Precautions while melting shot.

[Amol Gupta]

Here is a reference to one of sreetips videos of melting silver shot.



@11:55 we can see an explosion as he melts the shot, I'd like some experts to comments on it.
A few thoughts in my mind.
He uses a slant wooden plank with running water to create shots.
Of the limited reading I have the cause of explosions seems to be the evaporated water that tries to escape the liquid at high pressure often violently.
From what I can see sreetips always tries to pour the molten metal at the junction of water and air on the wooden plank, he does not dump the metal directly in water which makes sense as it would lead to an explosion.
My question is why he doesn't pour the molten metal higher on the plank as it seems safer as highlted by the green circle in the image, are there any drawback to pouring metals higher on the plank?
I was also wondering if the height from which metal is poured affects the characteristics of the granules.

My second concern is one with respect to handling crucibles.
Here is a reference to another video



@3:20 we can see as he put the hot crucible on the surface the crucible seems to pop I was curious If someone has experienced the same and what causes such popping.
I have read graphite crucibles at high temperatures oxidise quicker reducing life expectancy and thus exposure to air should be limited.
Any other precautions while handling graphite crucibles in general will be helpful.

Thanks.

 

[Yggdrasil]

Here is a reference to one of sreetips videos of melting silver shot.



@11:55 we can see an explosion as he melts the shot, I'd like some experts to comments on it.
A few thoughts in my mind.
He uses a slant wooden plank with running water to create shots.
Of the limited reading I have the cause of explosions seems to be the evaporated water that tries to escape the liquid at high pressure often violently.
From what I can see sreetips always tries to pour the molten metal at the junction of water and air on the wooden plank, he does not dump the metal directly in water which makes sense as it would lead to an explosion.
My question is why he doesn't pour the molten metal higher on the plank as it seems safer as highlted by the green circle in the image, are there any drawback to pouring metals higher on the plank?
I was also wondering if the height from which metal is poured affects the characteristics of the granules.

My second concern is one with respect to handling crucibles.
Here is a reference to another video



@3:20 we can see as he put the hot crucible on the surface the crucible seems to pop I was curious If someone has experienced the same and what causes such popping.
I have read graphite crucibles at high temperatures oxidise quicker reducing life expectancy and thus exposure to air should be limited.
Any other precautions while handling graphite crucibles in general will be helpful.

Thanks.

Ordinary crucibles are used for this no need for Graphite crucibles..
Often one makes a crucible with drilled holes that hangs close to the water and pour the liquid metal into it.
It have to be very hot.
There was a discussion a few days ago regarding this.

 

[Amol Gupta]

Any idea of the crucible popping as in the second video...?

 

[justinhcase]

I was corn-flaking some inquartation and instead of a slow steady pour of molten metal, I fumbled the pour and dumped the entire crucible content into my water drum.
What a bang! Like a flash/bang without the flash.
Luckily the explosion was at the very bottom of the drum, so it was contained under the water.
The result was some of the finest, sand-like gold I have ever seen.
If you could replicate the process, it would be interesting.

 

[Amol Gupta]

I was corn-flaking some inquartation and instead of a slow steady pour of molten metal, I fumbled the pour and dumped the entire crucible content into my water drum.
What a bang! Like a flash/bang without the flash.
Luckily the explosion was at the very bottom of the drum, so it was contained under the water.
The result was some of the finest, sand-like gold I have ever seen.
If you could replicate the process, it would be interesting.

Looks scary actually.

 

[4metals]

I watched the sreetips video in the first post and have some possible answers for this question.

@11:55 we can see an explosion as he melts the shot, I'd like some experts to comments on it.

I've done a few melts in my day and, as a result seen a few explosions as well. When 2 materials at such temperature extremes as the unmelted powder and the hot furnace mix excitement is a possibility.

I cannot be certain as the audio did not say what was added to the crucible as it went in. But this is my 2¢.

My assumption is the melt was primarily cement silver. But there was another bucket which I will call the mystery bucket that appears twice. The first melt was all from the cement silver bucket. Poured fine, no surprises. Then in the next melt he added a scoop from the mystery bucket as well. That was primarily gray with something white as well, but mostly gray. More cement silver went on top and the melt poured nicely as well.

Then he added more cement silver to the empty crucible and another scoop from the mystery bucket which by now was much more white in appearance. On top of that he added more cement silver. This melted fine and instead of pouring he did something I would caution anyone melting metals not to do. He added more cement silver on to the molten pool of metal. As it did not react I know the silver was dry. But as a general rule never add anything (flux being the exception) to a crucible of molten metal because any moisture in the solid will cause a rapid and violent steam explosion. Thankfully he was fine, his silver was dry.

When he poured this crucible full was when the explosion (actually an experienced melter would call that a pop!) happened. I assume what caused that was the white material in the mystery bucket, which I assume was flux which when molten usually pours out first. Flux is typically glass like and reacts that way when it hits water. That is my guess.

I guess we will never know until the contents of the mystery bucket is revealed.

