Nucleated Casting Apparatus for Large Diameter Preform Segregation Control
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Solution Overview
Problem
Current methods for refining and casting large diameter metal and metal alloy preforms prone to segregation, such as nickel-based superalloys and titanium alloys, face challenges like segregation, melt-related defects, high yield losses, and size limitations due to centrifugal forces and gas entrapment, leading to costly and inefficient processes.
Innovation Solution
A method and apparatus involving electroslag or vacuum arc remelting followed by nucleated casting, where the molten refined material is transferred through a cold induction guide to protect it from contamination and oxidation, and then atomized into a droplet spray for deposition within a mold, allowing for the formation of large diameter preforms with minimal segregation and defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If VAR melting is used to produce large diameter ingots, then the ingot size can be increased, but segregation and macro-scale defects increase
Solution Approach 1:
The invention extracts the harmful centrifugal forces and gas entrapment mechanisms from the casting process by using a static mold configuration and controlled melt delivery, eliminating the root causes of segregation and defects while maintaining large diameter capability
Solution Approach 2:
A flux layer is introduced as an intermediary between the molten metal and the mold cavity, serving to control melt flow, reduce oxidation, and minimize turbulence that would cause segregation, thereby enabling large diameter casting with improved metallurgical quality
2Productivity
If spray forming is used to produce preforms, then production speed can be increased, but yield losses increase due to overspray and gas entrapment
Solution Approach 1:
The invention converts the typically harmful rapid solidification and gas entrapment effects in spray forming into benefits by using a controlled atmosphere and modified droplet deposition process, where the gas that would normally cause porosity is managed to actually protect the melt and improve quality while maintaining high productivity
Solution Approach 2:
The invention changes key process parameters including droplet size distribution, deposition temperature, and atmosphere composition to optimize the balance between production speed and yield, reducing overspray losses and gas entrapment while maintaining rapid solidification benefits
3Manufacturing precision
If triple melt technique is used for segregation-prone materials, then metallurgical quality can be improved, but processing time and costs increase
Solution Approach 1:
The invention merges multiple refining functions into a single integrated casting process, combining the benefits of vacuum processing, flux refinement, and controlled solidification that were previously achieved through separate triple melt steps, thereby reducing cycle time while maintaining metallurgical quality
Solution Approach 2:
The invention performs preliminary refinement actions during the casting process itself rather than requiring separate pre-processing steps, using flux layers and controlled atmosphere to prepare the melt in advance, eliminating the need for multiple sequential melting operations
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 enables the production of large diameter preforms with minimal segregation and melt-related defects, reducing yield losses and processing costs, and achieving a fine-grained microstructure, while avoiding the limitations of conventional casting methods.
Implementation Method 1
at least a portion of the molten refined material passes through a passage that is protected from contamination by contact with oxygen in the ambient air. The passage preferably is constructed of a material that will not react with the molten refined material
Implementation Method 2
Spray forming is essentially a 'moldless' process using gas atomization to create a spray of droplets of liquid metal from a stream of molten metal
Implementation Method 3
The process parameters of the spray forming technique are adjusted such that the average fraction of solid within the atomized droplets at the instant of impact with a collector surface is sufficiently high to yield a high viscosity deposit
Data Source
AI summary
An apparatus for casting metals by a nucleated casting technique to create a preform, the apparatus including a mold having a base and a side wall where the base can be moved relative to the side wall to withdraw the preform as it is being created. In various circumstances, portions of a droplet spray created by an atomizing nozzle, i.e., overspray, may accumulate on a top surface of the side wall and prevent or inhibit the preform from being moved relative to the side wall. The atomizing nozzle can be oriented such that the droplet spray passes over the top of the side wall to remelt and remove at least a portion of the overspray that has accumulated thereon. The mold can be rotated such that the overspray formed on a region of or on the entire perimeter of the top surface can pass through the droplet spray and can be removed from the side wall.