What Kind of flux to use for Forge welding

[RaiderJameson]

HI. i am about to get started on forge welding and i was wondering what kind of flux i should use. i found some on amazon but it is all for non carbon metals. Does anybody have any suggestions.

 

[weo]

The standard answer would be anhydrous borax, but regular borax works as well.

Be aware that flux will destroy the floor of your forge after a while. A lot of folks eventually progress to fluxless welding.

Historically, flux was used both to prevent oxidation of the welding surfaces as well as to help clean out impurities. Nowadays, with proper surface prep, it's mainly there to prevent oxidation of the welding surfaces (which will prevent welding). If you have a properly tuned forge with a reducing flame, then you don't need the flux to prevent oxidation.

 

[RaiderJameson]

The standard answer would be anhydrous borax, but regular borax works as well.

Be aware that flux will destroy the floor of your forge after a while. A lot of folks eventually progress to fluxless welding.

Historically, flux was used both to prevent oxidation of the welding surfaces as well as to help clean out impurities. Nowadays, with proper surface prep, it's mainly there to prevent oxidation of the welding surfaces (which will prevent welding). If you have a properly tuned forge with a reducing flame, then you don't need the flux to prevent oxidation.

Thanks. Are there any brands you would recommend?

 

[weo]

any brands you would recommend

If you're asking about anhydrous borax, no. But you can make your own by melting/boiling regular borax at just under forging temps, let cool, then crush into a powder/granules.
When I used flux it was either generic borax, or the mule team brand. The only real difference between anhydrous borax and regular borax is that the regular stuff will boil and bubble a lot more as you sprinkle it on.

 

[RaiderJameson]

If you're asking about anhydrous borax, no. But you can make your own by melting/boiling regular borax at just under forging temps, let cool, then crush into a powder/granules.
When I used flux it was either generic borax, or the mule team brand. The only real difference between anhydrous borax and regular borax is that the regular stuff will boil and bubble a lot more as you sprinkle it on.

thanks very much. Would i put it into water to boil or will it liquefy on its own.

 

[Alex Topfer]

it melts on the hot steel. i have heard of people dissolving it in water so they can soak the entire piece in the water to get flux into all the gaps, when you heat it the water evaporates and leaves the borax.

 

[DevinT]

K&G sells a flux that is mostly anhydrous borax mixed with some boric acid, it’s a good one. It was developed by Bill Fiorini (rip) who was one of the pioneers of pattern welded steel who’s influence I still see today.

Hoss

 

[RaiderJameson]

Thanks Very much Guys. I will Try it and let you know how it goes.

 

[Stacy E. Apelt - Bladesmith]

I use 90-95%anhydrous borax, 4-6% boric acid, and 1-4% powdered charcoal. The charcoal helps remove oxides.
The ratio isn't all that critical, so start with a pound of anhydrous borax, add an ounce or two of boric acid, and then add half an ounce to an ounce of charcoal. All are available from Amazon or most any online place. You don't need high grade chemicals, so use the cheapest available. You could crush up your own powdered charcoal from hardwood charcoal (not briquettes).
Mix them up well in a plastic bucket and store in a tightly closed jug.

A good trick for applying flux is to get a metal seasoning shaker like they use for BBQ grilling. fill it about half full and use it to shake on the flux. You want what is called a dredge shaker (not salt and pepper shakers). Two of them with plastic covers runs $10 on eBay. Search using,

"Dozenegg Stainless Steel Versatile Dredge Shaker, Set of 2"​

 

[RaiderJameson]

Very Cool Thanks so much Yall.

 

[Ken H>]

Stacy: Those do look good. I think I'll order the $10 pair. Looking more I found this set on Amazon (search for item B077995L95) which is only $7.50 for a 5 oz pair and have larger holes in the top. Will those larger holes be good? OR, are the smaller holes on the item you mentioned better?

 

[Stacy E. Apelt - Bladesmith]

It doesn't matter as long as the flux shakes out. Most folks put on WAY too much flux. An ounce of flux does not make the billet weld any better than 1/4 ounce of flux. In fact, too much flux can be a problem (besides the red-hot molten flux shooting all over the shop).

