Layered Susceptor Design for Magnetic Flux Shielding
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Solution Overview
Problem
The directional solidification process in single crystal gas turbine part casting is hindered by magnetic field leakage from the susceptor, leading to defects such as separated nucleated grains, freckles, porosity, and mis-oriented boundaries, due to the impractical thickness required to fully attenuate the electromagnetic field in monolithic graphite susceptors.
Innovation Solution
A layered susceptor system with constant thickness layers, comprising different electromagnetic shield materials, is used to attenuate the primary induction coil's electromagnetic field, reducing magnetic flux leakage and controlling the magnetic stirring within the molten material, thereby enhancing the formation of desired microstructures in cast parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a monolithic graphite susceptor with increased thickness is used to attenuate the electromagnetic field, then the magnetic field shielding effectiveness is improved, but the device complexity and manufacturing difficulty increase significantly
Solution Approach 1:
The susceptor is divided into multiple discrete layers (first layer, second layer, and interior layer) rather than using a single monolithic structure. Each layer can be independently manufactured and positioned, allowing the system to achieve the required magnetic field attenuation through cumulative shielding effect of multiple thin layers instead of requiring an excessively thick single layer.
Solution Approach 2:
The invention employs composite susceptor construction using multiple layers of electromagnetic shield materials that can be selected for different attenuation properties. This allows optimization of magnetic field shielding effectiveness while maintaining practical thickness requirements and manufacturing feasibility.
2Object-affected harmful factors
If a thicker susceptor is used to fully attenuate the electromagnetic field, then the magnetic flux leakage is reduced, but the heat transmission efficiency to the mold deteriorates
Solution Approach 1:
By segmenting the susceptor into multiple thin layers rather than using a single thick layer, the system achieves adequate magnetic field attenuation while minimizing the total thickness. This preserves heat transmission efficiency from the induction coil through the susceptor to the mold, as thinner susceptor material allows better thermal coupling.
Solution Approach 2:
Different layers of the susceptor can be designed with different material properties optimized for their specific functions: some layers prioritize electromagnetic shielding while others prioritize thermal conduction. This local optimization allows simultaneous achievement of magnetic field attenuation and heat transmission efficiency.
3Object-affected harmful factors
If multiple layers of electromagnetic shield material are used to attenuate the electromagnetic field, then the magnetic flux leakage is reduced, but the device complexity increases
Solution Approach 1:
The susceptor is divided into multiple discrete layers (first layer, second layer, and interior layer) rather than using a single monolithic structure. Each layer can be independently manufactured and positioned, allowing the system to achieve the required magnetic field attenuation through cumulative shielding effect of multiple thin layers instead of requiring an excessively thick single layer.
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 layered susceptor system effectively reduces grain defects in single crystal castings by minimizing magnetic stirring and maintaining the desired microstructure orientation, improving the yield and quality of cast parts.
Implementation Method 1
A susceptor is utilized to transduce an electromagnetic field produced by the electric coil into radiant heat transferred to the casting mold
Implementation Method 2
The susceptor is heated by induction coils and radiates heat toward the mold to maintain metal in a molten state
Implementation Method 3
The susceptor therefore fulfills two roles: it transduces the electromagnetic field from the primary induction coil into heat, and simultaneously attenuates said field
Data Source
Figure 1
AI summary
An induction furnace assembly (10) comprising a chamber (12) having a mold (16); a primary inductive coil (20) coupled to the chamber (12); a layered susceptor (26) comprising at least two layers (40) of magnetic field attenuating material (44) surrounding the chamber (12) between the primary inductive coil (20) and the mold (16) to nullify the electromagnetic field (28) in the hot zone of the furnace chamber (12).