Annealing

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David Thorpe
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Annealing

Postby David Thorpe » Thu Oct 08, 2009 10:34 pm

Making slow but fairly tidy progress with my new Hudswell Clarke kit, I came across the instruction: "Anneal the firebox wrapper and then, using the firebox former as a guide, bend it to shape....." I'm afraid that I haven't done any annealing before. There appear to be a number of theories - some say you heat the brass until its red hot (presumably using a blow torch, we've no gas hob here), and then drop it in water, while others say that it should be allowed to cool more slowly, and so on. I'd very much welcome any recommendations. I assume that once it's cool the brass will have lost its spring and be more amenable to accurate bending?

David.

David Knight
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Re: Annealing

Postby David Knight » Thu Oct 08, 2009 11:29 pm

David,
I allow the brass to cool at its own pace as the thin brass used in kits does not take long to lose its heat. The brass in High Level kits responds well to this process as I discovered when doing the tank on my Neilson.

HTH

David

nigelcliffe
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Re: Annealing

Postby nigelcliffe » Fri Oct 09, 2009 9:04 am

Quenching things rapidly is usually used for hardening, not softening (annealing). Bending metal usually results in it becoming harder (which is why you can snap thin sheet by flexing it back and forth).
To form a complex bend you need the metal to be softer not harder, so, heat up, then let it cool naturally.

Heat with a gas flame. Don't try to turn it red-hot or similar, it only needs moderate temperatures.

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David Thorpe
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Re: Annealing

Postby David Thorpe » Wed Oct 14, 2009 9:31 am

Thanks for the replies, David and Nigel. The annealing went very smoothly, although thanks to the DIY style blowtorch it also went very quickly and I'm afraid that the brass was red hot in seconds. I allowed it to cool naturally (again, that didn't take long) after which it was all nice and workable.

David

allanferguson
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Re: Annealing

Postby allanferguson » Thu Oct 15, 2009 11:54 pm

Brass, copper, etc can only be hardened by working them (bending, stretching, hammering -- like my back.....). They can be softened by heating as described. Carbon steel can be hardened and tempered by heating. But it can also be softened -- try it with a piece of piano wire.

Allan Ferguson

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Allan Goodwillie
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Re: Annealing

Postby Allan Goodwillie » Fri Oct 16, 2009 9:51 am

:geek: Annealing material takes it above the re-crystallization temperature. The material should be maintained at a suitable temperature for a short time, and then allowed to cool. Annealing makes the material more ductile, it softens it , relieves internal stresses, and refines the structure by making it homogeneous (even throughout). It is particularly useful for folding n/s frets, for example the three bar slide of a Gresley valve gear. ;)

I used to make silverware at Art College, 8-) silver and nickel silver tend to be harder materials than brass and that harder than copper and that about the same as phosphor bronze. So most times silver would require annealing before bending otherwise breaking was a very real possibility. Beating it on a former to form a goblet would require heating several times otherwise cracking could happen as beating the material would stiffen it to that point of over-stress and hardening. Nickel silver behaves in much the same way, the original sheet being normally quite hard before etching. If making something in N/S sheet that requires bending I would tend to anneal it first using a small gas torch. It is always easy to re-heat and plunge into cold water to harden it again before soldering.

Brass tends to be softer and requires less annealing and is easier to work in some ways - does not look to pretty as N/S where the solder is about the same colour as the material.

Copper is even more flexible and will oxidise on these few occasions when annealing, forming a coating of Copper oxide which has to be removed which is a bit of a pain.

Phosphor bronze wire can disintegrate when annealing and does not require much heat to do so. I wonder about phosphor bronze being used for pick-ups on wheel flanges, particularly steel where arching can occur. Arching often involves temporary high temperatures between small areas of surface. This may not effect a small loco at low voltages pulling a couple of wagons, but put it on a substantial train and working at constant 24 volts of a digital system and you have perfect conditions for annealing of the wire and gradual loss of springing. I know this is all very theoretical, but I hope practical information as well - perhaps there is a trained metallurgist :ugeek: out there to give a more refined view.

Hope you are enjoying making the locomotive :D - looking forward to seeing the results sometime

Allan Goodwillie

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Will L
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Re: Annealing

Postby Will L » Fri Oct 16, 2009 10:24 am

Thanks for the run down on Annealing Allan it was really useful. By the time you had got to the last paragraph I was beginning to wonder about my own habit of using fine PB wire for pickus!

None the less it seems to me it is the best material. Anybody any clear ideas why this should be. I've never seen problems with them loosing temper or disintegrating in use (DC only). I do try and maximise the number of pickup fitted wheels each side with springing or compensation to keep them in contact with the rail, so often six a side on a tender loco. That way perhaps you never get enough sparking on any one wheel to produce significant heating.

Will

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Allan Goodwillie
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Re: Annealing

Postby Allan Goodwillie » Fri Oct 16, 2009 12:03 pm

Hi Will,
I have tried using them as p/b is supposed to be a better conductor , more like copper but not so soft. I have however reverted to N/S ones for some time now and more recently been fitting them with Gold tips :idea: as renewals come around, this has given the very best performance, but then again I run 40 wagon trains up 1 in 75 gradients on my mainline so there is a fair old current draw on that, so I have to go for robustness. The locos I've built for Burntisland have n/s strip pickups and give little trouble from that point of view,although the little Neilson has a tendency to lift off on one side if the chairs are not properly stuck down!

Using the gold tips I can say this is the best I have tried - there is a whole thread on this subject elsewhere on this forum. as long as it works for you Will that's what matters.

All the best :)

Allan

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David Thorpe
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Re: Annealing

Postby David Thorpe » Fri Oct 16, 2009 2:08 pm

Allan Goodwillie wrote:Hope you are enjoying making the locomotive :D - looking forward to seeing the results sometime

Thanks. It's the first kit I've built after a lapse of about 15 years and I must admit I'm finding it quite difficult and slow going! I am however making steady progress, although I'm currently held up for want of a 14BA bolt - will hopefully get one at the local Model Railway show this weekend, although I'm a bit disappointed that it wasn't included with the kit.

David.

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Will L
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Re: Annealing

Postby Will L » Fri Oct 16, 2009 6:49 pm

DaveyTee wrote: although I'm currently held up for want of a 14BA bolt - will hopefully get one at the local Model Railway show this weekend, although I'm a bit disappointed that it wasn't included with the kit.


This is a High-level kit yes? Because I'm sure if it has a 14ba bolt on the instruction then its supposed to be there. I have found High-level very helpful about such things in the past. Ring them, the numbers on their web site. http://www.highlevelkits.co.uk/

Will

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David Thorpe
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Re: Annealing

Postby David Thorpe » Fri Oct 16, 2009 7:26 pm

Yes, it is a High level kit. So far it has required the use of four bolts - three M2s and a "14BA C/S bolt, cut to about 4mm long". Only two M2 bolts, each about 20mm long, were supplied. I've got a pack of M2s, so they're not a problem, but if I can't get a 14BA bolt at the Dundee show this weekend (I'm impatient to get on!), I'll give Chris a ring.

David.


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