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View Full Version : C A T A S T R O P H I C - F A I L U R E . . . LEE 4-20 Pb POT . . . 1,350*F.



OS OK
02-28-2017, 12:18 AM
Well, as some of you know...'Elvis Ammo' (he did the gel test for me when I ran a thread on casting .38/.357 SWC-HP's) has been casting Zinc, Zn, and loading and doing all the tests to see if it might be a viable alternative to Pb (should we ever be forced to find an alternative)...mostly doing it to see what he and his channel subscribers could learn.
Well, while he was casting last week his new 'Lee 4-20' pot had a catastrophic failure...a brand new casting pot he bought just to do the Zinc experimenting with...it blew a hole right out the bottom of the pot and melted through the steel pot liner the aluminum housing and then through the aluminum base and onto the wooden block that was under his pot! "WHAT...NO WAY?"

*Here's the story...
Lee 4-20 Lead Pot. "MAJOR FAILURE"! (https://www.youtube.com/watch?v=0z3k_gy1Plw)


*Ok, this is the information he found out from John Lee...Zn reacts badly with steel...
Lee 4-20 Lead Pot "Major Failure" (UPDATE)===) (https://www.youtube.com/watch?v=ixiEpJz63rw)


*Johnny's Reloading Bench used a PID control as a monitor to see just how hot a Lee 4-20 pot can get..."UNBELIEVEABLE!"
How Hot Will a Lee 4-20 Casting Furnace Get? (https://www.youtube.com/watch?v=B6nhuQvD9vw)


This will undoubtedly lead to quite a conversation about the above links...safety, why the failure, was it smart?, etc....

*For me, the first thing I think of is an 'UNATTENDED POT', there's the lesson for me...Then I think of getting that 'steel cookie sheet' I've been procastinating about and getting one put under each of my pots. No doubt, if Elvis hadn't been watching his pot his shop could have burned down.

reddog81
02-28-2017, 12:52 AM
I scanned through the first 2 videos and found them semi-interesting. It was very hard to watch a 15 minute video to get 30 seconds worth of information.

Bmi48219
02-28-2017, 01:39 AM
I wonder if a layer of DRY sand or cat litter under the pot would be a good safety measure. As long as it is dry the molten liquid would have a better chance of freezing up in the granular media before it started a fire. In the old days they used sand to line the iron runners when they tapped a blast furnace.

shoot-n-lead
02-28-2017, 01:58 AM
Spray on hi-temp coating would prevent that from happening as it would keep the zinc from interacting with the pot steel. And, I suspect our Lee posts don't have the highest quality steel in the pot.

Also, I suspect his pot got way over temp and if the temp had been monitored, that probably would not have happened.

Shiloh
02-28-2017, 07:59 AM
Mine won't go that high. Maybe if it was empties to around where the heating element is. That is WAY to hot for any casting.

Shiloh

OS OK
02-28-2017, 08:08 AM
You saw it on the PID control...1/3 pot full of Pb...1,350*F. The oxidized tin and antimony was a hard crust and glowing red.

lightman
02-28-2017, 09:13 AM
A cookie sheet under a pot is a good idea for any brand pot. I built a wooded box with 1-1/2 inch sides that my pot sits in and dump the finished bullets onto a folded towel. May convert to the cookie sheet. I just started casting on a new steel work bench so I'm not too worried about fire. But, caution is not a bad thing!

Ballistics in Scotland
02-28-2017, 09:28 AM
Spray on hi-temp coating would prevent that from happening as it would keep the zinc from interacting with the pot steel. And, I suspect our Lee posts don't have the highest quality steel in the pot.

Also, I suspect his pot got way over temp and if the temp had been monitored, that probably would not have happened.

A stainless pot on a burner is probably the solution. I don't think quality, as we usually judge it, of carbon steel would make any difference. I once sleeved an 1860s Webley revolver barrel, which produced as beautiful a bright, curling shaving as you could imagine. But although there was no pitting, the grain of the metal was visibly more accentuated by a century and a half of patina, than on the wrought iron frame.

rancher1913
02-28-2017, 09:36 AM
well I was thinking of making some zinc round balls, guess I will rethink that.

