Protruding Mandrel Geometry for Hot-Rolled Coil Flatness
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Solution Overview
Problem
The flatness of hot-rolled steel sheets in coils manufactured by winding with a mandrel in the hot-rolling process is compromised due to a combination of temperature and tight winding factors, leading to uneven thermal strain and plastic deformation, which existing methods have not adequately addressed.
Innovation Solution
The mandrel is designed with a protruding shape in the axial direction to compensate for non-uniform diameter reduction during winding, ensuring a uniform diameter and reducing peripheral length differences, thereby improving the flatness of the hot-rolled steel sheet.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the hot-rolled steel sheet is wound with a conventional mandrel, then the winding process is simple, but the flatness of the steel sheet deteriorates due to non-uniform tension distribution and peripheral length differences
Solution Approach 1:
The mandrel is designed with an asymmetric protruding shape at its center portion in the axial direction, creating intentional geometric asymmetry to compensate for the non-uniform tension distribution that occurs during winding. This asymmetric design allows the center portion to have a larger diameter, which compensates for the greater peripheral length differences that occur at the center of the steel sheet width, thereby improving flatness without requiring complex external control systems
Solution Approach 2:
The protruding shape of the mandrel is designed in advance based on predicted peripheral length difference ratios, allowing the mandrel to pre-compensate for flatness deterioration before the winding process begins. The mandrel's geometry is predetermined to counteract the expected non-uniform tension distribution and peripheral length differences that will occur during winding, eliminating the need for real-time adjustments during the winding process
2Manufacturing precision
If temperature distribution is controlled to improve flatness, then thermal strain is reduced, but the tight winding factor causing plastic deformation is not addressed
Solution Approach 1:
The invention separates the flatness control problem into two distinct factors: thermal strain (addressed by temperature control) and plastic strain from tight winding (addressed by mandrel geometry). By extracting and addressing the tight winding factor independently through mandrel design, the solution acknowledges that temperature control alone is insufficient and adds a geometric compensation approach that works alongside thermal management
Solution Approach 2:
The mandrel's protruding shape creates local geometric variation at the center portion, providing different effective diameters at different locations along the axial direction. This local quality change allows the mandrel to specifically address the greater peripheral length differences at the center of the steel sheet while maintaining standard geometry at the end portions, providing targeted flatness improvement
3Manufacturing precision
If all coils are conveyed to precise process for flatness correction, then flatness specification is met, but manufacturing cost increases
Solution Approach 1:
The mandrel with protruding shape enables the winding process itself to generate the flatness improvement, making the coiling operation self-correcting for flatness issues. The mandrel's geometry automatically compensates for peripheral length differences during the normal winding process, eliminating the need for subsequent expensive precise correction processes for coils that meet flatness specifications
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 suppresses peripheral length differences and enhances the flatness of the hot-rolled steel sheet, reducing the need for precise shape correction processes and lowering manufacturing costs by maintaining flatness within standard values.
Implementation Method 1
the tight winding under the non-uniform tension distribution causes plastic deformation of an inner peripheral portion of the coil, resulting in plastic strain
Implementation Method 2
The first temperature factor is thermal strain caused by non-uniform temperature distribution in the width direction of the hot-rolled steel sheet just before it is wound on the coiler (mandrel)
Data Source
AI summary
Flatness of a hot-rolled steel sheet in a coil is improved when the hot-rolled steel sheet is wound with a mandrel in a hot-rolling process to manufacture a coil. The mandrel has a protruding shape with a center portion in an axial direction protruding from both end portions when seen from a lateral side in the axial direction. Regarding a peripheral length difference, which is a difference between a peripheral length of the center portion of the mandrel and a peripheral length at a predetermined distance from the center portion, the ratio of the peripheral length difference to the peripheral length of the center portion is preferably 0.0002 to 0.012. The protruding shape may be a trapezoidal shape or a polynomial function shape.