Hold-down Roller for Flying Work Roll Changes in Hot Strip Mills
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Solution Overview
Problem
In continuous hot strip mills, work roll changes during rolling operations are challenging due to the need to maintain production and quality, as stopping the casting process is not feasible, and existing methods fail to ensure strip tension control when a roll stand is opened for replacement, leading to potential defects in the rolled strip.
Innovation Solution
The method involves disengaging the work rolls by opening the roll stand and using a controllable hold-down roller to maintain strip tension, allowing for 'flying' roll changes by guiding the strip through the open stand without contact with the work rolls, utilizing hold-down rollers and loopers to manage tension and temperature control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the roll stand is opened to change work rolls, then the work rolls can be exchanged, but the strip tension control is lost and the strip may be pressed against the upper work roll
Solution Approach 1:
A hold-down roller is introduced as an intermediary device between the looper and the work rolls. This hold-down roller takes over the strip tension control function when the roll stand is opened, preventing the strip from being pressed against the upper work roll while allowing the work rolls to be exchanged. The hold-down roller acts as a temporary mediator that maintains tension control during the transition period when the normal tension control mechanism is unavailable.
2Manufacturing precision
If the casting process is stopped to change work rolls, then quality can be maintained, but production is interrupted
Solution Approach 1:
The invention enables continuous casting and rolling operations to proceed without interruption during work roll changes. By using the hold-down roller to maintain strip tension control while the roll stand is opened, the casting process can continue uninterrupted, and the rolling process can resume immediately after roll exchange. This maintains the continuity of useful action throughout the production process, eliminating downtime while preserving strip quality.
3Reliability
If the looper is active during roll change, then strip tension might be maintained, but the strip could be pressed against the upper work roll preventing roll change
Solution Approach 1:
The hold-down roller serves as a mediator that coordinates the interaction between the looper and the work rolls during the roll change process. It allows the looper to remain active for tension maintenance while preventing the strip from contacting the upper work roll, thereby enabling both tension maintenance and roll exchangeability simultaneously.
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
Enables efficient and defect-free work roll changes during continuous operation by maintaining strip tension and temperature control, allowing for uninterrupted production and quality preservation by identifying and separating defective strip areas.
Implementation Method 1
a controllable strip tension replacing the strip tension of the open roll stand can be applied via at least one hold-down roller
Implementation Method 2
the looper, which is usually arranged between the roll stands, would push the hot strip upwards
Data Source
Figure 1~3
AI summary
The invention relates to a method for the flying changing of working rolls in continuous casting and rolling installations and hot strip rolling mills, in particular continuous hot strip rolling mills, wherein, to exchange the working rolls by opening the roll stand (2), they can be disengaged from the hot strip to be rolled. According to the invention, a strip tension that can be regulated and substitutes the strip tension of the opened roll stand (2) can be applied to the hot strip (6) to be rolled, before and/or after it enters the opened roll stand (2), by means of at least one hold-down roller (5) that can be introduced into the rolling line.