Sciencemadness Discussion Board - ruined crucible

ruined crucible

Skrinkle - 1-7-2008 at 10:37

Hi guys,
I was attempting to make a low temperature alloy and i somehow ruined it. It's proportions were 3 parts tin, 5 parts lead, and 8 parts bismuth. I heated it with a blowtorch but it failed to liquefy. I turned it up some more and continued to heat it but it wouldn't melt fully and it much of it seems to be oxidized. Did i not thoroughly enough mix the metals, or did i over/under heat it? Any suggestions would be helpful.

[Edited on 1-7-2008 by Skrinkle]

12AX7 - 1-7-2008 at 11:36

And the crucible?...

Is your question about the metal, the crucible, or both?

What form of metals did you start with, how long did you heat it, to what temperature, and did you use any flux or cover?

Tim

Skrinkle - 1-7-2008 at 17:19

No flux, no cover, perhaps that would have been a good plan in retrospect. Sorry i forgot to mention the crucible's problem. There is a gray metallic mass at the bottom of the crucible that cannot be removed and oxides on the top. The metal appears to not have fused fully, it is mostly melted but still a little chunky. The tin and bismuth were granules and the lead was in various sized chunks.
I feel silly for not useing flux OR a cover now that you brought it up. The temperature is unknown to me because i didn't measure it. How would one go about taking the temperature of molten metal in the home lab anyway?

thanks

[Edited on 1-7-2008 by Skrinkle]

kilowatt - 1-7-2008 at 17:42

When a metal or alloy of known melting point is melting, that's the temperature you've got. If you can find the phase diagrams for alloys, you can tell a lot about that. High temperatures can be estimated fairly accurately by the color of their incandescence. K type thermocouples can measure pretty high temperature but the bare wire needs protected from molten metals. Many digital multimeters come standard with one.

ShadowWarrior4444 - 1-7-2008 at 17:44

Quote:

Originally posted by Skrinkle
No flux, no cover, perhaps that would have been a good plan in retrospect. Sorry i forgot to mention the crucible's problem. There is a gray metallic mass at the bottom of the crucible that cannot be removed and oxides on the top. The metal appears to not have fused fully, it is mostly melted but still a little chunky. The tin and bismuth were granules and the lead was in various sized chunks.
I feel silly for not useing flux OR a cover now that you brought it up. The temperature is unknown to me because i didn't measure it. How would one go about taking the temperature of molten metal in the home lab anyway?

thanks

[Edited on 1-7-2008 by Skrinkle]

An IR thermometer would be effective, also observation of the physical changes in the metal (melting points, red heat, white heat.)

Making these eutectic alloys may be better accomplished by melting the base metal first, then adding the others to it depending on the inter-solubility of the metals.

If you are attempting to make the eutectic alloy that is a liquid at room temperature, I do not believe you are using enough lead. I seem to recall an OTC method for making it that called for 60% Lead, 40% Tin solder; special note was made that 40% Lead, 60% Tin solder would not work.

[Edited on 7-1-2008 by ShadowWarrior4444]

Skrinkle - 2-7-2008 at 13:28

The alloy i was attempting to make was solid at room temperature but has a melting point only slightly higher than woods metal. Thank you for telling me about the temperature estimates. I know that the tin melted fine but the lead seemed to have the most trouble melting. Perhaps i should melt the lead first, then add the bismuth and tin? Do you guys think i require flux and/or a lid?

thanks

[Edited on 2-7-2008 by Skrinkle]