silver solder?

[digiex-chris]

Sorry, but your post also suffers from the lack of detail you speak of. What do you recommend to pickle the object with? Are there agents you buy, or do you make them? Many of us are here looking for details because we lack the experience. There are thousands of cleaning products and we need the experts to help us weed them out!

 

[goldstar31]

I thought that I had prattled with enough details earlier but if other will forgive repetion.
You need a flux to silver solder. For most purposes an ordinary borax one will suffice. If you are onto things like stainless, you might need a so called better one. Again, you can use a silver solder paste which has flux and etch in it. I would still borax flux on the succeding operations. However, using a simple borax flux( or proprietory powder) it is applied to a cleaned bit of metal. Cleaning the metal means cleaning it properly. If it is pretty clean, a bit of clean emery or glass paper or cloth should suffice to remove any light corrosion. If it is highly corroded or something like cast iron, it should be pickled either in an acid or a strong alkali. I like dilute sulphuric which removes casting sand as well as rust and grease. Others will say Hydrochloric or Phosphoric acids whic may be rust,drain or limescale removers in the normal life. Others will clean off with caustic soda which will also do drains and rust and if you are so inclined, get rid of your mother in law completely! Large bath, large amount of soda and large mother in law- and all down the plug hole. You can also chop her up and cook her and invite the police to a banquet but I digress. You have a squeeaky clean mother - no, couple of bits of metal! Time to flux it and the flux is made into a thick paste with water to which a bit or drop of detergent is added. The reason for the paste rather than the powder is obvious- if it is dry, the torch might blow it away before it is melted to a glassy molten state. Time to use that silver solder and time to realise that is silver and expensive. You only cut or snip what is needed. If it is a pipe, you make a ring if you have a larger job, you might have to go with a stick which is dipped in flux. Here the heat comes in. This is where you have to judge just how much heat and how little heat you need. If you are doing a tube, the little ring should melt by circling the torch to even out the heat. It should melt evenly with dross./old flux/dirt on the top of the melt. You should have something which is wicking rather than cinder toffee. Do you still have that?
Ok, if you have been playing with a copper locomotive boiler you will not be able to do it all at one heat and the copper will have hardened. With the whole thing red hot, you mutter a prayer and dodge the splashes dunking it all into a pickle bath which will do three things. It will remove the old flux, it will soften the copper and scare the **** out of you.

My old mate's Simplex boiler, he and me had the oxy/acetylene going madly and tube after tube went in. Having a spit and a drag, the hot boiler was dropped quickly into the sulphuric pickle bath which was a porcelain sink with lead plugs.

And then he had a minor heart attack. So I had to shut off the regulators, give him nitro glycerine tablets( yea, they can go bang) and get him to hospital.

Well you did ask! The first aid course will follow after a short commercial break.

 

[davedfsme]

Goldstar,

I'll gladly forgive any repetition, if you'll allow me to fill in a few details . . .

Acid Pickle: I like sulphuric acid pickle too. Cheap, easy to find (any automotive battery shop) and effective. Minor downside is disposal once it is played out. Do not use full strength from the chemist (or battery shop), it needs to be diluted IN water (NOT "with water"!!! The distinction is very important!). "Water" contains impurities, which in reacting with the concentrated acid, releases heat energy. The last thing you want is a violent reaction in a mass of concentrated acid, erupting all over you and your surroundings! Add the acid to the water SLOWLY, and any reaction disperses through the water. If it starts to boil, STOP adding, and the reaction will stop too. Probably obvious that you want to stir while adding . . .

How much to add? To think as a chemist, you will know the concentration of the acid you are adding, and have calculated your dilution ratio based on the final concentration desired. Knowing the final volume of dilute solution you intend to produce, it would be a simple matter to calculate the volumes of each component required. This would be the most correct and logical way to proceed.

I am not a chemist, I'm a shop rat. I want my pickle to produce a nice "salmon pink" surface on my copper parts in less than 20 minutes soak at room temperature (even less from hot), and I still want time to get my jeans off before my skin starts to bubble if I get splashed. (If that happens, have a COLD shower immediately, wash with baking soda to neutralize the acid, soap to get rid of the salty residue, and seek medical attention if blisters pop out.) Using commercial battery acid, I started with 10 parts water/1 part acid. Add acid to the bath until you are happy with the results. As the acid is depleted by reaction with the parts going through the bath, it will need to be replenished. If you don't the reaction will slow down . . .

