Thread: Grain Refinement Video

Thanks for sharing. Great demo!

Thanks, Charlie - I've been looking for this info this week, so your video was perfectly timed. Did you use a magnet to determine temperature? I looked at the knife article your mentioned, and he was eyeballing heat. I wonder how normalizing would work with a salt pot? There we can set heat with a thermocouple, and soak for a while, and reduce the a heat a tad each time like the knife guy suggests. Guess it's time to pick Mike's brain again.

Originally Posted by skipnord

Thanks, Charlie - I've been looking for this info this week, so your video was perfectly timed. Did you use a magnet to determine temperature? I looked at the knife article your mentioned, and he was eyeballing heat. I wonder how normalizing would work with a salt pot? There we can set heat with a thermocouple, and soak for a while, and reduce the a heat a tad each time like the knife guy suggests. Guess it's time to pick Mike's brain again.

Yes, I used a magnet and my eye as an indicators. I would let the metal get to nonmagnetic then put in back in the forge for a minute or two more. My forge runs at about 1500 when turned way down it is pretty steady with its temperature. I did not lower the temp each iteration, I just cycled critical then quench, it works well. I can see it with my eye and feel it with the hammer as I was breaking the samples.

I use my digital oven when doing razors. I was illustrating the process with the forge.

Charlie

Awesome video Charlie.

Originally Posted by skipnord

Thanks, Charlie - I've been looking for this info this week, so your video was perfectly timed. Did you use a magnet to determine temperature? I looked at the knife article your mentioned, and he was eyeballing heat. I wonder how normalizing would work with a salt pot? There we can set heat with a thermocouple, and soak for a while, and reduce the a heat a tad each time like the knife guy suggests. Guess it's time to pick Mike's brain again.

I use a magnet sometimes, but a couple of times I've eyeballed it.
For complex steels, eyeballing may be much more difficult, but for simple steels, you can do this more easily.
I used the magnet initially to figure out which color goes with the critical temperature. Now I try to get it right by comparing to that color.

Mind you, that is not always a recipe for success
But luckily, if at first you don't succeed, you can easily try again.
And success is easily established by visual inspection and spark testing.
If I touch the edge of a knife to my belt sander, and I see every part of the edge generating a fountain of sparks, I know that the heat treatment was successful.

Sorry I don't mean to be a late bloomer on this thread or a buttinsky. I have been reading about normalization, HT, and annealing and this sprung some questions. Is grain refinement the same as normalization or a method similar to normalization? The difference that I see, in this process, is that you are quenching it each time. I thought in normalization you let it air cool to around room temp? Also, Charlie, do you do this on your razors? Would doing this increase the risk of cracking or warping? I assume not since it gets "tougher" as you go on. Did you test the RHC between each cycle?

I normalize by getting a hair above critical temp then air cool to relieve the stresses of forging. I use cycles of right above critical temp then quench to refine the grain. Both processes will refine the grain, but the rapid cooling works better for me to reduce the grain size.

I am more worried what the grain of the metal looks like than hardness, you can get a very hard piece of metal with large grains that will not make a good blade. I want a velvety looking grain when I break a test blade.

Yes I do this on razors, I have not experienced a lot of warping



New Grains formed by Phase Transformation section starting on page 68 of this http://www.feine-klingen.de/PDFs/verhoeven.pdf is very helpful.


Charlie

The effect of grain reduction will reduce warping because there is little difference between grain sizes across the piece. Example: if one side of the blade had been overheated and grain size increased, then as the blade is heated to critical for the heat treatment and quenched, then the larger grains will be reduced and there will be movement of the steel in that direction, causing a warp. That's just about as simple as I can say it anyway.

So, during the thermal cycling process any straightening that needs to happen, should be done, followed by another cycle. At the last cycle, e.g., final heat treatment, there should be little movement of the steel at all. There is more than just toughening going on.

Thank you gentlemen. This makes a lot more sense now. Looks like I have my reading for the next week or so 201 pgs.