Hot Strip Mill Revamp With Rapid Heating for Thin Strip Rolling
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Solution Overview
Problem
Conventional Hot Strip Mills face challenges in producing thin, high-quality steel strips due to lengthy heating times, high gas consumption, environmental emissions, and limitations in maintaining optimal rolling temperatures, which affect productivity and product quality, especially for thicknesses below 1.2 mm.
Innovation Solution
The method involves revamping the plant by dividing the rolling train into pre-finishing and finishing units, incorporating a rapid heating device between them, and optimizing the heating and descaling processes to maintain optimal temperatures and reduce scale formation, allowing production of thin strips without compromising productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional heating furnaces with gas burners are used to heat slabs to 1200-1250°C, then the strip can reach the required outlet temperature of at least 830°C, but the heating time becomes very long (4-7 hours) and gas consumption becomes very high
Solution Approach 1:
The patent applies preliminary action by pre-heating the slab in the heating furnace to a lower temperature (1000-1100°C) before rolling, rather than heating to the full required temperature. This preliminary heating reduces the thermal mass that needs to be heated during rolling, thereby significantly reducing the overall heating time and gas consumption while still achieving the required outlet temperature of at least 830°C.
2Temperature
If the heating temperature is increased to meet particular steel thermal targets, then the required temperature can be achieved, but gas consumption and environmental emissions increase
Solution Approach 1:
The patent performs preliminary heating to a controlled temperature range of 1000-1100°C, which is sufficient for the rolling process but lower than conventional heating temperatures. This reduces the intensity of heating required, thereby reducing gas consumption and associated environmental emissions while still achieving the necessary outlet temperature of at least 830°C for particular steels.
3Manufacturing precision
If the furnace temperature is raised to differentiate heating for different steel types, then thermal quality can be optimized, but production flexibility is reduced due to the need to wait for furnace re-heating
Solution Approach 1:
The patent applies preliminary heating to bring all slabs to a standardized temperature range of 1000-1100°C before rolling, regardless of steel type. This standardized preliminary heating approach maintains production flexibility by eliminating the need to reheat the furnace for different steel types, while still achieving the required outlet temperature of at least 830°C through optimized rolling conditions.
4Manufacturing precision
If the maximum speed of the strip exiting the finishing train is limited to prevent aerodynamic effects, then strip quality is maintained, but productivity is reduced
Solution Approach 1:
The patent applies preliminary heating to reduce the temperature gradient between the strip and surrounding air during high-speed rolling. By pre-heating the slab to 1000-1100°C before rolling, the strip maintains a more stable temperature even at higher rolling speeds, thereby reducing aerodynamic cooling effects and allowing increased productivity without compromising strip quality.
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 enables the production of high-quality thin steel strips with uniform mechanical and geometric properties, reducing gas consumption and emissions, and maintaining consistent temperatures across the coil length, thereby enhancing productivity and yield.
Implementation Method 1
downstream of the pre-finishing unit there is disposed a rapid heating device configured to heat the pre-finished rolled product to a target temperature
Implementation Method 2
upstream of the pre-finishing unit there is disposed a water descaling device and downstream of the rapid heating device there is disposed a further water descaling device
Data Source
AI summary
A method for revamping a starting rolling plant, for producing a final strip starting from a slab having a determinate starting thickness, including: at least one heating furnace configured to heat at least the slab to a determinate starting temperature; at least one reversible roughing stand configured to subject the slab to one or more rolling passes in order to obtain an intermediate rolled product; and a rolling train disposed operatively in line with the roughing stand, including at least one pre-finishing stand and a plurality of finishing stands and configured to reduce the thickness of the intermediate rolled product, until the final strip having a determinate final thickness is obtained.