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Mystery metal
15

Mystery metal

Mystery metal

(OP)

I have a piece of metal in my hand that appears to be bronze.  I am confused about this, because the hardness of it is around 54-58 RC, and it is hardened throughout!

The piece is used as a driveshaft transfer coupling, and splines run the length of the ID.  This means the part was probably broached, but I can't be for certain.  I have been asked to modify the part, but even when grinding with a diamond wheel the work is SLOW.  (This isn't a problem, it's just that I am totally impressed with the toughness of the metal.)  

The dimensions (for what it's worth) 2" OD, 1.125" ID, threaded 1/4-20 full lentgth, 8 splines run the ID.  The piece cost $800 three years ago.  (It has an oil trough drilled inside)

I would ask the manufacturer what mat'l it is, but the manufacturer is out of business.  I have asked some toolroom guys what it is, and their best guess is some kind of beryllium steel, but I disagree with that because beryllium steel would offer no great advantage over regular steel where the part is used: a non corrosive, dry, cool, clean and dark environment.  The shaft that it couples runs continously, with no jumpy, jerky starts or super-high RPMs.

Young's Modulus is extraordinarily high on Beryllium Copper, but is it on beryllium steel as well?

RE: Mystery metal

There is no beryllium steel. Maybe they meant to say boron steel. Boron is used to increase the depth of hardening. It's probably alloy steel but to know which one with accuracy you should use a spectrograph.

RE: Mystery metal

Why do you think it is bronze?  Because of the color?  I agree with mcguire, it is likely to be an alloy steel, possibly one that has been coated if it looks copperish.

RE: Mystery metal

(OP)
I have been doing some reading, and I think what I am dealing with is actually an Aluminum-Bronze Alloy.

http://microstructure.copper.org/overview/al_bronze.htm

I can't wait to tell those guys back in the shop that there is no such thing as Beryllium Steel.  Maybe I should have them order some for me.

RE: Mystery metal

rhodie,

Can you calculate the density (measure volume and mass)? That might narrow it down significantly.

Best regards,

Matthew Ian Loew

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: Mystery metal

(OP)
MLoew:

I calculate it at about .293 lb/in^3

I hope that helps you more than it did me.

RE: Mystery metal

2
Is it magnetic?

RE: Mystery metal

(OP)
I don't think so.  If it is ferrous, it is a really low composition.

RE: Mystery metal

rhodie,

Aluminum bronze alloys are incapable of attaining a hardness of 54-58 HRC.  Beryllium copper alloys have the highest hardness when precipitation hardened, with maximum hardness of ~ 42 HRC.

RE: Mystery metal

I would have hazard a guess at aluminum bronze also, but the colours do not match.  Aluminum bronze is a pale golden colour, but it certainly is tough.  I have made aluminum bronze and couldn't cut with hacksaw, only an industrial hand grinder.  It would be slightly magnetic, due to the nickle and iron content (5%).

RE: Mystery metal

(OP)

Thanks for the replies.  I'm still not sure of what it is after reading TVP's reply.  When I find out for certain, I'll let everyone know.

RE: Mystery metal

2
Rhodie,
Maybe you've already figured this out, but I'll add this as nobody has commented on it . . .

You state a density of .293 lb/in^3. This equates to 8100 kg/m^3.

Here is a brief listing of some metal densities (in kg/m^3):

Aluminum: 2800
Cast Iron: 7200
Steel: 7850
Brass: 8470
Bronze Manganese: 8800

I think this supports the suggestion of an aluminum bronze.
Brad

RE: Mystery metal

Aluminum bronze with 5% aluminum is 8.17 g/cc. Bradh wins the prize.

RE: Mystery metal

Bradh, the densities that you listed are average values for these groups of materials. The steel grades that we manufacture vary in density from 0.276 lbs/in^3 for 440C to 0.294 lbs/in^3 for M2. The density itself won't tell you that it definitely is or isn't aluminum bronze. Why not save some of the chips and send them to a local college that has an SEM for an EDAX scan? They probably won't charge you a cent for the service, and it would give the students some practice in identifying an unknown.


