Flat Rolling Line With Rapid Heating for Strip Temperature Uniformity
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Solution Overview
Problem
Existing rolling plants face challenges in maintaining the optimum temperature of metal strips at the outlet of the last finishing stand, particularly in coil-to-coil and semi-endless modes, which can lead to unwanted phase changes and non-uniform mechanical properties in the final product.
Innovation Solution
The proposed method involves a rolling plant configuration where a rapid heating device is always active in coil-to-coil or semi-endless modes to maintain the metal strip temperature between 830° C and 860° C, and the rolling speed is set to a constant value below 12 m/s to avoid the need for speed-up operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the rolling mass flow is increased to maintain strip temperature above 850°C at the outlet of the last finishing stand, then the temperature control is improved, but the rolling speed must be increased which causes the strip head to rise dangerously due to aerodynamic effects
Solution Approach 1:
The strip head is wound onto the winding reel before the body and tail of the strip pass through the finishing stands. This preliminary action removes the strip head from the path where aerodynamic effects would cause it to rise, allowing the finishing stands to operate at higher speeds needed to maintain optimal temperature without causing strip head instability
Solution Approach 2:
The rolling speed is dynamically adjusted during the passage of each strip. The speed is increased to maintain temperature above 850°C while the winding reel operates at a different speed to accommodate the strip head being wound first. This dynamic speed adjustment allows optimization of temperature control without being constrained by the aerodynamic limitations of constant speed operation
2Productivity
If the rolling speed is increased to reduce temperature losses and maintain optimal temperature, then the productivity is improved, but oversized electric motors are required which increases device complexity and cost
Solution Approach 1:
The strip head is wound onto the winding reel before the body and tail pass through the finishing stands. This allows the finishing stands to operate at higher speeds optimized for temperature control and productivity, while the winding reel speed is independently controlled. The preliminary winding action decouples the speed requirements, allowing high-speed rolling without requiring oversized motors that would be needed if the winding reel had to match the high rolling speed
Solution Approach 2:
Different components of the rolling system operate at different speeds. The finishing stands can run at high speeds to maintain optimal temperature and improve productivity, while the winding reel operates at a speed appropriate for its function. This dynamic speed differentiation allows the system to achieve high productivity without requiring all components to be oversized, thereby reducing device complexity and cost
3Temperature
If the rolling speed is varied to control temperature, then the temperature control is improved, but the production of thin strip below 1.2 mm is complicated due to difficulty of entry into finishing stands
Solution Approach 1:
The strip head is wound onto the winding reel before the body enters the finishing stands. This preliminary action creates a buffer that allows the finishing stands to operate at higher speeds needed for temperature control, while the winding reel accommodates the thin strip at a lower speed. The preliminary winding prevents thin strip from having to enter high-speed finishing stands directly, eliminating the entry difficulty
Solution Approach 2:
The system uses dynamic speed adjustment where the winding reel operates at a lower speed suitable for thin strip handling and entry, while the finishing stands operate at higher speeds to maintain optimal temperature. This dynamic differentiation of speeds allows thin strip to be processed effectively - the winding reel protects the thin strip during entry, and the finishing stands provide the high-speed temperature control needed for quality production
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 allows for the production of high-quality metal strips with uniform mechanical properties across the entire coil length, while reducing the need for oversized electric motors and minimizing temperature losses, thus enhancing plant efficiency and reducing costs.
Implementation Method 1
a rapid heating device, consisting of selectively activatable elements, which is interposed between the at least one roughing stand and the plurality of finishing stands and is configured to heat the intermediate rolled product
Data Source
AI summary
Rolling method to produce a metal strip (P) in coil-to-coil, semi-endless or endless mode, in a rolling plant (10) comprising:a continuous casting device (11) to produce slabs;a furnace (16) configured to maintain the slabs at a certain temperature and/or to heat the slabs;at least one roughing stand (25) to reduce the thickness of the slabs and obtain an intermediate rolled product;a plurality of finishing stands (31) to reduce the thickness of the intermediate rolled product and obtain the strip (P);a rapid heating device (28) interposed between the at least one roughing stand (25) and the plurality of finishing stands (31) to heat the intermediate rolled product in each operating mode, so that the temperature of the strip (P) in correspondence with the outlet of the last finishing stand (31) is comprised between 830° C. and 860° C.