Looooooong heat treatment

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kickinwings

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Mar 30, 2017
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Hi folks long time reader first time poster here...

Just a quick question about using a heat treat oven.

I've got a china painters kiln that gets up to 2010 degrees f (1100 c) the only issue is that it takes about 6hrs to get there! I've checked the elements and so on and it all seems to be working fine, just probably not designed to heat up that fast.

I've also got a PID temperature controller from my brewery that you can program ramp and soak times into.

I've been heat treating N690 by just doing a single 20 min soak at 1940 f (1060 c) but would like to add a pre-heat step or two before it reaches the austenitizing step for the final soak.

I'm just wondering if there would be any issue with the whole process including ramp and soaks taking 6hrs or so? It seems to get up to about 1470 f (800 c) in about 2.5hrs but takes 3.5hrs more to get to 1940 f (1060 c)
 
How big is it and what voltage does it run on? I have heard some say that the little 120V Paragon takes a pretty longtime to get up to temperature. If you are running one of those, the require a true 20 amp circuit.
kickinwings said:
Hi folks long time reader first time poster here...

Just a quick question about using a heat treat oven.

I've got a china painters kiln that gets up to 2010 degrees f (1100 c) the only issue is that it takes about 6hrs to get there! I've checked the elements and so on and it all seems to be working fine, just probably not designed to heat up that fast.

I've also got a PID temperature controller from my brewery that you can program ramp and soak times into.

I've been heat treating N690 by just doing a single 20 min soak at 1940 f (1060 c) but would like to add a pre-heat step or two before it reaches the austenitizing step for the final soak.

I'm just wondering if there would be any issue with the whole process including ramp and soaks taking 6hrs or so? It seems to get up to about 1470 f (800 c) in about 2.5hrs but takes 3.5hrs more to get to 1940 f (1060 c)
Click to expand...
 
Its 240v (i'm in New Zealand) and runs a 2.3kw elemnt so draws about 10 amps. Internal dimensions are 300x150x150 (12''x6''x6'')
 
Yeah, that sounds like our 110V 20A model. My 24 inch knife oven is 240V 20A. Just out of curiosity, how long does it take to get up to carbon steel temp of 1500F? Also, does it have a digital controller? I wonder if it ramps up slowly because it is made for delicate ceramics, not metals?
kickinwings said:
Its 240v (i'm in New Zealand) and runs a 2.3kw elemnt so draws about 10 amps. Internal dimensions are 300x150x150 (12''x6''x6'')
Click to expand...
 
It takes about 2.5 hrs to get up to carbon steel temps.

Yeah I've heard that before about ceramic kilns needing to be slower to heat up. No digital controller, it seems to just have a thermostat that clicks on and off if you turn the dial up and down (like your regular household oven). Is it possible there is something else that limits the speed which it can ramp up?

I've tested it with one of those household power consumption meters and seems to be using the right amount of KW and drawing 10 amps.
 
My 240V 20A takes what seems like a long time to me to get up to 1500F, but I would guess that it takes no more than 30-40 minutes at full ramp up setting.
 
Could be several things, check to see if there is a bad element if there is more than one. You could have the wrong voltage input. If it was made for 240 volts and you only have 220 volts, it will heat slowly. I think heating elements are based on resistance, if someone replaced them with the wrong one, furnace will be slow.

Hoss
 
A bit off topic from the main subject but I've been experimenting with heat treating AEBL. My question is, when my oven is at austenitizing temp for stainless, every time I open the oven door to place the blade in it would drop to about 1800, although it does go back up to 1950 in about a minute or two do I wait for it to settle back at austenitizing temp then start my timer to soak or do I start timing right when the blade is in the oven ?


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DevinT said:
Could be several things, check to see if there is a bad element if there is more than one. You could have the wrong voltage input. If it was made for 240 volts and you only have 220 volts, it will heat slowly. I think heating elements are based on resistance, if someone replaced them with the wrong one, furnace will be slow.

Hoss
Click to expand...

Yeah I've looked into all those things and the kiln is operating as it was designed, which is to paint china. My main question is would it matter if the knives were in the oven from cold to 1060c (including a couple a step soaks on the way) for around 6hrs. Would that negatively effect the heat treat in anyway?
 
I would be concerned regarding the length of soak. While you may only be at austentizing temp for the prescribed time, you will be soaking for over an hour at temps fairly close to that temp. I don't know much about n690 and at what temp grain growth starts/accelerates, but it's definitely something to look into.
 
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