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Riaan

exploding brass ingots

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Hi guys, 

I had a terrible experience last night.  I tested my new furnace and tried some brass ( pipe fittings and an ingot). The pipe fittings melted quite easily but the brass ingot did not want to go. After a while I decided to pour out what was pourable and save the rest for later when I figured out why it did not melt. But as soon as I moved the crucible the ingot exploded sending molten brass everywhere. I cannot find reason for this anywhere and would like to prevent this from happening in the future. 

Do you guys have any advice?

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Welcome aboard Riaan, glad to have you. If you'll put your general location in the header you'll be surprised how many of the Iforge gang live within visiting distance.

I'm not a caster, not since high school anyway but it sounds to me like you didn't break the scrap up well enough and the ingot not having reached liquidus trapped whatever was included. Any super cooled or super heated material only needs the least of disturbance to change phase sometimes nearly instantly, either flash freeze or boil. Most explosions in old steam boilers were caused by super heated water flashing into steam, whether by being splashed onto the boiler plate or by a pressure relief valve opening. The sudden pressure drop lowers the boiling temperature in the whole tank so it all flashes to steam.

About casting brass though. I have a friend who has become the go to caster for bronze monuments, placards, etc. within a few hundred miles and teaches almost nonstop. He won't touch brass, won't have it in his shop in case a student mistakenly adds it to a melt. The zinc in brass will produce zinc oxide fumes during a melt, even if the melt temp is below that where zinc burns on contact with air. While it's not heavy metal poisoning it's BAD for you and a large enough dose can be lethal.

Brass too dangerous for a professional caster to mess with at all. Given what I know about zinc fume fever from personal experience and how it can sneak up on a guy my advice is STOP MELTING BRASS!

That's it, learn to cast with something else, send the brass to the scrapper and buy good casting bronze, you can cast for a year for less than one ambulance ride.

Frosty The Lucky.

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jmccostomknives,

Not that I was aware of.

Frosty,

Thanx for the advice and my brass collection made it's way to the recyclingbin shortly after I read your post. I will start collecting bronze instead. Luckily I was wearing the correct PPE at the time. I've got brass blobs stuck to my gloves, apron and face mask. 

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in any good sized system the stuff that melts at the lowest temp will also be the stuff that hardens last and so the center may be preferentially made up of stuff that will melt first but be trapped by the shell.  This was actually an advantage in cannon barrels as you would then bore out the "trash" in the center.

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On 20-8-2016 at 8:40 PM, Frosty said:

Welcome aboard Riaan, glad to have you. If you'll put your general location in the header you'll be surprised how many of the Iforge gang live within visiting distance.

I'm not a caster, not since high school anyway but it sounds to me like you didn't break the scrap up well enough and the ingot not having reached liquidus trapped whatever was included. Any super cooled or super heated material only needs the least of disturbance to change phase sometimes nearly instantly, either flash freeze or boil. Most explosions in old steam boilers were caused by super heated water flashing into steam, whether by being splashed onto the boiler plate or by a pressure relief valve opening. The sudden pressure drop lowers the boiling temperature in the whole tank so it all flashes to steam.

About casting brass though. I have a friend who has become the go to caster for bronze monuments, placards, etc. within a few hundred miles and teaches almost nonstop. He won't touch brass, won't have it in his shop in case a student mistakenly adds it to a melt. The zinc in brass will produce zinc oxide fumes during a melt, even if the melt temp is below that where zinc burns on contact with air. While it's not heavy metal poisoning it's BAD for you and a large enough dose can be lethal.

Brass too dangerous for a professional caster to mess with at all. Given what I know about zinc fume fever from personal experience and how it can sneak up on a guy my advice is STOP MELTING BRASS!

That's it, learn to cast with something else, send the brass to the scrapper and buy good casting bronze, you can cast for a year for less than one ambulance ride.

Frosty The Lucky.

Fully agree with Frosty, see my first and last! brass ingots below.  Don’t need to repeat Frosty’s arguments and have some additions / remarks.

·         Used scrap brass from an old ship bull eye which also annealed with arsenic and phosphor

·         Got also a lot of zinc oxidizing all over the place (outside ventilated backyard)

Glad to use the coal forge after all and not the gas forge to heat the crucible (stuffed with oxide other ways).

While melting the scrap in the forge the bottom of the improvised cast iron crucible melted at the same time as the last bit of brass scrap.

However looking for decent bronze now and a serious carbon crucible and build an extra gas fired melting pot.

IMG_20171010_195833.jpg

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