Silver braze/solder

[Ripcrow]

Can someone explain the difference between the amount of silver in the rod and what effect this has on the strength of the weld and the materials to be joined,my local supplier has 2% 15% and 30% rods from 1.6 mm to 3.5 mm rods,I purchased some 2% 2.5 mm rids and tried them their melting point is quite higher than expected and also I notice little gas bubbles in one of my failed welds,I've never done this type of work before so any advice will be appreciated

 

[goldstar31]

Might I respectfully suggest that you read and re-read much the same topic of perhaps only a few days ago. I've been up and down the length of the UK since and my memory is fragmented because of that and old age.

Initially, I doubt that a beginner will succeed using rods which have a high melting point because the silver content is virtually non existent. Once you have melted 2% stuff, you will have next to no silver left to speak of. Consequently, you will be trying to melt something with an even higher melting point. So instead of silver soldering, you are attempting to braze because that is what you have left. You need a lot of heat or if I may be forgiven, A LOT!
Once you have a proper braze joint, it will be far stronger than a silver solder one- but you have porosity. You have either impurities or air or both and are using the wrong technique and heat to get them out. I think that I attempted to explain this.

At this part of your questions, no one knows what you are doing and equally important, what you are using. Basically, you have two roads. Either you bite the bullet and get your wallet spanner out and buy high silver stuff or get your heat sufficient to melt what amounts to brazing rod and its somewhat different technique. With the latter, if you are making small engines out of brass, you stand a high chance that your efforts in machining will distort or melt. On the other hand, if you are mending the garden gate, silver solder is an obvious waste.

I hope that this helps

Norman

 

[Loose nut]

Try this website there is a lot of tech info on solder there. May have strength comparisons.

Usually for models the silver content is near 50%. Easyflow #2 (England 42%) or Easyflow 45 (North America 45%).

The trick to a good silver braze job is the right flux and how to use it.

http://www.lucasmilhaupt.com/en-US/products/fillermetals/1/

 

[Entropy455]

The difference between brazing and soldering is the temperature in which the filler material melts. Greater than 800 degrees is brazing, less than 800 degrees is soldering. Overseas, everyone seems to call silver-brazing “silver soldering” - which is fine, provided they understand the proper flux and heat requirements needed to make the joint.

You must be careful with silver brazing rod, as some of it contains cadmium. Cadmium will out-gas at temperatures greater than 400 degrees F, and will harm you if inhaled (or ingested). Here in the US, our low-temp silver brazing rod is 20% cadmium by weight, and melts just under 1300 degrees F. The advantage to the cadmium, is that the silver-brazing alloy flows very freely (low viscosity) – which is good for brazing pipe joints. Whereas cadmium-free silver rod melts at over 1600 degrees F, and flows more like peanut butter – which is good if you’re trying to make fillet type joints – for general joining of parts.

Your base materials must have a higher melting temperature than your brazing material, or you’ll melt your parts.

Bronze melts hot
Silver melts less hot
60/40 lead-tin solder melts the least hot

Flux is used to encourage the wetting action of the filler material onto your base materials. There are a wide range of fluxes.

 

[goldstar31]

The difference between brazing and soldering is the temperature in which the filler material melts. Greater than 800 degrees is brazing, less than 800 degrees is soldering. Overseas, everyone seems to call silver-brazing “silver soldering” - which is fine, provided they understand the proper flux and heat requirements needed to make the joint.

Respectfully, the answer is 'No' Twice!

In France, the joining process is 'Soudure' for all this airy fairy sticking things together- with metal. To our untutored translation that is 'soldering'

Again, we Brits use the words 'Soft soldering', Hard soldering, Lead loading, tinning, brazing, welding, Tig-ing, Mig-ing and a plethora of words to define the simple joining process.

Sticking metal together is and never was much of a problem. Ask your dear old girls who stuck your wonderful Liberty Ships from the Henry Kaiser Yards to help sort out a beleaguered Britain where I grew up.

Norman

 

[Swifty]

Well, I'm still convinced that according to my experience, silver soldering is done with flux and a various silver content rod that flows into the joint with minimum solder showing, whilst brazing, using flux and a brazing rod, sits on the joint similar to welding. Entrophy455 mentioned that "overseas that call it silver soldering" instead of silver brazing, maybe its only the US that's the odd one out.

There are pictures on this link showing brazed joints.
http://forums.mtbr.com/frame-building/you-suck-brazing-601866.html

Paul.

 

[Hopper]

Well, I'm still convinced that according to my experience, silver soldering is done with flux and a various silver content rod that flows into the joint with minimum solder showing, whilst brazing, using flux and a brazing rod, sits on the joint similar to welding. Entrophy455 mentioned that "overseas that call it silver soldering" instead of silver brazing, maybe its only the US that's the odd one out.

