Normalizing

[ALW]

Another question on normalizing.  Karl, you talked about doing three cycles of normalizing on forged steel to reduce the stresses.  Would three cycles, as you described, be necessary when simply doing stock removal?  Just wondering.  There wouldn't be any stresses from hammering, just cutting and grinding.  Would one or two cycles be sufficient?  Thanks.

Aaron

[kbaknife]

Nope, I don't think I said anything about relieving stresses - did I?
It's mostly for even distribution of alloys and grain refinement. In that respect, yes there are stresses, but it's stresses from uneven distribution of the alloys creating different steel structures throughout the blade.
Truth of the matter is, you have NO IDEA of the condition of that steel. NO IDEA of what mill it came from or how it was treated.
When you thermal cycle in three REDUCING HEAT steps, with good heat control for EVEN heating of the target steel, you DISSOLVE the alloy for even distribution and in the cooling process enhance grain refinement.
I always think of different steel types as different types of cakes with different ingredients.
We have "simple" tool steels and we have "high alloy" steels.
A simple cake would only have flour, egg, water, just basic ingredients.
Wouldn't take much to get all of that dissolved and evenly distributed.
But as soon as you begin to make a more complex cake, with a lot more ingredients, the more stirring, the more heat and the more TIME is needed to evenly distribute the ingredients and the more time in the oven to get it cooked.
For example, to austenize 1084 for hardening, you barely need to get it much more than non-magnetic (1414) and quench in something wet! It has very few ingredients.
But, to do it properly, 5160, because of all the chromium and other alloys, needs to soak at 1525-1550 for a GOOD! 20 minutes.
A LOT more heat and a LOT more time.
I know I'm going on here, but just to delineate between simple steels and complex steels.
Is it important to thermal cycle blade steels?
I can come up with a lot more reasons to do it than to not do it.
But make sure to do it in REDUCING HEATS!!
If a subsequent heat cycle goes ABOVE the previous cycle, then you just lost overything you were trying to gain!
Go HOT on that first one to dissolve all the alloy and let cool to black, then right back in the heat.
Heat the second time to a nice even orange color well above non-mag, but not as hot as the first time. Once again, just back to a black heat, which will be about 900 degrees.
On the third one, just to non-mag and let cool to room temp.
It's a really basic procedure, but better than NOT doing it.

[Lin Rhea]

I agree with Karl. It dont hurt to do it, but it may hurt NOT to.

A lot of testing and time have been spent trying to figure out the magic (not literally magic   :D   ) number and, from what I have read, three is it. Three times. After that the returns are deminshing and may even have negative effects. This does not mean you cant thermocycle more than one session of three during the whole forging, grinding, heat treat process. You can and thermocycling generally will help each following step up to the quench.

This information is just what I and Karl as well as many others gather while at the Hammer Ins and classes. It's not to say that it's the final word. But it does seem to work well. Lin

[ALW]

Sorry, didn't mean to raise any hackles.  I guess I read it wrong.  Thanks for the info.

Aaron

[kbaknife]

No hackles were raised - to the contrary - you just gave us another opportunity to discuss what we enjoy!

[mater]

Where can a guy come up with a color chart to see differant heats of steel? Ever seen any?  Thanks Mark

[Lin Rhea]

Yes. But I cant remember where.    

After I said it, I thought about how little help that is. Lin

[Montauks]

Scroll towards the bottom of this   LINK

[mater]

Thanks, Ill copy that.  Mark

[Lin Rhea]

Yep, that's where I saw it. Lin

[Ragnarok Forge]

The machinists Handbook has color charts in it that make for great references when forging / normalizing / hardening your steel.