Method for producing casting molds, cores and basic mold materials regenerated therefrom
What are described is a process for producing casting molds, cores and mold base materials regenerated therefrom, a mixture for combination with a solution or dispersion comprising waterglass for production of casting molds and/or cores, a molding material mixture, a mold base material mixture, and a casting mold or a core. What is also described is the corresponding use of an amount of particulate sheet silicates having a d 90 of less than 45 μm or a corresponding mixture as additive for production of a molding material mixture comprising waterglass and particulate amorphous silicon dioxide, which is cured by chemical reaction of constituents of the molding material mixture with one another, in the production of a casting mold or a core, to facilitate the breakdown and/or to increase the regeneratability of the casting mold or core.
1. A process for producing casting molds, cores and mold base materials regenerated therefrom, comprising the following steps for production of a casting mold or a core:
providing or producing a molding material mixture comprising
a mold base material
a solution or dispersion comprising waterglass
0.1% to 3% by weight of particulate amorphous silicon dioxide
and, to facilitate the breakdown and/or to increase the regeneratability of the casting mold or the core,
one or more particulate sheet silicates in a total amount of 0.05% to 0.4% by weight, where the d 90 of the total amount of the sheet silicates is less than 45 μm,
where the percentages are each based on the total mass of the molding material mixture,
shaping the molding material mixture,
curing the molding material mixture by chemical reaction of constituents of the molding material mixture with one another, so as to result in the casting mold or the core.
2. The process as claimed in claim 1 , wherein the waterglass in the molding material mixture has a modular SiO 2 /M 2 O modulus in the range from 1.6 to 4.0, where M 2 O denotes the total amount of lithium oxide, sodium oxide and potassium oxide.
3. The process as claimed in claim 1 , wherein the average diameter of the mold base material particles is in the range from 100 μm to 600 μm.
4. The process as claimed in claim 1 , wherein the molding material mixture comprises fumed particulate amorphous silicon dioxide and/or the particulate amorphous silicon dioxide is a fumed particulate amorphous silicon dioxide.
5. The process as claimed in claim 1 , wherein the one or more particulate sheet silicates are present in the molding material mixture in a total amount of 0.1% to 0.4% by weight, where the d 90 of the total amount of the sheet silicates is less than 45 μm.
6. The process as claimed in claim 1 , comprising the providing or producing of a molding material mixture comprising
a mold base material,
a solution or dispersion comprising waterglass,
one or more particulate sheet silicates in a total amount of 0.1% to 0.4% by weight, where the d 90 of the total amount of the sheet silicates is less than 45 μm,
0.3% to 3% by weight, of particulate amorphous silicon dioxide, and
0.01% to 1% by weight of graphite,
where the percentages are each based on the total mass of the molding material mixture.
7. The process as claimed in claim 1 , wherein the mold base material comprises quartz sand,
and/or
wherein the curing of the molding material mixture
is assisted or brought about by heating the shaped molding material mixture,
is assisted or brought about by the hydrolysis of an ester, where
the alcohol is selected from the group consisting of C1-C8 monoalcohols, C1-C8 dialcohols, and C1-C8 trialcohols, and
the acid is selected from the group consisting of organic C2-C8 monocarboxylic acids, organic C2-C8 dicarboxylic acids, organic C2-C8 tricarboxylic acids,
or
is assisted or brought about by gassing of the shaped molding material mixture with a gas or gas mixture containing less than 1 mol % of CO 2 .
8. The process as claimed in claim 1 , wherein the casting mold produced or the core produced is heated temporarily at least in regions to a temperature of >900° C. such that the breakdown is subsequently facilitated, and/or wherein the casting mold produced or the core produced is heated temporarily at least in regions, by contacting with a metal melt in the casting operation, to a temperature of >900° C. such that the breakdown is subsequently facilitated.
9. The process as claimed in claim 8 for production of a regenerated mold base material from the casting mold produced or the core produced after the heating, comprising the following additional steps:
acting mechanically on the casting mold produced or the core produced, such that the casting mold or core breaks down,
producing the regenerated mold base material from the broken-down casting mold or the broken-down core.
10. The process as claimed in claim 1 , wherein the molding material mixture provided or produced contains a proportion of regenerated mold base material produced from a casting mold produced or a core produced after a heating, comprising the following additional steps:
acting mechanically on the casting mold produced or the core produced, such that the casting mold or core breaks down,
producing the regenerated mold base material from the broken-down casting mold or the broken-down core
and/or
wherein the shaping of the molding material mixture and/or the curing of the molding material mixture is effected by means of a 3D printer
and/or
wherein the shaping of the molding material mixture is effected in a 3D printing method and the curing of the molding material mixture is effected during the 3D printing operation and/or after the 3D printing operation.