Chill Wills
02-28-2017, 09:42 AM
Tile "hardbacker" under the casting area. AKA Cement board - 1/2".
One sheet is cheap and large enough to cover the largest work table. Home Depot or Lowes is your friend.

Then the addition of steel cookie sheets is good on top of that.

daloper
02-28-2017, 10:25 AM
Like Chill Wills said. This is what I have covering my casting bench.

bkbville
02-28-2017, 10:32 AM
I guess we should read the instructions on our gear.

Did he bypass the thermal switch on his pot? I'm surprised it didn't cut out before 1350F

I like the cement board idea.

mozeppa
02-28-2017, 10:51 AM
I guess we should read the instructions on our gear.

Did he bypass the thermal switch on his pot? I'm surprised it didn't cut out before 1350F

I like the cement board idea.

nope...left it on high.

runfiverun
02-28-2017, 11:30 AM
they will go that high if the contact strips ['points' as I like to call it] are set that way.

my first 20 lb pot wouldn't get over 650 with a torch assisting it.
I adjusted the strips and couldn't keep it under 800-f in a snowstorm.
it took some fidgeting to get the thing settled down enough to have an actual range of 650-800 on the dial.

tomme boy
02-28-2017, 05:14 PM
So why is zinc sprayed onto steel to prevent rust? It is called galvanized steel??? If it ate the steel then it would not be made. The pot on the Lee melter is very thin. Something else went wrong

Tenbender
02-28-2017, 05:27 PM
If you were successful casting a zink boolit how would you size it ?

country gent
02-28-2017, 05:27 PM
There are several things that may have happened here. If zinc was being salvage from castings could some castings that were magnesium gotten in the mix? 1/3 full is where in relation to the heating coils and the thermocouple rheostats. Also could have been a flaw in the pot from forming it or the steel itself.

Geezer in NH
02-28-2017, 05:54 PM
Wow blame LEE for modifying there product so it fails.

NOT LEE"S FAULT

JSnover
02-28-2017, 06:05 PM
So why is zinc sprayed onto steel to prevent rust? It is called galvanized steel??? If it ate the steel then it would not be made. The pot on the Lee melter is very thin. Something else went wrong
I could be wrong but I think the reaction we're talking about here took place at a much higher temperature than the galvanizing process.

GONRA
02-28-2017, 06:26 PM
GONRA would love to cast Zn alloy boolits - cast in our conventional Pb boolit moulds.
But am chicken to melt Zn alloys in a common Pb alloy "furnace".
Stories like this reinforce it all.....

What "furnaces / melting pots" do you Professional Zn Alloy Casters use?

tomme boy
02-28-2017, 06:37 PM
Galvanized steel is made by dipping the steel in the molten zinc. So my guess is the steel failed because of the actual heated steel was starting to glow red and there was a flaw in the pot. Probably a extra thin section. These pots are super thin to begin with.

And no it is not Lee's fault. He is doing something that Lee never intended for you to do. If it were me I would make a ceramic pot and melt the zinc that way.

tomme boy
02-28-2017, 06:50 PM
The only thing I am finding is you don't mix stainless steel and zinc. They will react badly with each other. Sooo, is the pot in the Lee melter SS???

OS OK
02-28-2017, 07:30 PM
Galvanized steel is made by dipping the steel in the molten zinc. So my guess is the steel failed because of the actual heated steel was starting to glow red and there was a flaw in the pot. Probably a extra thin section. These pots are super thin to begin with.

And no it is not Lee's fault. He is doing something that Lee never intended for you to do. If it were me I would make a ceramic pot and melt the zinc that way.

I imagine a hot spot on the bottom of the pot liner there glowing red and the weight of the melt kept bulging on it till the thin metal ballooned out and separated and poured through...then the aluminum skin was nothing to that temp. of the Zink.
You noticed the hole in the base plate of the pot also?

