Why water quench?

L

Leon Husock

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Jul 17, 2019
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I was thinking about the quest for successful water quenching and all the intricacies involved trying it (getting the water the right temperature first, etc), and it occurred to me that you're always going to temper the knife after quenching, which sort of renders the extra couple points of hardness you might get from water quenching it moot. So is there any reason to try for it? Besides tradition for its own sake, and possibly the sori you get on clayed blades.
 
It’s cheaper and less messy and because you can (if you work with laminated steels like me),

and on laminated steel blades you generally don’t get sori.

also no chance of fire from the water like there is from oil.
 
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You might get slightly higher hardness from water quench... and for most water quench steel, by using clay coat technique and quenching in fast oil has possibility to develop negative sori due to the speed of oil is not enough to overcome the thermal contraction.
 
shqxk said:
You might get slightly higher hardness from water quench... and for most water quench steel, by using clay coat technique and quenching in fast oil has possibility to develop negative sori due to the speed of oil is not enough to overcome the thermal contraction.
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Can confirm negative sori (tip dipipng down vs. up, yes?) in oil quenches with fully-heated blade ground to final thickness. If you can account for it, and/or aren't making traditional blades that demand otherwise, can be a perfectly acceptable result. But you also risk lasagna noodle edges as the spine expands to form martensite while the edge is still warm enough to be somewhat pliable.

Guess what I'm saying is that oil-quench is not risk-free either.
(I'm not moving to water, tho! *eek*)
 
daizee said:
Can confirm negative sori (tip dipipng down vs. up, yes?) in oil quenches with fully-heated blade ground to final thickness. If you can account for it, and/or aren't making traditional blades that demand otherwise, can be a perfectly acceptable result. But you also risk lasagna noodle edges as the spine expands to form martensite while the edge is still warm enough to be somewhat pliable.

Guess what I'm saying is that oil-quench is not risk-free either.
(I'm not moving to water, tho! *eek*)
Click to expand...

Yeah, I mainly do oil quench too cause having a crack or two at the edge is not fun.

Mostly what I concern are from when the hamon is not up to desire and need to re-HT several times and negative sori from oil quenching will start to be a problem.
 
There are some guys that to an interrupted quench for around a 3 seconds in brine followed by immediate dunk in parks 50.
Not sure if that would even out sori/negative sori.
I’ve only done brine quench a few times. Too risky for me.
 
daizee said:
Can confirm negative sori (tip dipipng down vs. up, yes?) in oil quenches with fully-heated blade ground to final thickness. If you can account for it, and/or aren't making traditional blades that demand otherwise, can be a perfectly acceptable result. But you also risk lasagna noodle edges as the spine expands to form martensite while the edge is still warm enough to be somewhat pliable.

Guess what I'm saying is that oil-quench is not risk-free either.
(I'm not moving to water, tho! *eek*)
Click to expand...

Hah, yeah. Personally I'm not aiming for sori so I just clay the sides of the blade and leave the spine clean (though I'm also not quenching at final thickness).
 
Water quenching is significantly faster than even fast oil. Some steels have very poor hardenability.
 
Water quenching is great if you like to make two piece blades out of one piece blades.
 
water quenching requires the right steel. It has to be low manganese and high carbon. Otherwise, you are better with oil. If not going for very active hamon, oil is far safer. It is a risk vs reward thing. Oil wins in my forge.
 
Going back to the OP's question, knowing that water quenching is more risky than oil, let's assume that you have two blades that are in the same steel, profile and ground the same.
Both are successfully quenched, one in water and one in oil. The water quenched blade is going to be a little harder, correct?
Assuming this, if you temper both blades at the same temperature, the water quenched blade will still be harder afterwards, right?
If all that is true, the question you have to ask yourself is: Is the little increase in hardness worth the risk?
 
I think instead of "hardness" your looking for the greatest conversion to martensite.


Also
If you're new to this "water" quench really refers to salt brine
 
The right steel for water quenching - laminated steel
Fhqox6L.mp4
 
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Robert Erickson said:
Going back to the OP's question, knowing that water quenching is more risky than oil, let's assume that you have two blades that are in the same steel, profile and ground the same.
Both are successfully quenched, one in water and one in oil. The water quenched blade is going to be a little harder, correct?
Assuming this, if you temper both blades at the same temperature, the water quenched blade will still be harder afterwards, right?
If all that is true, the question you have to ask yourself is: Is the little increase in hardness worth the risk?
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Interesting, clearly my metallurgical knowledge needs work. I've always thought of tempering as re-softening the steel just a little bit (since a file can skate on a knife pre-temper and bite in post-temper), so if you're tempering both knives to the same temperature, say 400 degrees for two hours, they would end up the same hardness. Or would you have to temper longer to get the extra hardness out of the water-quenched knife?
 
If the as quenched hardness is different, the tempered hardness at the same temperature will likely be different, though higher temperatures will have smaller differences. By higher I mean above 700 degrees. Not a likely temperature range for steels that need a water quench.
 
12345678910 said:
I think instead of "hardness" your looking for the greatest conversion to martensite.
Click to expand...

Does this lead to an increase in hardness?

Leon Husock said:
Interesting, clearly my metallurgical knowledge needs work. I've always thought of tempering as re-softening the steel just a little bit (since a file can skate on a knife pre-temper and bite in post-temper), so if you're tempering both knives to the same temperature, say 400 degrees for two hours, they would end up the same hardness. Or would you have to temper longer to get the extra hardness out of the water-quenched knife?
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The as quenched hardness comes from the aus temp, soak time and quench media. Some steels have a "secondary hardening curve" when tempered a certain way. I don't believe this applies to steels such as 15N20, 1084 etc.
You'd have to temper the one with the higher hardness with a higher temperature to get it down to the same RC as the one with lower starting RC.
 
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