Process for producing and using a ceramic shell as casting mould with reducing properties

摘要

The invention relates to a process for producing ceramic shells as a casting mould, in which a) a fusible or releasable pattern of a part to be cast is produced, b) the pattern is dipped into an immersion mass consisting of a slurry of a refractory material and a binder, in order to form a moist coating on the pattern, c) a coarse, refractory powder is sprinkled on the coating, d) the coating is dried, e) steps b), c) and d) are repeated until the shell has reached the desired thickness. The invention consists in adding to the immersion mass and/or the coarse refractory powder a protective ceramic substance, to which, during production, in the molten state, carbon has been fed which is capable of chemically binding oxygen at the time of cooling of the casting, essentially at mould temperatures above the firing temperature of the casting mould, and thus of preventing surface (skin) decarburisation and surface defects in carbon-containing steels and alloys.