AEB-L warpage woes

Jarrod, thank you very much for sharing your tips and tricks so freely. I have learned a lot from your posts since I started making knives.

I did straighten a couple of blades between quench and cryo yesterday and like you said, they bowed back. I will quit doing that and also be more careful opening the pouches. Based on one of your previous posts, I quit grinding the surface before HT a while ago and had pretty good success until yesterday when only one blade came out straight.

 

I want to thank everybody for your help. I think I have a good idea how to get the lateral warp out. Maybe it got lost or was poorly explained, but nobody commented on the curvature some of my blades now have in the other direction. I tried to get a picture of it but it did not turn out so well, so I made the very exaggerated illustration below. Has anybody seen anything similar or am I the only one? This problem is also most severe at the tang/blade junction and it is almost like there is a kink and the tang is kicked up. I recall seeing this on one blade I made about a year ago, but back then I attributed it to a mistake in profiling the blade even though that did not seem very plausible.

 

I don't know if the piece I have is impact grade or not, I think it was labelled as C2 tungsten carbide. I can check tomorrow. Honestly, I did not know there was such a thing as impact grade carbide until very recently. Assuming I have non-impact grade carbide, will it immediately shatter?

 

I'm glad the drill bit missed your eye. I used to be a lot more casual about safety equipment, but I have become pretty good about wearing safety glasses in the shop, as well as a respirator and hearing protection. I'll make sure to be careful with it.

 

How long do you keep it at 650°C? I assume you do this step without foil in the blade rack you showed a picture of a while back?

I would be interested to know what the purpose of the two different temperatures is. @DevinT recommends a pre-quench from 20 minutes at 1,725°F for grain refinement before hardening. In a separate thread, he recommended a sub-critical anneal at 1,350°F for a couple of hours if the hardening occurs a significant amount of time after the pre-quench. Your temperatures are relatively close, do they serve the same purpose?

I've been looking at your oven build thread recently, that turned out really nice. I am starting to plan for a bigger furnace.

 

I used an old 12oz ball peen hammer and drilled a 1/4" hole with a carbide drill bit. The hole turned out a bit smaller than the carbide insert, but I was able to press it in there and it seems very solid. I tried it on a few of the blades and it is just amazing. It worked even for a 3mm thick honesuki blade that had a pretty decent warp.

The carbide I used was indeed C2 carbide rod from McMaster. I could not find much online in a quick search about impact resistance. The piece started out 2" long, I scored it in the middle with a diamond disc, wrapped it in a rag and hit it to break it in half. It took a couple of good blows without breaking before I hit it for real and it fractured into two pieces. I think it will be fine but I will be careful with it and report here if it breaks.

Thanks again everybody for your help.

 

Your heat treat sounds convenient, saves the first plate quench compared to what I have been doing. With my small HT oven, I try to build up a bunch of blades to do the final HT on in a single day. So I'll pre-quench and then anneal a couple of blades when I can until I have enough together and a free weekend day.

It will be a while before I start building a new oven. I'm interested in what you will do differently for your next oven and hope you'll do another WIP thread. I like the idea of putting the coils up top like JT's and Drew Riley's ovens, it seems a lot easier to service. I dread the day the coil burns out in my current oven and I will have to replace it.

 

I used a diamond coated wheel in a Dremel tool. The wheels are pretty cheap at Harbor Freight. I had the carbide spinning in the drill press and just shaped it with the wheel. It is very quick to do. I then spun it in a hand held drill against a cork belt loaded with compound to polish it a bit. Maybe that did something, the surface came out pretty smooth.

I have scratched my carbide file guide using ceramic belts, but I don't think they would grind carbide very efficiently. I am curious now, I'll try to test it tomorrow if I remember.