Grain-Oriented Electrical Steel Sheet Manufacturing
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Solution Overview
Problem
Current methods for manufacturing grain-oriented electrical steel sheets struggle to effectively reduce core loss and its variations, which is crucial for energy-efficient transformer applications, as they require precise control of magnetic domains and are costly in terms of man-hours and resources.
Innovation Solution
A manufacturing method that involves adjusting the composition of the slab, particularly the Sn and P content, and optimizing the conditions of hot-rolled sheet annealing, cold rolling, and nitridation treatment to increase the number of grains in the Goss orientation, thereby improving core loss and reducing its variations without the need for complex domain control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If artificial grooves and/or strains are introduced into the surface to subdivide 180-degree magnetic domains, then eddy current loss is drastically decreased, but manufacturing cost and man hours increase
Solution Approach 1:
The steel sheet performs self-service by utilizing its inherent material properties (Sn and P contents, crystal grain structure) to achieve magnetic domain subdivision and reduce eddy current loss, eliminating the need for external artificial groove introduction and complex domain control processes
Solution Approach 2:
The mechanical process of artificially introducing grooves and strains is replaced by chemical and metallurgical control during manufacturing, specifically by adjusting Sn and P content ranges and controlling hot-rolled sheet annealing conditions to achieve the desired magnetic properties through material composition rather than mechanical modification
2Loss of energy
If annealing conditions are adjusted to improve core loss, then magnetic properties are enhanced, but it has been difficult to sufficiently improve core loss
Solution Approach 1:
The invention changes key material parameters by specifying precise ranges for Sn content (0.003% to 0.030%) and P content (0.005% to 0.025%), and by controlling hot-rolled sheet annealing conditions (temperature of 750°C to 1200°C, time of 30 seconds to 10 minutes), which enables sufficient core loss improvement that previous annealing condition adjustments alone could not achieve
Solution Approach 2:
The invention creates a composite effect by combining specific alloying elements (Sn, P, Si, Mn, Al) with controlled processing conditions (hot-rolled sheet annealing parameters) to achieve a synergistic improvement in magnetic properties and core loss reduction that exceeds the effect of individual parameters
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 effectively improves core loss and reduces its variations, enhancing the magnetic properties of the steel sheets without the need for costly domain control methods, resulting in more efficient energy conversion.
Implementation Method 1
a slab is heated at a temperature of 1300°C or higher to solid-dissolve fine precipitates called inhibitors almost completely
Implementation Method 2
performing hot-rolled sheet annealing of the hot-rolled steel sheet more than once to obtain an annealed steel sheet
Implementation Method 3
performing cold rolling of the annealed steel sheet to obtain a cold-rolled steel sheet; performing decarburization annealing of the cold-rolled steel sheet to obtain a decarburization-annealed steel sheet in which primary recrystallization has been caused
Implementation Method 4
finish annealing the decarburization-annealed steel sheet to make secondary recrystallization occur
Implementation Method 5
The control of the orientation of crystal grains is conducted with catastrophic grain growth phenomenon called secondary recrystallization
Implementation Method 6
thereafter, is subjected to hot-rolling, cold-rolling, decarburization annealing, a nitridation treatment, finish annealing, and so on, to cause AlN, (Al, Si)N, and so on to precipitate as an inhibitor during the nitridation treatment
Implementation Method 7
to cause AlN, (Al, Si)N, and so on to precipitate as an inhibitor during the nitridation treatment
Implementation Method 8
is subjected to hot-rolling, cold-rolling, annealing, and so on
Data Source
Figure 1
AI summary
A slab having a desired composition containing Sn: 0.02% to 0.20% and P: 0.010% to 0.080% is used. A finishing temperature of hot rolling is 950°C or lower, hot-rolled sheet annealing is performed at 800°C to 1200°C, a cooling rate from 750°C to 300°C in the hot-rolled sheet annealing is 10°C/second to 300°C/second, and a reduction ratio of cold rolling is 85% or more. A nitridation treatment in which an N content of a decarburization-annealed steel sheet is increased is performed between beginning of decarburization annealing and occurrence of secondary recrystallization in finish annealing.