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YouTube
The following information is also available as a YouTube video for those that prefer watching to reading. The video might be more fun though there are more details and more discussion in the article.
Oil
One common rating method for quench oils is the quenchometer “nickel ball” test. A 12 mm nickel ball is heated to 1620°F and then quenched into 200 ml of oil. Nickel reaches the Curie point at 670°F at which point it is attracted to a magnet.
The nickel ball is held on a string and a magnet placed outside of the beaker so that when the nickel ball becomes magnetic it is attracted to the side of the beaker. At that point the test is stopped and the time taken. A general ranking of different quenchants is found below:
Parks 50 and AAA are quite commonly known oils among knifemakers. Parks 50 is a 7-9 second oil, clearly in the “fast oil” category. Parks AAA is a medium-fast oil, taking 9-11 seconds with the nickel ball test. I bought my oils from Maxim but since then DuBois has an easy online store available for these oils.
Quenchfast and Quenchall are offered by McMaster-Carr as “11 second” (Quenchfast) and “28 second” (Quenchall) oils. I asked McMaster-Carr for more information on the oils but the sheet they sent me (hosted here) doesn’t have any more specific information on the nickel ball test ranges. In fact, for some reason the datasheet calls Quenchall a 26 second oil instead. The buckets say Reladyne oil but contacting Reladyne led to nothing; the person I spoke to on the phone didn’t seem to have any information on the products whatsoever and kept asking me for an order number. Of course giving them the McMaster-Carr order number just gave an error in the system.
The Citgo Quenchol 521 came from Jantz. Jantz lists the oil as “14-16 seconds” on their sheet, but the datasheet from Citgo lists the oil as 16.1 seconds, which looks oddly specific when the other products have ranges.
So the ratings of the oils are not quite as simple as I might have liked. There are other products available, of course, notably Houghton makes a range of oils at different speeds. If you have a supplier that regularly sells 5 gallon containers of Houghton oils those are worth looking at as well.
Canola, Motor Oil, and the Inconel Probe Test
Knifemakers looking for oils to use that are cheaper than those available commercially most commonly use canola from the grocery store. However, some will also use motor oil. I found a study on 1045 steel where they found canola to quench more rapidly than motor oil so I am going to stick with canola as my “cheap” quenching option to test.
Data adapted from [1]
Despite quite a few studies that looked at canola oil I did not find any nickel ball measurements. This seems to be because the nickel ball test is outdated and has mostly been replaced by the inconel probe test.
The inconel probe test is similar but the probe can measure the temperature of itself during quenching to generate more information about the quenching process rather than just generating a time in seconds. So you get a curve such as below:
The blue line is the normal time vs temperature curve, and the orange line is the “instantaneous cooling rate” at each position. In other words, the slope of the time vs temperature curve at each position. You can see that the cooling rate is relatively slow at high temperature, then accelerates to a peak cooling rate around 1150°F and the slows down to about 600°F where it becomes more stable. Those three stages are the “vapor blanket,” “nucleate boiling,” and “convection” phases, which are also shown below. I have more information about these stages in this article about hardenability of steel.
Comparing Oils with the Inconel Probe Test
Below shows a range of different oil speeds from Houghton oils, as well as Canola:
Data adapted from Houghton International
The 7-9, 8-10, and 10-12 second oils look relatively similar but the peak cooling rates are slower as the nickel ball time goes up. The 15-22 second oil has a vapor blanket that lasts until a lower temperature, and then the peak cooling rate is significantly lower and at a lower temperature. Canola forms almost no vapor jacket at all and therefore reaches its peak cooling rate at a higher temperature. However, its cooling rate then decreases at higher temperatures, crossing over with the 15-22 second oil at about 1000°F.
However, if we look at water we see that it is much faster than any of the oils, coinciding with the nickel ball results I listed earlier. I have two temperature results listed because water is very sensitive to temperature. The closer the water is to boiling the more tenacious its vapor blanket is.
Water quenching chart from ASM Heat Treater’s Guide
However oil is much less sensitive to temperature. There are small changes in the cooling behavior with temperature but not nearly as extreme as water.
