Please help!! Silver soldering/brazing confusion

[Hicube]

Hi all! Please excuse me this is my first time posting here on the forums. I am currently building a Alpha-type Stirling engine based off the Alpha Victory by IronHorse. You can read it here at http://www.homemodelenginemachinist.com/f31/alphavictory-engine-build-8343/

I have built most of the components and I am currently attempting to joining the brass pipes and the regenerator by silver soldering/brazing. Joining metals by heat isn't my forte unfortunately and i have a lot to learn. :wall:

I am currently confused as to the differences in silver soldering and silver brazing. Sometimes the terms seemed to be used interchangeably sometimes they seem worlds apart.

I need to produce air tight joins between, brass and brass. aluminium and brass as well as 303 stainless and brass.

Currently I have attempted by to no success in trying to join brass to brass. Only resulting in a melted brass tube which was supposed to be my regenerator. :fan:

I am equipped with the following: BernzOmatic TS8000 torch using MAPP
BernzOmatic Nickel Silver Brazing Rods
Durafix aluminium soldering/brazing rods
Ezi-weld 602 flux
Are these items sufficient to get the job done or have I bought the wrong items.

Any advice would be appreciated!! Thanks

 

[goldstar31]

I'm a certified welder( or was) but a British one. Things and names may be different but what you are actually looking for can be summarised into

1. Getting enough heat to melt the solder rod
2. Getting enough heat onto both bits of metal
3 . Getting the melted drop of molten solder between 1 and 2 to stick the bits together.
For that you need flux and you need sufficient heat- and no more heat.

OK, I've been at this for a long time and a lot longer than when I 'qualified' but I watched the way that beginners were taught. Eventually, they would be able to join a sawn through wing or bumper on a car - and have it perfect for a professional paint finish but they started with nothing more basic than a bit of scrap metal, a bit of flux thinned with water and a rod and heat to make a weld pool of molten solder on a bit of scrap. If the whole thing ended up as a bit of cinder toffee or aero chocolate or whatever, the heat was insufficient. If they overheated, there would a pool of hot metal in your sox and a lot of swear words. You have to get that pool. Once you are happy with that , move on to joining two sheets of thin scrap that are clean and have flux between the joint. Carefully balance a tiny bit of solder on the joint and warm it up until it melts- and it should flow into the joint.

You can then run around the workshop waving a flag or getting drunk or your thing.
You are there.

I was watching Quest on TV last night and someone made and soldered up a tuba. Nice!

Cheers

Norman

 

[GWRdriver]

I need to produce air tight joins between, brass and brass. aluminium and brass as well as 303 stainless and brass.

Not being a "Stirling" motor person the first question I need to ask, in order to try to answer your questions, is what temperatures will these joints be subjected to?

 

[Hicube]

Hi Norman, Thanks for the input!

I suspect I am using the wrong brazing rod. The working temperature it is specified to be 910C however brass melts at around 930C. I have my eye on some 45% silver rods from Harris which becomes liquid at 743C and has high fluidity.

I am also thinking the way I have the workpieces set up in the vice will affect how the heat is distributed along the workpieces. Do you think isolating the pieces from the vice will improve my chances? Also perhaps some practice is in order before I destroy some finely machined parts. :hDe:

Cheers Pat

 

[Hicube]

Not being a "Stirling" motor person the first question I need to ask, in order to try to answer your questions, is what temperatures will these joints be subjected to?

Hey mate, I have designed my engine to run at from 400-500C. So the means the joint closest will be required to be the most resistant. The other joints would ideally be of the same standard. But with the brass to aluminium joint silver solder doesnt seem to work from what I have read. Thanks for your time!

 

[goldstar31]

Pat, adding things like big bits of metal like vices only adds a heat sink- which you should try to avoid. If you can, fasten bits with a bit of wire temporarily. Again, shield your work with firebricks to concentrate your heat onto the work. Basically, you want red heat to do things.

You'll enjoy success!

Norman

 

[Hicube]

Pat, adding things like big bits of metal like vices only adds a heat sink- which you should try to avoid. If you can, fasten bits with a bit of wire temporarily. Again, shield your work with firebricks to concentrate your heat onto the work. Basically, you want red heat to do things.

