Plate Quench vs Slow Oil Quench

MBB

MBB

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I'm venturing into air quenched steels (A2 and AEB-L) and am curious about the benefits of plate quenching versus slow oil quenching (McMaster 28 seconds). I assume the plates help to prevent warp versus the slow oil? Is 28 second oil still too fast for air quench steels? I have seen a few proponents for oil quenching A2 versus a large number of proponents for plate quenching.

I already have plates, so that is not an issue. This is just a point of curiosity.

Thanks,

Mike
 
I've been quenching AEB-L and M390 that had too much grinding done ahead of time for plates to make reasonable contact in 16 second Citgo Quenchol with no ill effect. Hitting the targeted hardnesses, no cracking. The warp has been rather extreme in comparison to plate quenching. Since AEB-L grinds easy enough I'll likely stop pre-grinding with enough flat left for plate quenching, and with the other stuff, I'll stick into plates after an initial quench to try and prevent some warping.

How advantageous it is I don't know, especially if you're doing cryo to eliminate RA. Actually now I'm wondering why I even try. Is there another benefit to faster quenching than air or plates with little contact other than reducing RA?
 
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read what steel maker says. some give a time, like less than 1000F in a minute, some say oil or plates or forced air. do some small knives with oil quench and see what happens
 
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The best system is a five to eight second oil quench followed by immediately placing in the plates.

On most steels that use a slow oil, blades will harden OK in the plates alone, as the thickness is so thin.
 
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I believe for air hardening steel, the faster quench = less chance that carbon could be separated from austenite, grab free chromium and form Cr carbide at the grain boundary.
Which will lead to lower in both toughness and stain resistance. Also less austenite to be transform to martensite thus lower hardness too.
 
Stacy,

As clarification, do you mean a fast oil (like Parks 50 or DT48) followed by plates or 5-8 seconds in (non-fast) oil followed by plates?
 
shqxk said:
I believe for air hardening steel, the faster quench = less chance that carbon could be separated from austenite, grab free chromium and form Cr carbide at the grain boundary.
Which will lead to lower in both toughness and stain resistance. Also less austenite to be transform to martensite thus lower hardness too.
Click to expand...

So what qualifies as a fast quenching for air hardening steels?
 
MBB said:
So what qualifies as a fast quenching for air hardening steels?
Click to expand...

May be something faster than cooling in still air or faster than minimum pressure gas quench in vacuum furnace. As we can see there are some air hardening strel which has factory HT info stated that "vacuum HT may result in 1-2 lower in HRC"
 
I see how my wording could be misread.
I was saying a quench of 5-8 seconds duration. The oil would be the appropriate oil for the steel ... a 28 second "slow" oil.

Such a quench will be faster than air or just the oil, but won't really be a "fast" quench. The conversion to martensite would happen in the plates, helping to avoid warpage.
 
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on
Stacy E. Apelt - Bladesmith said:
I see how my wording could be misread.
I was saying a quench of 5-8 seconds duration. The oil would be the appropriate oil for the steel ... a 28 second "slow" oil.

Such a quench will be faster than air or just the oil, but won't really be a "fast" quench. The conversion to martensite would happen in the plates, helping to avoid warpage.
Click to expand...
on plate quenching, what is the desirable thickness of the plates or the minimum suggested thickness?
just 6061 aluminum?
 
Depends on the size of the knife, really the mass you're trying to cool. I have some 3/4" thick plates and some 1.25" thick plates that are soft jaw stock. They both work about the same, the 3/4" just heat up a little faster.

I think 3/4" is sufficient and probably more than necessary for thinner smaller knives.
 
Most guys look for 1.5 to 2" thick stock that is 3" to 4" wide. That will allow multiple knives to be done one after the other in a HT batch.

In practical terms, 1" by 3" plates should be fine for most thin blades.

18" long is a good length.
 
Thanks for the input! Now I'm debating getting some 28 second oil. Maybe play with the plates I have first and then decide.

I would be curious if the oil-to-plates quench results in higher HRC or lower retained RA than plates only.
 
I'm making an extensive testing with M390 steel (made around 30 blades so far + a few more that went to the trash...), mostly of them with Alu-Steel plates + forced air quenching and lately with oil-plates-air combination...also after heat treatment they were all in LN2 (deep).
Results?
I appreciate a slightly - I repeat, slightly- increase in hardness with oil+Alu or steel plates (around 0,5HRC)...as mentioned by kuraki oil only will drive mostly of the time to a warp blade, so I wonder if it pays off to add the oil step to the process...

I'm by no means an expert...but aim to be in M390 steel soon ;), but speaking to people at Böhler (I told them my intention to do this extensive -and expensive!!- testing) they seem to suggest metal plates rather than oil (Phil Wilson also followed the same route in a M390 testing he performed some time ago)
This is with 3,5mm & 4,5mm thick blades
My plates are 1-1,25" thick (steel and Alu)
If you want to increase the wear resistance go to high tempering temperatures and LN2(LN2 is vital if you want the very best results)...you will lose "some" corrosion resistance though ...and make sure your furnace is calibrated (specially if you cannot get access to LN2)
 
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