ASM Heat Treater’s Guide
Hardenability of Steel – Jominy
Hardenability of steel also has multiple measures. I first covered hardenability in this article which had an extensive discussion of different CCT curves (continuous cooling transformation) diagrams. Hardenability is how slow you can cool the steel from high temperature and still achieve full hardness. Hardenability is not a measure of how hard a steel can be after quenching, which is controlled by other factors, primarily how much carbon is “in solution” in the martensite. One relatively simple measure of hardenability is the Jominy test where a bar of steel is heated in a furnace and then is placed in a fixture with a water spray that is directed at one end of the bar. So that end is rapidly quenched and the cooling rate is progressively slower toward the other end, which is essentially being air cooled.
Comparing different steels you get a chart that looks something like this:
Adapted from ASM Heat Treater’s Guide
A2 is an air hardening steel so its line is flat; even with slow air cooling it fully hardens. 1095 is a water hardening steel so it only reaches maximum hardness at the position measured directly next to the water quench and the hardness drops rapidly. 5160 and O1 are oil hardening steels though the O1 is significantly more hardenable. 52100 is in between the water hardening and oil hardening steels, and different datasheets will recommend that either can be used depending on the cross section.
Continuous Cooling Transformation Curves
The CCT curves I mentioned above have more information about the behavior of the steel than the Jominy test. It is sort of like the difference between the nickel ball test (limited information) and the inconel probe test (more information). The CCT curve is generated by cooling the steel at different rates and measuring the phase transformations that occur during cooling. This shows the critical cooling rate required to avoid pearlite formation (makes the steel softer) and also the temperatures and times at which different phases will form. There are also certain features that can be different between steels such as some that will form some bainite (labeled B+K) if cooled at an appropriate rate, such as seen with O1 steel below:
Low hardenability steels see pearlite transformation at much shorter times such as can be seen with W2 below:
Different elements added to steel help to suppress the formation of pearlite. These elements are preferentially found in iron carbide so that when the steel tries to form the carbide phase of pearlite it is delayed by the diffusion of those elements. The most effective elements for hardenability are Mo, Mn, and Cr though Ni, Si, C, and V also affect hardenability. W2 has high carbon, low Mn/Si, and a V addition. The vanadium helps to refine the grain size which reduces hardenability (see my hardenability article). O1 has high Mn plus 0.5% Cr so it has relatively high hardenability.
Steels Used in This Study
I chose a range of low alloy steels to test the different oils that I bought. The primary tests I performed were with 1/4″ thick stock. 1/4″ is about as thick as most knives get so if it fully hardens at that cross-section then thinner knives will also work with that particular oil.
The steels above are ranked in order of increasing hardenability based on Jominy data, CCT curves, and otherwise estimated based on the composition using equations found in the hardenability article. W2 has very low Mn and Cr which means its hardenability is quite low. And as mentioned previously the vanadium addition refines the grain and further reduces its hardenability. 1095 has somewhat higher hardenability due to the increase in Mn. 26C3 has very high carbon which reduces hardenability, but the Cr addition helps to overcome that to have somewhat higher hardenability than 1095, at least according to the CCT curves. 26C3 has a similar high carbon+Mn+Cr composition to several steels like the Blue/Aogami series. 1084 is near-eutectoid and higher Mn than the previously mentioned steels which gives it increased hardenability. 80CrV2 has reduced Mn when compared with 1084 but with a significant Cr addition that makes up for it. 15N20 is an interesting case since it has a substantial Ni addition; nickel does not contribute that much to hardenability but 2% certainly has an effect. 52100 is a similar case with relatively low Mn but a substantial Cr addition for hardenability. CruForgeV and O1 combine significant Mn with a 0.5% Cr addition which is why they are the highest hardenability steels on the chart.
The W2, 1095, 1084, 80CrV2, 52100, and O1 were purchased from New Jersey Steel Baron. Most of the steels were produced by Buderus according to the composition sheets, and the O1 was produced by Latrobe. 26C3, 15N20, and CruForgeV came from Alpha Knife Supply. The 26C3 and 15N20 are produced by Uddeholm and CruForgeV is a Crucible product.
Experiment
I tested each of these as 1.5 x 2 inch rectangular specimens. The majority of the tests were with 1/4″ stock though some tests were done from 1/8″. The 1/4″ specimens were held at temperature for 18:30 minutes while the 1/8″ specimens were held for 10 minutes. Parks 50 and water were used at room temperature. The other oils were used at 120-150°F. I ground 1/32″ off the surface and tested the hardness, and then continued in 1/32″ increments checking the hardness each time until the center of the specimen.
