Steel industry / Users use same technique as kamis!

[ddean]

Who'd a-thunk it.

http://www.key-to-steel.com/Articles/Art12.htm
"Temper colours formed on a cleaned surface are still used occasionally as a guide to temperature........
For turning, planing, shaping tools and chisels, only the cutting parts need hardening. This is frequently carried out in engineering works by heating the tool to 730°C, followed by quenching the cutting end vertically. When cutting end gets cold, it is cleaned with the stone and the heat from the shank of the tool is allowed to temper the cutting edge to the correct colour. ......... "

Lacking only the teapot of course.

 

[Dan Harden]

A. The opening abstract covers soaking in a furnace at tempereture. This is essential to convert as much of the cross section as possible.
B. The full _immersion_ causes as much conversion to martensite throughout that same section. Pouring water over a surface is not the same thing. You wil get surface hardening. Doubt it? I will cut up any Kukri we care to offer starting with my very own, Etch them in a nital etchent, test them, and prove it.
It is no way to fully treat steel

There is an article here to that very topic, where Bill poins out the sharpening revelaing a softer core.
Quenching end mills with immersion is different.
They used to do it in cyanide baths as it increased the as quenched hardness.


cheers
Dan

 

[Yvsa]

Originally posted by Dan Harden
B. The full _immersion_ causes as much conversion to martensite throughout that same section. Pouring water over a surface is not the same thing. You wil get surface hardening. Doubt it? I will cut up any Kukri we care to offer starting with my very own, Etch them in a nital etchent, test them, and prove it.
It is no way to fully treat steel

cheers
Dan

Dan methinks you may have misunderstood what Dean is saying.

Originally posted by ddean
When cutting end gets cold, it is cleaned with the stone and the heat from the shank of the tool is allowed to temper the cutting edge to the correct colour. ......... "

I read Dean's post to say that the heat from the rest of the khukuri is allowed to temper the edge and nothing more, same as the item in Dean's post.
And indeed that is the conclusion that everyone here seems to believe, or at least those of us who have been around long enough to know about the discussion.
I'm aware, and I'm sure most here are, that the center core of the khuk's edge is soft and that the edge is simply surface hardened as you say.
However I'm of the opinion that though the center core is soft it does extend further up the edge than one might think.
And yet there will be a point reached where the sides of the khuk will be harder than the center edge.
I guess what I'm trying to say is that the khuk has an ample hardened edge and that it's good for a lot of wear and sharpening before it will need to be rehardened as they do it in Nepal.

 

[ddean]

Remember Bill's comment about how one of the kamis
showed him how to harden with the teapot pour, &
watch for, what was it, 6 changes of color?

That was the point that really caught my eye
in this reference.

---------------------
re the discussion--

I'll estimate the hardened core goes back fairly far;
especially when quenching with water.
Per the chart in that article, if the quench
reduces the temperature fast enough,
then you get the hardening.
Edge thin, cools fast.
Hardness will extend -somewhat- higher on the exterior.
I'd be very surprised if someone could prove
a soft core extended anywhere near the edge.

Now, in recognition of the principle involved,
if you plunged the whole blade in &
removed it pretty quickly (with exact timing),
then the exterior would have a hard surface and
the core would be softer.

 

[Dan Harden]

Hi Guys

No I understadn Dean well enough. I just think there are far better ways to treat steel in the same amount of time (same cost).
Dean your second paragraph covers what we call an interupted quench many of us do it as a standard for simple carbon steels. But you miss the point that the second quench fully converts the martensite to a managble degree. Subzero quenching and temeoring will convert retained austenite anf give you an added 2 points rockwell without added loss of ductility.
As for the other posts there is much to cover about the steel used in the swords. It is a GREAT misunderstanding to think of the early cementation processes that resulted in sheer steel and double sheer steel and consider it case or surface hardening. It was far deeper than that. So much so that you could make it agrueent that they were on a part with japanese swords for hard edge /soft core.

Anyway I 'll be wayw for a few days but I would love to chat when I get back. Have fun you guys

Dan