The acid bath needs to be kept in a container that it won't react with . . . this, too should be obvious. I use a plastic bucket, but this is not ideal. If I drop a hot component, it may melt a hole in the bucket. Goldstar's porcelain sink with lead stoppers solves that problem, but is hard to seal for long-term storage. A steel bucket is likely to rot through in a month . . . with poisoned pickle all over the floor. LBSC reportedly kept his in a lead-lined wooden box, but this might be less than ideal too.

BTW, and IMHO, heat softens copper. Quenching just cools it faster. Cold-work (bending) will harden it, but simple heat will soften (temper) it again as long as it is not stressed to the point of cracking.. Quenching has no effect on the ultimate hardness. If someone has proof otherwise, I'd like to hear it.

Anybody remember the grade school "bottle rockets" or "volcanos" using vinegar and baking soda? That was intended to teach you that mixing even "kitchen materials" can cause violent reactions . . .

Ask any high school chemistry student how to speed up a chemical reaction . . . add heat. Allow your parts to cool at least until "black" (all traces of red heat are gone, in the dark (turn the lights out)) before plunging into the bath. You still want enough heat for thermal shock to crack loose the "glass-like" flux deposits. Expect a violent boil! You have the heat of quench, plus the acid reaction. This does nasty things to the atmosphere, don't do this in an enclosed space next to your lathe. Acid solutions should be kept in an outbuilding, tightly capped. Fumes released will cause corrosion. I rely on the lid seal of the bath container (in a somewhat heated space) to keep the fumes in while keeping the solution from freezing and bursting the container during the winter.

My mentor, Jim, advocated citric acid for a pickle for "non-ferrous" parts. Not only is the pickle less hazardous to your skin, it doesn't cause nearly the same level of corrosion due to fuming. Citric acid is available from health food or wine-making stores, but they often look at you funny when you try to buy 2 kilos at once to make up 20 litres of bath. IMHO, it works OK for copper-based alloys if you can let it soak long enough, but it ain't worth a $#!t for ferrous parts.

If you opt for a sulphuric acid pickle, keep a separate bath for ferrous parts. Iron poisons copper, and the other way around too. In fact, you can copper plate steel parts with the spent copper pickle . . . Someone correct me if I am wrong, but the green color and the blue precipitate in a "copper" sulphuric pickle tank is due to copper sulphate? Was that not used as marking out fluid before Dykem Blue? (I apologize for asking for answers at the same time as offering others, but we all learn something new everyday.)

Regarding poisoning acid baths; Do not use "spent" or recycled battery acid for bath material. New stuff is OK, but used stuff is polluted (poisoned) with lead.

Like I said, I'm just a shop rat. Any chemical engineers ringing in might have some words of wisdom to keep this thread alive.

DJD

 

[rkepler]

How much to add? To think as a chemist, you will know the concentration of the acid you are adding, and have calculated your dilution ratio based on the final concentration desired. Knowing the final volume of dilute solution you intend to produce, it would be a simple matter to calculate the volumes of each component required. This would be the most correct and logical way to proceed.

The industry (at least for jewelry) doesn't use sulphuric acid but instead a compound sold as "Sparex". You can buy Sparex but it's usually cheaper to buy sodium/potassium bisulphate more commonly known as "dry acid" at a pool or spa supply. Mixing this about 1 pound to a gallon of water makes a decent pickle.

I mix mine in a 5 gallon plastic pail, the same one available at hardware stores with the snap on lid. Mine usually had 4 gallons or so of solution and lives on porch outside my shop next to the clear water rinse pail and 5 gallon salt water quench pail.

When the pickle action gets a little slow I degrease some steel wool and toss it in for a while. I try to remember to pull it in an hour or so, it'll come out with a bunch of black gook that's a lot of the copper from solution. If that doesn't clear the blue/green color I do it again. It's not necessary unless you're using the pickle a lot.

The acid in the pickle will blow a hole in your jeans at the next wash, but won't eat up skin (maybe if you held it under for a while) - i.e. I've reached in to grab stuff I couldn't hook with a wire. It'll burn pretty good in a cut (almost as bad a Hoppes #9) , so I rinse pretty fast.

An old pickle will plate copper on steel but not so bad that it can't be removed with a shop towel. Yes, an old marking compound was made from fairly concentrated copper sulphate. I like Dykem (or a Marks-a-lot) better.

BTW: another cleaning method I've used is to bead blast things. That does a nice job of stripping scale from hot rolled steels. You've got to clean things again afterwards as the dust left behind will interfere with silver brazing.

