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.

[tomme boy]

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]

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]

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]

Those pots weren't built to get filled with molten zinc.
Glad nobody got hurt.

[tomme boy]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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)