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Advantages of silver solder over tin/antimony?

Posted by pjb999 (My Page) on
Sun, Oct 21, 07 at 14:34

Just wondering if I really should be using the silver, I'm using mps/mapp (yellow can) gas and started this particular job with a small roll of silver solder, and ended up using tin/antimony, I hadn't even noticed beyond the 'lead free' notation, I haven't mixed the two at any single joint and after a struggle to get the last (wet of course) joint done despite copious amounts of bread, it all seems good now, yes rather drippy and it's tempting to use Yorkshire (pre-soldered) fittings in some places - it might make sense in some tight areas, I have some pretty charred drywall and framing in parts now- but as I understand the silver stuff is better for lower temp torches but since i went with mapp I guess it's not an issue?


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RE: Advantages of silver solder over tin/antimony?

Quote: "but as I understand the silver stuff is better for lower temp torches but since i went with mapp I guess it's not an issue?"

While that may be your understanding, I hate to be the one to inform you but it is totally wrong, but then, dont be disheartened because; most homeowners and neophyte handyman plumbers share it.

The American Society of Welding defines "Soldering as the act of joining two metals by means of a filler metal with a melting temperature under 840degF. In fact the alloys used for plumbing purposes rarely exceed 600degF.

Ordinary 50/50 tin/lead solder (ASTM alloy SN50) has a melting temperature of 361 to 421degF, which can easily be applied with a common pencil flame type propane torch.

In the early 1980s the American Society of Testing and Materials amended ASTM standard B-61-"Standards for Safe Potable Water" to require that we use lead free solder or solder which contains not more than 0.20% lead.

We then adopted the use of ASTM alloy SB-5, which is a 95/5 mix of Tin and Antimony. This is the alloy, which is still most commonly in use.

It is true that with a melting temperature range of 452-464degF the new Alloy SB-5 (95/5 tin/antimony) solder proved to be a bit more difficult to handle than its predecessor, Alloy SN-50 (50/50 tin/lead) solder with a temperature range of 361 to 421, especially when working with the older style pencil flame propane torches

In commercial plumbing there are conditions which require a solder with a higher tensile than what is provided by Alloy SB-5(95-5 Tin-Antimony) solder so they have now developed ASTM Alloy E (95/5 Tin/copper) with a melting temperature of 440-500degF and ASTM Alloy HB (Tin/Antimony/Silver/Copper & Nickel) with a melting temperature of 460-630degF.

To compensate the propane torch manufacturers developed torches that have the combustion air intake directly on top of the regulator and there is a spiral wire inside the tube from the air intake to the torch tip, which causes the fuel/air mixture to swirl as it travels up to the tip. This pre-combustion swirling action effectively increased the output temperature of the flame well within the requirements for the new alloys.

The plumbing codes were again amended to prohibit the use of soldered joints on copper lines run under a slab. When running copper under a slab we are required to use wrought copper fittings and all joints must be brazed.

Per the American Welding Society "Brazing" is the act of joining two metals with a liquid fill metal with a melting range between 1200 and 1550degF. In order to meet this standard the propane torch manufacturers then began producing dual fuel torches that could use "Propane" as the primary fuel for soldering and "Mapp" for brazing.

Most of the problems that are commonly encountered by the novice when soldering are a direct result of too much heat. While the solders that they are using have melting temperatures ranging from 452 to 630degF they are using torches, which can effectively heat the pipe in excess of 1500deg.

Flux bubbles at 600 to 800degF which is well above the proper soldering temperature and at 800deg the flux itself burns off, leaving a gummy residue that makes it nearly impossible to get solder to flow.

To answer your original question, there is absolutely no advantage to using silver bearing solders in residential plumbing and due to the increase temperature range it would make soldering even more difficult. Your best bet is to stay with Allow SB-5 (95/5 Tin/Antimony) solder and Propane fuel until you are completely comfortable with it.


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RE: Advantages of silver solder over tin/antimony?

