Case hardening steel with sugar fact or fiction?

acutron · Jan 25, 2007

I walked into work today, & the shop smelled like a damm cotton candy factory. One of the guys brought in a cheap wood chopping ax to sharpen & was told by someone to heat it up cherry red after sharpening & put in sugar. I have never heard of this one & figured I would post it here for fun before I cast any doubts. I did go to the candy machine for some M&M'S though lol. Has anyone ever heard of this?

wippin' boy · Jan 25, 2007

case hardening is about adding carbon
is there carbon in suger?

Forrest Addy · Jan 25, 2007

Won't work hardly at all as described.

The carbon in the sugar will immediately react with oxygen in the ambient air and turn into CO2. It takes time for carbon to diffues into the steel. OTH, sugar is a good source of clean carbon. In fact I recall an old carburizing recipe where sugar and 1/4" size limestone pellets are used in a retort to carburize steel parts imbedded in the mix.

Barbecue charcoal is better. It stays put. Sugar melts into a kind of syrup and pools in the bottom of the retort until it chars at about 700 degrees. Only then will its carbon release and react with the lime to make the carbon rich gasses that diffuse carbon into the steel.

He'd be better to make several applications of Kasenite and heat the ax in a furnace for a few hours. Kasenite and other cyaniding materials work by diffusing the carbon to the steel through a molten salt not via gas diffusion as in pack carburization.

By the way, heat treat tools that have been pre-sharpened to 1/32" of the finished edge. The surface of the steel is likely to de-carburize or scale. This will damage a fully sharpened edge and require sharpening all over.

If your shop buddy kicked his source of information square in the a$$ for passing plausible sounding BS as valid technique, he'd be doing to world a small favor.

This trade is hard enough to pick-up without garrulous morons cluttering the information stream with nonsense.

I know what his defense would be. "Hey. I was only passing on what a guy told me."

L Vanice · Jan 25, 2007

I suppose the axe handle gets carbonized while heating the head red hot to carburize it.

Larry

gwilson · Jan 25, 2007

The trouble with case hardening is that it normaly doesn't go in very deep.By grinding both edges of the axe,the soft interior of the axe will be quickly exposed.In the past,and in some really cheap Pakistani made pocket knives today,the bottom of the line knives were made by csaehardening one side only.Then,you were supposed to sharpen the knife by honing only the soft side,leaving the edge hard.Secondly,unless the axe was put under some means of applying a little air pressure to it,the hardening penetration would be very thin.Best to put stuff into a crucible and lute the lid shut.Even a little air pressure helps to drive the hardening compound into the metal.When the metal is red hot,the pores in it open up,and carbon can be driven in much better.Sugar would blow up the crucible as it released its hydrocarbons.Kasenite,charcoal or other purer forms of carbon should be used.

s7hss · Jan 25, 2007

This technique your buddy is trying also begs the question: is case-hardening good for a striking took such as an axe? I'd think this would make the cutting edge prone to chipping.

Thought case-hardening to be good for wear-resistance, not necessarily shock resistance. I'd think he'd be better off tempering the cutting edge to a bronze color or thereabouts and proper sharpening.

gwilson · Jan 25, 2007

I forgot to mention that after case hardening,the cutting edge should be tempered to successively darker straw colors,and tried until it can be barely filed with a fine cut,new file.

Ox · Jan 25, 2007

Sure sounds like a lotta werk for just sharpening an axe?

Think Snow Eh!
Ox

jim fuchs · Jan 25, 2007

joy dishsoap will harden metal, we tryed it and checked rockwell after and before ,it works?
jim

Ries · Jan 25, 2007

Somehow I doubt the Joy Dish Soap hardened the metal without getting it hot first.
So what you were doing was quenching the metal in a liquid, which cooled it quickly.

My guess is that in that application, Chicken soup, or Maple syrup, or Jack Daniels would all make a difference in the rockwell.

Heck, along these same lines, there are always wannabe blacksmiths, who sit and play sword and sorcery games all day and have never even been in the same room with an anvil, who will swear to you on the Kaballah that if you quench a sword in the blood of a live human being, it will become so hard you can cut down streetlights with it. Supposed to work even better if you use a virgin....

