Method for constructing molds and cores layer by layer by means of a binder containing water glass, and a binder containing water glass

Abstract

The invention relates to a binder, which contains water glass and further a phosphate or a borate or both. The invention further relates to a method for constructing molds and cores layer by layer, the molds and cores comprising a construction material mixture, which at least comprises a refractory molding base material, and the binder. In order to produce the molds and cores layer by layer in 3-D printing, the refractory molding base material is applied layer by layer and is selectively printed with the binder layer by layer, and consequently a body corresponding to the molds or cores is constructed and the molds or cores are released after the unbonded construction material mixture has been removed.

Description

[0001]The invention relates to a method for constructing molds and cores layer by layer, the molds and cores comprising a refractory molding base material and a binder containing least one aqueous alkali silicate solution and further a phosphate or a borate or both. In order to produce molds and cores layer by layer in 3-D printing it is necessary to apply a refractory molding base material layer by layer and to selectively print each with the binder. Furthermore, the invention relates to molds or cores produced in this way.PRIOR ART[0002]Casting molds essentially consist of cores and molds, which represent the negative forms of the casting to be produced. These cores and molds consist of a refractory material, for example quartz sand, and a suitable binder which imparts sufficient mechanical strength to the casting mold after removal from the forming die. For the production of casting molds, therefore, a refractory molding base material is used, which is coated with a suitable bind...

AI Technical Summary

Benefits of technology

[0022]2. sufficient thermostability, particularly suitable for metal casting, to prevent deformation of the casting mold during the casting process.

[0027]A rapid clogging of the nozzles or a rapid film formation at the module of the print head is due to an increased reactivity of the binder. The reactivity of the binder can be controlled by its chemical composition as well as the thermal stability of the binder. In view of the application in the area of the 3-D printing method, on the one hand, a low reactivity of the binder is required in order to avoid impairment of the print head and to control the curing of the binder, but on the other hand, high thermal stability is desired also in order to prevent the produced casting molds from deforming during the casting operation and thus resulting in poor dimensional stability of the casting. The thermostability and reactivity of the binder depend in the same manner on the chemical composition of the binder, i. e., the higher the reactivity, the higher the thermal stability. It is the subject matter of this invention to disclose a suitable binder composition which ensures a sufficiently high thermostability of the casting molds at sufficiently low reactivity of the binder.

Problems solved by technology

The material of the casting mold then has to decompose under the action of the heat given off by the metal so that it loses its mechanical strength, i. e. cohesion between individual particles / granules of the refractory material is lost.

Thus, the binder is consumed unnecessarily.

DE 102011053205 A1, however, does not provide information as to which water glass compositions can be used.

The large amounts of water (e. g. up to 60% by weight water) are thought to be disadvantageous since they are difficult to handle.

However, such a method is very complex and cost-intensive.