Grain-Oriented Electrical Steel Strip Manufacturing Process
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Solution Overview
Problem
The production of grain-oriented electrical steel strips faces challenges in achieving homogeneous grain distribution and sharp crystallographic texture due to refractory grains from thin cast slabs, which leads to high production costs and undesirable magnetic properties, especially when using traditional high-temperature slab reheating and complex processing routes.
Innovation Solution
A process involving continuous casting of silicon-alloyed steel into slabs of 50-100 mm thickness, followed by rapid solidification, hot rolling with specific temperature and deformation control, and subsequent annealing to achieve a chemical composition that includes optimal levels of Si, C, N, Mn, S, Se, Cu, and other elements to promote recrystallization and inhibit grain growth, ensuring excellent magnetic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional high-temperature slab reheating treatment is used to dissolve elements for re-precipitation, then grain growth inhibitors can be controlled in size, but production cost increases and environmental impact worsens
Solution Approach 1:
The patent applies preliminary action by controlling the precipitation of grain growth inhibitors (AlN, Al2O3, TiN) during the continuous casting process itself, rather than waiting for later reheating treatment. The slow cooling rate (1-10°C/min) during casting allows these inhibitors to precipitate in the desired size range (0.1-10 μm) before rolling, eliminating the need for subsequent high-temperature dissolution and re-precipitation cycles.
Solution Approach 2:
The patent changes the temperature parameter profile during processing. Instead of using high-temperature reheating (above 1000°C) followed by rapid cooling, the method employs controlled slow cooling (1-10°C/min) during casting to achieve the desired precipitate size distribution. This parameter change eliminates the energy-intensive reheating step while maintaining or improving inhibitor size control.
2Productivity
If thin cast slabs are used to enable in-line processing and temperature control, then productivity improves, but segregation phenomena occur leading to inhomogeneous chemical composition
Solution Approach 1:
The patent applies periodic action through controlled cooling cycles during casting. By implementing a slow, steady cooling rate (1-10°C/min) throughout the casting process, the method creates consistent thermal conditions that prevent segregation. This periodic thermal action ensures uniform precipitation of grain growth inhibitors and homogeneous chemical composition throughout the slab, even with thin cross-sections enabling in-line processing.
3Stability of the object's composition
If rapid solidification is used to prevent segregation, then chemical composition homogeneity improves, but grain growth inhibitor precipitation is insufficient
Solution Approach 1:
The patent uses preliminary action by allowing sufficient time during the casting process for grain growth inhibitors to precipitate. The slow cooling rate (1-10°C/min) provides an extended time window (compared to rapid solidification) for AlN, Al2O3, and TiN particles to nucleate and grow to the desired size range (0.1-10 μm) before the slab enters the rolling mill, while still maintaining compositional homogeneity.
4Reliability
If complex processing routes with multiple reheating steps are used, then magnetic properties can be optimized, but process complexity and production cost increase
Solution Approach 1:
The patent merges multiple processing functions into the continuous casting step itself. By controlling cooling rate and composition, the casting process simultaneously achieves: (1) homogeneous chemical composition, (2) proper grain growth inhibitor precipitation, (3) appropriate initial microstructure, and (4) readiness for subsequent rolling. This consolidation eliminates multiple separate reheating and heat treatment steps, reducing process complexity while maintaining magnetic property optimization.
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 results in grain-oriented electrical steel strips with improved magnetic permeability and reduced core losses, achieving peak induction levels of over 1.80 Tesla, while simplifying the production process and reducing costs by avoiding high-temperature reheating and segregation issues.
Implementation Method 1
rapid solidification, hot rolling with specific temperature and deformation control
Implementation Method 2
obtaining a very homogeneous distribution of recrystallised grains and second phases particles in the metallic matrix
Data Source
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AI summary
The invention related to a process to manufacture grain-oriented electrical steel (GOES) strip is provided wherein a molten silicon-alloyed steel is continuously cast in a strand having a thickness in the range of from 50 to 100 mm and subjected to hot- rolling in a plurality of uni-directional rolling stands to produce final hot-rolled strip coils having a thickness in the range of from 0.7 to 4.0 mm followed by a continuous annealing the hot-rolled strip, cold rolling, continuous annealing the cold-rolled strip to induce primary recrystallisation and, optionally, decarburization and/or nitriding, coating the annealed strip, annealing the coiled strip to induce secondary recrystallisation, continuous thermal flattening annealing of the annealed strip and coating the annealed strip for electric insulation and the product produced thereby.