Casting Core Hierarchical Pore Structure for Stability and Removal
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Solution Overview
Problem
Casting cores used in molds lack dimensional stability during the casting process and face challenges in easy removal of the core material from the cast component, with existing binder systems often leading to thermal breakdown and harmful gas emissions.
Innovation Solution
A casting core composed of ceramic particles bound with a silica sol, featuring a hierarchical pore structure where the average pore size increases from the outside to the inside, achieved through the freeze gelation process, providing a dense surface for stability and porous interior for easy removal, without significant volume change or gas formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If organic binders (synthetic resins, protein binders) are used to produce casting cores, then the cores can be formed into required shapes through pressing, core shooting or casting, but the thermal breakdown of the organic binder during the casting process weakens the core structure and enables removal of core material, which is associated with emission of environmentally harmful gases
Solution Approach 1:
The patent changes the chemical composition parameter of the binder from organic to inorganic (silica sol), fundamentally altering the material properties to eliminate harmful emissions while maintaining manufacturing capabilities. The silica sol binder system replaces organic binders entirely, changing the chemical basis of the core material.
Solution Approach 2:
The patent converts the potential harm of binder thermal breakdown into a benefit by using an inorganic binder that does not emit harmful gases. The silica sol binder, when subjected to heat, does not decompose into harmful substances but rather provides thermal stability and maintains core integrity throughout the casting process.
2Strength
If the casting core has high strength and dimensional stability during casting, then the core remains stable under casting pressure, but the core material becomes difficult to remove from the cast component after casting
Solution Approach 1:
The patent applies different pore size characteristics to different regions of the core. The outer region has smaller pores for strength and stability during casting, while the inner region has larger pores that facilitate easy removal after casting. This spatial differentiation of structural properties resolves the contradiction between maintaining strength and enabling removal.
Solution Approach 2:
The core structure is segmented into functional zones with different pore characteristics. The heterogeneous pore structure divides the core into regions serving different functions: the outer dense region provides structural integrity, while the inner porous region enables easy removal, allowing the core to satisfy both contradictory requirements simultaneously.
3Strength
If waterglass is used as inorganic silicate binder and solidified by gassing with CO2 or by addition of esters or acids or by drying, then the binder provides sufficient core strength, but a good demoldability must also be ensured and the heat input must loosen the structure while sintering must be prevented
Solution Approach 1:
The patent changes the binder system from waterglass requiring chemical activation (CO2 gassing, esters, or acids) to a silica sol system that can be solidified by freezing. This parameter change in the solidification mechanism simplifies the process and improves demoldability while maintaining core strength, as the frozen structure can be easily removed and then thawed without chemical reactions.
Solution Approach 2:
The patent utilizes phase transition (freezing) as the solidification mechanism for the silica sol binder. By freezing the silica sol, the binder sets without requiring chemical reactions or complex drying processes. The phase change from liquid to solid provides sufficient strength, and the reversible nature of freezing facilitates easy demoldability and subsequent reuse of the core material.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The casting core maintains dimensional stability during the casting process and facilitates easy removal of the core material post-casting, while avoiding harmful emissions and allowing for reuse of the core material.
Implementation Method 1
casting core contains or consists of ceramic particles bound with a silica sol
Implementation Method 2
The casting core has a pore structure, in which the average pore size of the pores increases at least in sections from the outside to the inside in the casting core
Implementation Method 3
achieved through the freeze gelation process
Data Source
AI summary
The present invention relates to a casting core for casting molds, wherein the casting core contains or consists of ceramic particles bound with a silica sol. The casting core has a pore structure, in which the average pore size of the pores increases at least in sections from the outside to the inside in the casting core. The present invention also relates to a method for producing the casting core according to the invention and to the use of the casting core according to the invention.