Foamed Sand Mold Hardened Layer Design for Casting Integrity
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Solution Overview
Problem
In the process of molding products with hollow portions using foamed sand, the vulnerable or hollow portions formed during the hardening process can expose internal cavities, allowing molten metal to flow into these areas, compromising the integrity of the casting.
Innovation Solution
The molding method and die configuration ensure a hardened layer is formed in a predetermined thickness range from the outer layer, with the vulnerable or hollow portion's thickness being one-third of the product portion, and the hardened layer's thickness also one-third, maintaining a ratio where b < d/2, preventing molten metal from entering the sand mold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If foamed sand is filled into the cavity to form a sand mold with hollow portions, then the collapsibility and ease of core removal are improved, but vulnerable portions or hollow portions are formed inside the molded product which may allow molten metal to flow in during casting
Solution Approach 1:
The patent applies local quality by creating a hardened layer with different properties from the vulnerable portion. The hardened layer has higher density and strength, while the vulnerable portion maintains lower density for collapsibility. This local differentiation allows the hardened layer to prevent molten metal intrusion while the vulnerable portion enables core removal after casting.
Solution Approach 2:
The sand mold is segmented into two distinct regions: a hardened layer and a vulnerable portion. The hardened layer acts as a protective barrier, while the vulnerable portion provides collapsibility. This segmentation resolves the contradiction by assigning different functions to different segments of the same structure.
2Reliability
If the hardened layer thickness is increased to prevent molten metal flow, then the structural integrity is improved, but the vulnerable portion thickness must also increase which affects the collapsibility and core removal
Solution Approach 1:
The patent maintains local quality by keeping the hardened layer thickness within a specific range (1/3 to 2/3 of total thickness) rather than maximizing it. This controlled thickness provides sufficient protection against molten metal while preserving enough vulnerable portion for effective collapsibility and core removal.
Solution Approach 2:
The patent optimizes the thickness parameter of the hardened layer to a specific range (1/3 to 2/3 of total thickness). This parameter change balances the conflicting requirements: sufficient thickness for protection, but not so thick as to compromise the collapsibility function of the vulnerable portion.
3Ease of manufacture
If the filling opening is made larger to facilitate foamed sand filling, then the filling process is improved, but the vulnerable portion or hollow portion of the blowing opening may expose on the product surface allowing molten metal flow
Solution Approach 1:
The patent applies local quality by ensuring the hardened layer extends to the surface in the filling opening region. This creates a protective barrier specifically where the filling opening is located, preventing molten metal from entering through the blowing opening while maintaining adequate filling access.
Solution Approach 2:
The hardened layer is formed preliminarily during the foamed sand filling and heating process before the actual casting occurs. This preliminary formation of the protective layer ensures that when molten metal is poured, the barrier is already in place to prevent intrusion through the blowing opening.
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
This configuration secures a sufficient hardened layer thickness, preventing molten metal from flowing into the sand mold from the vulnerable or hollow portions, ensuring the structural integrity of the casting.
Implementation Method 1
water glass and an aggregate are accumulated in an outer layer part of a molded product, so as to form a minute hardened layer having a necessary strength
Implementation Method 2
The die 2 is heated to around 150° C. to 300° C., so as to vaporize water in the foamed sand S filled in the cavity C, thereby solidifying the foamed sand S
Implementation Method 3
an internal pressure of the cavity C of the die 2 is increased due to evaporation of water and thermal expansion of air bubble in a heating and hardening process
Data Source
AI summary
A molding method of a sand mold including a hardened layer in a predetermined thickness range from an outer layer part, includes: forming a cavity and a filling opening of a die so that a dimension, which is a largest dimension between two intersections of straight lines passing through a section of a boundary portion between the cavity and the filling opening of the die, with respect to an outside line of the section, is less than a predetermined ratio with respect to a thickness dimension of that part of a product portion of the sand mold from which a blowing opening molded in the filling opening projects, the product portion being formed by the cavity of the die; and filling foamed sand into the cavity from the filling opening of the die.