1084 and Comparing Oils
It turns out that 1084 was in the sweet spot for comparing the different oils to each other; it shows the clearest differences. This was a little bit of a surprise because I expected 1084 and 80CrV2 to have more similar hardenability since Cr is less effective than Mn for hardenability, so 0.75 Mn should be similar to 0.4 Mn + 0.5 Cr. The results of the different quench media are shown below:
Water led to the highest hardness, as expected being the fastest quenchant. Parks 50 had a drop in hardness at the center of the 1084. Parks AAA had a maximum hardness of 62 Rc near the surface though it dropped to 60 Rc through the rest of the cross-section. Quenchfast (11 second oil) and Quenchol 521 (16 second) had somewhat odd behavior. The Quenchfast started out at higher hardness as expected but then the two oils crossed over at 3/32″ from the surface. I’m not sure what led to that result. The slow oil Quenchall led to low hardness. But the biggest surprise to me was that canola was by far the slowest oil. The overall time for cooling the steel in canola is very similar to the other oils, perhaps even faster. However, the slowing of cooling rate appears to be the deciding factor here. The “pearlite nose” on the CCT curve (the shortest time for transformation) occurs around 1050°F which is where the canola has already slowed down to the cooling rate of a slow oil.
O1 High Hardenability Steel
O1 with its very high hardenability there was no difference between Parks 50 and canola:
There is a small difference in hardness between the two oils shown above, however. This is likely due to “auto-tempering” which is a small amount of tempering that occurs by slow cooling through martensite formation. This explains why the two lines are parallel to each other rather than seeing a drop as would be expected from pearlite formation.
Water Hardening Steels – W2, 1095, and 26C3
I was also somewhat surprised that these water hardening grades did not fully harden in the Parks 50. Parks 50 is often promoted as “approaching the speed of water” but it turns out the word approaching is doing a lot of work in that sentence.
The other surprise here is that the steels are basically in reverse order of hardenability from what was expected on composition. I can’t think of many good reason why W2 with the lowest Mn is showing superior hardenability to the 1095, especially since both are made by the same manufacturer. I would expect the reason for reduced hardenability of 26C3 is because of differences in carbide structure from the manufacturer. Perhaps a follow-up study could be done where I dissolve the carbides and re-anneal them to all have a similar starting microstructure. When I quenched 1095 and W2 in water, however, they fully hardened. I didn’t have the 26C3 yet when I performed this experiment:
Effect of Cross Section with Low Hardenability Steels
Many knives are produced with thinner than 1/4″ stock so I was also interested in how much effect that would have. And some knives have bevels before hardening and so the edges may still harden even if the spine of the knife does not. Of course we expect a faster cooling rate with thinner steel and therefore better hardening.
Canola was unable to harden 26C3, 1095, W2, or 1084, though 1084 was by far the closest of those. I was surprised that canola could not fully harden 1/8″ 1084 since this is such a common oil used by beginning knifemakers. Parks AAA did harden the 1095 and W2 but not the 26C3, it needed Parks 50. Since the W2 and 1095 had higher hardenability than expected in my tests it is possible that other steel from another manufacturer, or the same steel hardened from the normalized condition may require faster than AAA. So for steels in the “water hardening” category I would recommend using water if thicker than 1/8″. Water can be a dangerous quenchant, it is important to avoid stress risers in the knife and keep the grain size small in the steel. Also “hard” water is a faster quenchant than distilled. If 1/8″ or thinner it appears that a very fast oil is effective in these low hardenability steels.
Intermediate Hardenability Steels
80CrV2 and 52100 had somewhat inconsistent hardening results. I believe this is also due to prior microstructure effects. Perhaps if the steel was processed for a finer microstructure in the annealed condition it would show more consistent hardness at the surface with fast oil. A finer microstructure would also reduce the hardenability of the steel so that could be an interesting follow-up as with the 1095/W2. With 80CrV2 the canola did not fully harden the 1/4″ steel and Quenchall was about 2 Rc lower than the other oils throughout. With 52100, canola and Quenchall dropped a couple Rc by the surface which makes it appear that the oils are not fast enough for that cross section. However, with the inconsistent hardening, Parks AAA and Quenchol 521 had somewhat lower hardness at the surface than the center. So it is hard to tell if the canola/Quenchall are insufficiently fast.
