Silver soldering.......a newbe to boilers

[Ken Ratcliffe]

Hi All,

I have started on a traction engine using the How to book by George Hughes. Failed at almost the first step though. I cannot get silver solder to run on the boiler end pieces. Having read through many threads on silver soldering and watched youtube vids, I am using a mapp gas torch with a second butane torch for heat. The piece is mounted in fire bricks and I have cleaned all the surfaces using sandpaper, wire wool and a pickle bath. The solder is Medium Silver Solder Strip, 0.70mm X 1.5mm X 600mm with Easy Flo Flux Powder 250g UN3288.

Any help, suggestions or direction to existing threads much welcomed, but I think I have tried everything I have read !

Ken

 

[mfrick]

When Silver Solder is called for the surfaces needs to be clean I would stay away from the steel wool it will leave a residue on the surface and the pickle bath as well. I use emery cloth then carburetor cleaner then flux and your ready to go. Copper will carry the heat off very rapidly so you need a heat source that will put more heat on than the item can carry away.

Mike

 

[tractionengine42]

I've just built a 5" gauge Lion Boiler, don't know if your boiler is a similar size? it sounds very much like your not getting enough heat into the material quick enough. Copper soaks away heat very quickly, preheating the copper away from the joint may help. The flux will go off if heating takes too long, if this happens then melted silver solder will not flow but just form globules.
Avoid using any abrasives to clean the parts as this can leave minute contaminates embeded in the material which could later lead to a leaky joint. I only use files or brass wire brush but mostly just rely on a pickle bath. The flux will clean the joint provided silver solder is applied before the flux goes off, once the flux goes off the joint will oxidise and will have to be dis-assembled, cleaned and re fluxed. I good source of information is Cup Alloys website.
I started by using a large Sievert propane torch which was adequate, I ended up buying an oxy propane torch. For heating large joints I used the propane torch to preheat the surrounding copper and used the oxy propane to apply heat local to the joint. This combination worked well. (This is a bit OTT but I have other uses for the oxy propane torch).
Another point to note, allow the heat in the work to melt the silver solder, melting the silver solder with the torch while the joint is not hot enough only results in globules of solder that don't flow into the joint.
Defiantly silver soldering copper boilers is not easy, a clean joint and getting enough heat in to the joint quickly enough are critical, if it's taking more than a few minutes to get the joint up to temperature then that's probably taking too long. Adding flux to the silver solder as you apply it can help.
That's my experience any way.
I used the same silver solder and flux you mentioned.
Hope that helps
Nigel

 

[goldstar31]

Ken
I'm one of these old geysers with a double distinction in City and guilds Motor Vehicle Restoration with then one for as a Certified welder. I took this all in as mature( manure?) student at the age of 55 after I made my crust in something completely different. At the age of nudging 90, I'm still mentoring- and still auditing though half blind
So my somewhat warped outlook- mind you Dad was blacksmith/farrier, I would put the whole process onto the back burner and do as I did some learning thus saving the spoiling of my good work and my money.
I would light a ring on the top of the gas cooker and heat up a bit of scrap metal that had been cleaned. Incidentally, you were adding oil by using steel wool. Sorry and all that. I would mix up a creamy paste of flux with a wee drop of washing up liquid and before faffing on with a mountain of silver solder nick a piece about half an inch/12mm long. Put the bit to one side with a handy pair of scrap pliers.
So heat up the scrap until the liquid in the flux starts to bubble and eventually it will turn clear and glassy.
Take the bit of solder and drop it in the middle of the glassy flux and wait. Put a bit more dry flux on if you want.
Watch what is happening and your bit of solder should start melting at the edges. Then it should almost all melt and flow onto the scrap. Shut the gas off and make a welcome cup of tea.
Come back when everything is cooled down.

Now do another bit as before, flux, a bit of solder etc on top the gas ring but don't light it. Instead repeat the whole thing but using your torch instead.
If there is no response, you have either not enough heat or the wrong solder or both.
If it does melt, you can practice blowing the melted solder with your torch.
Only move onto your proper work when you are fully satisfied with your capabilities.

