Grain-Oriented Electrical Steel Sheet Rapid Heating Annealing
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Solution Overview
Problem
Conventional methods for producing grain-oriented electrical steel sheets face challenges in achieving uniform iron loss reduction and minimizing deviations in iron loss properties due to temperature variations and internal oxide layer defects during the heating process.
Innovation Solution
The method involves rapid heating with a rate of at least 50°C/s in the primary recrystallization annealing process, followed by holding the steel sheet at 250-600°C for 1-10 seconds and dividing the soaking process into stages to control temperature, time, and PH2O/PH2 levels, which helps in uniformizing the temperature and reducing the deviation of iron loss values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If rapid heating is performed at high heating rate to suppress γ-fiber development and promote {110} texture, then primary recrystallized texture is improved, but temperature variation inside the steel sheet increases causing deviation in iron loss property
Solution Approach 1:
The heating process is divided into multiple stages with different heating rates. The first stage uses a high heating rate (≥100°C/s) to suppress γ-fiber development, while the second stage uses a lower heating rate to reduce temperature variation inside the steel sheet, thereby achieving both texture improvement and uniformity
Solution Approach 2:
The heating rate is dynamically adjusted during the heating process. The heating rate is set to be not less than 100°C/s in the first stage and not less than 50°C/s but less than 100°C/s in the second stage, allowing the process to adapt to different temperature ranges and achieve optimal results
2Speed
If heating rate is increased to raise temperature close to recrystallization temperature quickly, then development of γ-fiber is suppressed, but defects in internal oxide layer occur
Solution Approach 1:
The heating process is segmented into two stages with different heating rates. The first stage uses high heating rate to quickly raise temperature and suppress γ-fiber, while the second stage uses moderate heating rate to complete the heating without causing oxide layer defects
Solution Approach 2:
The heating rate parameter is changed at different temperature ranges. By setting specific heating rate ranges for different stages, the process optimizes the balance between heating speed and oxide layer quality
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 results in grain-oriented electrical steel sheets with lower and more uniform iron loss properties, effectively addressing the limitations of previous techniques by stabilizing the iron loss and improving magnetic properties.
Implementation Method 1
rapid heating is performed at a rate of not less than 50°C/s in a region of 200-700°C in the heating process of the primary recrystallization annealing
Implementation Method 2
the steel sheet is held at any temperature of 250-600°C in the above region for 1-10 seconds
Implementation Method 3
soaking process of the primary recrystallization annealing is divided into N stages (N: an integer of not less than 2), and the process from the first stage to (N - 1) stage is controlled to a temperature of 750-900°C, a time of 80-170 seconds and PH2O/PH2 in an atmosphere of 0.25-0.40
Data Source
Figure 1~3
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 comprising C: 0.002-0.10 mass%, Si: 2.0-8.0 mass%, and Mn: 0.005-1.0 mass%, subjecting the steel sheet to a hot band annealing as required, cold rolling to obtain a cold rolled sheet having a final sheet thickness, subjecting the steel sheet to primary recrystallization annealing combined with decarburization annealing, applying an annealing separator to the steel sheet surface and then subjecting to final annealing, rapid heating is performed at a rate of not less than 50°C/s in a region of 200-700°C in the heating process of the primary recrystallization annealing, and the steel sheet is held at any temperature of 250-600°C in the above region for 1-10 seconds, while a soaking process of the primary recrystallization annealing is divided into N stages (N: an integer of not less than 3), and the first stage is controlled to a temperature of 820-900°C, a time of 10-60 seconds and PH20/PH2 in an atmosphere of 0.25-0.40, and the second to (N - 1) stages are controlled to a temperature of 750-900°C, a time of 70-160 seconds and PH20/PH2 in an atmosphere of 0.25-0.40, and the last N stage is controlled to a temperature of 750-900°C, a time of 10-60 seconds and PH20/PH2 in an atmosphere of not more than 0.20, provided that the temperature of the first stage is higher than those of the second stage to the N-1 stage, whereby a grain-oriented electrical steel sheet being low in the iron loss and small in the deviation of the iron loss value is obtained.