Warm Tandem Rolling for Grain-Oriented Steel Texture Control
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Solution Overview
Problem
Tandem rolling mills face challenges in ensuring sufficient time for diffusion of carbon and nitrogen to improve texture in grain-oriented electrical steel sheets, particularly at later stages where dislocation density is higher, due to shorter pass times and higher steel sheet speeds.
Innovation Solution
A method involving a tandem rolling mill with a pass line extension mechanism that extends the pass line length between stands to at least 1.3 times the distance between stands, ensuring sufficient inter-pass aging time, even at later stages with higher rolling reduction, and using a specific chemical composition for the steel material to enhance primary recrystallization texture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a tandem rolling mill is used for final cold rolling, then productivity is improved, but the pass time between stands becomes insufficient for carbon and nitrogen diffusion to improve texture
Solution Approach 1:
The patent applies preliminary action by conducting inter-pass aging treatment between cold rolling passes to pre-establish the texture conditions needed for secondary recrystallization. This preliminary texture improvement during cold rolling reduces the dependency on prolonged pass time in tandem rolling, allowing the process to achieve good magnetic properties while maintaining high productivity.
2Productivity
If the steel sheet speed is increased in later stages of tandem rolling, then productivity is improved, but the diffusion time for carbon and nitrogen becomes even shorter
Solution Approach 1:
The patent performs preliminary texture improvement through inter-pass aging at lower speeds in earlier rolling stages, building up the necessary dislocation structure and carbon-nitrogen distribution before high-speed rolling. This preliminary preparation ensures that even with reduced diffusion time at high speeds, the texture quality remains sufficient for secondary recrystallization.
Solution Approach 2:
The patent changes process parameters by controlling steel sheet temperature within specific ranges (150-280°C) during inter-pass aging, and by adjusting the pass line extension ratio (≥1.3 times) to optimize the balance between diffusion time and productivity. These parameter changes enable texture improvement without sacrificing production efficiency.
3Manufacturing precision
If the pass line length is extended to increase inter-pass aging time, then texture is improved, but the equipment complexity increases
Solution Approach 1:
The patent solves the contradiction by extending the pass line in the spatial dimension (creating loops or curves between stands) rather than adding more rolling stands in sequence. This dimensional approach increases the effective aging distance without proportionally increasing equipment complexity, as it utilizes the existing space between stands more efficiently.
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 the texture and magnetic properties of grain-oriented electrical steel sheets, achieving excellent iron loss properties while maintaining high productivity and low production costs.
Implementation Method 1
the steel sheet is maintained at an appropriate temperature during the rolling or during the pass between rollings to precipitate carbon and nitrogen on the dislocation and inhibit the migration of the dislocation
Implementation Method 2
A method involving a tandem rolling mill with a pass line extension mechanism that extends the pass line length between stands to at least 1.3 times the distance between stands, ensuring sufficient inter-pass aging time
Implementation Method 3
a method disclosed in Patent Literature 2 performing heat treatment (aging treatment) on a cold-rolled sheet at a low temperature during rolling. The method aims to diffuse solid-solution elements such as carbon and nitrogen at low temperature to segregate on the dislocation introduced by the rolling
Implementation Method 4
The grain-oriented electrical steel sheet is usually produced using a steel material with a chemical composition comprising approximately not more than 4.5 mass % Si and other components that form a so-called inhibitor such as MnS, MnSe, and MN to cause secondary recrystallization
Data Source
AI summary
In a method of producing a grain-oriented electrical steel sheet comprising subjecting a steel slab containing no inhibitor-forming components to hot rolling, cold rolling, primary recrystallization annealing working also as decarburization and to final annealing causing secondary recrystallization after applying an annealing separator on the surface, the final cold rolling for cold rolling the steel sheet to the final thickness uses a warm rolling with a tandem rolling mill at a total rolling reduction of not less than 80% at 150 to 280° C. and is performed by extending a pass line length of the steel sheet between the stands so that T satisfies T≥1.3×L/V, where an distance between the stands is defined as L(m), a speed of the steel sheet passing between the stands is defined as V (mpm), and a pass time during which the steel sheet passes between the stands is defined as T(min).