With 15N20 the Parks 50 (fast) and Quenchfast (medium) oils behaved similarly, while canola clearly led to softer steel. For CruForgeV all three oils showed similar results, so it seems to be hardenable enough that oil doesn’t matter too much with 1/4″ thickness.
Quenching Too Fast?
A frequent discussion I see on the forums and Facebook groups is whether to use Parks 50 or AAA for a particular steel. These oils are common with knifemakers so it is often a decision between one or the other. Some knifemakers will say that Parks 50 is “too fast” for some steels and you must switch to AAA to avoid reduced toughness. However, this is not as important a decision as is sometimes stated. One thing to remember is that Parks 50 and AAA are not that different from each other; this is not a decision between a very fast and very slow oil. AAA is straddling the line of the fast oil category.
One of the concerns is that the faster oil leads to microcracks and therefore reduced toughness. Microcracks are real but they occur due to plate martensite formation not from overly-fast quenching. Plate martensite comes from very high carbon austenite so this is controlled by austenitizing (how much carbon is in solution) not from quenching.
In a previous study we did on 8670 toughness we looked at toughness differences between Parks 50 and AAA. 8670 has hardenability similar to CruForgeV and is one of the steels that is sometimes said to be a no-no for Parks 50. However, the toughness was the same whether we used Parks 50 or AAA, in fact the Parks 50 was slightly higher but that is probably just due to experimental scatter.
Instead, the concerns with quenching more rapidly are warping and cracking. Cracks are not the same as microcracks. Microcracks are a microstructure-level feature that specific etching techniques are required to reveal. Cracking is on a macro level and are much more obvious. High hardenability steels can be quenched in slower oils to minimize the chances of warping and cracking. However, quenching high hardenability steels in a fast oil is still possible and it doesn’t mean reduced toughness.
Which Oil to Buy?
Because warping/cracking can be reduced through a slower oil it makes sense to have multiple oils depending on the hardenability of the steel. However, if you buy only one oil it should be a fast oil like Parks 50 so that you can quench the low hardenability steels. If the funds are really so tight that you are considering buying canola I would recommend getting the relatively inexpensive AAA instead.
Which Steels Can be Quenched in Slower Oils?
To know which steels can be used with slower oil to minimize warping/cracking I have the following chart that is from my book Knife Engineering. It is an approximate ranking based on hardenability. The steels at the top are expected to have the lowest hardenability and the bottom has a few air hardening steels as examples.
Summary and Conslusions
The biggest takeaway for me is that canola is not a particularly great quenchant. I would highly recommend buying a commercial quenching oil instead. I was also a bit surprised just how sensitive the water hardening grades were to cross-section and oil. I thought at 1/8″ they would harden no problem. There was a pretty sharp transition where 1084 was a step up in hardenability from 1095/W2/26C3, and then every steel with higher hardenability than that was basically insensitive to oil choice. A few potential follow-up studies were mentioned in this article, such as processing the steels for different prior microstructures. We would expect normalized steel (pearlite) or fine carbide annealed structure to have reduced hardenability, which may be significant for forging bladesmiths. The austenitizing temperature can also affect hardenability, typically low temperatures lead to reduced hardenability. And of course we can look at other steels where we think it will be interesting.
[1] Pérez-Ruiz, Eduardo, Santiago Frye Rocha, and Jorge Freddy Llano Martínez. “Performance of Vegetable Oils on the Hardness and Microstructure of AISI 1045 Steel Quenched.” (2019).
This is a very interesting read, but there seems to be something missed because it is so different to my experience. I’ve quenched ~1/8″ 26c3 and 1095 , and 1/8 and 1/4 w2 in canola and the results have been harder than what you found. I don’t have high tech measuring equipment, but good files won’t work on the steel and basic hardness testing files show ~60.
Maybe it’s due to the temperature you’re heating the steel to? I also don’t have precise temperature control, so my pieces are probably being heated higher. Some of your previous work also shows higher hardness from hotter austenitising temperatures.
My canola oil is also cooler than yours was, maybe around 40c?
Your graph from data in reference 1 also looks quite different.
I think something hasn’t been controlled correctly, though I’m not sure what.
When you have a furnace and a hardness tester you can share your results with us and then we can explore potential differences.
