Thoughts on quenching with water before or after oil?

Forgive the off the wall question here, but I have seen some 'smiths here and in other forums discuss using water (Usually before, but a few have said after) in combination with an oil quench. I was just curious about the process and or benefits. Could this method be suitable for some steels more than others? Quenching in water after a few seconds in oil seems to make more sense to me, than vice versa, but perhaps my thinking is off base. I thought about doing a little experimenting with 1084 later in the week, but I figured I would ask here first.

I think that there are some who quench in water for 2-3 seconds and then switch to oil to slow the rate of cooling. It's sort of like the interrupted quench where the blade is quenched in the water for 2-3 seconds to beat the nose of the cooling curve and past the Ms point then pull it out to slow the cooling and reduce the stress on the steel for 3-4 seconds and then return it to the water to keep the retained heat in the steel from over tempering the blade. Personally, I don't see the advantage. The major temperature shock and convulsions that the blade will go through will occur in that 2-3 seconds that is needed to get the steel past the nose of the cooling curve and down past the Ms point. If the blade is going to crack, it will crack then.

It would make even less sense to me to quench the blade in oil for 2-3 seconds, beat the nose of the curve and go past the Ms point, then transfer the blade to water to speed the rate of cooling.

My personal advice is to quench in oil unless you have a steel that will not harden adequately in it or unless you are trying to maximize the hamon effect in the blade. Then you might want to give water or brine a chance or get an oil that is designed for quenching shallow hardening steels.

Doug

Mark Redmon said:

Forgive the off the wall question here, but I have seen some 'smiths here and in other forums discuss using water (Usually before, but a few have said after) in combination with an oil quench. I was just curious about the process and or benefits. Could this method be suitable for some steels more than others? Quenching in water after a few seconds in oil seems to make more sense to me, than vice versa, but perhaps my thinking is off base. I thought about doing a little experimenting with 1084 later in the week, but I figured I would ask here first.

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I need to get the next part of the hardening threads, “the quench”, posted as it will give details on some of the issues involved here. But for now, to be quick and to the point, the mechanisms and transformations in a quench are such that the ideal condition is to quench as fast as possible from your chosen heat to below 900F and then begin slowing so that from 450F to room temp is as gentle as possible without a halt or reverse in cooling. The time to beat occurs around 1000F to avoid making pearlite, any pearlite made will be a portion of your blade that cannot harden. Nothing in this range is hard or high stress so no cracking should ever occur there. The real stress happens when the blade actually begins to harden below 450F-500F, it is here that too severe a cooling will result in cracking or distortion. This is not to say that uneven cooling in the high range could not set up conditions that would lead to the cracking in the lower range, just that this is where it will show itself.

I myself do not see the need for any second quench so long as you get as near to 450F before interrupting, the air is the safest and most effective way to cool through the hardening phase so long as the cooling is continuous. But water actually has a cooling potential of over 4,000F per second so perhaps some use the oil because choosing the exact moment that it would obtain 450F is near impossible. I know why others may use the two quenches since water is something I only worked with briefly a long, long time ago, but I can safely say that inverting them, with the water last, would give you the worst of both worlds according to what the steel needs in cooling.

I have used water 1 sec . then quickley into oil with medium success . Quenching in oil first , then water .???? I cannot see any benefit
As Kevin says its the worst of both worlds . Dont even think about it .

Thanks for the information, gentlemen. I have only seen the oil before water process mentioned by a few people. It makes sense that this is a bad idea, but I couldn't help but wonder if there was something I was overlooking. The water then oil quench is something that I've come across with some frequency, so I thought it might warrent some testing. I may still play around with it at some point, but I'm in no hurry to ruin any blades..

Just some additional thoughts on the matter. As Kevin said, once the steel descends below the Ms point and allowed to cool further all it will do is convert to more martensite regardless of the rate that it cools at, unless you want to slow the rate of cooling very dramatically to transform some of the austinite to lower bainite. Depending on the alloy, you would be talking about delaying the cooling to the Mf point for several hours.

If one really wanted to decrease the shock of the steel passing from the Ms to the Mf point marquenching, also known as martempering, would be the way to go. With that the steel is quenched in oil to just above the Ms point, for 52100 that would be about 500-510°. The Ms point for that alloy is about 490°. The steel is then held at that temperature to equalize the interior and exterior temperature of the steel and then taken out to air quench. From the temperature of the initial quench you will have about one minute for the temperature of the steel to descend past the Ms point.

