Please can someone explain to me the difference between...

[Lord_Nick]

Normalizing and annealing? Thanks,
Nick

[PS_Bond]

Questions like that tend to get answered with a "yes" around here... :D

(Right - less sarky answer follows)

http://www.dfoggknives.com/hardening.htm
http://www.mintek.ac.za/Physmet/intermet/heatreat.htm
http://www.efunda.com/processes/heat_treat/softening/annealing.cfm

[Chux]

That was amazingly quick Peter :yikes:

[PS_Bond]

I've heard that before somewhere :rolleyes:

[David Morgan]

I'm not sure about the precise metallurgical difference, but for practical purposes normalizing is a quick stress relieving, and annealing is slow softening. To normalize heat to critical and allow to cool in still air. This should be done a couple of times after forging and a couple of times after grinding. To anneal, heat to critical and cool slowly in an insulating material, or even better, place in a fire and just allow to burn down. I anneal by placing a layer of charcoal in my propane forge, heating the blade, then throwing some more charcoal in on top. Switch off the gas and allow to burn out on its own. This should be done after forging and prior to grinding.

[Chux]

I've heard that before somewhere :rolleyes:

that must be a bummer

[PS_Bond]

Whereas I usually anneal by bunging the steel in a large ammo box full of vermiculite. If it is an awkward steel, like D2, there will usually be more than one bit of hot metal in the same box. I've managed to come back to the box after leaving it out overnight and still have things warm to the touch in it, so it works quite nicely for annealing. Ashes are also supposed to be good for annealing in.

[Tacol]

Ashes are also supposed to be good for annealing in.
Ashes ARE good to anneal, that's what I use. It takes hours and hours to cool down.
One negative point, it sticks on the steel. You need an energic wirebrush cleaning before grinding.

:biggthump

[MushiSushi]

now to to add something contentious ..... I have a print out on O1 that specifically says do NOT normalise O1 ..... hmmmmmm

[keith_beef]

Whereas I usually anneal by bunging the steel in a large ammo box full of vermiculite. If it is an awkward steel, like D2, there will usually be more than one bit of hot metal in the same box. I've managed to come back to the box after leaving it out overnight and still have things warm to the touch in it, so it works quite nicely for annealing. Ashes are also supposed to be good for annealing in.


You've managed to anneal D2?

When I asked about this on rec.knives, the general conscensus was "it's not worth the trouble".


KKK.

[MushiSushi]

D2 annealing ......800/850 oC for 4 hours approx. Cool slowly in the furnace at 20 oC maximum per hour.

?? . doesn't sound like much trouble?

[PS_Bond]

Well, I tend not to soak for that long as I'm working with industrially thin pieces, but yes - it anneals. (I think my cooling rate is a bit faster, however - 24 hours to room temp -> about 30ishC/hr)

Not nice to file regardless, but it is doable.

What is the justification on not normalising O1?
(http://www.pvsteel.com/docs/Tsb-112.pdf has HT for O1 - including detailed normalising instructions ;) )

Here's one that says not to normalise D2:
http://www.forgemaster.com/view_section.php?section=39

[MushiSushi]

I've got the print out somewhere.. but i have a reorganisation and can't find it now

pretty sure it was a download from Lindquist steel

[MushiSushi]

http://www.lindquiststeels.com/html/literat/tecbul/tecbul12.pdf

[Kevin]

.....(snips),,,,,,,

What is the justification on not normalising O1?

]


I have heard that annealing tends to make the carbides bigger. And undisolved carbides promote the formation of bainite and pearlite , instead of martensite.
I dont know enough to comment myself.


That bit of news is a b :censored: r if you need to soften the steel to be able to work it with a file and drill :yikes:

[MushiSushi]

would certainly explain the unusual grain pattern you got in the first colab knife, Kev

[Lord_Nick]

Thanks guys!
Nick

[Trond]

Now i am confused here.
I thought that the annealing was the thing you do after H/T?
I mean first heat the steel untill it is not magnetic (0,9-1,1 % carbon) THEN anneal.
IF you dont do this the steel will be to hard, (62-64 RC) the edge will be brittle, and there is a hazard of breaking the blade easy.
I tend to soften it to 56-58 RC by annealing the blades so the steel is brass coloured.
Am i wrong here? are my blades crap?
Please enlighten me

[David Morgan]

Trond, thats the process that most of us refer to as 'tempering', which as far as I know everyone does more or less the same as you; just a mix up in terminology. Annealing as I use the term (and as I have always seen it used) means to make the steel as soft as possible for cutting/grinding. The terminolgy seems to vary- I've heard the term 'tempering' used to refer to both the hardening and tempering of the steel, and some makers anneal the spine and tang of the blade as part of the tempering process. I guess translating from the Norwegian is an added complication!

[MushiSushi]

Trond. annealing is taking the metal to it's softest possible condition ...... what you are doing in taking your blades to 58 RC is tempering

[Martyn]

I understand em like this...

Hardening:
taking the steel to it's hardest possible condition, usuallly by rapid cooling from a high temp.

Annealing:
Taking the steel to it's softest possible condition by very, very slow cooling from a high temp.

Normalising:
Relieveing the stresses from steel (e.g. from forging), by cooling in air at it's own pace, from a high temp.

Tempering:
Taking the steel from it's hardest possible condition, to a softer, more usable condition ("tempering back"), by reheating after hardening, to a medium temp.


Obviously the temps and stuff vary depending on the steel, but this is how I understand the terms.

Also, I sometimes use "temper" in context to mean the state a knife is left in, after it has gone through the overall process of heat treatment.

[PS_Bond]

Blast. I try to use all the jargon, but the boss has sussed me.

:D

Normalising is also potentially appropriate for grinding too, AIUI - depends how hot you let the steel get when you're doing it. For example, I've just been cleaning up some forgings with an angle grinder - they will definitely be normalised after I'm done grinding them!

[David Morgan]

Yep, that's my understanding too- very clearly put. I would add that from what I've heard (and my own limited experience) normalising after grinding is important as well.

[one_rod]

The most extreme annealing job I ever saw was for a friend who wanted to make a bench-top anvil.

We managed to get hold of a 2 foot length of railway rail. This is fairly tough alloy steel and not easy to work in its "as supplied" state.
Having no other means available at the time, we annealed it by lighting a huge bonfire on top of it. Old pallets, packing crates, that sort of stuff. Let it burn out and left the metal to cool in the ashes. Took two days before it was cool enough to touch.
After that it was soft enough to work very easily.
We made it "anvil shaped" using an angle grinder and hand files.
Then we hardened the top by packing the rest of it in fire clay and blasting the top with a propane weed burner that we had borrowed. Once the whole top was glowing red we dropped it into a drum of old engine oil.
After that the top was hard enough to take a heavy hammer blow without leaving a mark, but the rest of the thing still soft enough to absorb the blows without cracking.


one_rod.

[David Morgan]

On a point of trivia, one of the most impressive examples of annealing involves not metal but glass; the annealing of the main lens of the 200 inch telescope at Mount Palomar Observatory took over a year.