Split, again.

[KnitePrince]

Okay, tried to post the picture, but I have to apparently upload it somewhere and then make a link here.. so I will just explain.... I have, at this time about ten knives, hand made, that SPLIT down the middle when tempered. Just had another one split today.

Solutions I have tried;
Cleaner metal, using both coarser, and finer grinding of the surface. CLEANING it with, Alcohol, kerosene, Lacquer thinner. Welding the entire edge of the billet. And lastly, building a new forge that gets hotter. I have also tried different quench oils, thinking I was cooling it too fast. The oil I used today was 5W20 Motor oil, in an attempt to quench it a bit slower than the cooking oil or the Grade 22 Phillips Quench oil.
Usually the split is close to the center, in this case it split between the two pieces of 15N20, the patterned steel welded to the 15N20 splendidly, but the two pieces of 15N20 split apart...
I am at a loss as to how to solve this. As most of you probably know, by the time it is ready to quench, a lot of work has gone into it, only to have it SPLIT when quenched.

I can get the new forge hot enough to turn the blank white hot and sparkling, which I understand is too hot. If anyone has any ideas, I would LOVE to hear them. Thanks! Scott

 

[Templehound]

In 30 years of knife making I only had this twice, with two san mai blades.
Outside layers were Damascus with a mono steel cutting core.
I asked fellow knife makers and spoke two of them who experienced the same problem.
The amount of tensions in san mai and damascus blades is quite enormous, really hard to believe.
The solution was, after forging give the welded and forged chunk several times of stress relief in 680 - 700 degree celsius and letting them cool down in the oven.
Doing this 3-4 times seems it solved the problem because it never happened again.....good luck.

 

[KnitePrince]

In 30 years of knife making I only had this twice, with two san mai blades.
Outside layers were Damascus with a mono steel cutting core.
I asked fellow knife makers and spoke two of them who experienced the same problem.
The amount of tensions in san mai and damascus blades is quite enormous, really hard to believe.
The solution was, after forging give the welded and forged chunk several times of stress relief in 680 - 700 degree celsius and letting them cool down in the oven.
Doing this 3-4 times seems it solved the problem because it never happened again.....good luck.

Thank you very much. I will give this a try and see what happens. I appreciate the response and advice! SO MANY hours involved only to have the blade split when quenched. I will reply with the results!