 

[Entropy455]

I’ve had good luck removing oil from freshly machined parts by running them through the dishwasher. Use a little extra Cascade dish washing detergent, and set the dishwasher on “pots and pans” and “high-temp wash”. . . It’s not high tech, but it’s safe, and pretty effective. If your parts are ferrous steel, don’t let them air-dry in the dishwasher, as they’ll rust up real quick.

With regard to removing oil from Cast iron. There’s only one effective way that I’m aware of – heat. A lot of heat. You can bake a seasoned cast iron engine block at 600 degrees F for a few hours, and you’ll cook out all the oil. Then use a gentle steel shot to remove the residual carbon, and also clean up any loose iron oxides. Anyone who has ever had a cast iron engine block “shake-n-baked” knows exactly what I’m talking about. It removes the oil, rust, paint, etc, and makes the part look brand new from the foundry.

For silver brazing steel, you’ll want to use Type-B flux.

Is the crank pin the same material as the crank? If so, why not TIG weld it together? It’s a low heat input process (compared to brazing), and you can accurately place small weld beads.

 

[digiex-chris]

Interesting, that's what I was looking for! rust/limescale remover? That's pretty easy, don't have to go far to get it! Thanks!

Who knew something like silver soldering could be controversial.

 

[goldstar31]

Interesting, that's what I was looking for! rust/limescale remover? That's pretty easy, don't have to go far to get it! Thanks!

Actually it is closer than you think! Simply vomit and you have hydrochloric acid all ready and waiting. Quite a bit of a basic explosive too if dried.
Better still have a pee and dry it. You are now a fine candidate for an exteme political organisation

Nothing controversial , you've been creating these things all your life.

See what you missed?

 

[Entropy455]

http://www.everyspec.com/FED_SPECS/O/O-F-499D_21857/

Go to the above link, and download the document O-F-449 (it’sfree). This is the US Federal specification for low-temperature brazing flux - specifically for use with silver brazing rod (approximately 1250 to 1600 degree F, depending on the alloy of the silver being used). Type A flux is generally used for brazing aluminum bronze. However Type A flux is sometimes used when brazing stainless steel to ferrous steel. Type B is the “general use” flux for silverbrazing.

You do not want to use brazing flux that’s intended for use with brass rod, as the lower melting temperatures of silver braze will not properly activate the bronze flux. It won’t properly clean the joint, and you’ll have poor wetting action with the silver.

Grade-3 silver is Cadmium free, and is also known as Bcup-5. It has the highest melting temperature of the common silver brazing alloys. The advantage is no cadmium exposure. The other advantage is that Grade-3 silver has a wide temperature range of plastic behavior – where the braze can be applied thick like peanut butter, or you can increase the heat input and get it to flow fast like melted table butter.

Grade-4 silver is 20 percent cadmium by weight, and it transitions from solid to liquid over a span of just a few degrees F. Thus Grade-4 silver will always flow fast and wet. It is difficult to obtain fillet-type beads with Grade-4, whereas you can make nice fillet beads when brazing with Grade-3. Also note that if you use Grade-4, a portion of the Cadmium will become airborne once heated over 400 degrees F. Thus use plenty of ventilation if you use Grade-4.

There are low-cost (DC only) TIG machines out there. They are sold-state, thus they are light weight (no transformers). The advantage is that you can make textbook welds on steel and stainless steel, however becausethere’s no AC function, you cannot weld aluminum or magnesium. The sold-state technology has really driven the cost of these machines down. You can use an air-cooled torch up to about 150 amperes. There are air cooled torches that are rated for more than 150 amperes, but trust me – water cooled is the way to go – and they’re not that much more expensive. You’ll also need an Argon bottle with an adjustable flow regulator - one that meters in the 10 to 30 CFH (cubic feet per hour) range. Look into it. These DC only solid state TIG machines are impressively inexpensive. You can get them in both 120 volt, and 240 volt single phase (and both 50 and 60 Hz).

 

[goldstar31]

No Entropy455! I doubt that anyone here will want to bother with what in plain English could be described as the Exuberance of Your Own Verbosity.
The poster wanted to deal with a simple task and provide a quick inexpensive solution. He didn't want to go out and listen to you spouting endlessly on your so called expertise. If you look at the response by the poster to this developing charade, you will notice that he has gone into hiding and has yet to reply.

For me, if that was your intention, do realise that I would have chosen to simply peg the part and drop a couple of bits of soft solder in.
There is no stress in a toy engine to need much more than that.

 

[Entropy455]

No Entropy455?

