Oriented Electrical Steel Sheet Annealing Process
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The conventional high-temperature annealing process for oriented electrical steel sheets is energy-intensive, causes temperature deviations within coils leading to magnetism deviations, and results in reduced yield due to surface defects and a multi-step production process.
Innovation Solution
A method involving reheating a slab with specific compositions, hot-rolling, decarburization-annealing, and continuous final annealing in a mixed gas atmosphere to reduce grain size and magnetic domain size, eliminating batch-type annealing and nitriding, thereby improving magnetic properties and reducing iron loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If batch-type annealing in coiled state is used, then production process is simplified, but temperature deviation and magnetism deviation occur between external and internal winding portions
Solution Approach 1:
The patent segments the annealing process into two distinct stages: (1) batch-type annealing in coiled state for initial treatment, and (2) subsequent annealing of unwound steel sheets for final precision control. This segmentation allows the first stage to handle bulk processing while the second stage addresses uniformity issues, thereby resolving the contradiction between process simplicity and magnetism uniformity.
Solution Approach 2:
The patent performs preliminary annealing in the coiled state before unwinding and subsequent processing. This preliminary action prepares the material for further treatment while allowing later stages to correct any deviations, thus maintaining both process efficiency and final product quality.
2Device complexity
If conventional batch-type annealing is used, then processing is simpler, but MgO coating and surface defects reduce actual yield
Solution Approach 1:
The patent separates the annealing operation from the coating operation. By annealing unwound steel sheets rather than keeping them in coiled form with MgO coating, the process eliminates surface defects caused by coating interference, thereby improving actual yield while maintaining reasonable process complexity.
Solution Approach 2:
The patent converts the potential harm of removing MgO coating during annealing into a benefit by deliberately annealing unwound sheets without coating interference. This approach transforms what could be a damaging process (coating removal) into a quality-improving step that eliminates surface defects and increases yield.
3Ease of operation
If decarburization-annealed plate is wound in coil form, then handling is easier, but additional flattening annealing and insulating coating steps are required
Solution Approach 1:
The patent inverts the conventional sequence by annealing unwound steel sheets instead of annealing coiled sheets. This reversal eliminates the need for subsequent flattening annealing and insulating coating steps, as the steel sheets are processed in their unwound state, thereby reducing overall process complexity while maintaining ease of handling through continuous processing.
4Manufacturing precision
If high-temperature annealing with slow temperature raising rate is used, then Goss orientation integration and magnetism are improved, but energy consumption increases and processing time extends
Solution Approach 1:
The patent performs preliminary decarburization annealing before the final high-temperature annealing for Goss orientation development. This preliminary action removes carbon that would otherwise interfere with recrystallization, allowing the subsequent annealing to achieve better Goss orientation integration more efficiently, thereby reducing overall energy consumption and processing time.
Solution Approach 2:
The patent optimizes the temperature raising rate and holding time parameters for the final annealing process. By carefully controlling these parameters after preliminary decarburization, the process achieves high Goss orientation integration with reduced energy input compared to conventional slow-heating methods applied to carbon-containing steel.
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 reduces energy consumption, minimizes magnetism deviations, and enhances yield by achieving a high volumetric fraction of Goss orientation grains with small magnetic domains, significantly lowering iron loss and improving magnetic flux density.
Implementation Method 1
allowing the same to undergo high-temperature annealing for primary recrystallization annealing and secondary recrystallization formation
Implementation Method 2
high-temperature annealing for primary recrystallization annealing and secondary recrystallization formation
Implementation Method 3
decarburization-annealing the cold-rolled steel sheet
Data Source
AI summary
A method for manufacturing an oriented electrical steel sheet according to an exemplary embodiment of the present invention includes: providing a slab including, as wt %, Si at equal to or less than 4.0% (excluding 0%), C at 0.001% to 0.4%, and Mn at 0.001% to 2.0%, and including a balance including Fe and inevitably mixed and input impurities; reheating the slab; manufacturing a hot steel sheet by hot-rolling the slab; performing hot-rolled steel sheet annealing to the hot steel sheet; primarily cold-rolling the hot-rolled steel sheet annealed hot steel sheet; decarburization-annealing the cold-rolled steel sheet; secondarily cold-rolling the decarburization-annealed steel sheet;and finally annealing the cold-rolled steel sheet, wherein, regarding the finally annealed steel sheet, a size 2L of a magnetic domain existing in a grain is less than a thickness D of the steel sheet (2L<D).