copper plate quench

Discussion in 'Heat Treating Forum on KnifeDogs' started by ironbasher, Dec 29, 2010.

  1. ironbasher

    ironbasher Guest

    Hi everybody, I know alot of people quench their air hardening steels between copper,aluminum or steel plates. but of late I have started to hear of many bladesmiths also using this method on oil quenched steels, is there any factual benefits to this or is it merely the latest "flavor of the month"? I would'nt think they would be as fast as a liquid. thanks for any and all input. ironbasher
  2. BossDog

    BossDog & Owner

    copper is a faster heat conductor than aluminum. It would be more widely used than aluminum except the cost is fairly high. I've not heard of too many using it for oil quenched steels but I know it's been done.
    Last edited: Dec 30, 2010
  3. Darrin Sanders

    Darrin Sanders Moderator

    I have heard of plate quenching O-1 but have not tried it myself. But if I remember correctly it was only done with 1/16" thickness. Probably wouldn't work on anything thicker. I think he only did it to control warping.
  4. Kevin R. Cashen

    Kevin R. Cashen Super Moderator

    I too have heard of enough people doing this that it concerns me. The logical fallacy of appealing to common practice is one of the most common pitfalls in all of knifemaking. The error of assuming that because a number of people do something that is must be correct should be obvious, but this is not the case on our craft. The other odd thing about our craft are the number of methods that are adopted for various reasons that can be at odds with the actual purpose of the operation, but when the exercise doesn't result in obvious disaster it becomes validated and the practice gain acceptance. If your priority gets skewed from knife edge properties to keeping things straight then any method that produces a straight piece of steel can be called a success. So many practices have gained acceptance because we simply changed our priority and redefined success.

    We have three categories of steels we typically work with, "water hardening", "oil hardening" and "air hardening". Plate quenching was adopted long ago for air hardening steels and is slightly faster than air but is not a liquid medium. One can say that very thin sections can be done but very thin sections of O-1 can be left in the open air and get very hard, and with L6 in thickness of 1/2" to 5/8" I can get a consistent 61 HRC from just throwing it on the floor while hot, but I would never heat treat a blade this way. My famous killer lawn mower blades showed me this, I started out just welding L6 inserts in and then using air cooling since I could get a 61-62 with this down and dirty heat treat (it's just a lawn mower blade, after all). No matter how well I tempered these blades the inserts would break out in use. When I took the time to properly heat treat (oil quench) and temper the inserts I never had to replace them again and have been grinding up anything in my path with glee.

    There are reasons the specific heat treatment of specific steels were developed, other methods may "look" good but it is what goes on inside that steel that matters. Yes there are more people playing with plate quenching steels that really should be quenched in oil, there are also a lot of people who swear by gooey lard quenches, but since I don't work with air hardening alloys I will not be quenching any of my blades in either.
    Last edited: Dec 30, 2010
  5. tomwatson

    tomwatson Well-Known Member

    You should add another quench medium to the three you mentioned. A brine solution. Water is a quick quench medium, but the water can vaporize off the steel so fast that the bubbles created can hinder cooling by forming pockets of air on the blade. The brine solution reduces this by not creating very many bubbles. Plate quenching has been around for a while and is appropriate for air hardening steels of higher alloy content at .250" and thinner. Thicker sections need an oil quench in a circulating oil bath. The whole point of a quenching medium is to have a velocity of quenching that matches the heat treat chart for a specific steel and can get the hot steel below 400 degrees F in the time specified on the chart. This is usually a couple of seconds. Plate quenching should not be used on any steel in any thickness that would make it prone to cracking. This type of quick quench is more for the higher alloyed steels.
  6. seved

    seved Well-Known Member

    A friend forging O1 for me, and i have to anneal it every time before i can drill it. But i have never cheched the hardnes before i annelead it.


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