HTS: Guide to Heat Treating Steel for knife and tool makers

Saturday, December 18, 2010

Properly Heat Treating ATS-34 using an oil quench method

ATS-34 Oil quenching process. The oil should be warm and thin at the time of quenching it should also have a safe flash point. Some prefer to use olive oil rather than petroleum based quenching oils because of it's higher flash point. It is common practice to have one gallon of quenching oil for each pound of steel. To warm the oil before quenching simply heat a piece of scrap steel and drop it into the oil. 

To begin...

wrap the piece in stainless tool wrap and leave an extra two inches on each end of the package (This will be for handling purposes).  A double wrap is suggested for this grade.  The foil should be double crimped around the edges. Note: be careful to not tear or puncture the wrap!

 Once wrapped place in the furnace and heat to 1900F. Upon reaching this temperature immediately begin timing the soak for 25 to 30 minutes. (Soak time is the amount of time the steel is held at the desired temperature; which is in this case 1900 degrees Fahrenheit)

Note: soak times will very depending on steel thickness. See formula at the bottom of page.

When the soak time is complete, very quickly but carefully take the package out with tongs, and hold over a quench tank then snip the end of the package to allow the piece to drop out in the oil. Be sure to have some kind of wire basket already placed in the quench tank to raise and lower the piece in the oil rather than have it lie still. This must be done to ensure a proper quench.

NOTE: For full hardness; it is critical that the piece enter the quenching oil as quickly as possible after taking them from the furnace!

If treating a knife carefully remove it from the tool wrap and quench holding it at a non crucial point such as the rear of the tang making sure to move the blade up and down in the oil as mentioned above for a proper quench.

Once the piece has been quenched down to around 125F begin the tempering process. To temper the piece it must be placed back into the furnace at 300F. Once 300F is reached allow them to soak for 2 hours. Then remove the piece and allow it to cool to room temperature.

Tip: Some have successfully used toaster ovens to complete the tempering cycle.

To begin the second temper place the piece back in the furnace and soak for 2 hours this time at 275F. Once this step is complete remove the piece and allow it to cool. It should now be approx hardness 60 RC. 

Tip: The piece can be placed in dry ice for an hour this will add more stability and even a little extra hardness

Note: Pre quench soak times can very to some degree. However, commonly one can figure about 1 hour of soak at hardening temperature per inch of steel thickness
1 inch = 1hour 

1/2 inch = 30mins

1/4 inch = 15mins

1/8inch = 7.5mins


  1. this is some really great info and a great blog!!! thanks much...

  2. The only soak times I have ever found on steel were for machine part specs from naval spec books. The soaking was for steels that were incredibly large machine parts, anywhere from two inches thick to two feet thick. Working down from these specs to knife thickness, the math says that I can quench immediately upon reaching critical temperature using almost any kind of steel,including stainless. Soaking upon experimentation causes continual oxidation and loss of steel, no matter what median I use to heat the blade. I have also found that doing no soaking gives me a harder and more durable blade. I have however only been forging for 27 years so there are still things I don't know. What are your thoughts on my findings?
    Charles Adams

    1. Charles you are correct, soak times are really for cross sections not weight. Once the steel meets the temp requirment all the way through it should be quenched.

  3. Thanks for sharing the information ATS-34 Oil quenchingprocess.

  4. I have been using this method for over 30 years with great results every time using my trusty Paragon oven Rudy Pattay PATTAY KNIVES