There are pictures on this link showing brazed joints.
http://forums.mtbr.com/frame-building/you-suck-brazing-601866.html

Paul.

Yes, here in Oz, silver soldering generally refers to using EasyFlo 40-50 per cent silver solder, which is silver in colour. Can be done with oxy or with propane torch if the job is not too big.

Brazing, here in Oz , generally refers to using the yellow coloured brass rod and an oxy torch to join two bits of metal.

But it gets complicated because there is also sif-bronze welding which requires special technique and is used on Norton motorbike frames and their replicas. Seems the Brits claim to specialize in this technique.

And now the Strine gumment in its infinite wisdom has banned lead from solder for plumbing, so that solder now comes with 2 per cent silver and is marketed as "silver solder", confusing the heck out of everyone.

Back to the OP, there is a very good book in the Workshop Practice series on Soldering and Brazing that is well worth a read.

 

[GWRdriver]

Well, I'm still convinced that according to my experience, silver soldering is done with flux and a various silver content rod that flows into the joint with minimum solder showing, whilst brazing, using flux and a brazing rod, sits on the joint similar to welding

That's exactly how I would describe it.

Entrophy455 mentioned that "overseas that call it silver soldering" instead of silver brazing, maybe its only the US that's the odd one out. - Paul

Paul,
It's only a very few who insist upon calling it brazing. The majority of model engineers and live steamers in the USA use "silver solder." I think the confusion about brazing arose some years ago with the great increase in Gauge 1 live steam activity in the USA and the subsequent desire of folks to build their own boilers. At that time many DIY big box shops were selling solder products labeled "Silver Solder" but which were actually silver bearing solder (when you read the fine print.) Folks momentarily flocked to this because it avoided costly torch gear and special flux, resulting in unusable, or at least unsafe, results. At that point some people began to use silver brazing to distinguish between high temp and low temp silver solders. Even the largest US manufacturer of silver soldering materials labels their products "Silver Solder."

 

[chucketn]

I agree with Hoppers' explanation. That's how I learned it many years ago. My Dad could lead solder, silver solder, braze or weld with stick or oxy/acet. I now have his B tank and torch set. I wasn't taught by him how to solder, and have fallen for the silver bearing vs silver solder hype myself. Miss him terrably...
Chuck

 

[TimTaylor]

The following link will provide you with more information than you probably want to know about a wide variety solders and their applications:

http://en.wikipedia.org/wiki/Solder

 

[chucketn]

Thanks for the Wikipedia link, Tim. I taught High Reliability Soldering for the USAF at a Field Training Detachment for almost 10 years, and there was info in that link I didn't know!

Chuck

 

[Entropy455]

Even the largest US manufacturer of silver soldering materials labels their products "Silver Solder."

Curious - which manufacturer might that be?

http://www.harrisproductsgroup.com/en/Products.aspx

Above is a link for a large manufacturer & global distributor of brazing and soldering alloys. Note that they advertise a silver-solder within the "soldering" section, that melts well under 800 degrees F. Also note that silver brazing rod is labeled and advertised within the "brazing" section, and melts over 800 degrees F.

One alloy is safe for elevated temperature & pressure steam joints, whereas the other alloy would be very dangerous (as others have already pointed out.) It's an unsafe practice to identify a brazing operation as soldering.

Whenever I task a pipe-fitter to makeup a brazed joint, I identify the piping base material, the fitting base material, the required flux, the required silver alloy, system fluid, system operating temperature, and operating pressure. I also task any non-destructive testing requirements that I require - such as a hydrostatic tests, VT inspections, UT inspections, etc - depending on the criticality of the joint.

Please don't take offense to my comment that overseas folks often call silver-brazing by the wrong term - as it happens to be a true statement. Besides, here in the US we have more than our share of screwed up technical terminology. . . . .

 

[Ripcrow]

I had a lot of trouble finding silver solder in aus every time I asked for it I got a dumb look or got shown the little roll of silver solder for electrical work,it wasn't until I asked for silver braze that I got what I needed just wasn't sure on strength verses silver content properties.thanks for all your replies

 

[TimTaylor]

Ripcrow,

Sorry if you got buried with too much info - here's the simple difference:

Both silver solder and silver braze alloy are Sn/Ag alloys.

Silver solder has silver content in the 3-5% range and melts in the 424-570 deg F range

Sliver braze alloy has silver content in the 30-50% range and melts at 1100 def F or higher

The higher silver content of silver braze alloy makes it significantly stronger.

It should also be noted that a good brazed joint relies on capillary action drawing the braze filler into the joint, so clearances are important. Optimum joint strength is achieved with clearances in the 0.002"-0.003" range.