 

[Stacy E. Apelt - Bladesmith]

I took a look at those shakers you saw, and they are half the capacity and don't have the plastic sealing covers. The covers are important because anhydrous borax is hydroscopic.
When done with a day's forge welding, dump the shakers back into the storage container and close up tight.

A wide mouth gallon size mayonnaise or similar plastic jar is perfect for mixing and storing your flux. Any restaurant, school/college cafeteria, or commercial cooking place has them and will gladly give you an empty.

 

[Ken H>]

Yep, I saw they didn't have a cover, but wasn't sure if the plastic cover would really seal that good or not. My idea with the half size (5 oz) was to store one in a wide mount pint jar (what I have on hand) that should seal good. Or perhaps for storage remove lid, cover with thin plastic, screw lid on which should seal container nicely.

5 oz should be more than enough for a forging session - or 3. I only use flux until weld is set. Doesn't take much flux.

 

[Stacy E. Apelt - Bladesmith]

It will work that way. But it is best to dump the flux back in the bulk container at the end of the day. At a minimum, store teh shaker in a Zip-lock freezer bag.

 

[Atlas Knife Company]

Haven't used flux in years. Try just skipping the flux

 

[Stacy E. Apelt - Bladesmith]

Charles brings up a valid point.
By tig/mig-ing up all the seams on the entire billet while clamped tightly you can dry-weld. Basically, the billet is like a canister. Once welded solid, grind the sides clean od the weld material.

Or use hydrocarbon fluxing.
Weld the billet up as normal and soak in a can of kerosene or other hydrocarbon (Brake cleaner, etc.)
When ready to do the weld, take out and let the excess drip off back into the container and put the billet in the forge. Cover the fluxing container with a tight lid to prevent fires.
The flux will burn off leaving carbon which attaches to oxygen and leaves the surface ready to weld cleanly. The trick is that once the billet reaches welding temp, do not let it drop below orange color. Hammer/press - brush off quickly - stick back in the forge - brush off & hammer/press - back in the forge - continue until the billet is solid.

 

[Super_Alloy_Alan]

it melts on the hot steel. i have heard of people dissolving it in water so they can soak the entire piece in the water to get flux into all the gaps, when you heat it the water evaporates and leaves the borax.

That would not happen I have no idea who told you this but that just..is NOT how science works mate. If you are talking about dissolution in a solution and then heating...ya. No. salt works like that. this is Sodium Tetraborate. Not..im not going to get into the chemistry unless someone asks me to.

Charles brings up a valid point.
By tig/mig-ing up all the seams on the entire billet while clamped tightly you can dry-weld. Basically, the billet is like a canister. Once welded solid, grind the sides clean od the weld material.

Or use hydrocarbon fluxing.
Weld the billet up as normal and soak in a can of kerosene or other hydrocarbon (Brake cleaner, etc.)
When ready to do the weld, take out and let the excess drip off back into the container and put the billet in the forge. Cover the fluxing container with a tight lid to prevent fires.
The flux will burn off leaving carbon which attaches to oxygen and leaves the surface ready to weld cleanly. The trick is that once the billet reaches welding temp, do not let it drop below orange color. Hammer/press - brush off quickly - stick back in the forge - brush off & hammer/press - back in the forge - continue until the billet is solid.

Do this!

 

[Ken H>]

What Stacy says - Although I only weld up seams all the way around on San Mai. With a stack of 15 to 20 strips of 1/8" it sure would take a LOT of welding to get the seams solid all the way around. Another option is to weld an 1/8" flat on the sides and end, in effect making a canister.

Kerosene works good. There are times when I might prepare a couple of billets, weld them up with strips of weld, weld handle on and put to soak in kerosene overnight. Next day do the welding. Since I'm not an expert at all on this stuff I'll still sprinkle a bit of borax on the edges as billet gets to a dull red, then soak until it's at welding heat, then to the press.

 

[fitzo]

That would not happen I have no idea who told you this but that just..is NOT how science works mate. If you are talking about dissolution in a solution and then heating...ya. No. salt works like that. this is Sodium Tetraborate. Not..im not going to get into the chemistry unless someone asks me to. <snip>

I'd be interested in hearing your explanation of the chemistry and how science works. Thanks!