Ok, I’ll make sure I have the correct $10,000 worth of equipment before commenting again
Hrrmm, let me get this straight, you’re getting different results but have NO temperature control for austenitizing or the oil temp and NO way to accurately confirm HRC values to the nearest point, yet feel something wasn’t controlled correctly by someone with all the equipment, experience and a PhD? Interesting, I think what will help you out is to branch out into the knife community and find folks that have the equipment that are willing to help confirm things for you. However, you’ll have to keep an open mind and be polite, nobody owes you anything.
It is odd how badly canola did, there are plenty of videos out there of canola perfectly hardening 1084 knives. My guess is that knives are beveled making the edge cool faster compared to a 1/4 inch plate resulting in a hard edge.
Hmmmm….. RC 40 vs RC 60 is such a large difference, it does not take a PHD to tell them apart. Your statement is a little over the top….
Alex got a point. Everybody and their dog are getting good results with canola. They most likely cannot tell between 58 and 63 HRC etc. But 40? That is not really “hard”, that is only a little more than +QT 4140 and can be turned with carbide on a normal lathe. A file will slice right into it….impossible to confuse that with 60+.
There clearly are parameters unchecked by this test. The 1/8″ 1084 in canola was getting hard enough to make a workable knife. 1/8″ is still a lot for anything but a chopping/fighting knife/sword. Even huge kitches knives are much thinner. Then variation in steel composition. Then oil temperature. Canola is quite viscous but looses thickness very quickly with heat. Bunch of German dudes use it at more like 200+°F. Since it has no tendency to boil much, maybe that actually makes it faster. I think alex is on to something. Only proper scientific method can precisely determine which parameter is really responsible, but there clearly is one….
Common sense and good questions always trump fancy equipment. I’m not surprised that canola oil isn’t ideal even where it’s performance is actually competitive, but what about the TEMPERATURE of the oil. Most guys heat it up to 120-160 degrees. Did Einstein factor that in? Maybe I didn’t read closely enough, but I don’t think so.
You didn’t read closely enough.
“However oil is much less sensitive to temperature. There are small changes in the cooling behavior with temperature but not nearly as extreme as water.”
Larrin, are you referring to this quote when you say I didn’t read close enough? Maybe I missed something else. The graph your statement refers to is a reference to oil in general and not canola oil in particular. I suspect there isn’t a huge difference between various oils, but my suspicions are not based on any science. I’m curious about the difference in performance between something like the 60 degree and 130 degree canola. Some claim it performs like an 11-second oil. Many claim they get decent results, even with 1084.
I meant that the article specifies which temperature range was used with the oils, which was 120-150F for everything but Parks 50. That is the typical range for the vast majority of quenching oils.
well, i know what you are saying, some of the better… and worst… performing knives i made was done in a big forge and unknown oil… but 2mm thick steel helped out there. a 1/4 ” bar will behave somewhat differently, than 1 or 2mm edges / pieces of fast and possibly slightly overheated pieces of steel wrt autotempering and cooling rates. your results could point to many things, like grain growth, which would make for higher hardenability, if not hardness. but you should probably take note that there are also a few other ways to compensate for slow quenching, but they all have side-effects. one of the confounding factors are that pearlite would skate a file better than the actual hardness would suggest. having said all this, with your tools a good knife is certainly possible, but i think one should do experiments / tests to eliminate the pitfalls. and improve temperature accuracy.
so if 2.5mm 1055 doesnt fully harden in “supposedly” 8second oil… the fastest i can get here… water is going to be it… only the very tip of the knife hardened…
I plan to get my heat treatment stuff up and running so I’ll let you know what we find for canola oil results as we’ll probably use that a bunch while getting things setup. Won’t be running a study like this though, just some samples before making knives
Thanks for the great study Larrin! What is the effect on steel properties when using a quenchent that is too slow and the steel is not fully hardened but in the target hardness? For example hardening 1084 to 62 and tempering down to 60 vs hardening it to 65 and tempering to 60. How would the 2 knives perform differently?
Cooling too slowly means pearlite/carbide formation for reduced yield strength for a given hardness and lower toughness. It is not ideal.
So one should aim for the highest possible hardness before tempering…in this case, would you recommend a cryo treatment for most steels (even high carbon steels like 1084, 52100)?
I didn’t say you have to aim for the highest potential hardness. If you cool slower and get lower hardness that generally means pearlite formation which is bad. If you austenitize from a lower temperature and quench sufficiently fast, resulting in a lower hardness, that can be advantageous depending on the specifics. Whether we use cryo is a separate discussion.
