Sif-Bronze is best for Steel. But you can check if OK for the boiler to join copper, there's plenty of on-line advice about this. That's where I would need to look.
The REGULATIONS are for designs of boilers using SILVER SOLDERED copper . I know Sif-Bronze has some capillary action, but the silver solder is designed for the capillary action of filling a couple of thou gap between the 2 copper surfaces. That's where it gets its strength, not from fillets of solder.
I think the top reason for using silver solder on copper boilers, is the temperature of melt of the solder. SifBronze melts very close to the melting point of copper, although I have used it, but not on boiler work. I have also looked on the web at copper MIG brazing (uses SifBronze wire) or Copper welding (TIG). There is so little information about SifBronze brazing of copper that maybe it is just more risky from the higher temperature required to fuse to the copper?
I use silver solder 55% silver, as this is really easy to use. But if silver soldering in stages, where you need one stage to remain solid while the next stage is made, then you need to ring changes in the silver solder to give you a good range of assembly temperatures. Start High temp., on small sub-assemblies, and lower the melting point of solder at each stage. Needs some homework, research and planning.
Unlike welding, you have to heat a huge amount of the job while silver soldering, so it takes a BIG blowtorch and LOTS OF BRICK INSULATION, so you can get the joints hot (e.g. on shell ends). I bury 3/4 of my boilers in a bucket of sand for insulation, so only the end being worked on is exposed. But the sand must be DRY.
Using the highest melt-point silver solder on bushes, internal reinforcements, etc. is a good idea. Then the sub-assemblies can be assembled together for soldering with a lower melt silver solder. - I mentioned to someone that my boilers were worth more in "silver" than scrap copper! But a good boiler can last more than a lifetime!
PICKLE well between stages, and apply a paste of the flux powder (a drop of washing-up liquid with some powder) before assembly of the ends to cylinders. Lots of "teaching" videos on the web.
A few pics attached that I took to help someone else see what I do to make boilers. I use 3 Blowtorches, Lots of firebrick, Leather welder's gear, hand protection, etc, safety mask/goggles, boots and brain. - The last is most important.
You need to set-up properly, as when the job is hot, 3 lamps are roaring, and the flux has melted, you don't want to find you forgot something - like solder or tongs?!
And please think to use TINS/metal containers for sand, etc., not plastic containers. (They burn well!).
DO NOT plunge the finished boiler into water, Many a crack has been created by dunking hot metal. BURY the finished job, so heat can dissipate slowly and not develop shrinkage stresses.
The finished boiler will be annealed copper, with the strength of hot toffee.. or wet cardboard... so handle with care when cold. And DO NOT DROP IT! it will buckle so easily... and then you have to start again!
When below 100degrees C (boiling water temp) lower into the pickle, to warm the pickle and encourage rapid dissolving of the flux and oxides. Wash well in water after pickling, before the next step.
OK?
K2
The REGULATIONS are for designs of boilers using SILVER SOLDERED copper . I know Sif-Bronze has some capillary action, but the silver solder is designed for the capillary action of filling a couple of thou gap between the 2 copper surfaces. That's where it gets its strength, not from fillets of solder.
I think the top reason for using silver solder on copper boilers, is the temperature of melt of the solder. SifBronze melts very close to the melting point of copper, although I have used it, but not on boiler work. I have also looked on the web at copper MIG brazing (uses SifBronze wire) or Copper welding (TIG). There is so little information about SifBronze brazing of copper that maybe it is just more risky from the higher temperature required to fuse to the copper?
I use silver solder 55% silver, as this is really easy to use. But if silver soldering in stages, where you need one stage to remain solid while the next stage is made, then you need to ring changes in the silver solder to give you a good range of assembly temperatures. Start High temp., on small sub-assemblies, and lower the melting point of solder at each stage. Needs some homework, research and planning.
Unlike welding, you have to heat a huge amount of the job while silver soldering, so it takes a BIG blowtorch and LOTS OF BRICK INSULATION, so you can get the joints hot (e.g. on shell ends). I bury 3/4 of my boilers in a bucket of sand for insulation, so only the end being worked on is exposed. But the sand must be DRY.
Using the highest melt-point silver solder on bushes, internal reinforcements, etc. is a good idea. Then the sub-assemblies can be assembled together for soldering with a lower melt silver solder. - I mentioned to someone that my boilers were worth more in "silver" than scrap copper! But a good boiler can last more than a lifetime!
PICKLE well between stages, and apply a paste of the flux powder (a drop of washing-up liquid with some powder) before assembly of the ends to cylinders. Lots of "teaching" videos on the web.
A few pics attached that I took to help someone else see what I do to make boilers. I use 3 Blowtorches, Lots of firebrick, Leather welder's gear, hand protection, etc, safety mask/goggles, boots and brain. - The last is most important.
You need to set-up properly, as when the job is hot, 3 lamps are roaring, and the flux has melted, you don't want to find you forgot something - like solder or tongs?!
And please think to use TINS/metal containers for sand, etc., not plastic containers. (They burn well!).
DO NOT plunge the finished boiler into water, Many a crack has been created by dunking hot metal. BURY the finished job, so heat can dissipate slowly and not develop shrinkage stresses.
The finished boiler will be annealed copper, with the strength of hot toffee.. or wet cardboard... so handle with care when cold. And DO NOT DROP IT! it will buckle so easily... and then you have to start again!
When below 100degrees C (boiling water temp) lower into the pickle, to warm the pickle and encourage rapid dissolving of the flux and oxides. Wash well in water after pickling, before the next step.
OK?
K2
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