2006-11-13 00:49:31 · 5 answers · asked by ? 5 in Science & Mathematics ➔ Engineering
Good question!
If you used a metal crucible, the steel would definitely eat through the walls and the molten steel would leak out - very bad! Even if you used tungsten (the highest melting point metal), the steel would form a lower melting point alloy (a 'eutectic') and you'd contaminate your steel as well as attack the tungsten crucible.
A 'eutectic' alloy is composed of at least two metals and has a lower temperature melting point alloy than any of its individual components. The reason this happens is similar to what happens when you put salt down on the roadway: it lowers the melting point.
I've seen molten aluminum eat through stainless crucibles - you should never melt or hold liquid metals in metal containers without checking to see if a lower melting point eutectic forms: you'll need a phase diagram for this purpose.
That's why almost always people line the crucible with some kind of ceramic coating, or use a ceramic crucible. The basic reason is that the ceramic (composed typically of a metal and an oxide) are ALREADY fully chemically reacted with one another and have little or no affinity for molten steel. The ceramic is specially chosen to have a higher melting point than steel, and the composition varies depending what steel you're casting, cost, cleanliness, etc.
The second trick you can use is called the 'skull' melting method, where you only melt and pour out the interior molten contents of the crucible: the crucible walls are cooled and a thin layer of metal adheres to the crucible wall that does not melt (by design), leaving a 'skull' insulator, so no crucible wall melting or contamination of the molten steel is possible. This is typically used with induction melted metals.
2006-11-13 12:04:18 · answer #1 · answered by jimdempster 4 · 0⤊ 0⤋
the thing in which the melted steel is in has a higher melting point than the steel
2006-11-13 00:53:16 · answer #2 · answered by Anonymous · 0⤊ 0⤋
made of metals with higher melting points.
2006-11-13 00:51:09 · answer #3 · answered by David B 6 · 0⤊ 0⤋
Two reasons, either they're more refractory (higher melting point) like various ceramics, or they're cooled via liquid cooling or air cooling.
2006-11-13 02:50:32 · answer #4 · answered by Anonymous · 0⤊ 0⤋
What makes the melting pot then?
2015-08-28 07:51:35 · answer #5 · answered by robert 1 · 0⤊ 0⤋