Author Topic: Mystery metal... how to identify without damaging the sample?  (Read 7800 times)

Offline AdeV

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Mystery metal... how to identify without damaging the sample?
« on: September 22, 2010, 12:15:21 PM »
I have a machined piece which I need to replicate. It's made out of a silvery metal, probably some form of cast iron.

Its density seems to be in the 7100kg/m3 region, although it's hard to be precise as my kitchen scales only measure whole grams or 10ths of an ounce. 7100kg/m3 also puts it in the cast iron range, or maybe its "white metal", or something similar...

I've attached a picture of it. It's harded than brass, but seems to be softer than "regular" steel, although it's hard to tell for sure.

Unfortunately, I can't damage this example, so I can't put it on a grinder, or on the lathe for example. It's part of a regulator for a Petter stationary engine - beyond that I know nothing about it. I don't know if the weight of the device is critical, I assume the piston bore is critical but I'm not sure about the length...

Any ideas?
Cheers!
Ade.
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Offline Jasonb

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Re: Mystery metal... how to identify without damaging the sample?
« Reply #1 on: September 22, 2010, 01:40:23 PM »
Certainly not white metal or a similar alloy they would be far to weak for a part like that.

Also I would have thought regular cast iron would be too prone to fracture at the end of teh thread, could possibly be SG iron (Spheroidal Graphite) which is stronger but I'd recon its just steel.

Whats the actual part as this may give a clue to weather the finer machined section has possibly been case hardened.

You could also ask on one of teh stationary engine forums like Smokestak as they may know what that specific part is made from.

Jason

Offline No1_sonuk

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Re: Mystery metal... how to identify without damaging the sample?
« Reply #2 on: September 22, 2010, 02:38:45 PM »
Is it magnetic?

Offline Yorkshireman

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Re: Mystery metal... how to identify without damaging the sample?
« Reply #3 on: September 22, 2010, 04:29:16 PM »
Take a clean Q-Tip, dip it in strong vinigar, then swipe the Q-Top along the part. That will propably not damage it. Clean the part ...
Now produce somehow a small (almost) colourless gas flame in a dark room. Then touch the edge of the Q-Tip to the flame.
If the colour of the flame changes to GREEN, then the material is containing COPPER.

Johannes

Offline AdeV

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Re: Mystery metal... how to identify without damaging the sample?
« Reply #4 on: September 22, 2010, 05:11:14 PM »
Thanks chaps; yes, it IS magnetic, so definitely cast iron or steel. Probably just ordinary steel TBH. Reckon I'll just make one & see what it weighs...

Ta!
Cheers!
Ade.
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Offline raynerd

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Re: Mystery metal... how to identify without damaging the sample?
« Reply #5 on: September 22, 2010, 05:43:22 PM »
Now produce somehow a small (almost) colourless gas flame in a dark room. Then touch the edge of the Q-Tip to the flame.
If the colour of the flame changes to GREEN, then the material is containing COPPER.


Rubbing alcohol would give you a clean (colourless) flame.

I teach flame tests for GCSE Chemistry - finally a true to life practical example!!   Li - red, K - lilac, Na - orange, Cu - green

Good luck and I think u should give it a go for the sheer hell of it - I`ll even send you some nichrome wire for the occasion! :nrocks: :loco:
« Last Edit: September 23, 2010, 07:32:54 AM by craynerd »
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Offline AdeV

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Re: Mystery metal... how to identify without damaging the sample?
« Reply #6 on: September 23, 2010, 06:26:48 AM »
Well, I gave it a try with what I had to hand... I have a butane/propane blowtorch which burns with a decent blue flame, not unlike a bunsen burner really. So, first try was a dry cotton bud (slight yellowing of flame); then a bud wetted in vinegar (no change to flame), then wetted in vinegar & rubbed on the metal piece (no change to flame). As that was a bit dissapointing, I tried a vinegared bud rubbed on some copper pipe. No change to the flame  :(

Maybe the vinegar isn't strong enough.... it is Tescos 13p/pint special stuff after all...
Cheers!
Ade.
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Offline RichardShute

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Re: Mystery metal... how to identify without damaging the sample?
« Reply #7 on: September 23, 2010, 06:17:37 PM »
If it actually _really_ matters, find a local university physics, chemistry or engineering department with a 'Link Analytical' attachment on their electron microscope. They should be able to give you chapter and verse on the composition down to fractions of a percent in minutes. Won't be able to define heat treatment obviously and if it has been plated, it's the plating that will be analysed.

Richard
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Offline bilhar

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Re: Mystery metal... how to identify without damaging the sample?
« Reply #8 on: September 24, 2010, 02:54:52 PM »
looks mild steel chemiblacked.   cast iron has a reddish tinge to it while heat treatable steel are more difficult high to bring to high gloss shine so my guess is mild steel chemblacked
 


Offline DavidA

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Re: Mystery metal... how to identify without damaging the sample?
« Reply #9 on: December 23, 2010, 07:58:03 AM »
First test for SG iron is to breath on it then sniff it.  If it is SG then it will smell distinctly of acetylene.

Dave.

Offline bry1975

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Re: Mystery metal... how to identify without damaging the sample?
« Reply #10 on: January 22, 2011, 02:35:06 PM »
Definitely sounds like cast iron which can have a density of 7,100kg/m3, steel is denser so more like 7,400kg/m3 upto 8,000kg/m3 for SS.
« Last Edit: January 22, 2011, 02:37:03 PM by bry1975 »

Offline DavidA

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Re: Mystery metal... how to identify without damaging the sample?
« Reply #11 on: May 28, 2011, 03:09:07 PM »
AdeV,

What did it turn out to be made opf ?

Dave

Offline AdeV

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Re: Mystery metal... how to identify without damaging the sample?
« Reply #12 on: May 29, 2011, 07:13:40 AM »
I never did find out I'm afraid; it transpired the chap only wanted the brass outer piece making, he'd already got the internal gubbins.

I'm pretty sure it was either cast iron, or steel, based on the colour & feel, but once I found out I only needed to make the brass outer, I didn't think much more about it.
Cheers!
Ade.
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Location: Wallasey, Merseyside. A long way from anywhere.
Or: Zhengzhou, China. An even longer way from anywhere...
Skype: adev73