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View Full Version : Kiln For Heat Treating ... Revisited

Lou
10-23-2006, 01:14 PM
I want to thank everyone for their input to my original post. I guess that I should have explained myself a little bit better on the question. Last week I made a special angle counter sink for a friend of mine to use in aluminum. The counter sink body was 1" in dia. about 1" long and necked down to a 1/2" shank about 2" long. I machined the cutter, fluted it and then heat treated it with a torch and then sharpened it on the tool and cutter grinder. The steel being used was 4140.
After completing the job, I thought, how about using the kiln for heat treating ??? ( the original idea for purchasing the kiln at a yard sale). OK, heat treating the project with the torch, approximately 15 min. with some scaling and spalling, but project completed.
My original question was an arbitrary 5 cubic inches of steel, to an arbitrary 1600F to give me a rough idea as to what to expect from my kiln.
After nemours followups to my post I have found out:

1. I need a PID

2. I don't A PID

3. maybe stick with my torch

4. It will take 45 min to get my kiln to 1600F

I'm not complaining, but as the end user I have found this to be VERY interesting.

Thanks again to everyone who has responded..... Lou

Alistair Hosie
10-23-2006, 01:50 PM
what's a pid.Maybe I need one too.Alistair

gzig5
10-23-2006, 02:28 PM
Allistair,

PID= Proportional, Integral, Derivative

Fancy mathmatical terms.

rantbot
10-23-2006, 04:18 PM
It will get even more interesting if you ask if 4140 was the right steel for the job.

J Tiers
10-23-2006, 05:25 PM
It will get even more interesting if you ask if 4140 was the right steel for the job.

Which I would argue wouldn't have been my first choice, but.............

I think your one point is pretty much key.........
4. It will take 45 min to get my kiln to 1600F assuming it is true...... which it very well may be.

The key issue is that it takes maybe 5 min to light the torch , heat the part, and dunk it, and maybe 5 more to temper it.

So you need a reason to fire up the kiln. You need to be:

a) doing a bunch of items that you can heat at once.

b) doing an item that is not evenly heatable with your torch

c) doing an item that needs a specific temperature profile.

d) wanting to have a particular tempering temperature held to hit a hardness range

For "a" the kiln helps you do them all the same way. You COULD do it with a torch, but might have some variations.

For "b" the kiln is fairly essential.

For "c" or "d" the kiln AND a good control are essential. In fact, for "d", TWO kilns would be nice......

lazlo
10-24-2006, 11:54 AM
Last week I made a special angle counter sink for a friend of mine to use in aluminum. I machined the cutter, fluted it and then heat treated it with a torch and then sharpened it on the tool and cutter grinder.
...
After completing the job, I thought, how about using the kiln for heat treating ??? OK, heat treating the project with the torch, approximately 15 min. with some scaling and spalling, but project completed.

I use a MAPP torch for small jobs too -- when I don't want to fire-up the furnace for a little job. One thing though -- are you tempering the cutter with a second heat? After you quench that 4140, its going to be unbelievably hard - around 65 Rockwell 'C.' That's so hard that it can shatter if you use the tool on steel.

For a cutting tool, it's usually recommended to temper back the quench hardness by re-heating to straw color (around 450° F) and let it soak for 1 hour per inch (just like the primary heat treat). You want to do this as soon as possible after quenching -- preferrably when the steel is hot out of the quench bath.

By the way, here's a great color table/temperature chart from one of the Knifemaker's forums:

http://www.anvilfire.com/FAQs/temper_colors_hardness.htm

Lou
10-24-2006, 08:26 PM
Thanks again for the additional information.
Looks like I'm going to have to get a colored monitor ( so I can use the color/temp scale) along with the PID. 4140 was my first choice, second and only other was 1018.

Lou