Our high performance crucibles are manufactured to withstand the most severe melting conditions either in air or vacuum furnaces. They are developed to address the issues of thermal shock, saturation and erosion.
Induction melting in crucibles creates various metal and alloy interactions. The interactions will largely depend on the crucible composition, the alloys melted, and melting practices. The compositions are designed to be compatible with most alloys, whether they are basic or acidic in nature.
Our crucibles are manufactured in alumina, magnesia, mullite and alumina zirconia for the more extreme situations. While the densities of alumina and magnesia are similar, their thermal expansion and PH level vary. In choosing a crucible, the alloy, melting techniques, thermal cycling, and holding period at tap temperature should all be considered.
Common causes of failure are wetting and penetration of the melt into the crucible. This saturation is prevalent below the melt line while the high temperature gradient at the melt line and the relatively cooler atmosphere above the melt line both play a part in the degradation of the crucible, usually presenting itself as thermal shock cracking in that area. In most cases, erosion is noticed at the slag melt interface. Long tap times and low bath heights can be a major contributor to erosion in this area of the crucible. Alloy additions, fluxes and slag coagulants can also be detrimental to the crucibles and should be carefully considered and observed as a potential source of saturation and erosion. Fluid and aggressive slags can cause destruction of the bonding of the crucible and can lead to either build up or erosion on the walls and eventual failure of the crucible.
Proper installation of the backup refractory and top cap can aid in longer crucible life. The backup should be chosen for density and the ability to contain the crucible in compression and freeze molten metal in the event of the crucible cracking so coil damage can be avoided.
Our metal melting crucibles are manufactured in capacities from 50 lbs to 4000 lbs with the ability to accommodate special shapes and compositions.
For additional information on popular crucibles, please visit the following pages: