having problem with 01 heat treat, odd cracking almost like delaminating.

P

Paliden

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Mar 26, 2006
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has any one had 01 crack lengthwise in the middle of the spine? I'm use to heat-treating 5160 and 52100 with few problems but had a couple knives crack along the spine almost like it was de-laminating. I'm using precision ground 01 3/16" thick the process that i have been using is profile to shape, normalize in either an electric ht oven or gas forge. in the oven the normalizing temp is 1525f. 2x. then air cool. pre-heat the oven and blade to 1250f and hold for 5 min, then to 1525f hold for 5 min and quench in 120f to 140f canola oil. where it is held till below 350f then into room temp oil till completely cooled, wash and sandblast, then into oven at 400f for 1 hr, air cool, then second identical draw cycle. any thoughts or suggestions would be appreciated, thanks,
 
You should tell us where the steel came from. That will help .

This pops up with various steels from time to time. It usually traces back to a bad batch of steel from the mill. The beginning of the split is put in the steel during rolling ( rolled a bit too cold) and no matter how well it is annealed and rolled after that, it may separate in the stress of quench.

Contact the supplier you bought it from, and tell them what happened. They should replace the steel.
 
Thanks Stacy, that helps. I'm reviewing my ht regimen to make it consistent. 59-60 Rockwell is the target which we were consistently getting with Aldo"s steel but found a local supplier but noticed only getting 57-58 Rockwell with same regimen. i think I'll stick with Aldo as a supplier.
 
Not sure if I read your post right. It looks like you sandblasted before tempering. Can that cause a problem?
 
sand blasting is to remove any scale or dirt, i use fine grain sand running moderate pressure. the blades are stock removal.
 
Thin hollow grind?
Are you making certain to keep the same amount of passes on ea side as your grinding?
Have had a crack or three but mainly what is mentioned above was the culprit. Very seldom with O1 steel unless it was overheated and/ or quenched in to cold a quench.
 
blade was not ground yet, just profiled. flat grind is done post ht. problem was noticed after the draw cycle before grinding. I've made these knife blanks 3 times now. unfortunately the steel from the local supplier was used for the first 2 times. after the 1st time i thought id messed up ht somehow, so made the second set. after they also had the cracking i got a bar from Aldo. they're profiled and normalized, will do ht on Monday.
 
Have always used steel from Alpha knife supply or the better known suppliers, with no issues.
Sounds like a bad batch of steel
 
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