Method for the production of a core sand and/or molding sand for casting purposes
A method for producing a core sand and/or molding sand for casting purposes mixes a basic granular mineral molding material such as silica sand with an additive based on an organic or inorganic component, a binding agent being optionally added. The additive is coarsely ground prior to the mixing process, more than 50 percent by weight of the grains having a minimum size of approximately 0.05 mm.
1. A method for producing a core sand or molding sand for casting purposes comprising the steps of:
(a) providing an additive having an organic component and an inorganic mineral component, the organic component containing over 50 wt.-% carbon and less than 30 wt.-% oxygen, the additive having a water content of less than 10 wt.-% and emitting a gas amount in a temperature range of 250° C. to 800° C. of less than 500 ml/g;
(b) coarsely grinding or pelletizing additive grains of the additive so that more than 50 wt.-% of the additive grains have a grain size of at least approximately 0.05 mm; and
(c) subsequently mixing a granular mineral molding material with molding material grains having an average grain size less than 0.50 mm with the additive grains to form a finished mixture comprising over 90 wt.-% of the molding material and a residual amount comprising the additive and if necessary binding agents.
2. The method according to claim 1 , wherein the organic component of the additive constitutes up to 90 wt.-%.
3. The method according to claim 2 , wherein the oxygen content, of the organic component of the additive is less than 20 wt.-%.
4. The method according to claim 2 , wherein the organic component contains up to 50 to 98 wt.-% carbon, with reference to the weight of the component.
5. The method according to claim 2 , wherein the organic component is selected from the group consisting of coal, hydrocarbon resins, bitumen, and mixtures thereof.
6. The method according to claim 1 , wherein the gas amount emitted by the additive is less than 350 ml/g when heated until a temperature in the range of 250° C. to 800° C. is reached.
7. The method according to claim 1 , wherein more than 70 wt.-% of the additive grains possess a grain size of at least approximately 0.05 mm.
8. The method according to claim 7 , wherein more than 90 wt.-% of the additive grains possess a grain size of at least approximately 0.09 mm.
9. The method according to claim 1 , wherein the inorganic component constitutes up to 80 wt.-% of the additive.
10. A method for producing a core sand or molding sand for casting purposes comprising the steps of:
(a) impregnating and coating granular mineral molding sand grains having an average grain size less than 0.50 mm with an additive having an organic component and an inorganic mineral component, the organic component containing over 50 wt.-% carbon and less than 30 wt.-% oxygen, the additive having a water content of less than 10 wt.-% and emitting a gas amount in a temperature range of 250° C. to 800° C. of less than 500 ml/g, to form aggregate grains of molding material grains impregnated and encased with the additive; and
(b) coarsely grinding and pelletizing the aggregate grains to form a finished mixture wherein more than 50 wt.-% of the additive grains have a grain size of at least approximately 0.05 mm, the finished mixture comprising over 90 wt.-% of the molding material and a residual amount comprising the additive and if necessary binding agents.
11. The method according to claim 10 , wherein the aggregate grains have a sealed surface.