over tempering?

swede2207

swede2207

Joined
Mar 10, 2002
Messages
323
Hey guys,got a question. Since im so smart..i went off to the deerstand and left a knife in the temper(toaster) oven, for about 4 and a half hours. Is this knife ruined? If so why? And what would you guys do..scrap it or do i just need to harden and re treat..or is is ok ? Thanks
Luke
 
Just continue temper cycle, leaving it in that long should have no detrimental effects to the heat treat. Can re HT it if yoru eally want, but I think you'd just be wasting your time.

Well, assuming this is a high carbon steel tand that you did HT right in the first place.
 
What etp777 said, I use a toster oven and since it cycles up and down I leave mine in for three hour runs, with the high end the correct tempering temp. As long as you didn't go over the temp and got to soft you'll be alright.
 
Well the steel was 01 and edge quenched in goop as per "the 50 dollar knife shop" then was put into a preheated oven at around 400 degrees..so i went ahead and did another hour and a half cycle..i have to work tomorrow so ill finish the ht on tuesday..thanks.
 
Yep, should be perfectly fine, sounds almost exactly like my HT cycle, though I won't swear to using same tempering temp(been a while, woudl have to dig out my notes again)
 
I once heat treated a 4140 hammer head for three days. Forgot I had it in the shop oven. It came out fine.
 
What everyone said. On simple carbon steel I don't think you can leave it too long.
 
You should be able to leave it there overnight so long as the oven remains no greater than the desired temperature. I would consider it as only one temper session, so if doing two tempers it would only count as one and the second temper I would do for its full normal amount of time and temperature. No change.

RL
 
Gib, that was an interesting read. While i understand that carbon can move at lower temperatures,i am seriously doubting that the extra hour in the tempering oven would be long enough to cause such. In that post the guy left it overnight, this one was only about an hour and a half longer than i normally do. There is of course only one way to be sure. Ill clean up the knife sharpen it..and test it on some rope..see how long it lasts compared to my previous blades. At that point ill be in a better informed position to form an opinion. thanks for all the help guys..ill let you know.
 
Swede, It's not the hour or two extra that I worry about it is the times that I forget all about it and find it in the oven the next morning. Gib
 
Gib, i know what you mean..my best trick is to put one in the temper and start grinding on the next project..getting caried away..i havent left one overnight...YET, but im sure it will happen. In that situation..i will redo the whole schmeer just for my peace of mind.
 
You blademakers are sure forgetful types, and Rick has the record of three days , wow !! Certainly tempering to color is not acceptable, at least 1 hour is needed to get a good stable martensite.More complex steels should have 2 , 2 hour tempers. While in these transformations temperature is linear , time is more of a logrithmic function as you see in the TTT diagram. On that basis 12 hours should not be any problem. Rick's three days might though, but that's beyond my experience .Of course the higher the temperature the more of a problem excess time would be.
 
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