01 heat-treat quenching oil

[Kevin R. Cashen]

The topic always begs the question- why did they develop quenching oils? If there is no difference between mineral oil and canola oil and a quenching oil, why was all the effort and resources spent on improving them for quenching? And why would successful entities in industry get fleeced by paying people more for quenching oils? Such corporations don't stay in business by wasting money with no true benefits, a successful business would certainly cut the cost of quenching oil for mineral or canola oil if there were no difference.

I would hazard to guess that our steel is more iron, percentage wise, than a quench oil is just mineral oil, and yet are we willing to say that fraction of a percentage of carbon is inconsequential to the outcome of the knife? Very small applications of chemistry results in very profound changes in material properties, we eat sodium chloride everyday but would any of us care to apply the pure mineral or canola oil logic with ingestion of either of the basic ingredients in table salt (well minus the iodine, so that eventually if the toxic gas or flaming metal doesn't kill us, we can have goiter with the omission of that nonessential additive). I have used just about every liquid out there for quenching and when I finally quit resisting and tried a liquid made specifically for the task the differences were amazing and I never looked back. I hear the same thus far from everybody who has went to one of the good quenchants.

Fortunately we are discussing O1 here. O1 has a very forgiving cooling curve which opens it up to a very wide range of quenchants (the trade off, of course, is that it does have a stricter need for proper and accurate soak times, but that is another thread), so one will get the necessary quench speed from almost any oil. But then there are about a dozen other factors critical to proper quenching, however for simplicities sake I will stick to quench speed and say that the blade would survive the canola or mineral oil. The ideal is to find that sweet spot between forming any structures other than the desired martensite and needlessly shocking the steel with quench speed overkill; not too fast, not too slow, but just right. It is a mistake to approach quenching simply as the fastest cooling possible.

And by the way don't try to get the Park's stuff directly from Park's, you won't get anywhere, but it is sold on the secondary market. The good news is that there are plenty of other quenchant makers out there who will be happy to sell you some. Houghton international is very cool to deal with have a very wide section of quenchants (even one that is based on canola oil- please read "based)". Many of the quenchants sold by smaller companies are acutally reapackaged Houghton products. The point is that you do not give up on looking for ways to improve you process and ultimately you knives, there is always another level to take things to and when we stop seeing that we are done growing. I think it is sad when I see a pretty good smith who has went 20 years without any advancement or changes in what they do leaving so much potential wasted.

[sdcb27]

Well said Kevin

[dbalfa]

Kevin - in your opinion, does container size make much a difference- regardless of the quenchant? *assume the correct temp is maintained*

[Kevin R. Cashen]

Quenchant container size, for me, is like hard drives or RAM you can't have too much and you can't go wrong with going with the most you can afford (financially or space wise). Agitation is one of those things that is hard to convince many smiths of the importance of, if they have heat treated certain number of blades without disaster holding the blade stationary in still oil. But improving the process is not about simply avoiding disaster and looking no deeper out of insecurity.

Thus my reason, beyond constant temperature is room for agitation. Now of course I realize that in a field where convincing folks to obtain a bucket of proper quench oil can be like the Battle of the Bulge, that suggesting the construction of pumped oil circulation systems is really pressing my luck. But short of this anybody has the means and budget to agitate by moving the blade through the oil, and the more space you have to do that, the better your quench will be.

Oil or water based quenchants will form vapor jackets at any temperature and the easiest way to defeat this is to agitate. Everybody owes it to themselves to give it a try sometime with a shallow hardening steel and see how much deeper the hardening is with motion than without, and the idea that moving the blade in at all causes warping is pure myth. Evenly killing that vapor jacket will reduce distortion significantly. I have traced distortion back to countless variables that happened well before I put the hot blade into oil- grinding technique being perhaps one of the biggest.

So for vertical quenching a tube with enough height to stab and pull, stab and pull, is very good. For horizontal, a trough with the room to slice the liquid in a tip to tang motion is good. One need not go crazy, I have gotten by with a trough a Little under 2 feet for 10-12" bowies, just enough to outrun that vapor jacket and expose the blade to fresh oil.

[sdcb27]

I to found that more oil ment more weight and mass pushing against the blade helping to break up the vapor barrier. 2 gallons seemed at the edge of to little and over 3 seemed like over kill. At least no noticeable difference from 3 to 5 gallons but for sure under three there is for me with the steel I use.
Note: Agitation given for all blades as not doing so there is a noticable difference no matter how much oil I have experimented with.