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[derekwarner]

Guys.......purchased a 750 mm length of 5/32"OD brass tubing from an OZ model components distributor

Have been soft soldering non ferrous metals for 40+ years but never found a brass that will not take or tin or solder easily....have tried Baker liquid flux, Yorkshire paste & Benzomatic paste....the solder is standard 60/40 non cored and also tried 60/40 rosin cored 

Despite absolute cleanliness  ....the flux just blackens & the solder just balls off  ....same result with a 200 watt soldering iron or any combination of fine gas pencils
....have experimented with standard brass plate & was able to tin the surface without any issue using any combination of flux & solder as above

1/8"copper tube from the same supplier and the K&S hobby shop brass tube range also solder just as they should with any combination of the above

The application here is from the gas tank to the burner & via a gas regulator which requires telescoping down to 2.0 mm OD for the regulator

A further complication is with the gas tank requiring removal for filling I needed some rigidity in the gas discharge tubing .......like I couldn't just let 2.0 mm OD tubing self support itself.....& further  the gas tube also had to be constrained as the 2.0 mm tube sealing in both ports of the regulator is by o-ring only

I won't throw the remaining length of 5/32" material away..........maybe just use it as a paint stirrer or something.......  Derek

[steamboatmodel]

Derek,
I had some years back that I had to skim some of it off in the Lathe before it would take any solder. Tossed the rest of it in the spares box and forgot about the problems I had had with it. I should have marked it a few mothes later had another line to do grabbed some tube annealed it bent it to shape and tried soldering it. You can guess which piece I had grabbed. got ticked with it could not bother straightening it out to skim it so just binned it and bought some new stuff.
Regards,
Gerald.

[colin]

Had same problem myself found out the tube had a clear heat resistant coating on it , not sure why but after sanding with wet and dry to remove was ok. Worth a try.


Regards
Colin

[Circlip]

Never ceases to amaze why people would use a material that work hardens so easily and splits for steam and gas connections. Must be cos in  bling terms it looks PRETTY. Yes, so does Copper, but at least in model terms, the wall thickness of Copper tubes compensates to a certain extent.
 
  Regards  Ian.

[xrad]

Agree with circlip. Some brass tubing (like K+S) is too thin for steam pressure. especially weak after soldering. There is thick wall brass tubing just for steam, and it threads well too. I use a lot of 3/16 thick wall for my builds threaded 3/16 40.
 
 

[steamboatmodel]

What pressures are you using that you are finding the K&S too thin for steam pressure?
I am not going to go through the calculations, but you would have to be using the very thinnest. Here is the chart for there tubeing sizes.
http://ksmetals.com/resources/cuttolength.pdf
Regards,
Gerald.
PS Over in the Model Engine Maker Forum Sandy gives the formula for calculating tubes subject to external pressure. I don't know if you have to be a member to view it.
http://www.modelenginemaker.com/index.php/topic,2731.0.html

[AlexC]

Hi Guys,
 
Soft annealed Brass has approx 2 x the UTS of copper so allowing a safety factor of 8 this would amount to 6250psi.
 
Given that:  P = 2t x UTS/ID for internal pressure
 
where UTS is 6250psi
t = wall thickness
ID = OD -2t
 
Then 5/32" OD pipe with a 0.006" wall thickness would therefore have a max internal pressure limit of 520.8psi.
 
So I don't agree that thin brass tube is incapable of high steam pressure use and soft soldering would not change that... the soft solder, on the other hand, would be a problem, at even moderate steam pressures... where steam is concerned, ALWAYS use silver solder.
 
I do agree that it is somewhat more prone to splitting, but that is a whole different ball game, and it is always subject to DE-ZINC issues where steam is involved.
 
Derek''' I think you will find that your tube has a protective coating on it... give it a good rub over in the joint area with some 400 or 600 grit wet and dry... then wash the joint area with some Xylene... allow it to evaporate then apply the flux.

Best regards.
 
AlexC

[derekwarner]

Thankyou all for the responses

The 5/32" OD brass tube in question is #24 [gauge ] or 0.039" wall....so the question of suitability for steam @ 150 PSI is not an issue
My mention of successful soldering 5/32" K&S brass tubing was for the exhaust spools & open to atmosphere

As previously mentioned, I need mechanical support for the 2.0 mm OD tubing out of the gas regulator to the burner ...this tube is not subjected to heat....but more so to chilling & icing

I will revert to 1/8"copper OD x #22 gauge [for mechanical strength] & complete the small task with the 2.0 mm OD tube

Here is another view of the brass plate which tinned perfectly after a lap on 400 W&D & the same problematic 5/32" brass tube  cleaned with the same piece of #400 W&D ......

Oh...it's amazing how a 1 meter long coil of 0.5 diameter wire can leave UK in on piece & by the time it gets to OZ....it has turned into individual  5/32" diameter rings  .....[thanks Sandy] Derek

[xrad]

Not to side track ....AlecC: you are I think describing ideal conditions and cold temps.  K+S: Low pressure side: no issue. High pressure side with silver solder  is not recommended , unless your torch is computer guided for equal heat penetration on that .006 wall.  Especially when some kid wanders near your unit and peers in for a closer look.....
 
None of the builder books/plans recommend thin wall for any HP steam component, especially boilers....Kozo/LBSC/Little Engines.
 