Boolseye
02-28-2017, 08:19 PM
Those pots weren't built to get filled with molten zinc.
Glad nobody got hurt.

tomme boy
02-28-2017, 09:33 PM
The bottom plate is kind of a mystery. It should not have melted like that. Unless the temp of the pot was over 1200 deg. So I am also thinking the rheostat was stuck and the temp skyrocketed.

Boolseye
02-28-2017, 09:36 PM
I imagine a hot spot on the bottom of the pot liner there glowing red and the weight of the melt kept bulging on it till the thin metal ballooned out and separated and poured through...then the aluminum skin was nothing to that temp. of the Zink.
You noticed the hole in the base plate of the pot also?

That sounds right to me. Man, the burn that would have caused....

OS OK
02-28-2017, 10:22 PM
That kinda reminds me of the gal selling stuff at the baseball game a couple light years ago...had her little box-O-goodies marching up and down the bleachers...calling out..."Hot Nuts!"

pakmc
03-01-2017, 07:04 AM
I had the spout fall off my 20lb. Lee pot with 20 lb.s of liquid lead in it. I didn't think this old man could move that fast. with the dripping of the spout I would tap it with a hammer(very lightly) to stop it dripping. these ain't much lip on the spout(not much at all) now I use a screw driver to just turn the "plug" a little to stop the dripping. but they do(will) drip. Lee send me a new spout and a back up for the new one. after I send pictures of the pot and the hole in the bottom of it.(yes, all the lead drained out.)

TexasGrunt
03-01-2017, 09:33 AM
The bottom plate is kind of a mystery. It should not have melted like that. Unless the temp of the pot was over 1200 deg. So I am also thinking the rheostat was stuck and the temp skyrocketed.

Please read the complete thread before commenting.

Temp was controlled with a PID and was 1350°. This was stated by the OP.

OS OK
03-01-2017, 10:20 AM
Actually Grunt...'Elvis Ammo' was casting with the temp. dial full throttle and did not have a PID control.
A fellow Y-Tuber...at 'Johnny's Reloading Bench' was following Elvis's Zinc casting results and saw this mishap...he then decided to use his PID control to 'monitor only' his Lee 4-20 pot (1/3 full of Pb) to see just how high this pot would go...given that it was set on 'full throttle' and left to run that way.
That is where the 1,350*F. temperature came from...it's in his link, the last one I posted.

therealhitman
03-01-2017, 02:03 PM
Actually Grunt...'Elvis Ammo' was casting with the temp. dial full throttle and did not have a PID control.
A fellow Y-Tuber...at 'Johnny's Reloading Bench' was following Elvis's Zinc casting results and saw this mishap...he then decided to use his PID control to 'monitor only' his Lee 4-20 pot (1/3 full of Pb) to see just how high this pot would go...given that it was set on 'full throttle' and left to run that way.
That is where the 1,350*F. temperature came from...it's in his link, the last one I posted.

Johnny is a character. I look forward to his vids. Lots of loading and range testing, definitely my favorite YouTube casting/loading channel. Lots of great info on 300AAC sub loads and 6.5 Grendel stuff. I am supremely jealous in that he has quit his job of many years and intends to spend a full year just fishing, hunting, shooting and loading. He is actually building Elvis a PID and donating to the Zn experiment cause. Nice guy!

OS OK
03-01-2017, 02:12 PM
I noted that generous offer to Elvis too...that's when I decided to subscribe to his channel, that was a most gracious offer.

I know Elvis will be grateful...he's a nice fella too and tries hard to get it right.

tomme boy
03-01-2017, 02:16 PM
Please read the complete thread before commenting.

Temp was controlled with a PID and was 1350°. This was stated by the OP.You better re-read the post yourself before commenting. It was someone else that did the test with the PID NOT the OP or the person that the pot failed with.

These pots are all different. Some barley get hot enough to melt lead and others get way hot. Using the PID bypasses the rheostat. That was why it got as hot as it did.

dragon813gt
03-01-2017, 05:57 PM
The PID does not bypass the rheostat. All you're doing is controlling the 120v to the pot. The rheostat is still wired in and has control of the highest temp achievable.

