tempering emergency

S

smorgan345

Joined
Mar 8, 2007
Messages
242
Well, I was on my second and last tempering cycle and I had an emergency and had to leave the house. The cycle was 325f for two hours but the knives sat in the kiln for an additional 30-45 minutes at about 300f before I got home. Anybody have any ideas what effect this might have had? Do you thing they be too soft now? I'm using 440c. Thanks for any input.
Scott
 
Dude! chill, it's OK, if you left them in at 300 for a day you'd probably be fine, I temper for a total of 3-5 hours sometimes, I don't play with 440, but I don't anticipate it being that much diffferent from all of the steels I do use

-Page
 
sunshadow said:
Dude! chill, it's OK, if you left them in at 300 for a day you'd probably be fine, I temper for a total of 3-5 hours sometimes, I don't play with 440, but I don't anticipate it being that much diffferent from all of the steels I do use

-Page
Click to expand...

thanks. This is my first heat treat so I'm overly cautious. mostly cause I'm still learning what the processes actually do to the steel so I'm following directions to the T so I don't screw up all the hard work that went into them. this is good news, thank you.
s
 
A quick search online and a double temper at 325F (165C) should yield maximum hardness of about Rc 60 and increasing the temperature is what will affect the outcome and in your case if you went up to 375-450F you will only increase the toughness and drop the hardness to about 56/58 Rc.

And I read Kevin's article a few times in addition to staying in a holiday inn express last night!

I am no expert, I just grabbed my Machinery's Handbook and double checked with google. Both sources say you should be fine.


-Xander
 
With an extra hour or two in a receding temperature ( 325 down to 300) there would be no change in hardness....just a better temper. After four or five hours, any RA might be stabilized, but since this was the second temper, it was going to stay anyway.
 
No need to worry,alot of times I will set my kiln for a 2 hour temper run on the second temper, and then go in for the night,pull the blades out the next morning,as Stacy said it should stabilize any remaining RA and make for a better temper.
Stan
 
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