Cast Component Corner Radius to Prevent Recrystallization
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Solution Overview
Problem
High residual stresses in cast components made using refractory metal cores during investment casting can lead to recrystallization, which affects mechanical properties and requires costly heat treatment to alleviate, but this can alter other properties and is not entirely effective.
Innovation Solution
Designing internal corners with a corner radius greater than a critical value to manage internal residual stresses, eliminating the need for subsequent heat treatment by ensuring the corner radius is sufficient to prevent recrystallization without impacting other properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If refractory metal cores are used to form internal passages in cast components, then complex internal geometries can be achieved, but high residual stresses are generated that cause recrystallization and require costly heat treatment
Solution Approach 1:
The invention changes the geometric parameter of the core, specifically increasing the corner radius beyond a critical value. This parameter change reduces stress concentration at internal corners during casting, preventing recrystallization and eliminating the need for heat treatment while maintaining the ability to form complex internal passages
Solution Approach 2:
The invention applies preliminary action by designing the core with an enlarged corner radius before the casting process. This pre-design feature prevents the generation of harmful residual stresses during casting, thereby preventing recrystallization and eliminating the need for subsequent heat treatment operations
2Strength
If heat treatment is applied to relieve residual stresses, then recrystallization is reduced, but other material properties are altered and costs increase
Solution Approach 1:
The invention converts the potentially harmful sharp corner geometry into a beneficial feature by enlarging the corner radius. This design modification prevents stress concentration and recrystallization from occurring in the first place, thereby eliminating the need for heat treatment and avoiding the associated costs and property alterations
Solution Approach 2:
The invention performs the stress prevention action preliminarily by designing the core with an enlarged corner radius before casting. This prevents recrystallization and residual stress formation during the casting process itself, eliminating the need for subsequent heat treatment operations and reducing manufacturing complexity
3Ease of manufacture
If sharp internal corners are used in the core design, then manufacturing simplicity is maintained, but recrystallization occurs due to high residual stresses
Solution Approach 1:
The invention changes the geometric parameter of the core corner from sharp to enlarged radius. This parameter modification reduces stress concentration during casting, preventing recrystallization and maintaining microstructure stability while still being manufacturable using standard core-making processes
Data Source
Figure 1~3
AI summary
A cast component includes a cast body that has a single crystal microstructure and an internal corner bounding an internal cavity. The single crystal microstructure defines a critical internal residual stress with respect to investment casting of the cast body using a refractory metal core beyond which the single crystal microstructure recrystallizes under a predetermined condition. The internal corner has a corner radius that is greater than a critical corner radius below which an amount of internal residual stress in the single crystal microstructure exceeds the critical internal residual stress. The internal cavity includes a cross section less than about 20 mils near the corner radius.