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Old 28th Feb 2024, 11:14 pm   #21
Richard_FM
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Default Re: Brittle Brass Syndrome?

Ammonia is one substance that attacks brass.
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Old 29th Feb 2024, 8:42 am   #22
Electronpusher0
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Default Re: Brittle Brass Syndrome?

Quote:
Originally Posted by m0cemdave View Post
Yes, brass does require annealing to remove work hardening caused by manufacturing processes such as drawing and bending. A place I worked in for a while (Boosey & Hawkes, they made brass musical instruments) had an oven based around a long conveyor belt that ran through the main factory area.

So some failures of brass parts might be due to inadequate annealing, to add to the other causes previously mentioned. above.
Slightly OT so please delete if inappropriate.
I attended a lecture at my local archaeology club last about the middle bronze age and our ancestors were drawing and annealing bronze about 1400 BCE.

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Old 29th Feb 2024, 11:26 am   #23
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Default Re: Brittle Brass Syndrome?

Hello

This was tickling my mind and I've now found the reference on my bookshelves.

"Season Cracking" first identified in rifle cartridge cases after storage. The failure process being stresses/work hardening from manufacture being released by almost imperceptible corrosion attack sometimes years later. The solution was to anneal the cases between 200 - 300C.

This is my abridgement of an item in "Metals In The Service Of Man", Pelican books, 1960 reprint.

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Old 29th Feb 2024, 9:42 pm   #24
emeritus
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Default Re: Brittle Brass Syndrome?

The 1942 edition of "Machinery's Handbook" has an extensive section dealing with SAE alloys, including 8 pages of different types of brasses and bronzes. It lists the proportions of the various alloys their fields of application, and how some types can be tempered and annealed, but there is no mention of time-related embrittlement.
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Old 1st Mar 2024, 10:20 am   #25
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Default Re: Brittle Brass Syndrome?

I had a surprising experience of de-zincification in the Himalayas, back in the 1980s:

I was having breakfast at the big table in the kitchen of the mission guest house in Kathmandu. I was sitting opposite the Belfast-style sink on the far wall, when the bib tap, all by itself, dropped off the wall, landing with a splash in the sink, and causing a horizontal jet of water to come from the hole. The lady who ran the guesthouse kept a level head and knew where the stop tap was, and I went off to work.

When I came back later, the plumbers were in: hole excavated in the wall, around the cast iron pipe, which had been tapped for a cast iron coupler and a stub of pipe, that brought the tap out to several inches away from the wall surface.

The original plumber had left the joint at the back of the tap buried in (or at least touching) the damp plaster, completing the circuit with the cast iron and causing the zinc to leach away.

The following morning all was back to normal.

Here, I've had several old radiator fittings crumble when a spanner was applied. De-zincification is quite a nuisance!
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Old 1st Mar 2024, 6:33 pm   #26
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Default Re: Brittle Brass Syndrome?

I've got an ITT KB "Golf Preset" radio my father bought in 1972. It still works perfectly apart from a scratchy volume control. The chromed brass telescopic aerial has some of the larger diameter sections split along their length.
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Old 11th Mar 2024, 2:29 pm   #27
m0cemdave
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Default Re: Brittle Brass Syndrome?

I have just found this in one of my boxes of spare valves.
Brimar 6J5GT, code 2G7.
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Old 11th Mar 2024, 2:36 pm   #28
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Default Re: Brittle Brass Syndrome?

Those generally break at the joint in the ring and I've successfully resoldered them. You have to tightly bind them with wire to keep the ends together during the soldering operation.
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Old 11th Mar 2024, 7:43 pm   #29
G6Tanuki
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Default Re: Brittle Brass Syndrome?

My preferred 'fix' for split brass shrouds on Octal valves is a short length of adhesive-lined heatshrink; make it long enough to cover the entire brass shroud, and go up 3mm on to the glass bottle.

Pop it in the oven at 140C for 30 minutes [temperatures and timing may be different for non-fan ovens] and your valve will be good for years to come.
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