I did a batch of 5 AEB-L knives last night, and decided to do some experimenting. First I made a set of coupons and used my normal heat treat but varied the austenitizing temperature to dial in the optimum temperature. Big surprise for me, the coupons at 1975f came out harder after dry ice bath than those at 1995 which was my standard temperature.
So, then decided to give the Devin Thomas prequench approach a try based on his generous posting on another thread. Batch of coupons at 1725 for 20 minutes, plate quenched, then put each back in the oven at different temperatures again for 8 min, then plate quench and into the dry ice mixture. Each was placed in the oven when it reached the target austenitizing temp. Again the coupon at 1975 was the hardest, and slightly harder than the coupon from my test with my original process so I decided to go for it with a batch of chef knives and utility knives.
Everything was going well, until the final step. As i pulled each blade out of the oven to plate quench, they drooped and bowed inside the foil packet. Never seen this before with my original process. When I set them on the aluminum plate before clamping, they had as much as a 1/2 inch curl from end to end. Once clamped, they came out pretty straight, but I could see a slight bend in most still. Decided while they were still a bit hot to bend them back into shape with gloved hands and my granite block for reference. I was surprised that they actually bent fairly easily and thought I must have messed up the heat treat for sure. Got everything straight into the dry ice bath- and the slight bow returned! Tested each blade and was happy to see each hit the target hardness, just have an annoying slight bow that probably only I will know is there but will bother me just the same! later, after an hour in the tempering oven I took them out to try to straighten but now they were locked in to their shape with no adjusting possible.
Anybody try this and notice the same? Is there something about the prequench that produces a softer blade at austenitizing temperature? Is the 8 min at austenitizing vs the 5 I used in my previous process causing this? Worried now that I don't have a process that produces straight blades.
Appreciate any advice- already made a note to self about "not experimenting when running a batch of knives" haha!
Stuart
So, then decided to give the Devin Thomas prequench approach a try based on his generous posting on another thread. Batch of coupons at 1725 for 20 minutes, plate quenched, then put each back in the oven at different temperatures again for 8 min, then plate quench and into the dry ice mixture. Each was placed in the oven when it reached the target austenitizing temp. Again the coupon at 1975 was the hardest, and slightly harder than the coupon from my test with my original process so I decided to go for it with a batch of chef knives and utility knives.
Everything was going well, until the final step. As i pulled each blade out of the oven to plate quench, they drooped and bowed inside the foil packet. Never seen this before with my original process. When I set them on the aluminum plate before clamping, they had as much as a 1/2 inch curl from end to end. Once clamped, they came out pretty straight, but I could see a slight bend in most still. Decided while they were still a bit hot to bend them back into shape with gloved hands and my granite block for reference. I was surprised that they actually bent fairly easily and thought I must have messed up the heat treat for sure. Got everything straight into the dry ice bath- and the slight bow returned! Tested each blade and was happy to see each hit the target hardness, just have an annoying slight bow that probably only I will know is there but will bother me just the same! later, after an hour in the tempering oven I took them out to try to straighten but now they were locked in to their shape with no adjusting possible.
Anybody try this and notice the same? Is there something about the prequench that produces a softer blade at austenitizing temperature? Is the 8 min at austenitizing vs the 5 I used in my previous process causing this? Worried now that I don't have a process that produces straight blades.
Appreciate any advice- already made a note to self about "not experimenting when running a batch of knives" haha!
Stuart
