The Factory Floor

2:27 PM

@Shalvenay Heya Shal

@James hey there! glad we're able to talk at last :) wanted to talk over our answers to the question about quenching swords in dragon's blood :)

and if you don't mind, my answer on the blacksmith sabotage job as well

which one do you want to go over first? :)

Dragon's blood is probably easier.

A: Quenching swords in dragon blood; why?

Dragon's blood is an ideal medium for austempering While most blades, to this day, are made using water or oil as the quench medium in the traditional quenching and tempering process that James mentions, producing a tempered martensite microstructure, this is actually not the ideal microstructur...

looking at that in contrast to your answer -- I was wondering if you saw a fatal flaw with my proposal, or if you were thinking solely in classical Q&T terms because that's what you know, basically :)

Looking

@Shalvenay Ok yeah so this reminds me that I need to read up on austempering, until I read the other answers to this question I had no idea what it was. You were correct I was just basing things on my personal knowledge which was limited to lets call it "traditional bladesmithing"

2:44 PM

@James appliedprocess.com/wp-content/uploads/2018/09/…

(also, austempering is not exactly unknown in C&I edged stuff -- it seems that not only is it applied to lawnmower blades, it's in at least somewhat common if not widespread use for that application)

jdparts.deere.com/partsmkt/document/english/featbene/…

and industrialheating.com/articles/… (although this last one is registrationwalled)

That is a dense document

knifesteelnerds.com/2018/07/09/bainite-vs-martensite

(a bit of an interesting perspective as well, a bit contrarian but does illuminate some of the issues involved)

hmm, it could be that the dragons blood is good for Marquenching the blade, since getting molten salt in a fantasy setting might be more difficult, and dragons blood could generate heat magically

@AndyD273 yeah, we're looking for a low-magic approach here :)

That would be low magic... a passive effect

The point being to let the blade cool very slowly, instead of quickly.

you could melt salt in a forge for traditional Marquenching, but using dragons blood for that purpose would be a little more fitting for the setting.

And the idea of using molten salt to quench a blade isn't something that makes a lot of sense, but a blacksmith getting a similar effect by using hot dragon blood does.

3:27 PM

I need to read up but I don't get how molten salt...which would have to be pretty hot I assume, provides a large enough temperature differential to harden the cutting edge...

@James the salt used is typically a mix of sodium nitrate and sodium nitrite (some hobbyists have used nitrite-based bluing salts for this)

so the MP isn't all that high compared to the austentitizing temp of steel

(apparently there's potassium nitrate in some blends too, probably acts as a freezing point depressant using a 50-50 mix of nitrates)

Hmm...so it would cool more slowly which would harden it to an extent and given the steel of the tang/spine was thick enough would cool more slowly and remain flexible...

at least that is my understanding, I am certainly not an expert in material science.

actually, the initial quench starts off really fast (it has to, to avoid an unwanted pearlite reaction), but then sort of flatlines at the transformation temperature

huh...interesting.

I kinda want to make molten salt now...

Melting SALT in a Furnace

3:50 PM

►

Granted, that's table salt, but the other stuff probably works the same

@Shalvenay This seems like a good thread.

bladeforums.com/threads/austempering-advantages.260037

@James yes, if it's the thread I saw prior, it definitely is!

Seems austempering is generally really good, though it appears to vary from steel to steel type...the users tend to think that it won't hold as hard an edge but will be quite durable.

@James yeah, austempering is sensitive to where the "nose" of the TTT curve is, from all I've read, and that varies with steel chemistries

and yeah -- that's consistent with the industrial lit -- the absolute achievable hardness is less, but the durability at a given hardness is superior

Hrm...now how do I get a tub of salt heated to 500F?

4:00 PM

@James immersion heater and t-stat in a suitable vessel? (of course, you'd want a safety cutoff, too)

also, the paper I dropped as the first link has some important safety notes re: nitrate/nitrite molten salt baths (biggest one is that unsurprisingly, they're oxidizing, so don't contaminate them with things like graphite, carbon black, cyanide salts from austenitizing baths, oil, whathaveyou)

(also, on austempering -- come to think of it, when was the last time you heard of someone having a chunk taken out of their mower blade because they ran over a rock or the likes?)

2 hours later…

6:19 PM

Hmm, so apparently the new black market currency in China is cordyceps fungus. By weight it's more valuable than gold, and is used in traditional Chinese medicine kinda like how they used rhino horn.

I'm pretty sure this is how "The Last of Us" started...

7:19 PM

@AndyD273 I never even finished that game...

As I recall it started real slow.

@James I never played it. I just happen to know it was based on the cordyceps fungus. Found out about the game after reading The Girl With All The Gifts, which also involves cordyceps.