Good luck!

 

[clifforddward]

A further description of your symptoms would be helpful to guide a solution. How large is the boiler you are trying to solder...what type of torch are you using?...as others have said copper is an excellent conductor of heat and will pull heat away from a joint very efficiently...isolating the joint by surrounding it with ceramic brick pieces will help keep the heat from leaving the joint area.

Silver soldering is one on those basis model engineering tasks that once learned will become second nature.

If the silver solder melts then beads up and /or won't flow into the joint, then I suspect not enough heat and/or cleanliness of joints.

I suggest you try some experimental silver soldering using smaller scrap pieces of copper...that will allow you to practice applying heat; getting the silver solder to melt and flow based on heat from the copper material rather than directly applied heat.

In reality, once mastered silver soldering is like magic...once copper is hot enough and flux has done it's thing clarifying the metal surface, the silver solder quickly wicks into the joint...that is the technique you want to master on the practice pieces.

Expect to make many mistakes along the way...I know I certainly have.

 

[Ken Ratcliffe]

Hi All,
I worked though suggestions and ideas, changed the solder and flux types, used different cleaning methods, but in the end I think it was "simply" heat. Not enough insulation and not enough heat in. I bought a Sievert Pro and a bottle of propane. I use that with a bit of more directed heat where needed with a MAPP gas torch and bought a insulation blanket to to with insulation blocks. Low and behold, solder runs and quickly disappears into joints - as Cliff says - like magic ! After it cooled there was a good seal for most of the joint, but not perfect. I was pretty happy to get such a good result though. I have a bit of patching to do, then I will hopefully get better on the back end of the boiler. Still waiting for the equipment to arrive (I live in deepest darkest rural Wales) gave me time to get on with other parts of the build.

 

[goldstar31]

err Uhm????? Patching changes the melting point of your solder.

 

[Ken Ratcliffe]

yeah......I can see from looking around other posts that my blasé comment about patching could be naïve !

 

[clifforddward]

Yep, takes more heat to remelt a joint second time around...down the road you'll be able to use that to your advantage when adding new parts near already silver soldered joints.

My advice is to remember to apply flux to all surrounding joints that will see the heat...not sure if I fully understand the science behind it, but refluxing surrounding areas has always allowed me to re-heat and re-seal a joint more successfully.

As you do more silver soldering you'll develop techniques including using gravity to your advantage...arranging joints to be soldered so that solder flows downhill into the joint.

Also remember to leave a tiny bit of space in the joint for solder to flow...one common mistake is to make the mechanical joint to be soldered so tight that there is no room for the solder to flow. A trick I use on close mating surfaces is to give the joining surfaces a "pop" from an automatic center punch to slightly raise the surface around the center pop...provides the .001"-.002" of space for solder flow.

Here again, practice makes perfect. I'd fully recommend taking your scrap copper pieces from making the boiler, make up practice joints, and develop your skill there before tackling the actual project.

 

[goldstar31]

Yep, takes more heat to remelt a joint second time around...down the road you'll be able to use that to your advantage when adding new parts near already silver soldered joints.

My advice is to remember to apply flux to all surrounding joints that will see the heat...not sure if I fully understand the science behind it, but refluxing surrounding areas has always allowed me to re-heat and re-seal a joint more successfully.

.

As we know the solder is an alloy of silver but on making the first joint, part of the silver alloys with the parent- in this case copper. Of course, the silver has the lowest melting point- and you lose some of it which creates a higher melting point alloy. To get the old joint to melt again, you obviously need more heat. Some people will use a higher silver content to get the required flow.

i hope that this clears the question.

Norman

 

[coulsea]

As most people have said cleaning and the correct amount of heat are the key. when it comes to cleaning some things can do the unexpected. I was doing some nickel plating and was using some sandpaper from the cheap shop, even after using soap and solvent it would not work. the sandpaper had some sort of glue or something that I could not get rid of.

