Controlled Nozzle Cooling for Progressive Solidification
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Solution Overview
Problem
Conventional casting processes face challenges such as turbulent mold filling, air gap formation, and slow cooling rates, leading to defects and poor mechanical properties, especially in sand molds, while ablation casting technologies are limited by solvent usage and mold compatibility issues.
Innovation Solution
A controlled nozzle cooling (CNC) casting process using arrays of nozzles embedded in molds to deliver coolant at predetermined rates and durations, eliminating air gaps and achieving progressive solidification from the distal end of the casting towards the riser or downsprue, allowing for rapid and uniform cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If metal molds are used for high pressure die casting, then cooling rates are high and microstructure is fine, but turbulent flow causes defects and severe erosion to the mold
Solution Approach 1:
The mold is segmented into two functional parts: a permanent metal mold structure for mechanical support and a removable sand liner for smooth mold filling. This segmentation allows each part to perform its optimal function without the drawbacks of using either material alone for both purposes.
Solution Approach 2:
A disposable sand liner is used inside the permanent metal mold. The sand liner is removed after each casting, allowing the expensive metal mold to be reused indefinitely. This eliminates the need for the metal mold to withstand turbulent flow erosion while maintaining smooth filling capabilities.
2Ease of operation
If sand molds are used for casting, then mold filling is smooth, but cooling rates are low resulting in coarse microstructure
Solution Approach 1:
The invention merges the advantages of sand molds (smooth filling) and metal molds (high cooling rate) by combining a sand liner with a permanent metal mold structure. The sand liner provides smooth filling while the metal mold structure provides high thermal conductivity for rapid cooling.
Solution Approach 2:
The mold system uses a composite structure combining sand (for smooth filling) and metal (for high thermal conductivity). This composite approach allows the system to achieve both smooth mold filling and rapid cooling rates simultaneously.
3Temperature
If ablation casting with soluble binder is used, then rapid cooling is achieved, but mold making cycle is extended and mold compatibility is limited
Solution Approach 1:
A disposable sand liner is used that can be quickly removed after each casting, eliminating the need for complex soluble binder chemistry. This simple disposable component achieves rapid cooling without extending the mold making cycle or requiring specialized binder materials.
Solution Approach 2:
The cooling function is extracted from the mold structure itself and transferred to a separate removable sand liner. This allows the permanent metal mold to be reused without modification while the sand liner provides the necessary rapid cooling capability through its removal and replacement.
4Temperature
If coolant is delivered early with full impacting force, then cooling is rapid, but leakage and surface damage occur
Solution Approach 1:
A solid skin is formed on the casting surface before coolant delivery begins. This preliminary solidification layer acts as a protective barrier that prevents coolant impact from causing surface damage or leakage, while still allowing rapid cooling to proceed.
Solution Approach 2:
The solid skin formed on the casting surface serves as a cushioning layer before the coolant is applied. This protective layer absorbs the impact of the coolant flow, preventing direct damage to the casting surface while maintaining effective cooling.
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 process reduces cooling time, increases casting productivity, improves mechanical properties, and enables the use of conventional binders and semi-permanent molds, while being retrofittable to existing production lines, capable of producing high-quality thin-walled and large castings.
Implementation Method 1
delivering a predetermined amount of coolant through each nozzle at predetermined rates, times, and durations to break the layer of sand or coating separating the nozzle to the casting and to cool the external surface of the casting
Implementation Method 2
achieve an acceptable level of progressive solidification from the distal end of the casting towards the riser or downsprue
Data Source
AI summary
A process for permanent mold casting of metals and their alloys includes the steps of providing at least a mold equipped with a plurality of cooling nozzles, making a layer of coolant permeable materials covering the nozzles and maintaining the materials at desired temperatures, delivering a molten metal into the mold, supplying predetermined amount of coolant to each nozzles to contact the external surface of the casting at desired rate, time, and duration to achieve an acceptable level of progressive solidification from the distal end of the casting towards the riser until the casting has reached desired temperatures.