Grain-Oriented Electrical Steel Decarburization Heating Control
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Solution Overview
Problem
Conventional methods for producing grain-oriented electrical steel sheets face challenges in stabilizing the decarburization property and forsterite coating formation during the heating process, leading to poor magnetic properties and increased iron loss, especially when rapid heating is applied in either oxidizing or non-oxidizing atmospheres.
Innovation Solution
A controlled heating pattern during decarburization annealing, where the heating rate is adjusted to suppress excessive fayalite formation and ensure a stable forsterite coating, is implemented, involving rapid heating to a temperature above 700°C followed by a slower heating rate to a soaking temperature, in a wet hydrogen atmosphere with a specific oxygen potential, to maintain decarburization property and peeling resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If rapid heating is performed in an oxidizing atmosphere to increase Goss orientation nuclei, then secondary recrystallized grains are refined and iron loss is reduced, but excessive fayalite is formed in the oxide coating making forsterite coating formation unstable
Solution Approach 1:
The patent applies parameter changes by controlling the oxygen potential of the atmosphere during rapid heating to a specific range (0.30-0.55), which prevents excessive fayalite formation while still allowing sufficient Goss orientation nuclei formation. This optimized parameter range resolves the contradiction between reducing iron loss through grain refinement and ensuring stable forsterite coating formation.
2Reliability
If rapid heating is performed in a non-oxidizing atmosphere to suppress fayalite formation, then forsterite coating formation is stabilized, but a dense oxide layer is formed blocking decarburization reaction
Solution Approach 1:
The patent changes the atmospheric parameter from non-oxidizing to oxidizing with controlled oxygen potential (0.30-0.55). This controlled oxidation prevents dense oxide layer formation that would block decarburization, while simultaneously controlling fayalite formation to ensure stable forsterite coating. The specific oxygen potential range allows both decarburization and stable coating formation.
3Loss of energy
If wet hydrogen atmosphere with high oxygen potential is used to suppress dense oxide layer formation, then decarburization property is ensured, but excessive fayalite is formed making forsterite coating unstable
Solution Approach 1:
The patent refines the atmospheric parameter by controlling the oxygen potential to a specific range (0.30-0.55) rather than using high oxygen potential. This optimized parameter ensures sufficient decarburization while preventing excessive fayalite formation, thereby achieving stable forsterite coating formation. The specific range optimization resolves the contradiction between decarburization efficiency and coating stability.
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 a grain-oriented electrical steel sheet with improved iron loss properties and enhanced forsterite coating peeling resistance over the full length of a coil, ensuring stable magnetic performance and insulation.
Implementation Method 1
rapid heating up to not lower than 700°C is performed at a heating rate of not less than 80°C/s
Implementation Method 2
an annealing atmosphere is rendered oxidizing, so that an oxide coating composed mainly of Si and Fe oxides is formed on the surface of the steel sheet
Implementation Method 3
a forsterite (Mg 2 SiO 4 ) coating layer is formed by the reaction of the subscale and MgO
Implementation Method 4
decarburization annealing
Data Source
Figure 1~2
Figure 3~4
AI summary
In a method for producing a grain-oriented electrical steel sheet by subjecting a slab containing C: 0.002-0.10 mass%, Si: 2.5-6.0 mass%, Mn: 0.01-0.8 mass% and further containing A1 and N, or S and/or Se, or A1, N, S and/or Se as inhibitor ingredients to hot rolling, hot band annealing, cold rolling, decarburization annealing, application of an annealing separator and finish annealing, when a certain temperature within a range of 700-800°C in a heating process of the decarburization annealing is T1 and a certain temperature as a soaking temperature within a range of 820-900°C is T2, a heating rate R1 between 500°C and T1 is set to not less than 80°C/s and a heating rate R2 between T1 and T2 is set to not more than 15°C/s, whereby a grain-oriented electrical steel sheet having excellent magnetic properties and peeling resistance of forsterite coating is obtained while ensuring decarburization property even when rapid heating is performed in the heating process of the decarburization annealing.