 

[Ken Ratcliffe]

Yep, takes more heat to remelt a joint second time around...down the road you'll be able to use that to your advantage when adding new parts near already silver soldered joints.

My advice is to remember to apply flux to all surrounding joints that will see the heat...not sure if I fully understand the science behind it, but refluxing surrounding areas has always allowed me to re-heat and re-seal a joint more successfully.

As you do more silver soldering you'll develop techniques including using gravity to your advantage...arranging joints to be soldered so that solder flows downhill into the joint.

Also remember to leave a tiny bit of space in the joint for solder to flow...one common mistake is to make the mechanical joint to be soldered so tight that there is no room for the solder to flow. A trick I use on close mating surfaces is to give the joining surfaces a "pop" from an automatic center punch to slightly raise the surface around the center pop...provides the .001"-.002" of space for solder flow.

Here again, practice makes perfect. I'd fully recommend taking your scrap copper pieces from making the boiler, make up practice joints, and develop your skill there before tackling the actual project.

I like the tip on the punch - will use that one ! On the last recommendation...….I wish I had the organisation / discipline - I have this awful tendency to jump straight on and try the most complex process first - and then wonder why it doesn't work !

 

[kwoodhands]

Hi All,

I have started on a traction engine using the How to book by George Hughes. Failed at almost the first step though. I cannot get silver solder to run on the boiler end pieces. Having read through many threads on silver soldering and watched youtube vids, I am using a mapp gas torch with a second butane torch for heat. The piece is mounted in fire bricks and I have cleaned all the surfaces using sandpaper, wire wool and a pickle bath. The solder is Medium Silver Solder Strip, 0.70mm X 1.5mm X 600mm with Easy Flo Flux Powder 250g UN3288.

Any help, suggestions or direction to existing threads much welcomed, but I think I have tried everything I have read !

Ken

Ken, fire brick absorbs the heat, insulating brick reflects heat. I bought 6 insulating brick online , also called refractory bricks. They are white in color, very light weight and break easily. I also bought refractory cement.
Mainly to cement broken bricks. You need a propane torch that puts out a lot of heat and a propane bottle used for barbecues. You buy the initial bottle and when empty take it back for a refilled bottle.
As far as information you have received so far , it is spot on.
I have done a bit of hard soldering myself, but I have to say I failed with a boiler. Make sure the gap is not too large or too tight. I believe some of the failure I had was the seam was too tight. You need about .0003 gap.
I tried a second time, almost got it. Got tired of chasing leaks and decided that my locomotive will only run on air.
I hope you do better than me. By the way I bought a Victor Torch on Amazon that really works well.

mike

 

[goldstar31]

Mike,

I think your decimal point is in the wrong place! As for leaks, two thoughts come to mind. the first is to use silver solder paste as a preparatory 'tinning' before actually sealing the joint. 'Tinning' does help and if you are brave and careful enough, removal of the dross can be achieved with a wiping cloth on. Your initial offering should leave everything bright and shiny in preparation for adding to equally important ring of solder. OK, I would use a long stick dabbed iin flux with a bend it to avoid poking my eye out but a ring of solder held by molten clear flux is the beginner's way. You need a steady circular motion rather - dabbing it here, dabbing it there approach. the heat around a tube or stay must be EVEN.

Ken should read the foregoing too!

My dear old father who could barely read and write would tackle a full size locomotive boiler and 'raise the dottle' from out of the weld. This is an old Northumbrian or Tyneside expression about the filthy residue left in a smoker's tobacco pipe and a weld if not scrupulously prepared will have the leaking mentioned caused by dirty inclusions. I'm not going to give a lecture on how to do it suffice to say that this isn't a dirty oily corroded lot of old steel piping and so on.

After all, EVERYTHING should come out clinically clean of a pickle bath ideally of dilute sulphuric acid.

 

[packrat]

After silver soldering in the HVACR industry for years I would say you need more heat, We always used a oxy-acetylene torch
never Mapp gas only on soft soldering small copper water pipes also used air-acetylene torch with soft solder.
If you could get your hands on what we called a turbo torch that used acetylene and forced air it could get hot enough for smaller silver solder jobs..

