My last job before I retired I ended up being the heat treater for a big machine shop and their TIG welder for certain jobs, but was hired as an engineer. Go figure huh? I became the heat treater because I mentioned to the owner that I made knives as a hobby. As the HT guy though I could do my own knives and use drop-off scrap if big enough for knives. I already had a working relationship with a HT company I used them for jobs that wouldn't fit into our oven which was 24 inches deep. Used D2 a lot for paper cutting blades that cut the "FOLD AND TEAR HERE" lines you see on envelopes and other things. HT always the same, 1200, hold then 1600 and hold the ramp to 1850 for 30 minutes and air blast with an air hose and paint sprayer misting water. Temper at 500 degrees for two hours then cryo in between blocks of dry ice in a cooler with 4 inch thick walls of Styrofoam for 4 days or 6 if a weekend was in the cycle. The dry ice had only half evaporated. Then into the HT oven to 1000 degrees for one hour, do not exceed one hour. It will be right at HRC60 with decent toughness for D2. D2 isn't a very tough steel like O1 for instance and if you want or need the toughest knife or ax you ever saw use S5 steel at 59-60 hard. The S stands for shock and S5 is better for knives that S7 which doesn't get as hard as S5. Worst thing you can do to D2 is overheat it by even 50 degrees. 1850 is D2's sweet spot like 1475 is O1's. A temper at 700 degrees the D2 will start getting harder until you hit 1000, it drops fast past there, like 1200 will get you HRC55 instead of the 60 at 1000. Now mind you at 700 it is still 57 hard, but if you want 55 or lower you're not getting it in your kitchen oven. For some industrial applications you need to go softer than HRC 59/60. Keep in mind that hardness is not the end all and be all of D2 as it will hold an edge at 58 as good as 60. What gives D2 its abrasion resistance or edge holding is the chromium and vanadium carbides it makes. As quenched D2 is 63 to 64 hard and 63 is preferable for toughness and too fast of a quench can setup stresses in the matrix of the knife. Knifemaker Ray Rogers told me he had a D2 knife crack and break apart 3 weeks after he finished it, but he had also forged it too. Something he called a nightmare because D2 must be forged at 2000 degrees. SAFETY TIP, wear a tinted face shield if tempted to try it as the light will harm your eyes and even a regular forge is long term harmful as well if you stare into it too much and don't even think about heat treating D2 in a forge. It heats up too fast and easily overheats.
@@rarknivesandleatherwork8045 You're very welcome. Everything I learned about D2 came pretty much from Hinderliter HT in OKC, OK. That 1.50% of Carbon in D2 guarantees that the Chromium and Vanadium will make carbides, but look at AEB-L steel with its 0.60% carbon. That is to ensure that the Chromium does not turn into carbide. Therefore the chromium doesn't convert into austenite and lose its stainless properties. AEB-L achieves its hardness from mostly Ferrite or Iron Carbide and should have a shallow cryo treatment of -95 F. I used dry ice at -110 and simply put the blades between the blocks. I tried the mixing it with one of kerosene or alcohol, then acetone to make a slurry, but it used up a bunch of dry ice, made a mess and the acetone was just plain scary. So I just built a box with Styrofoam 4" thick slightly bigger than the 10lb blocks I could buy at the grocery store. I lined the inside with an 18 gauge, .051 stainless box that nested into the foam and made the outside out of aluminum that the foam dropped down into. It could hold 3 blocks of dry ice for over a week. (Safety note, if using dry ice store in a well ventilated area. It could make a basement into a death trap.)
D2 difficult heat treatment with raping stops to critical temp . Triple temper . I use 99% alcohol with dray ice in a strophe picnic container for cryo , till the dry ice evaporates through a hole in the lid . pour the alcohol back into bottle .
D2 what I have found 1850 30 minutes..quench.....450 draw two times 1 hour each,they come out 60 61 RC I test every blade...nice shop,they do not have to be big to make good knives..
Tempering determines the final hardness/toughness balance which you require. I triple temper for two hours each time at a temperature that gives the balance I want.
RAR Knives and Leatherwork I ended up getting a pair of plates off the internet, struggled locally (I live in Macclesfield) so hopefully next week I’ll be able to make my first SS knife!