                                            Maui

RE: Mystery metal

(OP)
Maui

Your suggestion that I send a sample off for analysis is something I did this morning.  

I am sending a sample to a lab at Texas A&M.  We'll see how quick the aggies can make something of it.

-Just some clarification on the color; it is a pale golden color, competely thru.  I apologize if I confused anyone.

I gathered some more (similar) pieces today, and I find that an average of fifty or so Rockwell readings result in an average RC of 52.  That said, the particular piece I am curious about has a RC avg. of 56, and it one of four pieces that read this highly.

The given density of .293 lb/in^3 is a good number.

Today I told the machist (that yesterday offered his guess of Beryllium Steel) to order me a 5" x 5' barstock of the material.  I emphasized to him that I didn't want Beryllium Copper or Boron treated steel, I wanted Beryllium Steel or nothing at all.  He said it should be "no problem, it'll be here in 4 days."  I can't wait to see where this situation goes.




RE: Mystery metal

rhodie,

Are you sure your hardness measurements are correct?  Are you performing a Rockwell C test, or converting another test to HRC?



Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: Mystery metal

(OP)

I am using a Rockwell C hardness tester with a diamond cone indenter.  Should I be using a Rockwell B scale or even an A scale?

The instrument could be "off", but I doubt it.

RE: Mystery metal

(OP)
CoryPad:

I see you point.  I should only be getting 80-90 RB to 30 RC depending on the particular alloy of aluminum bronze.

RE: Mystery metal

Maui,
I realize that those are average values; I was merely providing information which is relevant in HELPING identify the metal.

As his metal is on the ABSOLUTE high-scale for steels, this would suggest that it is more likely to be an aluminum-bronze alloy than a steel alloy.

Brad

RE: Mystery metal

Sure sounds like al. bronze and an incorrect hardness test.

RE: Mystery metal

Maybe Nickel beryllium of some sort.. Not sure thou the hardness is really high even then but the color is close and again the stuff is really tough...

nick

RE: Mystery metal

I agree with Metalguy and CoryPad.  Likely to be aluminum bronze, and your hardness test is flawed.

RE: Mystery metal

(OP)
This problem has started a huge stink where I work.

The tester I was using is a production test fixture, as WIP parts that come out of an HT oven are checked on it immediately after quench.  I am not too familiar with the work flow process, but both aged aluminum and HT steels are checked at this particular station.  

It seems that someone in a non-technical role made the decision to start checking aluminum on the Rockwell tester using a C indenter, therefore consolidating test instruments.  I told the area supervisor that whatever results he was gaining from the tests were meaningless.  (He told me that no one ever complained before me.)  I asked him what happened to the aluminum hardness tester, he said that it had been gone for a good year, probably in storage somewhere.  I dug out a handheld Webster checker and told him to start using that in the meantime, please!

Upon inspecting the indenter more closely, I found that when the aluminum sheet was tested on the Rockwell, the metal was so malleable (and the sheet thickness so thin) the intenter would punch right through the specimen and hit the hardened steel "table" holding the piece.  The indenter is basically crap, and probably has been broken for a while.

I was getting pretty mad at this point, but I realized that the area supervisor didn't know any better.  I asked him for the last year's worth of data, which I'll analyize later today.  (I am not going to be surprised if the data doesn't deviate more that 5 points for the entire sample of two different metals.)

My best guess is that the production guys were "fortunate" to have the Tester read incorrectly within the range they were aiming for, coupled with the idea that they thought the hardness of aluminum and steel should be equal.   The test wasn't a GO/NO GO qualifer, it simply was data gathering for process adjustment purposes.  No one had ever explained to these guys the theory, intent, and necessity of the test they were conducting.  They were simply recording numbers.

(As far as product liability, all of this metal is used in a decorative fashion, no load bearing beams or structural members have been compromised...)  I still have a huge problem to backtrack through.  God knows how many other production areas have been affected by this screw-up.

