Will This Furnace Work For Heat Treating?

[oldgoaly]

I've been using a muffle furnace for 25 years, your may keep temps even better!

 

[Plas62]

I think you got a good deal. They go for over $600 new. If I'm not mistaken on this model the heating elements are embedded in the liner material and the entire liner would need to be replaced if one of the elements went out. You would need to contact Paragon to be sure.

 

[12bolts]

When it comes time you can get any supplier to provide you with the element you need just by telling them some simple facts.
You give them the OD of the winding, the stretched length, and the temp you want to achieve, and the terminations you want. They will wind the correct gauge wire on a mandrel of the correct length and ship it to you unstretched. All you have to do is evenly stretch to length and install

cheers Phil

 

[Rick Leslie]

I hear ya Rick. I am such a noob that I wouldn't even know how to properly heat treat with a torch. Hopefully the new purchase will be good incentive to learn multiple methods.

Bob

There's a ton of info on the web. I read everything I could find before I started. Youtube is a good source too, but nothing will replace experience. A lot of the charts I looked at before starting to HT had contradictory info. An example is 4140. One chart said to heat to about 1400 F. Another said 1550 F. I've heat treated revolver cylinders made from 4140 and tested to destruction. From that I was able to settle on 1425 to 1435 F for my application. You also have to know the alloy you're dealing with or heat treating it will be a crap shoot. Order from a reputable source and get the certification with the order. Most metal suppliers will provide a 'pedigree' for the material.

Don't forget you'll be tempering as well, once you harden. I just use a small $20 toaster oven for that. Reaches just over 565 F.

The torch takes a little more finesse, at least for me.

 

[DMS]

I have the same furnace, and it works great. I have used it for heat treating, soldering, and enamel work. Very useful to have. As far as replacing the the elements, that is one disadvantage on these smaller models, the elements are cast into the refractory (the larger ones are built out of individual fire bricks). For occasional use, it should not be an issue. I also recommend purchasing a small kiln shelf to sit on the bottom and protect the kiln from damage and contaminants. Kiln shelves are available from ceramic supply houses, and are pretty cheap.

Regarding the ramp rate, if you care about hitting a target temp, I recommend against setting the ramp rate to "full", the overshoot can be pretty severe. If you set it lower, it takes a little longer to reach temp, but the results will be more stable.

Good find, I think I spent close to $700 on mine new.

 

[Rbeckett]

That furnace looks gently used so it should give you many years of good service before it needs attention. If your still heat treating when it breaks I am sure you will already be looking for a bigger and faster machine. so for the money and what you have planned it is an excellent buy and a great idea too!!!! It will allow you to get your feet wet in that arena without spending a fortune just to get the equipment. Good luck and some pics of you treated projects would be wonderful too!!!!

Bob

 

[frostheave]

Good for you! And I do not have personal experience, only from reading and I could be all full of it. But, I recall reading where if you use that kind of electric furnace at its high temp range all the time you shorten the life of the heating element (nichrome wire I believe). Maybe someone else can chime in, because I for one would like to know.

That is a good question. I checked the Paragon FAQ but didn't find an answer, other than being careful to not touch or contaminate the heating element. In that respect, this furnace is nice because the element is embedded and completely enclosed in the sides of the refractory material. Of course the downside is it must be more expensive to replace the heating element when it fails. I guess time will tell on element life.

Bob

 

[frostheave]

Yep, that's a nice oven for heat treating and Paragon is a good brand. It should serve you well.

As someone else mentioned, it achieves temperatures high enough for virtually all carbon steel heat treating. Unless you get into some of the more esoteric tool steels, most steels and various alloys only need temps around 1575F for Austentizing. Occasionally (rarely?), you might want to normalize something and that usually requires a 1700-1750F temp.

As far as the heating element is concerned, do your best to not dribble any contaminants on it. Doing so will put a quick end to the coils. Eventually, they will burn out but hopefully Paragon can sell new ones at a reasonable cost or, better yet, tell you precisely what type of wire to use, how long, loop diameter and number of loops for a given length. There are two kinds of wires (Kanthal and Nichrome) and they're rated by gauge and resistance per unit length (usually by the foot).

I have lot's of posts here about heat treating and if you look them up, I gave fairly detailed information and recipes for many of the common metals (mainly 1045 and 4140). Those are my favorite metals...


Ray

Lots of good info. Thanks Ray. I did some searching. That's a pretty impressive furnace you built! How well is it holding up? Would you use the wool again?

Below are two links that will be very informative and helpful.

Ray C Heat Treat Furnace Build: http://www.hobby-machinist.com/showthread.php?t=9929&highlight=heat

Reading Resources for Heat Treating: http://www.hobby-machinist.com/showthread.php?t=9653&highlight=heat

- - - Updated - - -

I've been using a muffle furnace for 25 years, your may keep temps even better!

View attachment 83683

Hi oldgoaly. Forgive my ignorance, but what is a Muffle Furnace? How is it different from the Kiln I bought? Thanks.

Bob

 

[frostheave]

I think you got a good deal. They go for over $600 new. If I'm not mistaken on this model the heating elements are embedded in the liner material and the entire liner would need to be replaced if one of the elements went out. You would need to contact Paragon to be sure.

You are correct Plas62. The element is embedded.
Paragon has a really nice website. One of the best I have seen. There is a 13 minute video describing the replacement procedure for the entire muffle with the embedded heating element. Looks pretty easy. The replacement cost for the muffle is $287.50. Actually a little less than I expected.

Bob

- - - Updated - - -

There's a ton of info on the web. I read everything I could find before I started. Youtube is a good source too, but nothing will replace experience. A lot of the charts I looked at before starting to HT had contradictory info. An example is 4140. One chart said to heat to about 1400 F. Another said 1550 F. I've heat treated revolver cylinders made from 4140 and tested to destruction. From that I was able to settle on 1425 to 1435 F for my application. You also have to know the alloy you're dealing with or heat treating it will be a crap shoot. Order from a reputable source and get the certification with the order. Most metal suppliers will provide a 'pedigree' for the material.

Don't forget you'll be tempering as well, once you harden. I just use a small $20 toaster oven for that. Reaches just over 565 F.

The torch takes a little more finesse, at least for me.

Thanks Rick. I sure have a lot to learn! The toaster oven is a great idea. By the way, how do you test a revolver cylinder to destruction???? Does it involve a big BANG?

Bob

 

[frostheave]

I have the same furnace, and it works great. I have used it for heat treating, soldering, and enamel work. Very useful to have. As far as replacing the the elements, that is one disadvantage on these smaller models, the elements are cast into the refractory (the larger ones are built out of individual fire bricks). For occasional use, it should not be an issue. I also recommend purchasing a small kiln shelf to sit on the bottom and protect the kiln from damage and contaminants. Kiln shelves are available from ceramic supply houses, and are pretty cheap.

Regarding the ramp rate, if you care about hitting a target temp, I recommend against setting the ramp rate to "full", the overshoot can be pretty severe. If you set it lower, it takes a little longer to reach temp, but the results will be more stable.

Good find, I think I spent close to $700 on mine new.

Thanks DMS. The small kiln shelf was the one thing missing. The seller lost it during their move. I will definitely pick one up. Makes perfect sense on the ramp settings. I was a little surprised at the cost of the complete replacement muffle at $287.50. Really not too bad considering...

Bob