Reactivity of Steel At Elevated Temperatures

Bob La Londe · 2023-07-03T20:49:38+00:00

Most of us know If you dump a ton of oxygen, heat, and fuel on steel it can burn. Burn may be technically arguable but a very violent reaction resulting in loss of material in its original form results.Some of us may know that there is some steel loss from reactions at a lower temperature when using a steel crucible for things like casting aluminum and even some material loss with steel molds used for casting aluminum many times.Still molten pourable aluminum is pretty hot.I test a lot of fishing tackle molds with lead. Its no where near the reactive temperatures mentioned above. I've got an RCBS Pro-Melt 20lb bottom pour lead pot. I've had it for years and its worked great for many of them. I don't think I have ever emptied it. The last few years its begun to drip. That's only a minor inconvenience really. Ask around the tackle making groups and you will find plenty of people who will say they all leak eventually. I stick an ingot mold under the spout to catch the drips when I am not actively pouring.Not only was my pot starting to drip the flow was getting to be less and less. Even with full head pressure (full pot) and the plunger set to maximum opening the flow was getting anemic. I was think various bits of debris must have gotten into the gate over time. Except it all floats to the top. Yeah, tungsten is heavier than lead, but I can't think of any other substance in my shop (well there are a couple gold trinkets in the safe) that wouldn't float on molten lead. Nothing that would be on the mold testing benches.I use pretty pure led purchased from a reputable source, but I still get a bit of dross on top. I figure its mostly lead oxide. I think some of it is some form of iron reactive from the melting pot, valve plunger, and valve nozzle. After draining and partial disassembly I am convinced that the steel was reacting at the mere 800F(+/-) of the molten lead. There was some metal growth like scaley rust "looking" corrosion in the pot itself, put...

Jul 03, 2023 Last reply: 3 years ago 23 Replies

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Jim Wilkins 3 years ago

Local Humidity. There's not really enough water in the air to do more that oxidize the top later.

------------------ King Tut's meteoritic iron dagger shows minimal rust after 3400 years in a dry climate. It's the lower one.

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Mike Spencer 3 years ago

Yes. The welded sculpture is rusty-brown but otherwise fine decades later. OTOH, the stone plinth, surrounding walkways and anything open to run-off rain water is permanently stained a similar brown. There was much flap about a public sculpture at Dalhousie University in Halifax years ago.

Um, well, not in the Arizona desert perhaps. Nova Scotia is very unline the Arizona desert.

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