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Silver soldering Stainless Steel

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Dennis Rayner01/09/2011 16:35:49
122 forum posts
8 photos
I have the problem of joining together end on 2 pieces of 5/16" diam. stainless steel within a 1/2" diam. brass coupling reamed out to 5/16".
I have some Easy - flo - will this solder OK to the Stainless Steel?
Alternatively can anyone suggest an alternative method of securing? I'm a big taper pin fan myself but this component is the regulator rod into the boiler and I'm obviously concerned about the pins rusting through over time.
Mike01/09/2011 16:47:41
713 forum posts
6 photos
I have often used Easy-flo to join stainless of various grades with success. However, I can't vouch for the strength of the joints, so over to the real experts!
Dusty01/09/2011 17:29:53
487 forum posts
9 photos
First things first, Brass should never be used in a boiler it will over time de-zinc and become like swiss cheese and loose any strength it may have had.
Secondly why on earth are you joining two pieces of stainless steel together, is there any reason why it should not be made from a single piece. If the only reason is 'I had it to hand' then throw it back into the scrap box and purchase a new length. A regulator rod failing with the locomotive on the track could be disastrous for you, the locomotive and anyone who got in its way. Silver soldering stainless steel is slightly more problematic than other materials but with the correct grade of flux it is achievable without to much heartache.
Dennis Rayner01/09/2011 17:52:02
122 forum posts
8 photos
Of course, you are absolutely right and I will start again with a new piece of S/S. The reason for trying to resurrect the machined part was the frustration of machining the item to the drawing and then finding the drawing was wrong! Ugh!!
I'm intrigued by the problem of brass within the boiler. I am building Elidir which has a Stroudley type regulator. The drawing specifies brass for the regulator links and has the option of brass for the lower block. My "Boxhill" completed in 1979 has brass regulator links and has lasted OK for the last 32 years. Is it possible that the use (or non-use) of brass in the boiler has to be more specific.
Jeff Dayman01/09/2011 18:27:56
2189 forum posts
45 photos
There are many types of brass and many types of water in different areas of the world. Both of these factors, and the rest of the materials used in the boiler will affect how fast or if brass will lose zinc. Immersion will cause brass to lose zinc faster, generally. The old rule of thumb was brass is OK in the boiler's steam space but not OK below the waterline. Dennis - Your Boxhill regulator's brass parts may be fine due to the fact that they are mostly in the steam space, not immersed, and it could be that your local water is one of the ones that allows slow zinc loss.
my 2 cents -
When in doubt or if building new, use bronze or phosphor bronze, not brass, in boilers. For external boiler fittings for steam or cold water brass is OK but not if immersed below the boiler waterline.
If you need to join critical components like stainless reg. shafts inside a boiler, make from one piece, or find a TIG welder and ask him to weld it together, or pin it with a stainless pin and peen the pin ends.

Edited By Jeff Dayman on 01/09/2011 18:32:19

Bogstandard01/09/2011 21:37:56
263 forum posts
You can in fact buy brass stock now that resists the zinc depletion almost or totally completely, but I personally would stick to the above explained rules.
To get back to the original question.
I use Tenacity 5 flux for everything I silver solder together, it really is a wonderful flux and doesn't exhaust itself even at extended times and temperatures. It is really designed for silver soldering stainless, but it seems to work with all the normal materials, and after use it is one of the easiest fluxes I know of to clean off.
Clive Hartland01/09/2011 21:44:11
2751 forum posts
40 photos
Just out of interest, I watched a programme about making Cow bells.
It was partly riveted at the joints and then brazed.
The brazing materiel was a rifle cartridge! It flowed beautifly into the joint and made a good job of it.
The cartridge had been hammered flat and placed along the join and then heated.
A another bit of useless info but it might help someone one day!
Richard Parsons02/09/2011 08:21:40
645 forum posts
33 photos

Dennis Hi!

Do not try to braze stainless steel as this is a receipt for disaster. Stainless steel covers its self almost instantly with an oxide film so molecular joints (like brazing) do not have any strength to them. There are some stainless steels that can be soldered/brazed/silver soldered and there are fluxes which can help. But the joint is doggy unless you are a real specialist with the right rods. There is a thread on steel boilers on this website here started by Dave Bond. It contains a lot about brazing, welding etc.

