1st heat treat issue ever...your opinions on this?

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godogs57

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Apr 16, 2004
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Closing in on knife #1500....for stock removal I have been using CPM154 exclusively for the last 4-5 years or so...whenever it first came out. Heat treating a batch last week and I had one warp all over the stinking place. To the point I could not save it, which ticked me off, as we all know how much time we have in a blade at that point, not to mention CPM154 is not cheap!

I had a batch of 5 knives in ht that day, all individually wrapped up in foil (the high temp stuff) and brought 'em up to 1950 degrees. I take the blades out after 30 minutes and all is normal at that point: taking them out of the foil and air quenching under my fan....except for my problem blade. I swear it looked like it had been vacuum sealed in that foil! I could hardly get it out...turns out I also had a little dime sized bit of foil stuck to the blade. After I got it out, I tested all the knives and they were all at 62.5 Rc. A triple temper and I was on my way, still wondering what happened. I look at the problem blade and it has a horrible tip to tang twist in it. I figured I would heat with a propane torch and see if I could salvage it to use as a shop knife...it certainly would never be up for sale. No go...

My other blades I just cut open the end of the foil and pull them out or ease them out...not this one...she was sealed in there! And then the warp... Can anybody guess what I did wrong on that one particular blade? Perhaps it was just bad luck...I don't know. oh yeah....I also put in a small bit of newspaper with each blade to burn up like everyone else does.

Any suggestions very much appreciated!
 
I'd guess the twist may be related to trying to get the darn thing out of the envelope.

As to why it stuck, there was recently a LONGGG thread about the effect and possible causes. Interestingly, I had one stick yesterday, and it's been nearly a year (~2000 blades) since the last time it happened. Moon phase? :rolleyes:
 
Every now and then a blade will stick/weld itself to the foil. Hard to say why, but it happens. If it does, just quench/cool the whole package. The pulling and twisting in trying to remove the blade can bend/twist/warp the 1900F steel pretty easily. At that point it is like stiff taffy.

First thing to do when this happens is - Take Your Time.
Remember, this is an air hardening steel, you have many minutes to play with it with no loss of hardenability. If it appears to be really stuck on, you can just plate quench or air quench the whole packet/blade . If you just can't bring yourself to do that, trim the packet off around the blade with your scissors, and gently peel the foil away. No need to rush, take your time, and quit if it is obvious that the foil is welded to the blade.
 
I have had a few stick over the years. Two possible problems, First, piece of paper was to big, which when it burns up will expand the pouch and cause it to crack and then colapse against the blade. If left in to long it will weld to blade. Second you actually forgot to put the papper in. As careful as I am, it still happens ever now and then. But the issue here is what to do when it does happen. Bladesmth said it, take your time getting it out of the pouch. You have a lot more time than you think. But in the event that after you get it out and it's warped or misshapen not to worry. Most S.S. will remain in a plastic state for a short peiod of time before it has been tempered or Cryoed. If after your blade has cooled so you can handle it, just bend back in shape. I Cryo all my S.S. and if I have had to straighten one it sometime will warp back just a little. Again not to worry. Using a three pin vise, bend blade past the warp and using a propane toruch heat spine at the warp. Don't worry about loosing your Rockwell mumber. Most S.S. have a secondary tempering temp. of about 900 deg. Your not going to be heating your spine the hot. Cool the blade by first spraying the side of the blade that you want it to move, then spray it all until cool. I hope this all make sense to you.

Michael
 
Thanks all...every guy I have ever seen ht a knife, when taking them from the oven it has been "off to the races"...got to get it out of that dang foil wrap ASAP! I will keep in mind that I can take my time and still be ok. In the past, I have had some that I just could not get one hand and tongs on the foil, the other snipping open the bag quick enough to suit me. Now that I think about it though, after they cooled down, they were all the same hardness....that one that took me an extra minute or so was just as hard as the others.

Good advice...thanks!
 
I have just started cooking my own stuff only a month ago, but in that thread mentioned earlier, RJ Martin told me to use plain talcum powder. Rock solid performance, dust the whole thing with powder, shake off the excess, wrap it up. No paper, the powder burning does the same thing removing oxy and also makes that little bit of oxide or ash to stop the sticking. Super clean blades out of the foil. I quench in the foil too.

and on top of that I have a large bottle, that will last for the rest of my life.
 
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