T- minus what to 400*?

[shane wink]

I have some 52100 I am wishing to use but all I have is parks 50# which I am told is too fast for it. So I am looking at an interrupted quench at 400* but how to I gauge that the metal is at 400* and time to remove it? DO I wrap the blade in newspaper and set it aside to cool to room temp or hang it so it cools to room temp in still air then put back in the oven at 450 for several hours?

 

[mete]

One of those handheld IR thermometers would be handy. Otherwise it's a guess.Once it gets to 400 * it can just be aircooled, then tempered.

 

[shane wink]

Thanks Mete.

 

[jdm61]

Erratus, some folks would tell you that with a deep hardening steel like that, you only need to get it below say 900. I would not try that with say W2 (the myth of auto tempering), but I know that some folks use to do a quick interrupted water quench of 52100 just to get it cooled to black. As for wrapping and setting it aside, I would say no. IF you set a hot blade down any way other than upright, IMO, you risk warping because the structure in that blade is not set up yet. You can get slight warpage even in the temper by lying thr blade flat on the rack of your kitchen oven in my experience.

 

[Rick Marchand]

You can kinda gauage the 400F mark by the way the oil is behaving on the hot blade as well. Look up the smoke/flash point of the quenchant you are using. They are often times very close to the same. I know that if I pull the blade out and it is billowing smoke that I am not quite there. Obviously, if it flares up you are way too soon. I like to see whisps of smoke and a slightly wet texture to the oil, without excessive dripping. I use HQ-K but it was similar with canola.