CPM154 warp...two questions

[silver_pilate]

Just heat treated a 3 1/2" edge full flat ground blade of cpm154. The blade was thoroughly cleaned, packaged in SS foil and placed on its spine in a holder in the oven. I equalized the blade at 1400 for about 20 minutes, and then jumped up to 1925 for 45 minutes. Then I clamped the blade between my quench plates with the foil still on and let it cool. After I removed the packet (the blade was room temp), I noticed a very small warp at the tip, only the last 1/4" or so of the blade. This area, of course, is not in contact with the plates because of the distal taper.

So, two questions:

1. How can I fix this blade? Would soaking at 1200 for 2 hours be enough stress relief that I could bend the tip back to true. Also, at what temp do you normalize cpm154 after bending the tip back? I'd really like to fix this blade as it turned out nice and is for a Christmas customer.

2. How can I fix this in the future? Obviously, as Ken suggested in another post, I can grind after HT, but is there a way to fix any warp before the blade is fully set up? How long should I leave it in the plates prior to cutting the packet open and fixing any warps?

Thanks for any insight here. I'm familiar with straightening a warped O-1 blade out of the oil at around 400, but have never had to do it to a stainless or air/plate quenched blade.

--nathan

 

[mete]

At what temperature do you temper your CPM154 ? If you use a high temperature , ~1000 F, you should be able to straighten at the high temperature fairly easily without any other treatment. Never attempt straightening of any blade below 400 F.
Fixing the warp before the blade is set up would require you remove the blade from the foil. Remove foil when the blade is 1200 F to prevent scale forming .

 

[silver_pilate]

I temper at the lower end, this one just one cycle at 375 to take out some stress as I know I will be re-HT'ing it.

Mete, do you think I should heat this blade up to 1200 for a while and then try to straighten while it's at temp? Also, do you have any guesses as to how many seconds between the plates before I need to remove the packet and attempt straightening in future blades?

Thanks!

--nathan

 

[mete]

Probably the safest thing is to temper twice at 1200 F and after the second temper , while still hot , straighten it.
I have no idea of the cooling time in foil.

 

[silver_pilate]

Thanks!

For other makers using CPM with foil and quench plates, what do you typically do to correct warps and when?

--nathan