 

[Natbr]

If I can jump in here too ... I have been silver soldering small fittings for my model steam engine/boiler projects. In the end, I found that you really have to get the parts up light glowing red for the solder to "flow" into the joint. After soldering up small pieces, "nipples" (or pipe ferrules) for pipe unions, I started silver solding something larger -- the brass rudder to its steering shaft and then ornamental brass supports to the outside of the rudder. My issue was that every time I got the rudder up to temperature to silver solder a new item on, the solder on virtually every previously soldered piece, ran and the whole thing came apart. :-(

I struggled with it and eventually used pipe solder for the ornamental pieces (much lower temp needed). This experience convinced me NOT to try to silver solder up my own boiler. I ended up buying one from Pendle Steam Boilers (http://www.pendlesteamboilers.com/) .. Pricy but I have been marveling at their silver solder work .. don't know how they add internal cross tubes, boiler ends, fittings (bushings, etc) ... without everything running... any ideas?

 

[John Antliff]

Personally I have not had as good an experience with the new Cadmium free silver solder on sale these days, preferring to use old Easiflo 2 solder. I managed to obtain some Cadmium SS from the states and decided to make a vertical 6 inch boiler as my first serious SS project. The full build can be seen in - https://youtu.be/a7nZ0zwbGEs

I had to build an insulated cave out of Kawool ........

and I used a Sievert gas torch of about 40 KW. Note the rings of silver solder on the two flange plates. I do not advocate applying the solder manually as you apply heat, much preferring placing a calculated amount of SS on the joint with flux and heating the joint from below and never allowing the flame to heat the solder directly.

Another tip is to use Citric acid as your pickling medium - it's cheap and far less dangerous then H2SO4 (Sulphuric acid i.e. battery acid) and it works just as well if not better! Cleanliness is definitely the key to good results, even sweat from fingers can contaminate a surface. Pickle before you assemble with flux and solder it quickly soon after.

The work needs to be able to remain assembled as you heat it and may need special fixtures to ensure correct positioning during the heating. The above picture shows 84 tubes inserted into 2 flange plates, the tubes were shouldered at each end to ensure that they did not slip through the holes during the soldering process. That is far more time was spent ensuring that the assembly would stay together than was spent doing the brazing.


Practice makes perfection!

 

[bluejets]

Personally I have not had as good an experience with the new Cadmium free silver solder on sale these days, preferring to use old Easiflo 2 solder. I managed to obtain some Cadmium SS from the states and decided to make a vertical 6 inch boiler as my first serious SS project.

Available in Aus, might be a bit more convenient.

https://www.sbagroup.com.au/amal/sba-products/silver-solder-rods-wires-rings/

 

[ALEX1952]

With regards to soldering boilers I believe you can get silver solder with different melting temperatures or you used to be able to a few years ago, start at the highest temp and work down, still a lot of skill to get the subsequent temps just right, never tried it myself so best of luck.

 

[goldstar31]

[

With regards to soldering boilers I believe you can get silver solder with different melting temperatures or you used to be able to a few years ago, start at the highest temp and work down, still a lot of skill to get the subsequent temps just right, never tried it myself so best of luck.

YES, one can.

So a little story? Yes, I was in Welsh Wales/ My favourite silver solderer( whom I married) was playing music in Llandudno and I got an invite to go into what were the roman copper mines on the Great Orme. I come from a mining family where accidents down under were prevalent but the odds were that there would be no big bangs, roof collapses and such ordinary affairs. The copper ore was worked out to stop at sea level and so on.
I got curious- my wife taught me casting- well, gold, she was a dentist. So realising that thee was no coal or trees, I raised the question with a very informed guide. He said all the smelting was done with nothing more than brushwood and a good Atlantic breeze!

It made me think! My late wife used to mouth blow on a little alcohol burner and happily silver solder orthodontic appliances. It made me think a bit more. She also gave me a lecture one night on centrifugal casting- of old gold fillings-- but I digress

Norman