Hot Strip Rolling with Rapid Heating for Exit Temperature Control
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Solution Overview
Problem
Existing rolling plants face challenges in maintaining the optimal temperature of metal strips at the outlet of the last finishing stand, particularly in coil-to-coil and semi-endless modes, leading to unwanted phase changes and non-uniform mechanical and geometric properties, while also requiring oversized electric motors and complex speed adjustments.
Innovation Solution
A rolling method and plant design that includes a continuous casting device, selective cutting devices, a rapid heating device, and a management and control unit to maintain the temperature of metal strips between 830 °C and 860 °C, using a constant rolling speed of 12 m/s or less, and adjusting the rapid heating device's activity to achieve optimal temperature without 'speed-up', allowing production in all three modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the rolling mass flow is increased to maintain optimal temperature at the outlet of the last finishing stand, then the temperature control is improved, but the rolling speed must be increased which requires oversized electric motors and increases energy consumption
Solution Approach 1:
The invention applies preliminary heating action by inserting a heating device between the roughing stand and the finishing stands. This heating device pre-heats the strip before it enters the finishing stands, ensuring that the strip reaches the optimal temperature at the outlet of the last finishing stand without requiring excessive rolling mass flow or oversized motors. The heating is applied in advance to compensate for thermal losses during rolling.
Solution Approach 2:
The invention changes the thermal parameter of the strip by actively heating it during the rolling process. By controlling the heating parameters (temperature, heating rate) in the heating device, the strip temperature is maintained within the optimal range (850-950°C) throughout the finishing stands, eliminating the need to increase rolling speed and motor power to achieve temperature control.
2Productivity
If the rolling speed is increased to improve productivity, then the production efficiency is improved, but the temperature of the strip at the outlet of the last finishing stand decreases due to thermal losses
Solution Approach 1:
The heating device performs preliminary heating of the strip before it enters the finishing stands. This advance heating compensates for the thermal losses that occur during high-speed rolling, ensuring that even when rolling speed is increased for higher productivity, the strip maintains the optimal temperature at the outlet of the last finishing stand.
Solution Approach 2:
The heating device operates continuously throughout the rolling process in the finishing stands, providing continuous thermal energy input. This continuous heating action ensures that the strip temperature is maintained at the optimal level throughout the entire rolling process, regardless of the rolling speed, thereby enabling high productivity without temperature loss.
3Temperature
If the rapid heating device power is increased to maintain strip temperature, then the temperature control is improved, but the energy consumption increases
Solution Approach 1:
The heating device parameters (power, heating rate) are optimized to match the actual thermal requirements of the strip during rolling. By controlling the heating parameters precisely, the device provides just enough thermal energy to maintain the optimal temperature without excessive energy consumption. The heating power is adjusted based on the strip thickness, rolling speed, and thermal losses.
Solution Approach 2:
The system uses temperature feedback from thermocouples positioned at various points in the finishing stands to control the heating device power. The measured strip temperature is fed back to the control system, which adjusts the heating power accordingly to maintain the optimal temperature range, minimizing energy consumption while ensuring temperature control.
4Use of energy by moving object
If the rolling mass flow is decreased to reduce energy consumption, then the energy efficiency is improved, but the temperature of the strip at the outlet of the last finishing stand increases beyond optimal levels
Solution Approach 1:
The feedback control system monitors the strip temperature and adjusts the heating device power to maintain the optimal temperature range. When the rolling mass flow is decreased, the feedback system detects the temperature increase and reduces or stops heating to prevent the strip temperature from exceeding the optimal range, thereby maintaining energy efficiency while controlling temperature.
Solution Approach 2:
The heating device power is dynamically adjusted based on the rolling conditions. When the rolling mass flow is low, the heating power is reduced or stopped to prevent overheating. When the rolling mass flow is high, the heating power is increased to compensate for thermal losses. This dynamic adjustment optimizes both energy consumption and temperature control.
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
The solution ensures consistent temperature and quality of metal strips, reduces the need for oversized motors, lowers construction costs, and enhances production efficiency and quality, particularly for thin and ultra-thin strips, while minimizing speed adjustments and energy consumption.
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
Implementation Method 2
Downstream of the finishing stands there is an outlet table, also called run-out table, provided with cooling showers
Data Source
Figure 1
Figure 2~3
Figure 4
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.