Non-oriented Electrical Steel Sheet Two-stage Finish Annealing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for producing non-oriented electrical steel sheets fail to stably achieve high magnetic flux density through rapid heating in finish annealing, particularly due to issues with induction heating causing surface defects and increased production costs, and inefficiencies in heating techniques.
Innovation Solution
A two-stage heating method involving induction heating up to at least 720°C at an average rate of 50°C/sec between 600°C and 700°C, followed by radiation heating, with a transition time of no more than 3 seconds, is employed in the finish annealing process to enhance magnetic flux density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If induction heating is used for rapid heating in finish annealing, then heating efficiency is improved, but surface defects occur due to sparks between conductor roll and steel sheet
Solution Approach 1:
The heating process is segmented into two distinct stages: first induction heating to rapidly raise temperature to 720°C or higher, then radiation heating to complete the heating process. This segmentation allows each heating method to be used in its optimal range, avoiding the harmful effects of continuous induction heating while maintaining its efficiency benefits.
Solution Approach 2:
Radiation heating serves as an intermediary method that bridges the gap between induction heating and the final heating requirement. It takes over from induction heating at the critical point where surface defects would occur, providing a spark-free heating method to complete the process.
2Speed
If rapid heating is conducted by electric heating, then heating speed is improved, but sparks are generated causing surface defects
Solution Approach 1:
The heating process is divided into two stages: rapid induction heating phase and radiation heating phase. The induction heating provides the necessary speed, while the radiation heating phase eliminates spark generation in the final heating stage.
Solution Approach 2:
The patent converts the potential harm of continuous induction heating (sparks and surface defects) into a benefit by using it only for the rapid temperature rise phase, then switching to radiation heating which eliminates the harmful effects while completing the heating process.
3Manufacturing precision
If induction heating is used with cooling and reheating, then magnetic flux density is increased, but production cost and equipment cost increase
Solution Approach 1:
The patent extracts the essential function of rapid heating from the complex cooling-reheating cycle. By using induction heating followed by radiation heating, it achieves the desired magnetic flux density without requiring the additional cooling and reheating equipment and processes.
Solution Approach 2:
The patent changes the heating parameters by introducing a two-stage heating process with specific temperature thresholds (720°C or higher for induction heating completion). This parameter-based control achieves the magnetic flux density improvement without the need for complex cyclic processing equipment.
4Manufacturing precision
If conventional heating methods are used in finish annealing, then production cost is reduced, but magnetic flux density cannot be stably increased
Solution Approach 1:
The patent applies parameter changes by specifying exact heating conditions: induction heating at an average rate of not less than 50°C/sec between 600°C and 720°C, with the induction heating phase completing at 720°C or higher. These precise parameter specifications enable stable magnetic flux density increase while controlling costs.
Solution Approach 2:
The patent uses partial induction heating (only until 720°C or higher is reached) followed by radiation heating for the remainder. This partial use of the more expensive induction heating method, combined with radiation heating, achieves the desired magnetic flux density while controlling production costs.
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 method stably increases the magnetic flux density of non-oriented electrical steel sheets while reducing production costs and avoiding surface defects, thereby meeting the demand for high magnetic flux density and low iron loss.
Implementation Method 1
performing an induction heating and subsequently a radiation heating, conducting the induction heating up to not lower than 720°C at an average heating rate of not less than 50°C/sec between 600°C and 700°C
Implementation Method 2
performing an induction heating and subsequently a radiation heating
Data Source
Figure 1~2
Figure 3
AI summary
A method for producing a non-oriented electrical steel sheet by hot rolling a steel slab containing C: not more than 0.0050%, Si: not more than 5.0%, Mn: not more than 3.0%, P: not more than 0.2%, S: not more than 0.005%, Al: not more than 3.0%, N: not more than 0.005%, Ni: not more than 3.0%, Cr: not more than 5.0%, Ti: not more than 0.005%, Nb: not more than 0.005%, B: not more than 0.005% and O: not more than 0.005% by mass% and subjecting the sheet to a hot band annealing, if necessary, and further to a cold rolling and a finish annealing, wherein the heating in the finish annealing is conducted in two stages of performing an induction heating and subsequently a radiation heating and the induction heating is conducted up to not lower than 720°C at an average heating rate of not less than 50°C/sec between 600°C and 700°C and a time from the end of the induction heating to the start of the radiation heating is set to not more than 8 seconds, whereby a high magnetic flux density can be obtained stably.