Thanks for your informative post - I had gotten the higher melting point impression of silver solder from literature I'd read, but I guess they were comparing it to traditional lead- bearing solder rather than tin/antimony. Here in Canada the silver stuff sits alongside the tin/antimony stuff and there's a difference of around three dollars for a medium-sized roll, from what you say the silver stuff may make a stronger joint? I'm all in favour of that.

As for getting comfortable with Mapp/mps I'm a lot more comfortable with it than when I started, you're right, it's certainly possible to quickly overheat the joint but I'm not a complete novice with soldering -albeit a different sort, I've done a lot of electronics soldering and some manufacturing so I'm fairly handy with that sort. Prior to this job I'd probably only soldered half a dozen copper pipe joints and assisted my dad with a few, by the end of the work it was looking a lot better (somebody said something in favour of wiping and I suspect they're right)

Brazing might be fun, I believe it when they say you don't strictly need the oxy bottle if you're doing small work, I'd just have to find something to do....I must admit the mini-oxy/mapp kits look pretty cool at well under a hundred dollars....

If I did go to propane, I wonder if the torch I got with the mapp/mps bottle would work, it has the swirly pattern inside you described, it certainly does throw a beautiful flame.


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RE: Advantages of silver solder over tin/antimony?

Oatey has a set of patents on Tin/Copper/Silver bearing solders for lower temperature use.
The silver content is just a few percent.
Most melt right around 428F/220C putting them a little closer to Sn-Pb alloys.
They also flow better and leave a better surface finish than 95-5 Tin-Antimony alloy.

Smaller torches have always had some problems with 'T' joints and larger pipe sizes.
Trying to bring a 3/4 x 3/4 x 3/4 Tee up to temp has been difficult for smaller propane torches.
The flux tends to get pretty cooked by the time you get to the last joint.
Larger and/or hotter torches solve the problem.
Really large soldered or brazed joints start requiring multi-head torches running oxy-acetylene.
Since I already have acetylene tanks for welding and brazing, I just use an air-acetylene torch for most soldering work also.
The lack of any position concern (inverting small tanks is a problem) and small size of the torch head connected to the tank by a 12 foot hose works very well for working overhead or in tight spaces.


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RE: Advantages of silver solder over tin/antimony?

When they say the inclusion of silver in the alloy produces a stronger joint that is a relative term. In truth the advantage only begins to appear when working with copper pipe in excess of 2" diameter and I doubt that many homeowners will ever have opportunity to work with 2" or greater copper pressure piping.

For all intents and purposes ASTM alloy SB-5 (95/5 Tin, Antimony) will far exceed the strength requirements for any soldered joints found in a residential structure.

The safe working pressure of a pipe or joining material is generally considered to be approximately 50% of its "Maximum Bursting Pressure". In turn, the safe working pressure generally decreases as the diameter of the pipe increases.

Keep in mind that the maximum allowable static head pressure for a potable water distribution system is 85psi whereas the safe working pressure for " type L hard drawn copper pipe with a working temperature of 100degF to 250degF is 1242psi.

For the same " Type L hard drawn copper pipe the standard 50/50 Tin/Lead solder (ASTM SN-5) produced joints with a maximum safe working pressure of 200psi whereas the Lead Free 95/5 Tin/Antimony solder (ASTM SB-5) produces joints with a maximum working pressure of 1090psi. As you can see, the 95/5 will produce joints far in excess of any conditions, which might be found in the residential potable water system. On the other hand, if the hard drawn copper pipe is heated in excess of 850degF during the soldering process it will anneal the pipe and once the copper pipe is annealed the safe working pressure is reduced to approximately 50% of its rating. This means the safe working pressure would then be reduced to approximately 500psi, still well above any condition which might be found in the home, but annealing the pipe introduces a number of other problems and it is a prime consideration when selecting the type of torch one uses to make the solder joints. This goes back to what I said in my first post, most of the problems that are encountered by the novice when soldering copper pipe are a direct result of too much heat.

