Non-Oriented Electrical Steel Rolling to Suppress Ridging
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Solution Overview
Problem
Conventional methods for producing non-oriented electrical steel sheets with high alloy content and thin thickness face challenges in suppressing ridging, particularly when using high amounts of Si, Al, and Mn, which complicates recrystallization during hot-rolled sheet annealing.
Innovation Solution
A method involving continuous casting of steel slabs with specific chemical compositions, followed by a hold process at high temperatures to promote precipitation and coarsening of MnS and AlN, and then subjecting the slabs to rough and finish rolling with high total rolling reductions to refine the microstructure and enhance recrystallization, thereby suppressing ridging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high amounts of alloying elements (Si, Al, Mn) are added to increase specific resistance, then electrical efficiency is improved, but recrystallization during hot-rolled sheet annealing becomes more difficult and ridging occurs on the surface
Solution Approach 1:
The patent applies preliminary action by performing a hold process at high temperature (1100-1300°C) before hot rolling to promote precipitation and coarsening of MnS and AlN. This preliminary precipitation action modifies the microstructure in advance, enabling subsequent recrystallization during annealing even in the presence of high alloying elements, thereby preventing ridging while maintaining electrical efficiency
Solution Approach 2:
The patent changes physical parameters by implementing specific hold temperature (1100-1300°C) and hold time (60s or more) conditions, followed by controlled rolling reductions (80% or more for both rough and finish rolling). These parameter changes create optimal conditions for precipitation and recrystallization, resolving the contradiction between maintaining high alloy content for electrical efficiency and achieving surface quality
2Ease of manufacture
If thinner hot-rolled steel sheets are used to reduce cold rolling load, then cold rolling feasibility is improved, but hot rolling load increases and shape control becomes more difficult
Solution Approach 1:
The patent changes the physical state and microstructure parameters through high-temperature holding and controlled rolling processes. By achieving high rolling reductions (80% or more) in both rough and finish rolling with proper microstructure control, the process enables production of thinner sheets (0.4-2.0mm) that are feasible for cold rolling while managing hot rolling loads through optimized process parameters
3Manufacturing precision
If high rolling reductions are applied in both rough and finish rolling to refine microstructure, then recrystallization is enhanced and ridging is suppressed, but process complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the hot rolling process into distinct rough rolling and finish rolling stages, each with specific reduction requirements (80% or more). This segmentation allows for controlled microstructure refinement at each stage, achieving the desired manufacturing precision while organizing the process complexity into manageable segments
Solution Approach 2:
The patent uses specific parameter changes including hold temperature (1100-1300°C), hold time (60s or more), and rolling reduction ratios (80% or more for both stages) to achieve microstructure control. These defined parameter ranges provide a systematic approach that reduces process complexity by establishing clear operational targets
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 allows for the production of non-oriented electrical steel sheets with high alloy content and thin thickness without ridging, achieving low costs and improved recrystallization during annealing.
Implementation Method 1
holding at a high temperature before the hot rolling process, dividing the hot rolling into rough rolling and finish rolling with reheating treatment between the two
Implementation Method 2
holding at a high temperature before the hot rolling process, dividing the hot rolling into rough rolling and finish rolling with reheating treatment between the two
Implementation Method 3
subjecting the steel slab to rough rolling, reheating treatment, and finish rolling in sequence to obtain a hot-rolled steel sheet
Implementation Method 4
increasing the rolling reduction of the rough rolling and the finish rolling
Data Source
AI summary
In a process using a thin slab, ridging is suppressed. A method of producing a hot-rolled steel sheet for a non-oriented electrical steel sheet includes: continuous casting producing a steel slab having a defined chemical composition and a thickness of 50 mm to 200 mm; transferring the steel slab to a furnace while maintaining a surface temperature of the steel slab at 800° C. or more; holding the steel slab in the furnace under conditions including a hold temperature of 1100° C. to 1300° C. and a hold time of 60 s or more; and a hot rolling process under conditions of (1) and (2) of rough rolling, reheating treatment, and finish rolling in sequence to obtain a hot-rolled steel sheet:(1) total rolling reduction of the rough rolling: 80% or more, and(2) total rolling reduction of the finish rolling: 80% or more.