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caddy
07-15-2008, 12:25 AM
Hi
I am perplexed about a silversoldering issue I have encountered.
I was making a fuel tank from 4" dia. copper tube 1/8th wall about three inchs high. I found that in order to get the solder to flow (easy flo 45)
I had to use a moderate size tip (O/A) to get enough heat to flow. I was under the impression that propane was likely the best heat source for this but I had to use what I had. Suggestions?

sidegrinder
07-15-2008, 12:37 AM
Copper is such a great conductor that it pulls the localized heat away pretty fast--so you probably had to get the whole piece pretty warm. While not huge, that size pipe would probably be a chore to silver solder with any of the smaller propane and oxygen setups. I have one of the mini ones and it has its place. I prefer the oxy-actylene in most instances though.

tattoomike68
07-15-2008, 12:44 AM
I was reading in another thread just today about the CO2 is low in a propane flame and does not sheild the weld like AC.

I have only gas welded with acetylene so when other chime in I will learn a few things too..

I have welded hydraulics with brass but never silver solder, it seems to me I remember being told silver solder likes about 1,850F and propane just kick out about 1,600F its just too cold. Please correct me if I am wrong...

lazlo
07-15-2008, 12:54 AM
it seems to me I remember being told silver solder likes about 1,850F and propane just kick out about 1,600F its just too cold.

Silver brazing is usually done around 1145 F, well within the heat envelope of oxy/propane.

Evan
07-15-2008, 12:55 AM
The correct way to silver solder a large piece of copper like that (or silver!) is to flux the area to be joined and then, using the flux as glue, stick small pieces of solder ribbon in the area sufficient to flow out when it melts. The entire piece must be heated. Easyflo comes in several different grades, each with a different melting temperature. If you have several different parts to solder on the same piece you start with the highest temperature grade first. The next soldering operation is done with a lower temperature grade and care is taken to just heat the piece enough to melt it without melting the previous joins. This can be repeated if you have a selection of solder grades.

I highly recommend buying silver solder in ribbon form as it is much more versatile than sticks.

dp
07-15-2008, 12:59 AM
http://www.homemodelenginemachinist.com/
Nice website, Mike - somehow missed it all this time.

tattoomike68
07-15-2008, 01:23 AM
Nice website, Mike - somehow missed it all this time.

I am the tech admin of that site, I dont have the skills to even think of building engines as fine as they do but am proud to make the site a fine place.

I can write code for web servers but someday as an old man I will build some more engines, I just hope I live long enough.

Since I hurt my back and my heath went downhill I started working on web sites and I spend less time in the shop.

You are all very welcome to join http://www.homemodelenginemachinist.com/ and watch videos and download plans and enjoy for free, its a place where we have fun and are easy going.

thanks for noticing its nice, We worked hard setting it up.

:)

Astronowanabe
07-15-2008, 01:26 AM
In a former life I built bicycles (or human powered vehicles at any rate)
always brazed with Mapp gas (basicly propane++) / O2
and used a borax flux paste.
seemed to always work well

Smokedaddy
07-15-2008, 01:27 AM
My turn,

You mentioned Easy-Flo (not Sil-FOS). It's 45% Si, 15% Cu, 16%Zn and 24% Ca (note the zinc and cadmium ... good ventilation needed). There is a very fine line between its melting point (Solidus 1125 F) and when it flows (Liquidus 1145 F). Your flux must be fresh and clean. We only use Borax made into a paste with distilled water, which of course you can buy (don't use tap water to thin the Borax). The copper must be super clean. Heating is critical. The flux is your friend, acting like a temp-stick. When you start to apply the heat, the flux will dry out (moisture i.e.) boils off (212 ish). The flux will then turn a milky white in color and start to bubble at about 600 degrees. Eventually it will turn into a clear liquid at about 1100 degrees, which is just short of the brazing tempeature. Keep in mind its melting tempeature and when it flows, about 1140 F. A large tip is best as it allows for a shorter brazing time and reduces the time for oxides to form. On larger bore copper tube (6" and 8") we use a double headed tourch and or a large rose bud, sometimes 2 of them.

-SD:

tattoomike68
07-15-2008, 01:39 AM
In a former life I built bicycles (or human powered vehicles at any rate)
always brazed with Mapp gas (basicly propane++) / O2
and used a borax flux paste.
seemed to always work well

thats cool I have a few old bikes and would love to make a bicycle built for 3. :) 2 is too easy...

Evan
07-15-2008, 01:44 AM
Not so fast. Easyflo 45 is just one of the series that may be used.