Thank you so much Larrin for everything you do for the
knifemaker Community!! Great post, very informative!
(Side note get his book it’s awesome!)
Dear Sir,
I didn’t see any information about the degree of agitation, as this influences the cooling rate a lot. As it was a comparative essay, it concludes that all were carried out with the methodology mentioned initially.
And in addition to water, brine is mentioned in several literatures as the one that generates the fastest cooling.
Great article! Some knife makers recommend use Diesel oil to quenching 5160, 52100 and 1095. I used to quenching 5160 and it “works”. After reading this article I was curious about how fast diesel is?
If it were me I would stick with commercial quenching oils.
I know they are better, and have more precision with a lot of data. I’m looking but still not found comercial quenching oil in few liters to buy in my country. This is why i’m looking if have any studies with diesel.
did it burn? how high were the flames?
This research is phenomenal for me especially. My “Magnum Opus” knife is a double edge Arkansas Toothpick made for a fisherman afraid of bears. The blade was 12 inches long by 1/4 inch thick (17″ overall) and I wondered if my 1085 tempered back to 54 would be tough enough if it hit a bone. I had tempered it in peanut oil, not all that dissimilar from canola and your tests show two points of less hardness at .12 deep. I had ground the knife to 90% before HT and it is pleasing to see that knife is softer in the middle, so unlikely to break if it hits a bone.
Thank you Larrin, again superb work. Very helpful article I was just making investigation for buying a furnace and different oil types, in Europe, we don’t have Parks or the price is insane, just found on ebay Rye oil which should be same as Parks.
In the last 2 years I started making my own knives, just for fun, I was fortunate to have an 81 years old blacksmith/knife maker to be my mentor. He divide the steels he uses in to a few categories, steels like GOST 65G or U8 rain water + table salt 5:1 on weight, on German 80CRV2 – 1.2235 and 1.2842 he was using transformer oil + gasoline or diesel, and for 1.2379 and 1.4528 he is using used car oil 0W40. He has a book where he has written his austenitizing temperatures and hold times, but most interesting temperatures of the quench, depending on the steel, what is the thickness, is he using paint for decarb or clay for hamon, usually they varies between 40C to 85C.
For know I prefer more alloyed steels and send them to a knife maker who do plate quench and cryo.
Thank you Larrin, Stay safe!
Hi Larrin
A lot of good information in this article, thank you for posting it. A quick question: Does the Ac1 and Ac3 temps change depending on what phase the steel is in, or do the temps stay constant regardless of the phase. For instance..if the steel is in the martensite phase does that alter the temps at which it fully changes to austenite on reheating ??
I assume that Ac1 and Ac3 temps are dictated by alloy content and not by the phase the steel is in. Is that correct ??
A1 and A3 are not affected by phases because they are the equilibrium terms. Ac1 and Ac3 are on heating and therefore controlled by kinetics where the prior microstructure can matter. Depends on heating rate, etc.
Very interesting..thank you !!
i never heard about this being the case, in theory, that is. think about it, by the time you get to aust. temp. its not martensite any more. but imo you cannot really separate temterature and time. a finer the structure (like tempered martensite or bainite) will austenize faster. however the aust. temp. is very dependent on the heating rate.
In my experience, hardening from a martensite structure will shift the Ac3 temp downward a bit from the specified Ac3 temp even at a high heating… and might shift it down even more from a slower heating rate. I haven’t done enough experimenting to be dogmatic but heating at a high rate to slightly below or slightly above Ac1 and holding for awhile Before hitting Ac3 might change things as well. Interesting subject !!
FWIW I placed an order for 5 gal of Parks 50 through Dubois Chemicals on July 21st. My order still showed awaiting fulfillment over a week later so I messaged them through their website on July 30th and received no response. I again messaged them on August 6th and again no response. I then emailed them directly on August 9th asking for some kind of eta and…no response. My order still shows awaiting fulfillment and it appears basic customer service is as well.
Oh no! Hopefully they get their stuff worked out.
Larrin; my brother in CA uses a water soluble cutting fluid called Formula 77 he mixed a gallon jug with 2 gallons of water in a 4″ square steel tube and has never had W1, W2 or old Black Diamond Nicholson files that are basically W2 crack when quenched in it at 80+ degrees. He told me that he got the idea from the ad of a company online that sold fluids that claimed to be able to water quench any steel by mixing the different formulations they sold, but they didn’t sell to the general public nor in small amounts. I really do wish he could remember the name of the company. Have you heard of this stuff Larrin?