Here is a real challenge to test your soldering skills. According to the estimators table in the Copper Pipe handbook it requires 0.261lbs of solder per 100 joints on " copper pipe, and allowing an average of 100% loss for drips you should still be able to complete 100 joints with 0.595lbs of solder. On average a skilled plumber should be able to complete all the joints in a 3BR with 2.5baths, kitchen & laundry with 1lb of solder.

In regards to the small Oxy/Mapp or Oxy/Propane welding torches seen in the hardware stores for under $100. In my humble opinion-save your money. When they first came out I thought it would be handy to have a brazing torch that would fit inside my HVAC toolbox so I bought one. It didnt take me long to realize that it was no bargain. First off, the lines are only 6 long, which makes it nearly impossible to braze a line near the ceiling. Second, the Oxygen cylinders are $8 each and they only produce about 20 to 35 minutes actual burn time.

If you really want an oxy torch for welding and brazing I would suggest you consider the portable units made for HVAC techs by Victor, Harris or Tote-Weld. They offer an MC tank for acetylene and an R tank for Oxygen, both of which fit nicely into a portable carrier with a common Oxy-acetylene torch regulators, 12 lines and a torch handle with interchangeable welding tips and a cutting tip for about $300. With this type of torch you initially purchase the gas cylinders but when they are empty you can take them to a welding supply or an HVAC supply and exchange them for full tanks generally for much less than the cost of the MAPP or Oxy cylinders in the hardware stores. Depending upon the size of tip you are running, these torches will provide approximately 20 hours of welding or brazing time or 30 minutes of cutting iron for each oxy cylinder and you will typically use two oxy cylinders for each Acetylene cylinder.

Back in the mid 80s when we first switched to 95/5 lead free solder "Turbo-Torch" developed a torch with the regulator attached to the propane cylinder and the air intake at the base of the tube with the swirl mix pre-combustion technique. Those torches required that the propane cylinder must remain upright so the Turbo-torch had a rotating arm to allow directing the flame horizontally or even downward when necessary. Those were very good torches and they are still available today. In addition, Turbo-torch came out with torches that had multiple reach arms and burners. I recently looked at their catalog and they still show a dual burner torch but they have now discontinued the triple burner. The dual and triple burners are excellent when working with larger diameter copper such as 2" or 3" where you need a broader flame area to insure even heating.

About the same time that Turbo-Torch brought out their line of premix torches Bernz-o-matic introduced the TS-4000 trigger start all position torch with the swirl pre-mix technology. Later when MAPP gas came on the scene the TS-4000s were commonly packaged with both propane and MAPP cylinders. They are now commonly packaged as an individual torch head or with a MAPP cylinder but they still remain a dual fuel torch, and my personal preference for propane soldering. While many people may be put off by the $29 price tag on the torch head or $35 for the torch with fuel, I would like to point out that the original TS-4000 that I bought back in 1985 is still going strong. I have had to change the igniter once but most good hardware stores stock the repair parts for these torches so that was not a problem.


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RE: Advantages of silver solder over tin/antimony?

Pup-

Interesting comments. You forgot to mention smell. MAPP gas stinks!


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RE: Advantages of silver solder over tin/antimony?

What I find most fascinating is the insistence that MAPP is so much hotter. NOT TRUE..

When MAPP is burned with Oxygen it produces a flame temperature of 5301degF whereas when Propane is burned with Oxygen it only produces a flame temperature of 4579degF for a difference of 722degF

However when we consider Propane versus MAPP in the typical hand torch it is true that MAPP is hotter but I fail to see eough difference to make any real advantage with MAPP.

MAPP & AIR produce a flame at 3650degF while Propane and Air only produces a humble little 3596degF for a difference of 55degF.

is 55degF really worth tripling your fuel cost?


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RE: Advantages of silver solder over tin/antimony?

I'm no silver soldering expert, although i did find some good silver soldering directions recently and gave it a shot. Well, i succeeded in not burning myself so that was good :) Brazing is definitely not easy when you're getting started.


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