Spiral-Cast Single Crystal Sheets Beyond Furnace Size Limits
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Solution Overview
Problem
The existing methods for producing large sheets of nickel base superalloy single crystal are limited by furnace size and face challenges in maintaining thermal gradients during the directional solidification process, particularly when withdrawing the bottom chill plate beyond a certain height.
Innovation Solution
A method involving a spiral metallic workpiece with a cast single crystal structure, where a spiral cut is made and the workpiece is partially flattened, allowing for the creation of a sheet with progressively varying crystallographic orientation, which can be secured to form a full hoop or tubular structure, enabling the production of large single crystal sheets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If directional solidification of an investment cast mold is used to produce large sheets of nickel base superalloy single crystal, then single crystal structure is achieved, but the process is limited by furnace size and difficulty in maintaining thermal gradient as the bottom chill plate is withdrawn beyond a certain height
Solution Approach 1:
The patent divides the single crystal sheet production into two stages: first producing a cylindrical single crystal ingot through directional solidification, then making spiral cuts and flattening to create the final sheet product. This segmentation allows the challenging single crystal formation to occur in a controlled cylindrical geometry within existing furnace size limits, while the subsequent mechanical processing achieves the desired large sheet dimensions without requiring proportionally larger furnaces.
Solution Approach 2:
The patent transforms the problem from a two-dimensional sheet production challenge into a three-dimensional cylindrical ingot production followed by geometric transformation. By casting a cylinder and then applying spiral cuts at specific angles followed by flattening, the process achieves large sheet dimensions through dimensional transformation rather than direct planar solidification, bypassing the furnace size and thermal gradient maintenance limitations.
2Area of stationary object
If the bottom chill plate is withdrawn to increase sheet size, then larger single crystal sheets are produced, but maintaining thermal gradient becomes increasingly difficult
Solution Approach 1:
The patent separates the thermal processing stage (directional solidification of cylindrical ingot) from the dimensional expansion stage (spiral cutting and flattening). The thermal gradient is maintained only during the ingot formation phase in a controlled, compact geometry where furnace capabilities are sufficient. The subsequent sheet expansion to larger dimensions occurs through mechanical processing at lower temperatures, eliminating the need to maintain thermal gradients across large vertical distances.
Solution Approach 2:
The patent achieves large sheet area not through vertical extension that would require maintaining thermal gradients over large height differences, but through horizontal expansion via spiral unrolling and flattening of a compact cylindrical ingot. This dimensional transformation allows large area production while keeping the thermal processing zone compact and thermally controllable.
3Productivity
If conventional casting methods are used, then production capability is maintained, but investment costs increase due to requirements for liquid metal cooling and larger furnace infrastructure
Solution Approach 1:
The patent divides the production process into a high-precision thermal stage (cylindrical ingot casting with controlled directional solidification) and a low-cost mechanical stage (spiral cutting and flattening). This allows the expensive, complex furnace infrastructure to be used only for the essential single crystal formation in a compact geometry, while the subsequent sheet production uses simpler, lower-cost mechanical processing equipment.
Solution Approach 2:
The patent produces large sheet dimensions through geometric transformation of a compact cylindrical ingot rather than direct large-scale planar casting. This approach allows standard-sized furnaces to produce single crystal material, with the final large sheet dimensions achieved through spiral cutting and flattening operations that require minimal specialized infrastructure.
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 allows for the production of large single crystal sheets with varying Young's modulus and crystallographic properties, enhancing structural applications and potentially reducing costs by using nickel-based superalloys, while maintaining thermal gradient control.
Implementation Method 1
directional solidification of an investment cast mold
Implementation Method 2
single crystal technology to manufacture of industrial gas turbine blades
Implementation Method 3
at least partially flattening the workpiece
Data Source
AI summary
A method comprises: providing a spiral metallic workpiece having a cast structure associated with such spiral; and at least partially flattening the workpiece.