Filler Metal name: Easy-Flo 45
Typical Applications: Joining ferrous, nonferrous and dissimilar metals and alloys with close joint clearances.
Solidus: 1125'F/605'C
Liquidus: 1145'F/620'C
Max. Recom. Brazing Temp. 'F: 1350
Nominal Composition,%: 45Ag 15Cu 16Zn 24Cd
Joint Color as Brazed: Light Yellow

Filler Metal name: Easy-Flo 35
Typical Applications: Similar to Easy-Flo 45, but used where joint clearances are large and fillets are desired.
Solidus: 1125'F/605'C
Liquidus: 1295'F/700'C
Max. Recom. Brazing Temp. 'F: 1400
Nominal Composition,%: 35Ag 26Cu 21Zn 18Cd
Joint Color as Brazed: Light Yellow

Filler Metal name: Easy-Flo 30
Typical Applications: Similar to Easy-Flo 35, but used for more economical joints.
Solidus: 1125'F/605'C
Liquidus: 1310'F/710'C
Max. Recom. Brazing Temp. 'F: 1400
Nominal Composition,%: 30Ag 27Cu 23Zn 20Cd
Joint Color as Brazed: Light Yellow

Filler Metal name: Easy-Flo 25
Typical Applications: Similar to Easy-Flo 30, but used for most economical joints.
Solidus: 1125'F/605'C
Liquidus: 1375'F/745'C
Max. Recom. Brazing Temp. 'F: 1400
Nominal Composition,%: 25Ag 35Cu 26.5Zn 13.5 Cd
Joint Color as Brazed: Light Yellow


Note the differences in liquidus temperatures. It is a stepped series intended to be used in the manner I described. There is a lot more to silver soldering than just melting a bit by putting a flame to it. It is possible to do some very intricate soldering by taking advantage of the properties of the available filler metals.



There is a very fine line between its melting point (1225 F) and when it flows (1145 F).

1225 isn't the melting point. The liquidus of Easyflo 45 is 1145 and the solidus is 1125. Because Easyflo 45 is not a eutectic it does not melt or solidify all at once. The two temperatures give the range between which the solder is neither entirely solid or liquid. At the solidus all components have solidified. At the liquidus all components have melted. With a eutectic mixture all alloy components melt and solidify at the same time and temperature.

Smokedaddy
07-15-2008, 02:09 AM
Hi Evan,

Oops, a typo on my end, meant 1125. I suppose I should start reading my own posting before saving. <duh> I teach welding and brazing too. <red-faced> I realize additional series exist, he was specifying the 45 series.

Regards,
-SD:

Mike Hunter
07-15-2008, 09:35 AM
Since its for a fuel tank, fairly low pressure, why not use soft "plumbing" solder. Most melt and flow at 500 deg or less, easy to work with, flows nicely, easy to clean up, and designed for joints that hold liquid.

Mike

Mcgyver
07-15-2008, 09:59 AM
caddy, we can't use heat and temp interchangeably....propane and air give plenty high enough temps to silver solder, I do it all the time, but for a big job it doesn't provide enough heat (energy) in enough time. if you had 5 guys going at it with large propane torches no problem...or use O/A that puts out a whole bunch more heat a lot quicker. An A/O flame is too high temp for silver solder, it can burn the flux, so when using A/O its best to apply the flame indirectly

lazlo
07-15-2008, 10:19 AM
McGyver, post some more silver brazing pictures -- some of the brazing jobs you've posted are amazing.

Mcgyver
07-15-2008, 11:27 AM
lazlo, way to PUMP ME UP. geez for that i'm going to head out to the garage and start brazing up all kinds of crap ...... honest, I haven't done that much of it, but i only show you the good ones :D

Fasttrack
07-15-2008, 05:03 PM
Propane and oxygen torches put out more btu per hour than O/A ... How can O/A put out "more heat faster" than propane?

Maybe its just an issue of tip size and type. They offer tips for propane/oxygen setups that provide up to a million btu/hr. I've only seen 300,000 btu/hr for acetylene.

I'm a little faint on correct torch terms, but the "spreader" tip (designed for heating) does a dern good job heating up a large casting fast. Probably too hot for copper, but it worked great on big hunks of iron. The O/A torch at shool doesn't work near as well.

I've brazed the studs on an exhaust manifold once using O/A and once using a propane torch and the propane torch was alot faster. It got the whole end of the casting nice and hot so I just had to lick the stud with the flame for a bit before applying my brazing rod. With the O/A torch, I had to heat each area for a while before appyling the rod. Of course, the entire casting stayed much cooler with the O/A setup then the propane. I guess if I was just doing one stud, O/A would be faster but for all three studs, it worked better to spend a few minutes heating the entire end of the casting and then brazing the studs in place.

Let me be the first to admit that I'm a novice when it comes to brazing and silver solder, though. I stand to be corrected.

loose nut
07-15-2008, 08:45 PM
Ox/acet puts out a higher flame temp but it is highly concentrated and the copper will suck the heat away from were it is applied, propane puts out lower temp but is more diffuse so it will heat up a larger area to a more even heat.

The biggest problem for either is that you are loosing the heat you put into the copper faster than it can be replaced. The part that isn't being soldered should be packed it some kind of insulating material like sand or ash, fiberglass mat will work to but will melt were the flame impinges on it (not a real problem it will chip off when cool).