As with most things in life - there's more than one way to braze a joint. I linked a federal specification that governs the manufacturing of silver-braze flux. I also identified two of the more common silver brazing alloys, together with some advantages and disadvantages of each.

You implied that barfing and/or urinating on parts is a viable cleaning method. . . .

Aydelott, which posts did you find more useful, mine, or goldstar31's?

So goldstar - I am curious. Earlier you stated that you hold Engineering qualifications. Which qualifications exactly? Please do tell. . .

 

[Herbiev]

Goldstar31. Please keep it civil. Insulting another members post is not what this forum is about. A question was asked and members provide answers to the best of their ability.

 

[goldstar31]

Goldstar31. Please keep it civil. Insulting another members post is not what this forum is about. A question was asked and members provide answers to the best of their ability.

Actually I gave sufficient information earlier. It should have sufficed.

What was important was that I gave,or I hope that I gave sufficient information for the original poster to make a basic joint using silver soldering standard techniques.

The joint could have been made- and has been made by far simpler joining techniques and on that I later commented .

If I haven't given sufficient information to the original poster to solve his problem, I can only offer him my apologies.

 

[Herbiev]

As the questions have been answered in detail and posts are becoming a little "heated" I suggest closing this thread and move on.

 

[digiex-chris]

http://www.everyspec.com/FED_SPECS/O/O-F-499D_21857/

Go to the above link, and download the document O-F-449 (it’sfree). This is the US Federal specification for low-temperature brazing flux - specifically for use with silver brazing rod (approximately 1250 to 1600 degree F, depending on the alloy of the silver being used). Type A flux is generally used for brazing aluminum bronze. However Type A flux is sometimes used when brazing stainless steel to ferrous steel. Type B is the “general use” flux for silverbrazing.

You do not want to use brazing flux that’s intended for use with brass rod, as the lower melting temperatures of silver braze will not properly activate the bronze flux. It won’t properly clean the joint, and you’ll have poor wetting action with the silver.

Grade-3 silver is Cadmium free, and is also known as Bcup-5. It has the highest melting temperature of the common silver brazing alloys. The advantage is no cadmium exposure. The other advantage is that Grade-3 silver has a wide temperature range of plastic behavior – where the braze can be applied thick like peanut butter, or you can increase the heat input and get it to flow fast like melted table butter.

Grade-4 silver is 20 percent cadmium by weight, and it transitions from solid to liquid over a span of just a few degrees F. Thus Grade-4 silver will always flow fast and wet. It is difficult to obtain fillet-type beads with Grade-4, whereas you can make nice fillet beads when brazing with Grade-3. Also note that if you use Grade-4, a portion of the Cadmium will become airborne once heated over 400 degrees F. Thus use plenty of ventilation if you use Grade-4.

There are low-cost (DC only) TIG machines out there. They are sold-state, thus they are light weight (no transformers). The advantage is that you can make textbook welds on steel and stainless steel, however becausethere’s no AC function, you cannot weld aluminum or magnesium. The sold-state technology has really driven the cost of these machines down. You can use an air-cooled torch up to about 150 amperes. There are air cooled torches that are rated for more than 150 amperes, but trust me – water cooled is the way to go – and they’re not that much more expensive. You’ll also need an Argon bottle with an adjustable flow regulator - one that meters in the 10 to 30 CFH (cubic feet per hour) range. Look into it. These DC only solid state TIG machines are impressively inexpensive. You can get them in both 120 volt, and 240 volt single phase (and both 50 and 60 Hz).

Good info, thanks! Now I know how to go shopping! It sucks going into the welding shop and not knowing what words I should be talking about.

That's an interesting idea I've had in the back of my mind since I saw one of those little solid state tig machines. I can actually get a setup cheaper than I can get small porta-torch kit. I've been brazing using one of those burnzomatic propane/oxygen combos, which is depleted in about 10 minutes of work and is hard on the pocket book if you need lots of it. I'm going to think more seriously about that.

 

[rkepler]

That's an interesting idea I've had in the back of my mind since I saw one of those little solid state tig machines. I can actually get a setup cheaper than I can get small porta-torch kit. I've been brazing using one of those burnzomatic propane/oxygen combos, which is depleted in about 10 minutes of work and is hard on the pocket book if you need lots of it. I'm going to think more seriously about that.

