Direct Chill Casting Spout for Shrinkage Cavity Elimination
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Solution Overview
Problem
Direct chill casting of metal ingots, particularly aluminum and aluminum-based alloys, results in shrinkage cavities that are difficult to eliminate efficiently, leading to defects like 'alligatoring' and the need for costly metal removal or recycling.
Innovation Solution
A method involving the controlled filling of partial shrinkage cavities with molten metal during and after casting, using a spout that maintains heat to prevent solidification, allowing the cavity to form and then fill repeatedly until no further contraction occurs, ensuring the ingot maintains a predetermined height without significant spillage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a reservoir of molten metal is retained above the nominal upper surface to compensate for shrinkage, then shrinkage cavities can be filled, but excess metal must be removed from the upper part of the ingot after solidification
Solution Approach 1:
The spout is made movable relative to the mold, allowing it to be dynamically repositioned from a delivery position during casting to a central position below the upper surface after casting. This dynamic adjustment enables the spout to automatically fill shrinkage cavities as they form without requiring excess metal removal.
Solution Approach 2:
The system uses the ingot's own shrinkage process to drive the cavity filling. As the ingot shrinks and forms cavities during cooling, the spout automatically delivers molten metal to fill these cavities, eliminating the need for external intervention or excess metal removal.
2Extent of automation
If the spout is positioned centrally below the upper surface after casting, then shrinkage cavities can be filled automatically, but precise control of metal flow is required to avoid spillage
Solution Approach 1:
A level detector continuously monitors the position of the molten metal meniscus in the spout and provides feedback to the control system. This feedback enables precise control of the spout's metal delivery, automatically adjusting flow to fill cavities without spillage.
Solution Approach 2:
The manual or mechanical control of metal flow is replaced with an automated control system that uses level detection and controlled delivery mechanisms to precisely regulate molten metal flow into the spout and from the spout to the ingot.
3Temperature
If molten metal is continuously supplied to the spout after casting, then the spout remains molten for cavity filling, but the metal may solidify in the channels and spouts
Solution Approach 1:
Insulation is applied to the spout and channels before the cavity filling process begins, preventing heat loss and metal solidification. This preliminary thermal protection ensures the spout remains molten and ready for automatic cavity filling.
Solution Approach 2:
The thermal parameters of the spout system are modified by adding insulation, which changes the heat transfer characteristics and maintains the metal in liquid state during the cavity filling operation.
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 effectively eliminates or reduces shrinkage cavities, minimizing metal loss and preventing defects like 'alligatoring', allowing for a more efficient casting process with less material waste and improved ingot quality.
Implementation Method 1
supplying the spout to keep the metal molten for subsequent delivery through the spout
Implementation Method 2
A partial shrinkage cavity is allowed to form in the upper surface of the ingot as metal of the ingot shrinks and contracts
Data Source
Figure 1
Figure 2A~2H
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AI summary
An exemplary embodiment provides a method of fully or partially eliminating a shrinkage cavity in a metal ingot cast by direct chill casting. The method involves casting a metal ingot by introducing molten metal into a direct chill casting mold from a spout to form an upright ingot having an upper surface at a predetermined height. Upon completion of the casting, the lower tip of the spout is preferably maintained below the upper surface in molten metal at or near a center of the upper surface of the ingot. The metal flow through the spout is terminated while maintaining sufficient heat in metal within and supplying the spout to keep the metal molten for subsequent delivery through the spout. A partial shrinkage cavity is allowed to form in the upper surface of the ingot as metal of the ingot shrinks and contracts. Preferably before the partial cavity exposes the lower tip of the spout, the partial shrinkage cavity is preferably over‐filled with molten metal, while all or significant spillage of molten metal from the partial cavity is avoided, and then the flow of metal through the spout is terminated. The steps of allowing a partial shrinkage cavity to form in the upper surface and then preferably over‐filling the partial shrinkage cavity with molten metal from the spout before the cavity exposes the lower tip is repeated, preferably until no further contraction of the metal of the ingot causes any part of the upper surface to contract below the predetermined height. The spout is then removed from contact with molten metal of the ingot and all parts of the ingot are allowed to cool to a temperature at which the metal is fully solid.