beginner's questions about soldering

Hello,
I have some basic questions about soldering.
If I want to make a small art project with common metals (steel, copper, aluminum, etc.), what do I need to know about
soldering?
About 25 years ago, I learned a very few basics about soldering electronics. One was that you use different solders for plumbing, electronics, and jewelry. But which kind do you use for art? (Also, it's likely the technology and materials have changed since then.)
Please respond to the newsgroup and not to my email.
Thank you very much,
Ted Shoemaker
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snipped-for-privacy@yahoo.com (Ted Shoemaker) wrote:

Well, first thing is that you don't solder steel or aluminum. Period. You can gob on wads of solder and stick steel or aluminum pieces together the way you'd stick, for instance, chunks of wood together using a handful of clay - They'll be joined, yes, but don't count on *ANYTHING* resembling structural strength, and you'll never get anything even remotely like a proper solder joint out of the attempt. The metals just aren't compatible (The solder simply won't "wet" them, so it can't "grab on" the way you're probaby used to from electronics work) so it's one of those "ain't gonna happen" things.
Until relatively recently, when lead-bearing solder was either outright banned, or severely restricted for use in potable water plumbing work, the main difference between the solders used for plumbing and electronics work has been the flux - Plumbing uses acid flux, electronics uses rosin. This is due to the differing ways that plumbing and electronics tolerate (or fail to tolerate...) the inevitable corrosion from acid left behind by anything other than an *ABSOLUTELY PERFECT* cleanup job. Electronic gear doesn't like acid traces on the board, and generally dies in fairly short order if acid flux is used. This is partly due to the comparatively thin layers of metal being worked with, and partly due to electrolytic action that starts happening when the device is powered up. Plumbing, on the other hand, is heavier gauge metal, usually homogenous (only joints are copper-copper, with no possibility of copper-iron, copper-zinc, or similarly heterogenous joints) and not subject to carrying current, so it's much more forgiving.
Jewelry is *USUALLY* done with silver solder, which, as the name implies, usually means that the solder has at least some silver content to it. It's a harder solder (in terms of the comparative placements each would have on the Moh's hardness scale), and often, if not usually, requires a higher heat to work with than tin/lead soldering; You can solder using tin/lead solder with, depending on the exact alloy, anything from a kitchen match to a propane torch, while silver solder often requires a MAPP gas torch to get into the heat range needed to make it flow properly, and for the *REALLY* hard silver-solder alloys, might even require a small oxy-acetylene rig.
As far as "art" soldering... <shrug> Never encountered the concept, but at a guess, I'd say that if it involves steel, it's probably actually brazing (which is BASICALLY soldering with brass or bronze solder, rather than tin/lead or tin/silver), and if it involves aluminum, it's more likely TIG welding.
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Don Bruder wrote:

Wrong, steel is easy to solder and to silver solder. For example, shotgun barrel ribs are sweated on with lead/tin.
You got the rest of it pretty much right though.
Regards, Hoyt McKagen
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Hmmm... Apparently, based on the multiple "Hey, dummy, you can too solder steel!" messages, all my attempts at soldering steel (stainless or otherwise) have been done wrong, since I've *NEVER*, in dozens of atempts, had even the slightest success in getting the solder to "wet" the steel. I can make neat looking little balls of solder that are stuck to the steel by the remains of whatever flux I've tried using (everything from rosin to acid to one fellow's suggestion years ago, a mixture of borax, sugar, and vaseline), and anything else that even KINDA sounded reasonable and not instantly toxic), but no matter what I've tried, I can't make a joint that has anything that could be mistaken for a structural strength above absolutely nil. Most of my attempts haven't even been able to support their own weight for more than a second before the joint gives, and close exmination of the joint always reveals the classic "cold solder" problem quite clearly.
So it would seem I've been going about it wrong. Maybe some day, when I have another situation that needs something soldered to steel, I'll try to chase down a "proper" method, but for right now, trying to educate me on how to do it would be a waste of effort for both of us, since I haven't the interest to sit down and learn it. (zero practical motivation for doing so at this time - ask me again next month when I figure out that soldering would be the best way to deal with some new project involving steel that's caught my attention! :) )
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I can usually get a good joint on galvy with just rosin solder. Sand off any oxides then tin. Make sure not to overheat the joint as the zinc layer is dissolved by the tin and leaves a weird gray or black surface that's impossible to tin. For bare steel, file or sand down to shiny metal and go for it. Maybe a bit more heat than usually needed (bright copper being usual) to get the rosin going good.
I've never got anything to stick to SS, but then I don't have much SS nor do I have a reasonable acid flux. Heck.. I don't have _any_ acid flux right now.
Tim
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I never have had any luck soldering stainless with regular lead / tin solder either. Maybe the tin / 5% silver solders will do some stainless steels, but I am confident that there are some stainless steels that either take an exotic solder or can't be done with low temp solder.
Dan