I searched and found it, it is called a polymer quenchant and all my brother did was make his water thicker by mixing it 2 to 1 with a thicker cutting fluid. So somewhere between plain water and Parks 50 I’d guess is the viscosity. I suppose his lucky mix would work well with a lot of steels with less chance of cracking.
https://thermalprocessing.com/an-in-depth-look-at-polymer-quenchants/
I’m familiar with polymer quenchants but haven’t used them myself. Never heard of Formula 77 but I’m not exactly paying attention to the different brands.
The Formula 77 is just a cutting fluid that simply made the water a little more viscous. It was just luck that it worked.
Hi Larrin, have you had any experience with polymer quenching agents? I currently use excelquench 603 (fully accelerated) and it’s great for most things but often distorts thin sections. I like the idea of being able to buy one product and then change the speed with different dilutions, so have been looking at PAG polymers. Best, Gavin
I have not personally used any polymer quenchants.
Almost all sources seem to say that the best steel for a beginner is 1084 (someone usually working with canola oil and a forge with no temperature control) , but here you’ve shown how O1 is the easiest to harden correctly with canola (albeit with a proper furnace). Might O1 be the better choice for a beginner like myself, or is 1084 still the better choice for someone working with basic equipment?
1084 is recommended because of how simple it is and how quickly things dissolve. If you buy some Parks 50 it is probably the easiest.
This is a very timely article, as I am a hobbyist smith looking to move from canola and trying to decide on a quenchant (probably only 1).
I use primarily 80CRV2, 15N20 (standalone and in damascus), 1084 (usually only in damascus) and 5160. The first 3 would seem to benefit from Park’s 50, but since 5160 seems to want a medium-fast oil, would Park’s AAA be the better single solution?
You can quench high hardenability steels in fast oil but not low hardenability steels in slow oil, so if you buy one it would be better to have Parks 50.
I’ll preface this by saying that I’m a total amateur, but did enjoy your book and do enjoy your site and articles. My question here might be so remarkably stupid that I need to be slapped, and if that’s the case, feel free to do so.
My thought is this, could one intentionally use an oil that is slower than “optimal” to achieve desired results in a blade. As an example, The hardness results for 80CrV2 up to .06″ depth show almost identical results to the other oils. Would it be valid for a maker to use a slower oil for the purposes of differential hardening? As long as a blade, say a thicker piece like a chopper had a thin enough cross section, around 1/8″ total thickness (.06 to the center) far enough from the edge to produce optimal hardening at the very edge and leaving the spine softer. This steel and configuration are only used an an example because of the data provided. But if one had the necessary information about desired steel choices and oils, it could be applied to hatchet/axe heads or something of that ilk as well, where a very hard edge is desired, but a softer body.
I apologize in advance if this is a ludicrous thought. I’m not saying I’d advocate for this necessarily. I’m just curious if the idea had any scientifically valid basis, or is merely preposterously moronic.
This was my thought as well… Whether it is possible to achieve good HT on thinner parts of the blade, while thicker parts stay softer inside using slower oil (or oil instead of water). That sounds like very good option for knife makers, I’d say…
So first of all thank you for the test. I am still wondering about the necessity to fully harden / to achieve max hardness given that I will still temper afterwards.
For instance if I quench a steel with canola and yield lets say 61 HRC. With Parks 50 I would get 63 HRC. But I want to have 59/60 HRC after tempering which I can achieve by 400 Fahrenheit according to the data sheet. Does it matter if the steel was at 61 or 63 HRC before tempering if the values are above the final desired value?
Also if I measure the desired hardness after tempering…does it matter which oil was used?!
If the steel is 66 Rc with a fast oil but 60 Rc with a slow oil the hardness is lower because it formed some pearlite which is undesirable. The pearlite would mean reduced toughness at the same hardness. And “soft spots” in the microstructure.
interestingly a steel can be fully martensitic and still have lower hardness if cooled slower. at least thats what all the diagrams out there show. so my question is : what makes the difference?
retained austenite, autotempering come to mind, what else? and how would it affect the result from subsequent tempering? it all very probably depends on the exact composition of the alloy (e.g. types of carbides), austenizing temp and other variables (which ones?)
what else: dislocation density and structure (lath/block size and its distribution) of martensite.
