Hot Strip Coil Pre-Sagging to Mitigate Collapse and Scrap
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Solution Overview
Problem
Hot rolled steel coils tend to sag and collapse due to relative displacement of coil wraps after being removed from the mandrel, leading to scrap loss and increased manufacturing costs, as existing solutions are either expensive or require mechanical insertion into the coil eye to prevent sagging.
Innovation Solution
A method that involves pre-sagging the coil by allowing it to sag under gravity for a specific period, then rotating it to modify the direction of sagging, allowing it to continue cooling without mechanical support, thereby mitigating the initial sag and maintaining a circular shape without the need for mechanical intervention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If the coil is conveyed with the eye vertical position, then the coil sagging is reduced, but the protruding wraps or turns on the lower end of the coil are damaged resulting in considerable scrap loss
Solution Approach 1:
The coil is pre-sagged intentionally before conveying to create an initial deformation that compensates for subsequent sagging during transport. This preliminary action ensures the coil maintains its shape throughout the conveying process without damaging the wraps or turns, thereby eliminating scrap loss while maintaining shape stability.
2Loss of substance
If the coil is conveyed with the eye horizontal position, then scrap loss is reduced, but the coil sags and becomes egg-shaped due to relative displacement of coil wraps
Solution Approach 1:
The coil is pre-sagged before horizontal conveying to anticipate and compensate for the sagging that will occur during transport. By creating an initial controlled deformation, the coil is positioned to maintain its circular shape throughout the conveying process, preventing the egg-shaped deformation that would otherwise occur.
Solution Approach 2:
The pre-sagging process creates an initial deformation that acts as a counterbalance to the gravitational sagging force during horizontal conveying. This preliminary anti-action ensures that the coil wraps remain properly positioned and the coil maintains its shape throughout the conveying process.
3Shape
If mechanical means are inserted into the coil eye to prevent sagging, then coil shape stability is improved, but the device complexity and manufacturing cost increase
Solution Approach 1:
The coil is pre-sagged to create an initial deformation that enables it to self-correct and maintain its shape during conveying without requiring any mechanical means to be inserted into the coil eye. This self-service approach eliminates the need for complex mechanical intervention devices while maintaining coil shape stability.
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 method significantly reduces coil sagging rates from 62.8% to 7.3%, minimizing scrap and increasing yield by allowing the coil to maintain a stable shape for further processing without recoiling or mechanical support.
Implementation Method 1
pre-sagging the coil by allowing it to sag under gravity for a specific period
Implementation Method 2
the direction of the sag caused by the force of gravity is modified to a direction perpendicular to the first specific direction
Data Source
AI summary
A method for mitigating the effects of coil collapse on hot strip mill coils. A hot strip coil is removed from the mandrel/downcoiler and pre-sagged to create an initial sag by allowing gravity cause the coil to sag in a first specific direction for a first period of time. Then, without coil eye support to limit sagging, the direction of the sag caused by the force of gravity is modified to a direction perpendicular to the first specific direction and gravity is allowed to sag said coil for a second period of time. The first period of time and the second period of time are chosen such that the initial sag created during the first period of time is substantially mitigated by the perpendicular sag during the second period of time. The hot strip coil being cooled enough by the end of the second period of time such that the rate of sagging of the hot strip coil has become negligible.