Well, I at least don't feel bad now about not knowing the answer.
I appreciate the responses.
I should have been more specific. I build model steam engines. I do not have plans to build a boiler.
I have a boiler - which I may visit someday, but am quite happy running the machines on compressed air. I am fully aware of the potential hazard of live steam. I'm not afraid of it, nor am I afraid of my table saw. That does not mean I wouldn't be careful.
As far as solder -vs- brazing, I believe I understand the semantics. I was using terminology that I find common in nearly all the literature I read about live steam model building, it's nearly universally called "silver soldering", and that's what I meant.
John Hofstad-Parkhill said the following on 1/13/2006 4:36 PM:
And I feel you used the term correctly. I'm far from a weldor, but I get the impression that there's a serious difference between silver soldering and brazing. Silver solder will follow a heat source, and flows like water. I'm not convinced that brazing works similarly.
I've been in the machine trade since the late 50's, and have always heard the process referenced as "silver soldering".
As mentioned previously, there is a terminology problem here. Here in UK the term "soldering" refers to the process of joining metals with another metal having a lower melting point; in contrast to "welding" where metals are joined by melting them, and possibly adding a filler of the same melting point. We (meaning us in UK) recognise soft solders as those alloys containing lead/tin and hard solders as those that do not. Soft solders can be melted with a soldering iron, hard ones cannot. One particular type of hard solder is brass. It was once very commonly used to join iron or steel, and the process was known as brazing. Brazing is simply soldering with brass. The melting point of brass is high enough to make it unsuitable for joining copper or brass items, so another type of hard solder was developed that includes silver. This lowers the melting point so that it can be used to solder copper or brass. It is just about as strong as brass, but the silver content increases the cost considerably. Brazing and silver soldering are simply hard soldering; soldering with soft solders is known as soft soldering.
In USA it appears to be different in that all hard soldering is known as brazing, and all soft soldering is known as soldering. That's how I see it anyway.
You've been working with metal longer than I have, and I'm an amateur at metal while you are a pro. I'll bet I could learn a lot as an apprentice in your shop and I bet I'd enjoy doing so though I strongly doubt you'd tolerate my retired-ass appetite for work or hours.
I'll still brashly note what I've learned, or think I've learned, about the subject at hand.
Silversoldering is generally the same as silverbrazing, Harold -- which can be quite different from brazing with "brazing rod" like bronze or nickel-bronze. My experience is that the latter materials don't follow the heat worth a damn, though do not profess to be a pro. I seldom use them for that reason. I haven't done a bronze or nickle-bronze joint in half a decade. Pennies of cost per joint don't concern me a bit. I'm an amateur. I don't make my living working with metal.
Many if not most or all silverbrazing alloys do follow the heat source. I use that property routinely as a matter of technique. The follow is a matter of fluidity of the melted alloy and it's abilty to wet the parent metal in both brazing and soldering.
The low-temp materials are not regarded as silversolder but rather as silver-bearing solder May seem like a nit, but big difference. Sticking stuff together with silver-bearing solders at below 800 F is definitely soldering, but silver-brazing at temps above 800F is also often referred to as silversoldering -- and the materials used to do that are often referred to as silversolders.
Brazing and soldering are similar and differentiated from welding, in that the parent metal is never melted but is alloyed at lower temp with the joining material. The primary or only difference between brazing and soldering, as I understand it, is a matter of temperature: soldering is below 800F, brazing is above. I know of no basis for this apparently arbitrary boundary, but it seems to be accepted -- if confused by the common practice of referring to what is silverbrazing by this definition as silversoldering.
The remaining sanity in this mishmash is that soldering with lower-temp silver-bearing solders is very seldom regarded as silversoldering. It's just soldering with an alloy that contains a bit of silver.
Well I've built two with lead/tin solders. For low pressure and low temperature, there's nothing wrong with it. These were small Newcomen engines, fired by camping gaz burners.
All large firetube boilers have a "fusible plug" in them at the top of the firebox. This is a replaceable screw fitting with a hold drilled through it, filled with soft solder. If you let the water level drop to expose the plug, the heat melts the solder and it vents into the firebox. Rarely enough to affect the fire, but it's pretty noticeable and it lowers the pressure. Although there's no mechanical stress on this plug, it demnstrates that there's no inherent problem running soft solders at boiler temperatures.
You can also weld without melting the parent metal. Bronze welding uses exactly the same base materials and filler rod as brazing, but the technique is different. In soldering and brazing the overall workpiece is heated and capillary action causes the solder to flow into place. In welding (and bronze welding) the technique uses a more narrowly applied heat source. In bronze welding the cuprous filler rod is melted into place without melting the base metal (probably steel) and this gives a fillet with the typical "stack of dimes" look, not a smooth capillary fillet.
Harold you will find a great deal of smoke and not much light on this issue.
But the general consensus is, that the following terms are indeed interchangeable and mean exactly the same thing, from an adhesion standpoint:
Brazing
Hard soldering
Silver soldering
Braze welding
The mean the same thing, basically joining two similar or dis-similar metals using a filler that melts above 800 degrees, and does not melt the parent metal.
You will find a great many folks who claim that one of the other of the four terms above are indeed separate and distinct and describe different processes. If you do, then press them to tell you exactly what is different between, say, brazing and sliver soldering. Or braze welding and brazing. Or hard soldering and sliver soldering. Etc.
If the filler metal goes liquid below 800 degrees, it's soft soldering.
I've been using Solder-It for a few months, vastly superior to all the 4% and lower Silver content ones from Radio Shack etc.
