Okay, I'm convinced -- I'm going to begin building a proper quench tank and find some Parks #50. Actually, is Parks the proper quenchant for O1? (And can someone suggest a source? I can never find it when I go looking.)
This discussion clears up some things I've experienced that I believe will virtually disappear when I get a better system going. Thanks a million Kevin, this is always good stuff.
Thanks! Just the ticket.
Dave, any of the medium speed quenchants will work for O1, Chevron, Texaco, Tough-quench, Houghton makes several and then there is AAA by Park Metallurgical. #50 is actually overkill for O1. I am glad to hear of your decision but this thread did not have the intentions of suggesting any quenchant over the other (certainly not a particular brand, especially one that is a PITA to get). I believe you did exactly what I hoped could be done from this thread, that is make an informed decision based upon what really goes in on quenching and the factors that make the whole operation more pleasant and successful. To be certain, there are some vegetable oils and automotive products that can fully harden many steels, particularly one like O1, but as I keep reiterating, simple cooling power is but one consideration that we should look at when determining what will accomplish our goals most effectively. When we approach a grinder, metal removal is our objective so why do we not just use a 36X or 24X belts exclusively? Instead we have wide ranges of grits and abrasive materials we work with to achieve our goals, much the same if cooling power was all that mattered then we would need nothing more than brine for quenching.
Which brings me to another desirable property of a quenchant…
Final blade surface and cleanup. Just a few days ago I got a call from another maker fro advice on quenching, he reminded of this feature when he noted how much cleaner his blades come out of the quench now that he is using a well formulated quench oil. Any oil that comes into contact with glowing hot steel will have abrupt chemical reactions to it. Many organic oils will break down and deposit bits of nasty crust and scale on the blade (just ask you wife about this the next time she is scrubbing on a blackened pan that had oil burned in it). Often if the chemistry was not designed to remain neutral under the extreme heat there will be staining of the steel as well. Often when a really good quench oil is reaching the end of its life it will become evident by the increased sating of the quenched parts. I have also seen some oils that can have a carburizing or decarburizing effect on the steel and leave a nasty marbled surface of high an low spots on the blade that requires quite a bit of effort to return to smooth, I am certain others have seen this annoying issue before.
A good quenchant will account for this and have much thought into how true to the original finish the heat treated part will be, we would be doing ourselves a favor in adding it to our considerations as well.
Safety. Two things come to mind when considering safety, the threat of fire and the possible risks involved with the vapors released from the quenchant. Both of these are heavily dependant on the vapor forming tendencies of the oil itself. What is the vapor point of the quenchant? What is the flash point of the quenchant? Will filling your shop with heavy amounts of that vaporized quenchant be good for you? Will the quenchant have a greater change of bursting into flames any time you use it? You certainly won’t get a good quench if you are more concerned about the flames going up your arm than you are about the quenching operation.
I get nervous about many automotive products and the vapors they could release when used in this manner. Even good commercial quench oils are not the healthiest stuff to take into your lungs, but they were designed not to be there in the first place. This is where we need to determine if our methods and operations are well matched fro our quenchant. For example, edge quenching has an inordinately high chance of leading to heavy smoking or flashing, it may be best to avoid oils that will form heavy vapor and have hazardous components in that vapor. Most commercial quenchants were not designed for this type of use and I try my best to discourage people from wasting their money and lungs with a dedicated quenching oil if this is the method they plan to use.
Park’s #50 has a surprisingly low flash point, yet its vapor tendencies are so low that in all the years I have been quenching into it I have
never had a flash with a full quench.
Another example of poorly matching of methods with materials is simply assuming that one can heat any oil to 400F and perform marquenching. The obvious danger of this is introducing a 1450F+ blade into an oil that is already a few degrees from its vapor or flash point. Some people will examine this just enough to choose an oil that naturally resist flashing, but then totally overlook the fact that most oils have a “sweet spot” around 130-150F and then take a significant nose dive in cooling ability above this range. I have seen some oils virtually loose their thermal transfer rates above 225F. Industry spent much time an effort to develop oils specifically for marquenching, and for good reason, it is a very special oil that can handle prolonged periods at 400F+ cool steel well and not burn the heat treating facility to the ground. This is one area that is most prone to misinterpretation of the results, many blades cooled in hot oils not designed for marquenching are just full of fine pearlite but have enough martensite to skate that file. If one looks closely they will often see a faint hamon about ¼” to 5/16” from the edge of blades done this way, anything outside of this line is nothing but fine pearlite and within that edge zone you will find a mixture. I include this last part to implore people to ask themselves if endangering their shop and their life is worth a partially martensitic edge.
400F+ potassium based salts are treacherous enough, but they at least will not burst into flames when you put a blade into them.
) with great success. Is that what you're referring to above? If so, I'll add a suitable quantity to my next order. Getting that stuff is very straightforward.
