Using Boric Acid and Iron wire to reduce scale when tempering/heat treating

dbb-the-bruce

Dave
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I'm very interested in being able to make my own high quality bits, cutters etc. I've got a couple of tasks that are well suited for making a custom D-bit, one I need to make a lot of precise diameter ~ 0.060 and ~0.03125 deep flat bottom holes. Another I need for a number of small pitch racks, and finally a broach type tool for inside splines that are ~0.060 sq. - spaced evenly on an inside hole. (I'll probably ask for tips on tool geometry, but that's not this question!)

I watched the ClickSpring video on making a simple D-Bit (the guy does awesome videos!).
In the video he uses soft iron wire and boric acid paste to reduce scale when tempering.

I've managed to find 99% pure boric acid power.

My question is about the "soft iron wire". I've found "black annealed wire" 16 gage for about $10 at Home Depot. It seems to be the right stuff. However it doesn't say if it's steel or iron. With a little more googling, I've found both "black iron wire" and "black steel wire".

My question is, for reducing scale, do I have to be absolutely certain that I'm using iron vs. steel? what's the chance that the wire I bought is iron or steel? Is there an easy way to tell?

I'm not up on the chemistry involved, but my understanding is that the wire and the boric acid are "greedy" rob any air that gets near the part being treated of either/or carbon & oxygen. Hence less scale because the elements to create the scale are less available.

A second question is: In the video he makes a paste and says he used denatured alcohol but his jar of paste has "mineral spirits". I'm guessing that the what liquid you use to make the paste probably makes very little difference as long as it doesn't react - it's all going to evaporate very quickly once you start heating it up.

I've got a muffle / oven for heat treating so this should be pretty easy to get done.
Thanks in advance for any help!

-Dave B
 

Ulma Doctor

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Hi dbb,
i'm sure there is little difference whether you used iron or steel wire, they both contain iron
the annealed wire you got at home depot is soft steel
correct, the boric acid is a flux.
impurities that melt at a lower temperature will float to the surface and not contaminate the substrate

i really don't think it matters too much what you use
denatured alcohol and mineral spirits will flash off at a relatively low temperature

i have mixed water with boric acid in a pinch, it works-
but, i often wonder what i created when i substituted water :chemist:, :grin:


have fun!
 

john.k

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Pure iron wire is really soft,like lead wire......but I imagine also expensive.........much easier to get a tight wrap,I suppose.....a free source of this wire is/was motor car ignition coils....any coating is going to affect quenching.
 

benmychree

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Or, a person could use silver solder flux, essentially borax. I doubt that iron wire exists in the modern world, steel is what we have these days, such as baling wire and tire wire used for tying reinforcing rod. personally I use ground coke for protecting heat treating work in the furnace, it also prevents scaling and due to the relatively short time in the furnace, does not significantly increase carbon in the (very shallow) effected zone that is normally ground away in finishing the tool.
 

mikey

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Dave, I've been using Boric acid and rebar tie wire for heat treating for about 25years now. I used to tightly wrap the item with wire and applied the BA before heat treating but I found that the wire does little, if anything, to alter the outcome. The BA does. Now I just use the wire to either tie on to the item or form a basket and pay attention to applying the BA.

I mix termite powder, which is 100% BA, with denatured alcohol until it forms a paste that sticks and doesn't run. Apply with an acid brush to entirely cover the item and heat it. This forms a dark gray layer after heating but that comes off readily with a Scotchbrite pad. Then I temper it.

Works good, no problems.
 

dbb-the-bruce

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Dave, I've been using Boric acid and rebar tie wire for heat treating for about 25years now.

Works good, no problems.
Dang, I passed up on driving the extra 4 miles to Tractor supply for rebar wire..... Based on your comment though, the wire I have is probably fine. Any idea as to why the traditional approach calls for iron vs. steel?

The boric acid I ordered should be fine, probably sold for termite powder. Claims to be 99% boric acid. I looked for boric acid at the local HW store and all I could find was Borax products with all sorts of other crap in them.

Thanks.
 

mikey

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Any idea as to why the traditional approach calls for iron vs. steel?
Sorry, no. This method of reducing surface oxidation has been around for a very long time but I have not read anything based on fact; just anecdotal stuff like I'm laying out here.

I tend not to believe everything I read so I tried it both ways - wrapping the item to be heat treated tightly with wire and without. In both cases, the results were the same every time. Seems to me that the wire thing is either overblown or perhaps I'm missing something but I can't see what it might be. Now I usually just tie a long piece of wire directly to the part so I can safely hold it while heating it and quenching it in oil. The BA goes on after the tie wire is in place. If I cannot tie on directly to the item (like round stuff) then I make a basket from the wire and drop the item in there after coating with BA. I like the rebar tie wire because it gets red hot but doesn't break in use. Plus, its easy to work with so good enough.