Comes in a hypo-style tube, is 6%, I believe, has a great flux for bonding to steel or brass or Copper etc.
As easy to work with (or easier) for mending bits of clocks I work with, and many times stronger than normal Sn/Pb soft solders. Most hardware stores.
I won't comment on its safety for boilers, but I'm also concerned about using "hard" Silver solders for same, as the heat will certainly anneal brass or Cu - will this weaken it?
Perhaps not the industry then, but in many jewelry (silversmithing) courses offered to the public. Open up the riogrande catalog and what do you see? The classic fine-tip acetylene available air torch setups. Yes, there are also exotics like hydroxen electrolysis systems and probably older methods like your mouthpipe.
I know what I'm talking about well enough to have done quite a bit of it. And on workpieces much larger than any jewelry project too. I didn't say it was a good solution, I said it would just barely work - probably with the "easy" grade of solder only, too.
Sure, there are many methods of doing things. This may be advantageous for some applications, but it's not necesssarily the best generic method for silver soldering.
You know the thread is not about jewelry but about the options for making boilers. One of those is to use tools used by some silversmithing studios (even if not by you), and another might be to go get a the hottest bernzomatic from home depot. It all depends on if the flame needs to be concentrated or if it's okay to heat up a larger area.
Yes, if you want to bother with a source of compressed oxidizer. You've pointed out the possibility of a mouthpipe with is probably the simplest of those options if you are confident using one. I was talking about torches which entrain atmospheric air by themselves, simplifying things considerably though producing lower temperatures and less concentrated flames.
No, this is not a factor of the process name but a result of the property of the filler alloy used. A eutectic solder will tend to flow like water and follow the joint assuming things are hot enough. When the fit is designed for that it is wonderful. In contrast an alloy can be chosen which has a "plastic" temperature range between its solidus and liquidus and with practice this can be exploited to fill gaps. To some extent, if you get the whole thing above that range it should flow, but this is often hotter than you'd be comfortable or able to get the workpiece.
I think the confusion stems from traditional brazing alloys ("braze" - implication of brass or bronze type alloy) being those with plastic ranges rather than the high flow variety. Wheras a common reason (when color match is not a factor) of incurring the expense of a silver alloy is when a lower temperature, higher flow process was desired. Hence "brazing" tends to be associated with the use of plastic alloys and "silver soldering" with high flow ones, but they are basically the same process and there is no clear dividing line.
I can provide one difference. Silver solder does not build up in similar fashion to bronze brazing.. Who amongst us hasn't seen some serious "beads" of brass built up on cast iron? Try that with silver solder. Doesn't work, nor is there much benefit in doing so, anyway. . Joints for silver soldering are generally set up quite precisely, due in part to silver solder's limited ability to fill.
We generally get to bed well after 4:00 AM. When I was actively machining, my best hours were late night/ early morning.
-------snip lots of good stuff---
Yep! Hardly the same thing.
As I noted elsewhere, the one big difference between soldering and brazing (each "one and the same") is silver solder's limited ability to fill gaps and build beads. Don't know that it makes much difference in terminology, but it sure does when you're the guy trying to build a filet with silver solder, or bridge the gap when you screwed up on one of the components.
From all appearances, the terminology on this subject has been blurred for years. I have in my possession a large coil of 1/16" silver "solder", tag still intact, which clearly states that the product is "A low temperature brazing alloy". It's 54% silver, according to the tag. Bottom of the tag says United Wire & Supply Corp. Providence, 7, R.I. Providence
The only air-acetylene torches I've ever seen have been the Prest-O-lite sort. Now these are regarded as a fairly esoteric option locally, used only by a handful of people - they're certainly far from "mainstream" or "classic".
You can build up silver solder if you keep the temperature below the flow point. Even the handy and harmon ez-flow does that, when I'm flowing a joint I like to deposit a tiny ball of solder on the workpiece. As the heat builds the flux flows out, then the ball beads up and sticks to the work. More solder added at this point will look just like the brass welding rod you buy at the hardware store. Chunky.
Instead what I do is wait till the ball flows out, then the whole thing is up at temps and the joints runs nicely. It doesn't fill, but it sure does flow. The man that taught me silver soldering told stories about brazing gun barrels during ww2. They used to press in the liners, get the entire thing hot, and wipe the one end with the solder. The other end five feet away would show the ring of solder appear all around, if the joint was done right.
But the brass rod sold at the hardware store can be used to to flow out, but it has a wider eutectic range. It's easier to hold the part such that you can build up large beads like you mentioned. I've never found joints like that to be terribly strong so I prefer to keep on going and flow it out more.
And there are silver solders formulated to make a big fillet. You'll see references to them in British publications from time to time. They've been used for building custom bicycles and even for building some race car spaceframes.
I have some brand names here but I can't go looking for them.
"> Soldering a boiler with tin based solder, as someone suggested, ... yeah
Boooom, yer ass! Tell it to the folks at PM Research. I have 10 or 12 hours steaming time on a PMR boiler, riveted and sealed with 96% tin, 4% silver (silver bearing solder) and no "Boooom" so far. How long does Boooom take?
Cool! Thanks to you and Jim for enlightening me. . My limited experience with silver solder has never revealed the ability to build up a bead, or filet. . I've always flowed it out well. What little I did accomplish regards filets had a tendency to have serious shrinkage.
I hope you find what you need, Harold. BTW, in my experience, making a good fillet with ordinary silver braze requires someone who really knows what he's doing -- someone like Jim. I've had very little success with it. But I have gotten good fillets with bronze (brass) brazing rod, with a little help from my welding instructor.
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