Secondary Cooling Apparatus for NdFeB Magnet Strip Casting
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Solution Overview
Problem
Current cooling methods for cast thin pieces in the strip casting of neodymium-iron-boron based magnets struggle to control cooling velocity effectively, especially in the high temperature range, leading to slow cooling, oxidation issues, and safety concerns, while existing apparatuses are bulky and unreliable for mass production.
Innovation Solution
A secondary cooling apparatus with a comb tooth-shaped device and pressing mechanism, utilizing liquid cooling medium through cooling pipes, allows for precise control of cooling velocity by adjusting the time pieces are held on cooling teeth, ensuring rapid cooling to 150°C or lower, enhancing productivity and tissue control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional cooling methods (inert gas cooling, conveyer cooling, liquid Ar cooling) are used to cool cast thin pieces, then cooling can be performed, but the cooling velocity in the high temperature range becomes slow as temperature difference decreases, extending the time required to reach safe temperature and causing oxidation problems
Solution Approach 1:
The cooling process is divided into two distinct stages: primary cooling using inert gas in the high temperature range to prevent oxidation, and secondary cooling using liquid Ar in the low temperature range to rapidly reduce temperature. This segmentation allows each stage to be optimized independently, solving the contradiction between maintaining safe cooling velocity and reducing total cooling time.
Solution Approach 2:
The invention changes the cooling medium parameter from a single type (inert gas or liquid Ar) to a combination of two different media with different thermal properties. Inert gas provides gentle cooling at high temperatures, while liquid Ar provides intense cooling at low temperatures, thereby achieving both oxidation prevention and rapid cooling.
2Productivity
If the cooling apparatus uses large diameter pipes and heat exchangers to increase cooling capacity, then cooling effectiveness improves, but the apparatus becomes bulky and difficult to handle for mass production
Solution Approach 1:
The invention uses liquid Ar as a cooling medium that can be delivered through standard-sized piping and sprayed directly onto the cast pieces. This hydraulic approach replaces the need for large diameter pipes and complex heat exchangers, achieving high cooling effectiveness while maintaining compact apparatus suitable for mass production.
Solution Approach 2:
The invention exploits the phase transition of liquid Ar to rapidly absorb heat from the cast thin pieces during secondary cooling. This phase change mechanism provides intense cooling without requiring large apparatus, as the latent heat of vaporization of liquid Ar delivers enormous cooling capacity in a compact form.
3Loss of time
If cooling velocity is increased to prevent oxidation and improve productivity, then cooling time is reduced, but control over the distribution of Nd-rich phases and tissue structure becomes difficult
Solution Approach 1:
The cooling process is segmented into two stages with different velocities: primary cooling at moderate speed to control tissue formation and Nd-rich phase distribution, and secondary cooling at high speed to rapidly reduce temperature. This segmentation allows both tissue control and oxidation prevention to be achieved simultaneously.
Solution Approach 2:
The primary cooling stage performs the preliminary action of controlling tissue structure and phase distribution at appropriate cooling velocity, preparing the material for the secondary rapid cooling stage. This preliminary control ensures that even though secondary cooling is fast, the final tissue structure remains well-controlled.
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
The apparatus enables rapid cooling of cast thin pieces to prevent oxidation and control the distribution of Nd-rich phases, improving magnetic characteristics and productivity by regulating cooling velocity, thus addressing the limitations of existing methods.
Implementation Method 1
cooling pipes provided on the cooling teeth and through which a liquid cooling medium is made to flow
Data Source
AI summary
A secondary cooling apparatus capable of gradually cooling cast thin pieces and a cast apparatus that uses it are provided. A comb tooth-shaped device is arranged inside a vessel of the secondary cooling apparatus; the cast thin pieces are piled on the comb tooth-shaped device; and crushed small pieces are placed thereon. After the cast thin pieces and the crushed small pieces are gradually cooled, the cast thin pieces are crushed by a pressing device. The crushed small pieces are rapidly cooled by being in contact with a surface of a bottom wall and side faces of cooling teeth. Nd-rich phases or R-rich phases can be annealed by the gradual cooling, and after the crushed small pieces are rapidly cooled to its oxidation temperature or below, the crushed small pieces can be taken out to the air atmosphere.