Lost Foam Casting Sprue Using Porous Insert to Reduce Gas
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Solution Overview
Problem
In lost foam casting, bottom-fill gravity cast systems require a vertical sprue with thick foam, leading to undesirable gas creation and oxide films that reduce the fatigue life of metal castings, necessitating a method to minimize foam usage and optimize material properties.
Innovation Solution
A method and apparatus using a porous insert with a hollow stem and perforated tube to form a sprue, allowing resin to flow through the sand and cure, creating a bonded sand layer that minimizes foam usage and optimizes the flow path for molten metal, thereby reducing gas entrapment and oxide films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a vertical sprue with thick foam is used in bottom-fill gravity cast systems, then the sprue structure is maintained, but gas creation and oxide films increase, reducing the fatigue life of metal castings
Solution Approach 1:
The invention extracts the foam material from the sprue region, using only unbonded sand instead of foam for the sprue structure. This eliminates the source of gas generation and oxide film formation in the sprue, while maintaining the necessary sprue structure for metal flow. The foam is retained only in the pattern and runner sections where it serves its intended function.
Solution Approach 2:
The invention applies different material properties to different regions: unbonded sand is used specifically in the sprue region where gas-free flow is critical, while foam is maintained in the pattern and runner regions where pattern definition is needed. This localized material selection optimizes each region's function while minimizing overall harmful effects.
2Object-generated harmful factors
If foam is minimized in the sprue, then gas entrapment and oxide films are reduced, but the sprue structure becomes difficult to maintain
Solution Approach 1:
The invention introduces a bonding agent as an intermediary substance that acts between the unbonded sand particles in the sprue region. This bonding agent temporarily holds the sand particles together to form a stable sprue structure during the casting process, then breaks down when exposed to molten metal, allowing the sprue to function properly without foam.
Solution Approach 2:
The invention changes the bonding state of the sand particles dynamically: initially bonded to form the sprue structure, then unbonded when exposed to molten metal. This parameter change allows the sprue to maintain its structural integrity during formation and placement, then transition to a state that facilitates proper metal flow and gas release.
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 approach reduces gas entrapment and oxide films, enhancing the material properties of metal castings by minimizing foam usage and optimizing the flow path for molten metal, thus improving the fatigue life and quality of the castings.
Implementation Method 1
allowing resin to flow through the sand and cure, creating a bonded sand layer
Implementation Method 2
Molten metal is then introduced into the mold cavity to melt, pyrolyze, and displace the pattern with molten metal
Implementation Method 3
Gaseous and liquid decomposition/pyrolysis products escape through the gas-permeable, refractory skin and into the interstices between the unbonded sand particles
Implementation Method 4
In a gravity-cast lost-foam process, an overhead ladle or furnace pours metal into a pouring basin and sprue which is in communication with the casting pattern. The metallostatic head in the basin and sprue is the force driving the metal into the casting pattern
Data Source
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Figure 4
AI summary
A method and apparatus is disclosed for forming a metal casting sprue for a lost foam casting process, the sprue formed in sand for receiving molten metal and directing the molten metal to a foam pattern in a mold cavity, wherein the sprue formation is facilitated by an insert having a plurality of apertures formed therein, the apertures facilitating an application of a coating to sand surrounding the insert prior to removal of the insert from the sand, and wherein the sprue facilitates a minimization of production costs and an optimization of material properties of the resultant casting.