I was never a fan of using the vertical lifting tongs to pour, I much prefer using the vertical lift tongs to pick up the crucible, put it down and pour with pouring tongs. There is a lot more control for the fine stream you are looking for.

 

[Amol Gupta]

I watched the sreetips video in the first post and have some possible answers for this question.


I've done a few melts in my day and, as a result seen a few explosions as well. When 2 materials at such temperature extremes as the unmelted powder and the hot furnace mix excitement is a possibility.

I cannot be certain as the audio did not say what was added to the crucible as it went in. But this is my 2¢.

My assumption is the melt was primarily cement silver. But there was another bucket which I will call the mystery bucket that appears twice. The first melt was all from the cement silver bucket. Poured fine, no surprises. Then in the next melt he added a scoop from the mystery bucket as well. That was primarily gray with something white as well, but mostly gray. More cement silver went on top and the melt poured nicely as well.

Then he added more cement silver to the empty crucible and another scoop from the mystery bucket which by now was much more white in appearance. On top of that he added more cement silver. This melted fine and instead of pouring he did something I would caution anyone melting metals not to do. He added more cement silver on to the molten pool of metal. As it did not react I know the silver was dry. But as a general rule never add anything (flux being the exception) to a crucible of molten metal because any moisture in the solid will cause a rapid and violent steam explosion. Thankfully he was fine, his silver was dry.

When he poured this crucible full was when the explosion (actually an experienced melter would call that a pop!) happened. I assume what caused that was the white material in the mystery bucket, which I assume was flux which when molten usually pours out first. Flux is typically glass like and reacts that way when it hits water. That is my guess.

I guess we will never know until the contents of the mystery bucket is revealed.

I was never a fan of using the vertical lifting tongs to pour, I much prefer using the vertical lift tongs to pick up the crucible, put it down and pour with pouring tongs. There is a lot more control for the fine stream you are looking for.

I have seen people dropping of the flux before pouring the metal shots, I guess now I know why.

 

[Amol Gupta]

For anybody interested here is a video explaining one of the prominent reason for such explosions



There are further explanations in the video comment section.

 

[RichardSukhoi]

I watched the sreetips video in the first post and have some possible answers for this question.


I've done a few melts in my day and, as a result seen a few explosions as well. When 2 materials at such temperature extremes as the unmelted powder and the hot furnace mix excitement is a possibility.

I cannot be certain as the audio did not say what was added to the crucible as it went in. But this is my 2¢.

My assumption is the melt was primarily cement silver. But there was another bucket which I will call the mystery bucket that appears twice. The first melt was all from the cement silver bucket. Poured fine, no surprises. Then in the next melt he added a scoop from the mystery bucket as well. That was primarily gray with something white as well, but mostly gray. More cement silver went on top and the melt poured nicely as well.

Then he added more cement silver to the empty crucible and another scoop from the mystery bucket which by now was much more white in appearance. On top of that he added more cement silver. This melted fine and instead of pouring he did something I would caution anyone melting metals not to do. He added more cement silver on to the molten pool of metal. As it did not react I know the silver was dry. But as a general rule never add anything (flux being the exception) to a crucible of molten metal because any moisture in the solid will cause a rapid and violent steam explosion. Thankfully he was fine, his silver was dry.

When he poured this crucible full was when the explosion (actually an experienced melter would call that a pop!) happened. I assume what caused that was the white material in the mystery bucket, which I assume was flux which when molten usually pours out first. Flux is typically glass like and reacts that way when it hits water. That is my guess.

I guess we will never know until the contents of the mystery bucket is revealed.

I was never a fan of using the vertical lifting tongs to pour, I much prefer using the vertical lift tongs to pick up the crucible, put it down and pour with pouring tongs. There is a lot more control for the fine stream you are looking for.

Off topic is a story from a former colleague. When young he got a job at the aluminum foundry. He was wearing standard Foundry garb. They were pouring molten metal into very large ingot molds. After each use the molds are pressure washed and normally allowed to dry, except the work has fallen a bit behind. He watched the first pour. Then the second made sone noises and he spoke out loud asking what they were. Then the third was being poured and very ominous sounds emanated, he looked over, he was suddenly alone. He woke up in ambulance. My miracle he was in a shadow and the baseball chunks of aluminum smashed equipment all around him but not him. But the flash steam had burned much of his body. The suit was not steam proof. He showed me his legs where below boot was fine, and above jacket line was fine, but above and below the knees all scarred as well as numerous other places where the steam had gotten in. He never forgave his coworkers for scattering without tugging him along and after recovery went back to school.

 

[Darkthirty]

For anybody interested here is a video explaining one of the prominent reason for such explosions



There are further explanations in the video comment section.

When you consider water/steam conversion is 1/1700, a video isn't really necessary

 

[4metals]

For anybody interested here is a video explaining one of the prominent reason for such explosions

Personally I think the backyard scientist is a fool. That "experiment" was more for you tube clicks than science. I feel bad for his relatives who for years will have to deal with shards of glass that he didn't pick up out of the lawn.

 

[Amol Gupta]

He might seem like an ir-responsible lad but he did drive home the point of why to pour the metal slowly.