Rolling Mill Train Off-Gauge Reduction via Tensile Stress
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Solution Overview
Problem
Conventional rolling mill methods result in significant off-gauge lengths of metal strips due to uneven thickness and lack of tensile stress, leading to scrap material, especially at the strip head and end.
Innovation Solution
The method involves reducing the initial pass thickness of each rolling stand in a rolling mill train sequentially, using built-up tensile stress between stands to achieve a continuous thickness reduction, starting from the first stand and moving upstream, with adjustments calculated by a control device to optimize the target thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the roll gap is set to a predetermined initial pass thickness before the strip head enters, then the rolling force and work demand are reduced, but a considerable length of off-gauge metal strip is produced at the strip head and end
Solution Approach 1:
The roll gap is set to a predetermined initial pass thickness before the strip head enters the rolling stand, so that thickness reduction begins immediately when the strip head contacts the rolls, eliminating the off-gauge section that would otherwise be produced during the transition from opened to closed roll gap
Solution Approach 2:
The roll gap is dynamically adjusted during the rolling process: set to a predetermined initial pass thickness before strip head entry, then closed to a predetermined value substantially simultaneously with the strip head entering, with the peripheral speed of the working rollers changed depending on the size of the roll gap
2Loss of substance
If the roll gap is opened before strip head entry to avoid off-gauge length, then off-gauge length is reduced, but the force and work demand during rolling without tension becomes considerably higher
Solution Approach 1:
The roll gap is pre-set to a predetermined initial pass thickness before the strip head enters, so that the rolling action begins immediately with the strip head contact, avoiding the high force and work demand that would result from opening the roll gap and then closing it during rolling
3Manufacturing precision
If the roll gap is closed to a predetermined value after strip head entry, then the metal strip achieves desired thickness, but considerable off-gauge length is produced at the strip head
Solution Approach 1:
The roll gap is set to a predetermined initial pass thickness before the strip head enters the rolling stand, so that the metal strip achieves the desired thickness immediately from the first contact point, eliminating the off-gauge section that would otherwise be produced before the roll gap closes
Solution Approach 2:
The roll gap is dynamically controlled: set to a predetermined initial pass thickness before strip head entry, then closed to a predetermined value substantially simultaneously with the strip head entering the roll gap, ensuring continuous thickness control throughout the rolling 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 significantly reduces off-gauge lengths by allowing thickness reduction to begin before the strip head reaches the winder and extends the reduction to all stands, ensuring a more uniform and optimized final product.
Implementation Method 1
the metal strip as it passes the rolling stand undergoes in each case a thickness reduction, since the roll gap of the rolling stand is set in each case to a predetermined initial pass thickness
Implementation Method 2
the strip tension, in particular between two rolling stands, is monitored and if necessary it is set appropriately by means of appropriate setting means
Data Source
AI summary
The invention relates to a method, a computer program and a rolling mill train for cold rolling a metal strip (200). In order to achieve a shortening of undesired off-gauge lengths, the method according to the invention provides that the head (210) of the metal strip (200) already undergoes a thickness reduction at the first active rolling stand (n) in the rolling mill train, and then is transported on to the next rolling stand, in order to undergo a further thickness reduction there. The method according to the invention also provides for further reducing the initial pass thickness at the n-th rolling stand in accordance with the tensile stress that has built up in the meantime between the n+1-th and the n-th rolling stand.