My experience is that brazing needs more heat than high temperature, and that the tool for that job is a large propane/air torch. Some like the Sievert, I like the Goss. The smaller ones run about 25K BTU and the biggest I have runs about 300K BTU. I think the typical torch on a bottle would run about 10K BTU. Here's an image with the large on the left and smaller on the right:

These are run using fairly high pressure (12-20psi) using a high pressure regulator on an LP gas bottle. The big one will freeze up a BBQ bottle if you run it fairly long, but it puts out a heck of a lot of heat in the process.

 

[goldstar31]

In an earlier and less afluent era, I bought a second hand AC welder with 50-75-100 amps outlets. I made up a a pair of carbon arc welders. One was for spot welding car panels whilst the other employed two rods in a sort of jig and generated enough heat to melt prefuxed brazing rods ( not merely silver ones).
It is no use me recommending that welder but extremely cheap arc welders ( £30 in tht UK) from places like Aldi and lidl which you have in the US as well as here in UK. Finally, I started to run 16g mild steel rods to replace car panels and to do repair panels.
It obviates having gas bottles which certainly incur hefty insurance hikes here as well as criticism from the local authorities for both storage and transport in unauthorised motor vehicles.
OK, I'm or was a City and Guilds Motor Vehicle Restorer with all sorts of distinctions and a Certified Welder - and all that jazz but it reached the point where it was no longer permitted to do repairs etc using oxy/acetylene on high strength low alloy steels on vehicle bodies and becoming expert within the law for even home vehicle repairs.
I suspect that the US etc are far more accomodating in this direction.
Sadly, it is a bit snotty in my neck of the woods where permission is needed to prune a tree- mine are all subject to Tree Preservation Orders and even a small propane or butane gives rise to objections.
However, I hope that these snippets will be accepted as a guide to others who may be more fortunate

 

[Entropy455]

http://i797.photobucket.com/albums/yy259/dhem7/DSC03308.jpg

Take a look at this link. (Note: I did not build this part. I simply found the link on Google).

Pay particular attention to the high-quality fillet beads on this brazed joint. These were made with brass/bronze brazing rod, not silver. This joint was almost certainly made with an Oxy-Fuel torch, and not a fuel-air torch. It is much easier to get tight fillet beads like this using the intense focused heat of an Oxy-Fuel torch. A fuel-air torch would’ve introduced significant heat into the adjacent base material, causing the brass to wet out – i.e. no pretty beads.

It’s even trickier to get silver braze to lay nice fillet beads like this, but it can be done – provided you’re using a fine tip oxy-fuel flame. This is where Grade-3 Cadmium-free silver is advantageous, as it flows more like peanut butter, and the Cadmium-based brazing rod wets out real easily.

On the topic of Oxy-Fuel - I recently purchased a complete Oxy-Propane outfit. I was growing sick and tired of paying 80 cents per cubic foot for acetylene. A number 5 acetylene bottle is costing over 200 dollars to fill!

Acetylene currently costs $0.80 per cubic foot, and contains about 1470 BTU of energy per cubic foot. This equates to $52.45 per Therm of acetylene.

Propane currently costs $2.89 per gallon, and contains about 91,600 BTU of energy per gallon. This equates to $3.16 per Therm of propane.

Oxy-Propane is clearly a significant cost savings over Oxy-Acetylene. . .

 

[rkepler]

http://i797.photobucket.com/albums/yy259/dhem7/DSC03308.jpg

Take a look at this link. (Note: I did not build this part. I simply found the link on Google).

Pay particular attention to the high-quality fillet beads on this brazed joint. These were made with brass/bronze brazing rod, not silver. This joint was almost certainly made with an Oxy-Fuel torch, and not a fuel-air torch. It is much easier to get tight fillet beads like this using the intense focused heat of an Oxy-Fuel torch. A fuel-air torch would’ve introduced significant heat into the adjacent base material, causing the brass to wet out – i.e. no pretty beads.

I think that process is called "braze welding" and is distinct from "silver brazing", but there are overlaps between the processes. I expect that you use that form when the area between parts is low or you need a lot of strength (tubing joins in bike frames) and a braze that fills when the area is high or the required strength is low (pretty much everything else).

But you're right, you can't do that with an air-propane torch. I've done high fillet brazing (silicon bronze) with a TIG but never with a gas. After getting TIG in my shop it's my preferred point heat source, I don't think I've fired up the gas torch for anything but cutting for 5-6 years now.

Most of the silver brazing I do is like that below (a hand pump in my loco tank):

The bolster on the top of the cylinder, the arms attaching the handle above and the end pieces with the checks are all silver brazed. Lots of wetted surface and so minimum fillet.

I wonder what the original poster ended up doing?