Metallurgy is pretty well understood, and if you go to a site like http://www.knifeforums.com/ you can find a lot of guys who will tell you exactly how to harden all kinds of alloys, without resorting to urban myths, ancient magic, or common food products.

John Madarasz · Jan 25, 2007

Here's an excellent tested method fwiw... probably doesn't smell as good as the cotton candy though

Super Quench

http://www.cvbg.org/tips/superquench.PDF

Alan H · Jan 25, 2007

Ries stated:

Heck, along these same lines, there are always wannabe blacksmiths, who sit and play sword and sorcery games all day and have never even been in the same room with an anvil, who will swear to you on the Kaballah that if you quench a sword in the blood of a live human being, it will become so hard you can cut down streetlights with it. Supposed to work even better if you use a virgin....

No, no ... You need a fat Nubian eunuch. It's not the salt of the blood, it's the fat of the thigh.
And don't forget to heat the steel until it's color matches the light of the harvest moon ...

stephen thomas · Jan 25, 2007

Looking at the table published, caustic soda is Sodium hydroxide, both are listed at 10% solution, why the vastly different listed cooling rate?

Someone I know personally who works professionally as a blacksmith posted on a forum about using sodium hydroxide solution to harden mild steel; merely as an exercise to see if it could be done. Messing with a solution like that does not appeal to me for the eye and skin hazard, so will stick with conventional tool steels & hardening processes, thank you very much.

smt

John Madarasz · Jan 25, 2007

Stephen, you are correct, and that's a good observation. I've since pulled the table and link, rather than create any confusion. The super quench solution is tested safe, and works very well. Thxs for the heads up

JST · Jan 25, 2007

Forrest.....

If you dip the red-hot item in the sugar or whatever, it probably will work marginally at least. The bottom layer will char right onto the iron.... Then it isn't like pot/box hardening, and it won't run off.

Of course, a person could also just do it right, with the kasenite.....

You are supposed to do that same thing with the Kasenite, IIRC....

On the decarb, if case hardening, isn't the surface all that DOES get hardened? So there shouldn't be hardly any de-carb surface.... unless you let it cool and then re-heat. I can see that being an issue.

IIRC the sugar deal etc, as well as Kasenite instructions want you to dunk it with teh stuff still on, at which point it is supposed to spall off and allow hardening. Dunno if it does.

For other goodies, how about the hardening in mercury for the ultimate fast cooling....... Per my old toolmaking books.....

boslab · Jan 25, 2007

well you can add carbon to steel with sugar, provided the steel is above 720 deg C before the application of the sugar, wich will in tha first instance caremalise then carborise, the carbon will dissolve into the surface of the steel, however the case layer will be very thin, kasnit is a better option which is reduced bones, hoofs and coal at 99% carbon

acutron · Jan 25, 2007

Thanks for all the replies everyone. When I seen what he was doing I just shook my head & laughed. This is the type of guy that would squeeze a piece of coal in a vise if someone told him he would get a diamond out of it lol.

spock · Jan 25, 2007

"joy dishsoap will harden metal, we tryed it and checked rockwell after and before ,it works?
jim "

Yes, it works, and very consisntently. Read about it in an old machinest home workshop or its sister. A guy was testing a recipe like the superquench mentioned above, his daughter (a chemist) looked at the list and told him that the only thing that was actively doing anything in the quench was the soap, which was dishwasher type liquid. I have used it several times, and can consistently hit 50 HRC on 1018 crs. Comes in handy every now and then!

Ernie LeFlore · Jan 26, 2007

If you heat up steel a little, then coat it with liquid dish soap, before heating it up, it will protect it form oxygen so it will not carubrise. I don't know if it helps anything else, but your part is cleaner.

No joke intended.

Ernie

Ernie LeFlore · Jan 26, 2007

Back to the sugar:

In the book "The Great Escape" the British prisoners case hardned some of their hand made tools with sugar. Wheather it worked or not they must of thought it did.

Ernie

Case hardening steel with sugar fact or fiction?

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