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Quench speeds?
- Thread starter John L
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I use the industry terms to describe the hardenability of steel based upon Jominy and other standards which divides the steels into categories of how deeply they will harden into a standardized thickness, this gives values that correspond to “shallow” hardening (only capable of hardening on the outside if a 1” diameter piece) or “deep” hardening (capable of hardening to the core of the same). This terminology gets away from “water” hardening versus “oil” hardening, which is deceptive for thicknesses in our work with knife blades since many “water hardening” steels can quite effectively be hardened in fast oil in cross sections of ¼” or less. Also, in these thinner sections water can be overkill that often leads to undue stress, distortion or cracking.
In light of this, proper quenching should not be measured in quench speed alone, since the ideal quench should be one that will fully harden the given steel as evenly as possible without overstressing things unnecessarily. If all that mattered was the fastest possible quench, a 9% brine solution would be all we would ever need for any steel and this is certainly not the case.
Shallow hardening steels lack alloying such as chromium or heavy manganese (above around .9%) to retard the formation of soft structures or phases that may form in quenching and thus require faster heat extraction to avoid them. Steels in this category would be:
1070
1075
1080
1084
1095
W1
W2
And a few more I am not thinking of
Deep hardening steels have the aforementioned alloys and other additions to partially or totally retard the formation of soft phases (pearlite) in the quench and thus allow much more time for cooling for total hardness. This feature was developed for the ability to make more complex shapes and not have them self destruct in sever quenching operations by allowing for more gradual, and thus more even, cooling. Of course alloying has many other functions and often will also offer this benefit as a side effect. Just a few examples of deep hardening steels would be:
5160
52100
6150
O1
L6
Etc…
Carbon, up to around .8% only determines how hard the steel can get under full hardness but it does not determine hardenability itself, so one can have a steel of .9% carbon and have it be just as shallow hardening as a steel of .7% carbon if the other elements are missing.
Originally the shallow hardeners were limited to water quenching, but quench oil manufacturers have developed oils capable of very quick heat extraction, even approaching water, that still produce the gentler and even cooling effects of oil. So there are fast quench oils specifically designed for the first group and medium speed oils that work quite well for the second group.
The simple designation of “fast” or “medium” speed oils cannot always tell us what we need to know for selection and the most common information we get is quench speed in seconds. This has to be taken with a large grain of salt as well, however. Many quenchant producers use hot wire tests for assign quench speeds while others may use the nickel ball test and thus the numbers can be like apples and oranges. Generally the medium speed oils are like 12 seconds or more and the fast speed stuff will be as low as 6.5 seconds.
I hope this helps.
In light of this, proper quenching should not be measured in quench speed alone, since the ideal quench should be one that will fully harden the given steel as evenly as possible without overstressing things unnecessarily. If all that mattered was the fastest possible quench, a 9% brine solution would be all we would ever need for any steel and this is certainly not the case.
Shallow hardening steels lack alloying such as chromium or heavy manganese (above around .9%) to retard the formation of soft structures or phases that may form in quenching and thus require faster heat extraction to avoid them. Steels in this category would be:
1070
1075
1080
1084
1095
W1
W2
And a few more I am not thinking of
Deep hardening steels have the aforementioned alloys and other additions to partially or totally retard the formation of soft phases (pearlite) in the quench and thus allow much more time for cooling for total hardness. This feature was developed for the ability to make more complex shapes and not have them self destruct in sever quenching operations by allowing for more gradual, and thus more even, cooling. Of course alloying has many other functions and often will also offer this benefit as a side effect. Just a few examples of deep hardening steels would be:
5160
52100
6150
O1
L6
Etc…
Carbon, up to around .8% only determines how hard the steel can get under full hardness but it does not determine hardenability itself, so one can have a steel of .9% carbon and have it be just as shallow hardening as a steel of .7% carbon if the other elements are missing.
Originally the shallow hardeners were limited to water quenching, but quench oil manufacturers have developed oils capable of very quick heat extraction, even approaching water, that still produce the gentler and even cooling effects of oil. So there are fast quench oils specifically designed for the first group and medium speed oils that work quite well for the second group.
The simple designation of “fast” or “medium” speed oils cannot always tell us what we need to know for selection and the most common information we get is quench speed in seconds. This has to be taken with a large grain of salt as well, however. Many quenchant producers use hot wire tests for assign quench speeds while others may use the nickel ball test and thus the numbers can be like apples and oranges. Generally the medium speed oils are like 12 seconds or more and the fast speed stuff will be as low as 6.5 seconds.
I hope this helps.
Last edited:
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As for which oil for what steel, a typical answer given for fast speed oil is Park's #50 and a medium speed oil for the deeper hardening steels is AAA (both are specially formulated quenching oils).
For some steels like O1 that are deep hardening, you can get by with mineral oil, canola, etc, though they may not be as stable over multiple quenches/knives as the heat breaks them down. I've not tried it, but I've heard discussion about 1084 hardening just fine in something like canola because of typically thin cross sections. I haven't tried it because I have and use Park's #50 for 1084, 1095, W2, W1, etc. I use AAA for O1 and 52100.
--nathan
For some steels like O1 that are deep hardening, you can get by with mineral oil, canola, etc, though they may not be as stable over multiple quenches/knives as the heat breaks them down. I've not tried it, but I've heard discussion about 1084 hardening just fine in something like canola because of typically thin cross sections. I haven't tried it because I have and use Park's #50 for 1084, 1095, W2, W1, etc. I use AAA for O1 and 52100.
--nathan