 I would at minimum consider .03 wall for the hot side 3/16 OD pipe.  1000+psi vs 500.....safety first.  75 PSI steam jetting out of a 2 mm rupture will travel 3-5 feet hot. 

[AlexC]

Hi Xrad,
 
No I was stating as it would be for steam at up to 90psi.
 
Brass typically has a UTS of around 62500psi in hard state.
 
I de-rated this to 50,000 psi to account for annealing and high steam temperatures.
 
I then added a safety factor of 8 giving a working UTS of 6250psi.
 
I have, over many years, silver soldered thousands of joints in brass tube down to 0.006" wall thickness with nothing more than a standard propane blowtorch with a smallish nozzle... No computer control necessary.
 
As a professional boiler and engine maker for many years I would not recommend BRASS as a suitable material for anything steam related (fittings, tubes or especially boilers) Copper is the correct material for boilers and steam pipework and bronze for boiler/steam fittings.
 
Keep happy.
 
Regards.
 
AlexC

[rickles23]

Hi,


I had the same problem but the answer is easy.


The parts you need to solder must be clean.


I always use a fine wet/dry sandpaper and a bit of elbow grease.


Again it must be clean as there is a thin coating on the tube.


Regards

[Circlip]

Said nowt about the steam pressure capabilities of Brass tube, only that it age hardens and cracks quicker than Copper. Looking at some of the "Flee" offerings on various sides of "The Pond", for a well known Japanese manufacturer shows the stains and discolourations that thanks to poor steamsmanship will lead to failure.
 
   OK. it's a purely personal opinion  but Brass doesn't come anywhere on my list of steam materials.
 
    Regards   Ian.
 
   And yes, I DID have a Mamod sixty years ago.

[NoNuFink]

 but that is a whole different ball game, and it is always subject to DE-ZINC issues where steam is involved.

I am curious and seek enlightenment - Why does dezincification matter?  Surely if you take the zinc out of brass you are left with copper?

I'm not having a pop at anyone - I just want to know, having attacked a shower mixer with descaler and turned the brass into copper  - probably only on the surface and it still works OK.  It just made me curious.

NNF

[geoff p]

Years ago, when I lived in Shetland, our water-supply was a bit acidic - it came from a peat bog, basically - and leached the zinc out of cheap brass fittings.

What was left looked like sintered copper, a porous, spongy, dull-coloured material that had NO strength at all.  And under ordinary mains water-pressure the fittings would fail, sometimes spectacularly.

Geoff
Thailand
 

[AlexC]

Quote fromNoNufink:  Today at 03:50:50 PM
 

 Why does dezincification matter?  Surely if you take the zinc out of brass you are left with copper?

Quite correct, however, the copper structure that is left is porous and weak leading to failure... especially when subject to high steam temperatures and pressures.
 
I would not worry too much about your shower... this is more than likely the acidic nature of the de-scaler disolving very small amounts of copper, either from the shower pipework or the copper tank in the shower, producing copper sulphate.
When this comes into contact with brass fittings it tends to copper plate them... any de-zinc would be minimal in this application.
 
Best regards.
 
AlexC.
 
 

[derekwarner]

 ....the Australian supplier after reading my plight has free supplied a replacement 750 mm length of 5/32" OD  x #24 brass tubing

It is a different batch lot as the replacement has microscopic longitudinal die marking on the OD which was not apparent in the original tube piece

Best news is.........the replacement...well....... .it tins...it sweats .....it solders perfectly........ ....

Having said this....none of the comments offered explain the non solderability of the original tube piece..... .............Derek

BTW...the following are the calcs I use...which essentially are the same as shown by Sandy a few days back......
_____________________________________________________________________________________________

Barlow's formula can be used to estimate burst pressure of pipes or tubes.
P = 2 s t / (do SF)         
where
P = max. working pressure (psig)
s = material strength (psi)
t = wall thickness (in)
do = outside diameter (in)
SF = safety factor (in general 1.5 to 10)
The Barlow's estimate is based on ideal conditions at room temperature.
Material Strength
The strength of a material is determined by the tension test, which measure the tension force and the deformation of the test specimen.
•   the stress which gives a permanent deformation of 0.2% is called the yield strength
•   the stress which gives rupture is called the ultimate strength
s=25,000 PSI, t=0.014”, do=0.15625” [5/32”OD], ……SF=2…… or… SF=5

   P= 2^25,000^0.014 /0.15625^2 = 2240 PSI @ 2:1 FOS
P= 2^25,000^0.014 /0.15625^5 = 896 PSI @ 5:1 FOS
   

[xrad]

I think you answered your own question in a way. The 'first' batch likely had contaminates or oxidation which penetrated the outer surface of the brass, or were mixed into the original metal.
 
I have had a few lengths of Chinese insulated fine braided copper wire. the insulation reacted with the copper and the stuff could not be soldered even after cleaning off the 'visual' oxidation.
 
By the way, what kind of wood is on your gas tank? great color!

[derekwarner]

mmmmmmmmmm.....I do tend to agree with a materials contamination issue.....as we have whole families of brasses/bronzes that all can be soldered without any issue

I suspect the timber lagging is from the Lime family.....but the colour is from staining........it is a 50/50 mixture of Oak & Gold Teak..........have used it for all of the lagging in the setup........Derek