For large work like a 7 1/2 " scale loco boiler you can even use a oxy/acet set with a rosebud (#100 Heating tip) as long as you keep it in motion so you don't burn the copper. For smaller work like your tank propane is best unless you are proficient with the oxy/acet but a propane hand torch isn't good enough, usually, unless the job is fairly small. When you need more BTU's you need a torch like those made by Sievert (and others), these have different sized tips and can really pump out the heat but can be tailored to suit the job at hand.

http://www.shesto.co.uk/Soldering_&_Brazing_Equipment_&_Supplies-Sievert_LPG_Gas_Torches_&_Burners/c50_52/index.html

You probably aren't going to run out and buy a new torch so try insulating the job and get a buddy with a second torch to help out. See if it will work.

Mike Hunter is right, why not soft solder it, thats what I would do. Save the expensive silver for the jobs were it is necessay, if you have a leak it is easier to fix soft solder than silver (use the higher melting soft solder first and repair with a lower melting solder).

You haven't mentioned what type of joint that you are using, that is very important to the job too.

oldtiffie
07-15-2008, 09:01 PM
Its done a lot by Licenced Plumbers here in OZ. I've seen any amount of 3" plus diameter copper tube welded in all sorts of conditions for water, natural gas and LPG.

The compositions of the copper and silver-solder is prescribed in each case.

I'd be inclined to ask your local Plumber or visit a Plumbing web site.

I get my brasing, bronzing and silver-soldering rods and fluxes from my local welding and steel supplier. He has racks of the stuff with a quite comprehensive guide.

You can't beat professional advice from those whose living and livelihoods depend on getting right just about every day of the week. I'm sure that many would regard being asked as a compliment and would be only too glad to advise you.

Oxy/acet and LPG seem to be the methods of choice as regards heating.

Evan
07-15-2008, 09:14 PM
I wouldn't use soft solder, it doesn't hold up to vibration. Better and just as easy is to use silver bearing solder. It is usually lead free and has about 2% silver and the rest tin. It is much stronger than soft solder and has a reasonably low melting temperature, low enough that a good hot 80 or 100 watt iron can be used. For insulation vermiculite works the best. It's made of expanded mica flakes and is an excellent insulator. You can fill a bucket with it and bed the part in the vermiculite to solder. It can also be mixed with water and bentonite clay (wine making supplies) to make a loose paste that may be applied to keep portions of the work cool while heat is applied elsewhere.

caddy
07-15-2008, 11:10 PM
Hi guys.
I wrote a masterpiece reply and for reasons unknown, it went into the cyberfog.
So, I havent the horsepower to do it again.
My thanks to all that responded.
Caddy

oldtiffie
07-16-2008, 12:42 AM
Some of the best "efforts and results" I've seen with copper pressure vessels are the construction and testing of model locomotive boilers. I was all done with copper and (as I recall) silver solder. Some of them were very intricate and sizable. All had to be pressure-tested (relief and safety valves too) by a Certificated club-member.

Many of the makers of those boilers were not from a skilled back-ground - but many of the club members were. They developed those skills and the "look" of the results was superb.

I'd suggest looking at model engineering sites for advice.

I am sure there is plenty here as well.

From my point of view, I don't want or need to know the composition or analysis of "stuff" as regards materials and consumables etc. I'd just need some competent experienced advise to point me in the right direction as regards material (copper), consumables, (rods and flux), methods of heating (ox-/acet, LPG, gas-bottle sizes, tip sizes etc. and if possible to give me advice and hopefully a demonstration "face-to-face" either in person or on a web page.

Scishopguy
07-16-2008, 02:45 PM
My turn,

You mentioned Easy-Flo (not Sil-FOS). It's 45% Si, 15% Cu, 16%Zn and 24% Ca (note the zinc and cadmium ... good ventilation needed). There is a very fine line between its melting point (Solidus 1125 F) and when it flows (Liquidus 1145 F). Your flux must be fresh and clean. We only use Borax made into a paste with distilled water, which of course you can buy (don't use tap water to thin the Borax). The copper must be super clean. Heating is critical. The flux is your friend, acting like a temp-stick. When you start to apply the heat, the flux will dry out (moisture i.e.) boils off (212 ish). The flux will then turn a milky white in color and start to bubble at about 600 degrees. Eventually it will turn into a clear liquid at about 1100 degrees, which is just short of the brazing tempeature. Keep in mind its melting tempeature and when it flows, about 1140 F. A large tip is best as it allows for a shorter brazing time and reduces the time for oxides to form. On larger bore copper tube (6" and 8") we use a double headed tourch and or a large rose bud, sometimes 2 of them.

-SD:

Smokedaddy...this is the best explanation yet of what to look for when silver soldering. I did quite a bit of it in the science labs, making manifolds and fittings, and was always told that you had to hold your mouth right when doing it. I quickly learned about watching the flux but the amount of heat took a little longer. I quickly learned that once you have overheated it the solder will just bead up and fall off. I had the best luck with Aircosil brazing flux. Everywhere you apply the flux, the solder will go.

topct
07-16-2008, 04:54 PM
Anyone use something like this, (just an example). There are simpler ways of doing the same thing.

http://www.gasflux.com/