Cryogenics is a complicated process...
Hello Frank,
I wish it were that easy!
Unfortunately, you cannot achieve the benefits of deep cryogenic treatments by soaking a tool in liquid nitrogen for a few minutes. Deep cryogenic treatments do not expose the material to the liquid, only the gas. The process of deep tempering is achieved over a long period of time and requires a computer to achieve the maximum benefits the process can deliver. I recently completed a three and a half year test of cryogenically treated woodturning and woodcarving tools in my studio. I'm familiar with the process, so I will give you a snapshot of a typical (may vary based upon material being treated) deep cryogenic treatment cycle:
A standard deep cryogenic cycle consists of several steps, each "stage" or (ramp) is carefully monitored by the computer.
1.) The initial procedure is called a ramp down. This will bring the temperature of the part being treated down between -300F to -323F over a six to ten hour period of time. The slow ramping is designed to prevent thermally shocking the part. If you simply dip a part in liquid nitrogen, you can create a temperature gradient that can lead to stresses in the surface of the metal as it reacts to the sudden change in temperature. This can lead to cracking on the surface.
2.) The second procedure is called soaking. Typically, this will last between eight and forty hours, with the piece being exposed to the nitrogen gas at -300F to -323F. This is the point where things are starting to change in the metal (like the precipitation of fine carbides and making a stronger crystal structure) and it takes time.
3. The next procedure is called ramping up. This brings the temperature of the part back to room temperature over a period of eight to twenty hours. This must be done slowly to prevent thermal shock and cracking.
4. Next up is a temper ramp up. This slowly ramps the temperature up to a preset level over a specific period of time, much like the tempering process that you would use during quenching and tempering in heat treating. Typical temperatures reach between 300F up to 1100F, depending on the specific metal and the metals hardness.
5. Lastly, we have a temper hold to complete the process. This insures that the tempered part has received the full benefit of the tempering cycle. This will last around three hours, give or take - depending on the thickness of the part. Some pieces may require several of these holding cycles.
As you can see, it's a long and complicated process. However, it can do magical things to many different types of materials. Take care and all the best to you and yours!