There is a significant difference between using the BA and not using it. Clean up of the item is much, much easier with the BA than without. Hardness is the same; just the amount of work afterwards differs.

Just so you know, it is recommended that you temper the part while it is still warm, like right out of the quench. I tried this and also tried tempering a cooled part and I cannot see any difference in the tempering results. However, I don't have a hardness tester so my claims are suspect, okay? Anyway, I raise this because I temper by color and I need to see the surface of the part. I do not trust the temper of the whole part if I only clean one small area so I clean the whole thing. I usually clean off the dark gray stuff left from the BA until the part is clean, with a nice smooth surface finish. I also clean all traces of oil off with Acetone or Lacquer Thinner and put it in the tempering oven with a nitrile gloved hand. I learned that oily fingerprints will stay on a part forever after if you don't clean them off; hence, the glove.

I also experimented with cleaning stuff to get the BA residue off. I use Scotchbrite most of the time because it does not change the dimensions of the part like sand paper does. Metal polishes also work but are slow. I even tried buffing it off with a wheel and rouge but it removes metal so I learned not to do that. The combination of Scotchbrite that works best for me is the green fine one, followed by the extra-fine gray one to smooth the finish. Works fast, works good, and works even better when you can chuck the part up and use power.

Much more than you asked for - sorry. I just wanted to tell you a few things that might make things easier for you. Heat treating is something we all have to do from time to time so I hope this helps.

Oh, one more thing. If you haven't bought a torch yet, have a look at the Bernzomatic TS8000T. Puts out a lot of BTU's and works well with Propane or Mapp. I don't bother with my OA anymore because of that torch.
 

T Bredehoft

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I also clean all traces of oil off with Acetone or Lacquer Thinner and put it in the tempering oven with a nitrile gloved hand.
I learned the hard way that if there is oil on the piece being tempered it will turn yellow/amber then brown long before the steel does the same thing. You get a brittle piece if you go by the oil color.
 

Janderso

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Interesting, they call it, iron wire.
We’ve always called it bailing or mechanic’s wire.
I’ve been following along. I have considered a heat treating oven. The science of heat treatment is very interesting to me.
Great thread!
 

Cooter Brown

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Interesting, they call it, iron wire.
We’ve always called it bailing or mechanic’s wire.
I’ve been following along. I have considered a heat treating oven. The science of heat treatment is very interesting to me.
Great thread!

If you get a heat treating oven then buy this book its my new bible..... Its expensive as hell.... I was lucky enough to find an old used one on ebay for $90.....

20190918_071851.jpg

 

dbb-the-bruce

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I've got "Hardening, Tempering and Heat Treatment" by Tubal Cain. (workshop practice series #1, cheap in paper back)

I've just re-read the chapter 1 where he discusses the history of Iron production, early steel and roughly explains the chemistry (for a layman).
The part that caught my attention is the description of (paraphrased)

"early STEEL (prior to 1855) which is not the mild steel we know today. It was made by starting with "BEST"
or wrought iron heated in a box containing charcoal at 1000 C for 8 to 10 days (!).

The iron would absorb the carbon. The process was called the"Cementation Process".
Carbon content could be raised to 1.5% and the "steel" was used for making razors.
"

I'm guessing that the description of using boric acid and IRON wire come form the assumption that the iron will absorb some of the carbon and also that iron wire was a lot more common when the technique was used.

Anyhow, based on the comments here in this thread it looks to me like the actual make up of the wire has very little effect on scale reduction and that the boric acid simply forms a coating on the part that prevents/reduces air/atmosphere forming scale.

-Dave B
 

Cooter Brown

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The heat treaters guide has hardnening and tempering information on just about every steel and stainless steel alloy......
 

Janderso

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Hudson Steel is where I buy tool steel.
Their web site has lots of information including heat treatment and tempering stats on what they sell.

 

markba633csi

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I read somewhere that old wire coat hangers are iron, but they have a coating you'd need to remove
M
 

grzdomagala

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I always assumed wire is only to keep liquid flux from "dripping off" (sort of like a piece of cloth keeps water in place) and help spread heat evenly to keep sharp corners from overheating (corners will heat up much faster since hot gases "attack" there from multiple sides). So - anything that can survive the flame is ok :) (as long it's not zinc galvanised- you don't want breath the fumes).


