Ramp times in regards to thermal cycling.

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v8r

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would you guys mind sharing your ramp time settings when using a heat treat oven to Normalize 1084 steel. I recently purchased a Paragon KM18T heat treat oven. I did the first cycle on some 1084 blades. I took it to 1600f with a ramp time of 800 degrees per hour.
Is this a excessive ramp time in regards to length, or should it be faster?
I just want to make sure I'm not baking all the carbon out of the blade.
 
No you shouldn't be inserting the blade and allowing it to come up with the kiln. Get the kiln to target temp (For normalizing 1084 this is ~1600f). I will even let the kiln sit AT target temp for 15 minutes or so PRIOR to inserting the blade, just to make sure there are no temp overshoots. Temp overshoots are but one problem that can happen with a blade that is ramping with the kiln. Excessive time above critical temp is but another.
 
samuraistuart said:
No you shouldn't be inserting the blade and allowing it to come up with the kiln. Get the kiln to target temp (For normalizing 1084 this is ~1600f). I will even let the kiln sit AT target temp for 15 minutes or so PRIOR to inserting the blade, just to make sure there are no temp overshoots. Temp overshoots are but one problem that can happen with a blade that is ramping with the kiln. Excessive time above critical temp is but another.
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So more than likely these blades are fried then from what you guys are saying . I read the info that came with the oven on heat treating and it said to let the blades come up to temp with the oven, and to never stick a room temp blade in a preheated oven.In the instructions it also said to ramp up the last few hundred degrees at a slower rate so you would not overshoot temperature . I was standing there when the oven got to temp, and the readout didn't go over 1600. I immediately pulled the blades out and let them air cool in still air.
 
Your blades are fine. You would have to heat it for days at 1600F to remove much more than a few microns of surface carbon.

The info you listed that came with the oven isn't really what I would recommend.

Ramp at 9999, let come to temp for 5 minutes to stabilize, place blade in oven, soak for the desired time. Depending on what you are trying to do with the blade, either remove and air cool, or oven cool at 50F per hour.
 
I wouldn't say there is anything wrong with the blades, just that it is best metallurgical practice to insert the blades in the kiln once the temp has been reached, and rebounded a time or two ( or three...15 minute wait or so, just for peace of mind). You certainly can slow down the ramp rate once you get close to your target temp to help with the rebound issue.

If 1084 is normalized and not protected from decarb in any way, there will be a lot more decarb than just "a few microns" to deal with, even with a short soak.
 
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Yeah, probably more like two hundred microns - .2mm or so. I was thinking a few thousandths (of an inch) and typed microns. It takes a lot to get decarb to penetrate .010" (ten thousandths).
 
how long do you soak the blades once the oven is up to temp and the blades are put in?
 
That is like asking, "How long to you cook a roast." It depends on the size and type.

For 1084 5-10 minutes is more than enough.
 
I keep forgetting we are talking 1084 here. All that is required of that steel is to reach target temp, equalize, and quench. No need to soak 1084, but I will do a total of 5 minutes, just to be sure you're up to temp and equalized and a short soak (technically 1084 does have a little more carbon past the eutectoid, so a short soak is good). For me, that means insert blade into your preheated 1500F kiln, and immediately start your 5 minute timer. Timer goes off, pull blade out and quench. That gives the blade 2-3 minutes to come to temp and a couple minutes soak). Once at room temp (or able to handle bare hand easily), temper.

Stacy and I posted at the same time. He's right. If the blade is a large chopper, then extend the soak a few more minutes, 10 being plenty (total time in the kiln)
 
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