Those are NitroV stainless knives that have been hardened at 1955F/1070c for 7 minutes and plate quenched. I put them in the shed freezer for a 1/2 hour to bring them down in temp to below zero before they go in the liquid notrogen @- 320f / -195C for an hour to do the cryo quench then after they come back up to room temp are into the tempering oven for 2 time 2 hour cycles at 339f / 165C
The cryo quench is only really benificial for the stainless. The knife steel nerds have done extensive testing of most of the commonly used steels for knifemaking and so studying their findings has bought about my process in line with their recomendations.That’s quite a process. Impressive system. Did you arrive at that process over time? Trial and error? (Besides the leg work and study of course)
I understand the heat and oil quench process some but what does the cryo quench process add for you? Is that more for stainless?
The cryo quench is only really benificial for the stainless. The knife steel nerds have done extensive testing of most of the commonly used steels for knifemaking and so studying their findings has bought about my process in line with their recomendations.
Nitro-V is a recent (2017) stainless knife steel. I have information on how it compares to other steels and how to heat treat it.knifesteelnerds.com
these are the relevant sections
Hardness of Nitro-V
Like other stainless steels Nitro-V has high hardenability so it can be cooled in air or plate quenched for hardness. Oil quenching is also possible though plate quenching is good for helping to maintain flatness. I recommend cryogenic processing for maximizing strength when heat treating. You can read more about cryo here: Part 1, Part 2, and Part 3. For heat treatment experiments on Nitro-V I austenitized for 15 minutes at 1850, 1900, 1950, and 2000°F followed by plate quenching and then immediately going into liquid nitrogen for an hour. The steel was then tempered at 300, 350, 400, or 450°F. Peak hardness was achieved at 1950°F, and remained flat to 2000°F. Therefore I recommend austenitizing no higher than 1950°F. The higher 2000°F has the same hardness despite the increase in hardness of the martensite because of an increase in retained austenite. That means that the 2000°F austenitize likely leads to a decrease in strength and toughness. Heat treating without cryo would mean a reduction in hardness and a reduction in the peak austenitizing temperature. I recommend at least going into a household freezer directly after quenching to reduce the retained austenite as much as possible. To check your heat treatment against mine, it is best to perform heat treatments from a range of austenitizing temperatures and going straight into the cold treatment used, whether freezer, dry ice, or liquid nitrogen. Check hardness and austenitize no higher than the peak hardness.
The peak hardness of Nitro-V will reach about 64 Rc
I next produced toughness specimens using the 1950°F austenitizing temperature plus cryo but tempered at 300 and 450°F to test the effect of tempering temperature. I used 4 specimens for each condition and these were machined by me. The 300°F temper led to increased hardness with a reduction in toughness, as expected. The 450°F temper led to a reduction in hardness and toughness, so it is not recommended. This reduction in toughness was somewhat unexpected because tempered martensite embrittlement is not expected with this tempering temperature in high alloy steels. I don’t know if a 400°F temper would see similar results. But I can’t recommend tempering higher than 350°F right now because I don’t know where the reduction in toughness takes place.
Nitro-V has very good toughness compared with other steels. Nitro-V would be well suited to knives requiring good toughness.
Overall the properties of Nitro-V are expected to be similar to AEB-L with perhaps an improvement in corrosion resistance. I got good results in heat treating by austenitizing between 1900 and 1950°F for 15 minutes followed by a plate quench and a cryo treatment. Temper between 300 and 350°F depending on desired hardness.
I recieved the steak/table knives the other day, in plenty of time for Christmas! My only regret is I didn't jump on the opportunity and buy both sets!!!After the hunt is done and the meat processed and bought to the table a good knife is needed to help enjoy the fruits of your endevours.
I have been working on a table knife/steak knife design over the last couple of years and now have it where I convinced that it is worthy of presenting to my customer base. There is a His'n'Hers in the pair with the Hers being a fraction shorter in both handle and blade. Blades is NitroV SS with the first pair being spalted buckeye and the second pair with maple burl.
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These are some of the trial knives I have done and rejected over that time. Make one and use it for long enough to find fault and the make another to try.
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The top one with linen micarta was the first one of the new design that I was able to use for over 6 months without feeling the need to alter any aspect of it. There are many instances where the main table kn ife may also be needed for the secondary use as a side polate knife for the spreading of a bit of butter on a bread roll etc etc so the forward third of the blade came in for a lot of trialing to get to this point (pun not intended) where it will comfortably accomplish this task as well as it will perform on a steak or clean up round a chop bone. The lower one with the stone washed blade and impala jigged buffalo horn in my traveling knife and stays in the truck for when we eat away from home. Hotel staff have been intrigued to see someone bring their own knife to the table but a comfortable knife is always preferabvle to some random knife offered at another table.
Appreciate that Bob. I have just heat treated another 3 pair for the ready drawer so they will just need handle choices. Will get more done when I get caught up on the order bookI recieved the steak/table knives the other day, in plenty of time for Christmas! My only regret is I didn't jump on the opportunity and buy both sets!!!
Garry let's see what the next 10 or 11 months bring, but I think I'm going to need at least a couple more sets before Christmas next year
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