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Moon bunny

Judging your grammar.
I'm guessing that's the NRM Workshop?

I like it when you post in this thread @Moon bunny: It's always something unexpected and interesting...

I feel privileged at times, getting to handle some of the most valuable and beautiful objects the nation owns, from rockets and the big mill engine down to a ceramic cat.
 

TheDoctor

Europe Endless
Moderator
Location
The TerrorVortex
Ringo and Jasper.jpg

Jasper and Ringo. Ringo is a 18 month Lab who's really a big powerful puppy. Pulls (quite) a bit on walks.
Jasper is nearly 9 now, and just about the nicest dog ever.
If there's a storm he gets frightened and jumps on my bed, then looks unhappy when I stop stroking him.
 

palinurus

Velo, boulot, dodo
Location
Watford
Measuring the composition of some tin-based alloys (in the original form of solder pastes)

First I melt the solder, pour off the flux and then tip the molten metal into a little round mould to give a little slug like this.

View attachment 648426

Then- to make it nice and flat and expose a fresh surface- I machine it with a lathe (it's a soft alloy so very easy to machine and the swarf doesn't give you splinters!)
View attachment 648428

Then I pop the sample face down on the spark stand of this atomic emission spectrometer (spark AES) and give it a whack with the electrode (it goes bzzzzzzzzzzzzzzzzzzzzzzzzzzzz-zzzzzzzzzzzzzzzzzzzzzzz-zzzzzzzzzzzzzzzzzzzz)- some magic happens and it displays the composition of the alloy (selected elements I'm interested in, anyway- silver, lead, bismuth, nickel, antimony, copper- several others)

View attachment 648429

Meant to have been a 15 minute job but the bismuth composition was low so a recalibration, preparation of new samples, re-testing of a known-good sample followed- took up a lot of time. Still not resolved so will pick it up again next week.

So this job took longer than expected. I've been waiving through any samples with slightly low bismuth in the meantime, sending some to our lab in Hungary for verification (they get a result between 2.80 and 3.25% which is the specification range for this alloy). I didn't have a reference standard with the right sort of bismuth content, I searched a database and found one- 3% bismith, some zinc and the rest tin. I don't care about zinc but it doesn't do any harm. Took ages to order it, we've just been taken over by a new company and we had no purchasing procedures. Finally it was delivered last week.

It's a little cylinder of alloy, with a certificate. It cost over £500. Bismuth content is certified at 3.03%.
IMG_20221121_081103797.jpg

As before turned it on the lathe (not very deep- that's expensive swarf right there)
IMG_20221121_081256960.jpg


IMG_20221121_081244171.jpg

(the swarf, incidentally, is very nice- the alloy is very soft and ductile and it remains in one continuous thread of metal)

Put the sample on the AES and flushed with argon, gave it a zap with the electrode -three zaps- in different places, everything in triplicate at least. The bismuth came out at 2.65%- there's the problem.
IMG_20221121_082300765.jpg


IMG_20221121_085313721.jpg

It's easy to adjust- add a correction factor until the result shows 3.03%. Then I rechecked some earlier samples.
IMG_20221121_085331902.jpg

Seems OK now, three samples from earlier this year which were originally low are now within specification.

This is a minor part of my job, mainly do this because we're short of technicians and because I like machining the samples.
 
Picking out posters for the 2024 calendar:
View attachment 668904

Thanks for this: my parents send me that calender as a little slice of "home" so it's nice to know who puts it together...
 
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