It seems like everyone goes to a lot of trouble to line their welding forges with stuff that will resist the corrosive action of caustic borax flux. Is there a commercially available flux that won't eat through ceramic fiber insulation blankets ?  Maybe a guy could pay a little more for commercial flux, but his forge would last longer and be safer ?

This from Wikipedia:

Early examples of flux used different combinations and various amounts of iron fillings, borax, sal ammoniac, balsam of copaiba, cyanide of potash, and soda phosphate. The 1920 edition of Scientific American book of facts and formulae indicates a frequently offered trade secret as using copperas, saltpeter, common salt, black oxide of manganese, prussiate of potash, and "nice welding sand" (silicate).

Would one of these formulas work just as well, and not eat through the forge lining ? Is all that stuff safe to breathe ?    Is borax safe to breathe ?

Edited August 12, 201510 yr by potatoeman

Most people seem to report that Satanite , which is available from suppliers listed in the knife forum, is resistive.  I found it works ok for me but I still need to be careful about how much borax I apply.  Boron and Boric Acid are potentially poisonous.  However it is dust rather than vapor you want to watch out for.  A mild boric acid solution was used for eye wash for years. Twenty mule team borax has a lot of water chemically bound to it.  Evaporating that water cools the iron so some people prefer to use pretreated borax welding compounds to avoid the mess and cooling.  Twenty Mule team is cheap.  For general work like forging welds on fire place pokers I've always used twenty mule team.  If you are doing Knife work that is a whole different thing and you should follow the recommendations in their stickies.

Didn't Japanese use rice straw ash.  English dont use flux.  Flux by nature is corrosive as eating is its job

The flux has two jobs; eat oxide off the steel and prevent new oxide from forming by shielding the piece from oxygen. If you start with a clean workpiece, maybe you only need an oxygen barrier to protect the steel while it heats up ? English smiths, apparently, don't use any flux at all ? 

With a real good deep bed of coke I've found it possible to do a flux free weld in mild steel.  I've read that clean white sand was the only flux used to weld wrought Iron.  However, I'm not sure that gas forges are compatible with forge welding.   I've never tried a flux free weld in a gas forge.

Didn't Japanese use rice straw ash.  English dont use flux.  Flux by nature is corrosive as eating is its job

my understandin is no. From what I've read and understand they don't use flux. The straw ash paper and clay wrap is to protect from decarburization while working at welding heat. The iron they used still had impurities they drove out durin the folding and welding process. Again this is my understanding but others might read the same info and see somethin different.

With a real good deep bed of coke I've found it possible to do a flux free weld in mild steel.  I've read that clean white sand was the only flux used to weld wrought Iron.  However, I'm not sure that gas forges are compatible with forge welding.   I've never tried a flux free weld in a gas forge.

I intended to say that Gas forges with out flux or with some air exclusion device as in can welding  may not be compatible with fluxless welding.

Many old fluxes are either to dangerus to work with or, melt at to high a temp to protect the steel from forming scale (infact you may make sparklers of tool steel waiting for sand to melt) many old books on forging tools recomended charcoal as it was cleaner and "ash is a flux" ash is not only made of caustic compounds but as many "woody" plants get there structure from silicats in theire tissue (hardwoods praduce more ash than soft woods for this reason) 

 

Edited August 12, 201510 yr by Charles R. Stevens

Firstly, my understanding would be "if it contains cyanide " there is a strong possibility that it might not be good for you RDA probably Nil. Secondly guys like John Emmerling an American, with a gas forge does beautiful flux less Damascus. He has shown me how he does it and it just needs a longer 'soak' . Thanks John!

Firstly, my understanding would be "if it contains cyanide " there is a strong possibility that it might not be good for you RDA probably Nil. Secondly guys like John Emmerling an American, with a gas forge does beautiful flux less Damascus. He has shown me how he does it and it just needs a longer 'soak' . Thanks John!

I glad to know that it is possible  to do fluxless welding in a gas forge.  Would you care to share what you know about the conditions?  The only fluxless pattern welding in a gas forge that I've been privileged to see has been what is some times called can welding.   That is a mild steel container is constructed around the billet stack and welded closed.  It is then soaked in the forge until the smith knows that the contents are at welding temperature.  

I find it much easier to do ornamental welding in a solid fuel (coked coal) fire than in a gas forge btw.

I read somewhere where guys have used a layer of the black casting sand on the bottom of the forge. The flux that drips onto it is easily removed as it sits on the sand, and does not contact the inside of the forge.

I glad to know that it is possible  to do fluxless welding in a gas forge.  Would you care to share what you know about the conditions?  The only fluxless pattern welding in a gas forge that I've been privileged to see has been what is some times called can welding.   That is a mild steel container is constructed around the billet stack and welded closed.  It is then soaked in the forge until the smith knows that the contents are at welding temperature.  

I find it much easier to do ornamental welding in a solid fuel (coked coal) fire than in a gas forge btw.

John has done a thread on flux less Damascus, a short synopsis, sorry  I could not post a link. 

Edited August 13, 201510 yr by ianinsa

I got to watch Tom Ferry weld up a stack of Damascus in a rather high tech propane forge with a thermocouple rigged to a solenoid that pulsed the feed and could keep the forge within a few degrees of what you set it at.  I think I posted about it elsewhere, let me see if I can find it.

Won't let me edit 3 minutes later, odd.  Anyway here it is:

http://www.iforgeiron.com/topic/40852-uniformity-at-low-temps/#comment-416838

The idea of adding sand is good. I've been toying with a forge design where the floor and walls of the forge are shaped to let the melted flux that drips off to drain out the front of the forge, rather than just puddling inside. 

interesting Chinobi .   Can welding is simpler  but  a muffle is an excellent choice  for professional work.

I just put a cookie tray (actually a thicker stainless custom made tray but you get the idea) in the bottom of my gas forge when oozing flux is a concern.  When it's cold flip it upside down and tap with a hammer and some the glassy stuff chips off and falls away.  

some folks fill the tray with a layer of cheap clay kitty litter and then knock that out as needed.

I use insertable plates made of a highly flux resistant castable.

Also, rice ash is used by the smiths as a flux and protective barrier. Ash analysis has shown rice straw ash to be in the 80-90 percentile as silica. Also after a number of folds, or say about 6-7 out of 13-15 folds, there is little slags left enough to self flux the billet, so other means such as the ash is necessary to keep the welds clean.

Also, in a highly rich atmosphere, fluxless welding is possible.

As far as I understand, Japanese smiths use charcoal and a lot of it. There probably is hardly any oxygen left in the area where they put the billet. Rice straw contains much silica so it may form a slag if hot enough but looking at the clips I get the impression that there is a lot of carbon left that can act as oxygen scavenger.

Göte