Amorphous Metal Strip Casting to Limit Surface Crystallization
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Solution Overview
Problem
The production of amorphous and nanocrystalline metal strips faces challenges in achieving consistent mechanical and magnetic properties due to surface crystallization, which affects ductility and reliability, especially during rapid solidification processes where cooling rates vary, leading to irregularities and strip tears.
Innovation Solution
A method involving rapid solidification technology where the molten mass is solidified on a casting wheel with a controlled cooling rate and surface reshaping to limit surface crystallization to less than 23% on both sides, ensuring a microstructure of at least 80% amorphous or nanocrystalline grains with random orientation, and heat treatment to maintain properties over long lengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If rapid solidification technology is used to produce amorphous metal strips, then good soft magnetic properties and attractive mechanical properties are achieved, but surface crystallisation occurs which affects ductility and reliability
Solution Approach 1:
The patent applies parameter changes by precisely controlling the cooling rate during solidification (10^5 to 10^7 K/s) and adjusting the composition of glass-forming elements (10-30 at.%) to prevent surface crystallisation while maintaining the amorphous microstructure. This resolves the contradiction by optimizing process parameters to achieve reliable properties without harmful surface crystallisation.
Solution Approach 2:
The patent applies local quality by ensuring that the surface layer of the metal strip maintains an amorphous microstructure without crystallisation, while the bulk material can have controlled nanocrystalline phases through heat treatment. This local control of microstructure quality prevents surface crystallisation from affecting overall reliability.
2Productivity
If longer strip lengths are produced to improve cost-effectiveness, then production efficiency increases, but the risk of strip tears and property irregularities due to surface crystallisation increases
Solution Approach 1:
The patent applies continuity of useful action by implementing continuous casting processes that maintain consistent cooling rates and protective atmospheres throughout the entire production run. This continuous control prevents intermittent surface crystallisation that would cause strip tears, enabling reliable production of very long continuous strips.
Solution Approach 2:
The patent applies preliminary action by pre-heating the casting wheel and establishing stable thermal conditions before initiating the casting process. This preliminary preparation ensures that the first portions of the strip are produced under optimal conditions, preventing early surface crystallisation that could compromise overall strip integrity.
3Adaptability or versatility
If cooling rate varies during solidification, then production flexibility is maintained, but surface crystallisation occurs leading to property irregularities
Solution Approach 1:
The patent applies feedback by implementing monitoring systems that track cooling rates and thermal conditions during casting. When deviations are detected that could lead to surface crystallisation, the system automatically adjusts process parameters to maintain microstructure uniformity, thereby preserving both production flexibility and manufacturing precision.
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 metal strips with improved ductility and uniform mechanical and magnetic properties, allowing for longer continuous lengths without tears, enhancing the reliability and cost-effectiveness of the manufacturing process.
Implementation Method 1
a molten mass is solidified on the outer surface of a casting wheel
Implementation Method 2
solidified on the outer surface of a heat sink, i.e. a casting wheel
Implementation Method 3
The nanocrystalline grains are typically formed by annealing the amorphous metal strip
Data Source
AI summary
A metal strip is provided having a casting-wheel side that has been solidified on an outer surface of a heat sink, an opposing, air side and a microstructure. The microstructure is at least 80 vol. % amorphous or has at least 80 vol. % nanocrystalline grains and a residual amorphous matrix in which at least 80% of the nanocrystalline grains have an average grain size of less than 50 nm and a random orientation. The air side of the metal strip has a surface crystallisation proportion of less than 23%.