CS199305B1 - Method of manufacturing ceramic smelting pots,e.g. for induction smelting furnaces - Google Patents

Description

The present invention relates to the manufacture of ceramic crucibles, in particular for an induction crucible crucible furnace or a vacuum melting furnace with an optional inert atmosphere.

Up to now, the production of ceramic crucibles has been carried out either by ramming the crucible directly in the induction melting furnace solenoid, or by ratcheting a new crucible with a metal template of a separate and rotary or pneumatic rammer. This process is very time consuming and practically means a loss of melting capacity of 24 hours. With expensive vacuum melters, this is then very expensive. According to another known method, the pails are usually pressed from refractory materials on presses under high specific pressure followed by sintering in high temperature annealing furnaces. In order to achieve perfect sintering, a small amount of flux is added to the refractory raw material. This reduces the softening point of the crucible material, but this is not desirable in terms of crucible life. The crucibles produced in this way are very expensive and often crack or melt refractory during melting.

According to the invention, these disadvantages are overcome by the use of precision casting by the method of exposible soluble or combustible exposable models for the production of ceramic crucibles, for example for melting induction furnaces and vacuum melting furnaces.

199 305

199 30S

Usually, 3 to 12 layers are possible depending on the size and shape of the crucible. · Highly stable materials such as AlgO ^, ZrSiOg, ^Zr0 2 can be used as refractory. » ^Μ β ° »silioidy, carbides, nitrides, borides, Tioga ΗίΌ ^ tho ^, ^p ° S em ^even mentioned and similar žáruvzdomin may be hydrolyzed ethyl silicate, zirconium, or similar substance, such as water glass.

The crucibles produced by the method of the invention are inexpensive and are not prone to cracking.

In fact, the crucibles produced according to the invention do not exhibit internal stresses as with the pressed crucibles, especially in the case of rapid temperature changes which always occur during the melting process. In contrast, in crucibles made according to the invention, the crucible structure is softer and more easily withstands heat shocks. Only the first or two functional ceramic layers need to be made of first-class materials such as ZrOg, BeO, etc. The made crucibles make it economically possible to use them for a single melting, which is the most metallurgically advantageous.

For example, a stencil made of steel, aluminum, copper, zinc or their alloys is produced in the production of the model. The template is provided with a wax coating by immersion in molten wax.

After the wax coating has solidified, this model is immersed in a ceramic slurry mixed with grit, filler and binder. After a few seconds, the model-stencil is removed from the ceramic slurry and the excess ceramics allowed to drain. Subsequently, the ceramic coating is covered with grit.

The ceramic coating thus prepared is allowed to solidify freely in the air or is cured by chemical agents or by depressurization. to achieve the required crucible thickness. After the final package has completely solidified, the metal template is heated to a temperature above the melting point of the wax coating by conventional means and the ceramic crucible is removed from the metal template. The crucible thus produced can be annealed to a temperature at which the wax residues are burnt, but also to a temperature at which partial or complete sintering occurs,

OF THE INVENTION

Claims (1)

OF THE INVENTION Application of steeping or potting of melted, soluble or combustible ♦ a ceramic slurry model as a manufacturing process for the production of ceramic crucibles, for example, for induction melting furnaces and vacuum melting furnaces.