Heat Treating Questions, about to make my first attempt

So I have done as much research as one can. Watched videos, read posts from countless forums, etc.. Watched Tracy's video too...

Still I have a few questions...

I am HT CPM3V, at .190 thickness for my blade as well as a back spacer at .230 thickness.

1. I am starting off with a stress relief bc I do a good bit of manual milling on the blade. Do I need to wrap the steel with foil for the stress relief? I am setting the oven at 1200 degrees and soaking it for two hours then letting it cool slowly to room temp. Also, should I put the steel in the oven while it heats to the set temp? I have read that decarburization begins to occur around 1292.

2. For the preheat.. (Steel is in SS Foil now) Should I set the pouches in the oven while it climbs to set temp, or should I wait till it reaches set temp then place the pouches in? I have read that it is better to set them in the oven while it heats to the set preheat temp and then equalize at the set temp. I have read it done both ways. Why is one chosen over the other?

3. For the "equalize" part of the preheat. I have read that a good rule of thumb is 1 hour per inch of material. If that is true I would need about 11-12 minutes to equalize at the preheat temp for the blade and about 14 minutes for the back spacer. Is this thought correct? Longer, shorter? Will I be okay if I just preheat the blade longer so that the back spacer is properly "equalized"?

4. The cryo treatment. After the steel has quenched in between my aluminum plates, removed from the pouch, how cool does the steel need to be before I can submerge it in the LN? 176 degrees? 150 degrees? 125? Room temp? I have read that the quicker it can get in the cryo the better off you will be.

5. The temper.. Same question as with the preheat. Should I set the steel in the oven while it heats to set temp, or wait for it to reach set temp then place steel in the oven?

Looking forward to learning more about this process and actually HT'ing my first steel. I just want to get the best possible results, so I ask as many detailed questions as possible. Thanks guys!!!!
 
Last edited:
My advice would be to follow the "spec sheet"..... https://www.crucible.com/eselector/prodbyapp/tooldie/cpm3vt.html

Chances are good that things will not be "perfect" the first time out. You're likely going to have to do a bit of experimenting to get the results you desire.

I can offer you how I would do it..... but.... most folks have specific "tweaks" they use during the process..... just remember there is no "one size fit all" when it comes to heat treating.

I always place the blade(s) in foil, place then in a rack so they are sitting with the spine up and the edge down. I then start the oven and allow the blade(s) to be there as the oven runs it's cycle. 11-12 mins WILL NOT do the job for equalizing. For 3V the recommended time is 20-45 MINUTES.... I usually will got with the higher end, depending on the steel and experience.

LN can be a tricky thing....you have to realize that you're dealing with something that is -320F..... if the steel isn't introduced SLOWLY, or it's too warm, at the very least you will "shock" the steel, and at worst shatter it. I always run a blade through a "snap temper" at least once, and allow it to cool to room temp before going to the LN.

When it comes to tempering, I always preheat the oven first..... then put the blade in there, and allow it remain a full two hours. Then remove, allow to cool to room temp in still air, and repeat. (3V REQUIRES three tempering cycles).


As I said, don't expect things to come out "perfect" on the first try. There are tons of variables, and it's not uncommon to sacrifice a few blades learning the process, and more importantly, discovering the "tweaks" that work best for you.
 
Ed,

Thanks for the clarification on the equalizing time. I understand that there will be some experimenting with this process, just as there has been with every other part of this knife making journey. I am just wanting to shorten the learning curve as much as possible with help from my fellow knife makers.

Regarding the LN, that is why I asked about how hot/warm the steel could be to safely put it in the LN without it damaging the steel. I will consider a snap temper. Can you provide what temperature and time you use for the snap temper?

Any reason why you don't put the blade in the oven as it heats up for the temper cycle?

Thanks!!
 
Last edited:
Can you provide what temperature and time you use for the snap temper?
Since the tempering temp for 3V is so high compared to carbon/tool steels, I would go with 500-600F for the snap temper. The way I work LN is a snap temper, then overnight in the LN, take it out and put the blade between two piece of kawool, which forces it to warm up to room temp slowly. Then the blade gets 2 more tempering cycles at 25-50F HIGHER then I would temper a blade that hasn't been soaked in LN.

Any reason why you don't put the blade in the oven as it heats up for the temper cycle?

For me it's the fact that most ovens will fluctuate up/down a bit when heating up...some much more then others. If I put a blade in an allow it to heat up with the oven, the temp will generally "spike" ABOVE what I want for the tempering temp...meaning that it softens more then I want. I generally turn the oven on and set the temp, then let it cycle for approx 1/2-1 hour.....this gives the oven temp time to stabilize, and helps minimize and wild fluctuations of temp.
 
Thanks for sharing the info on the Snap Temper.

I was under the impression that bc you are using LN during the HT process, the temper temps are much lower. As in 400 degrees compared to 950-975 without the use of LN.

It makes sense about the ovens fluctuating. Hopefully the EvenHeat oven I purchased will minimize that with proper setup and programming.
 
The exact temp of the "snap" temper depends on the given steel. 3V is sort of a "special case" because the tempering temp is so high in comparison to things like 1080/84, 5160, 52100, etc., which are usually tempered in the 400F range +/-.
 
Back
Top