Stirrer-Roll Electromagnetic Stirring for Slab Surface Defects
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Solution Overview
Problem
The continuous casting of stainless steels and silicon steels often results in surface defects like roping and ridging due to inadequate solidification structure, and existing electromagnetic stirring methods are costly and inflexible, especially in the secondary cooling zone where staged stirring is necessary for optimal results but not economically viable.
Innovation Solution
Implementing electromagnetic stirring in segment zero using at least two stirrer-rolls that generate magnetic fields traveling in the same direction, replacing smaller support rolls to achieve a predominantly equiaxed solidification structure, which improves metal behavior during rolling and prevents roping or ridging defects, while allowing better control of superheat and reducing electrical power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electromagnetic stirring is performed in the secondary cooling zone using staged stirring, then the internal soundness of the cast metal is improved, but the electrical power consumption and cost increase significantly
Solution Approach 1:
The patent applies preliminary action by performing electromagnetic stirring in segment zero, which is the initial section of the secondary cooling zone where the slab first enters. This early stirring action promotes equiaxed solidification structure formation at the critical early stage, preventing roping and ridging defects before they can develop. By acting early rather than later in the cooling zone, the process achieves the desired internal soundness with reduced energy consumption compared to staged stirring performed further downstream.
2Reliability
If box-type stirrers are used for electromagnetic stirring, then the stirring effect is achieved, but the electrical power consumption increases by about five times compared to stirrer-rolls
Solution Approach 1:
The patent extracts the electromagnetic inductor from the box-type configuration and integrates it directly into the support roll structure. This creates a stirrer-roll where the inductor is embedded within the roll itself, allowing the magnetic field to be applied directly to the slab through the roll contact point. This extraction of the inductor from the box configuration eliminates the need for large air gaps and complex positioning systems, reducing electrical power consumption by about five times while maintaining effective stirring.
Solution Approach 2:
The patent merges the support roll function with the electromagnetic inductor function into a single integrated component - the stirrer-roll. The support roll structure itself becomes the housing for the electromagnetic inductor, combining mechanical support and electromagnetic stirring functions. This merging eliminates the separate box-type inductor assembly and its associated high power consumption, achieving both structural support and effective electromagnetic stirring with minimal energy input.
3Reliability
If stirrer-rolls of large diameter are used for electromagnetic stirring, then the stirring effectiveness is improved, but the regularity of mechanical support for the slab is compromised
Solution Approach 1:
The patent applies dynamics by making the diameter of the stirrer-roll variable rather than fixed. The roll diameter can be adjusted based on the specific casting conditions, slab dimensions, and desired stirring intensity. This dynamic adjustment capability allows optimization of stirring effectiveness for different production scenarios while maintaining regular mechanical support by selecting appropriate diameters that fit within the available space and maintain proper support geometry.
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 enhances the solidification structure of flat metal products, preventing surface defects and improving rolling behavior, making the process suitable for ferritic stainless steel and silicon steel, while also being cost-effective and flexible enough to adapt to varying casting conditions without compromising the continuous casting process.
Implementation Method 1
electromagnetic stirring consists, as is known, in subjecting the slab to one or more moving magnetic fields (that is to say fields in which the maximum intensity moves over time in a defined direction in space), the action of which on the molten metal is therefore manifested by entrainment of the metal identical, in sense and direction, to the displacement of the magnetic field
Implementation Method 2
The travelling magnetic field is created by a polyphase linear inductor
Implementation Method 3
The walls are vigorously cooled by the circulation of water so as to continuously extract, via the base of this mould, a product that has already solidified on the outside
Implementation Method 4
the cast product, guided by support and guide rolls (hereafter called support rolls), is sprayed with water in order to extract the heat necessary for its complete solidification
Data Source
AI summary
A process for continuous casting of slabs or other metal products of elongate cross section, for example made of steel, in which a molten metal is poured into a cooled mold, and the externally solidified product is continuously extracted from the mold and guided in a secondary cooling zone downstream of the mold. To obtain a cast product exhibiting predominantly equiaxed solidification, the product extracted from the mold is subjected to electromagnetic stirring in segment zero of the secondary cooling zone by at least two stirrer-rolls incorporated into the segment zero.