Divided Finishing Train With Rapid Heating for Thin Hot Strip
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Solution Overview
Problem
Conventional Hot Strip Mills face challenges in producing high-quality thin steel strips due to inefficient heating processes, leading to temperature losses and phase changes, which affect product quality and productivity, and are limited in producing strips thinner than 1.2 mm without compromising production speed and flexibility.
Innovation Solution
A new generation Hot Strip Mill plant with a divided finishing train, including a pre-finishing stand and a rapid heating device between the pre-finishing and finishing stands, which heats the strip to maintain temperatures above 830°C, reducing gas consumption and emissions, and incorporating modular induction heating to optimize temperature control and reduce scale formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional gas heating furnaces are used to heat slabs to high temperatures (1250°C), then the strip can maintain austenitic structure and avoid phase transformations, but the heating time becomes very long (4-7 hours) and gas consumption increases significantly
Solution Approach 1:
The patent applies preliminary action by heating the slab to a lower temperature (1100-1150°C) in the gas furnace before rolling, rather than heating to the higher conventional temperature (1250°C). This preliminary heating is sufficient when combined with the rapid heating device during rolling, thereby reducing the initial heating time while achieving the same final temperature maintenance through coordinated heating stages.
2Temperature
If the slab is heated to higher temperatures for particular steels, then the thermal targets are met, but the gas consumption and emissions increase
Solution Approach 1:
The patent uses preliminary heating to 1100-1150°C followed by rapid heating during rolling to achieve the required thermal targets for particular steels. This two-stage approach reduces the need for excessive preliminary heating, thereby lowering gas consumption and emissions while still meeting the thermal requirements for specialized steel grades.
Solution Approach 2:
The patent changes the temperature parameter strategy by reducing the initial heating temperature range and compensating with rapid heating during the rolling process. This parameter change optimizes the balance between achieving thermal targets for particular steels and minimizing energy consumption and environmental impact.
3Adaptability or versatility
If the furnace temperature is increased to differentiate heating for different steel types, then production flexibility is improved, but the delivery times are lengthened due to waiting for correct furnace heating
Solution Approach 1:
The patent applies preliminary heating to a standardized temperature range (1100-1150°C) that is sufficient for most steel types, rather than pre-heating to different high temperatures for each steel grade. The rapid heating device then provides the necessary temperature adjustment during rolling, enabling flexible production of different steel types without waiting for furnace temperature adjustment, thereby reducing delivery times.
4Productivity
If the strip speed is increased in the finishing train, then productivity improves, but the head of the strip rises dangerously due to aerodynamic effects
Solution Approach 1:
The patent applies preliminary heating to maintain the strip at optimal temperature (1100-1150°C) before and during the early rolling passes. This preliminary temperature maintenance allows for higher rolling speeds without compromising strip stability, as the heated strip is more resistant to aerodynamic effects that cause head rise, enabling increased productivity while maintaining reliability.
5Adaptability or versatility
If thin strips (less than 1.2 mm) are produced, then product variety is improved, but the temperature maintenance becomes difficult and quality deteriorates
Solution Approach 1:
The patent applies preliminary heating to maintain the strip at optimal temperature (1100-1150°C) before thin strip rolling. This preliminary heating ensures that even when producing thin strips (0.9-1.2 mm) where temperature maintenance is difficult, the strip starts at a temperature that provides a thermal buffer, allowing sufficient time for the rolling process while maintaining quality and preventing premature cooling that would deteriorate the product.
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 the production of high-quality steel strips with thicknesses as low as 0.9 mm without compromising productivity, reducing gas consumption and emissions, and maintaining uniform mechanical and geometric properties along the coil length, while minimizing production costs and reducing the risk of cobble and stoppages.
Implementation Method 1
a rapid heating device consisting of selectively activatable elements is interposed between the at least one pre-finishing stand and the plurality of finishing stands, so as to heat the pre-finished rolled product
Implementation Method 2
gas heating furnaces configured to heat the slab to a determinate starting temperature
Data Source
Figure 1~2
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AI summary
Plant (10) and method for producing a final strip (P) starting from a slab (50) having a determinate starting thickness, comprising: at least one heating furnace (16) configured to heat at least the slab (50) to a determinate starting temperature; at least one reversible roughing stand (23) configured to subject the slab (50) to one or more rolling passes in order to obtain an intermediate rolled product (51); and a continuous rolling train (25) disposed operatively in line with the roughing stand (23) and configured to reduce the thickness of the intermediate rolled product (51), until the final strip (P) having a determinate final thickness is obtained.