Tandem Warm Rolling for Grain-Oriented Steel Inter-Pass Aging
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Solution Overview
Problem
The tandem rolling mill process in producing grain-oriented electrical steel sheets faces challenges in ensuring sufficient time for diffusion of carbon and nitrogen, which is crucial for improving texture and magnetic properties.
Innovation Solution
The method involves reheating a steel slab to a specific temperature, subjecting it to hot rolling and multiple cold rollings with intermediate annealing, and using a tandem rolling mill with a pass line extension mechanism to increase the pass time between stands, especially at later stages where the total rolling reduction is significant.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a tandem rolling mill is used for cold rolling to achieve high productivity, then production efficiency is improved, but the pass time between stands becomes insufficient for carbon and nitrogen diffusion
Solution Approach 1:
The patent introduces a movable roll that can dynamically adjust the pass line length between stands during the rolling process. By moving the roll along the pass line, the system extends the effective pass time for aging treatment while maintaining the high-speed productivity characteristics of the tandem rolling mill. This dynamic adjustment allows optimization of both productivity and aging time.
Solution Approach 2:
The patent adds a spatial dimension to the rolling process by introducing a movable roll that operates perpendicular to the main rolling direction. This allows the pass line to be extended in length without increasing the distance between fixed stands, thereby increasing the aging time while maintaining the compact high-productivity tandem mill configuration.
2Manufacturing precision
If the pass line length is extended to increase pass time for aging treatment, then texture quality is improved, but the distance between stands must be increased
Solution Approach 1:
The movable roll provides a dynamic solution to extend the pass line length without permanently increasing the distance between stands. The roll can be positioned at different locations along the pass line to achieve the required aging time, and can be repositioned or removed when high productivity is needed. This maintains flexibility while improving texture quality.
Solution Approach 2:
The movable roll acts as an intermediary element between the fixed stands, creating an extended pass line through which the steel sheet travels. This intermediary component allows the aging treatment to occur over a longer path without requiring the stands themselves to be farther apart, thus improving texture quality without increasing the overall mill footprint.
3Manufacturing precision
If a reverse rolling mill is used to allow long aging treatment, then texture control is improved, but productivity is reduced compared to tandem rolling mill
Solution Approach 1:
The patent merges the advantages of both reverse rolling mill and tandem rolling mill by combining the aging treatment capability of the former with the high productivity of the latter. The movable roll mechanism allows the tandem mill to provide extended aging time similar to reverse rolling, while maintaining the continuous high-speed operation characteristic of tandem mills, thus achieving both good texture control and high productivity.
Solution Approach 2:
By making the roll movable rather than fixed, the system can adapt its configuration to provide extended aging time when needed, then return to normal high-speed operation. This dynamic capability allows the system to achieve good texture control during specific passes while maintaining overall high productivity across the entire production process.
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 promotes inter-pass aging, leading to improved primary recrystallization texture and enhanced magnetic properties, even when using a tandem rolling mill, which is known for its high productivity.
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
extending a pass line length of the steel sheet between the stands so as to satisfy the following equation (1): L×1.3≤pass line length＜5L
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).