Dusty yes ‘condenseritis’ however de-zincification can be prevented by adding 0.03% arsenic to then brass. Most brazing rods except the very cheapest are guaranteed against this problem. This site is very interesting about de-zincification. . The main culprit is not so much hot water but a combination of hot water and Oxygen from the air. The hot water dissolves the Zinc Oxide formed by the action of Oxygen on the Zinc in brass. Zinc Oxide then forms Zinc Hydroxide. Arsenic inhibits this process. I suspect that all my brass stock came from a now defunct supplier who used to supply various university departments. I think it contained arsenic.

Clive Yes I saw a smith in the old bazaar in Kirkuk hammering out old cartridges to use as spelter. I presume that the brass used in cartridges has a lower melting point than the normal half hard brass.



John McNamara02/09/2011 09:33:54
1328 forum posts
122 photos
Hi All
Cartridge Brass 30% Zinc?
Brass is an excellent conductor of heat. A flame applied at any point on a case for a short time will cause the rest of the case to heat very quickly. There are several temperatures at which brass is affected. Also, the time the brass remains at a given temperature will have an effect. Brass which has been "work hardened" (sometimes referred to as "cold worked") is unaffected by temperatures up to 482 degrees (F) regardless of the time it is left at this temperature. Remember, water boils at 212 degrees (F), and oil heated in a frying pan easily reaches 500(F) or more degrees. (All temperatures will be in Fahrenheit). At about 495 degrees (F) some changes in grain structure begins to occur, although the brass remains about as hard as before -- it would take a laboratory analysis to see the changes that take place at this temperature.
If cases are heated to about 600 degrees (F) for one hour, they will be thoroughly annealed -- head and body included. That is, they will be ruined. (For a temperature comparison, pure lead melts at 621.3 degrees (F)).
The critical time and temperature at which the grain structure reforms into something suitable for case necks is 662 degrees (F) for some 15 minutes. A higher temperature, say from 750 to 800 degrees, will do the same job in a few seconds. If brass is allowed to reach temperatures higher than this (regardless of the time), it will be made irretrievably and irrevocably too soft. Brass will begin to glow a faint orange at about 950 degrees (F). Even if the heating is stopped at a couple of hundred degrees below this temperature, the damage has been done -- it will be too soft. From this discussion we can see that there are four considerations concerning time and temperature:
End Quote

Edited By John McNamara on 02/09/2011 09:34:41

Laurence B02/09/2011 11:02:06
58 forum posts
I use Argobraze 56 silver solder (it is silver solder despite its name!) and some Easy-flo ''Stainless Steel Flux Powder' for silver soldering stainless steel.It's not cheap but the joint is fairly easy to make.I have used standard easy-flo rods to join stainless steel bits together but it's not so easy to use,nor is the standard flux quite aggressive enough.
As the others have mentioned,the use of brass on boilers is not to be recommended.
Ian S C02/09/2011 11:04:03
7468 forum posts
230 photos
Thats quite interesting Dick, I always thought it was an electrolitic reaction that caused the break down, which is one reason I also wonder about steel boilers with copper tubes, although these would be helped by a zinc anode being installed in the boiler.
Ian S C
Adrian Gough02/09/2011 18:45:52
4 forum posts
I used to work in a hospital and regularly silvered soldered stainless steel with no problems.
We used Easy-Flow Stainless Steel grade flux.
Both these materials were suppled by RS components. (no connection)
We could also soft solder Stainless using a proprietary grade of Bakers fluid made for Stainles steel. In the days that Hospitals had a full chemical lab the chemist would make up flux for us. This meant dissolving Zink in Hydroclic Acid (Basic Bakers Fluid) adding a few drops of a detergent and then adding extra Hydocloric Acid.
We could soft solder Stainless aseasily as copper.
We had to soft solder very thin wall tube 3mm OD to a block of Stainless 25MM x 12mm x 6mm,so that the tube was not overheated by using a gas tourch we used a hot air gun with very good results.
The joint had to e cleaned extreamly well after of course.

Speedy Builder505/09/2011 19:14:41
2454 forum posts
196 photos
Oh dear ! all those old aircraft from the 60's. Most of the pipe unions were silver soldered to BS316 stainless tubes with easy flo number 2 (OK it did have cadmium in it), but the silver solder flowed like melted butter, using standard flux, and tenacity number 5 for larger jobs. Just do not overheat the joint as it is quite difficult to remove the burnt flux / oxide.
robin coleman22/05/2021 19:09:18
18 forum posts

I have a stainless steel garden trowel can this be silver soldered as it was a present from a late relative



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