Shadows Dance during HT question

blgoode

blgoode

Knifemaker / Craftsman / Service Provider
Joined
Oct 3, 2003
Messages
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Okay....One refresher question. While I heat my blades I am very careful o watch what is going on. The steel changes color and you get what looks like dark shadows dancing around. Do I wait untill those shadows disapear to quench?

I was thinking that I read that hapened just before the steel is ready to quench.

Thanks fellas'.
 
Its the trolls coming out of their sleep when the steel nears critical temp.
Seriously,this id caused by temperature variants and surface oxidation rapidly moving about on the surface.Do not use this as a temperature gague.True it happens as the steel is around the temperature of quench,but how close-too early or too late?There are several ways of knowing the exact temperature.In approximate order of accuracy are - A salt pot,controlled oven,digital High Temp. pyrometer (non contact),very experienced eye for the color ,closing your eyes and counting to 100 before quenching,and last - the shadow dance.
IG puts on a pair of magnifiers and watches until he sees the trolls jumping up and down to cool off their feet.He then knows the temperature is right.
SA
 
If you have even heat, like in a good forge or oven. The dissapearance of all the shadows shows guess what? Even heat :) You still need to make sure you are in the critical range with a magnet.

It's kinda cool.Steel will absorb heat up to a point where it starts into the critical range. It kinda likes to hang at that temp while its doing its transformation into austenite. Once its done with what it can do with it's little carbon doodads. It will start to rise in temp past the critical range and start grain growth. From what I've seen of the grain structure you've been getting, you are judging it pretty good.
That's what I like about using a forge VS a torch. I just keep checking with a magnet for assurance and have my forge running at the proper temp for the particular steel. Once the blade kinda dissapears in the background of the forge heat I know I'm very close or right at it. If you see the blade starting to rise in temp and get real bright. It's too late. I hope some of that made sense.
 
Reading you loud and clear :D I have a color sheet that shows the temp. range and an image sent to me by Charles Sauer just before he quenches. I always look at these a few days before doing a ht session.

I wont think about it too hard.....just go by the experience and results I have had. I just seem to get a little nervous because I dont HT everyweek so its sort of like learning the HT thing all over again. I'll pull my boot straps up and jump right in there ;)
 
Troll boogies
are what you have to watch for if you heat the boogers out of them the trolls stop dancing for you :D

it's like riding a bike after a while Brian.

I call it a lag point and just as the dances stops (slow as you go) then freeze the steel in place rrr I mean quench it :D
there's a little trick to getting it every time but you'll get it..and it will be the easiest and most cool part of heat treating for you. :)
 
Thanks Dan - and the other troll watchers :footinmou

Hey PM me that little trick...he he.
 
blgoode said:
Thats what I THUNK
Click to expand...

No easy way out on that one but it will stay with you for life..


you can go any where that has O/A or a good heat source
and a bench grinder and make a good useable knife. that is so cool.

I have an even heat but it's so much faster and easier for run of the mill
1 at a time knives to use the O/A :)
 
The shadows that move and dance may be different, but the shadow that stays stationary and appears and then fades with more heat can be a fairly accurate indicator of austenitizing temp. When you heat a bar of steel from one end it will glow bright and then there will be a shadow followed by a brighter glow again. This is decalescense (sp?) and what you are seeing is the austenite transformation occuring right before your eyes. Austenite recrystalization is an endothermic reaction, it requires energy (in this case heat) to work. When you heat the bar to Ac1 the transformation will begin and the heat energy will be used up by that transformation, causing the steel to glow duller until the transformation is complete. If one really learns to recognize that color just on the hot side of the shadow, they can nail the heat treat pretty good by eye alone.

Now the dancing shadows are probably a different case. Give this a try, I love it, heat a really big damascus billet up to around 1600F and then hang it up by the handle in a completely dark shop. Take your hammer and tunk it on the tip and watch the incredible light show! When the hammers energy gets transmitted to the steel it will send the coolest rippling waves of light, up and down the billet. Way better than a lava lamp or one of those silly plasma balls :D
 
Kevin R. Cashen said:
Give this a try, I love it, heat a really big damascus billet up to around 1600F and then hang it up by the handle in a completely dark shop. Take your hammer and tunk it on the tip and watch the incredible light show! When the hammers energy gets transmitted to the steel it will send the coolest rippling waves of light, up and down the billet. Way better than a lava lamp or one of those silly plasma balls :D
Click to expand...

See, I just KNEW you were a big kid! :D Sounds like a lot of fun to me. :)
 
I left the magnet out of the list because I was refering to temperature acuracy in the oven/forge.All carbon steels get a magnet check before they hit the oil in my shop.
SA
And don't forget to burn a sock first!
 
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