Wysłane z mojego SM-N950F przy użyciu Tapatalka
 

dbb-the-bruce

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... and help spread heat evenly to keep sharp corners from overheating (corners will heat up much faster since hot gases "attack" there from multiple sides).
That's the best reasoning for the wire I've heard so far. Makes the most sense. If using a torch, it would be easy to overheat corners/edges.
And yes it does help keep the flux paste in place but I've read plenty of advice (jewelry work) where wire is not used.

That's the thing about all of these old "Do it this way wisdom" sometimes it's awful hard to figure out the Why? and everyone's been doing it that way for so long that they don't know the why.

-Dave B
 

RJSakowski

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We used borax for forge welding and brazing. Borax is the sodium salt of boric acid.

I suspect that the use of iron wire predates the modern steel production that came with the Bessimer process. Before 1860, iron wire was the only type available. Mild steel wire such as used for tie wire and baling wire is essentially pure iron, having .25% or less carbon and up to .9% manganese.

Soft iron has very little spring back, allowing a tight wrap. Alternative choices for smaller diameter wire might be flux core welding wire or the wire from spiral bound notebooks.
 

john.k

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iron wire is still used for the cores of ignition coils....its very soft,softer than annealed copper.........anyhoo,the modern method of heat treatment is vacuum furnaces etc,all very costly......also making a "packet " from some nickle alloy foil sealed up like a plastic bag,...again costly.......I might add,electric furnaces are also costly to run ,you are always replacing the elements.......once heated ,the element wire is very fragile,and any contact or splash while incandescent breaks it.
 

Nutfarmer

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The best way to prevent oxidation of tooling in heat treatment is to wrap it in stainless steel foil. also if you can put argon in the wrap it will help. if you need some stainless steel wrap to try pm me and I will send you some. forget the wire wrap and boric acid coating unless it is for a museum piece. If you are local I will run it through an oven for you.
 

Diecutter

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The best way to prevent oxidation of tooling in heat treatment is to wrap it in stainless steel foil. also if you can put argon in the wrap it will help. if you need some stainless steel wrap to try pm me and I will send you some. forget the wire wrap and boric acid coating unless it is for a museum piece. If you are local I will run it through an oven for you.
 

Diecutter

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I use KeepBryte anti-scale compound to protect oil hardening steel in an electric furnace. Available at mscdirect.com in a 3 pound can which will last a long time.
The maker states KeepBryte "is ideal for preventing scale or oxidation on tools, dies, components. A great feature is that after heat treating, the coating can be removed by soaking the part in very hot (boiling?) water, or in an ultrasonic cleaner as I do. No abrasives required. I then finish up with a fine brass bristled brush. The part then looks like it did prior to heat treat with no degradation of fine detail and no pitting.
 

dbb-the-bruce

Dave
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Success with the heat treating and boric acid.

My practice was this center to use with my dividing heading head. Here is the center:
IMG_3632.JPG
The boric acid has worked great preventing scale. It does create an almost glass like coating on the surface. A lot of it flakes and cracks off after the oil quench. I managed to stab my finger on the shards. What's left is really glued to the piece. I found the key to removing it: baking soda in hot water!

Works like a charm, like the Efferdent commercial. I little 0000 steel wool cleans up.

It can be a little tricky getting the boric acid to stick to the piece. So far I've just made a paste and tried to get it to stick. If you get it right it melts in the oven and prevents scale. Apparently, you can also heat the piece up and get the powder to melt/sick. Will try that next.

Here is the center in a mount that I'm going to bolt to an angle plate when needed:
IMG_3633.JPG

Can you post a shot of the title page or more info for that book? I found two possibilities, and would love to have copy.

-Dave
 

benmychree

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Success with the heat treating and boric acid.

My practice was this center to use with my dividing heading head. Here is the center:
View attachment 304976
The boric acid has worked great preventing scale. It does create an almost glass like coating on the surface. A lot of it flakes and cracks off after the oil quench. I managed to stab my finger on the shards. What's left is really glued to the piece. I found the key to removing it: baking soda in hot water!

Works like a charm, like the Efferdent commercial. I little 0000 steel wool cleans up.

It can be a little tricky getting the boric acid to stick to the piece. So far I've just made a paste and tried to get it to stick. If you get it right it melts in the oven and prevents scale. Apparently, you can also heat the piece up and get the powder to melt/sick. Will try that next.

Here is the center in a mount that I'm going to bolt to an angle plate when needed:
View attachment 304977



Can you post a shot of the title page or more info for that book? I found two possibilities, and would love to have copy.

-Dave
When I was an apprentice and later as a journeyman, we packed heat treating items in ground peach pit charcoal to prevent decarburization; can't get it anymore, so they went to ground coke, that is what I use, and pack parts in a stainless steel box with a loose fitting lid in the furnace.
 
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