are forge and heat treat ovens the same

A

ajohnson55005

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Feb 19, 2012
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Stupid question of the day. I read a lot of posts about forges. But very little about heat treat ovens. Do u guys use the word simultaneously or is there a diffrence. I have been tossing around the idea of making a heat treat oven. I can get I PID SSR and a K thermocouple on eBay cheap. The brick is cheap and I can pick it up after work. I don't know if propane or electric is better. Some time in the future I may try hammering on hot steel. In the short term I will be only stock removal knife work. Any info would be helpful
 
You can use a forge to HT but it can be difficult. It is hard to use a HT oven to forge unless it can go above 2000f and has an inert atmosphere. My forge is set up so I can HT. It heats evenly and has a very stable temp control. So for me the answer is yes. Some may not be able to. If I want super tight control in HT I have a salt pot.
 
They are definitely not the same thing.

At a pinch, each might be just about used for the other job, but will almost certainly not do it well.

If you are considering building an HT oven, electric is the way to go. Control is reasonably easy and the additional cost per kWhr of the electricity is more than offset by not needing to have somewhere for the combustion products to get out (so needing a much greater heat input on gas).

I've built 5 so far and I think I'm getting the latest ones fairly close to right. Some things I'd strongly advise:

Use type 23 Insulating Fire Bricks (JM23's if available). 2300 degF is enough. and the higher-rated bricks are denser and are poorer insulators, making them less suitable for an HT oven.

Use a PID controller that will work with an SSR and use a 2-second output cycle. If the budget will stretch to it, a ramp/soak controller is worth the extra.

Use the fastest-responding thermocouple you can get. Run the oven up to around 1100 degC/2000 degF to get a nice black oxide layer on the thermocouple BEFORE you run the autotune.

If there's any chance you'll treat more than one blade in a batch, make sure you can operate the door with only one hand.

Spend some time thinking about it, and what you might want it to do. I build mine so they are normally used horizontally, but can be stood on end and used vertically with a salt pot. I have a separate control panel with a socket for the power to the oven, a socket for the thermocouple and a socket for the door switch (I fit a door switch to cut the power when it is opened. The ovens I've built have all gone to people I like and I'd like to keep them alive). The control panel can also be used with a crucible furnace. One of my next projects will be a tempering oven, so I don't have to wait hours for the oven to cool before tempering, that will run off the same control panel.

It's well worth reading the .pdf file at http://knifemaking.webs.com/heattreatmentfurnace.htm if you haven't already.
 
Here is my forge:
IMG_0736.jpg


Here is my heat treating oven:
IMG_0778.jpg


:)

As an addendum related to your interest in building an oven, here is the oven I built a year or two after starting:
IMG_6499.jpg


--nathan
 
Thanks for the great info. First of Nathan I'm not sure I can t:Dake advice form someone with such a clean han shop:D
Niacrome or Kanthal A1 are my elements, still have to make a decision. At this point I am planning on building a 4x4 x16 oven. Four bricks top and bottom two on each side and two on each end. Assuming the Hong Kong pid SSR and k thermocouple work I will save money after about 5 single blades sent out.
Thanks for the info.
Adam
 
Kanthal A1 seems to be the better choice, especially if you are going to be running up to stainless steel temperatures.

I got mine from ebay seller jrider12 in 16ga Kanthal A1. He seems to have dropped off the radar lately, but pmtoolco on ebay have been listing what appear to be the same elements recently. None on at the moment, but it's probably worth giving them a try. Both jrider12 and pmtoolco are/were in Portland, Oregon.

There are a lot of far eastern elements on UK ebay lately, shipping from Hong Kong and China. They seem to be much finer wire and the descriptions are pretty vague, with no detail at all on the tails, which leads me to think they may just be cut from a long coil.

The cheap PID should work OK. I've used a SET620, which seems to be the same as the TET612 and N2006P, judging by the manuals. I also have a Sestos D1S-VR-220 that looks like it'll work, but haven't actually fitted it yet. Be careful if you are thinking of one of the other models and check that it'll accept a type K input and work to the higher temperatures. A few of them will apparently only read to 400 degC (752 degF).

The themocouple supplied with the controller will be no good for an HT oven. It'll either be PVC insulated and only good to a little above the boiling point of water, or a mineral insulated thing with an oddly-threaded retaining nut that seems even less use than the PVC one. Take a look at Omega.com for something that will get the job done. I've found Omega (albeit their office in the UK) to be very helpful with advice on the phone, so give them a call if the online catalog gets too daunting.

The controller I recommend is this one

http://www.automationdirect.com/adc...ers/1-z-16_DIN_Size_(SL4848_Series)/SL4848-VR

It gives ramp-and-soak program capability and is the cheapest thing I've found that will do the job well.

As far as I can tell from the manuals from AutomationDirect and Omega, Omega also have the same controller badged as the Omega CN7823.
 
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