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While soft soldering stainless is a bit tougher, because of the extremely low thermal conductivity, it can easily be done with the correct active flux. I use "Duntons" liquid stainless flux, which works well except the mist and fumes that come off are a bit corrosive.
I've found that the key to doing a good stainless joint is to carefully pre-tin the part. This really takes less heat than is imagined - the stainless has such low thermal conductivity that even large thick parts can be surface tinned with a small iron or gun. The part will heat locally and the solder will wet the surface nicely.
One common mistake is using too much heat, and overheating the flux, and burning it off before the solder has a chance to wet down. Also using rosin cored solder is not the best, as the rosin for this application is not really a flux, but a contaminant that the acid flux has to overcome before it works properly.
Once the stainless part is tinned properly, once, it can be sweated without the use of stainless flux - ZnCl or rosin flux can be used to attach a tinned stainless part to copper brass or steel.
Because the Silver-Tin solder (eutectic 151 is my favorite) is so much stronger, and does not contain any rosin, and has a low vapor pressure (no lead) it is my favorite for doing the odd vacuum system job where stainless parts have to be soft soldered.
Jim
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I think that most of the people here who have had difficulties soldering one material or another are looking at it from the wrong angle. It isn't the solder. It's the surface preparation and fluxing.
Ed Huntress
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When you get around to it, ask the people at Kester solder. They'll give you complete details on soldering both plain carbon steels and stainless. It helps to watch someone do it, because you may be burning the flux off or trying to do it with insufficient heat.
Ed Huntress
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Stainless steel type 304 and 316can be silver soldeereed using a high-temperature flux, but beware - the silver solders I have used contain some zinc, which embrittles stainless at red heat, so to make thin stainless bits join together, I had to work quickly and quench quickly, before the zinc could work its way in between the steel crystals. Any interest?
-G.H.Ireland
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igor
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Not sure about soft solder but in th UK you can buy a special silver solder flux for stainless which is much more agressive the the normal stuff for steel. My neighbour has used some and I have seen the results and a sectioned test piece. All worked extremely well.
Don Bruder wrote:

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So why not ? Sounds like you're using the wrong flux.
Baker's Fluid / killed spirits / zinc hydrochloride (take hydrochloric acid - dissolve an excess of zinc in it) works fine as a flux for steel. That and either a gas heated iron. or a large electric one.
Strip any plating off first too.
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Don Bruder wrote:

I've soldered thin stainless many, many times with great success. You have to clean it and give it a 'tooth' with sandpaper, tin it with good acid flux then make the joint. Thin sheet steel should work just as well.
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On Sat, 13 Dec 2003 20:36:46 GMT, Don Bruder put forth the notion that...

There's a rod for aluminum to aluminum now that works pretty well, but it won't stick it to any other metal. It's more like brazing than soldering, but you can do it with propane or MAPP gas.
--
Checkmate
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From other threads regarding the joining of aluminium with these special rods you can buy, they are apparently very high in zinc. It would be interesting to see if you could join aluminium to steel or galvanised steel with them.
Checkmate wrote:

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One day I was trying to melt a small soup can of zinc on the stove... An hour later it was just barely melted and I gave up, poured off what I could and busted out the rest. Problem is... it was stuck. Had to peel the can off the zinc block! Basically it soldered itself on. Any steel-zinc joint will be similarly weak, just like any other soft- soldered joint. I've tried said aluminum brazing before, seems to work. I bet if you tinned the aluminum and steel with the rod, then stuck them together (with a bit of flux of course) it'd work. The weak point would be the zinc/steel joint.
From my metal melting experience I don't see why you wouldn't be able to braze steel with aluminum, only problem is flux.
Tim
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The rod is called either alumaloy or alumiweld. They make versions for steel and cast. I beleive the alumaloy will join aluminum to steel but I am not positive. Do a search on google for alumaloy or alumiweld and you can read all about them. One note is that most outlets for these products are franchised, I think the product was turned over to some direct marketers at some point and they are marketing it through a million individuals so check the pricing. I have found different places selling it for wildly different prices. Some places you can get almost twice as much for the same price.
Mark
David Billington wrote:

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I have an entire book, published by Alcoa some years ago, about soldering aluminum. This is ordinary soft solder they were talking about, although there are some alloys that make it easier.
The idea that you can't use ordinary soft solder on aluminum is a mistake. It's been done in industry since at least the 1920s.
Ed Huntress
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<snip>
You can achieve a reasonable solder joint to aluminium. Very hot iron, sandpapered while oily, solder through the oil. Not especially easy.
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snipped-for-privacy@sonic.net says...

Solder will work just fine on steel. Cleanliness is important, and a more active flux than you might use for copper may be helpful, but regular old No-Korode will work with careful prep. The limiting factor for typical lead/tin solder will be the solder itself, not the bond.
It's also possible, but not straighforward, to solder aluminum with Pb/Sn solder. One trick mentioned often on this NG is to clean and solder under a film of oil to inhibit the rapid formation of the oxide layer.

Nokorode, perhaps the most widely used plumber's flux for at least 50 years is zinc chloride and ammonium chloride in petrolatum (Vaseline). Not an acid flux, but not something you'd use on a circuit board either.
For the OP, the silver bearing soft soft solders -e.g., All State 430, Harris Stay Brite (sp?)- are good for decorative work. They are substantially stronger than lead/tin and stay shiny with time. Since they do not flow as well as lead/tin they do require better heat control to get good results. Also more expensive.
Choice of flux for these solders is similar to lead/tin. Nokorode is fine for most uses, but there are acid fluxes that allow soldering stainless steel and other difficult materials. The acid fluxes (All State Duzall is one) are trickier to use as they are prone to burning when overheated, especially a problem with a torch.
Ned Simmons
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