You'll enjoy success!

Norman

Yes I was thinking something like that would affect my job. Looks like I have some new things to try out. Thanks for your input. I will keep this thread updated until the job is done.

Pat

 

[Till]

Cheap electric cooktops (the ones with a cable attached) are getting red hot if left at maximum for some time. I use one of the white ones like these
https://www.google.de/search?q=elek...e&btnG=Suche&gbv=1&um=1&hl=de&tbm=isch&tab=wi
for heating up the workpiece when brazing. You’ll only need very little additional use of the torch to reach the required temperature for brazing.
When soldering, use one of lower temperature settings and apply the extra heat with an electric heat gun. It’s a very save way to work and it’s almost impossible to burn the flux on accident.

It’s very useful for heat treatment, too. You can establish very slow cooling by heating sand (or bricks) on the other plate to cover the work piece later.

 

[vascon2196]

Typically Brazing processes use filler material with a melting temperature above 840F where Soldering is done below 840F. Both create a mechanical bond because they don't heat the base material above their melting temperature.

I have been told by Soldering/Brazing specialists that a good clean surface, the proper flux, and heat all have a direct effect on the results.

For me its hit or miss when it comes to soldering...I guess I need more practice.

 

[Hicube]

Typically Brazing processes use filler material with a melting temperature above 840F where Soldering is done below 840F. Both create a mechanical bond because they don't heat the base material above their melting temperature.

I have been told by Soldering/Brazing specialists that a good clean surface, the proper flux, and heat all have a direct effect on the results.

For me its hit or miss when it comes to soldering...I guess I need more practice.

Yeah I figured that out the hard way when I melted one of my parts by the filler material was just starting to melt. I have ordered some silver soldering rod that melts at a much lower temperature than brass. Thanks for your comment!

 

[Oilydog]

The main thing to remember is to concentrate the heat on the denser of the two parts to be joined. The smaller piece will be drawing reflected heat, and only when the larger us up to temperature should the torch play over the smaller piece, and then quickly apply the pre-fluxed solder rod.

Trust me I'm a silversmith!

 

[Chiptosser]

As you are finding out, soldering and brazing are two different processes.

Soldering is just a bonding or joining metals with a alloys of dissimilar metals at what is considered low temperature, and lower strength.

There are soft solders and hard solders, soft mostly consists of lead, tin, and other alloys. The percentages of each alloy determines the melting point of each type of solder, ; 60/40, 50/50, 70/30 ect.

Silver solder, is considered a hard solder, there are many variations in the compositions of silver solder. Different percentages of silver in the solder determines the melting point and the strength of the solder joint.

Brazing is a higher temperature process, usually using a brass alloy filler , as with the other materials, brazing rods come in different alloys, for different applications. This is a higher temperature process.

I am not going to get into the temperatures of each here, it all varies with the material and mass , ect of what is being bonded.

One of the biggest mistakes people make when silver soldering and brazing is ; not using the proper amount of heat, and the biggie, --- using the proper flux!

You can not use rosin flux for silver soldering! You need the proper flux for your material.

Oh, and always flux the area that you want the solder to wick to, this will take practice, soft solder acts different than silver solder. Practice!!

I Strongly suggest not to, try silver soldering with the flux on the rod!
Remove the flux from the rod, use it in the joint, I would suggest getting
the paste flux.

I am leaving this open here, as you can surmise, you will have to some research on your own for temperatures for your filler.

Brazing,? I'll let someone else go into that, I don't consider this hobby forum the place that, many people have the equipment to properly heat
parts for brazing with the different brazing alloys.

Like all endevers, Practice, Practice, Practice

Good Luck

 

[TimTaylor]

I'll second what Chiptosser said.

There are different brazing rod alloys for different applications, but the majority are predominately copper, with phosphorous, silver, zinc or other additives to get the desired characteristics.

Silver soldering can easily be done with a small propane or butane torch, but for brazing I use oxy-acetylene adjusted for a neutral flame.

It's not a hard process to learn - the keys are good joint preparation and having the right equipment.

The fumes are nasty- be sure to work in a well ventilated area and wear a filter mask if necessary.