Multi-Stand Rolling Mill Thickness Transition With Stable Mass Flow
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Solution Overview
Problem
Existing rolling mill technologies face challenges in efficiently changing the thickness of metallic rolling stock on-the-fly, leading to increased scrap and process disruptions, particularly in continuous operations, due to inaccuracies in position tracking and stress on rolling stands when transitioning between different thicknesses.
Innovation Solution
A method that adjusts the outlet thickness by setting the inlet speed of the rolling stock based on the outlet speed of upstream units, using a combination of position-controlled and rolling force-controlled roll stands to minimize scrap and maintain constant mass flow, allowing for smooth transitions without disrupting upstream processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If position-controlled roll gap adjustment is used for all rolling stands, then thickness control precision is improved, but measurement accuracy deteriorates at high speeds near the end of the rolling train
Solution Approach 1:
The patent changes the control parameter from position-controlled to rolling force-controlled for rolling stands near the end of the train. This allows the system to maintain manufacturing precision by using rolling force as the controlled parameter instead of position, which becomes difficult to measure accurately at high speeds.
Solution Approach 2:
The patent dynamically switches between position control and rolling force control depending on the location in the rolling train. Rolling stands at the beginning use position control, while those at the end use rolling force control, optimizing performance for each section's specific operating conditions.
2Productivity
If simultaneous transfer of all rolling stands from first to second pass plan is performed, then throughput is improved, but rolling stock consumption increases due to scrap
Solution Approach 1:
The patent prepares a transfer section in advance before the actual thickness change is needed. This transfer section is rolled through the rolling train beforehand, allowing the rolling stands to be progressively transferred from the first pass plan to the second pass plan without causing disruptions that would require scrapping the entire rolling stock.
Solution Approach 2:
The transfer section acts as an intermediary element that facilitates the transition between different pass plans. By rolling this intermediate section through the train, the system can change thickness settings progressively rather than simultaneously, avoiding the need to scrap entire batches of rolling stock.
3Stability of the object's composition
If inlet speed is adjusted to compensate for mass flow fluctuations during transfer, then mass flow stability is improved, but upstream unit operation is disrupted
Solution Approach 1:
The patent segments the rolling train into different control zones: rolling stands at the beginning operate in position control mode while those at the end operate in rolling force control mode during the transfer. This segmentation allows mass flow fluctuations to be managed locally without propagating disruptions to upstream units.
Data Source
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AI summary
The invention relates to a rolling mill, a control and/or regulation device and a method for adjusting a discharge thickness (H3, H3') of rolling stock (G), especially a hot strip, that passes through a multi-stand mill train (2). A first section (G-1) of the rolling stock (G) is rolled to a first discharge thickness (H3) and a second section (G-2) of the rolling stock (G) is rolled to a second discharge thickness (H3') that is different from the first discharge thickness (H3). The transition from the first discharge thickness to the second discharge thickness proceeds at a feed rate (V0) of the rolling stock (G) to the mill train (2) which feed rate is adjusted depending on a discharge rate (Vg) of the rolling stock (G) of a unit (6) that is mounted upstream in the throughput direction of the mill train (2), thereby allowing a method which substantially proceeds without provoking feedback reactions from units that are mounted upstream in the throughput direction of the mill train.