Brazing/Hard Soldering Questions

[Chiller]

So I've done pretty much all the dry work on my plated still, but now I need to start the soldering.

First of all the hearth, I plan on using one to improve the general brazing process, I have read about different density fire bricks, vermiculite and coke, but haven't been able to settle on what exactly it is that I need: do I use fire bricks and put vermiculite on top? Do I use vermiculite bricks only? Or just fire bricks?

Second, I think I know which solder to use for my copper: 55% silver for general copper-copper brazes, then 15% silver for bigger copper-copper gaps, and regular lead free for the second round (which I already have), not sure what flux to use for these though!

Also I'm not sure how to go about soldering my ferrules to the side of my column - I am going with a through joint for ease of fabrication, but again, there's alot of conflicting info on the net so would appreciate any advice on what solder and flux to use for this.

Sorry for the poor writing skills - its late o'er here

Thanks in advance

[rtalbigr]

I really don't understand about what ya need fire brick, vermiculite, etc for, course that could be my ignorance. For all my brazing with copper I have always used Stay-Silv 15, ya don't need a flux with it. It does require Oxy-acetlene and ya need to carborize the flame and keep it movin' (I do weaves, like stick weldin') or you'll blow holes in the copper.

Big R

[Kentucky shinner]

if your soldering stainless to copper use harris black flux. It is a high temp flux. Keep your flame focused on the copper for the most part. Grind or sand the stainless before yor start then use plenty of flux. Do not over heat the stainless.
good luck,
KS

[Chiller]

The bricks and whatnot is for the hearth, basically just to reflect the heat back at the work. I only have access to mapp, nothing oxy - will 15% work find as a first rounder without flux even if I only use mapp? Btw can't get the exact brands you guys have but we still have a large selection, could you tell me what the reducing component in the flux is KS?

[rtalbigr]

I see what you're talking about with the bricks but I've never fooled with that. With the Stay-Silv 15 it depends on how big your copper is. I've done some small stuff and mapp was ok but anything over 3/4 to 1 in. ya need oxy-acetylene. They do have set ups where you can use oyx-mapp and that might work, never used it though. Another product I have used is called Blockade F.C. It's a lot cheaper than Stay-silv and is flux coated. Works pretty good with mapp. It works good with copper and brass but I do't think it will work with SS.

Big R

[myles]

With MAP you can soft solder up to 2" no problem. I generaly use soft solder for copper to copper and reserve the high silver content brazing for copper to stainless or joints that need to be structural.

I have never yet managed to desolder a brazed joint with MAP.Trying to get enough heat into 2" with MAP for brazing requires an additional heat source. I only did it once and built a small forge with fire bricks and charcoal to heat the tube, and the MAP to just top up the joint.

As you are in the UK have a look at this site. http://www.cupalloys.co.uk/ Lots of good info and the prices are OK too.

[Chiller]

Hmm, alright - btw the reason I planned on using silver for some of the copper-copper work was to have a two-stage solder, for example I would silver solder the small tubes in my shotgun, then soft solder the outside. It really is out of the question to get oxy, but the only reason I'll use the silver is to do the aforementioned - is it still feasible if I use mapp + a hearth? OD managed to do it

[myles]

Thats a perfectly good reason. There are a range of melting point solders availabe for 2 or 3 stage soldering. I have never needed to use oxy yet, the MAP is fine. It sometimes just needs an assist to get the entire bit up to working temperature. a 3 foot length of 2" can soak up a lot of heat.

[Chiller]

So, given that - could you reccomend to me which solders to use for: the stainless ferrules to copper which do not need to be high-temp; and the copper-copper brazes which should be high temp. I have researched the solders but a couple of things are still fuzzy, so confirmation from the experienced would give me great peace of mind

[myles]

No problem. This info is UK based and only relates to the stuff I use (cupalloy). There are other manufacturers.

Stainless - if your stainless is one of the 300 series you can soft solder it with 2207 but you have to use the matching liquid flux. Alternatively use a borax based flux and high silver 455, or if the stainless is of unknown origin use 449 as it also contains nickel. Both are cadmium free and melt below 700 degrees. both can be done with MAP. ONLY heat the copper on a copper/stainless joint.

For the copper/copper or copper/brass I tend to use a generic low% silver, lead free, plumbing solder for most things. Multi stage soldering requires harder solder. 455 is my favourite. Melts at 630-660 degrees and flows well. If it is only on the coolant side then cadmium is OK to use. 842 is 42% silver with cadmium and melts at 610 to 620 degrees. Very widely used. 440 is cadmium free and melts at 650-710 degrees. You can get cadmium free 424 but at 740-780 degrees you will strugle with MAP.

You can also get flux free copper-phosphorous. These are intended for refrigeration use and are not recomended for hot work. Can be fine on the outside of condensers though as the colour match is good on copper. There are dozens of alloys available but a lot are intend to be used at low temperatures and are not really suitable for boiler work.

[Chiller]

Perfect, thanks for that myles, really appreciate it