Forge welding

[maddog]

Stay Silv is a silver solder. The flux probably is mostly borax. It might work for forge welding - lots of stuff does but I dunno.

There are basically three kinds of soldering brazing processes:

Soft solder: made with lead or tin. Melts at about 600deg. Used for electrical & plumbing work. Can be done with a soldering iron or fuel air torch


Sliver solder: Made of silver. Melts at about 1100deg. Used for jewelry, fine work, AC & vacuum lines and other stuff. Needs fuel air or oxy fuel torch. Sta Silv is designed for AC plumbing. I have some but I dont have the flux so I use 20 Mule Team borax

Brazing: Uses brass brazing rod. Melts at about 1400 deg. Used for joining steel parts and often cast iron which is hard to weld. needs oxy fuel torch.

The temps are approx - I dont recall exactly. These are all very similar processes in that the metal being joined is not melted but held together by a layer of metal which melts at a lower temp than the base metal. They all require a flux to wash the oxides off the surface of the joint.

Strictly speaking only the brass process is called "brazing" the others being called soldering. Seems a bit arbitrary to me since the only difference is the metal being used and the temp but there it is.

Brazing flux is mostly borax with a couple of other cleaining agents added

You can find this stuff in welding supply stores , automotive parts stores and some hardware stores. It sells for about $16/lb. IMO it works a little nicer than ordinairy laundry borax which costs $1/lb for forge welding . I have brazed and silver soldered with 20 mule team borax which you can find on the laundry aisles of many supermarkets.

[MetalMuncher]

Thanks for all the tips guys, BIG help. I should be able to get a weld now.

[Woody]

When using commercially prepared flux get a MSDS and READ IT! Many of these products contain fluorite which when heated in the forge gives off Hydrogen Fluoride Gas which is extremely toxic, those are big words for DEADLY if you breathe enough of it. When a forge weld fails to make, it is usually not flux that is the problem. Most forge welds fail for one of the following reasons reasons, either it wasn't hot enough or you hit it to hard or the metal wasn't clean. Try bringing it to welding heat and squeezing it together in a vise.

[Avadon]

Thank you maddog and woody. I'm going to try Airgas and see if they have what is in the picture above. Airgas is really the only thing "welding" on capecod, so if they don't have it or can't order it then i'll have to fish it down from the internet somewhere. I'll definitely check out the MSDS. Most of the welding products I use I know are full of carcinogens, but since i've been welding forever I think they have actually mummified my body lol

[Rich Hale]

Twenty mule team borax is a good flux and is found in the laundry soap part of grocery stores

[evfreek]

I am starting to wonder why fluorite is so dangerous. There must be a good reason. I heard that 6011 welding rods contain a small amount of potassium fluoride to help stabilize the arc. They smell terrible, and it made sense that the irritating nature of their smoke was partially due to the fluoride. Well, a quick web search shows that this is not quite right. In fact 7018's, which smell much better when they are burning, contain about 15-30% fluorite based on the MSDS's. This encouraged me to search around a little more. Apparently, the main irritating constituent of 7018 smoke is an alkali calcium fluoride fume. There is some risk to the lungs, but the main culprits, with lower TLV's, are haxavalent chromium, nickel and manganese. In fact, many welding fume analyses do not contain fluoride percentages, instead being restricted to metal fractions. According to many studies, the fluorite fume is not all that harmful, although it has an OSHA and ACGIH TLV of 2.5 mg/m3. Hydrogen fluoride is much nastier, and I know more people who have been laid low by this chemical. It is toxic at about 3 ppm. Oddly enough, the two numbers above are nearly identical. Maybe the fluorite is just as dangerous, but since it was "baked off" with calcium carbonate, its impact is in a less dangerous alkali form. So, why is forge flux fluorite so much more dangerous????!?!???! One reason is the alkalinity of the welding fume. Another may be the quantity, but forge fluxes tend to carry a much lower percentage of fluorite than welding rod flux. Forges are hot, but SMAW arcs are much hotter (even though they're smaller). Fluorite is stable up to pretty high temperatures, and does not decompose into hydrogen fluoride, unless there is hydrogen or water present. It can, according to one source, out-gas fluorine, according to ceramicists. A lot of people inhale a lot of welding fume, especially those doing unprotected confined space work, and the main risk appears to be siderosis due to magnetite deposition in lung tissues, as well as the aforementioned metallic carcinogenicity risk.

Whew, that was kind of long winded. Briefly, why is fluorite so dangerous in forge welding flux when it is much less so in stick welding flux for basic electrodes?

[maddog]

Im inclined to agree. One 6011 is widely used by prof welders and amateurs. One doesnt hear of poisonings or injuries. I bought 1lb of flourspar from a pottery supply house to add to my forge welding borax. The bag didnt come with any special warnings. I can smell it when I use it but have not suffered any ill effects. Nor is it a toxin that accumulates in the body allowing sub toxic doses to build up to dangerous levels.

I think its a bit of hyperbole that gets passed around and repeated. There are common chemicals that are lethal in high enough concentrations but harmless at low levels. Hard boiled eggs sewage, cabbage and human flatulence all contain hydrogen sulphide, which is more lethal than cyanide yet we survive those. Cyanide too occurs naturally in almonds and mangos