The Absolute Last Final Word on Anhydrous Borax Flux

[ThomasPowers]

Now if you trust them, you can use them to calibrate a sketchy speedometer.  Back in high school a friend calibrated his VW Bug's speedometer and made a card to go behind it with accurate values using a stopwatch and the mileposts on the GSP in NJ.

[Frosty]

My what a grand idea, I'll put your name on the suggestion, it's just the kind of thing DOT would go for! While you're going to take your eyes and attention off the road let's do it for long enough to synchronize our thermometers!

I convinced myself of how accurate the radar signs are by watching the range their "reading" jumps as I drive past on cruise control, when I'm the only one within a half mile or so. The sign's margin of error isn't consistent, one near our place is maybe within 5mph but it's often a different 5mph. 

When they were first put up the margin of error was often more than 10 mph. 

If you use mile posts average over at least 10 miles, they're not terribly accurate. When I was new in the materials lab I got tagged to document potholes and mile posts. I spent a couple weeks driving slowly with a special camera taking pics every 52' while instruments recorded the vehicle's level. I manually clicked a pic of each milepost and logged the mileage from the little odometer/speedometer wheel clamped to the rear of the car. 

It would've been a fine way to spend a couple weeks but I had a 30 mph speed limit or the results were no good. I got some good scares from traffic traveling at realistic highway speeds.

Anyway, a 10 mile average and mile posts are reasonably accurate, a 100 mile average and you're within the allowable margin of error for the tests I was doing.

Oh yeah, the speedometer and odometers in our vehicles are LCD displays. 

Frosty The Lucky.

[JHCC]

You expect a wheel to turn the same number of times over any given distance on an Alaska road?

[ThomasPowers]

I've always wanted to hear a rendition of John Denver's "Take me home Country Roads"  sung while in an old pickup going over severe wash boarding with lots of dust to help the singers with that real country road sound!

[anvil]

Lol, considering where this post started and where it is now, I think that's the road taken here.

[ThomasPowers]

We do tend to take the road less travelled, get lost and wander a long while until the topic dies...

[Frosty]

Or washes out.

Frosty The Lucky.

[Samael]

I find this very interesting, because multiple books I've read on smithing now recommend simple clean dry sand as a flux.  I have borax but with the way things are right now (TRYING TO AVOID POLITICS) the local groceries and Wally Worlds are all bereft of borax.

One thing where I came from, which is casting, I was always advised to take Morton's light salt, which is a mix of potassium chloride and sodium chloride and melt them in the furnace, form an ingot, then grind it up to form the best flux for aluminum.  The reason being that the two compounds have different melting temps and thus bonding them together makes them melt together easier.  I assume this is simply the same process, then?  Melt the grocery/laundry grade borax in a crucible, form an ingot then go to pound town to form anhydrous?

[Steve Sells]

that is the general idea, tho I feel its a waste of time, I use it as is from the box with some sal amoniac and boric acid added, for the same reason as mixing the salts

[George N. M.]

Samael, I have used sand as a flux and it works but the problem is that it has a much higher melting point than borax or similar compounds.  Sand is usually quartz.  So, it doesn't protect the steel from oxygen as well as something that melts at a lower temp.

"By hammer and hand all arts do stand"

[Frosty]

I buy powdered welding, brazing, etc. flux at the local welding supply, Peterson's blue. It is anhydrous borax, boric acid and something blue. I hear prices of "forge welding fluxes" have come way down but Peterson's on the shelf in Wasilla Alaska was $26 and change last can I bought.

1lb/pint lasts a long time if you don't try burying a joint in flux when you weld. 

I still have most of a 3lb. coffee can of 20 mule Borax and boric acid I've had maybe 20 years. It works fine but the Peterson's works better.

Frosty The Lucky.

[TWISTEDWILLOW]

X2 on the Peterson’s blue, I followed Frostys tip and I ordered some of that stuff from Amazon and have used it to weld mild steel so far with success! 

[Samael]

3 hours ago, George N. M. said:

Samael, I have used sand as a flux and it works but the problem is that it has a much higher melting point than borax or similar compounds. 

Thank you for this, for some dumb reason I hadn't even considered the material of sand and its melting point vs. borax.  I will be welding in a gas forge when I weld, so it's something to take into consideration for sure.  I know Frosty preaches a lot about how borax will cut through ceramic blanket like water through cotton candy, so I think I will use a coat of rigidizer, some satanite, then KOL and then some ITC for a heat surface.  Overkill?  Should I just use KOL or Satanite to resist the flux instead?

[Samael]

1 hour ago, Steve Sells said:

that is the general idea, tho I feel its a waste of time, I use it as is from the box with some sal amoniac and boric acid added, for the same reason as mixing the salts

Does boric acid react with the hydrous boride to remove the hydrogen in free solution?  This makes perfect sense when dealing with an acid.  What is your method?  Do you heat first then apply the flux and acid or??  It seems to me on one level it would be simpler to synth a batch like I do when casting, which is cast two 100 troy oz ingots with morton's light then smash em up in my giant Costco mortar and pestle.

[JHCC]

3 hours ago, Samael said:

multiple books I've read on smithing now recommend simple clean dry sand as a flux.

Samael, a lot of older texts recommend sand as a flux, but a lot of those date from when wrought iron was more common. Since WI has a comparatively high silica content, it's largely self-fluxing, and the sand is a bit of extra insurance. I haven't seen any recent books that recommend sand over borax; do you have examples?

3 hours ago, George N. M. said:

Samael, I have used sand as a flux and it works but the problem is that it has a much higher melting point than borax or similar compounds.  Sand is usually quartz.  So, it doesn't protect the steel from oxygen as well as something that melts at a lower temp.

The melting point of silicon dioxide (the main component of silica sand) is 3,110°F / 1,710°C, which is actually higher than the melting point of steel (2500-2800°F / 1371-1540°C, depending on alloy content). Whatever it is that the sand is doing to act as a flux, it's not actually melting.

[Samael]

I should've phrased that better, I didn't mean to say "now" as in the most recent books out.  I am going through a few books at once so I don't recall off the top of my head exactly which one, but I distinctly remember reading to use sand as a flux when forge welding and thinking "huh, sand?"

[JHCC]

Gotcha. 

The big advantage that borax has over sand is twofold. First, it actually does melt and cover the metal, forming a barrier against oxidation. Second, it dissolves any scale on the surface and flushes it out of the weld as the metal pieces are forced together.

[ThomasPowers]

Sand was a fairly passive flux for Wrought Iron that didn't need much flux to start with,  powdered glass was another. Passive is mainly a cover to prevent oxidation.

Borax is a more active flux; it will attack oxidation present.  Some add Boric Acid, (I use Roach Pruf; found an old bottle that was 100% boric acid at the fleamarket for a couple of USDollars...; as I use it 1:4 with borax it will last me YEARS!)

Even more active flux components are out there; JPH's "steel glue" uses more components.  Note that fluxes used to attack oxides on stainless steels evolve TOXIC FUMES!

[Frosty]

Silicates are soluble in caustics. Ceramic blanket is a silica based refractory and borax is a strong base, at welding temp it's very caustic and will dissolve most refractories.

Don't get crazy, rigidize the blanket, cover with KOL and as a final layer of armor a good kiln wash. Not ITC-100, there are better, Plistex being one of them and available in small quantities from the Iforge store under refractories and forge supplies.

Frosty The Lucky.