Grain-Oriented Electrical Steel Rapid Heating Annealing
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Solution Overview
Problem
Conventional methods for producing grain-oriented electrical steel sheets result in high iron loss deviations due to temperature variations during heating, which are not effectively addressed by rapid heating techniques, leading to suboptimal magnetic properties.
Innovation Solution
A method involving rapid heating during decarburization annealing with a holding time of 1-10 seconds at 250-600°C, achieving uniform temperature distribution and reducing the development of //ND orientation, thereby promoting Goss orientation and refining recrystallized grains, resulting in lower iron loss and reduced deviation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If rapid heating is performed at high heating rates (≥100°C/s) during decarburization annealing, then the primary recrystallized texture is improved and Goss orientation is promoted, but temperature variation inside the steel sheet increases leading to high iron loss deviation
Solution Approach 1:
The heating process is divided into distinct stages: an initial rapid heating phase (≥100°C/s) to promote Goss orientation, followed by a holding phase at 550-650°C to equalize temperature, and then continued heating to the target temperature. This periodic action allows the system to benefit from both rapid heating effects and temperature uniformity.
Solution Approach 2:
The heating rate parameter is dynamically adjusted during the process. It starts at a high rate (≥100°C/s) to achieve texture improvement, then is reduced during the holding phase (550-650°C) to allow temperature equalization, and finally increased again to reach the decarburization annealing temperature. This parameter change resolves the contradiction between rapid heating benefits and temperature uniformity.
2Reliability
If the steel sheet is held at high temperature (775-840°C) for extended periods to refine secondary recrystallized grains, then magnetic properties improve, but production time and energy consumption increase
Solution Approach 1:
The initial rapid heating phase (≥100°C/s) and the intermediate holding phase (550-650°C) are performed as preliminary actions to pre-equalize the temperature distribution and promote Goss orientation before the final high-temperature holding. This preliminary action reduces the time required for the final recrystallization holding, as the temperature uniformity is already established.
3Loss of energy
If conventional heating rates are used during decarburization annealing, then energy consumption is lower, but γ-fiber ({111}//ND orientation) develops preferentially reducing magnetic properties
Solution Approach 1:
The critical temperature range where γ-fiber forms preferentially is rapidly traversed by applying high heating rates (≥100°C/s). This 'skipping' through the problematic temperature zone prevents the unwanted γ-fiber orientation from developing, while the overall energy consumption is managed by using holding phases at lower temperatures (550-650°C) to maintain uniformity.
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 method produces grain-oriented electrical steel sheets with lower iron loss and smaller deviation in iron loss values, enhancing magnetic properties and achieving uniform heating across the steel sheet width.
Implementation Method 1
rapid heating in decarburization annealing or rapid heating just before decarburization annealing
Implementation Method 2
decarburization annealing
Implementation Method 3
keeping the steel sheet at a temperature of 775∼840°C lower than the temperature of the rapid heating
Implementation Method 4
the temperature inside the steel sheet is uniformized to provide the effect of the rapid heating over the full width of the steel sheet
Implementation Method 5
grain orientations are highly accumulated into {110} orientation called as Goss orientation
Implementation Method 6
primary recrystallized texture
Data Source
AI summary
In a method for producing a grain-oriented electrical steel sheet by comprising a series of steps of hot rolling a raw steel material containing C: 0.002~0.10 mass%, Si: 2.0~8.0 mass% and Mn: 0.005~1.0 mass% to obtain a hot rolled sheet, subjecting the hot rolled steel sheet after or without hot band annealing to one stage cold rolling or two or more stage cold rollings including an intermediate annealing therebetween to obtain a cold rolled sheet having a final sheet thickness, subjecting the cold rolled sheet to decarburization annealing combined with primary recrystallization annealing, applying an annealing separator to the steel sheet surface and then subjecting to a final annealing, when rapid heating is performed at a rate of not less than 50°C/s in a range of 200~700°C of the decarburization annealing, the cold rolled sheet is subjected to holding at any temperature of 250~600°C for 1~10 seconds thereof to thereby produce a grain-oriented electrical steel sheet being low in the iron loss and small in the deviation of the iron loss value.