Science FAX -- (505) 646-1002
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
www.nepra.com www.rocketmaterials.org http://home.sprynet.com/~monel/home.htm
wrote:

Non magnetic stainless steels are called "Austenitic" stainless steels. They have a crystal structure phase called austenite. Magnetic stainless steels are called :Martensitic" stainless steels. They have a crystal structure called martensite.The difference between the two is the level of nickel. Nickel is an austenite forming element.
Doc
--


Drake "Doc" Dameru
President, NEPRA
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

As an EE, I didn't have to learn much about materials. Other than Si, I only got a small thimble full of material science. But if it hadn't been for that, I'd be thinking Austenite was somebody from central Texas :)
Seriously, Doc, what about heating / cooling / quenching the stainless? Would the various forms of heat treating, since it affects the properties, have any effect on the magnetism?
Doug
--
Posted via Mailgate.ORG Server - http://www.Mailgate.ORG

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
www.nepra.com www.rocketmaterials.org http://home.sprynet.com/~monel/home.htm

Not really. What happens is this: When you heat an iron alloy, the iron crystal changes. The crystal is shaped by the arrangement of the atoms. At "room temperature", the atoms are arranged in one shape, and at high temperature, the atoms rearrange them selves into another. This new shape arrangement at high temperature is called austenite.
The austenite (atomic arrangement) changes back when it's cooled. This is called an "allotropic phase change". When you start to add other elements, like nickel, the temperature at which the austenite changes back is lower. Generally, the more nickel you add, the lower the temperature at which the phase change happens. If you add enough nickel, the temperature is lower than room temperature. So you have austenite, or austenitic steel.
So... What does all this have to do with magnetism? Simple; austenite is non magnetic. That's why iron magnets loose their magnetism at high temperatures, and why hot steel (above the austenite phase change temperature) is non magnetic.
Also see "Currie point".
Quenching austenitic stainless steels wont really do much. Actually, heating them to a low temperature (like 800F) will harden them. That's called aging and that's a completely different thing called diffusion.
But we digress.
If there is little or no nickel in the iron alloy, but a quantity of carbon or chromium (lots of chromium in stainless), the austenite with undergo a phase change directly to a phase called martensite. Thus, martensitic stainless steel. Martensite is magnetic. The phase of martensite is also known as a super-saturated interstitial solid solution.
Wasn't that fun!
Doc
--


Drake "Doc" Dameru
President, NEPRA
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

So far as magnetism is affected by crystal structure, quite a bit. The cornerstone of the steel industry is not the production, but the post-processing: the controlled (accelerated or not) cooling and subsequent reheating "recipe" of the different alloys.

It takes time for this rearrangement to take place. Quenching (in water, oil, salt, or lead baths) is a key process in stopping this recrystallization from taking place and 'freezing' the desired microstructure in place.

An allotropic phase change is simply a solid-solid phase change, as opposed to solid-liquid, solid-gas, etc. While the addition of alloying elements will affect various transition temperatures and corrosion and physical characteristics, they will not affect what is controlled by energy and time. Solid-state phase changes, for most nearly all materials systems, require the energy (heat) and time to make their transitions. If you cool it very quickly (and don't reheat it much), it will lock in the structure you had at the high temperature. In the steel industry, these types of processes are mapped on Time-Temperature-Transformation (TTT) diagrams. An example of a simple process is:
http://www.materialsengineer.com/E-Steel%20Properties%20Overview.htm
and a good diagram with microstructures is here:
www.key-to-steel.com/Articles/Art51.htm
Actually, the "Stainless Steels" link on the first website has a good overview of this stuff.

I think a couple concepts are getting mixed or over-simplified here, but we are already into to much metallurgical detail for a RMR thread.

Tai, send me an email, I'll give you my address, and you can send me a part of the piece. I'll put it in the SEM and we'll get an elemental analysis. :-) Frankly, I'm a little surprised it's not aluminum since all the spindle cap needs to do is hold the top platter down and the screws in place. And since precision (it's a machined part) is critical here, a hardened steel or other metal is quite unusual.
Justin
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Quenching dosent freez the the microstructure, it transforms it from face centered cubic to body centered tetragonal.

While thats true, the most important aspect is that it is reversable and the material can have two phases at the same time.
While the addition of alloying

This is not exactly true. Our example uses nickel as an alloying element. Nickel forms a substitutional solid soulition. No amount of time will change that.
Solid-state phase changes, for most nearly all

This is not true. The structure at high temperature is face centered cubic austenite. If cooled slower than a TTT diagram sugests, it will form body centered cubic ferrite. If cooled rapidly (quenching) it will form body centered tretragonal martensite.
In the

That's why I over simplified it. (Being a chief metallurgist at a 26.6 billion dollar sales per year company.) I didn't want to get technical.

--


Drake "Doc" Dameru
President, NEPRA
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Doc wrote:

True, inthe case of a pure Fe-C system. Quenching some low-alloy content stainless steels fast enough (granted, not possible with large billets) should keep the microstructure intact, but it will put the FCC austenite into a "metastable" situation, but transitions of less then 50% to martensite over long periods of time are typical. As you mention below, in high-Ni or certain Ni-Cr ratios, austenite is stable to room temperature, demonstrating the effect of austenite stabilization.

You are quite right, I tied my thoughts up in a knot here and called them non-related when they were. Alloying and impurity control are critical to most material systems. Materials and thermo 201 there...don't know what happened in the gray matter.

I'm not sure this disagrees with my above paragraph, as martensite is not truly aviodable in a pure Fe-C system, but in Fe-Ni-Cr-C systems it is. But I think we say that depending on the alloying, and cooling rate, we can get either martensite or austenite. Some restrictions may apply. :-)

This one still has me thinking...can all austenitic stainless steels even be hardened by heat treatment? If the microstructure can not be changed appreciably, and we can not achieve grain refinement, what will the hardening mechanism be?

I believe I straightened myself out, now.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

?
Don't forget pearlite/ferrite. Martensite is hard to create in iron-iron carbide alloys containing carbon up to .5%, and impossible to create when the carbon is below .2% like in "mild steel". Over .8% (eutectic) martensite is easy to create. But, regardless of the iron alloy, martensite can only be created if quench fast enough to transform the austenite to martensite. Inversely, and alloy than can form martensite, can be annealed to completely eliminate it.

...or pearlite, ferrite, bainite, trootsite... and most importantly, Fe3C

You're not kidding there. I've been doing this for longer than I will admit, and I still get metallurgical "issues I don't predict.

Other than some "freaky" supper alloys, the answer is no. Austenitic stainless steel alloys can not be hardened by heat treat (quenching).

The only way to harden austenetic stainless steels is to workharden them. Some stainless steels, like 17-4PH can be age-hardened. This is a type of low-heat heat treatment. But still, the hardening is not created by quenching, its a precipitation mechinisim.

Not if you're into metallurgy. You'll never be straight. It's 99% science, 1% magic.
Doc
--


Drake "Doc" Dameru
President, NEPRA
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

Isn't that what the Six Million Dollar Man's legs and right arm were made from?
--
Darren J Longhorn http://www.geocities.com/darrenlonghorn /
NSRG #005 http://www.northstarrocketry.org.uk /
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I thought they were made with titanium (all the more reason to charge 10,000 dollars extra)
--
TAI FU
"Darren J Longhorn" < snipped-for-privacy@privacy.net> wrote in message
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.