I had one of the smaller pots, filled w/ potassium nitrate, up to 1200 and it would have gone higher if I set the PID higher. That was the most dangerous way I've ever annealed cases and quickly abandoned the method.

OS OK
03-01-2017, 06:29 PM
You better re-read the post yourself before commenting. It was someone else that did the test with the PID NOT the OP or the person that the pot failed with.

These pots are all different. Some barley get hot enough to melt lead and others get way hot. Using the PID bypasses the rheostat. That was why it got as hot as it did.

Johnny used the PID control to monitor the pot temp. only. He plugged the pot into the wall outlet and set the pot to High...he showed the plug on the back of the PID to prove that it wasn't controlling anything, only monitoring.

tomme boy
03-01-2017, 08:09 PM
Still the fact that these pots vary on how they work. Mine only goes to 950 deg. I know how a rheostat works. And you can take it completely out. It is not needed. The PID becomes the rheostat. I have installed hundreds of these and programed them when I was still working. And I bet you have handled things that I personally have worked on that was controlled by a PID that I installed and programed.

dragon813gt
03-01-2017, 08:23 PM
Still the fact that these pots vary on how they work. Mine only goes to 950 deg. I know how a rheostat works. And you can take it completely out. It is not needed. The PID becomes the rheostat. I have installed hundreds of these and programed them when I was still working. And I bet you have handled things that I personally have worked on that was controlled by a PID that I installed and programed.

You can take them out. But I don't know of anyone that has done this w/ their pots. The rheostat is still in the circuit. This way if the PID or thermocouple fails you plug the pot in like normal and cast like you used to.

longbow
03-01-2017, 08:31 PM
Zinc galvanizing is usually put on steel strip run through a molten bath of zinc... one pas to put a rust resistant coating on the steel. the zinc doesn't "eat" the steel after it is applied. However, long term exposure to molten zinc will eroded the steel (or cast iron) away a bit at a time as it reacts at a microscopic level.

The zinc plant where I work goes through lots of cast iron moulds and steel jumbo pins that get "eaten" up by molten zinc but they are repeatedly exposed so gradually dissolve a bit at a time.

Your pot and boolit moulds will do the same and it is no surprise that the Lee pot failed, in fact it would be a surprise if it didn't. try it with an RCBS or any other steel pot and the results will be the same.

If you want to do any significant amount of melting and casting of zinc boolits, you'd be better off getting a cast iron pot with heavy wall and heat it over a propane burner. heavy steel would work too but steel gets eaten away faster when exposed to molten zinc. Even 316 stainless steel is not suitable for the application but I am sure there are exotic alloys that would last indefinitely ~ like CD4MCU ~ but they are expensive and many are difficult to machine or work. All in all a refractory lined pot would be best as the zinc is kept away from the surface of the metal then as the refractory breaks down it can be replaced.

Longbow

OS OK
03-01-2017, 08:46 PM
Still the fact that these pots vary on how they work. Mine only goes to 950 deg. I know how a rheostat works. And you can take it completely out. It is not needed. The PID becomes the rheostat. I have installed hundreds of these and programed them when I was still working. And I bet you have handled things that I personally have worked on that was controlled by a PID that I installed and programed.

The PID becomes (replaces) the rheostat('s function). [The PID is a temp. controlled 'on - off' switch.] I'm sure you know that but your explanation might confuse others. Rheostats are just heavy duty 'restive wire'-wound (in this case 'variable') potentiometers.

rupe01
03-02-2017, 09:03 PM
You can take them out. But I don't know of anyone that has done this w/ their pots. The rheostat is still in the circuit. This way if the PID or thermocouple fails you plug the pot in like normal and cast like you used to.

I hadn't seen anyone take the rheostat out of the circuit either.....until i saw this video. Just a different way of doing the same job , i guess:
https://www.youtube.com/watch?v=vwDgkrNMJQA&t=612s

(You can jump to around the 5 minute mark to where he shows it, if you dont want to watch the entire video)

tomme boy
03-02-2017, 09:37 PM
You have not seen it because no one knew you could. Everyone is just copying everyone else on how you put these together. Youtube makes lots of people experts you know!