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Heat Treating and Metallurgy Discussion of heat treatment and metallurgy in knife making.

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  #1  
Old 03-17-2006, 09:45 AM
RJ Martin RJ Martin is offline
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Press Quenching 01 Steel

As expected, the 3" x 2" x .25" Thick test piece did not fully harden.

Austenitizing temp was 1460F, soak time @ temp was 20 minutes.
Pressed between two large, 2" thick Al plates @60F, in foil packet.

As quenched hardness was Rc36

Sample was subsequently reheated at the same temp/cycle, and oil quenched to Rc63 to verify the steel type.

If I had some thin stock, I would try it again, but, I think the results might be only slightly better.


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  #2  
Old 03-17-2006, 11:13 AM
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mete mete is offline
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Thank you RJ ! At HRc 36 that's not even close and I don't think 1/8" would do much better. Too bad.
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  #3  
Old 03-17-2006, 11:40 AM
Chris Meyer Chris Meyer is offline
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Any chance that copper plates would be fast enough?


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Old 03-17-2006, 11:51 AM
fitzo fitzo is offline
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Thank you for doing the experiment, RJ!
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Old 03-18-2006, 11:11 AM
RJ Martin RJ Martin is offline
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Chris: No, copper plates wouldn't do it either, IMO.


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Old 03-18-2006, 07:04 PM
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Thermal conductivity - silver -1.00, copper - .94, aluminum - .53 So copper is twice as fast but still probably still not fast enough.
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Old 03-18-2006, 10:35 PM
Chris Meyer Chris Meyer is offline
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I guess Mr. Martin will just have to get some big chunks of silver and give that a try.


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Old 03-19-2006, 12:25 AM
sleepy sleepy is offline
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Just out of curiosity would it work if the quench plates were at a much lower temp to start with?
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Old 03-25-2006, 09:43 PM
twistedneck twistedneck is offline
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Press quenching sounds awesome, ever have foil sticking issues when pressed hard at 2100F? I have argon and was thinking about a mini press quench chamber plummed with argon.
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Old 03-26-2006, 08:46 AM
RJ Martin RJ Martin is offline
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Twistedneck: 2100F is pretty hot, and more than you need for any CPM alloy I can think of. However, you can apply pure talcum powder to your blades and it will help prevent sticking.

By leaving the blades in the foil the whole time. the sticking issue becomes much less important. Once the blades are cool, you can generally peel it off, or, at worst, grind it off.


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Old 03-30-2006, 08:08 AM
Owen Wood Owen Wood is offline
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R J Martin,
I have just found this great forum and have spent far to much time perusing the many exciting and interesting threads in the last day! Today I wil have to get back to the workshop!
I all the I been quenching between 1 inch thick steel plates in a vice with very good results. The blades are not ground and are still in foil bags when quenched. Air hardening steels are quenched with the plates at room temp. Damascus (in my case 1095 and 15N20) is quenched with plates that have been retrieved from the deep freeze. As quenched hardness in the case of Damascus is 64 - 66RC. The blades of course are dead straight - a very big plus.

I have not tried to harden O1 in this manner. .25 is fairly thick. I will run a test on a 1/8 piece of O1 over the weekend. What is very important is the time that it takes to move the package from the furnace to the vice. Any undue delay and the temp drop will definitely mean that full hardness is not achieved. The press or in my case the vice is placed about 6 inches from the mouth of the furnace - the package being whipped out - dropped between the plates which are then clamped shut as quickly as possible.

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Old 03-31-2006, 08:43 AM
RJ Martin RJ Martin is offline
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Owen: Glad to have you here!
I agree-For press quenching 01, time is if the essence. You might want to increase the Austenitizing temp by 10-15 degrees and use chilled plates.

Please post your results when you try the 1/8 thick stock.


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Old 04-05-2006, 06:47 PM
Owen Wood Owen Wood is offline
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Hi RJ,

Many thanks for the welcome. this is a great forum. Very firendy people and I have already learned a great deal.

As to the tests:

Three pieces were hardened each in a separate foil pouch. Austenizing temp 1500 Deg F. Soak time 20 min. Quenched between ground steel plates approx 3/4 inch thick prechilled in the deepfreeze. (probably about 25 deg F). The plates were not rechilled for each quench. Rather all three quenches were performed (starting with the thickest piece) one after the other. Time taken for all three was approx 4.5 minutes.

A .095 X .38 X 1.0 average of three tests RC 63

B .145 X .55 X 1.2 average of three tests RC 64

C .238 X .55 X 1.2 average of three tests RC 64.5

It is very important to keep the interval between furnace and quench to an absolute minimum. It seems probable that the increased austenizing temp helps a great deal in keeping the piece above critical temp between furnace and quench. Note that the Heat Treaters Guide gives austenizing temp for O1 as : 1455 - 1500 deg F.

I expected to find that the .095 inch would fall below the critical temp before the plates were fully clmped to its surface - but the tests proved this to be a false assumption.

This method for quenching thin stock without having to remove it from the foil bag obviously has great advantages.

I will carefully cut the .238" piece in half - grind the edges perfectly parallel under water and do a hardness test in the center of the section.

Hope that this is of interest

OW

Last edited by Owen Wood; 04-05-2006 at 07:02 PM.
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Old 04-05-2006, 08:40 PM
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Yes, very interesting . In comparison to the thermal conductivity mentioned above , iron is only .18 considerably slower than aluminum which is what most use. Keep us informed of further tests.
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Old 04-06-2006, 07:07 AM
RJ Martin RJ Martin is offline
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Owen: Very encouraging. Thanks for that detailed info.

I am mentally wrestling with the small size of the test pieces, wondering if your results will translate into a longer, wider piece.

And, there is the issue of the ground portion of a real blade cooling fast enough.

I may go back and try my thicker piece again, at 1500F instead of 1460F.

Want to grind a small blade from 1/8" stock and try it again, Owen?


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