You are correct that RA and autotempering are the likely reasons.
So parks 50 is the recommended oil for 1084 over water, is that correct?
As long as the cross-section isn’t too thick.
How long do you think the nickel ball time will be when using boiling water?
Also, if that time is close to the nickel ball time of various oils, is it possible to use boiling water instead?
The vapor jacket formed in hot water leads to uneven cooling not just slower.
Hi.
Is it possible to convert cooling rate (e.g time-temp) between the “nickel ball time” and other standards as ISO 9950,
ASTM D 6200-01 and ASTM D 6482-06 standards?
I hava a cooling diagram done with the IVF SmartQuench on the fuchs quenchway 22 (https://castrasteel.com/wp-content/uploads/2019/11/QuenchWay-22-at-70-and-85C.pdf) and it would be great to be able to compare the time-temperature with Parks 50 and AAA. I’ve tried to google if there is some way of roughly convert between the different methods with no luck. I understand that there are different probes, but i guess the shape of the different curves looks identical, only the scale is different.
What do you think?
Best regards
Peter
There is no way to convert between them, but the same inconel probe curves are shown in this article for different nickel ball speeds of oils.
this doesnt answer the question, but might be of interest anyway:
https://pdxscholar.library.pdx.edu/cgi/viewcontent.cgi?article=1217&context=mengin_fac
btw, ist interesting to note that clay can slow down as well as accelerate cooling. the japanese used to cover the whole blade because the thin layer at the edge promotes hardening (→steem blanket).
I was the chemist at a transformer plant for years, and used transformer cooling oil for quenching. it is a light mineral oil, someone told me it is similar to #4 fuel oil. (make sue you get newish oil, the really old yellow or brown oil might contain PCB. And if if its old and really heavy- very definitely don’t use it! That could be askarel, not oil)) I used it at about 100 F and it worked well. But i was mostly using O1 which hardens easily. I also used old transmission oil at about 120 F. and it worked well , hardening even 1060 blades. Where I do my forging now we cool in horse-drenching oil, which is a light oil similar to baby oil or transformer oil. it will harden old truck springs, so it must be fairly fast as oils go.
two quick questions- have you ever tested lard? The late pro knifemaker Wayne Goddard had a ‘goop’ which was I think lard with some paraffin wax and hydraulic fluid, or was it brake fluid? it was solid at room temp, so easier to transport than oil. And, do you have an experience with warm water? That is what the Japanese quench swords in. But they lose 1/4 of their blades…
hank you very much for all your information. Joe
Please check toxicity of transformer oil before using it as a quenchant.
Looking at your 80crv2 hardening depth chart it looks like canola is only about a half point softer than parks and harder than quenchall at the .06 inch depth.
Since the center of an 1/8th inch thick blade is .0625, why would canola not work well for 1/8 inch or even 5/32 (.078) inch thick blades where it still hardens better than quenchall at the .078 inch depth?
Thanks
Most of my knives are made with high alloy steels and stainless steels that are air quenched I’ve always used plate quenching with aluminum quench plates to avoid warping and boost quenching speed. If I used copper quench plates do you think it would increase the hardness very much by how much more thermal conductivity copper has?
What are your thoughts regarding polymer quenchants for knifemaking? I use 1095 and W2 with differential hardening and find too many blades crack in the quench. I have houghtoquench K, a fast oil, which still provides a nice hamon, but I wonder if a polymer quenchant between this and water would be better?
I’ve never tried polymer quenchants
I know this is an old article, but I love this article because I love data, particularly practical data. Having noticed some interesting results with canola (that seem to contradict some people’s real-world results), I wondered about the consistency of canola oil between manufacturers. While I don’t have direct data, I think it is worth noting that the reported smoking point (an important trait of cooking oils) is highly varied for canola oil at 375F-450F. This suggests significant differences in oil composition, i.e., the specific proportions of various fatty acids. It would be interesting to see if different seed oils have different cooling speeds, as well as if different companies’ canola oils have different cooling speeds.
Nice article. Most of my work is in air-harden steels, but for oil harden steels I use a layer of oil (motor, canola or other) on top of water. This allows me to control the cooling rates by adjusting the thickness of the oil layer. I had good result with this technique.