Enamel Kiln for hardening?

[jimi43]

I was thinking out of the box today about getting ready for the Philly Forge project....WHEN I get my 01 delivered....and looked up and spied my little enamel kiln...

Now this little beauty gets up to about 1000 deg C so would it be acceptable to heat 01 stock in or do you need to actually fire it in charcoal.

Any thoughts on this?

Jim

 

[Harbo]

It's the temperature that's important and maintaining it for the required time - usually 1 hr/1" thickness pro rata.

A kiln would be ideal.

Rod

 

[CHJ]

'perfic' jimi43, in fact the lack of any risk of adding extra carbon to the outer skin is an advantage in maintaining the alloy purity.

 

[jimi43]

AH! Excellent! I will try this with pictures and let you know how I get on...the 01 hasn't arrived yet so will have to wait a while...

Cheers for the confirmation

Jim

 

[woodsworth]

how big is the Kiln? What a great idea.

 

[Aled Dafis]

I've been on the lookout for an enamelling kiln on the 'bay for a while. I't perfect for hardening, assuming that it has a thermostat. The temp. you're looking for is about 780Deg C IIRC, I'll check that out and gt back to you.

Remember to put a small nugget of charcoal in the kiln with the iron so that it scavenges all the free oxygen.

Cheers

Aled

 

[jimi43]

Great tip Aled!!! Ah well that was worth the score at the bootfair on spec then...I had no idea what I was going to use it for six months later...but I knew it would come in handy!!

The gauge on the right shows 1000 deg max...I think it runs at 930 deg C on full whack.

That's a shame...I was looking forward to a barbeque!!!!



Jim

 

[paininthe]

When I did hardening at college, many years ago, we used an oven but i'm sure we also put the tool in carbon pieces aswell. Whether this was for case hardening or to keep levels of carbon up I cannot fully recall.

 

[jimi43]

how big is the Kiln? What a great idea.

It's a twee enamelling one...I guess the hole in the front is about 8" cube but may be bigger...will check tomorrow.

So it all seems that I should try this then...will do...will come back here with the results.

Cheers guys.

Jim

 

[would not]

What are you trying to harden in that?

 

[jimi43]

What are you trying to harden in that?

I just went out and measured it now you guys had my interest and it is 8" deep by 6" wide by 3" high (the internal ceramic lined bit).

So that is perfect for irons up to a No.7 which is just under the 8"

It's similar to this one...an EFCO...but I think a tad older and larger.


CLICK


Jim

 

[ondablade]

Hi Jimi. My suggestion would be to do a bit of research on hardening and tempering processes for the grade of steel you are proposing to work with. A book like this covers the basics of carbon steels: http://www.amazon.co.uk/Hardening-Tempe ... 596&sr=1-1

Basically quench in the right medium to harden, and then reheat to the right temperature and let cool to temper. (get the blend of hardness and toughness you want)

Where it may get a bit more complicated is that some of the fancy tool steels now about contain alloying agents which alter the situation somewhat. Some will 'air harden' - air cooling is fast enough to cause then to harden without quenching.

My memory is fuzzy and I know little about the specifics, but i gather than some of the high alloy tool steels too are subject to 'grain growth'. That is when heated the crystals or grains enlarge (change to Austenite), and don't revert to the finer structure fast enough to avoid being trapped as the metal cools. So that when you sharpen it won't accept a fine enough edge.

The correct handling stops this, but i don't know how except that process timings probably become important and it's i think why cryogenic cooling (using liquid nitrogen or the like) is used.

Short article on cryogenic hardening: http://en.wikipedia.org/wiki/Cryogenic_hardening

It'd be nice if you could report your findings.

ian :wink:

 

[jimi43]

Hi Ian

Thanks for the information. I was going to start with 01 (gauge steel) as recommended by others here...

It seems that it is the simplest to harden and the process involves initial heating in the kiln...which I have confirmed can reach the required temperature...then quenching in oil (either old engine or veg) and then tempering after Sunday lunch in a cooling oven.

That was the initial plan with the charcoal BBQ Philly Forge approach...the only thing I have changed is using the kiln for the initial heating.

Cheers

Jim

 

[ondablade]

It should be fine Jimi as long as it's a steel containing carbon to the correct %...

ian

 

[wizer]

Good bit on this video, at around 8mins, about how Damascus style steel blades are made. Thought it might interest.

 

[jimi43]

Interesting vision on Damascus steel there Tom (once I had waded through the drivel....glad they hi fived with the right hands!)

I think I will give that a miss for DIY though...that power hammer looks serious stuff there mate!!

I guess you could do it by hand with little bits...I think they would not have that kit in the hills of Mount Fuji!!

Cheers mate

Jimi

 

[wizer]

yah I nearly turned off when they high fived. If that was me with a red hot lump of steel in a kiln and some guy was running all around me, he'd have eaten the damascus.

 

[jimi43]

Well I fired up the little kiln for the first time today...

Now that looks bleedin hot!

The analogue temperature probe and gauge show it reached about 900C:

and it was still going but VERY slowly...crept up to just over 900C ten minutes later...so I think this may very well be optimum...

Hardening:
Heat uniformly to 780/820°C until heated through. (If possible pre-heat at 300/500°C). Allow 30 minutes per 25 millimetre of ruling section and quench immediately in oil.

I also have a Keithley 870 digital temperature gauge which goes up to 1350C with a probe and I can put that in the hole that the existing prob sits as confirmation.

The idea will be to watch it go over 800C then switch off and let it drift back...it took nearly 30 minutes to drop to 600C with the power fully off...in fact I had to wait until it was safe to go inside!

What you think guys and gals?

Jim

 

[PeterBassett]

That's a very impressive bit of kit.

How hot does the outside get in use? Just thinking of dumping it outside in an emergency.

Pete

 

[jimi43]

That's a very impressive bit of kit.

How hot does the outside get in use? Just thinking of dumping it outside in an emergency.

Pete

Oh...you could pick it up Pete. I kept touching the top to check for that VERY reason!

I think if you left it for an hour it might get too hot but for the 30 mins it was on it was moveable.

Just a quick question for the experts here...what is "25mm of ruling section?"

Jim