15 replies to this topic

[catceefer]

I have been using a flux-less copper braze to join copper to copper. I now wish to join some sheets of copper together with the braze between the sheets and not visible at all. I have considered filing the brazing rod to make a powder and then mixing this with either borax or a flux used with ordinary solder to make a paste to smear between the pieces to be joined.

I shall have a go anyway, but wondered whether anyone has tried something similar or has an alternative suggestion?

Thanky ou.

James.

[AvishaiW]

I assume that you are using silphos solder for copper which works nice on copper without flux. The silphos solder is a high temp. Solder and the question is how big are your copper sheets, and how can you heat the sheets to a uniform temperature of about 550 centigrade. If the temperature will not be uniform and your copper sheets are large, I am afraid that the plates might curl and distort.If possible, I would recommend to use a soft solder like the Harris  Stay Brite or Bridgit. The procedure is to flux one plate and cover it with melted solder, and than to flux the second plate, to put it on top and to heat it slowly. You will have to take care that the plates will not move during heating because due to the low surface tension of the melted solder they usually move.

[catceefer]

Thank you for the suggestion. Yes: I have been using a silphos braze. Your approach is the same that I have taken in the past and has proven fine. However, my thoughts for my suggestion were that if any of the solder weeps at the joins, then it will show less than if it is ordinary soft solder. I also thought that I could apply the same technique to joining small copper items where the join is visible and where feeding in a rod of solder would be impractical. The paste would make it easier to keep a small amount of braze in situ. I am thinking of making some copper jewellery and using this method to join components.

Regards,

James.

[AvishaiW]

Good luck James. I hope that it will give a nice solder. Please update us about the results, and it would be very appreciated if you could post a photo. It is always nice to learn something new. Thanks

[Rich Waugh]

James,

What you're doing is  a very old technique called "spelter" - you can probably Google a lot of information on it.  It works just dandy.

[catceefer]

Quote

Please update us about the results, and it would be very appreciated if you could post a photo.

I shall certainly post some images once I have something completed.

Rich Waugh, on 24 April 2012 - 06:44 AM, said:

James,

What you're doing is  a very old technique called "spelter" - you can probably Google a lot of information on it.  It works just dandy.

Thank you for this and I shall do a search. I had always thought that spelter was just a type of cheap metal used for casting imitation bronze statues.

Regards,

James.

[Pat Roy]

I have only found phosporus-copper solder locally(but I haven't looked too hard yet). It melts at a fairly hight temp. The silphos you mentioned, what is it's melting point and what torch do you use in the process? I use my O/A torch for the phos-copper with the smallest available tip but it is pretty hot to use on thin copper. I could use some advice.
Thanks
Pat

[AvishaiW]

Any jewelery supply shop will be happy to sell silver solder. I use 40 % Ag solder which flows very nice. The Silphos solder melts at about 580 centigrade.It is recommended to use a propane torch unless the parts to be soldered are very heavy. Always make sure that the heated joint will melt the solder and not the torch.

[Rich Waugh]

Phos-copper is okay for brazing copper, as is sil-fos, but the melting points of either one are pretty close to that of the copper itself and may cause problems if you're working with thin copper.  Under those circumstances I'd opt for the Sil-fos solder with the higher silver content, such as Sil-fos 15 (15% Ag) or Sil-Fos Plus (18% Ag), rather than the more commonly used Sil-Fos 5 (5% Ag) - it costs more naturally, but it melts at a lower temperature.  Due to the phosphorus content, you shouldn't need to use flux if soldering copper to copper.  Any other metals will require the use of a flux.  

If color match isn't much of an issue, then I'd opt to use regular silver solder in either "Easy" or "Extra Easy" grade, the two lowest melting  points.  You'll need to use a flux like Battern's or something similar (even borax will work), but it flows very well and runs nicely by capillary action in a close-fitting joint.  For soldering steel or stainless steel, it much better than any of the phosphorus-containing solders as it will not cause embrittlement of the adjoining steel.  You may be able to find silver solder in granular form, I don't know.  It is commonly available in both sheet form and wire.

[crquack]

I vote for the Extra Easy. I found it remarkable that using only a MAPP torch one can silver-solder quite large pieces. Has anyone tried this:

http://www.riogrande...y/103099?pos=26

I have not had much luck with some of the other pastes but this one may be different.

[Pat Roy]

Avishai, when you say "propane torch" do you mean propane/oxygen or just propane. My soldering up to now has just be a little plumbing with copper pipe. Now I am trying to assemble parts made from 16 ounce copper sheet without destroying the parts.

Thanks Avishai, Rich and CRQuack.

Pat

[AvishaiW]

I mean just propane. I use a torch about 7/8" in diameter, and I do over 500 solder joints per month without any problems. Propane/oxygen torch is too hot for that and you have to be very careful not to overheat the metal.

[Pat Roy]

Thanks, that's what I needed to know.

[Rich Waugh]

Speaking of propane torches:  The other day while I was at Lowe's in NC, I finally caved in and purchased a Bernz-O-Matic push-button start torch head.  What a treat!  The thing was only a bit over $25 and it makes using the torch so much handier I can't believe it.  I mostly use the torch for lighting the forge, quick heats on tiny stuff, etc, so it is really great to just be able to grab it and push the button and have instant flame.  The one I got is the Model TS-4000.

[AvishaiW]

Rich Waugh, on 15 August 2012 - 03:12 AM, said:

Speaking of propane torches:  The other day while I was at Lowe's in NC, I finally caved in and purchased a Bernz-O-Matic push-button start torch head.  What a treat!  The thing was only a bit over $25 and it makes using the torch so much handier I can't believe it.  I mostly use the torch for lighting the forge, quick heats on tiny stuff, etc, so it is really great to just be able to grab it and push the button and have instant flame.  The one I got is the Model TS-4000.

Sounds like a nice torch to have. Will have to look for it here ( or something equivalent). For sure the price will be 5 times higher

[catceefer]

I have just noticed the renwed activity on this thread.

The rods that I have been using melt at about 710 degrees centigrade. I use a propane torch and large gas bottle when working on large items, but use a Taymar torch and cannister of gas with smaller items. I work with sheet copper down to 0.3mm thin and have no problems with melting.

Regards,

James.