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Boyd C-F




Location: Nelson, New Zealand
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PostPosted: Sun 18 Oct, 2009 9:52 pm    Post subject: Steel Tempering Recipe         Reply with quote

Hi All

This may be of more interest to the hard core iron pounders out there...although you may know all about it, it is an oldie after all!

I was looking through "Dr Chase's Receipt Book" 1885ish and came across this recipe;

Steel -To Temper Very Hard
Take water, 2 measures -no matter what size - wheat flour, 1/2 measure, and 1 of common salt.

Directions
Mix into a paste; heat the steel to be hardened enough to coat with the paste - by immersing it in the composition- after which heat to a cherry red and plunge it in cold soft water.
If properly done, the steel will come out with a beautiful white surface, and very hard.

Remarks
It is said that this is the process in which Stubbs' files are tempered.

So is anyone game enough to try it out? Or know whats going on with this?

Cheers

Boyd
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Bruno Giordan





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PostPosted: Mon 19 Oct, 2009 2:52 am    Post subject:         Reply with quote

It sounds like carburization. Same as Teophilus' greased files.
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Matthew Fedele




Location: Auburn, NY USA
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PostPosted: Mon 19 Oct, 2009 3:22 am    Post subject:         Reply with quote

Hardtack for lunch again... I'll have to try this one of these days.
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Christopher Lee




Location: Sunshine Coast, Australia
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PostPosted: Mon 19 Oct, 2009 4:00 am    Post subject: How?         Reply with quote

How would this actually work?
Would the carbon to harden the surface come from the salt, held in place with the flour and water?
C
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Bjorn Hagstrom




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PostPosted: Mon 19 Oct, 2009 4:51 am    Post subject:         Reply with quote

The Carbon would come from the flour.
The exact role of the salt is unclear to me, brine is sometimes used as a cooling medium (as is oil) Brine transports heat differently than pure water. It is supposed to have something to do with how watervapor is formed (or not) on the surface of the heated material when submerged.

Adding the salt to the paste might just be a way of getting the same effect when cooled in pure water.

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Craig Johnson
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PostPosted: Mon 19 Oct, 2009 5:58 am    Post subject: Heat Treat         Reply with quote

Hi guys

My guess is the paste is more to dampen scale development. To carbonize the material it would need to be held at temp for a long time. The salt would help with the quench as it counters a steam envelope developing around the blade. Soft water could have salt in it. That, I believe, is what a water softener is designed to do add salt to water.

So the result is a system designed to reduce scale, pretty important in making a file, and using the right kind of water.

Best
Craig
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Anders Backlund




Location: Sweden
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PostPosted: Mon 19 Oct, 2009 9:07 am    Post subject:         Reply with quote

According to my blacksmithing teacher, mixing salt into the quenching process does produce a very hard steel. I forget exactly why, though.
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Jean Thibodeau




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PostPosted: Mon 19 Oct, 2009 9:13 am    Post subject:         Reply with quote

Anders Backlund wrote:
According to my blacksmithing teacher, mixing salt into the quenching process does produce a very hard steel. I forget exactly why, though.


Faster absorbtion of heat from the steel to the salted water than pure water maybe ? Faster cooling in other words ?

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Justin King
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PostPosted: Mon 19 Oct, 2009 10:01 am    Post subject:         Reply with quote

Salt water has higher density than fresh water. Objects that are just heavy enough to sink in fresh water will often float in salt water. All else being equal, greater density=greater heat absorbtion/transfer capability.
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Craig Johnson
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PostPosted: Mon 19 Oct, 2009 10:02 am    Post subject: Steam         Reply with quote

What the salt does is inhibits the formation of steam around the blade. Steam is a good insulator. When you plunge red hot steel into water it can actually form an envelope of steam which slows the quench. If the water is moving or agitated or has particulate mater of some form in it tis is reduced. That is why they had recipes for different hardnesses in the period discussions of this. They thought the different additives imparted attributes to the steel. What was actually occurring is they where regulating the speed of the quench. One of the draw backs to empirical systems, if you attribute the cause to the wrong affect it looks like it is working but it may happen for a completely different reason.

Best
Craig
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Boyd C-F




Location: Nelson, New Zealand
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PostPosted: Tue 20 Oct, 2009 1:23 pm    Post subject:         Reply with quote

So the paste stops scale, the salt stops steam bubbles, and the wheat could add some carbon. Interesting.
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Justin King
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PostPosted: Tue 20 Oct, 2009 2:10 pm    Post subject:         Reply with quote

I like Craig's answer better than mine Wink
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Justin H. Núñez




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PostPosted: Tue 20 Oct, 2009 2:18 pm    Post subject:         Reply with quote

While we're on the subject...what about rubbing a ram's horn on the steel?

I was watching TV Espanola and there was a smith that was making an axe head and he rubbed a ram's horn on just inside of the edge before putting back in the forge. he then quenched it in what looked like a natural spring inside his shop.

I missed what he said it did but all of his other explanations seemed right on.

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Craig Johnson
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PostPosted: Wed 21 Oct, 2009 6:48 am    Post subject: Temp indicator         Reply with quote

Justin H. Núñez wrote:
...what about rubbing a ram's horn on the steel?


Hi Justin

This is an area where we start to get into two different issues. The first is the use of techniques to impart a perceived transfer of attributes from the item to what is being made. If you are a Medieval person one could see the advantage of having something with the power of a Ram.

But there could be another reason, or a parallel reason lets say. That is the use of materials to fulfill a practical need. In this case the horn may have been a temperature test. Is the material hot enough to be quenched. The reaction of the horn to the hot metal is what tells you it is right. Over a long time this maybe understood as a way to add the Rams essence to the piece but it does have a practical effect.

Here is another example from MS 3227a (sometimes referred to as the Doebringer Fight Manual)

"If you wish to release the hardness from the iron; take human blood, and ‘leave it out’ till the water comes to the top, then strain the water into a glass and keep that. And when you then want to release the hardness, so take the hardened weapon and hold it to the fire until it is so hot that it ‘swallows-up’ (slinde) water. Then brush the water with a feather on the edge, thus the hardness is let out and it will become more flexible."
Translation by Keith Alderson

As is illustrated above the smith is using a material that allows him to get a temperature reading on the piece and then control the tempering. It does not actually impart anything into the metal. One needs to remember in these discussions that imparting carbon into a piece of metal is something that takes heat and time in a controlled environment. You can not functionally carbonize a piece in an open flame. It is something that has been misunderstood and used by some who are trying to sell something "special" to people that physics can prove does not work.

This all highlights that the smiths of old where just as smart as us. They used a different data base to understand the world. While tradition is a strong dictate in such societies they would not hold on to something that did not proven useful in doing there job over time on the practical level. It is something that scholars today sometimes miss in their understanding of what these craftspeople where doing, someone who is making something has a practical outlook on the process they need to produce in a time frame if the process becomes loaded down they will not be able to compete.

A smith is usually a very practical person and one who is working in a tradition that is based on core principles and techniques. These can be applied to many different products but they are all done with a group of knowledge that many had.

Hope this is helpful.

Best
Craig
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Boyd C-F




Location: Nelson, New Zealand
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PostPosted: Wed 21 Oct, 2009 10:22 pm    Post subject:         Reply with quote

Nice answer Craig.

Cheers

Boyd
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