The root cause of the problem here is that the engineer who is responsible for this area never leaves his office.  I have not been working long, but I know to be on the floor everyday as much as I can.  You simply cannot do your job well if you operate far from where it is occuring.  He could have caught this a year ago, but since he is rather removed from the operation it slipped right on by him.

Anyway, I just wanted you all to know this problem, hopefully explaining the weird results I reported above.  I will re-test the "bronze" part in question later, and hopefully ascetain what it indeed is composed of.

Thanks for all your replies.

RE: Mystery metal

bradh, we're all here to help. No offense was intended.


                                           Maui

RE: Mystery metal

maui,
print tends to not convey ideas and emotions as well as voice; no offense was taken from your comment. Rereading mine, I see how it may have sounded like I was offended.

Sorry about that,
Brad

RE: Mystery metal

Wow.  I really have no words after reading rhodie's last post.  Sometimes I am just dumbstruck by how messed up things can get...

Best of luck, and thanks for the update.

RE: Mystery metal

3
TVP,Metalguy,mcguire,maui,CoryPad
Five of the top experts in this forum with others like NickE and Bradh(who should have figured on the list too), and the result is one of the best technical metallurgical discussion I have seen on the site.  A star to all of you!!!

Thanks and regards
Sayee Prasad R
Ph: 0097143968906
Mob: 00971507682668
email: sayee_prasad@yahoo.com
The whole of science is nothing more than a refinement of everyday thinking!!!  

RE: Mystery metal

Sayeeprasadr,

YOU certainly make the list too!  

RE: Mystery metal

Snatching the backs? lol

That is what all I could contribute. Nice discussion.

Regards,

RE: Mystery metal

All's well that ends well. What's next?

RE: Mystery metal

(OP)
I got a fax, telling me the results of the testing on the "mystery metal":
-----------------------------------
Copper Alloy No. C63000
(Nickel Aluminum Bronze)

Composition (in Nominal Percentages):
82% Copper
3%  Iron
10% Aluminum
5%  Nickel & Cobalt

98 RB  Hardness  (You guys were right on!)
118 KSI Tensile strength
75  KSI Yield Stength (.5% EAU)
16% per 1.5inch Elongation  ( I thought this was a weird specimen length...)

Physical Properties

Thermal Conductivity BTU/ (sq ft-ft-hr-F):     22.6
Specific Heat BTU/lb/ºF @ 68F:                   .09
Thermal Expansion Per °F from 68 F to 572 F:     .0000090
Density lb/cu in @ 68 F:                         .274
(I guess my calcs. were bad...)
Electrical Conductivity* (Annealed) % IACS @ 68 F:     7
Modulus of Elasticity (Tension) KSI:             17,500

*Volume basis

Fabrication Properties

Capacity for being cold worked: Poor
Capacity for being hot formed: Good
Machinability Rating (Free Cutting Brass=100) 30
Suitability for being joined by: Soldering/Not Recommended
Brazing: Fair
Oxyacetylene Welding: Not Recommended
Gas Shielded Arc Welding: Good
Coated Metal Arc Welding: Good
Resistance Welding Spot: Good
Seam: Good
Butt: Good
---------------------------------

I thank you all for your help in this matter!  I hope I can help one of you guys one day, but I think I have a long way to go before then!



RE: Mystery metal

Rhodie, your post and initiation of discussions was good enough help for all guys out here! Everyone participates in this forum in his/her own way and that is what makes this forum so active and live!!! Anyway thanks for keeping all of us posted on your test results!

Thanks and regards
Sayee Prasad R
Ph: 0097143968906
Mob: 00971507682668
email: sayee_prasad@yahoo.com
The whole of science is nothing more than a refinement of everyday thinking!!!  

RE: Mystery metal

2
You were, in a small way, lucky.

Never, but never, use a diamond wheel to cut a ferrous product.  The iron and the diamonds will react to form an iron-carbide.  The wheel will be ruined.  How do I know?  I blush ...

Use cubic boron nitride instead.

(Why did the guys in the tool crib allow you to use their diamond wheel on an unknown alloy?  It sounds like you have a management problem, not a materials problem.)

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