I've been using peanut oil for this, which requires close monitoring while the oil is being heated. Low temperature salts might be a better choice if not marquenching oil. Kevin has commented on this and expresses doubts as to the peanut oil held at these temperatures being able to transfer heat well enough to beat the nose of the cooling curve at around 1100°, which remains fairly flat until about 1000°. I've made two test blades, one heat treated by austempering and one by marquenching. They've performed well at edge retention by still shaving hair after chopping through a 2X4 once. They both got about 90 cuts through 3/8" manilla rope before they started to drag after resharpening following the chop. Next it the 90° bend. I hope to send the blades out for eventual microscopic examination after I build my savings back up.

Doug

In my experience , I only do this water to oil quench on steel that are not specficly designed for water quench , so do the 1 sec quench then quickley into the oil . I also only do this If I want a hamon on say 5160 or 9260 . I have done it quite often . You have to time it right and temp in both quench mediums must be close to avoid too much shock. here is picture of 9260 I double quenched . you know the old addage about pictures. The wrapped piece is 9260
and the side view of blade with hamon is 5160..........

PS its not for the faint of heart ........

Some people would accuse me of enjoying overcomplicating the simple art of bladesmithing, I like to look at it more as I enjoy reminding folks that nothing in life is ever as simple as it first appears, and that steel offers us a beautiful complexity that we can explore and challenge ourselves with for many lifetimes of wondrous exploration. My wife has me watching the Olympic gymnastics competitions and I find myself getting a lump in my throat as well when I watch a recipient tremble with uncontrolled emotion in the award ceremony. They saw a lifetime of disciplined study in the science of each physical move and embraced the challenge and now reap the rewards that no simple recipe could have given them. I envy them, not for being the best there is, but for having such a love for what they do that they explore it to levels most of us will never comprehend. That is worth gold!

With that introduction, let me tell you that there is no danger of ever reaching the limits of the variables in heat treating steel and Ms is just one of those. Ms looks like such a solid and unchanging line across the bottom of the I-T diagram, boring and predictable, but mistress steel could never be so mundane. Ms (martensite start) is a function of chemistry, once again seems pretty cut and dried, after all one can’t change the chemistry just by heating… Or can they?

Ms is a function of the chemistry of the parent austenite, and carbon is one of the main chemical components. The carbon content of austenite is determined by the temperature it is heated to. So just when we get comfortable with trusting the I-T diagram to give us Ms for our favorite steel, our trust is dashed without knowing the exact temp at which the steel was austenitized. Fortunately many of the better I-t charts include that tidbit. I actually realized this years ago when looking at several I-t curves for 52100 all giving a different Ms ranging from 550F all the way down to 350F. I was quite puzzled until I noticed the austenitizing temps at the top of the charts and then it hit me and I let out the obligatory “of course!”

Now before anybody considers giving up because this alone sounds so darned confusing and unpredictable, embrace it! Look at it as if you just found the foot placement for a somersault that was one part of a routine that put gold around the neck of one of those little girls. Think of how much richer her life is than her friends who just did the minimum in gym in order to get back to laying on the couch and texting their friends. Isn’t steel cool!

Bubba-san, so much for the claims that you can't get a hamon by clay coating 5160. From the wavyness of the line I take it that it was clay coated.

Kevin, I see what you mean. I found a second IT diagram in my book for 52100 that austinized at 1950° instead of 1550° with a grain size of 3 instead of 9 (maybe due to the high austinizing temperature?). The Ms point shifted to about 295° instead of the 490° for the lower temperature and they didn't even bother to show the the Mf point, just the M50 which was around 190°. Would I be correct in interpreting that as an indicator of increased retained austinite? The Jominy hardenability graph showed a lot deeper hardening, like 85% martensite out to 2.5" with an HRc of 60 as opposed to no martnesite measured past 1" with an HRc of 30 at 2.5" for the steel austinized at 1550°.

Doug

Doug, you know I never questioned the metalurgic aspect of it . I was shown how to treat 5160 by a philipino smith a few years ago . I was always under the assumption that putting a hamon on 5160 by the clay method was not possible . I still don't understand the mechanix and the science behind it . I have another blade somewhere in my picture file of it . The Hamon is very dark instead of light ,it is also 5160 .
The clay was applied and, clay line was simply wiped off with my fingers . There was no clay on the hardened edge . I treated it like was 1060
or one of the simple steels . I did not let it get too hot . It was passed across the flame of forge very smoothly and steady , with the other hand I constantly checked the magnetism until it was non-magnetic and immediatly went to water 1 sec. then right into the oil. I have lost a couple doing this but, it does work . You and Kevin can probably explain the metalurgy behind this technique better than myself . Bubba