Grain-Oriented Steel Cold Rolling with Alternating Work Roll Diameters
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Solution Overview
Problem
The production of grain-oriented electrical steel sheets with high magnetic flux density and low core loss requires a primary recrystallization structure with uniform crystal grain diameter and aligned Goss-oriented grains, which is challenging due to the limitations of existing cold rolling technologies, particularly with high Si content steel sheets that exhibit large deformation resistance, restricting rolling reduction and affecting magnetic properties.
Innovation Solution
A method involving a split-housing reversible cluster rolling mill that alternates between small-diameter and large-diameter work rolls during cold rolling, with inter-pass aging using deformation heating, to form a primary recrystallization structure that enhances magnetic flux density by optimizing rolling conditions and texture alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a small-diameter work roll is used for cold rolling high Si content steel sheet, then the rolling reduction limit increases and productivity improves, but the roll deformation increases affecting shape and magnetic properties
Solution Approach 1:
The patent introduces a support roll as an intermediary element that provides mechanical support to the small-diameter work roll during cold rolling. This support roll prevents the work roll from deforming under the high rolling forces required for high Si content steel, thereby maintaining both the productivity benefits of small-diameter rolls and the shape accuracy required for good magnetic properties
Solution Approach 2:
The rolling system is transformed into a composite structure where a small-diameter work roll is combined with a larger support roll. This composite rolling system allows the small work roll to provide high reduction capability while the larger support roll provides structural stability and prevents deformation, solving the contradiction between productivity and shape control
2Shape
If reversible rolling with large-diameter work roll is used, then roll deformation is reduced maintaining shape and magnetic properties, but the rolling reduction limit decreases restricting productivity
Solution Approach 1:
The support roll acts as an intermediary that enables the system to achieve both large-diameter roll stability and small-diameter roll productivity. By providing mechanical support, it allows the use of smaller work rolls without suffering from the reduced rolling reduction limit that would otherwise constrain productivity
3Strength
If high Si content is used to achieve high magnetic flux density, then core loss decreases and magnetic properties improve, but the deformation resistance increases making cold rolling difficult
Solution Approach 1:
The patent employs dynamic rolling conditions including controlled rolling speeds, temperature management, and alternating rolling directions to reduce the effective deformation resistance of high Si content steel. These dynamic adjustments allow the material to be more compliant during rolling while maintaining its high magnetic flux density properties in the final product
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 improves magnetic flux density and reduces core loss by forming a uniform primary recrystallization structure, allowing for higher reduction ratios while maintaining productivity and preventing roll deformation, resulting in a grain-oriented electrical steel sheet with enhanced magnetic properties.
Implementation Method 1
high-temperature rolling utilizing deformation heating is conducted
Implementation Method 2
the aging effect following inter-rolling reel winding is utilized
Data Source
Figure 1(a)~1(b)
Figure 2
Figure 3
AI summary
The invention produces a grain-oriented electrical steel sheet having a primary recrystallization structure in which Goss-oriented crystal grains and crystal grains having a coincidence orientation relationship to the Goss orientation are aligned in the rolling direction. It is characterized heating a slab containing, in mass%, C: 0.025 to 0.10%, Si: 2.5 to 4.5%, Mn: 0.03 to 0.55%, and Al: 0.007 to 0.040% to 1,100 to 1,450 °C or greater; hot rolling the slab to obtain a hot-rolled sheet; annealing the hot-rolled sheet; cold rolling the annealed sheet multiple times with a split-housing reversible cluster rolling mill; and subjecting the cold-rolled sheet to primary recrystallization annealing followed by secondary recrystallization annealing, in which method: (a) a first cold rolling or first and second cold rollings are performed using a small-diameter work roll of 55 mm to less than 105 mm diameter; (b) a second or third cold rolling to a penultimate cold rolling are performed using a large-diameter work roll of 105 mm to less than 150 mm diameter; and (c) a final cold rolling is conducted using a small work roll of a diameter smaller than the diameter of the large-diameter work roll.