Hope this makes it a little clearer.....

Tim

 

[robmort]

From the Cupalloys site:
'One definition in British Standards defines brazing as : "a process of joining generally applied to metals in which, during or after heating, molten filler is drawn into or retained in the space between closely adjacent surfaces of the parts to be joined, by capillary attraction"
International Convention declares that brazed joints are made above the melting point of aluminium 610 degC. Below that temperature you are soldering. A brazed joint is identified by the temperature of the filer metal, not by the composition of the rod in the hand.
The key words are by capillary attraction. Everything that you do, joint design, fluxing, heating is aimed at promoting capillary flow. If this is not done you are not brazing.'

Hence all the silver solders available, as well as the sifbronze alloys, are used to "braze" strictly speaking, but of course "silver soldering" is a term often used in practice,

 

[Swifty]

I think that this discussion may go on for ever. I would like to give an example of a brazed joint, if we use some tubing, such as they use on bicycle frames, and attempt to braze one piece on to the other at 90deg. The joint is fully prepared, with the end of the tube sticking up machined to suit the radius of the base tube, we then braze relying on capillary action to draw the braze into the mating surfaces, with no excess braze on the outside. Job done, maybe, grab the top of the tube and apply a force, will the tube bend or the joint come apart, my feeling is that after a slight bend the joint will came apart.

We now repeat the same preparation, braze the joint making a nice fillet with the filler material, as you can do with correct brazing rod, and then do the same test trying to break the joint. My feeling here is that the joint will be much stronger due to the fillet adding a lot of support. With true silver solder it is almost impossible to get a fillet joint due to the solder wanting to flow and not sit there.

Paul.

 

[TimTaylor]

I think that this discussion may go on for ever. I would like to give an example of a brazed joint, if we use some tubing, such as they use on bicycle frames, and attempt to braze one piece on to the other at 90deg. The joint is fully prepared, with the end of the tube sticking up machined to suit the radius of the base tube, we then braze relying on capillary action to draw the braze into the mating surfaces, with no excess braze on the outside. Job done, maybe, grab the top of the tube and apply a force, will the tube bend or the joint come apart, my feeling is that after a slight bend the joint will came apart.

We now repeat the same preparation, braze the joint making a nice fillet with the filler material, as you can do with correct brazing rod, and then do the same test trying to break the joint. My feeling here is that the joint will be much stronger due to the fillet adding a lot of support. With true silver solder it is almost impossible to get a fillet joint due to the solder wanting to flow and not sit there.

Paul.

Paul,

I don't disagree with what you said at all, but the O.P.'s original question was the difference between SILVER solder and SILVER brazing.

You have introduced a 3rd process into the mix which is commonly referred to as braze welding or simply brazing, which uses an entirely different class of filler alloys that are primarily copper based, melt at much higher temperatures and have a much higher tensile strength, typically several orders of magnitude greater than the tin/silver alloys. The fillet buildup you describe is a characteristic of this process and adds strength to the joint.

Tim

 

[Swifty]

I see your point Tim, the confusion arises by what appears to me to be a modern term, silver brazing. When I worked for a living, we only had either silver solder of various silver content or brazing rods.

Paul.

 

[OrangeAlpine]

From the Cupalloys site:
'One definition in British Standards defines brazing as : "a process of joining generally applied to metals in which, during or after heating, molten filler is drawn into or retained in the space between closely adjacent surfaces of the parts to be joined, by capillary attraction"
International Convention declares that brazed joints are made above the melting point of aluminium 610 degC. Below that temperature you are soldering. A brazed joint is identified by the temperature of the filer metal, not by the composition of the rod in the hand.
The key words are by capillary attraction. Everything that you do, joint design, fluxing, heating is aimed at promoting capillary flow. If this is not done you are not brazing.'

Hence all the silver solders available, as well as the sifbronze alloys, are used to "braze" strictly speaking, but of course "silver soldering" is a term often used in practice,

This makes no sense to me. It states that in brazing, you do everything possible to promote capillary attraction and if this is not done, you are brazing.

Or am I reading this wrong?

Bill

 

[GWRdriver]

It appears this will be a case of irresolvable semantics, and a function of where you live, what you read in books and mags, who taught you, what name those around you called it, and what the local suppliers and sellers called it. Here's a photo of a few of the silver solder containers I have, the majority of which are Harris and say "Silver solder" like the middle one. But the newer Harris packaging, as on the left, doesn't label it either way, cleverly dodging the issue! The Silvaloy packet on the right does indeed call itself silver brazing alloy. Yer pays yer money and yer takes yer choice. I think the important thing for us (model builders) is to get the silver content right, meaning appropriate for the job at hand, and then you can call it whatever you like.